K<>l»ort No. AR-H.'iiS
EVALUATION OF DIESEL SMOKE INSPECTION
PROCEDURES AND SMOKEMETERS
by
John O. Storment
Karl J. Springer
FINAL RETORT
Prepared for
Environmental Protection Agency
Air Pollution Control Office
Mobile Souree Pollution Control Program
Division of Emission Control Technology
rv
Contract EHS 70-109
July 1972
SOUTHWEST RESEARCH INSTITUTE
SAN ANTONIO CORPUS CHRISTI HOUSTON
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SOUTHWEST RESEARCH INSTITUTE
Post Office Drawer 28510, 8500 Culebra Road
San Antonio, Texas 78284
EVALUATION OF DIESEL SMOKE INSPECTION
PROCEDURES AND SMOKEMETERS
by
John O. Storment
Karl J. Springer
FINAL REPORT
Prepared for
Environmental Protection Ajjency
Air Pollution Control Office
Mobile Source Pollution Control Program
Division of Emission Control Technology
Contract EHS 70-109
July 1972
Approved:
John M. Clark, Jr., Director
Department of Automotive Research
.
\
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ABSTRACT
Various vehicle smoke test procedures, smokemeters, and smoke
opacity measurement techniques were evaluated by comparison to well-
known standards. The test procedures, which were designed as brief
inspections of smoke from diesel-powered trucks and buses, were compared
to a chassis-dynamometer version of the Federal smoke compliance test.
The performance of six commercial smokemeters was compared to that
of the standard PHS smokemeter. Also, end-of-line and inline opacity
measurements were evaluated by using an inline version of the PHS
smokemeter. This inline instrument was developed and constructed at
Southwest Research Institute as part of this project.
The smoke test procedures investigated showed varying degrees of
correlation with the simulated Federal smoke test, but no one procedure
produced data that correlated with the Federal test in every test instance.
Two commercially-available smokemeters performed well and correlated
with the standard PHS instrument in a number of tests. However, certain
combinations of test procedure and engine type were found for which these
two smokemeters did not correlate well with the PHS unit. The inline
smokemeter developed by SwRI is of the same general design as the
PHS end-of-line smokemeter and uses most of the standard PHS com-
ponents. Inline and end-of-line opacity readings were obtained simul-
taneously during transient and steady-state engine conditions. The data
from these tests showed that the inline and end-of-line instruments
registered similar opacity, although the inline smokemeter read lower
than the end-of-stack in most cases.
Several other aspects of diesel smoke opacity measurement were
also investigated in the course of this project. Two enlarged versions
of the PHS smokemeter were tested and showed good agreement with the
standard unit. Three standard PHS instruments were used in a series of
repetitive smoke tests and exhibited excellent agreement. This latter
series of tests also served as verification of the effectiveness of the
Beere-Lambert law in correcting indicated smoke opacity for small-
diameter exhaust stacks.
11
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TABLE OF CONTENTS
Page
ABSTRACT ii
LIST OF ILLUSTRATIONS v
LIST OF TABLES xi
I. INTRODUCTION 1
II. EVALUATION OF SMOKE TEST PROCEDURES 3
A. Description of Test Instrumentation and Facilities 3
B. Description of Smoke Test Procedures 3
C. Description of Test Vehicles and Engines 9
D. PHS Smokemeter Data for Four Smoke Test 11
Procedures
1. Truck Smoke Tests 11
2. Bus Smoke Tests 17
III. EVALUATION OF THREE COMMERCIAL SMOKEMETERS 23
A. Description of Commercial Smokemeters 23
B. Smokemeter Bench Tests 24
C. Results of Smokemeter Bench Tests 27
1. Static Filter Calibration Test 27
2. Zero Drift 37
3. Effect of Ambient Light 41
4. Effect of Ambient Temperature 45
5. Time Response 50
D. Smoke Tests With Commercial Smokemeters 52
1. Smoke Tests with Stationary-Mounted Engine 52
2. Truck Smoke Tests 61
3. Bus Smoke Tests 68
IV. OTHER TESTS WITH PHS SMOKEMETERS 75
A. Correlation of Three PHS Smokemeters 75
B Correlation of Ten-, Twenty-, and Forty-Inch
PHS Smokemeters 80
111
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TABLE OF CONTENTS (Con't)
Page
V. EVALUATION OF OTHER COMMERCIAL SMOKEMETERS 85
A. Evaluation of Atlantic Research Inline Smokemeter 85
1. Description 85
2. Results of Smokemeter Bench Tests 87
3. Smoke Tests 94
B. Evaluation of Wager Smokemeters 97
VI. DEVELOPMENT OF A PHS INLINE SMOKEMETER AND
COMPARISON OF INLINE AND END-OF-LINE OPACITY
MEASUREMENT 101
A. Design Criteria of the PHS Inline Smokemeter 101
B. Development of the Inline Smokemeter 102
C. Effect of Exhaust Variables on Inline and
End-of-Line Opacity Measurement 113
VII. SUMMARY AND CONCLUSIONS 118
LIST OF REFERENCES 120
APPENDIXES
A. Federal Smoke Test Procedure (Federal Register,
Volume 35, No. 219, November 10, 1970) A-l
B. New Jersey Smoke Test Procedures (New Jersey
Air Pollution Control Code, Chapter 14) B-l
C. Information and Operating Instructions for PHS
End-of-Line and Inline Smokemeters C-l
D. Smoke Trace Evaluation Sheets for Federal Smoke
Tests with PHS End-of-Line and Inline Smokemeters D-l
IV
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LIST OF ILLUSTRATIONS
Figure Page
1 PHS Full-Flow, Light-Extinction Smokemeter 4
2 City Bus Under Test on SwRI Dynamometer
(Inertia Simulation Wheels in Right Foreground) 5
3 Schematic of Federal Smoke Compliance Test 7
4 Schematic of New Jersey Lugdown Smoke Test 8
5 Schematic of New Jersey Acceleration Smoke Test 8
6 Schematic of Experimental SwRI Smoke Test for Trucks 10
7 Schematic of Experimental SwRI Smoke Test for Buses 10
8 PHS Opacity Data for Four Smoke Test Procedures--
Cummins NHC-250 Engine No. 1 14
9 PHS Opacity Data for Four Smoke Test Procedures--
Cummins NHC-250 Engine No. 2 14
10 PHS Opacity Data for Four Smoke Test Procedures--
Cummins NTC-335 Engine 15
11 PHS Opacity Data for Four Smoke Test Procedures--
Caterpillar 1150 Engine 15
12 PHS Opacity Data for Four Smoke Test Procedures--
6V-71 Engine at First Smoke Level 19
13 PHS Opacity Data for Four Smoke Test Procedures--
6V-71 Engine at Second Smoke Level 19
14 PHS Opacity Data for Four Smoke Test Procedures--
6V-71 Engine at Third Smoke Level 20
15 PHS Opacity Data for Four Smoke Test Procedures--
6V-71 Engine at Fourth Smoke Level 20
16 Atlantic Research Opacity Meter 25
17 Bacharach Opacity Meter 25
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LIST OF ILLUSTRATIONS (Con't)
Figure Page
18 Grid Network in Unit of Bacharach Opacity Meter 25
19 Nebetco Opacity Meter — Battery Power Pack
Configuration 25
20 Atlantic Research, Bacharach, and Nebetco Smoke-
meters in Use on a Diesel-Powered Truck-Tractor 26
21 Meter Reading and Error of PHS Smokemeter 29
22 Output Voltage and Linearity Error of PHS Smokemeter 30
23 Meter Reading and Error of Atlantic Research
Smokemeter 32
24 Output Voltage and Linearity Error of Atlantic
Research Smokemeter 33
25 Meter Reading and Error of Bacharach Smokemeter 35
26 Output Voltage and Linearity Error of Bacharach
Smokemeter 36
27 Meter Reading and Error of Nebetco Smokemeter 38
28 Output Voltage and Linearity Error of Nebetco Smoke-
meter 39
29 Angles of Light Incidence 43
30 Instrument Zero Change Asa Function of Ambient
Light Incident Angle 43
31 Instrument Half-Scale Change As a Function of Ambient
Light Incident Angle 44
32 Instrument Zero Change as a Function of Ambient
Temperature 47
33 Instrument Half-Scale Change as a Function of
Ambient Temperature 48
34 Federal "a" and "b" Factors As Measured by
Four Smokemeters 55
vi
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LIST OF ILLUSTRATIONS (Con't)
Figure
35 Test Stand With Four Smokemeters
36 Damaged Grid in Bacharach Smokemeter 61
37 Time-Averaged Smoke Opacity As Measured by PHS,
Atlantic Research, and Bacharach Smokemeters for
Three Test Procedures -- Cummins NHC-250 Engine
No. 1 63
38 Peak Smoke Test Opacity As Measured by PHS,
Atlantic Research, and Bacharach Smokemeters
for Four Test Procedures -- Cummins NHC-250
Engine No. 1 63
39 Time-Averaged Smoke Opacity As Measured by PHS,
Atlantic Research, and Bacharach Smokemeters for
Three Test Procedures -- Cummins NHC-250 Engine
No. 2 64
40 Peak Smoke Opacity As Measured by PHS, Atlantic
Research, and Bacharach Smokemeters for Four
Test Procedures -- Cummins NHC-250 Engine No. 2 64
41 Time-Averaged Smoke Opacity As Measured by PHS,
Atlantic Research, and Bacharach Smokemeters for
Three Test Procedures -- Cummins NTC-335 Engine 65
42 Peak Smoke Opacity As Measured by PHS, Atlantic
Research, and Bacharach Smokemeters for Four Test
Procedures -- Cummins NTC-335 Engine 65
43 Time-Averaged Smoke Opacity As Measured by PHS,
Atlantic Research, and Bacharach Smokemeters for
Three Test Procedures -- Caterpillar 1150 Engine 66
44 Peak Smoke Opacity As Measured by PHS, Atlantic
Research, and Bacharach Smokemeters for Four
Test Procedures -- Caterpillar 1150 Engine 66
45 Time-Averaged Smoke Opacity As Measured by PHS,
Atlantic Research, and Bacharach Smokemeters for
Three Test Procedures -- 6V-71 Engine at First
Smoke Level 70
VII
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LIST OF ILLUSTRATIONS (Con't)
Figure Page
46 Peak Smoke Opacity As Measured by PHS, Atlantic
Research, and Bacharach Smokemeters for Four
Test Procedures -- 6V-71 Engine at First Smoke Level 70
47 Time-Averaged Smoke Opacity As Measured by PHS,
Atlantic Research, and Bacharach Smokemeters for
Three Test Procedures -- 6V-71 Engine at Second
Smoke Level 71
48 Peak Smoke Opacity As Measured by PHS, Atlantic
Research, and Bacharach Smokemeters for Four Test
Procedures -- 6V-71 Engine at Second Smoke Level 71
49 Time-Averaged Smoke Opacity As Measured by PHS,
Atlantic Research, and Bacharach Smokemeters for
Three Test Procedures -- 6V-71 Engine at Third
Smoke Level 72
50 Peak Smoke Opacity As Measured by PHS, Atlantic
Research, and Bacharach Smokemeters for Four Test
Procedures -- 6V-71 Engine at Third Smoke Level 72
51 Time-Averaged Smoke Opacity As Measured by PHS,
Atlantic Research, and Bacharach Smokemeters for
Three Test Procedures -- 6V-71 Engine at Fourth
Smoke Level 73
52 Peak Smoke Opacity As Measured by PHS, Atlantic
Research, and Bacharach Smokemeters for Four Test
Procedures -- 6V-71 Engine at Fourth Smoke Level 73
53 Three PHS Smokemeters on Test Stand 76
54 Effect of Exhaust Stack Diameter on Smoke Opacity--
1600 RPM 79
55 Effect of Exhaust Stack Diameter on Smoke Opacity--
2100 RPM 79
56 Ten-, Twenty-, and Forty-Inch Diameter PHS
Smokemeters on Test Stand 83
57 Atlantic Research Inline Smokemeter (End View) 86
Vlll
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LIST OF ILLUSTRATIONS (Con't)
Figure Page
58 Collimating Tube and Screw-In Optical Module 86
59 Screw-In Collimating Tube and Inline Smokemeter
(Side View) 86
60 Inline Smokemeter and Control-Readout Box 86
61 Meter Reading and Error of Atlantic Research
Inline Smokemeter 89
62 Output Voltage and Linearity Error of Atlantic
Research Inline Smokemeter 90
63 Changes in Zero and Half-Scale Readings Asa
Function of Ambient Temperature 93
64 Atlantic Research Inline Smokemeter in Conjunction
with PHS Smokemeter on Three-In Pipe and Five-In
Pipe 95
65 PHS and A. R. Inline Smoke Opacity Data for Three
Exhaust Pipe Diameters 96
66 Wager Portable Smokemeter and Readout Unit 98
67 Wager Smokemeter Mounted on Exhaust Stack 98
68 Wager Smokemeter Mounted on Exhaust Stack 98
69 Wager Inline Smokemeter 98
70 Wager Inline Smokemeter with Control Box 99
71 Wager Inline Smokemeter Mounted in Exhaust Line 99
72 Wager Inline Smokemeter in Conjunction with
PHS Smokemeter 99
73 Initial PHS Inline Smokemeter Pipe with Mounting
Flange Shown 103
74 Aluminum Inline Smokemeter Pipe--I/2 Inch
Light Beam Hole 103
IX
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LIST OF ILLUSTRATIONS (Con't)
Figure Page
75 Dual Pipe Inline Smokemeter--Side View 103
76 Dual Pipe Inline Smokemeter-End View 105
77 Advanced Design PHS Inline Smokemeter 105
78 Advanced Design PHS Inline Smokemeter 105
79 Air Jets on Inline Smokemeter 105
80 Final Design of the PHS Inline Smokemeter 107
81 Schematic Drawing of Sealed Optical Tube from
PHS Inline Smokemeter 108
82 Opacity Traces for Federal Smoke Test with PHS
Inline and End-of-Line Smokemeters--Cummins
NHC-250 Engine 110
83 Opacity Traces for Federal Smoke Test with PHS
Inline and End-of-Line Smokemeters--Cummins
V-903 Engine 111
84 Opacity Traces for Federal Smoke Test with PHS
Inline and End-of-Line Smokemeters--Mack
ENDT 673B Engine 112
85 Inline and End-of-Line Smokemeters on Test Stand 114
86 Absolute Difference Between PHS Inline and End-
of-Line Opacity Readings Asa Function of Exhaust
Flow Rate 116
87 Absolute Difference Between PHS Inline and End-
of-Line Opacity Readings as a Function of Exhaust
Temperature 116
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LIST OF TABLES
Table Page
1 PHS Smokemeter Data for Four Test Procedures
for Diesel-Powered Trucks 12
2 PHS Smokemeter Data for Four Test Procedures
for Diesel-Powered Buses 18
3 Calibration Data for PHS Smokemeter--End-of-Stack 28
4 Calibration Data for Atlantic Research Model 101
Smokemeter 28
5 Calibration Data for Bacharach Model 73-7004
Smokemeter 34
6 Calibration Data for Nebetco Model NLT-1DE
Smokemeter with Model EM-3 Power Source 34
7 Calibration Data for Nebetco Model NLT-1DE
Smokemeter with Model BM-1 Power Source 40
8 Effect of Ambient Light on Smokemeter Zero
and Half-Scale 42
9 Effect of Ambient Temperature on Smokemeter
Zero, Half-Scale, and Full-Scale Settings 46
10 Smokemeter Response Time (CRC Procedure) 50
11 Smokemeter Response Time (Modified Procedure) 51
12 Federal Smoke Test Data--Smokemeter Evaluation 53
13 Steady-State Smoke Test Data--Smokemeter Evaluation 58
14 Smoke Test Data for PHS, Atlantic Research, and
Bacharach Smokemeters for Four Truck Test
Procedures 62
15 Smoke Test Data for PHS, Atlantic Research, and
Bacharach Smokemeters for Four Bus Test Procedures 69
16 Steady-State Smoke Test Data for Three PHS
Smokemeters 77
XI
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LIST OF TABLES (Con't)
Table Page
17 Smoke Opacity Data Corrected by Beere-Lambert
Law 81
18 Calibration Data for PHS Smokemeter--End-of-Stack 88
19 Calibration Data for Atlantic Research Model 103
Inline Smokemeter 88
20 Effect of Ambient Temperature on Smokemeter
Zero, Half-Scale, and Full-Scale Settings 92
21 Federal Smoke Test Data 94
22 Federal "a" and "b" Factors by Inline and End-
of-Line Opacity Measurement 109
23 Comparison of Inline and End-of-Line Opacity
Readings Under Steady-State Smoke Conditions 115
Xll
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I. INTRODUCTION
In 1966 the original prototype of the U. S. Public Health Service
full-flow, light-extinction smokemeter was sent to Southwest Research
Institute that several copies of the instrument could be made. This
was the first smokemeter designed to measure the density of diesel
smoke by the principle of the human eye, i. e. , light obscuration by
the smoke itself. Early tests at SwRI using the PHS instrument marked
the beginning of a long-range Environmental Protection Agency (EPA)
study* ''" involving diesel-powered trucks and buses, chassis dyna-
mometers, and test procedures. One of the principal objectives of this
study was to measure and characterize the smoke emissions of diesel
engines under both transient and steady-state operation. The PHS
smokemeter was used almost exclusively in this study. In the years
since its inception, the PHS instrument has been improved' ' ', but
the basic concept has remained unchanged.
In 1968, the Federal Government established standards for
smoke output from 1970 and later model diesel engines used in vehicles
above 6,000 Ibs. GVW*''. Compliance with these standards was (and
is) certified by subjecting a typical production engine, representative
of a certain class or family of engines, to the Federal smoke com-
pliance tesc '» °). The PHS smokemeter is specified for use in all
compliance tests. Hence, the Federal smoke test procedure and the
PHS smokemeter have become standards in the measurement of smoke
opacity from automotive-type diesel engines.
Concurrent with these efforts by the Federal Government to
control smoke from new engines, various states and localities in-
stituted inspection programs designed to limit smoke output from in-
use vehicles. Many of these inspection programs, such as that of
the State of California''', rely on the use of Ringelman smoke rating
charts by trained observers. The State of New Jersey has recently
enacted legislation requiring periodic smoke inspections of all diesel-
powered trucks and buses operated on public roads' ®>. The New
Jersey law established a test procedure that recognizes the inherent
limitations of the visual (Ringelman) method of rating diesel smoke
and requires the use of a light-extinction smokemeter for the inspection.
To meet the instrumentation requirements of present and future
inspection programs, various companies have developed smoke-
meters designed for this particular application. Such instruments
are usually portable, have their own internal power supply, and can
be operated by one person. Hence, they are not laboratory research
instruments, as is the PHS instrument, but rather are designed for use
in situations where use of the PHS smokemeter would be impractical.
'^Superscript numbers in parentheses refer to the List of References at
the end of this report
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Smoke test procedures have also received considerable attention
as a result of current or anticipated inspection programs. Such test
procedures must be performed in the field, either on the road or on
a chassis dynamometer, and should result in smoke measurements
typical of vehicle operation. Hence, these test procedures are not
necessarily similar to the Federal smoke compliance test, but, like
the inspection-type commercial smoke-meters, are designed for a
particular application.
The preceding paragraphs present a brief outline of the evolution
and present state of diesel smoke control programs, particularly at
the Federal and state levels. The project that is the subject of this
report was designed to obtain information on some of the pertinent
test procedures and commercial smokemeters now in existence and
compare them to the accepted standards, the Federal smoke compliance
test and the PHS smokemeter. A more general project objective was
to gather information on selected aspects of smoke opacity measure-
ment, such as end-of-line and in-the-line sampling methods. Several
of these selected topics were investigated at the request of the Project
Officer, after consultation with members of the Emissions Research
Laboratory staff.
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II. EVALUATION OF SMOKE TEST PROCEDURES
The Emissions Research Laboratory has successfully developed
a chassis -dynamometer version of the Federal smoke test that correlates
well with the engine dynamometer test procedure (Appendix A). This
simulated Federal test has, in fact, been the basis for a two-year surveil-
lance study for EPA of smoke from a variety of diesel-powered vehicles
(Contract EHS 70-109, "Surveillance Study of Smoke From Heavy-Duty
Diesel-Powered Vehicles -- Southwestern U. S. A. "J
In 1971, the State of New Jersey began enforcing limits on
visible smoke from diesel-powered vehicles operated on its public roads.
Several inspection smoke test procedures were investigated by New
Jersey officials, including a free acceleration test, a lugdown procedure
for trucks, and an acceleration smoke test for buses. The latter two
procedures, contained in Appendix B, are currently in use in the New
Jersey inspection program.
This phase of the project sought to establish the degree of
correlation between these three test procedures and the simulated
Federal test. Also, an experimental smoke test was developed by
the Emissions Research Laboratory and included in this evaluation
study.
A . Description of Test Instrumentation and Facilities
The U. S. Public Health Service full-flow, light- extinction
smokemeter (Figure 1) was used to measure exhaust smoke opacity
during all test procedures. Smokemeter output arri engine speed were
recorded on a Texas Instruments or Hewlett Packard dual-pen recorder
with 10-mv range and 0. 4 sec full-scale response. Recorder chart
speed was 12 in per minute, which permitted accurate analysis of the
opacity traces. The vehicles used in this evaluation were operated
on a Clayton chassis dynamometer with tandem-axle power absorp-
tion capability. This unit can absorb 200 hp per axle, while simulating
up to 41, 000 pounds of vehicle weight by means of inertia wheels
attached to the dynamometer rolls. Figure 2 shows a bus under test
on this dynamometer.
B. Description of Smoke Test Procedures
The smoke test procedures used in this study included the chassis
dynamometer simulation of the Federal smoke compliance test, the
New Jersey lug-down test for trucks, the New Jersey acceleration
test for buses, an experimental smoke test developed by the Emissions
Research Laboratory, and a free acceleration test formerly proposed
as the New Jersey test for trucks. These various procedures will
now be described in detail.
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FIGURE 1. PHS FULL-FLOW, LIGHT-EXTINCTION SMOKEMETER
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\
FIGURE 2. CITY BUS UNDER TEST ON SwRI DYNAMOMETER (INERTIA
SIMULATION WHEELS IN RIGHT FOREGROUND)
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The Federal smoke compliance test, as performed on engine
or chassis dynamometer, consists of an initial engine acceleration
from 150-250 rpm above idle speed to 85-90% of rated engine speed
in 5. 0± 1. 5 seconds, a second acceleration from peak torque speed
(or 60% of rated speed, whichever is higher) to 95-100% of rated speed
in 10. 0±2. 0 seconds, and (following this second acceleration) a full-
power lugdown from 95-100% of rated speed to the particular inter-
mediate engine speed (peak torque speed or 60% of rated speed) in
35. Oi 5 seconds. The accelerations are made against simulated vehicle
inertia furnished by large flywheels connected to the dynamometer
rolls or shaft, and/or against a preset load in the power absorption
unit. A schematic drawing of engine speed vs time is illustrated in
Figure 3. Three of these sequences constitute one smoke test.
The average smoke opacity from the 15 highest - valued one-
half second intervals of the two accelerations determine the "a" factor,
and the average opacity from the five highest - valued one-half second
intervals determines the "b" factor. The maximum values currently
allowed for "a" and "b" factors of certification engines are 40- and
20- percent opacity, respectively.
The New Jersey lugdown smoke test for trucks can be conducted
on a chassis dynamometer or on the road. In the latter procedure,
the full-power lugdown of the engine is accomplished by applying the
vehicle brakes. The chassis dynamometer test, which was used in
this evaluation, consists first of operating the engine at maximum
governed engine speed, under no load, in a transmission gear that
gives a vehicle speed of 45-60 mph. (Note that the engine speed involved
is the maximum allowed by the governor, and is usually 100-250 rpm
over the rated engine speed designated in the manufacturer's sales and
service literature. ) Power absorption (load) is applied until the engine
speed is reduced to 80% of maximum governed rpm. This reduced
engine speed is held constant for 5-10 seconds, and the peak smoke
opacity measured during this time is the opacity value for the test.
The maximum peak opacity allowed under current New Jersey law is
20 percent. Figure 4 is a schematic drawing of engine speed vs time
for this procedure.
The New Jersey acceleration smoke test for buses is conducted
on the road and involves a full-throttle acceleration from rest to a
vehicle speed of 20 mph. The peak smoke opacity generated during this
acceleration period (approximately 8-12 seconds) is the test opacity.
A peak of 40 percent opacity is the maximum allowed under current
New Jersey law. A schematic drawing of vehicle speed vs time for
this procedure is shown in Figure 5.
The experimental smoke test developed by the Emissions
Research Laboratory is a chassis dynamometer procedure. The
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90
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Lugdov/n
First
Acceleration
TIME, SEC
FIGURE 3. SCHEMATIC OF FEDERAL SMOKE COMPLIANCE TEST - ENGINE SPEED VS TIME
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engine in the test vehicle is first operated at rated speed and maximum
power output, and a transmission gear is selected that produces a rear
wheel speed of 45-65 mph. The engine is then brought back to low idle
speed and the rear wheels brought to rest. The dynamometer load
used to obtain the maximum power condition is left in the water brake
power absorption unit. The smoke test itself consists of engaging the
vehicle's clutch in a smooth and steady manner, then accelerating with
full throttle. (Buses with two-speed automatic transmissions are ac-
celerated at full throttle and the transmission upshift allowed to occur
as in normal operation. ) Engine speed increases quite rapidly at first,
due to the absence of any inertia simulation flywheels on the dynamometer
rolls. However, as engine speed (and, hence, rear wheel speed)
increases, the load stored in the water brake unit becomes effective,
and engine speed increases at a slower rate. Approximately five
to ten seconds after the start of the accelerations, engine rpm reaches
rated speed, the maximum attainable with the preset load in the dyna-
mometer. This maximum power condition at rated engine speed is
maintained for approximately 10 seconds. Schematic drawings of
engine speed vs time for this procedure for trucks and buses are
shown in Figures 6 and 7, respectively.
The smoke opacity trace produced during the acceleration and
the maximum power condition is analyzed to obtain both peak and
average opacity. This latter quantity is obtained by averaging the smoke
opacity in the five highest - valued one-half second intervals.
The free acceleration test is performed with the vehicle at
rest and the transmission in neutral. The engine undergoes a full-
throttle acceleration from 1000-1200 rpm to maximum governed engine
speed. As soon as this maximum speed is reached, the throttle is
partially closed and engine speed allowed to drop back to the 1000-
1200 rpm range. The engine is again accelerated to maximum speed.
This test cycle is repeated several times, until three or four repeat-
able peak opacity readings are obtained. Only peak opacity is of interest,
since the acceleration time is very short (usually one second or less)
and time-averaged opacity is therefore less informative than when the
acceleration is of longer duration.
C. Description of Test Vehicles and Engines
The makes and models of engines used in this study were selected
to fulfill several criteria imposed by the evaluation procedure. For
the evaluation of smoke tests of dies el-powered trucks, engines were
selected which provided a wide range of smoke opacities and exhaust
flow rates. Additional consideration was given to the operating charac-
teristics of the engines, such as whether their highest smoke opacity
occurred during acceleration or lugdown, and if the acceleration smoke
peaks were of long or short duration.
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Upshift
Test Period
Idle
15-20 sec.
Time, Sec.
FIGURE 7. SCHEMATIC OF EXPERIMENTAL SwRI SMOKE
TEST FOR BUSES - ENGINE SPEED VS TIME
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11,
The Cummins NHC-250 and NTC-335 engines used in these
tests were installed in intercity truck-tractors equipped with tandem-
drive rear axles and single four-in diameter exhaust stacks. The two
naturally aspirated NHC-250 engines originally had approximately the
same smoke opacity; however, for test purposes one engine had its
smoke level increased substantially by the insertion of a restrictor
plate in the intake manifold. The turbocharged NTC-335 engine had high
peak opacity during acceleration from idle and very low smoke during
high-power constant speed (or slow lugdown) conditions. The Cater-
pillar 1150 engine was installed in a single-axle truck-tractor used
in intracity service. This naturally aspirated engine had very high,
very brief smoke peaks during acceleration from idle, and lugdown
smoke similar to an NHC-250 engine. The Caterpillar 1150 thus
had smoke output typical of both naturally aspirated and turbocharged
engines.
For the evaluation of tests for diesel-powered buses, the only
engine available was the Detroit Diesel 6V-71 two-cycle engine common
to most municipal buses. Since these engines all have approximately
the same fuel and air consumption rates, the only variable of signi-
ficance was the smoke opacity. Hence, it was decided to use one bus
for all tests and to vary the smoke opacity by means of a series of
plate orifices installed in the engine's air intake system. This approach,
which was approved by the Project Officer, proved to be very effective.
Any desired smoke level could be obtained with the proper plate orifice,
and the smoke opacity was highly repeatable from one test to another.
The nominal smoke levels used in this evaluation were approximately
6.0, 13.0, 22.0, and 36. 5- percent opacity.
D. PHS Smokemeter Data for Four Smoke Test Procedures
The data contained in this section are results from all smoke
tests performed with the five test vehicles (four truck-tractors and
one bus) and are the average of at least six repeatable tests with each
test procedure, with each vehicle. In the case of the city bus, the
various tests were performed at least six times at each of the four
smoke levels. The data for the truck smoke tests are presented sepa-
rately from those for the bus smoke tests.
1. Truck Smoke Tests
Table 1 contains the data for the smoke tests involving the four
truck-tractors. The time-averaged data for the accelerations and lug-
downs (or other full-power conditions) are given as "a" and "b" factors,
respectively. These terms are generally used to denote the time-
averaged data for the Federal smoke test, and are used here in an
-------
12.
TABLE 10 PHS SMOKEMETER DATA FOR FOUR TEST PROCEDURES
FOR DIESEL-POWERED TRUCKS
Federal (Chassis Dyna. )
PHS Smoke
Engine
Cummins NHC -250 (No. 1)
Cummins NHC-250 (No. 2)
Cummins NTC-335
Caterpillar 1150
"a"
Accel.
Factor* Peak
13.5
35. 1
10.2
27.2
24.2
38.8
38. 8
97. 1
Opacity, %
"b"
Lug
Factor* Peak
12.2
38.0
2.6
24. 9
16. 1
40.4
3.0
27. 4
New Jersey Truck Lugdown
PHS
"a"
Factor*
9.6
18.0
42. 2
22.0
Smoke Opacity, %
Accel.
Peak
20.8
29. 1
64.0
79. 4
"b"
Factor*
8.8
31.4
2.2
12.6
Lug
Peak
10.8
32.4
2.8
17.9
SwRI Accel. -Max. Power
PHS
Engine
Cummins NHC-250
Cummins NHC-250
Cummins NTC-335
Caterpillar 1150
"a"
Smoke Opacity, %
Accel.
Factor*
(No.
(No.
1)
2)
14.
20.
37.
26.
2
6
6
8
Peak
18.
29.
50.
89.
4
8
6
3
"b"
Factor*
14.
27.
2.
15.
5
0
4
4
Max.
Power
Peak
16.
27.
3.
18.
3
9
0
2
New Jersey Free Accel.
PHS Smoke Opacity, %
Accel.
Peak
15.9
29.6
59.6
23.2
* Time-Averaged Data
-------
13.
analogous manner for the other test procedures. The "peak" data are
the instantaneous peak opacity values obtained during the accelerations
and lugdown (or other full-power conditions) of the various test pro-
cedures.
There are two general comparisons made with the data in
Table 1. First, the time-averaged "a" and "b" factors for a particular
test procedure are compared to the corresponding peak values for the
same procedure. However, the principle comparison is between the
data for the simulated Federal smoke test and those for the other three
test procedures. These comparisons, especially the latter, are quite
involved; therefore, the data is illustrated (Figures 8, 9, 10 and 11)
in an attempt to facilitate the various comparisons. Some remarks
concerning the general trends demonstrated by the data will be made,
but the reader will find frequent references to the aforementioned
figures, and Table 1, helpful.
a. Comparison of Average and Peak Opacity Data
As one would expect, the peak opacities were in every instance
higher than the time-averaged opacities. The magnitude of the differences
between the peak and time-averaged data was greatest for the acceleration
smoke opacities of the Cummins NTC-335 and Caterpillar 1150 engines,
since they have high peak smoke during acceleration from idle. In
the case of the two Cummins NHC-250 engines, the greatest difference
between peak and average acceleration opacities occurred for Engine
No. 1, the "low smoke" engine. This was due to the fact that the "high
smoke" engine (No. 2) had acceleration smoke traces with a broad,
almost square-wave form, while the low smoke engine had a definite
peak to its smoke trace. Thus, the peak acceleration opacity for the
high smoke engine was closer to its time-averaged "a" factor than was
the case for the low smoke engine.
The greatest difference between the time-averaged "b" factors
and their corresponding peak values occurred for the Caterpillar 1150
engine, and was least for the Cummins NTC-335 engine. The Caterpillar
engine has a large variance on either side of its average lugdown opacity
value. Such a variance appears as "hash" on the smoke opacity trace.
The turbocharged NTC-335 engine produces very smooth opacity traces,
with little "hash". This is because the turbocharger damps out most of
the pulsations in the exhaust flow. The difference between average and
peak lugdown opacity for the NHC-250 engines falls between the two
extremes mentioned above. However, the high smoke engine showed
slightly better agreement than its low smoke counterpart.
These general observations hold for the three test procedures
that have both average and peak opacity data. The free acceleration
test data involves only peak opacity values.
-------
14.
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TEST PROCEDURES - CUMMINS NHC - 250 ENGINE
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TEST PROCEDURES - CUMMINS NHC - 250 ENGINE
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-------
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-------
16.
b. Comparison of Federal Smoke Test with Other Test
Procedures
The "a" factors for the New Jersey lugdown test are substantially
lower than those for the simulated Federal Test, except in the case of
the turbocharged NTC-335 engine, where the reverse is true. The same
trends were found in the peak acceleration opacities for these two pro-
cedures. The acceleration in the New Jersey test is very fast, being
accomplished without inertia simulation or dynamometer load. This
rapid acceleration caused the turbocharged engine to develop significantly
higher peak opacity than the slower acceleration against inertia of the
Federal smoke test. Hence the higher "a" factor in the New Jersey test.
Similarly, the lugdown smoke opacities, both time-averaged
and peak, for the New Jersey test are, in general, significantly lower
than those of the Federal test. The turbocharged engine produced
very similar opacity readings with each procedure, while the Caterpillar
1150 engine showed the worst correlation. The reason for this dis-
crepancy is that the turbocharged engine produced low smoke at almost
any full-power condition, regardless of engine speed. On the other
hand, the naturally aspirated 1150 engine produced its highest smoke
opacity below 2000 engine rpm. The minimum speed this engine en-
counters in the Federal and New Jersey test procedures is 1800 and
2400 rpm, respectively. Hence, lugdown smoke was much higher in the
Federal test. The NHC-250 engines generate their highest lugdown
smoke at approximately 1800-2000 rpm, and this speed range is covered
in the Federal test. However, the New Jersey procedure is run at
1840 engine rpm, where smoke opacity is somewhat less.
factors for the SwRI test cycle show varying degrees of
factors. The best agree-
ment exists for the low smoke (No. 1) Cummins NHC-250 engine and the
Caterpillar 1150 engine. The SwRI "a" factor generated by the high
smoke (No. 2) NHC-250 is much lower, and that of the turbocharged
NTC-335 engine much higher, than the corresponding "a" factors for
the simulated Federal test. The peak acceleration opacities for the
SwRI test were moderately (6- to 9- percent opacity) lower than the
corresponding peak data for the Federal test cycle, except for the turbo-
charged NTC-335 engine, where the reverse situation occurs. The
typical acceleration in the SwRI test requires a time span somewhere
between those required for the Federal and New Jersey procedures,
and the acceleration smoke opacity, both peak and time-averaged, for
the turbocharged engine appears to increase as the duration of the
acceleration decreases.
The SwRI "b" factors and peak opacities for the low smoke
(No. 1) NHC-250 and NTC-335 engines are close to those for the Federal
test. However, the high smoke (No. 2) NHC-250 and Caterpillar 1150
-------
17.
engines show very poor correlation between the two test procedures.
All three of the Cummins engines are operated at 2100 rpm in the
SwRI test, while the Caterpillar engine is tested at 3000 rpm In view
of what was said previously concerning the speeds at which these engines
produce their maximum steady-state smoke opacity, it is not surprising
that the Caterpillar engine shows such poor correlation between these
two procedures. Conversely, one would expect that the NHC-250 en-
gines would show good correlation, since they are operated near the
speed where their maximum smoke opacity occurs. It is not known
why the high smoke NHC-250 did not have better correlation between
the two types of tests.
The peak opacities for the free acceleration tests do not correlate
well with the acceleration peaks of the Federal smoke test. However,
the free acceleration peaks are surprisingly close (2.5- to 5.5- percent
opacity) to the "a" factors for the naturally aspirated engines in the
Federal procedure. The turbocharged NTC-335 engine produces a free
acceleration peak approximately six times the value of the time-
averaged Federal "a" factor.
In summary, the SwRI smoke test shows good "a" factor correlation
with the Federal test for two naturally aspirated engines used in the
evaluation. The time-averaged acceleration opacity from the New Jersey
lugdown test does not adequately reproduce the Federal "a" factors for
any of the engines. The free acceleration has some correlation with
the Federal "a" factors for the naturally aspirated engines, but would
appear to have serious problems with smoke from turbocharged engines.
Both the New Jersey lugdown and SwRI tests are capable of reproducing
the Federal "b" factor for the turbocharged engine, but not for the
naturally aspirated engines. Thus, no one procedure correlates with
the simulated Federal smoke test in every instance.
2. Bus Smoke Tests
The data from the smoke tests performed by the municipal bus
are presented in Table 2. Again, the "a" and "b" factors are time-
averaged opacities for accelerations and lugdowns, respectively, while
the "peak" data are instantaneous opacity values. As in the case of the
truck test data, there are two comparisons of interest. First, time-
averaged opacities ("a" and "b" factors) for a test procedure are com-
pared to the corresponding peak opacities for the same procedure.
The second and more important comparison is between the Federal
smoke test data and the data for the other procedures. These comparisons
are represented graphically in Figures 12, 13, 14 and 15.
-------
18.
TABLE 2. PHS SMOKEMETER DATA FOR FOUR TEST
PROCEDURES FOR DIESEL-POWERED BUSES
Engine
Detroit Diesel 6V-71E
Detroit Diesel 6V-71E
Detroit Diesel 6V-71E
Detroit Diesel 6V-71E
Federal (Chassis Dyna. )
PHS Smoke Opacity, %
"a" Accel.
Factor* Peak
5.2
13,Z
21,9
37.6
"b"
Factor*
7.2 5.6
15.6 12.8
25.0 21.7
43.4 36.4
Lug
Peak
6.0
14.2
22.8
38.7
New Jersey Bus Accel.
PHS Smoke Opacity, %
"a" Accel.
Factor* Peak
3.5
8.0
14.2
20.0
4.4
10.4
18.2
25.1
Engine
SwRI Accel. - Max. Power
PHS Smoke Opacity, %
"a" Accel. "b" Max. Power
Factor* Peak Factor* Peak
Detroit
Detroit
Detroit
Detroit
Diesel
Diesel
Diesel
Diesel
6V-71E
6V-71E
6V-71E
6V-71E
4.
10.
19.
28.
1
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5
6
4.
14.
24.
34.
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5
4.
13.
24.
38.
4
6
2
9
4.
14.
25.
41.
9
6
6
2
New Jersey Free Accel.
PHS Smoke Opacity. %
Accel.
Peak
4.6
17.0
34.5
47.8
*Time Averaged Data
-------
19.
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FIGURE 13.
PHS OPACITY DATA FOR FOUR SMOKE TEST PROCEDURES
6V-71 ENGINE AT SECOND SMOKE LEVEL
-------
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-------
21.
a. Comparison of Average and Peak Opacity Data
As in the case of the truck smoke test data, the peak opacities
of both accelerations and lugdown were higher than the corresponding
average opacities, and the difference between peak and average opacity
tended to increase as the smoke level increases. This trend is most
evident for the acceleration smoke opacity data and is consistent for the
Federal, New Jersey, and SwRI tests. There is very little "hash" in
the smoke opacity trace of a two-cycle engine. Hence, the differences
between the time-averaged and peak opacities are not so dependent
on the variance in the opacity trace as in the case of the smoke tests
with the four-cycle truck engines.
The simulated Federal test produced acceleration smoke peaks
some 2. 0- to 6. 0- percent opacity higher than the average value of the
acceleration smoke. The peak opacities during lugdown were generally
within 1.0- or 2.0- percent opacity of the time-averaged opacities for
this part of the test procedure. The peak opacity values for the New
Jersey acceleration test were 1.0- to 5.0- percent opacity greater
than the time-averaged values. No lugdown data are produced by the
New Jersey test. The experimental SwRI smoke test had acceleration
smoke peaks approximately 0. 3- to 6. 0- percent opacity higher than the
corresponding "a" factors, while the steady-state maximum power smoke
had peaks some 0.5- to 2. 5- percent opacity higher than the time-
averaged opacities.
b. Comparison of Federal Smoke Test With Other
Procedures
The New Jersey smoke test for buses produced substantially
lower opacities, both peak and average, than the simulated Federal
test. Also, this difference increased as the nominal smoke level in-
creased. In actual practice the New Jersey inspection program is
concerned only with the peak acceleration opacity produced by the
test. Hence, it is interesting to compare the peak opacity with the
time-averaged Federal "a" factors. The peak New Jersey data are
consistently lower than the corresponding Federal "a" factors, in
spite of the fact that the Federal "a" factors are partially determined
by the usually lower opacity values from the second acceleration in
that procedure. Other factors that contribute to the differences in
opacity between these two procedures are the longer duration of the
New Jersey acceleration (almost twice as long as the initial accelera-
tion of the Federal test) and the lower engine speed attained during the
New Jersey test (1600 rpm N2 1800 rpm for the first acceleration of
the Federal test). Slower acceleration rates in particular appear to
be the reason for lower smoke opacity than would otherwise be produced.
-------
22.
The experimental SwRI smoke test produced peak and time-
averaged acceleration opacities at the first three smoke levels that
were slightly lower than the corresponding opacities from the Federal
smoke test. Only at the highest smoke level (a nominal 36.5- percent
opacity) was there a large deviation for the two sets of data. The
average and peak opacities for the lugging (or maximum power) part
of the SwRI cycle were close to (and slightly higher than) the
lugdown opacities of the Federal test procedure, even at the highest
smoke level. This agreement between the data for the two procedures
is the result of the fast acceleration time (approximately 2. 0 seconds)
and lugdown at rated speed in the SwRI test. These conditions are closer
to those in the Federal test than are the conditions of the New Jersey
procedure; hence, correlation with the Federal test is better.
The free acceleration test produced peak opacities that were,
in general, substantially higher than the "a" factors of the Federal
smoke test. The greatest difference again occurred at the higher smoke
levels. The correlation between the free acceleration peak opacities
and the acceleration peaks of the Feceral test was inconsistent, in
some cases being fairly close and in others being very poor.
Overall, the results of the experimental SwRI smoke test pro-
cedure showed the best agreement with the Federal test data, parti-
cularly for smoke levels below, say, 25- percent opacity. The "a"
factors of the New Jersey test correlate very badly with the Federal
"a" factors. However, a certain degree of correlation does exist
between the peak opacities of the New Jersey test and the Federal "a"
factors, but only for opacity levels under about 20 percent. This same
conclusion also applies to the free acceleration peak opacities. There-
for, in summary, none of the test procedures correlated with the
simulated Federal test in all cases.
-------
23.
III. EVALUATION OF THREE COMMERCIAL SMOKEMETERS
The recent emphasis on state inspection programs for diesel-
powered vehicles has caused several companies to develop opacity
measurement devices for this application. In particular, the New
Jersey Department of Environmental Protection requested that inter-
ested companies submit designs for a smokemeter to be used in that
state's inspection program. Three companies which offered their
smokemeters for consideration by New Jersey officials were Atlantic
Research Corporation, Bacharach Instrument Company and Nebetco
Engineering. The Atlantic Research instrument was eventually selec-
ted by New Jersey for use in the program.
However, the potential market for these inspection-type
smokemeters is still quite large, with other state and local enforce-
ment agencies, fleet owners, municipal transit (bus) concerns, and
even diesel repair shops all potential buyers of this type of instrument.
Hence, there exists a need for a performance evaluation of these smoke-
meters, particularly in comparison with the PHS instrument. The
Atlantic Research, Bacharach, and Nebetco smokemeters were the
instruments included in this evaluation, and their performance charac-
teristics were defined in a broad series of tests.
A . Description of Commercial Smokemeters
The Atlantic Research instrument (Figure 16) is a portable,
battery-powered unit designed to meet specifications of the State of
New Jersey. The instrument consists of a sensor unit containing the
light source and optical detector, and a hand-held readout unit con-
taining operating controls, meter, electrical circuitry, and power
supply. The two units are connected by a signal cable. The light source
is a solid-state device operating at a frequency of 1000 Hz. The op-
tical detector is a solid-state photodiode. Electrical circuitry is also
solid-state, and utilizes integrated circuits and printed wiring. The
batteries are of the permanent rechargeable type and can be recharged
by plugging the readout unit into a 120-volt AC outlet overnight.
Operating controls in the hand unit are an on-off switch, "zero" and
"full-scale" adjustments, and a button that gives the user a choice of
either continuous or peak opacity readings. The smokemeter may be
ordered with an external output jack that supplies a nominal 100-milli-
volt signal to a strip chart recorder.
The Bacharach smokemeter (Figure 17) is also a portable,
battery-powered unit designed to New Jersey specifications. The
instrument consists of a sensor unit containing the light source and
optical detector, and a readout box containing operating controls,
meter, electronic circuitry, and power supply. The light source is
a GE No. 502 incandescent bulb, while the optical detector is a cad-
mium sulfide photocell. Batteries can be recharged by plugging them
-------
24.
into a 120-volt AC outlet for 12 to 16 hours. Operating controls in
the readout unit include an on-off switch, "zero" and "full-scale"
adjustments, battery voltage indicator, and a switch that allows the
peak opacity reading to be retained. The normal operating mode of
the instrument gives continuous opacity readings. The smokemeter
is equippped with an external output jack that supplies up to 377 milli-
volts to a recorder. An interesting feature of the Bacharach instrument
is the grid network in the sensor head (Figure 18). The purpose of
this "eggcrate" is to straighten the exhaust plume and create a pressure
drop that is supposed to sweep air over the optical lens system.
The Nebetco smokemeter (Figure 19) was also designed to
meet New Jersey specifications. The instrument can be used with
either a rechargeable battery power source or 120-volt AC power.
There is a separate readout box for each power source, with the battery-
powered configuration being the most portable. Both readout boxes have
an alarm that sounds when a predetermined opacity level is exceeded,
as well as the usual on-off switch, "zero" and "full-scale" adjustments,
and meter. The 120-volt readout box will supply 64 millivolts externally
for a recorder. The design point where the Nebetco smokemeter
differs most from the Atlantic Research and Bacharach instruments
is in the optical system. The Nebetco system has the light source and
photocell in a single housing on one side of the sensor unit, or "cage",
and a focusing lens and reflector on the other side. The light beam
passes throug a semi-transparent mirror and is focused by the lens
onto the reflector, which reflects the light back through the lens to
the mirror. The light beam is reflected off the mirror and onto the
photocell. Calibration of the instrument is accomplished by placing
apertures of various diameters in the light beam, thus re.ducing the amount
of light reaching the photocell. The calibration opacity is proportional
to the area of the aperture. A complete set of apertures, for 0- to 90-
percent opacity in ten-percent opacity increments, was included with the
smokemeter.
The three smokemeters are shown in Figure 20 as they might
be used to perform a brief inspection smoke test on a diesel-powered
truck-tractor.
B. Smokemeter Bench Tests
Each smokemeter, including the PHS instrument, was subjected
to a series of bench tests. These tests, which were approved in ad-
vance by the Project Officer, were taken principally from the Coordinating
Research Council report, "Recommended Evaluation Procedure for
Full-Flow, Light-Extinction Smokemeters. " The following is a brief
summary of the tests selected and their objective.
-------
FIGURE 16. ATLANTIC RESEARCH
OPACITY METER
FIGURE 18. GRID NETWORK IN
UNIT OF BACHARACH OPACITY
METER
25
FIGURE 17.
BACHARACH OPACITY
METER
FIGURE 19. NEBETCO OPACITY
METER BATTERY POWER
PACK CONFIGURATION
-------
26.
FIGURE 20. ATLANTIC RESEARCH (TOP), BACHARACH (MIDDLE), AND
NEBETCO (BOTTOM) SMOKEMETERS IN USE ON A DIESEL-POWERED
TRUCK-TRACTOR
-------
27.
(1) Determine the accuracy and linearity of the smokemeter
using a set of neutral density filters. For this test, seven fil-
ters ranging from 15. 5- to 86. 0- percent opacity were selected
These filters have been calibrated and their values established
to a high degree of accuracy.
(2) Determine the zero drift of the smokemeter over a one-
hour period.
(3) Determine the sensitivity of the smokemeter to ambient
light. A 125-watt spotlight was directed into the photocell
and light source openings from different angles. Also, a white
reflecting surface was used to reflect the light into the photo-
cell. This simulates a plume of white smoke passing through
the smokemeter.
(4) Determine the sensitivity of the smokemeter to ambient
temperatures. Each smokemeter was placed in a temperature
chamber and soaked at 75, 100, 125, and 150 degrees F. The
change in the smokemeter's zero, half-scale, and full-scale
settings was measured at each temperature.
(5) Determine the time response of the smokemeter to a rapid
change in opacity. Both the CRC procedure and an alternate
procedure were used, as questions were raised concerning
the efficacy of the CRC procedure.
C. Results of Smokemeter Bench Tests
1 . Static Filter Calibration Test - The results of the filter
calibration of the PHS smokemeter are given in Table 3. Instrument
meter error was quite low, with deviation from the filter value being
one-percent opacity, or less. Meter error tended to the high (or plus)
side. Figure 21 shows the meter reading and error plotted versus
filter value. The smokemeter output at zero and 100- percent opacity
was 10 millivolts and zero millivolts, respectively. The theoretical
linear output was calculated from these two end points. The observed
output, which was measured on a digital voltmeter, agreed closely
with the theoretical output. Hence the linearity error, which expresses
the difference between observed and theoretical outputs as a percentage
of the total net output, was very low. Note that a meter error on the
high (or plus) side yields a linearity error on the low (or minus) side,
and vice versa. Figure 22 shows the output voltage and linearity error
as functions of filter opacity. The equations for the meter error,
theoretical linear millivolts, and linearity error appear at the bottom
of Table 7.
-------
28.
TABLE 3, CALIBRATION DATA FOR PHS SMOKEMETER END-OF STACK
OF
Filter Value.
% Opacity
0
100
15.5
22.5
37. 5
49. 5
61.0
73.0
86.0
Opaque
Clear
OM
Meter Value.
% Opacity
0*
100*
15.3
23.0
38.3
50. 0
62.0
74. 0
86.4
100.0
0
EM
Meter Error,
% Opacity
0
0
-0.2
+0. 5
+0.8
+0.5
+ 1.0
+ 1.0
+0.4
0
0
VM
Observed
Millivolts
10. 0 (=Vc)
0 (=Vo)
8. 47
7. 70
6. 17
5.00
3.80
Z.60
1.36
0
10.0
VF
Theoretical
Millivolts
10. 0
0
8.45
7. 75
6.25
5.05
3.90
2.70
1.40
0
10.0
EL
Linearity
Error. %
0
0
+0.2
-0. 5
-0.8
-0. 5
-1.0
-1.0
-0.4
0
0
• Meter adjusted to these values.
TABLE 4. CALIBRATION DATA FOR ATLANTIC RESEARCH
MODEL 101 SMOKEMETER
OF
Filter Value,
% Opacity
0
100
15.5
22. 5
37.5
49.5
61.0
73.0
86.0
Opaque
Clear
°M
Meter Value,
% Opacity
0*
100*
15.8
24.5
41.0
48.8
64.5
71. 2
86. 5
100.0
0
EM
Meter Error,
% Opacity
0
0
+0.3
+2.0
+3.5
-0.7
+ 3.5
-1.8
-0. 5
0
0
VM
Observed
Millivolts
105.4 (=Vc)
24.2 (=Vo)
92.8
85.6
70.6
65.2
52.8
46.8
35.0
24.2
105. 4
VF
Theoretical
Millivolts
105.4
24.2
92.8
87. 1
75.0
65.2
55.9
46. 1
35.6
24.2
105.4
EL
Linearity
Error, %
0
0
0
-1.8
-5.4
0
-3.8
+0.9
-0. 7
0
0
'Meter adjusted to these values.
-------
29.
>-
o
100
90
80
70
60
a?
o
? 50
O
<
ui
cc
cc 40
30
20
10
CORRELATION LINE
10 20 30 40 50 60 70 80 90 100
FILTER VALUE, % OPACITY
+2
+1
o.
O
cc
o
cc
oc
LLJ
DZ -1
LU
HI
-2
JO-
•O-
•O'
o.
10 20 30 40 50 60 70 80 90 100
FILTER VALUE, % OPACITY
FIGURE 21. METER READING AND ERROR OF PHS
SMOKE METER
-------
30.
10.0 Q
9.0 -
8.0 -
O
7.0 -
U 6.0 -
2
of
5.0
O
> 4.0
(-
a.
O 3.0
2.0
1.0 -
THEORETICAL LINEAR OUTPUT
10 20 30 40 50 60 70 80 90 100
FILTER VALUE, % OPACITY
+2
se
of +1
O
cc
cc
LU .*.
> o O
H
cc
<
s -1
-2
v
10 20 30 40 50 60 70
FILTER VALUE. % OPACITY
80 90 100
FIGURE 22. OUTPUT VOLTAGE AND LINEARITY ERROR OF
PHS SMOKEMETER
-------
31,
The Atlantic Research smokemeter had more meter error than
the PHS instrument. Maximum meter error was 3.5- percent opacity
high (Table 4). Meter error was predominantly on the high side, though
the instrument did read low at two points. Figure 23 shows meter reading
and error as functions of filter opacity. Smokemeter output at zero
opacity was 105.4 mv. At 100- percent opacity there was a residual
voltage of 24. 2 mv; i.e., the output did not drop to zero when no light
fell on the photodiode. The observed mv output and linearity error
are shown in Figure 24. Linearity error was, of course, greater for
the Atlantic Research instrument than for the PHS unit.
The Bacharach smokemeter read low throughout the range of
filter opacities. In general, meter error increased with filter opacity
(Table 5). The meter reading and error are shown in Figure 25. When
instrument output was measured, it was found that there was less out-
put (2 mv) at zero opacity than at 100- percent opacity (356 mv). This
is opposite from the output situation of the PHS smokemeter, which in-
creases its output as light intensity on the photocell increases. However,
the Bacharach instrument uses a photoresistive light detector instead
of the photo-voltaic detector used in the PHS unit. Hence, when more
light falls on the Bacharach photocell, the resistance in the meter
(or recorder) circuit increases and voltage output decreases. In any
case, the observed output differed considerably from the theoretical
linear output, and the linearity error was greater than that of the PHS
and Atlantic Research units. Figure 26 shows the output and resulting
error of the Bacharach instrument.
The Nebetco smokemeter could not be checked for accuracy
in the usual manner, as neutral density filters produced completely
erroneous meter readings. In general, meter opacity was from one-
third to two-thirds the value of the filter. However, the apertures
intended for calibration of this instrument produced meter readings
close to their specified value.
It should be noted that the other smokemeters under consideration
are calibrated by absorption of the light beam by a medium, i.e., a
neutral density filter. The Nebetco instrument, however, is calibrated
by reducing light beam intensity by an aperture in the light path. The
important difference in these two methods of calibration is that use of
a neutral density filter approximates what a light-extinction smoke-
meter (and the eye) sees in actual opacity measurement, while the
reduction of light intensity by an aperture does not.
When the smokemeter was calibrated with the reference
apertures, meter readings (Table 6) were low throughout the opacity
range (10- to 90- percent opacity). The meter readings and error for
the Nebetco instrument with the 120- volt power supply are plotted
-------
32.
1:1 CORRELATION LINE
Or 10 20 30 40 50 60 70 80 90 100
FILTER VALUE, % OPACITY
a.
O
as
cc"
O
cc.
cc
0 10 20 30 40 50 60 70 80 90 100
FILTER VALUE.% OPACITY
FIGURE 23. METER READING AND ERROR OF
ATLANTIC RESEARCH SMOKEMETER
-------
33.
120
100
THEORETICAL LINEAR OUTPUT
0 10 20 30 40 50 60 70 80 90 100
FILTER VALUE, % OPACITY
10 20 30 40 50 60 70 80
FILTER VALUE. % OPACITY
90 100
FIGURE 24. OUTPUT VOLTAGE AND LINEARITY
ERROR OF ATLANTIC RESEARCH
SMOKE METER
-------
TABLE 5. CALIBRATION DATA FOR BACHARACH
MODEL 73-7004 SMOKEMETER
34.
OF
Filter Value,
% Opacity
0
100
15.5
ZZ.5
37.5
49.5
61.0
73.0
86.0
Opaque
Cleat
°M
Meter Value,
% Opacity
0*
100*
14.7
19.7
33.4
46.5
53.0
67.5
80.0
100.0
0
EM
Meter Error,
% Opacity
0
0
-0.8
-2.8
-4. 1
-3.0
-3.0
-5.5
-6.0
0
0
VM
Observed
Millivolts
2.0 (=Vc)
356.0 (=Vo)
50.0
67.0
115.0
152.0
194.0
Z31.0
277.0
356.0
2.0
VF
Theoretical
Millivolts
Z.O
356.0
56.9
81.6
134.8
177.2
217.9
260.4
306.4
356.0
2.0
EL
Linearity
Error, %
0
0
1.9
4. 1
5.6
7. 1
6.7
8.3
8.3
0
0
*Meter adjusted to these values.
TABLE 6. CALIBRATION DATA FOR NEBETCO MODEL NLT-1DE
SMOKEMETER WITH MODEL EM-3 POWER SOURCE
OF
Filter Value,
% Opacity
0
100
10.0
20.0
30.0
40.0
50. 0
60.0
70.0
80.0
90.0
Opaque
Clear
0M
Meter Value,
% Opacity
0*
100*
8.0
18.0
26.0
36.0
45.5
54,0
64.5
75.0
89.0
100.0
0
EM
Meter Error,
% Opacity
0
0
-2.0
-2.0
-4.0
-4.0
-4. 5
-6.0
-5.5
-5.0
-1.0
0
0
VM
Observed
Millivolts
3.0 (=Vc)
64.0 (=V0)
3. 5
6.5
10.0
14.5
19.0
24.0
30. 5
41. 5
51.0
64.0
3.0
VF
Theoretical
Millivolts
3.0
64.0
9.1
15.2
Z1.3
27.4
33. 5
39.6
45.7
51.8
57.9
64.0
3.0
EL
Linearity
Error, %
0
0
9.2
14.3
18.5
21. 1
23.8
25.6
'24.9
16.9
11.3
0
0
*Meter adjusted to these values.
-------
35.
100
go
80
> 70
o
n 60
C3
z 50
Q
LU
= 40
QC
30
20
10
1:1 CORRELATION LINE
10 20 30 40 50 60 70 80 90 100
Fl LTER VALUE, % OPACITY
10
20 30 40 50 60 70
FILTER VALUE,% OPACITY
80
100
FIGURE 25. METER READING AND ERROR OF
BACHARACH SMOKEMETER
-------
36.
350
300
CO
O
"a
_j
s
uT
o.
D
O
250
200
oc
o
a:
oc
ID
150
100
50
+8
+7
+6
+5
+4 I-
+3
+2
+1
THEORETICAL LINEAR
OUTPUT
10
20 30 40 50 60 70 80 90 100
FILTER VALUE, % OPACITY
xo—o
10 20 30 40 50 60 70 80
FILTER VALUE, % OPACITY
90 100
FIGURE 26. OUTPUT VOLTAGE AND LINEARITY
ERROR OF BACHARACH SMOKEMETER
-------
37.
in Figure 27. There was a rather large discrepancy between the observed
output and the calculated linear output; in fact, the discrepancy was much
greater than the difference between meter reading and aperture value
would normally imply. The reason for this anomaly is not known.
The output voltage and linearity error are shown in Figure 28. Note
how the linearity error falls off rapidly above 70- percent opacity.
The Nebetco Smokemeter with the portable battery power supply
was also briefly checked for accuracy. This configuration produced
good agreement between meter readings and aperture value. However,
output voltage could not be measured, as the portable unit has no pro-
vision for external output. The meter readings are given in Table 7.
An attempt to calibrate the smokemeter with neutral density filters
again produced very low meter readings.
In summary, the PHS smokemeter had the highest degree of
calibration accuracy, followed by the Atlantic Research and Bacharach
instruments. The 120-volt Nebetco unit, though not calibrated with
neutral density filters, was about as accurate as the Bacharach. The
portable Nebetco was especially accurate up to 70- percent opacity.
However, it is difficult to directly compare the Nebetco with the other
smokemeters, due to the very different methods of calibration.
2. Zero Drift- The zero drift of the four smokemeters is given
below:
Elapsed Time, Zero Drift, % of Chart
Minutes
5
10
15
20
30
45
60
Maximum Drift
Hence, the Bacharach instrument showed the greatest drift over the
one-hour period, and the Nsbetco the least. However, none of the
drifts exhibited by the instruments was considered excessive, espe-
cially for the first 45 minutes. At the end of the one-hour period the
full-scale (opaque) settings were checked. The Bacharach and Nebetco
instruments decreased one percent of scale, while the PHS and Atlantic
Research units showed no change.
PHS
0
+0.
+0.
+0.
40.
+0.
+0.
+0.
2
2
2
2
3
3
3
A.R.
+0.
+0.
0
0
0
-0.
-0.
±0.
2
2
2
2
2
Bacharach
0
0
+0.
+0.
+0.
+1.
+3.
+3.
2
4
8
0
0
0
Nebetco
0
0
0
0
0
0
0
0
-------
38.
100
90
80
> 70
0
<
o 60
1 50
Q
<
LU
^ 40
GC
LU
5 30
20
10
n
/
/o
//
/ o
rf
//
/p
. 1:1 CORRELATION LINE //
\^ srv
y
x/"
X
^^ llllllllll
10 20 30 40 50 60 70 80 90 100
APERTURE VALUE. % OPACITY
10
70
APERTURE VALUE, % OPACITY
80
90 100
FIGURE 27. METER READING AND ERROR OF
NEBETCO SMOKEMETER
-------
39.
70
60
50
40
30
o
>
20
O
10
THEORETICAL LINEAR
OUTPUT
OBSERVED OUTPUT
10 20 30 40 50 60 70 80 90 100
APERTURE VALUE. % OPACITY
cc
O
QC
CC
Ul
>-
E
30
25
.- 20
15
10
30 40 50 60 70
APERTURE VALUE. % OPACITY
100
FIGURE 28.
OUTPUT VOLTAGE AND LINEARITY ERROR OF
NEBETCO SMOKEMETER
-------
40.
TABLE 7. CALIBRATION DATA FOR NEBETCO MODEL NLT-1DE
SMOKEMETER WITH MODEL BM-1 POWER SOURCE
oF
Aperture Value,
% Opacity
0
100
10.0
20.0
30.0
40.0
50.0
60.0
70.0
80.0
90.0
Opaque
Clear
OM
Meter Value,
% Opacity
0*
100*
10.0
10. 0
29.0
39.0
50.0
60.0
73.0
83.0
94.0
100.0
1.5
EM
Meter Error,
% Opacity
0
0
0
0
-1.0
-1.0
0
0
+3.0
+3.0
+4.0
0
1. 5
VM
Observed
Millivolts
No Output
Data with
BM-1
Power
Source
VF
Theoretical
Millivolts
N.A.
EL
Linearity
Error, %
N.A.
*Meter adjusted to these values.
Equations used to find quantities EM. Vp, and EL:
(1)
(2)
(3)
EM = °M ' °F
Vc - V
100
100
E, = .
Vc - Vo
-------
41,
3. Effect of Ambient Light- Changes in each smokemeter's
zero and half-scale settings were measured when a 125-watt spot-
light was directed at the photocell and light source openings from
various angles. The light was aimed directly into these openings and
also reflected off a white reflecting surface into the photocell. The
angles of light incidence were 90, 75, 60, 45, 30, 15 and 0 degrees.
The manner in which these angles were defined is illustrated in
Figure 29 (a). The spotlight was also held at a constant angle of
inclination as it was moved through the various incident angles. This
angle of inclination shown in Figure 29 (b), was the minimum allowed
by the shape of the smokemeter's optical unit.
The test procedure consisted of adjusting a smokemeter to
zero or 50- percent opacity, then shining the spotlight into the openings
or onto the reflector. When measuring the change in zero setting, a
strip chart recorder was used instead of the instrument meter. The
recorder gain control was set so that the zero occurred at midpoint
of the chart. The spotlight was moved in a half circle from 90 degrees
right to 0 degrees, and then to 90 degrees left. Equal right and left
incident angles produced nearly identical changes in the smokemeter
settings. The data in Table 8 are the average of the changes resulting
from identical right and left incident angles.
From the data in Table 8, it can be seen that the effect, if any,
of the ambient light was a reduction in the instrument setting. This was
expected, of course, as the ambient light effectively raises the trans-
mittance of light to the photocell and hence lowers the measured opacity
(even if it is zero opacity). Note also that the changes produced when
the light was reflected into the photocell were greater than those that
occurred when the light shone directly into the opening. This was also
expected, since the reflected light enters the photocell in virtually
the same plane as that from the light source.
The changes in the smokemeter's zero settings, graphed in
Figure 30, show that the Atlantic Research instrument was almost
completely insensitive to the ambient light. The PHS instrument was
only slightly affected, and then just at the two smallest incident angles.
The Bacharach was light sensitive at angles from zero to 45 degrees and
showed larger changes in its zero reading than the PHS unit. The
Nebetco smokemeter was very sensitive to light. Any incident angle
up to 60 degrees produced a change in the instrument's zero setting.
Changes in the instrument's half-scale settings (Figure 31)
follow the same general trend as the zero changes. This trend can
be seen by comparing Figures 30 and 31. The Atlantic Research
smokemeter again proved to be almost insensitive to the ambient
-------
TABLE 8. EFFECT OF AMBIENT LIGHT ON SMOKEMETER ZERO AND HALF-SCALE
Light Incident
Angle, degrees
90
75
60
45
30
15
0
Light Incident
Angle, degrees
90
75
.60
45
30
15
0
Zero Change, % Opacity
PHS
Direct
0
0
0
0
0
-0.5
-2.0
Refl.
0
0
0
0
0
-1.0
-2.5
Atlantic Res.
Direct
0
0
0
0
0
0
0
Refl.
0
0
0
0
0
0
-0. 5
Bacharach
Direct
0
0
0
0
-1.5
-3.0
-4.5
Refl.
0
0
0
-2.0
-3.0
-4. 5
-5.5
Nebetco
Direct
0
0
-0.5
-1.5
-2.0
-4.0
-7.0
Refl.
0
0
-2.0
—3.5
-5.0
-6.0
-7.0
Half-Scale Change, % Opacity
PHS
Direct
0
0
0
0
0
-0.2
-0. 5
Refl.
0
0
0
0
0
-0. 5
-1.0
Atlantic Res.
Direct
0
0
0
.0
0
0
0
Refl.
0
0
0
0
0
0
-0,5
Bacharach
Direct
0
0
-0. 5
-0. 5
-1.0
-1. 5
-3. 5
RefL
0
0
-1. 5
-3.2
-5.0
-6.0
-7.0
Nebetco
Direct
0
0
-1.0
-1. 5
-2. 5
-4.0
-6.0
Refl.
0
-1. 5
-3. 5
-4. 5
-5. 5
-6. 5
-7. 5
DO
-------
43.
PHOTOCELL OR
LIGHT SOURCE
90° LEFT
90° RIGHT
(a) PLANE ANGLE
(b) ANGLE OF INCLINATION
FIGURE 29. ANGLES OF LIGHT INCIDENCE
-1
-2
Q_
O
a?
uT
O
O
QC
111
N
-5
-7
^n
DIRECT
LIGHT
O PHS
D ATLANTIC RES.
A BACHARACH
• NEBETCO
75
60 45 30 15
INCIDENT ANGLE, DEGREES
FIGURE 30. INSTRUMENT ZERO CHANGE AS A FUNCTION OF
AMBIENT LIGHT INCIDENT ANGLE
-------
44.
-1
t
o
*
o
LU
I
U.
-3
-5
I -6
-7
REFLECTED
LIGHT
O PHS
D A.R.
A BACHARACH
• NEBETCO
75
60
45
30
15
INCIDENT ANGLE. DEGREES
FIGURE 31. INSTRUMENT HALF-SCALE CHANGE
AS A FUNCTION OF AMBIENT LIGHT
INCIDENT ANGLE
-------
45.
light, as did the PHS unit. The Bacharach and Nebetco units showed
slight increases in incident angle sensitivity at the half-scale setting.
Next, the light was directed at the light source opening, and the
change in an instrument's zero setting noted. The Atlantic Research
and PHS instruments showed no change whatsoever. The Bacharach
had changes of -0. 5, -1.0, and -1. 5 percent opacity at incident angles
of 30, 15 and 0 degrees, respectively. The Nebetco unit does not have
separate detector and light source openings, so the spotlight was aimed
at the reflector on the other side of the optical head (see description
of Nebetco instrument). This tactic produced virtually the same zero
changes as when the ambient light directly entered the combination
light source-photocell opening.
In summary, the Atlantic Research instrument had the least
sensitivity to ambient light, closely followed by the PHS unit. The
Nebetco and Bacharach had much more sensitivity than the other two
instruments. In passing, it should be noted that the three commercial
smokemeters are intended to be mounted on long extension poles and
held above the exhaust stack. It may be possible to turn an instrument
so that sunlight, the principal ambient light, is at a 90-degree angle
to the smokemeter light beam. This would negate most of the effects
of the ambient light, as no instrument showed sensitivity to light from
a 90-degree incident angle in this bench test.
4. Effect of Ambient Temperature- Changes in each instru-
ments' zero, half-scale (50- percent opacity) and full-scale settings
were measured at temperatures of 75, 100, 125 and 150 degrees F.
Test results are given in Table 9. Changes in zero and half-scale
settings are graphed in Figures 32 and 33, respectively.
The test procedure consisted of adjusting an instrument to
the appropriate zero, half-scale, or full-scale (opaque) setting, at a
baseline temperature of 75 degrees F. The smokemeter was then
allowed to soak in the heat chamber until equilibrium at the desired
temperature was reached. Temperature readings were obtained by
one thermocouple at the instrument's photocell and another at a point
near the light source. After equilibrium was reached the change in
instrument setting was recorded. A typical test involving the four
temperatures required about 30 minutes, so that instrument drift with
time was not a significant factor in the observed changes. Also, since
the entire optical unit was at equilibrium, thermal distortion and
any resulting misalignment of the optical system was at a minimum.
All tests were run at least twice and the data in Table 9 are the average
of these tests.
-------
TABLE 9. EFFECT OF AMBIENT TEMPERATURE ON SMOKEMETER
ZERO, HALF-SCALE, AND FULL-SCALE SETTINGS
46.
Ambient
Temp., °F
75*
100
125
150
Ambient
Temp., °F
75*
100
1Z5
150
Ambient
Temp., °F
75*
100
125
150
Zero Chan
PHS
0
+ 1.0
+3.0
+7.0
Atlantic
Research
0
+0. 5
+2.0
+5. 5
ge, % Opacity
Bacharach
0
+2.5
-2.0
-4.5
Nebetco
0
+4. 0
+6.5
+8.0
Half-Scale Change, % Opacity
PHS
0
+0.2
+ 1.3
+4.0
Atlantic
Research
0
0
-0.5
+0.3
Bacharach
0
-2.5
-6.5
-18.5
Nebetco
0
+ 1. 5
+3.0
+5.2
Full -Scale Change, % Opacity
PHS
0
0
0
0
Atlantic
Research
0
0
0
0
Bacharach
0
-2.0
-5.0
-13.0
Nebetco
0
+0.7
+ 1.0
+0. 5
*Baseline Setting.
-------
47.
12
10
>-
O
O
<*
uT
O
O
cc.
tu
N
-2
O PHS
D ATLANTIC RES.
A BACHARACH
NEBETCO
75
100 125
TEMPERATURE, °F
150
FIGURE 32. INSTRUMENT ZERO CHANGE
AS A FUNCTION OF AMBIENT
TEMPERATURE
-------
48.
t ^
o
<
a.
-2
U
o
-7
-17
-18
-19
O PHS
D ATLANTIC RES
A BACHARACH
• NEBETCO
75
100
125
150
TEMPERATURE, °F
FIGURE 33. INSTRUMENT HALF-SCALE
CHANGE AS A FUNCTION OF AMBIENT
TEMPERATURE
-------
49.
First, consider the changes in the instruments' zero settings.
In general, the smokemeters showed a tendency to increase their zero
setting as the temperature increased. The only exception was the
Bacharach instrument, which had below-zero readings at 125 and 150
degrees F. The Nebetco instrument showed the largest change at 100
and 125 degrees, while the Atlantic Research had the smallest change.
At 150 degrees the Nebetco again had the largest change (8. 0 percent
above zero), while the Bacharach showed the least change (4. 5 percent
below zero). Overall, the Atlantic Research instrument was least
sensitive to changes in ambient temperature. The Nebetco appeared
most sensitive, while the Bacharach and PHS units fell somewhere
in the middle.
The changes in half-scale settings were next measured. Again
the settings tended to increase with increasing temperature, with the
exception of the Bacharach instrument. At all temperatures, the
Bacharach registered thegreatest changes, the largest a drop of 18. 5-
percent opacity below half-scale at 150 degrees F. The Atlantic Research
instrument was almost completely unaffected by the temperature changes.
The PHS and Nebetco units exhibited nominal increases in half-scale
opacity which were between those of the other instruments. Note that
the changes in half-scale settings show approximately the same trend
as the changes in zero settings, though they do not have the same
values (compare Figures 32 and 33).
Changes in full-scale setting (opaque light beam path) were
significant only for the Bacharach smokemeter. This instrument again
showed a decrease from the baseline setting when the ambient temp-
erature was increased. At 150 degrees the drop from baseline reached
13. 0- percent of scale. The Nebetco instrument showed very slight
increases in the full-scale setting, while the PHS and Atlantic Research
units had no detectable changes.
In summary, the Bacharach smokemeter was most affected
by increases in ambient temperature, while the Atlantic Research instru-
ment was least affected. The PHS and Nebetco smokemeters showed
changes between these two extremes. It should be mentioned that
regardless of the change in the instruments' zero, half-scale, or
full-scale setting, all of them could be reset by their calibration adjust-
ments. Thus, heat build-up that might occur during a smoke test could
be compensated for at the end of the test, but not while the test was in
progress. When estimating the effect of temperature on a smokemeter's
performance, consideration should therefore be given to the type of
smoke test to be run, its duration, the number of tests, and whether the
smokemeter can be zeroed and set full-scale between tests. The proxi-
mity of the smokemeter to the exhaust pipe is also important. The opti-
cal system of the PHS instrument is well-removed from the exhaust
stack, but the Atlantic Research and Bacharach units are very close
-------
50.
to the stack in their normal operation. Therefore, it is more likely
that these smokemeters, rather than the PHS, would encounter temp-
eratures similar to those in the bench test.
5. Time Response - The CRC time response test involves the
use of a motor-driven chopper to alternately block and clear the smoke-
meter light beam. The rotational speed of the chopper is adjusted to
the maximum that will produce a square wave time-voltage trace on
an oscilloscope. Thus, the chopper speed is determined by the response
time of the particular smokemeter being tested and is not, in general,
the same rotational speed used with other smokemeters.
The doubt previously mentioned concerning the correctness
of this procedure centered around the idea that the measured time res-
ponse might depend on the speed of the chopper. That is, the rate at
which the light beam is obscured by the chopper blade may determine
the response of the photocell and, hence, the full-scale response
time of the smokemeter. Also, since the chopper speed is not usually
the same for different model smokemeters, the test procedure is
different for every instrument and hence may invalidate the comparison
of data for various smokemeters.
In spite of these doubts, a series of CRC tests was performed
using a variable speed, motor-driven chopper. An oscilloscope was
connected to the smokemeter output terminals, and Polaroid photographs
taken of the time-voltage trace thus obtained. The time response data
from these tests are given in Table 10, below. Both the build-up
(0% - 100%) and decay (100% - 0%) times are shown, and are the average
of three tests.
TABLE 10. SMOKEMETER RESPONSE TIME (CRC PROCEDURE)
Response time, sec.
Smokemeter 0-100% 100-0%
PHS 0.10 0.10
Atlantic Research 0.43 0.20
Bacharach 0.10 0.40
Nebetco 0.57 0.40
Although no information was available concerning response times
of these instruments, it was thought that at least two of them, the PHS
and Bacharach, had response times considerably faster than those
measured. It was therefore decided to repeat the tests, using a different
method of blocking the light beam.
-------
51.
The next series of tests consisted of dropping a wooden sphere
of approximately 3 1/2-inch diameter through the light beam and photo-
graphing the time-voltage trace displayed on the oscilloscope. (Due
to the design of the Nebetco smokemeter, a one-in diameter steel ball
bearing was used in lieu of the wooden sphere). In either case, the
sphere was dropped from the same height in each test, for each smoke-
meter. The data obtained with this procedure are presented in Table 11,
below. These data are also the average of three repeatable tests.
TABLE 11. SMOKEMETER RESPONSE TIME (MODIFIED PROCEDURE)
Response Time, sec.
Smokemeter 0-100% 100-0%
PHS 0.008 0.008
Atlantic Research 0.150
Bacharach 0.020 0.325
Nebetco 0.075* 0.300*
*0-50% of scale
The response times for the PHS, Atlantic Research, and Bacharach
smokemeters were reduced—in some cases, greatly reduced-- when
measured by the second procedure. The Nebetco smokemeter responded
too slowly to achieve full-scale deflection as the sphere passed through
the light beam. Hence, the actual full-scale response time for this
instrument is somewhere between the times given in Tables 10 and 11.
Due to technical problems, apparently in the oscilloscope, no data was
taken on the 100%-0% response time of the Atlantic Research smoke-
meter.
The data in Table 11 are considered to be more accurate than
those in Table 10. The times measured by the second test method are
more in keeping with the obviously fast response of the PHS, Atlantic
Research, and Bacharach instruments. Therefore, on the basis of
the Table 11 data, the PHS instrument had the fastest response, followed
by the Atlantic Research, Bacharach, and Nebetco, in that order. It
should be noted, however, that the most commonly used strip chart
recorders have full-scale response times on the order of 0. 30 to 0. 50
seconds. Hence, although the Atlantic Research and Bacharach smoke-
meters have response times several times slower than the PHS instru-
ment, they still respond faster than the typical recorder.
A third method of time response measurement was also tried.
This procedure consisted of directing a very brief, yet intense, flash
of light into each smokemeter's photocell. Two sources of light were
-------
52.
used in this test, a high-intensity strobe light and a photographic flash
gun. In order to shine the light directly into the photocell, the sources
had to be placed in the smokemeter light beam, thus blocking it com-
pletely. With the smokemeter registering 100-percent opacity, the
light flash was triggered and an attempt made to measure the time
response of the smokemeter as the opacity decreased from 100 percent.
This time corresponds to the delay (100%-0%) time of the other test
procedures.
A fundamental problem was encountered in this procedure;
i.e., the light flash from both sources was too brief in time to permit
the smoke-meter to deflect full scale, to zero opacity. The flash gun
had no adjustment whatever, and the strobe light was adjustable only
to the extent that the time between flashes could be varied; however,
the duration of each flash was fixed. The typical smokemeter would
deflect only five to ten percent of full scale when registering these
light flashes. Therefore, it was concluded that this procedure was
not feasible in its present form. A strobe light with truly adjustable
flash duration might solve the problem mentioned above, but such an
instrument was not available.
D. Smoke Tests With Commercial Smokemeters
The Atlantic Research, Bacharach and Nebetco smokemeters,
along with the PHS instrument, were used to measure smoke opacity
during several series of tests. One series involved a stationary-
mounted Cummins NH-220 engine subjected to the Federal smoke com-
pliance test and a sequence of steady-state runs at several engine speed
and load points. Another series of tests was conducted with the four
truck-tractors and the city bus used to evaluate the smoke test pro-
cedures (Section II). The tests performed by these vehicles were the
simulated Federal smoke test, the pertinent New Jersey test (either
truck lugdown or bus acceleration), the experimental SwRI test pro-
cedure, and the former New Jersey free acceleration test.
1 . Smoke Tests With Stationary-Mounted Engine
The three commercial smokemeters and the PHS instrument
were used to measure smoke opacity of a stationary-mounted Cummins
NH-220 engine subjected to the Federal smoke compliance test and a
sequence of steady-state runs. The tests were conducted in a back-to-
back manner using first the PHS, then one of the commercial smoke-
meters. All tests performed with a given smokemeter were done on
the same day. Four-in diameter exhaust pipe was used for all tests.
-------
53.
a. Federal Smoke Test Results
The Atlantic Research and Bacharach instruments showed
moderate-to-large baseline shifts after each test sequence. After
the first sequence, baseline change was about 7.0- percent opacity;
after the second sequence, it was about 11.0- percent opacity. The
cause of these baseline changes was soot deposit on these instruments'
optical lenses. In order to determine the effect of the baseline change
on opacity readings, two sets of three sequences were performed with
these two smokemeters. For the first set, the lenses were not cleaned
between sequences, while for the second set, the lenses were cleaned
and the instrument zero and full-scale calibration checked between
sequences.
Table 12 contains the data for the Federal smoke tests. Note
that the PHS data varied from one day to another. The tests were
conducted over a two-week period, and there obviously was some change
in the smoke produced by the NH-220 engine. However, the PHS and
any given smokemeter were run back-to-b,ack for comparison on the
same day; hence, there were only small run-to-run variations in the
data used for direct comparison.
TABLE 12. FEDERAL SMOKE TEST DATA--
SMOKEMETER EVALUATION
Smokemeter "a" Factor "b" Factor
Atlantic Res.* 24.8 30.9
Atlantic Res. ** 21.3 28.7
PHS 20.3 28.0
Bacharach* 32.2 37.7
Bacharach** 26.8 32.4
PHS 28.9 33.4
Nebetco 17.6 24.9
PHS 31.6 37.4
*Lenses not cleaned between tests
**Lenses cleaned between tests
From Table 12 it can be seen that the Atlantic Research smoke-
meter gave moderately higher (3-4 percent opacity) "a" and "b" factors
than the PHS instrument when the A.R. lenses were not cleaned between
test sequences, and gave only very slightly higher (1. 0- percent opacity)
factors than PHS when the lenses were cleaned between sequences.
-------
54.
The Bacharach read moderately higher (3-4 percent opacity) than PHS
when its lenses were left uncleaned between sequences, and slightly
lower (1-2 percent opacity) than the PHS instrument when the lenses
were cleaned. The Nebetco smokemeter produced much lower (12-14
percent opacity) "a" and "b" factors than the PHS instrument. Figure
34 illustrates the data in Table 12.
The three commercial smokemeters displayed the same trends
when measuring smoke opacity (with lenses clean) as when their cali-
bration was checked with neutral density filters. That is, the Atlantic
Research instrument calibrated slightly high; the Bacharach calibrated
slightly low. The Nebetco, when calibrated with neutral density filters
rather than with the aperatures provided for this purpose, registered
opacity values one-third to two-thirds the value of the filter. Thus,
the Nebetco instrument cannot be calibrated with either filters or
aperatures in the manner necessary for accurate smoke opacity measure-
ment.
b. Steady-State Smoke Measurement Results
The three smokemeters and the PHS unit were next tested on
the NH-220 engine operating at various steady-state conditions and
using three, four, and five-in diameter exhaust pipes. Engine speeds
were 1600 rpm and 2100 rpm, and engine loads were zero load, full
load, and approximately one-third and two-thirds of full load. These
four load settings produced a wide range of smoke opacities, exhaust
flow rates, and exhaust temperatures.
A special test stand was constructed for this series of tests.
The stand consisted of four 4-1/2-foot lengths of exhaust pipe (of one
diameter) on which were mounted the four smokemeters (Figure 35).
A piece of flexible pipe joined the engine exhaust system to one of
the four pipes on the test stand.
The test procedure consisted of setting the engine speed and
load to the desired condition, allowing a short time for stabilization,
and then connecting the flexible pipe to the test stand pipes for the
PHS and one of the other smokemeters in the following order: PHS,
smokemeter X, PHS, smokemeter X, PHS. Thus, the measurements
made with a given commercial smokemeter were bracketed with
measurements from the PHS instrument. This test procedure provided a
check on the stability of the smoke opacity during the test. It should
be mentioned that this stability was very good, usually ±0.5- percent
opacity at low smoke levels and ±1.0- percent opacity at higher levels,
according to the PHS smokemeter readings. Finally, any instrument
that showed more than 1.0- percent opacity baseline (zero) drift was
recalibrated before continuing with the tests. Optical lenses were
cleaned as needed.
-------
55.
35. 0 r
u 30.0
ft)
a
O
o
E
O
rt
25.0
20. 0 .
15. 0 -
k
Atlantic Res. *
| Atlantic**
CO
a
OH
Bacharach*
I Bacharach**
to
a
Nebetco
CO
a
OH
*Lens Not Cleaned Between Tests
**Lens Cleaned Between Tests
40. Or
- 35.0
u
(Tj -. — —
a 30.0
O
-------
56
:", i^J. -{.,
FIGURE 35. TEST STAND WITH FOUR SMOKEMETERS
-------
57.
The data from this series of tests are presented in Table 13.
The data are the averages of the individual runs (three runs for the
PHS smokemeter, two for all other instruments) made for each engine
condition and each pipe size.
At an engine speed of 1600 rpm, and \\ith three-in diameter
pipe, the three commercial smokemeters gave lower opacity readings
at all engine loads than the PHS instrument. The Bacharach and Atlantic
Research instruments were closest to the PHS, and read some 3-
to 4- percent opacity low at about 19- to 20- percent opacity (by PHS).
The Nebetco smokemeter registered approximately one-half to one-
third the opacity of the PHS.
For 1600 rpm and four-in diameter pipe, the Atlantic Research
instrument read very close to the PHS until full engine load was reached.
At this point the Atlantic Research read about 2.0- percent opacity
lower than the PHS. The Bacharach smokemeter read about 1. 0- percent
opacity higher than the PHS at zero engine load, but agreed very well
with PHS at the other opacity levels. The performance of the Nebetco
was about the same as with the three-in pipe.
At 1600 rpm and using a five-in diameter pipe, the Atlantic
Research smokemeter gave almost exactly the same readings as the
PHS instrument. The Bacharach again read slightly higher (about
1.5- percent opacity) than the PHS at zero engine load, but the two
instruments agreed very well at higher smoke levels. The Nebetco
read close to the PHS at zero engine load, then lapsed into its normal
mode of operation at the higher opacity levels.
Engine speed was increased to 2100 rpm and the above tests
repeated. On three-in diameter pipe the commercial smokemeters
read lower than the PHS instrument by a slightly greater amount than
at 1600 rpm. The Bacharach was closest to the PHS, followed by the
Atlantic Research and Nebetco.
With four-in pipe and 2100 rpm, the commercial smokemeters
again registered lower opacity than the PHS instrument. The Bacharach
read very close to PHS opacity at zero and one-third engine load, then
registered about 2. 5- percent opacity low at the higher smoke levels.
The Atlantic Research smokemeter gave readings some 3.5- to 4.5-
percent opacity below PHS at these high opacity conditions. The diff-
erence between the PHS and Nebetco instruments were again quite
large.
For 2100 and five-in pipe the Atlantic Research instrument
read slightly lower than PHS opacity at zero and full engine loads, and
slightly higher than PHS at one-third load. The Bacharach registered
-------
58.
TABLE 13. STEADY-STATE SMOKE TEST DATA -- SMOKEMETER EVALUATION
Engine Speed: 1600 rpm
Exhaust Pipe Diameter: 3 in
Engine
Load
0
1/3
2/3
Full
Exhaust Pipe
Engine
Load
0
1/3
2/3
Full
Exhaust Pipe
Engine
Load
0
1/3
2/3
Full
PHS
1. 1
7. 8
16.0
20. 0
Diameter:
PHS
1. 1
9.5
22. 5
27. 5
Diameter:
PHS
1. 5
9.8
18. 5
28. 1
A.R.
0.5
5.6
11. 8
16. 1
4 in
A.R.
1.3
10.5
21. 8
25.6
5 in
A.R.
1. 3
9.8
18. 8
28. 7
Smoke
PHS
1. 7
7.4
15.2
19.3
Smoke
PHS
1.9
10.4
22.0
26. 5
Smoke
PHS
1. 1
11. 1
21. 3
28. 7
Opacity, %
Bacharach
0.9
5.8
12.8
16.0
Opacity, %
Bacharach
3.0
11.0
21.4
27.0
Opacity, %
Bacharach
2. 5
11.0
20. 5
27.8
PHS
1. 3
7.6
15.0
17. 7
PHS
1.4
11. 2
21.9
27. 5
PHS
2. 3
11. 5
23. 2
28. 2
Nebetco
0. 3
2.9
6.0
8. 1
Nebetco
0. 7
4 .6
9.9
12. 1
Nebetco
1.8
3.9
11. 3
21.0
-------
TABLE 13. STEADY-STATE SMOKE TEST DATA -
(Cont'd)
Engine Speed: 2100 rpm
59.
- SMOKEMETER EVALUATION
Exhaust Pipe Diameter: 3 in
Engine
Load
0
1/3
2/3
Full
Exhaust Pipe
Engine
Load
0
1/3
2/3
Full
Exhaust Pipe
Engine
Load
0
1/3
2/3
Full
PHS
2.6
10.8
16.5
24.8
Diameter:
PHS
1.7
13.7
20.5
30.3
Diameter:
PHS
4.0
14.3
21.5
32.8
A.R.
1.0
7.5
16.8
18. 3
4 in
A.R.
1.3
11.2
17.0
25.8
5 in
A.R.
2.1
16.0
21.5
31.3,
Smoke
PHS
1.8
7. 5
13. 3
21.7
Smoke
PHS
1.6
15.0
23.2
31.5
Smoke
PHS
3. 7
15.9
22.0
33.0
Opacity, %
Bacharach
1.1
6.5
11.0
17.0
Opacity, %
Bacharach
2. 1
14.3
20.8
28. 8
Opacity, %
Bacharach
4.4
15.5
24. 5
36.5
PHS
2.4
11.2
16. 1
23. 5
PHS
1.3
14.2
22.2
32. 5
PHS
1.6
11.7
19.8
32.7
Nebetco
0
4.8
6.9
9.8
Nebetco
0.4
4. 1
9.4
12.8
Nebetco
0.3
4.2
7.0
12.6
-------
60.
opacities very close to those of the PHS instrument at zero and one-
third engine loads, and then read 2. 5- to 3.5- percent opacity higher
than PHS at the high smoke levels. The mode of operation of the
Nebetco smokemeter was unchanged from previous tests.
Several conclusions can be drawn from the test results for
steady-state smoke conditions. First, the Atlantic Research and
Bacharach smokemeters agreed much more closely with the PHS
instrument, for all of the above engine conditions and pipe sizes,
than the Nebetco smokemeter. Second, the differences (in percent
opacity) between the readings of the PHS smokemeter and the com-
mercial smokemeters are greater at 2100 engine rpm than at 1600 rpm.
Third, the data taken by the commercial smokemeters under steady-
state smoke conditions with four-in diameter pipe show the same
general trends (when compared to the PHS readings) as the Federal
smoke test data discussed in Section I. Last, the differences between
the PHS and the other smokemeters decrease as pipe diameter in-
creases, and this condition holds true for the two engine speeds and
four loads used in these tests.
It was mentioned previously that the Bacharach smoke-
meter uses a grid network in the sensor head. The stated purpose
of this "eggcrate" is to straighten the exhaust plume before it passes
through the smokemeter light beam, and to create a pressure drop
that is supposed to sweep air over the optical lenses. The grid as-
sembly is constructed from some lightweight, non-magnetic material,
probably aluminum or magnesium. Both of these metals melt at 650-
660°C (1200-1220°F). The grid assembly was inadvertently subjected
to full-power exhaust temperature from the NH-220 engine for an ex-
tended period of time (approximately 3-4 min ). The result of this
action is shown in Figure 36. The grid material melted and was blown
away by the exhaust, leaving a circular hole some 2. 5-in. in diameter.
While it must be admitted that the Bacharach instrument was not de-
signed for extended use at high exhaust temperatures, this incident
does point out the need for caution in its use. No problems were
encountered when using this smokemeter during the full-power lug-
down of the Federal smoke test. This lugdown is of 30-40 second
duration.
Another grid assembly was obtained from Bacharach and
installed according to their instructions. This approach, which was
approved by the Project Officer, allowed continued use of the same
basic instrument. The Bacharach Company offered another instru-
ment as a replacement, but it was feared that use of another smoke-
meter would disrupt the continuity of the evaluation.
-------
61
FIGURE 36. DAMAGED GRID IN BACHARACH SMOKEMETER
At this point in the project, a decision was also made by the
Project Officer concerning the Nebetco smokemeter. This instru-
ment had consistently failed to demonstrate an acceptable level of
performance in the bench tests or the smoke tests. The decision was
therefore made to exclude the instrument from further tests, and hence
restrict evaluation to the Atlantic Research and Bacharach smoke-
meters .
2. Truck Smoke Tests
The test plan consisted of performing the complete series of
tests (Federal, New Jersey lugdown, SwRI, and New Jersey free accel-
eration) with the PHS smokemeter, followed by the two commercial
instruments and winding up with the PHS. All tests involving a parti-
cular vehicle were conducted on the same day. The data shown in
Table 14 for the Atlantic Research and Bacharach smokemeters are
averages of at least three repeatable runs for each test procedure.
The PHS data are averages of at least six repeatable runs.
The data in Table 14 were compared to establish correlations
between the PHS smokemeter and the two commercial instruments.
This comparison was first done in a qualitative manner, then in a more
quantitative way. The data are illusteated in Figures 37 to 44 as an
aid to comparison. There are two figures for each of the four engines
used in the study. One figure illustrates the time-averaged-data ("a"
and "b" factors) and the other shows the peak data for the various
accelerations and lugdowns.
-------
TABLE 14.
SMOKE TEST DATA FOR PHS, ATLANTIC RESEARCH, AND BACHARACH
SMOKEMETERS FOR FOUR TRUCK TEST PROCEDURES
Federal (Chassis Dyna. )
New Jersey Truck Lugdown
SwRI Accel. - Max Power
Smokemeter
PHS
Atlantic Res.
Bacharach
PHS .
Atlantic Res.
Bacharach
PHS
Atlantic Res.
Bacharach
PHS
Atlantic Res.
Bacharach
Smoke Opacity, %
"a" Accel. "b"
Factor* Peak Factor*
Engine:
13. 5
12. 5
11. 1
Engine:
35. 1
25.6
25.7
Engine:
10.2
8.7
10. 7
Engine:
27. 2
23. 1
28.5
Cummins NHC-250
24.2 12.2
25.5 12.4
20.9 10.2
Cummins NHC-250
38.8 38.0
30.0 27.0
33. 1 30.4
Cummins NTC-335
38.8 2.6
35.9 1.5
42. 8 3. 2
Caterpillar 1 1 50
97. 1 24.9
93.0 20.0
96.5 24.6
Smoke Opacity, %
Lug
Peak
(No.
16.
15.
13.
(No.
40.
28.
33.
3.
2.
3.
27.
21.
26.
M
1
7
6
2)
4
4
6
0
1
6
4
6
9
"a" Accel.
Factor* Peak
9.
9.
10.
18.
18.
18.
42.
38.
45.
22.
24.
28.
6
1
3
0
5
8
2
8
6
0
7
1
20.
17.
18.
29.
26.
28.
64.
60.
77.
79.
81.
89.
8
2
3
1
1
4
0
o
0
4
4
2
"b"
Factor*
8.
7.
8.
31.
23.
29.
2.
1.
5.
12.
9.
13.
8
6
7
4
1
0
2
4
1
6
4
6
Lug
Peak
10.
9.
10.
32.
23.
31.
2.
2.
6.
17.
10.
15.
8
2
8
4
5
1
8
2
2
9
6
2
Smoke Opacity, %
"a" Accel.
Factor* Peak
14.
16.
1 1.
20.
24.
23.
37.
37.
45.
26.
25.
31.
2
6
5
6
5
9
6
0
0
8
0
9
18.
20.
15.
29.
26.
25.
50.
52.
60.
89.
85.
88.
4
0
5
8
2
1
6
1
4
3
7
4
"b"
Factor*
14.
16.
11.
27.
24.
22.
2.
2.
9.
J5.
12.
17.
5
0
3
0
5
7
4
0
3
4
1
8
Max. Power
Peak
16.
17.
12.
27.
24.
24.
3.
2.
10.
18.
17.
21.
3
5
5
9
9
5
0
8
2
2
0
5
New Jersey Free Accel.
Smoke Opacity, %
Accel.
Peak
15.9
13. 2
11.0
29.6
33. 8
30.9
59.6
58.2
57.2
23.2
16.0
21.0
* Time-averaged data
CM
-------
63.
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FIGURE 37. TIME-AVERAGED SMOKE OPACITY AS MEASURED BY THE
PHS, ATLANTIC RESEARCH, AND BACHARACH SMOKEMETERS, FOR
THREE TEST PROCEDURES - CUMMINS NHC-Z50 ENGINE (NO. 1)
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FIGURE 39. TIME AVERAGED SMOKE OPACITY AS MEASURED BY THE
PHS, ATLANTIC RESEARCH, AND BACHARACH SMOKEMETERS, FOR
THREE TEST PROCEDURES - CUMMINS NHC-250 ENGINE (NO. Z)
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Federal Smoke Test N. J. Truck Test SwRI Smoke Test Accel.
FIGURE 40. PEAK SMOKE OPACITY AS MEASURED BY THE PHS, ATLANTIC
RESEARCH, AND BACHARACH SMOKEMETERS, FOR FOUR TEST
PROCEDURES - CUMMINS NHC-250 ENGINE (NO. 2)
-------
65.
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FIGURE 41. TIME-AVERAGED SMOKE OPACITY AS MEASURED BY THE PHS,
ATLANTIC RESEARCH, AND BACHARACH SMOKEMETERS, FOR THREE
TEST PROCEDURES - CUMMINS NTC-335 ENGINE
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67.
In comparing the "a" factors generated by the PHS smokemeter
with those of the other instruments, it was found that the Atlantic Research
correlated best with the PHS in a majority of the tests. The Atlantic
Research tended to produce lower "a" factors than the PHS, while the
Bacharach "a" factors were generally higher. The Bacharach "b"
factors were closest to, and tended to be lower than, the PHS "b"
factors. The Atlantic Research also usually read lower lugdown smoke
opacity than the PHS smokemeter.
The Atlantic Research instrument correlated best with the PHS
in the area of peak acceleration opacity. Both commercial smoke -
meters generally read lower peak opacity than the PHS. The Bacharach
and Atlantic Research correlated best with the PHS in an equal number
of instances. Again, both instruments tended to read lower than the
PHS. The same qualitative comparison holds true for the free accel-
eration peak opacities as for the lugdown peak opacities.
An overall summary of the data reveals that the Atlantic
Research smokemeter correlated best with the PHS in 52% of the
tests, and the Bacharach correlated best in, of course, the remaining
48% of the tests. The Atlantic Research read lower opacity than the
PHS 77% of the time (and higher 23% of the time), while the Bacharach
read lower 55% of the time (and higher 45% of the time).
The quantitative analysis of the data in Table 14 is summarized
below. The numbers given are the average differences, in percent
opacity, between the PHS data and the data for the Atlantic Research
and Bacharach smokemeters. Note that these differences are derived
from readings both above and below the PHS data. This fact is empha-
sized by the column labled "Bias", which indicates whether the opacity
Atlantic Research Bacharach
% Opacity Bias % Opacity Bias
"a" Factors 2.7 Low 3.6 High
"b" Factors 3.2 Low 2.8 Low
Accel. Peaks 3.3 Low 3.8 Low
Lugdown Peaks 3.6 Low 3.0 Low
Free Accel. Peaks 3.9 Low 2.7 Low
readings tended to be above ("High") or below ("Low") those of the
PHS.
This summary of opacity differences shows that the Atlantic
Research readings were closest to the PHS readings for the "a" factors
and the acceleration peak opacities, while the Bacharach was closest
-------
68.
for the "b" factors, the lugdown peaks, and the free acceleration
peaks. These quantitative statements differ from those in the quali-
tative discussion given previously, in that the latter dealt only with
the number of instances where one smokemeter read closer to the
PHS than did the other smokemeter, while the former deals with
specific average magnitudes (percent opacity) of difference. This is
pointed out to prevent the reader from thinking there is a contradic-
tion in the fact that both smokemeters read closest to the PHS in an
equal number of instances (for, say, the free acceleration tests),
yet the readings of one instrument (in this case, the Bacharach)
were on the average closer to those of the PHS.
In conclusion, there was little difference between the two
commercial smokemeters in this series of comparison tests. The
Atlantic Research read closer to the PHS in a slightly greater number
of tests, while the Bacharach actually read closer on the average.
3. Bus Smoke Tests
The test plan for this series of tests was to perform the Federal,
SwRI, and free acceleration tests on the chassis dynamometer, then
perform the New Jersey acceleration test on the road. The nominal
smoke opacity of the bus was set at the desired level, and all three
chassis dynamometer tests were performed using a given smoke-
meter to measure opacity. The tests were then repeated, at the same
smoke level, with a different smokemeter. The PHS instrument was
used initially, followed by the Atlantic Research and Bacharach smoke-
meters and finishing with the PHS. The data from the commercial
smokemeters are the average of three repeatable runs, while the PHS
data are the average of six repeatable tests.
The data in Table 15 were compared in the same manner as
the data from the truck smoke tests. That is, the comparison was
done first in a qualitative manner, then in a more quantitative sense.
The data are illustrated in Figures 45 through 52 to facilitate the com-
parisons. There is one figure for the time-averaged data ("a" and
"b" factors) and one figure for each peak opacity data, for each smoke
level.
The Bacharach smokemeter read closest to the PHS instru-
ment in a large majority of both average and peak data for all four
test procedures. Both commercial instruments read lower than the
PHS in nearly every instance. These results agree, onthe whole,
with the truck test results obtained with these instruments. In those
tests the Bacharach produced generally higher "a" factors than the
PHS, but read lower than the PHS in the areas of peak acceleration,
-------
TABLE 15.
SMOKE TEST DATA FOR PHS, ATLANTIC RESEARCH, AND BACHARACH
SMOKEMETERS FOR FOUR BUS TEST PROCEDURES
Federal (Chassis Dyna. )
Smokemeter
Smoke Opacity, %
New Jersey
Bus. Accel.
Smoke Opacity, %
"a" Accel. "b" Lug
Factor* Peak Factor* Peak
"a"
Factor*
Accel.
Peak
SwRI
Accel. -Max Power
New Jersey Free Accel.
Smoke Opacity, %
"a" Accel.
Factor* Peak
"b"
Factor*
Max. Power
Peak
Smoke Opacity, %
Accel.
Peak
First Smoke Level
PHS
Atlantic Res.
Bacharach
PHS
Atlantic Res.
"Bacharach
5.2
4.3
4.2
Second
13.2
11.7
10.8
7.2 5.6
5.4 4.3
4.8 4.7
Smoke Level
15.6 12.8
13.7 11.1
13.6 9.6
6.0
4.7
5.1
14.2
10.9
10.4
3.
2.
2.
8.
6.
5.
5
8
9
0
0
9
4.4
3.5
3.8
10.4
7.6
8.2
4.1
3.2
3.5
10.3
8.4
10.0
4.4
3.8
4.4
14.0
10.8
12.5
4.4
3.1
4.5
13.6
10.3
11.8
4.9
3.4
5.1
14.6
11.0
12.3
4.
3.
4.
17.
13.
14.
6
2
9
0
0
8
Third Smoke Level
PHS
Atlantic Res.
Bacharach
PHS
Atlantic Res.
Bacharach
21.9
16.7
19.5
Fourth
37.6
31.1
34.0
25.0 21.7
19.0 16.9
22.3 18.3
Smoke Level
43.4 36.4
35.2 30.0
39.9 32.9
22.8
17.9
19.0
38.7
34.1
34.7
14.
11.
12.
20.
16.
15.
2
0
2
0
0
9
18.2
14.1
15.2
25.1
20.8
20. 1
19.5
14.2
17.4
28.6
21.6
23.8
24.2
18.3
22.1
34.5
26.9
31.1
24.2
18.5
22.3
38.9
31.4
36.0
25.6
19.7
23.0
41.2
33. Z
37.6
34.
29.
32.
47.
36.
40.
5
0
0
8
0
0
*Time Averaged Data
-------
70.
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Federal Smoke Test N. J. Bus
Accel. Lugdown
SwRI Smoke Test
FIGURE 47. TIME-AVERAGED SMOKE OPACITY AS MEASURED BY THE
PHS, ATLANTIC RESEARCH, AND BACHARACH SMOKEMETERS, FOR
THREE TEST PROCEDURES -- 6V-71 ENGINE AT SECOND SMOKE LEVEL
18 r
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Federal Smoke Test N. J. Bus SwRI Smoke Test Accel.
FIGURE 48. PEAK SMOKE OPACITY AS MEASURED BY THE PHS
ATLANTIC RESEARCH, AND BACHARACH SMOKEMETERS, FOR
FOUR TEST PROCEDURES -- 6V-71 ENGINE AT SECOND SMOKE LEVEL
-------
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FIGURE 49. TIME-AVERAGED SMOKE OPACITY AS MEASURED BY THE
PHS, ATLANTIC RESEARCH, AND BACHARACH SMOKEMETERS, FOR
THREE TEST PROCEDURES -- 6V-71 ENGINE AT THIRD SMOKE LEVEL
35 r
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-------
74.
peak lugdown, and time-averaged lugdown opacity. In summary, the
Bacharach smokemeter correlated best with the PHS in 79. 5% of the
tests, while the Atlantic Research correlated best in the remaining
20. 5% of the tests. The Atlantic Research read lower than the PHS
in every case, and the Bacharach read lower in some 95% of the tests.
The results of the quantitative analysis of the data in Table 15
are given below. The numbers represent the average differences, in
percent opacity, between the PHS data and those of the Atlantic Research
and Bacharach smokemeters. The column labeled "Bias" indicates
whether the opacity readings were generally higher or lower than the
PHS readings. Note that the Bacharach smokemeter read much closer
Atlantic Research
Bacharach
% Opacity
3.3
4. 0
3.9
4. 1
5. 7
Bias
Low
Low
Low
Low
Low
% Opacity
2. 2
2. 2
2.4
2.6
3.2
Bias
Low
Low
Low
Low
Low
"a" Factors
"b" Factors
Accel. Peaks
Lugdown Peaks
Free Accel. Peaks
to the PHS in every data category than did the Atlantic Research instru-
ment. This is in marked contrast to the trends shown by the data for
the truck smoke tests, in which the two commercial smokemeters were
approximately equal in their performance, as compared to the PHS
instrument.
-------
75.
IV. OTHER TESTS WITH PHS SMOKEMETERS
The work performed in this section includes two special
investigations performed at the request of the Project Officer. The
first investigation concerned the degree of correlation that exists be-
tween several PHS smokemeters. It was already known that the PHS
instruments correlate very well in static filter calibration tests, but
little information was available concerning the correlation during
actual smoke measurement. Therefore, a series of smoke tests
was conducted to determine the consistency of the opacity values ob-
tained with three typical PHS smokemeters.
The second investigation involved a series of smoke tests
with a standard PHS smokemeter and two large-diameter PHS smoke-
meters. These enlarged versions were constructed for use on very
large exhaust ducts of non-automotive types of diesel engines. It was
deemed of interest to determine the degree of correlation between the
large-diameter instruments and the standard PHS smokemeter when
they were used on a truck-size engine and exhaust system. The re-
sults of this correlation study would also shed light on the effect of
the smokemeter light beam path length on opacity readings.
A. Correlation of Three PHS Smokemeters
A series of steady-state smoke tests were performed with the
stationary-mounted NH-220 engine, using three PHS smokemeters.
These tests were to determine the variation in opacity measurements
at various engine speeds and loads for three identical PHS instruments.
The three PHS instruments were mounted on three-, four-,
and five- in diameter exhaust pipes on the test stand previously des-
cribed (Figure 53). The engine speeds used were 1600 and 2100 rpm,
and engine loads were zero load, full load, and approximately one-
third and two-thirds of full load. After engine load and speed were
stabilized, the flexible exhaust pipe was connected in turn to each of
the three smokemeters.
The data for this series of tests are contained in Table 16.
The excellent agreement shown by the smokemeters is evident. The
largest variation was 1. 0- percent opacity, and most of variations
were 0.5- percent opacity, or less. The smokemeters were calibrated
before and after a set of tests for a given pipe size, using neutral
density filters of approximately 20- and 36- percent opacity. The
calibrations were accurate to ±0. 5- percent opacity.
Of special interest is the average smoke opacity for the three
PHS smokemeters for each engine speed, load, and exhaust pipe size
-------
76.
FIGURE 53. THREE PHS SMOKEMETERS ON TEST STAND
(Table 16). Note that the indicated smoke opacity for each engine
speed and load increased as the pipe diameter increased. These
increases in opacity are shown in Figures 54 and 55 as a function of
engine load. The figures illustrate the consistency of the ob-
served changes.
At full engine load at 1600 rpm, the average measured smoke
opacity from the three-in pipe was 18.2- percent and that from the
five-in pipe was 26.8- percent, an increase of nearly 50 percent.
At 2100 rpm and full engine load, the average measured opacity from
the three-in stack was 19. 7- percent and that from the five-in pipe
was 33. 7- percent, an increase of over 70 percent.
It should be mentioned here that each smokemeter was mounted
on the exhaust pipes such that the distance from the end of the pipe to
the center of the light beam was six in. The Federal Register pres-
cribes a distance of 1.0-1.5 pipe diameters when performing the
Federal smoke compliance test. Hence, the distance used for this
series of tests was within the specified range for four-in and five-in
diameter pipes, but was somewhat more for the three-in pipe. How-
ever, mounting the smokemeters on the three-in pipes in this manner
allowed the rather narrow exhaust plume to diverge and fill the smoke-
meter ring.
-------
77.
TABLE 16. STEADY-STATE SMOKE TEST DATA FOR
THREE PHS SMOKEMETERS
Engine Speed: 1600
Exhaust Pipe Diameter: 3 in
Engine
Load
0
1/3
2/3
Full
Exhaust Pipe
Engine
Load
0
1/3
2/3
Full
Exhaust Pipe
Engine
Load
0
1/3
2/3
Full
Smoke Opacity, %
PHS #1
1. 0
6.7
13. 5
18. 5
Diameter: 4 in
PHS #1
1. 7
8. 5
16. 5
20. 0
Diameter: 5 in
PHS #1
2. 3
11. 5
19.5
27. 0
PHS #2
1.0
6.2
13.0
18.0
Smoke
PHS #2
1. 5
8.0
16.5
21. 0
Smoke
PHS #2
2.0
11. 0
19.5
26. 5
PHS #3
1.3
6.7
13.0
18. 0
Opacity, %
PHS #3
1. 5
8. 0
16. 0
20. 0
Opacity, %
PHS #3
2. 3
11.0
18. 5
27. 0
Average
1.1
6.5
13.2
18.2
Average
1.6
8.2
16.3
20. 3
Average
2. 2
11. 2
19.2
26.8
-------
78.
TABLE 16. STEADY-STATE SMOKE TEST DATA FOR
THREE PHS SMOKEMETERS (con't)
Engine Speed: 2100 rpm
Exhaust Pipe Diameter: 3 in
Engine
Load
0
1/3
2/3
Full
Exhaust Pipe
Engine
Load
0
1/3
2/3
Full
Exhaust Pipe
Engine
Load
0
1/3
2/3
Full
PHS #1
1. 7
8. 7
12.5
19.5
Diameter: 4 in
PHS #1
2. 5
11.0
16. 5
26.5
Diameter: 5 in
PHS #1
3. 5
14. 5
21.5
33.5
Smoke
PHS #2
1.8
8. 3
12.0
20. 0
Smoke
PHS #2
2. 5
11. 3
17. 0
26. 0
Smoke
PHS #2
3. 3
13. 5
22. 0
33. 5
Opacity, %
PHS #3
1.6
8. 3
12.0
19.5
Opacity, %
PHS #3
2. 3
11. 5
17. 0
27.0
Opacity, %
PHS #3
3. 3
14. 5
22. 0
34. 0
Average
1.7
8.4
12. 2
19.7
Average
2.4
11.3
16. 8
26.5
Average
3.4
14. 2
21. 8
33. 7.
-------
79.
u
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8
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30
25
20
15
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a
0 L
5 in
1/3 2/3
Engine Load
Full
FIGURE 54. EFFECT OF EXHAUST STACK DIAMETER
ON SMOKE OPACITY - 1600 RPM
35
30
25
I 20
0)
CO
ffi 10
0,
0 L »-
5 in
in
1/3 2/3
Engine Load
Full
FIGURE 55. EFFECT OF EXHAUST STACK DIAMETER
ON SMOKE OPACITY - 2100 RPM
-------
80.
As a matter of interest, the average data in Table 16 for the
three-in and five-in diameter pipes were corrected by the Beere-
Lambert law. The opacity data for these pipe sizes were calculated
on a four-in basis and these corrected data are given in Table 17.
At 1600 rpm, the corrected opacities from the three-in and
five-in pipes agree quite well with the measured opacities from the
four-in stack. The only anomaly is at full engine load, where the
corrected opacities are two- to three- percent opacity higher than the
observed opacities for this pipe size. However, note in Figure 54
that the data point for this condition is two- to three- percent opacity
low when compared to the other points. (It is likely that the engine
was not at full load, and smoke opacity was therefore slightly lower
than it should have been. ) Hence, the Beere-Lambert law, when
applied to the full-load opacity data for the three-in and five-in pipes,
predicts the smoke opacity for the four-in pipe. At 2100 rpm, the
corrected opacities agree well with the observed opacities for the four-
in stack throughout the range of engine loads. The greatest difference
is 1.2- to 1.5- percent opacity at approximately*26. 5- percent opacity.
%
It should be noted that the PHS data in Table 13 of the preceding
Section also shows an increase in opacity as pipe diameter increases.
However, the data in Table 16 was considered more conclusive since
they were obtained by three PHS instruments operating in a highly
repeatable manner. The data in Table 13 can be considered further
substantiation of the effect of pipe size on observed opacity. For
further information on this effect, refer to the final report, "An
Investigation of Diesel-Powered Vehicle Odor and Smoke - Part II",
dated February 1968, 11. 104-7. This report covers work performed
under Contract No. PH 86-67-72 for the National Center for Air Pollution
Control of the U. S. Department of Health, Education, and Welfare.
B. Correlation of Ten-, Twenty-, and Forty- inch Diameter
PHS Smokemeters
Another EPA project performed at the Emissions Research
Laboratory (under Contract EHS 70-108, "Study of Exhaust Emissions
from Uncontrolled Vehicles and Related Equipment Using Internal
Combustion Engines") called for a series of smoke tests of diesel-
powered locomotives. Since the standard PHS smokemeter, with
ten-in diameter ring, was much too small for the large exhaust ducts
of these engines, two large-diameter PHS instruments of 20- and 40-in
diameter were designed and constructed by SwRI. These instruments
were constructed using the standard PHS optical components (colli-
mating tubes, lens, lamp, and photocell) and the standard readout box
used with the ten-in smokemeter. The 20- and 40-in rings were formed
from a band of aluminum four-in wide by one-half in thick.
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81
TABLE 17. SMOKE OPACITY DATA CORRECTED
BY BEERE-LAMBERT LAW*
Engine Speed: 1600 rpm
Smoke Opacity, %
Engine
Load
0
1/3
2/3
Full
Engine Speed:
Engine
Load
0
1/3
2/3
Full
3 -in Pipe
(corrected to 4 in)
1. 5
8. 5
17.2
23.4
2100 rpm
3 -in Pipe
(corrected to 4 in)
2.2
11.0
15.9
25. 3
5 -in Pipe
(corrected to 4 in)
1.8
9.1
15.7
22. 1
Smoke Opacity, %
5 -in Pipe
(corrected to 4 in)
2.7
11.5
17.8
28.0
4-in Pipe
(as measured)
1.6
8.2
16.3
20.3
4-in Pipe
(as measured)
2.4
11.3
16.8
26.5
*The equation of the Beere- Lambert law is
O2 = 10o{l.O - antilog
where
. O-Oi/100) •
Oj : measured smoke opacity, %
Dl = actual stack. diameter
D£ = desired stack diameter
©2 = calculated smoke opacity for stack of diameter
-------
82.
The performance of these instruments was entirely satisfactory.
Calibration with neutral density filters was very accurate, and the
instruments' response times were judged equal to that of the 10-in
diameter smokemeter. The results of the locomotive smoke tests with
the large-diameter instruments were likewise termed satisfactory
by test personnel.
The Project Officer, when informed of the existence of these
smokemeters, requested that a brief series of smoke tests be per-
formed to establish the correlation between their opacity reading and
those of the ten-in smokemeter. Accordingly, the 10-, 20-, and
40-in instruments were mounted on the multi-pipe test stand (Figure 56).
Three- and four-in diameter exhaust pipes were used, and the Cummins
NH-220 engine was operated at 1500 and 2100 rpm. Engine loads were
full load and approximately one-third and two-thirds of full load, which
resulted in smoke opacities from twelve to forty percent. The test
plan consisted of passing exhaust through each of the three smokemeters,
in turn, as the engine speed and load were held constant.
The chief result of these tests was the discovery that the nominal
opacities registered by the three smokemeters were very close. The
emphasis is on "nominal", since there was a substantial difference
in the amount of variance, or "hash", in the opacity traces furnished
by the three instruments. This phenomenon was more pronounced
with the 40-in smokemeter than with the 20-in instrument, and more
in evidence with the 20-in than with the standard ten-in smokemeter.
It was also more apparent in the tests with four-in diameter pipe than
for those with three-in pipe and was greater at 1500 rpm than at 2100 rpm.
To site the extremes of the observed variations, the variance from the
nominal (or average) opacity measured by the ten-in smokemeter on
four-in pipe was approximately ±3.0- percent opacity at 1500 rpm and
full load while the 20- and 40-in instruments showed variances of about
5.0- and 8.0- percent opacity, respectively. However, the average
opacity values registered by the three smokemeters were within about
one percent opacity of each other. When the smokemeters were placed
on three-in diameter pipes, the opacity traces obtained at 2100 rpm were
virtually identical in their amount of variance and average values.
The speed at which exhaust gases exit the pipe increases when
engine speed is increased and/or as the pipe diameter is decreased.
Also, the rate at which the smoke diverges from the pipe into a plume
is increased as the exit velocity of the exhaust is decreased. Therefore,
the amount of "hash" in the opacity traces is related to the exit velocity
of the exhaust gases, as well as to the usual influence of exhaust pulsa-
tions. This relationship is well known to most users of the PHS smoke-
meter. The point to be made here is that this effect is magnified when
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83.
•
FIGURE 56. TEN-, TWENTY-, AND FORTY-INCH DIAMETER
PHS SMOKEMETERS ON TEST STAND
-------
84.
the size of the smokemeter ring is increased. Since the light beam
path length is increased in the 20- and 40-in instruments, it is important
to note that there was little discernible difference in the nominal opacities
measured by the three smokemeters. Hence, the effect of a longer path
length on measured opacity appears to be nil, at least for this series
of tests with a truck-size diesel engine with highly pulsating exhaust
flow.
-------
85.
V. EVALUATION OF OTHER COMMERCIAL SMOKEMETERS
The smokemeters from Atlantic Research, Bacharach, and
Nebetco were selected in advance of the beginning of the project as
the commercial instruments which would undergo evaluation. Shortly
after the project began, the Project Officer expressed interest in three
other commercial smokemeters. One was an inline instrument made
by Atlantic Research, while the other two smokemeters, one an inline
model and the other for end-of-line use, were made by the Robert
H. Wager Co.
The evaluation test plan for these instruments took two different
forms. First, since the Atlantic Research inline was already in pro-
duction and in actual use in some research programs, it was decided
to subject this instrument to the complete series of bench tests and
an extensive series of smoke tests. Second, the Wager instruments
were prototypes not yet in production. It was therefore decided that
these smokemeters should undergo a somewhat abbreviated series of
bench and smoke tests. The results of these tests would determine
whether the two smokemeters would be subjected to further evaluation.
A. Evaluation of Atlantic Research Inline Smokemeter
The Atlantic Research Corporation furnished a Model 103 inline
smokemeter to the project for evaluation. This instrument was sub-
jected to a series of bench tests and smoke tests similar to those per-
formed with the other smokemeters in the project.
1. Description
The smokemeter sensor unit consists of a six-in OD pipe fitted
inside an eight-in OD pipe (Figure 57). Both pipes have one-eighth in
wall thickness, and there is approximately seven-eighths in clearance
between them. The inner pipe is 15-in long and the outer pipe is 13-in
long. A flange is welded to each end of the inner pipe and matching
flanges are welded to the exhaust pipes entering and exiting the smoke-
meter. A split-ring clamp holds the two flanges together. There was
no apparent leakage of exhaust from between the flanges.
The optical system of the inline smokemeter is similar, if not
identical, to that of the manufacturer's end-of-stack instrument. The
light source is a solid-state emitter operating at a frequency of 1000
Hz. The detector is a solid-state photodiode. The optics are contained
in two phenolic modules that screw into the two finned collimating
tubes. Cleaning the optical lenses is accomplished by removing these
optical modules from the collimating tubes (Figure 58). The colli-
mating tubes screw into the outer pipe of the smokemeter and fit securely
against the inner pipe, thus forming a closed, leak-proof system
(Figure 59).
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86
Figure 57. Atlantic Research
Inline Smokemeter (End View)
Figure 58. Collimating Tube
and Screw-In Optical Module
Figure 59. Screw-In Collimating
Tube and Inline Smokemeter
(Side View)
Figure 60. Inline Smokemeter
and Control-Readout Box
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87.
The smokemeter uses about 2. 5 SCFM of compressed air at
about 30 psi to purge the collimating tubes of exhaust. Part of this
air is diverted into the space between the inner and outer pipes to
cool the unit and hence combat thermal distortion of the optical system.
The optical lenses were found to be clean even after extended full-load
engine operation, and baseline drift was nil.
The control-readout box (Figure 60) contains an on-off switch,
"zero" and "full-scale" adjustments, selector switch for either con-
tinuous or peak opacity readings, another selector switch for either
0-20 percent opacity or 0-100 percent opacity ranges, and opacity
meter. An external output jack provides a nominal 100-millivolt signal
for a strip chart recorder. A heavy-duty shielded cable joins the sen-
sor head and the control-readout box.
2. Results of Smokemeter Bench Tests
The data for the bench tests of the Atlantic Research inline
smokemeter are presented below. The data for the same series of
tests with the PHS end-of-stack instrument are reproduced from
Section III to allow direct comparison of the two instruments' per-
formance.
a. Static Filter Calibration Test
The results of the filter calibration of the PHS and AR inline
smokemeters are given in Tables 18 and 19, respectively. The accu-
racy of the PHS instrument is readily apparent from this data. The
Atlantic Research smokemeter had more meter error than the PHS,
and this error ranged from 0. 5- to 5. 0- percent opacity high. Figure
61 shows the meter reading and error as functions of filter opacity.
Smokemeter output ranged from 103 millivolts at zero opacity to three
millivolts at 100-percent opacity. The observed output and linearity
error for the AR instrument are shown in Figure 62.
b. Zero Drift
The zero, or baseline, drift was measured over a one-hour
period. The data appears below.
Elapsed Time, Zero Drift, % of Chart
Minutes
5
10
15
20
30
45
60
Maximum Drift
PHS
0
+0. 2
+0. 2
+0. 2
+0. 2
+0.3
+0. 3
+0.3
A. R. Inline
0
0
+0. 1
+0. 1
+0. 2
+ 0. 2
+0.3
+0. 3
-------
88.
TABLE 18. CALIBRATION DATA FOR PHS
(END-OF-STACK)
SMOKEMETER
OF
Filter Value.
% Opacity
0
100
15. 5
22. 5
37. 5
49. 5
61.0
73. 0
86.0
Opaque
Clear
oM
Meter Value,
% Opacity
0*
100*
15.3
23.0
38.3
50.0
62.0
74. 0
86.4
100.0
0
EM
Meter Error,
% Opacity
0
0
-0.2
+0.5
+0.8
+0. 5
+ 1.0
+ 1.0
+0.4
0
0
VM
Observed
Millivolts
10.0 (=Vc)
0 <=Vo)
8. 47
7. 70
6. 17
5. 00
3.80
2.60
1. 36
0
10.0
VF
Theoretical
Millivolts
10.0
0
8.45
7.75
6.25
5.05
3.90
2.70
1.40
0
10.0
EL
Linearity
Error. %
0
0
+0. 2
-0. 5
-0.8
-0. 5
-1.0
-1.0
-0.4
0
0
*Meter adjusted to these values.
TABLE 19. CALIBRATION DATA FOR ATLANTIC RESEARCH
MODEL 103 INLINE SMOKEMETER
OF
Filter Value,
% Opacity
0
100
15. 5
22. 5
37. 5
49. 5
61.0
73.0
86. 0
Opaque
Clear
OM
Meter Value,
% Opacity
0*
100*
-
23. 5
40.0
50.0
66.0
74.0
89.0
100
0
EM
Meter Error,
% Opacity
0
0
.
+ 1.0
+ 2. 5
+ 0.5
+ 5.0
+ 1.0
+ 3. 0
0
0
VM
Observed
Millivolts
103.0 ( = Vc)
3.0 (-Vo)
.
78.0
60. 0
54.0
36.0
30.0
15.0
3.0
103.0
VF
Theoretical
Millivolts
103.0
3.0
.
80. 5
65. 5
53. 5
42.0
30.0
17.0
3.0
103.0
EL
Linearity
Error, %
0
0
_
-2. 5
-5. 5
+ 0. 5
-6.0
0
-2.0
0
0
*Meter adjusted to these values.
-------
89.
100 -
:1 Correlation Line
10 20 30 40 50 60 70
Filter Value, % Opacity
80 90
100
10 20 30 40 50 60 70 80 90 100
Filter Value, % Opacity
FIGURE 61. METER READING AND ERROR OF ATLANTIC RESEARCH
INLINE SMOKEMETER
-------
.Theoretical Linear Output
Observed Output
90.
10 20
30 40 50 60 70
Filter Value, % Opacity
80 90 100
10 20 30 40 50 60 70 80 90 100
Filter Value, % Opacity
FIGURE 62. OUTPUT VOLTAGE AND LINEARITY ERROR OF
ATLANTIC RESEARCH INLINE SMOKEMETER
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91
The two instruments had almost identical baseline changes.
At the end of the one-hour period, the full-scale (opaque) settings were
checked, and neither instrument showed any change.
c. Effect of Ambient Light
The effect of ambient light on the Atlantic Research inline
smokemeter is academic, since no light can enter the instrument
when it is installed in an exhaust system. However, an attempt was
made to shine the beam of a 125-watt spotlight into the smokemeter's
optical system. This activity produced no detectable change in the
baseline, half-scale, or full-scale settings of the instrument.
d. Effect of Ambient Temperature
The effect of changes in ambient temperature on the instruments'
zero, half-scale (50-percent opacity) and full-scale settings were
measured as functions of ambient temperature. The temperatures used
in these tests were 75 (baseline), 100, 125, and 150 degrees F. Test
results are given in Table 20. The observed changes in zero and half-
scale readings of the A. R. smokemeter are graphed in Figure 63.
The A. R. showed almost no change in its zero setting when
the ambient temperature was increased from 75°F to 100°F. A slight
upward shift (1.4- percent opacity) was noted at 125°F, and a 3.4-
percent opacity increase noted at 150°F. These changes were approx-
imately one-half those of the PHS instrument at the same temperatures.
The half-scale (50- percent) changes by the A. R. inline were
very slight, the maximum being less than one percent at 150°F. By
contrast, the PHS showed a 4.0- percent opacity increase at this temp-
erature. The PHS smokemeter showed no change in its full-scale
(opaque) setting as the ambient temperature increased. However, the
A. R. had a drop of 3.0- percent opacity at 100°F, and decreases of
1. 5- and 2.0- percent opacity at 125 and 150 degrees, respectively.
e. Time Response
The full-scale response time of the A. R. inline smokemeter
was measured in the same manner as the other smokemeters; i. e. , a
sphere was dropped through the light beam and a photograph taken of
the resulting time-voltage trace displayed on an oscilloscope. The
response times thus obtained are given below, along with the times
for the PHS instrument.
Response Time, sec
Smokemeter 0-100% 100-0%
PHS 0.008 0.008
A. R. Inline 0.007 0.012
-------
92.
TABLE 20. EFFECT OF AMBIENT TEMPERATURE ON
SMOKEMETER ZERO, HALF-SCALE, AND FULL-SCALE SETTINGS
Ambient Zero Change, % Opacity
Temp. , ° F PHS A.R. Inline
75* 0 0
100 +1.0 +0.3
125 +3.0 +1.4
150 +7.0 +3.4
Half-Scale Change, % Opacity
PHS A. R. Inline
75* 0 0
100 +0.2 0
125 +1.3 +0.2
150 +4.0 +0.6
Full-Scale Change, % Opacity
PHS A. R. Inline
75* 0 0
100 0 -3.0
125 0 -1.5
150 0 -2.0
*Baseline temperature.
-------
93.
u
a]
a
O
a
oo
c
nt
A
U
S)
6
5
4
O PHS
D Atlantic Res. Inline
100 125
Temperature, °F
150
u
rt
0
-1
O PHS
D Atlantic Res. Inline
75
100 125
Temperature, ° F
150
FIGURE 63. CHANGES IN ZERO AND HALF-SCALE READINGS
AS A FUNCTION OF AMBIENT TEMPERATURE
-------
94.
Hence, the response times of the A. R. smokemeter are comparable
to those of the PHS instrument.
3. Smoke Tests
The A. R. inline and the PHS smokemeter were next mounted
on the Cummins NH-220 engine for a series of Federal smoke com-
pliance tests. Three, four, and five-in diameter exhaust pipes were
adapted to the inline smokemeter, and the PHS instrument was mounted
at the end of the exhaust system (Figure 64).
The Federal "a" and "b" factors measured by the two smokemeters
are summarized in Table 21 for each pipe diameter. The smoke
factors for the A. R. instrument are given as measured (observed)
and after correction by the Beere-Lambert law to the diameter of the
exhaust pipes entering and exiting the inline instrument. Figure 65
illustrates these data.
TABLE 21. FEDERAL SMOKE TEST DATA
Smokemeter "a" Factor "b" Factor
3-in Pipe
PHS 20.8 30.8
A.R. Inline (observed) 35.4 44.5
A.R. Inline (corrected) 19.6 25.5
4-in Pipe
PHS 22.8 33.6
A.R. Inline (observed) 31.0 37.8
A.R. Inline (corrected) 22.0 27.2
5-in Pipe
PHS 26.6 40.1
A.R. Inline (observed) 27.8. 35.6
A.R. Inline (corrected) 23.8 30.7-
Note that the PHS and observed A. R. data tend to converge
as pipe diameter is increased. The best agreement occurred with
the five-in diameter pipe, and the worst agreement was found with
three-in pipe. The PHS opacity of the "a" and "b" factors increased
with pipe diameter, as was shown in Section IV. The A. R. Inline
instrument, on the other hand, registered lower observed opacity with
increased pipe size. However, the corrected A. R. opacities increased
with pipe diameter.
-------
95
..
FIGURE 64. ATLANTIC RESEARCH INLINE SMOKEMETER
IN CONJUNCTION WITH PHS SMOKEMETER ON
THREE-IN PIPE (TOP) AND FIVE-IN PIPE (BOTTOM)
-------
96,
46
44
42
40
38
36
. 34
>s
u
a)
*
-------
97.
The corrected inline "a" factors agree quite well with the
PHS "a" factors for the three-in and four-in pipes. Less agreement
was obtained in the case of the five-in pipe, but here the observed
opacities were very close. The observed PHS "b" factors and corrected
A. R. "b" factors were closest for three-in pipe and showed the greatest
difference for the five-in pipe. However, in no instance did the "b"
factors generated by the two smokemeters approach to a reasonable
agreement.
B. Evaluation of Wager Smokemeters
Two smokemeters manufactured by the Robert H. Wager Co.
were obtained from the manufacturer and subjected to a brief series
of evaluation tests. At the time of these tests, these smokemeters
were being considered for possible inclusion in the project. Hence,
this series of tests was merely to decide whether these instruments
should be subjected to further tests and evaluation. A representative
of the Wager Company and an EPA representative were present during
all tests involving the smokemeters.
One of these smokemeters, shown in Figures 66, 67 and 68,
was an end-of-line unit built to meet New Jersey specifications.
The other instrument, shown in Figures 69, 70, 71 and 7Z was de-
signed for inline opacity measurement and utilized the same optical
components (light source, focusing lens, and photocell) as the PHS
instrument. This inline unit used purge air to keep the optical system
clean, and a flow of water to cool the photocell and light source.
Both instruments were tested for accuracy using the neutral
density filters previously described. The accuracy of the portable
Wager unit was good and that of the inline instrument was excellent.
The portable instrument showed a slight sensitivity to ambient light,
while the inline unit showed none. There was insufficient time avail-
able to perform the tests for zero drift and effect of ambient temper-
ature.
The two smokemeters were next tested on the Cummins NH-220
engine. Under steady-state smoke conditions, the portable smokemeter
experienced a build-up of smoke deposit on the optical lens after about
30 to 60 seconds of operation. When the engine was shut down, the
instrument continued to read about 4- to 6- percent opacity. The meter
reading returned to zero only when the optical surfaces were cleaned;
hence, it was concluded that the problem was one of carbon build-up
and not of temperature effects. The smokemeter was operated in
both continuous reading and peak reading modes. In the continuous
reading mode the meter read some 6- to 8- percent opacity lower
than the PHS instrument under similar conditions. When the peak
-------
98
NO
ADMITTANCE
APPLV AT
OFFICE
FIGURE 66. WAGER PORTABLE
SMOKEMETER AND READOUT
UNIT
FIGURE 67. WAGER SMOKEMETER
MOUNTED ON EXHAUST STACK
FIGURE 68. WAGER SMOKEMETER
MOUNTED ON EXHAUST STACK
FIGURE 69. WAGER INLINE
SMOKEMETER
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99
FIGURE 70. WAGER INLINE
SMOKEMETER WITH
CONTROL BOX
NO
ADMITTANCE
FIGURE 71. WAGER INLINE
SMOKEMETER MOUNTED
IN EXHAUST LINE
FIGURE 72. WAGER INLINE
SMOKEMETER IN
CONJUNCTION
WITH PHS
SMOKEMETER
-------
100.
reading mode was used, the reading obtained was substantially higher
than the continuous reading and similar to the PHS smokemeter reading.
The Wager representative concluded that the continuous reading cir-
cuitry required some revision to equalize the sensitivity in the con-
tinuous and peak reading modes.
The inline Wager instrument was installed in the exhaust line
of the Cummins NH-220 and the PHS smokemeter attached to the end
of the line (Figure 72). After about one minute of steady-state oper-
ation, the inline smokemeter registered 100- percent opacity, and
this reading persisted even when the engine was shut down. Examin-
ation revealed that the optical surfaces were covered with carbon
build-up. It was evident that the purge air system and instrument
design were not adequate to keep the optical surfaces clean.
Since both smokemeters experienced problems during these
preliminary tests, and since both instruments were in the prototype
category, the Wager representative asked that the instruments be
returned to the manufacturer. The Project Officer, when advised of
the results of these tests, decided that both Wager smokemeters should
not undergo further evaluation.
-------
101.
VI. DEVELOPMENT OF A PHS INLINE SMOKEMETER AND
COMPARISON OF INLINE AND END-OF-LINE OPACITY MEASUREMENT
Recent effort in the development of diesel smoke measurement
devices has been directed, in part, toward inline-type smokemeters. As
mentioned previously, at least one company (Atlantic Research) is marketing
an inline instrument, and it seems likely that other companies will follow
suit. Inline smokemeters enjoy two particular advantages over end-of-line
instruments; namely, an inline smokemeter can be permanently mounted in
a test cell installation, and the resulting closed exhaust system does not
allow exhaust gases into the cell. These two features make inline smoke-
meters attractive to many research and testing groups.
However, inline opacity measurement is obviously based on physical
conditions quite different from those of end-of-line measurement. For
instance, the exhaust gases in the pipe are subject to different turbulences,
pulsations, flow rates, and temperatures than the gases exiting the pipe.
The effect of these differences on indicated opacity obtained in the line and
at the end of the line is not fully known. The work in this section was a
preliminary research effort in the correlation of inline and end-of-line
sampling techniques. Also, under terms of this project contract, an iden-
tical inline smokemeter was constructed by SwRI and furnished to EPA for
further tests and evaluation.
A. Design Criteria of the PHS Inline Smokemeter
The primary objective of this part of the project was to compare the
opacity readings obtained with in-the-line and end-of-line sampling techniques.
Hence, an inline smokemeter that correlated with the standard PHS end-of-
line smokemeter was needed, and considerable effort was directed towards
the development of such an inline instrument. The approach to this develop-
ment work was to retain,as much as possible, the basic components (e. g. ,
optical system, collimating tubes, and control-readout box) of the standard
PHS smokemeter.
The criteria that the inline smokemeter design had to meet are the
following. First, the inline instrument must have calibration accuracy (with
neutral density filters) that is equal to, or better than the PHS end-of-line
smokemeter. Second, the time response of the inline must be fast enough to
follow rapid changes in smoke opacity. Third, the inline must not exhibit
excessive (more than two percent) baseline drift after extended full-power
engine operation, with the accompanying high exhaust flow rate and tempera-
ture. The first two criteria were not difficult to meet, as all of the inline
models developed used the same optical system (lamp, lens, and photocell)
and electrical circuitry (i. e. , readout box) as the standard PHS instrument.
Hence, all inline models tested showed the excellent calibration accuracy and
response characteristics of the end-of-line unit. It was meeting the third
-------
102.
criterion - - holding baseline drift to less than two percent of scale - - that
caused most of the difficulty in developing the inline PHS smokemeter.
Baseline drift is usually caused by misalignment of the optical system
(due to thermal distortion of the unit) and/or by the accumulation of carbon
particles on the lens and photocell. In an effort to prevent these two undesir-
able effects, several inline designs were tested, with varying degrees of
success, before the final design was developed. All of the inline models tested
will be briefly described next.
B. Development of the Inline Smokemeter
The original inline model consisted of a 3-foot length of 4-inch diameter
steel tubing with mounting pads for the collimating tubes (Figure 73). There
was a 3/8-inch air gap between the collimating tubes and the main pipe. The
purpose of the air gap was to partially damp out the severe pulsations in the
exhaust flow of the Cummins NH-220 engine. However, the large (2-1/4 inch)
holes in the central pipe allowed the exhaust gases to penetrate into the colli-
mating tubes and hence coat the optical surfaces (lens and photocell) •with a
carbon deposit. The flow of purge air "was increased to keep the optical sur-
faces clean, but the problem persisted. There was also considerable leakage
of exhaust through the air gap and into the test cell.
The first modification consisted of covering the large holes in the
four-in pipe with thin metal plates drilled with three-eighth in diameter holes
for the light beam to pass through. These smaller holes reduced the maximum
amount of light reaching the photocell and, hence, reduced the maximum photo-
cell output. The output circuit in the readout-control box was modified by
reducing its resistance. This increased the maximum output voltage to 10MV
and thus permitted use of a standard strip chart recorder with 10MV span.
A schematic of the modified output circuit is included as part of Appendix
The smaller light beam holes reduced the exhaust leakage into the
test cell, but the exhaust pulsations still filled the collimating tubes and
again coated the optical surfaces with carbon build-up. The next step was to
fit a metal plate, drilled with a 1/4-inch light beam hole, into the end of each
collimating tube. Carbon build-up on the optical surfaces was still present,
though considerably reduced. However, the smokemeter experienced heat
distortion that caused misalignment of the small light beam holes. This
misalignment caused the light beam to strike the edge of the hole in the exhaust
pipe and resulted in opacity readings about twice those of the end-of-line
smokemeter.
To minimize heat distortion of the inline unit, the 4-inch steel pipe
was replaced with a 15-inch length of 4-inch aluminum pipe with 1/4-inch wall
thickness (Figure 74). The light beam hole remained at 3/8 inch, and the air
gap between pipe and collimating tubes was decreased to 3/16 inch. Heat
distortion was less with this configuration, but still caused the smokemeter
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103
FIGURE 73. INITIAL PHS INLINE SMOKEMETER PIPE
WITH MOUNTING FLANGE SHOWN
FIGURE 74. ALUMINUM INLINE
SMOKEMETER PIPE-1/2-INCH
LIGHT BEAM HOLE
FIGURE 75. DUAL PIPE INLINE
SMOKEMETER-SIDE VIEW
-------
104.
to read 10 to 15-percent opacity higher than the end-of-line instrument. Carbon
build-up on the lens surface also contributed to these higher readings. To
further reduce the effect of heat distortion, the holes in the aluminum pipe
were drilled out to 1/2-inch. This step greatly reduced the effect of distor-
tion, and the inline smokemeter registered about two-percent opacity higher
than the end-of-line smokemeter. However, after about two minutes of full-
load engine operation, the lens in the inline unit again became covered with
carbon. The air gap was increased from 3/16-inch to 3/4-inch in hopes the
exhaust would not penetrate into the collimating tubes. This was not success-
ful, however, and it was decided to try a different inline design.
The next model consisted of a 4-inch aluminum pipe, identical to that
described in the preceding paragraph, fitted inside a 5-inch aluminum pipe
drilled with 1/2-inch light beam holes (Figures 75 and 76). There was,
therefore, a 1/2-inch gap between the two pipes. This arrangement was to
reduce heat transfer from the inner pipe to the outer, and hence to minimize
heat distortion. Also, it was hoped the gap between the two pipes would help
to damp out exhaust pulsations and hence prevent the exhaust from entering
the collimating tubes. However, the performance of this model was worse
than the preceding design. Opacity readings from this inline instrument were
almost double those of the end-of-line unit, and carbon build-up on the lens
was quite severe.
The next inline design consisted of a length of 4-inch diameter steel
tubing drilled with 3/8-inch light beam holes and fitted into an aluminum
bracket. A frame ring from the PHS end-of-line smokemeter was attached
to this bracket and the collimating tubes were mounted on the ring in the
usual manner (Figures 77 and 78). It was thought that this design would, by
removing the collimating tubes from the immediate vicinity of the exhaust
pipe, lessen the amount of exhaust entering the tubes and also minimize heat
distortion. These objectives were accomplished in large measure, as the
inline smokemeter read only about two-percent opacity higher than the end-
of-line unit. The two smokemeters followed opacity changes during transient
operation in a similar and consistent manner.
This inline configuration showed a slight (2-'..o 3-percent opacity) up-
ward zero change after several minutes of full-load engine operation. This
zero change was thought to be caused by a slight carbon build-up on the lens.
Therefore, a small air jet made from 1/4-inch copper tubing was installed
on each side of the exhaust pipe, at the rear of the light beam hole (Figure
79). The air from the jets was directed across these holes, at right angles
to the escaping exhaust flow. It was thought the air jet -would diffuse the
exhaust flow as it left the pipe and thus keep it out of the collimating tubes.
However, the zero change continued as before, and it was concluded that
thermal distortion of the smokemeter frame was to blame. In addition, the
opacity readings were sensitive to the amount of purge flowing through the
external air jets. That is, if the air flow from these jets was "correct" for
-------
105
FIGURE 76. DUAL PIPE INLINE
SMOKEMETER-END VIEW
FIGURE 77. ADVANCED DESIGN
PHS INLINE SMOKEMETER
FIGURE 78. ADVANCED DESIGN
PHS INLINE SMOKEMETER
FIGURE 79. AIR JETS ON INLINE
SMOKEMETER
-------
106.
a certain engine speed and load condition, the same air rate was not
necessarily suitable for another engine condition, and indicated smoke
opacity might be completely erroneous. No one air rate was found
suitable for all engine conditions and opacity levels.
The next inline model represented a substantial departure from
previous designs. Small metal tubes, approximately three in long by three-
eights in ID, were welded to the light beam holes in the central exhaust
pipe. The outer end of each tube was sealed with a small disc of clear
glass epoxyed to the tube. Thus, the effect of this design change was to
create a closed system. Purge air was admitted to each sealed tube by
means of a one-quarter in OD copper tube inserted just ahead of the glass
window.
This instrument was tested on a truck-tractor powered by a Cum-
mins NHC-250 engine. The vehicle was operated on a chassis dynamometer.
No exhaust leakage occurred under any test condition, and the glass "windows"
remained clean with a purge air rate of three to four SCFM. No purge air
was routed to the collimating tubes. These preliminary tests showed a
substantial improvement over those of the previous inline design. However,
a small amount of baseline change still existed. The inline smokemeter
also tended to read progressively higher opacity (under steady-state con-
ditions) with elapsed time.
It was thought that both of these anomalies were due to thermal
distortion effects. Therefore, the next step was to construct the central
four-in diameter exhaust pipe and the mounting bracket from stainless steel.
The stainless steel components have less differential thermal expansion
than the original components. Other improvements made at this time in-
cluded replacement of the small sealed optical tubes with stainless versions,
replacement of the epoxyed glass "windows" with screw-on caps containing
the glass, and routing a small flow of purge air to the collimating tubes.
This purge air served to keep the collimating tubes clear of any exhaust
smoke that happened to recirculate in the vicinity of the smokemeter. This
model of the inline instrument is shown in several views in Figure 80, and
a schematic drawing of one of the sealed optical tubes is shown in Figure
81. General operating instructions for the inline smokemeter are contained
in Appendix C.
In preliminary tests, this inline had approximately ± 1. 0-percent
opacity baseline change after extended running on the stationary NH-220
engine. This was considerably less change than previous inline models
had shown, but was somewhat more than the typical PHS end-of-line
demonstrates under similar conditions. The opacity traces from the two
instruments showed the same general trends; i. e. , when one smokemeter
registered an increase (decrease) in smoke opacity, the other unit registered
a similar increase (decrease). Also, the two smokemeters produced traces
-------
107.
FIGURE 80. FINAL DESIGN OF THE PHS INLINE SMOKEMETER
-------
— 1/4" Stainless Steel Tubing (for purge air)
Brass Plug w/3/4
NC Thread
tN
2-7/8"-
1.0" OD Stainless Steel Round Stock
^— 1/16" Viton Gaskets Stainless Steel. Sen. 40, 1/4" ID Pipe
(Reamed or Drilled to 3/8" ID)
FIGURE 81. SCHEMATIC DRAWING OF SEALED OPTICAL TUBE
FROM PHS INLINE SMOKEMETER
o
00
-------
109.
of similar shape and duration for engine accelerations. In general, the
opacity trace for the inline was slightly smoother, with less "hash", than
the end-of-line trace. This difference was apparently due to less variation
in exhaust flow passing through the inline than for the plume passing through
the end-of-line instrument.
This final version of the inline smokemeter was tested on naturally
aspirated Cummins NHC-250 and V-903 engines, and also on a turbocharged
Mack ENDT 673B engine. These engines provided a wide range of smoke
opacities, exhaust temperatures, and flow rates. The test procedure used
was the simulated Federal smoke test. The "a" and "b" factors for these
tests are given in Table 22, below.
TABLE 22. FEDERAL "a" AND "b" FACTORS BY
INLINE AND END-OF-LINE OPACITY MEASUREMENT
Engine
Cummins
Cummins
Mack ENDT 673B
"a" Factors, % Opacity "b" Factors, % Opacity
E.O.L. Inline E.O.L. Inline
24.2
18.3
14.8
23.9
15.2
11.5
33.2
21. 7
8.3
31.3
17.4
6.3
From Table 22, it can be seen that the inline instrument read two-
to five-percent opacity lower than the end-of-line smokemeter in all of the
tests. The best agreement between the two smokemeters occurred in the
case of the Cummins NHC-250 engine. Slightly less agreement was obtained
in the tests with the Cummins V-903 engine, and the two smokemeters
showed the least correlation for the turbocharged Mack engine. In particular,
the "b" factors for the V-903 engine were considerably different, as were
the "a" factors of the 673B engine. Three opacity traces from these smoke
tests are shown in Figures 82, 83, and 84. One figure is included for each
of the three trucks used for the tests. The smoke trace evaluation sheets
for these tests are contained in Appendix D. These sheets contain the indi-
vidual opacity readings for each test sequence.
The fact that the inline smokemeter registered lower smoke opacity
than the end-of-stack unit was not necessarily a discrepancy in the inline
instrument itself, since there was no a prior reason why the two instru-
ments should register the same opacity. What was judged important was that
this inline model (1) calibrated with neutral density filters to a high degree
of accuracy; (2) had response fast enough to follow transient smoke conditions;
and (3) had an acceptable amount of baseline change after extended running
time. In view of these facts, it was decided to proceed -with the study of
effect of exhaust variables on inline vs end-of-line sampling methods using
this inline smokemeter.
-------
FIGURE 82. OPACITY TRACES FOR FEDERAL SMOKE TEST WITH PHS INLINE AND
END-CfF-LINE SMOKEMETERS - CUMMINS NHC-250 ENGINE
-------
FIGURE 83. OPACITY TRACES FOR FEDERAL SMOKE TEST WITH PHS INLINE AND
END-OF-LINE SMOKEMETERS - CUMMINS V-903 ENGINE
-------
FIGURE 84. OPACITY TRACER FOR FEDERAL SMOKE TEST WITH PHS INLINE AND
END-OF-LINE SMOKEMETERS - MACK ENDT 673B ENGINE
-------
113.
C. Effect of Exhaust Variables On Inline and End-of-Line
Opacity Measurement
The stationary-mounted Cummins NH-220 engine was selected as the
smoke generator for this phase of the inline study because of its highly
pulsating flow and high exhaust temperatures. The inline and end-of-line
smokemeters were placed in series in the exhaust system of the engine,
with approximately three ft of pipe between them (Figure 85). A thermo-
couple was used to measure exhaust temperature at a point about one ft
upstream from the inline instrument. The engine's intake system was
partially restricted to increase the range of smoke opacities, and a nominal
opacity level of some 60 percent was the highest thus obtained.
The test sequence consisted of a series of steady-state engine con-
ditions at engine speeds of 600 rpm (low idle), 1500, 1800, and 2100 rpm.
Engine loads at each speed were zero, full, and approximately one-third
and two-thirds of full load. Three such sequences were performed in the
study. The first and third sequences went from 1500 rpm and zero load to
2100 rpm and full load, in an increasing manner. The second sequence went
from 2100 rpm and full load to 1500 rpm and zero load, in a decreasing
manner. Two idle conditions were included in each test sequence, one
between 1500 and 1800 rpm and the other between 1800 and 2100 rpm. For
the first and third sequences, the idle conditions are "hot", since they
follow full load at 1500 and 1800 rpm. The idle conditions for the second
test sequence are "cold", since they follow zero load at 2100 and 1800 rpm.
The average data for the three test sequences are presented in Table
23. The data include the estimated exhaust flow rate (in cubic ft per min at
line temperature and pressure) through the smokemeters and exhaust temper-
ature at the inline instrument for each test condition, as well as the opacities
registered by the two smokemeters. The absolute difference between the
opacity readings of the two smokemeters is given in Table 23 in the column
headed "Diff. ".
The data in the table reveal that the inline and end-of-line instruments
read within 1. 0-percent opacity in a majority of the test conditions. At full
engine load at 1500 and 2100 rpm, the end-of-stack smokemeter read 4. 0-
and 1.8-percent opacity higher, respectively, than the inline. However, at
full power at 1800 rpm, the inline instrument read 0.5-percent opacity higher
than the end-of-line. The maximum deviation at 1800 rpm was 3. 0-percent
opacity at one-third and two-thirds of full load. It is not known why the
readings differed most at these part-load conditions rather than at full load.
The opacity readings at 1800 rpm were also unusual in that the inline read
higher than the end-of-line at all four conditions. Again, the cause is not
known, although it is possible that a peculiar resonance condition existed in
the exhaust pipe at 1800 rpm and caused the inline smokemeter to register
higher opacities. The problem of determining resonance conditions in the
-------
114.
FIGURE 85. INLINE AND END-OF-LINE
SMOKEMETERS ON TEST STAND
-------
115.
TABLE 23. COMPARISON OF INLINE AND END-OF-LINE OPACITY
READINGS UNDER STEADY-STATE SMOKE CONDITIONS
Engine
RPM
1500
n
n
"
1800
"
"
"
2100
ii
11
it
600*
"*#
Engine
Load
0
1/3
2/3
Full
0
1/3
2/3
Full
0
1/3
2/3
Full
0
0
Exhaust Flow
Rate, ACFM
364
566
688
734
478
680
802
930
544
716
921
956
192
174
Nominal Exhaust
Temp., °F
360
815
1090
1195
440
820
1050
1290
565
890
1275
1340
330
260
Smoke
E.O.L.
2.7
11.2
32.0
50. 7
3.2
10.5
23.0
46. 0
4. 7
13.7
30.7
59.3
3.0
2.0
Opacity, '
Inline
2.5
12.2
31.2
46. 7
4.1
13.5
26.0
46.5
5.0
12.8
30.3
57.5
2.4
1.5
%
Diff.
0.2
1.0
0.8
4.0
0.9
3.0
3.0
0.5
0.3
0.9
0.4
1.8
0.6
0.5
Average Difference 1. 3
*Hot idle following full load.
>-*Cold idle following zero load.
-------
116.
4.0
3.0
2.0
g 1.0
:/}
0
s£
•t
>*
4->
• H
U
O
0)
o
2100 rpm
300 400 500 600 700 800 900 1000
Exhaust Flow, ACFM
FIGURE 86. ABSOLUTE DIFFERENCE BETWEEN PHS
INLINE AND END-OF-LINE OPACITY READINGS
AS A FUNCTION OF EXHAUST FLOW RATE
4.0
.3.0
>*
•u
• l-l
O
a 2.0
O
0)
91.0
1500 rpm
0L
1800 rpm
2100 rpm
300 400 500 600 700 800 900 1000 1000 1200 1300 1400
Exhaust Temperature, °F
FIGURE 87. ABSOLUTE DIFFERENCE BETWEEN PHS
INLINE AND END-OF-LINE OPACITY READINGS
AS A FUNCTION OF EXHAUST TEMPERATURE
-------
117.
pipe and their effect on opacity measurement is extremely complex and
certainly beyond the scope of this project. However, there is little doubt
that such conditions do influence the readings of the inline instrument.
The two smokemeters produced opacity readings within 1.0-percent
opacity during both "hot" and "cold" idles. However, the opacities were
slightly higher for the "hot" idle. Whether the "hot" exhaust is actually
of higher opacity than the "cold" exhaust, or whether the higher temperature
is producing a thermal effect in the two smokemeters, is not known.
The absolute difference (in percent opacity) in the readings of the
two instruments is graphed as a function of exhaust volumetric flow rate
and exhaust temperature in Figures 86 and 87, respectively. Since the
volumetric flow rate is, for a given engine speed, a function of the exhaust
temperature, the two figures differ only in the scale of their respective
abscissas. The four data points for each engine speed that are shown in
these figures are, of course, the four load points of the engine at each
speed, with the zero-load points appearing at the far left of the figures and
the full-load points at the far right.
Figures 86 and 87 reflect the previous discussion of the data in
Table 23. That is, the opacity readings of the two smokemeters tend to
diverge when going from zero load to one-third load, then tend to converge
or maintain the same agreement between one-third and two-thirds of full
load. The difference in the two opacity readings increases sharply at full
load at 1500 and 2100 rpm, and decreases sharply at 1800 rpm and full
load. Although the behavior of the two smokemeters is inconsistent in this
regard, it can at least be said that the full-load conditions, with their
accompanying high flow rates and high temperatures, produce the most
drastic changes in the instruments' opacity readings. However, the agree-
ment between the two smokemeters is, on the average, quite good.
-------
118.
VII. SUMMARY AND CONCLUSIONS
This project has covered several areas of interest in the measure-
ment of diesel smoke opacity. Several smoke test procedures, intended for
in-use vehicle inspections, were compared to a chassis dynamometer version
of the Federal smoke compliance test. Several commercially-available
smokemeters had their performance compared to that of the standard PHS
end-of-line smokemeter. Special topics that were investigated were the
comparison of opacity measurements from three identical PHS smoke-
meters and the correlation of the standard 10-in diameter PHS smokemeter
with enlarged versions of 20-in and 40-in diameter. Finally, an inline
version of the PHS smokemeter was developed at SwRI for this project.
Inline and end-of-line opacity measurements were made simultaneously
in order to determine the correlation between the two measurement tech-
niques and also to determine the effect of certain exhaust variables, such
as flow rate and temperature, on this correlation.
The following conclusions were drawn from the results of the items
of work mentioned above:
(1) None of the smoke test procedures correlated well with the
simulated Federal smoke test for all engine/vehicle combinations used in
the evaluation study. The experimental SwRI procedure came closest to
duplicating the results of the simulated Federal test in the largest number
of cases, while the New Jersey truck and bus procedures in general showed
poor correlation with the Federal test. However, the New Jersey procedures
appear to be related to regular in-service operation of diesel-powered trucks
and buses, and thus fulfill a principal requirement for an inspection-type
test procedure.
(2) Based on the results, of the bench tests, the Atlantic Research
smokemeter performed best, while the results of the various smoke tests
indicate the Bacharach and Atlantic Research were approximately equal in
their performance. In all cases the Nebetco instrument was far behind.
Neither the Atlantic Research or Bacharach correlated with the PHS smoke-
meter in all the smoke tests performed.
(3) Use of three typical PHS smokemeters in a series of smoke tests
showed that excellent correlation existed between the three instruments.
These tests also confirmed that pipe diameter has a definite effect on indicated
smoke opacity; i.e., the larger the diameter, the higher the opacity registered
by the smokemeter. However, the Beere-Lambert law was quite effective in
correlating the measured opacities for the various pipe diameters.
(4) The special enlarged versions of the PHS smokemeter, of 20- and
40-in diameter, produced nominal opacity readings that were very close to
those of the standard ten-in diameter instrument. Thus, the increased light
-------
119.
beam path length of the enlarged smokemeters had little or no effect on
indicated smoke opacity, at least for this series of tests using three-in
and four-in diameter pipe. However, the amount of "hash" in the opacity
traces increased substantially with the larger diameter instruments.
(5) The Atlantic Research inline smokemeter produced substantially
different opacity readings from the PHS end-of-line instrument. The amount
of this difference decreased as the exhaust pipe diameter was increased from
three in to four in to five in. Correction of opacities from one pipe size to
another by means of the Beere-Lambert law was only partially successful.
(6) The PHS inline smokemeter designed and constructed in the
course of this project displayed a reasonable degree of correlation with the
PHS end-of-line smokemeter during steady-state smoke tests. However,
the correlation between the two instruments during simulated Federal smoke
tests with three truck-tractors was inconsistent, showing good agreement
in some instances and poor agreement in others. In either case, the PHS
inline read much closer to the standard PHS smokemeter than did the
Atlantic Research inline instrument.
(7) The steady-state smoke tests performed with the inline and end-
of-line PHS smokemeters on a Cummins NH-220 engine showed that varying
exhaust flow rates and temperatures produced different changes in the two
instruments' opacity readings, causing them to converge in some cases and
to diverge in others. However, in most instances this observed convergence
or divergence was of small magnitude.
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120.
LIST OF REFERENCES
1. Springer, KarlJ., "An Investigation of Diesel-Powered Vehicle
Odor and Smoke - Part I, " Final Report to the U.S. Public Health
Service, Contract PH 86-66-93, March, 1967.
2. Springer, Karl J. , "An Investigation of Diesel-Powered Vehicle
Odor and Smoke - Part II, " Final Report to the U.S. Public Health
Service, Contract PH 86-67-72, February, 1968.
3. Springer, Karl J. , "An Investigation of Diesel-Powered Vehicle
Odor and Smoke - Part III, " Final Report to the U.S. Public Health
Service, Contract PH 22-68-23, October, 1969.
4. Springer, Karl J. and Dietzmann, Harry E, , "An Investigation of
Diesel-Powered Vehicle Odor and Smoke - Part IV, " Final Report
to the Environmental Protection Agency, Contract PH 22-68-23,
April 1971.
5. Pinkert, Daniel, "Neutral Density Filters for Use in Calibrating
the PHS Smokemeter, "U.S. Public Health Service, March 19, 1969.
6. "Revised Preliminary Operating Instructions for Use of the U. S.
Public Health Service Full-Flow Light-Extinction Smokemeter, "
June 1970.
7. Federal Register, Volume 33, No. 108, June 4, 1968.
8. Federal Register, Volume 35, No. 219, November 10, 1970.
9. Springer, KarlJ. and Ludwig, Allen C. , "Documentation of the
Guide to Good Practice for Minimum Odor and Smoke from Diesel-
Powered Vehicles, " Final Report, Contract CPA 22-69-71,
November 1969.
10. New Jersey Department of Environmental Protection, "Air
Pollution Control Code," Chapter 14.
11. Storment, JohnO. and Springer, KarlJ., Interim Report on
"A Surveillance Study of Smoke From Heavy-Duty Diesel-
Powered Vehicles -- Southwestern U.S.A. , " Final Report to
the Environmental Protection Agency, Contract EHS 70-109,
September, 1972.
-------
A PPENDIX A
FEDERAL SMOKE TEST PROCEDURE
(FEDERAL REGISTER, VOL. 35, NO. 219, NOV. 10, 1970)
-------
A-2,
FEDERAL
REGISTER
VOLUME 35 • NUMBER 219
Tuesday, November 10, 1970 • Washington, D.C.
PART II
Department of Health,
Education, and Welfare
Office of the Secretary
•
Control of Air Pollution From New
Motor Vehicles and New Motor
Vehicle Engines
Mo. 218—Pt. H-
-------
Subparl J—Test Procedures for En-
gine Exhaust Emissions (Heavy Duly
Diesel Engines)
§85.120 Introduction.
(a) The procedures described in this
subpart will be the test program to deter-
mine the conformity of heavy duty diesel
engines with the applicable standards set
forth in this part:
(b) The test consists of a prescribed
sequence of engine operating conditions
on an engine dynamometer with con-
tinuous examination of the exhaust gases.
The test is applicable equally to con-
trolled engines equipped with means for
preventing, controlling, or eliminating
smoke emissions and to uncontrolled
engines.
(c) The test is designed to determine
the opacity of smoke in exhaust emis-
sions during those engine operating con-
ditions which tend to promote smoke
from diesel-powered vehicles.
(d) The test procedure begins with a
warm engine which is then run through
preloading and preconditioning opera-
tions. After an idling period, the engine is
operated through acceleration and lug-
ging modes during which smoke emission
measurements are made to compare with
the standards. The engine is then re-
turned to the idle condition and the ac-
celeration and lugging modes are re-
peated. Three sequences of acceleration
and lugging constitute the full set of
operating conditions for smoke emission
measurement.
§ 85.121 Diesel fuel specifications.
(a) The diesel fuels employed shall be
clean and bright, with pour and cloud
points adequate for operability. The fuels
may contain nonmetallic additives as
follows: cetane improver, metal deacti-
vator, antioxidant, dehazer, antlrust,
pour depressant, dye, and dispersant.
(b) Fuel meeting the following specifi-
cations, or substantially equivalent speci-
fications approved by the Secretary, shall
be used in exhaust emission testing. The
grade of fuel recommended by the engine
manufacturer, commercially designated
as "Type 1-D" or "Type 2-D", shall be
used.
Item
Cetane
Distillation range
IBP °F
10 percent point, °F
60 percent point, °F. . ....
90 percent point, °f
Gravity "API .. .
Total sulfur, percent
Flash point °F (Min )
Viscosity centistokes
ASTM test method No.
D 613
D 80
D 287 .
D 129 or D 2622
D 1319
D 93
D 445
Type 1-D
48-54
330-3911
37CM30
410-480
460-520
600-560
40-44
0. 05-0. 20
8-15
. Remainder
120
1. 8-2. 0
Type2-D
42-50
340-400
400-460
470-640
550-610
580-460
33-37
0.2-0.5
27 (Min.)
Remainder
130
Z 0-3.2
(c) Fuel meeting the following specifications, or substantially equivalent specifi-
cations approved by the Secretary, shall be used in service accumulation. The grade
of fuel recommended by the engine manufacturer, commercially designated as
"Type 1-D" or "Type 2-D", shall be used.
Item ASTM test method No. Type 1-D Type 2-D
Cetane D 613 48-54 42-55
Distillation range D 86
1BP,°K 330-390 340-410
10 percent point, °F 370-430 400-470
SO percent point, °F 410-480 470-540
80 percent point, °F 460-520 S50-610
EP °F 500-560 igO-660
Gravity,'API D 287 40-44 33-40
Total sulfur, percent D 129 or D 2622 0.05-0.20 0.2-0.5
Flash point, ff (Min.) D 93 120 130
Viscosity, centistokes D 445 l.e-2.0 2.0-3.2
(d) The type fuel, including additive
and other specifications, used under
paragraphs (b) and (c) of this section
shall be reported in accordance with
§ 85.51(b)(3).
§ 85.122 Dynamometer operation cycle
for smoke emission tests.
(a) The following sequence of opera-
tions shall be performed during engine
dynamometer testing of smoke emissions,
starting with the dynamometer preload-
ing determined and the engine precondi-
tioned (§85.127(0).
(1) Idle mode. The engine is caused
to idle for 5 to 5.5 minutes at the manu-
facturer's recommended low idle speed.
The dynamometer controls shall be set to
provide minimum load by turning the
load switch to the "off" position or by
adjusting the controls to the minimum
load position.
(2) Acceleration mode, (i) The engine
speed shall be increased to 200±50 r.pjn.
above the manufacturer's recommended
low idle speed within 3 seconds.
(ii) The engine shall be accelerated at
full-throttle against the inertia of the
engine and dynamometer or alternately
against a preselected dynamometer load
such that the engine speed reaches 85
to 90 percent of rated speed in 5±1.5
seconds.
>
o
o
|
o
«n
FEDERAL REGISTER, VOL. 35, NO. 219—TUESDAY, NOVEMBER 10, 1970
CO
-------
RULES AND REGULATIONS
A-4.
(iii) When the engine reaches the
speed required in subdivision (li) of this
subparagraph. the throttle shall be
moved rapidly to the closed position and
the preselected load required to perform
the acceleration in subdivision (iv) of
this subparagraph shall be applied. The
engine speed shall be reduced to the
speed of maximum rated torque or 60
percent of rated speed (whichever is
higher), with ±50 r.p.m. Smoke emis-
sions during this transitional mode are
not used in determining smoke emissions
to compare with the standard.
(Iv) The throttle shall be moved
rapidly to the full-throttle position and
the engine accelerated against the pre-
selected dynamometer load such that the
engine speed reaches 95 to 100 percent
of rated speed in 10±2 seconds.
(3) Lugging mode. (1) Proceeding
from the acceleration mode, the dyna-
mometer controls shall be adjusted to
permit the engine to develop maximum
horsepower at rated speed. Smoke emis-
sions during this transitional mode are
not used In determining smoke emissions
to compare with the standard.
(11) Without changing the throttle
position, the dynamometer controls shall
be adjusted gradually to slow the engine
to the speed of maximum torque or to
60 percent of rated speed, whichever IB
higher. This engine lugging operation
shall be performed smoothly over a pe-
riod of 35±5 seconds. The rate of slow-
ing of the engine shall be linear, within
±100 r.p.m.
(4) Engine unloading. After comple-
tion of the lugging mode in subparagraph
(3) (ii) of this paragraph, the dynamom-
eter and engine shall be returned to the
idle condition described in subparagraph
(1) of this paragraph.
(b) The procedures described in para-
graph (a) (1) through (4) of this sec-
tion shall be repeated until the entire
cycle has been run three times.
§ 85.123 Dynamometer and engine
equipment.
The following equipment shall be used
for smoke emission testing of engines
on engine dynamometers.
(a) An engine dynamometer with ade-
quate characteristics to perform the test
cycle described in § 85.122.
(b) An engine cooling system having
sufficient capacity to maintain the en-
gine at normal operating temperatures
during conduct of the prescribed engine
tests.
(c) A noninsulated exhaust system ex-
tending 12±2 feet from the exhaust
manifold of the engine and presenting an
exhaust back pressure within ±0.2 inches
Hg of the upper limit at maximum rated
horsepower, as established by the engine
manufacturer In his sales and service
literature for vehicle application. A con-
ventional automotive muffler of a size and
type commonly used with the engine be-
ing tested shall be employed in the ex-
haust system during smoke emission test-
ing. The terminal 2 feet of the exhaust
pipe shall be of circular cross section and
be free of elbows and bends. The end of
the pipe shall be cut off squarely. The
terminal 2 feet of the exhaust pipe shall
have a diameter In accordance with the
engine being tested, as specified below:
Maximum rated Exhaust
horsepower pipe size
Less than 101 2"
101-200 3"
201-300 .- 4"
301 or more 6"
(d) An engine air inlet system pre-
senting an air Inlet restriction within
±l-lnch of water of the upper limit for
the engine operating condition which
results in maximum air flow, as estab-
lished by the engine manufacturer in his
sales and service literature, for the
engine being tested.
§ 85.124 Smoke measurement system.
(a) Schematic drawing. The following
figure (flg. 7) Is a schematic drawing of
the optical system of the light extinction
meter.
COUIMATED LIGHT FROM SOURCE
DETECTOR
1,
JRCE-^jf
-/_-
4-9"
OPTICAL COMPONENT FOR LIMITING
DETECTOR VIEWING ANGLE
LIGHT-SOURCE
• COLLATING LENS
Figure. 7. USPHS smokemeter optical system (schematic).
(b) Equipment. The following equip-
ment shall be used in the system:
(1) Adapter—the smokemeter optical
unit may be mounted on a fixed or mov-
able frame. The normal unrestricted
shape of the exhaust plume shall not be
modified by the adapter, the meter, or
any ventilation system used to remove
the exhaust from the test site.
(2) Smokemeter (light extinction me-
ter) —continuous recording, full-flow
light obscuration meter. It shall be po-
sitioned near the end of the exhaust pipe
so that a built-in light beam traverses
the exhaust smoke plume which issues
from, the pipe at right angles to the
axis of the plume. The light source is an
Incandescent lamp operated at a con-
stant voltage of not less than 15 percent
of the manufacturer's specified voltage.
The lamp output is collimated to a beam
with a nominal diameter of 1.125 inches.
The angle of divergence of the collimated
beam shall be within 4* included angle. A
light detector, directly opposed to the
light source, measures the amount of
light blocked by the smoke in the ex-
haust. The detector sensitivity is restrict-
ed to the visual range and comparable to
that of the human eye. A collimatlng
tube with apertures equal to the beam
diameter is attached to the detector. It
restricts the viewing angle of the detector
to within 16* included angle. An ampli-
fied signal corresponding to the amount
of light blocked Is recorded continuously
on a remote recorder. An air curtain
across the light source and detector win-
dow assemblies may be used to minimize
deposition of smoke particles on those
surfaces provided that it does not meas-
urably affect the opacity of the plume.
The meter consists of two units, an op-
tical unit and a remote control unit.
Light extinction meters employing sub-
stantially identical measurment prin-
ciples and producing substantially
equivalent results but which employ
other electronic and optical techniques
may be used only after having been ap-
proved in advance by the Secretary.
(3) Recorder—a continuous recorder,
with variable chart speed over a minimal
range of 0.5 to 8.0 inches per minute (or
equivalent) and an automatic marker In-
dicating 1-second intervals shall be used
for continuously recording the transient
conditions of exhaust gas opacity, engine
r.p.m. and torque. The recorder scale for
opacity shall be linear and calibrated to
read from 0 to 100 percent opacity full
scale. The opacity trace shall have a reso-
lution within 1 percent opacity. The re-
corder scale for engine r.p.m. and the
recorder scale for observed engine torque
shall be linear and shall have full scale
calibration such as to facilitate chart
reading. The r.p.m. trace shall have a
resolution within 30 r.p.m. The torque
trace shall have a resolution within 10
Ib.-ft. Any means other than strip chart
recorder may be used provided It pro-
duces a permanent visual data record of
quality equal to or better than that de-
scribed above.
(4) The recorder used with the smoke-
meter shall be capable of full-scale de-
flection in 0.5 second or less. The smoke-
meter-recorder combination may be
damped so that signals with a frequency
higher than 10 cycles per second are at-
tenuated. A separate low-pass electronic
filter with the following performance
characteristics may be installed between
the smokemeter and the recorder to
achieve the high-frequency attenuation.
(1) 3 decibel point—10 cycles per
second.
(11) Insertion loss-zero ±0.5 decibels.
(Hi) Selectivity—12 decibels per octave
above 10 cycles per second.
(iv) Attenuation—27 decibles down at
40 cycles per second minimum.
(c) Assembling equipment. (1) The
optical unit of the smokemeter shall be
mounted radially to the exhaust pipe so
that the measurement will be made at
right angles to the axis of the exhaust
plume. The distance from the optical
centerline to the exhaust pipe outlet shall
be 1.0 to 1.5 pipe diameters but never less
FEDERAL REGISTER, VOL. 35, NO. 219—TUESDAY, NOVEMBER 10, 1970
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RULES AND REGULATIONS
A-5.
than 4 inches. The full flow of the ex-
haust stream shall be centered between
the source and detector apertures (or
windows and lenses) and on the axis of
the light beam.
. (2 > Power shall be supplied to the con-
trol unit of the smokemeter in time at
l-ast 15 minutes prior to testing to allow
lor stabilization.
Jj 81). 125 Information to be recorded.
The following information shall be re-
corded with respect to each test:
ta> Test number.
ib> Date and time of day.
ic) Instrument operator.
(d) Engine operator.
(e) Engine Identification numbers—
Date of manufacture—Number of hours
of operation accumulated on engine-
Engine Family—Exhaust pipe diame-
ter—Fuel injector type—M a x i m u m
measured fuel rate at maximum meas-
ured torque and horsepower—Air aspi-
ration system—Low idle r.p.m.—Maxi-
mum governed r.p.m.—Maximum meas-
ured horsepower at r.p.m.—Maximum
measured torque at r.p.m.—Exhaust sys-
tem back pressure—Air inlet restriction.
(f) Smokemeter. Number—Zero con-
trol setting—Calibration control set-
ting—Gain.
(g) Recorder chart. Identify zero
traces—Calibration traces—Idle traces—
Acceleration and lug-down test traces— •
Start and finish of each test.
(h) Ambient temperature in dyna-
mometer testing room.
(i) Engine intake air temperature and
humidity.
(j) Barometric pressure.
(k) Observed engine torque.
§ 85.126 Instrument checks.
(a) The smokemeter shall be checked
according to the following procedure
prior to each test:
(l) The optical surfaces of the optical
section shall be checked to verify that
they are clean and free of foreign mate-
rial and fingerprints.
(2) The zero control shall be adjusted
under conditions of "no smoke" to give
a recorder trace of zero.
(3) Calibrated neutral density filters
having approximately 20 percent and 40
percent opacity shall be employed to
check the linearity of the instrument.
The filter(s) shall be inserted in the light
path perpendicular to the axis of the
beam and adjacent to the opening from
which the beam of light from the light
source emanates, and the recorder re-
sponse shall be noted. The nominal
opacity valve of the filter will be con-
firmed by the Secretary. Deviations in
excess of 1 percent of the nominal opac-
ity shall be corrected.
(b) The instruments for measuring
and recording engine r.p.m.. engine
torque, air inlet restrictions, exhaust sys-
tem back pressure, etc., which are used in
the tests prescribed herein shall be cali-
brated from time to time In accordance
with good technical practice.
§ 85.127 Test run.
(a) The temperature of the air sup-
plied to the engine shall be between
68° F. and 86' F. The observed baro-
metric pressure shall be between 26.5
inches and 31 inches Hg. Higher air tem-
perature or lower barometric pressure
may be used, if desired, but no allow-
ance will be made for possible increased
smoke emissions because of such condi-
tions.
(b) The governor and fuel system
shall have been adjusted to provide en-
gine performance at the levels specified
by the engine manufacturer for maxi-
mum rated horsepower and maximum
rated torque. These specifications shall
be reported in accordance with § 85.51
(b)(3).
(c) The following steps shall be taken
for each test:
(1) Start cooling system.
(2) Starting with a warmed engine,
determine by experimentation the dyna-
mometer inertia and dynamometer load
required to perform the acceleration in
the dynamometer cycle for smoke emis-
sion tests (§ 85.122(a) (2)). In a manner
appropriate for the dynamometer and
controls being used, arrange to conduct
the acceleration mode.
(3) Install smokemeter optical unit
and connect it to the recorder. Connect
the engine r.p.m. and torque sensing
devices to the recorder.
(4) Turn on purge air to the optical
unit of the smokemeter, if purge air is
used.
(5) Check and record zero and span
settings of the smokemeter recorder at
a chart speed of approximately 1 inch
per minute. (The optical unit shall be
retracted from Its position about the
exhaust stream if the engine is left run-
ning.)
(6) Precondition the engine by oper-
ating it for 10 minutes at maximum
rated horsepower.
(7) Proceed with the sequence of
smoke •emission measurements on the
engine dynamometer as prescribed in
§ 85.122.
(8) During the test sequence of § 85.-
122, continuously record smoke measure-
ments, engine r.p.m. and torque at a
chart speed of approximately 1 inch per
minute minimum during the Idle mode
and transitional modes and & Inches per
minute minimum during the acceleration
and lugging modes.
(9) Turn off engine.
(10) Check zero and reset if necessary
and check span of the smokemeter re-
corder by inserting neutral density filters.
If either zero or span drift is in excess
of 2 percent opacity, the test results shall
be invalidated.
§ 85.128 Chart reading.
(a) The following procedure shall be
employed In reading the smokemeter re-
corder chart.
(1) Locate the acceleration mode
(§85.122(a>(2)> and the lugging mode
(§85.122(a)(3» on the chart. Divide
each mode into '/2 -second intervals be-
ginning at the start of each mode. Deter-
mine the average smoke reading during
each '/a-second interval except those re-
corded during the transitional portions
of the acceleration mode (§ 85.122(a) (2)
(lii) ) and the lugging mode (§ 85.122(a)
(2) Locate and record the 15 highest
! 2 -second readings during the accelera-
tion mode of each dynamometer cycle.
(3) Locate and record the five highest
Vi-second readings during the lugging
mode of each dynamometer cycle.
§ 85.129 Calculations.
(a) Average the 45 readings in § 85.128
(a) (2) and designate the value as "a".
(b) Average the 15 readings in 8 85.128
(a) (3) and designate the value as "b".
§ 85.130 Test engines.
(a) The engines covered by the appli-
cation for certification will be divided
into engine families based upon the
criteria outlined in $ 85.89(a).
(b) Emission data engines:
(1) Engines will be chosen to be run
for emission data based upon engine
family groupings. Within each engine
family, the requirements of this para-
graph must be met.
(2) Engines of each engine family will
be divided Into groups based upon ex-
haust emission control system. Two en-
gines of each engine-system combination
shall be run for smoke emission data as
prescribed in §85.132(b). Within each
combination, the engines that feature the
highest fuel feed per stroke, primarily
at the speed of maximum rated torque
and secondarily at rated speed, will be
selected. In the case where more than one
engine in an engine-system combination
have the highest fuel feed per stroke, the
engine with the highest maximum rated
torque will be selected.
(c) Durability data engines:
(1) One engine from each engine-
system combination shall be tested for
lifetime smoke emission data as pre-
scribed in § 85.132(c). Within each com-
bination, the engine which features the
highest fuel feed per stroke, primarily
at rated speed and secondarily at the
speed of maximum rated torque, will be
selected for durability testing. In the
case where more than one engine in an
engine-system combination has the high-
est fuel feed per stroke, the engine with
the highest maximum rated horsepower
will be selected for durability testing.
(2) A manufacturer may elect to
operate and test additional engines to
represent any engine-system combina-
tion. The additional engines must be of
the same model and fuel system as the
engine selected in accordance with the
provisions of subparagraph (1) of this
paragraph. Notice of an intent to test
additional engines shall be given to the
Secretary not later than 30 days follow-
ing notification of the test fleet selection.
(d) Any manufacturer whose projected
sales of new motor vehicle engines sub-
ject to this subpart for the model year
FEDERAL REGISTER, VOL 35, NO. 219—TUESDAY. NOVEMBER 10, 1970
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RULES AND REGULATIONS
A-6.
for which certification Is sought Is less
than 200 engines may request a reduction
In the number of test engines determined
In accordance with the foregoing provi-
sions of this section. The Secretary may
agree to such lesser number as he deter-
mines would meet the objectives of this
procedure.
(e) In lieu of testing an emission data
or durability data vehicles elected under
paragraph (b) or (c) of this section and
submitting data therefor, a manufacturer
may. with the prior written approval of
the Secretary, submit data on a similar
vehicle for which certification has pre-
viously been obtained.
§ 85.131 Maintenance.
(a) (1) Maintenance on the engines
and fuel systems of durability engines
may be performed only under the fol-
lowing provisions:
(1) One major engine servicing to
manufacturer's specifications may be
performed at 500 hours (±8 hours) of
dynamometer operation. A major engine
servicing shall be restricted to the follow-
ing:
(a) Adjust low idle speed.
(b) Adjust valve lash if required.
(c) Adjust injector timing.
(d) Adjust governor.
(e) Clean and service injector tips.
(11) Injectors may be changed if a
persistent misfire is detected.
(Ill) Normal engine lubrication serv-
ices (engine oil change and oil filter, fuel
niter, and air filter servicing and adjust-
ment of drive belt tension, and engine
bolt torque as required) will be allowed at
manufacturer's recommended Intervals.
(Iv) Readjustment of the engine fuel
rates may be performed only if there Is
a problem of dropping below 95 percent
of maximum rated horsepower at 95-100
percent rated speed.
(v) Leaks In the fuel system, engine
lubrication system and cooling system
may be repaired.
(vl) Any other engine or fuel system
maintenance or repairs will be allowed
only with the advanced approval of the
Secretary.
(2) Allowable maintenance on emis-
sion data engines shall be limited to the
adjustment of engine low idle speed at
the 125-hour test point.
(b) Complete emission tests (see
§§ 85.121-85.129) shall be run before and
after any engine maintenance which may
reasonably be expected to affect emis-
sions. These test data shall be supplied
to the Secretary immediately after the
tests, along with a complete record of all
pertinent maintenance, Including an en-
gineering report of any malfunction
diagnosis and the corrective action taken.
In addition, all test data and mainte-
nance reports shall be compiled and pro-
vided to the Secretary in accordance with
§ 85.53.
(c) If the Secretary determines that
maintenance or repairs performed have
resulted In a substantial change to the
engine-system combination, the engine
shall not be used as a durability data
engine.
§85.132 Service accumulation anil
emission measurements.
Service accumulation shall be accom-
plished by operation of an engine on a
dynamometer.
(a) Emission data engines: Each
engine shall be operated on a dynamom-
eter for 125 hours with the dynamometer
and engine adjusted so that the engine is
operating at 95-100 percent of rated
speed and at least 95 percent of maxi-
mum rated horsepower. During such
operation, the engine shall be run at the
exhaust back pressure specified in
8 85.123(c) and the air Inlet restriction
specified In § 85.123 (d) except that the
tolerances shall be ±0.5 Inches of Hg.
and ±3 inches of water respectively. Ex-
haust smoke tests shall be conducted at
zero and 125 hours of operation.
(b) Durability data engines: Each en-
gine shall be operated on a dynamometer
for 1,000 hours with the dynamometer
and engine adjusted so that the engine
is operating at 95-100 percent of rated
speed and at least 95 percent of maximum
rated horsepower. During such operation,
the engine shall be run at the exhaust
back pressure specified In 9 85.123(c) and
the ah- Inlet restriction specified In 8 85.-
123 (d) except that the tolerances shall
be ±0.5 Inches of Hg. and ±3 Inches of
water respectively. Exhaust smoke meas-
urements shall be made at zero hours and
at each 125 hours of operation. All re-
sults except the zero hour results shall
be used to establish the deterioration
factors (see § 85.133).
(c) All tests required by this subpart
to be conducted after 125 hours of dyna-
mometer operation or at any multiple
of 125 hours may be conducted at any ac-
cumulated hours within 8 hours of 125
hours or the appropriate multiple of 125
hours, respectively.
(d) The results of each emission test
shall be supplied to the Secretary Im-
mediately after the test. In addition, all
test data shall be compiled and provided
to the Secretary In accordance with
{ 85.53.
(e) Whenever the manufacturer pro-
poses to operate and test an engine which
may be used for emission or durability
data, he shall provide the zero hour test
data to the Secretary and make the en-
gine available for such testing under
§ 85.54 as the Secretary may require be-
fore beginning to accumulate hours on
the engine. Failure to comply with this
requirement shall invalidate all test data
submitted for this engine.
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APPENDIX B
NEW JERSEY SMOKE TEST PROCEDURES
(NEW JERSEY AIR POLLUTION CONTROL CODE. CHAPTER 14)
-------
B-2.
CHAPTER 14, AIR POLLUTION CONTROL CODE
SECTION 1 - DEFINITIONS
1.1 PERSON: Includes corporations, companies, associations,
societies, firms, partnerships and joint stock companies as
well as individuals, and shall also include all political
subdivisions of this State or any agencies or instrumentalities
thereof.
1.2 MOTOR VEHICLE: Includes all vehicles propelled otherwise
than by muscular power, excepting such vehicles as run only
upon rails or tracks.
1.3 AUTOBUS: .Includes all motor vehicles used for the transporta-
tion of passengers for hire.
1.4 DIESEL-POWERED MOTOR VEHICLE: A self-propelled vehicle de-
signed primarily for transporting persons or property on a
public street or highway which is propelled by a compression
ignition type of internal combustion engine; for purposes
of this chapter passenger automobiles and motorcycles are
excluded.
1.5 DIESEL-POWERED ENGINE: A mechanism for converting energy
into mechanical force and motion by using a compression
ignition type of internal combustion engine.
1.6 SMOKE: Small gasborne and airborne particles, exclusive
of water vapor, arising from a process of combustion in
sufficient number to be observable.
1.7 OPACITY: The property of a substance which renders it
partially or wholly obstructive to the transmission of visible
light expressed as the percentage to which the light is ob-
structed.
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B-3.
1.8 EXHAUST EMISSIONS: Substances emitted into the atmosphere
from any opening downstream from the exhaust ports of a
motor vehicle engine.
1.9 SMOKEMETER: A device constructed in such manner as to
measure smoke opacity by light obstruction between a light
source and photoelectric cell which will indicate the percent
opacity of smoke at a point approximately four (4) inches from
the engine exhaust outlet. The device shall be of design
meeting "Specification for Diesel-Powered Vehicle Smokemeter"
on file with the State Commissioner of Environmental Protec-
tion and approved for use in accordance with manufacturers'
recommended procedures for calibration, mounting and main-
tenance.
1.10 OPERATING MODE: A procedure for operating a diesel-powered
motor vehicle or a diesel-powered engine during measurement
of smoke opacity in the exhaust emissions.
1.11 CHASSIS DYNAMOMETER: A device constructed in such a manner
as to simulate highway driving conditions on a stationary
motor vehicle.
1.12 RPM - Revolutions per minute
1.13 MPH - Miles per hour
SECTION 2 - PUBLIC HIGHWAY STANDARD
2.1 No person shall operate any diesel-powered motor vehicle or
permit any diesel-powered motor vehicle which he owns to be
operated upon the public highways of the State if the vehicle,
when in motion, emits visible smoke in the exhaust emissions
within the proximity of the exhaust outlet, for a period of
more than five (5) seconds.
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B-4.
SECTION 3 - INSPECTION STANDARD
3.1 Any motor vehicle propelled by a diesel-powered engine
which is subject to inspection at the premises or places
of business of the owner or lessee by the Division of
Motor Vehicles as a condition of compliance with said
inspection, shall not emit smoke in the exhaust emissions
in excess of the smoke opacity standards set forth in
Table 1.
3.2 Any autobus propelled by a diesel-powered engine which
is subject to inspection at the premises or places of
business of the owner or lessee by the Public Utilities
Commission as a condition of compliance with said inspection
shall not emit smoke in the exhaust emissions in excess of
the smoke opacity standard set forth in Table 2.
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B-5.
TABLE 1
VEHICLES SUBJECT TO INSPECTION BY THE DIVISION OF MOTOR VEHICLES
(Reference P.L. Title 39:8-10)
Type . Smoke
of Inspection Operating Mode* Ojpacity Standard
Self inspection au- (1) Vehicle driven on 20%
thorized by Division chassis dynamometer
of Motor Vehicles at with simulated load
the premises or places by power absorption
of business of the
owner or lessee -alternate-
(2) Vehicle driven in low 20%
gear with simulated
load by braking action
'•PROCEDURES :
(1) VEHICLE DRIVEN ON CHASSIS DYNAMOMETER WITH SIMULATED
LOAD BY POWER ABSORPTION - with smokemeter firmly positioned
on the exhaust outlet and vehicle positioned on the chassis
dynamometer proceed with the following steps:
STEP 1
With vehicle on a chassis dynamometer under no power absorp-
tion, select a gear ratio which will produce a maximum
vehicle speed of 45-60 MPH at governed engine RPM.
STEP 2
With engine running at governed engine RPM, apply power
absorption load to the dynamometer until such loading re-
duces the engine RPM to 80 per cent of the governed speed,
the peak smoke opacity measured over a period of 5 to 10
seconds with the engine under such loading shall be the smoke
opacity.
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B-6.
-PROCEDURES:
(2) VEHICLE DRIVEN IN LOW GEAR WITH SIMULATED LOAD BY
BRAKING ACTION - with smokemeter firmly positioned on the
exhaust outlet, proceed with the following steps:
STEP 1
Select a gear ratio which will produce a maximum speed of
10-15 MPH, at governed engine RPM, drive vehicle at 10-15
MPH at governed engine RPM.
STEP 2
Load the engine by applying brakes until engine RPM is
lugged down to 80 per cent of the governed engine RPM,
the peak smoke opacity measured over a period of 5-10
seconds with the engine under such brake loading shall be
the smoke opacity.
NOTE:
(a) All measurements are to be made after engines have been
run a sufficient period of time to be at normal operating
temperature.
(b) Separate measurements shall be made on each exhaust
outlet on vehicles equipped with dual exhaust outlets.
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B-7.
TABLE 2
INSPECTION STANDARDS
VEHICLES SUBJECT TO INSPECTION BY THE PUBLIC UTILITIES COMMISSION
(Reference P.L. Title 48: 40-2.1 and 2.1A, Title 48: 4-18)
Type
of Inspection
Inspection of Public
Utilities Commission
at the premises or
places of business of
the owner or lessee
Operating Mode*
Autobus driven with
rapid acceleration
Smoke
Opacity Standard
40%
-PROCEDURE
STEP 1
With smokemeter firmly positioned on exhaust outlet and
transmission engaged, drive autobus by accelerating as
rapidly as possible to approximately 20 MPH.
STEP 2
Release accelerator pedal and brake to full stop.
STEP 3
The peak smoke opacity measured during the acceleration to
20 MPH shall be the smoke opacity.
NOTE:
(a) All measurements are to be made after engines have been
a sufficient period of time to be at normal operating tem-
perature.
(b) Separate measurements shall be made on each exhaust
outlet on vehicles equipped with dual and separated exhaust
outlets.
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B-8.
(c) A single, combined measurement shall be made on
the exhaust outlets on vehicles equipped with dual,
adjacent exhaust outlets.
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APPENDIX C
Information and Operating Instructions
For PHS End-of-Line and Inline Smokemeters
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C-2
June 1970
ITRevised Preliminary Operating Instructions for Use of the
U.S. Public Health Service Full-Flow, Light-Extinction Smokemeter"
This revised preliminary procedure is offered to acquaint the user with the
PHS Smokemeter and its basic operation. For details regarding the design principle,
method of construction, specifications, drawings, etc. , please refer to the letter
from the Public Health Service to interested industry members from Howe Hopkins,
NAPCA, dated January 4, 1968, and revised February 19, 1968. Additional changes
requested by NAPCA in wiring and circuitry have required the February 1968 in-
structions to be revised.
General
The PHS Smokemeter consists of two items, an optical light source photo cell
assembly which is mounted on an exhaust stack, and a remote readout box con-
taining air purge controls and a meter for indication of percent light opacity
External requirements for use of this Smokemeter are a stable minimum 6. 5 volt
DC, 2. 75 amp power supply, and an approximate 2 SCFM of 60-120 psi shop air.
A 0-10mv output is available from the Smokemeter readout box suitable for use
with a 0-10mv null balance potentiometric type strip chart recorder, if desired.
Mounting of the Smokemeter
To measure smoke from a 4" OD stack, the usual procedure is to locate the 10"
OD aluminum ring on which the collimating tubes are mounted such that the smoke
plume is contained within, yet completely fills, the ring.
To Place Smokemeter in Service
1. Mount optical device on pipe and connect air hose and interconnect cable to
readout box. Connect shop air to air inlet on readout box. Adjust pressure regu-
lator to give 2 SCFM air purge to the optical device (Calibration curve supplied on
inside lid of readout box).
2. Connect DC power supply using 2 conductor cable provided (Alligator clips
are provided for use with cell battery, if desired). Red (positive) clip should be
connected to the positive pole of power source.
FOR READOUT BOXES EQUIPPED WITH API, 100 - 0% OPACITY METERS
3. Turn power switch to "on" and meter-recorder switch to "meter". Turn
three-position switch to "lamp volts". Remove cover from light bulb and, using a
sensitive voltmeter connected across the bulb terminals, adjust external power
supply to give 6 volts at light bulb with bulb in circuit and burning. It is assumed
that the external power supply is adjustable or can be so modified. Next, remove
panel board and adjust small potentiometer (black in color, Bourns No. 3007P)
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C-3
located on underside of panel to read 40% (6 volts) on the remote box meter. The
mic roam meter used to read percent transmittance is now in the circuit as a DC
voltmeter and zero opacity is equivalent to 10 volts. This procedure results in
6 volts DC at the bulb and the instrument meter is calibrated in the circuit to reflect
the voltage applied at the bulb. Only a minor trim adjustment should be necessary
as the setting should be fairly stable during shipment and day to day use.
4. Turn three-position switch to "meter" and adjust "calibration" pot (10
turn located below meter in center of panel) to full scale zero percent light opacity.
(Mechanical zero (100%) should be checked and adjusted prior to this step as meter
may change static zero due to shipment).
5. If measurement via meter indicator is desired, the smokemeter is ready
for use and the engine exhaust or other source of smoke can now be passed through
the optical device.
6. If it is desired to continuously record the output via a strip chart recorder,
connect external 0-10mv to a suitable precalibrated null balance recorder. Flip
meter-recorder toggle switch to "recorder" position. Zero recorder by depressing
red button to the left of the calibration dial using zero adjust on recorder. Should
recorder zero require adjustment, the recorder should be recalibrated with a labora-
tory millivoltage source. Next, adjust to lOmv full scale recorder indication using
the 10 turn "rec. adj. " potentiometer. The smokemeter is now ready for operation.
To Take Smokemeter Out of Service
1. Turn three-position switch to "off".
2. Turn power switch to "of".
3. After engine is shut down, disconnect or turn "off" air supply.
4. Place "shorting connector" provided on interconnect lead if disconnected
from remote box.
Maintenance
Due to the simplicity of design, lack of sophisticated electronics, etc. , this
smokemeter, if handled properly, should be relatively trouble-free. Do not handle
optical unit by the collimating tubes. Difficulties in drift or change in baseline are
generally caused by one of two things:
1. Dirty or increasingly dirty lens and photo cell.
2. An unstable DC power supply such as a wet cell battery. (A wet battery, if
used over an extended period of time, will discharge sufficiently to result in
low readings. A trickle charger or similar battery boosting device or a suit-
able substitute power, source, is recommended. )
-------
C-4
Supplied with the instrument is an extra GE No. 1630 light bulb and leads for
simple replacement should the light bulb burn out. (Located under instrument
panel).
It is recommended that periodic cleaning of the light source lens and photo
cell be made. How often this will be necessary will depend on the usage of the
instrument, the amount of smoke passed, etc. It is important to have the purge
air on before starting engine or other source of smoke as this will greatly extend
the cleanliness and reduce the amount of lens cleaning necessary. When replacing
the light bulb in the light bulb socket, it should be noted that elongated holes are
provided in the mounting flange to permit movement and adjustment of the light
bulb position relative to the collimating tubes. Adjust the position of the light
bulb so that the light beam is centered in the collimating tube on which the photo
cell is mounted. This adjustment should permit ample light intensity to drive
the meter indicator to 0 percent with reserve calibration adjustment. Should 0
percent light opacity be difficult to obtain under clear conditions, suspect either
low voltage, dirty lens and photo cell, or incorrect positioning of the light bulb in
the collimating tubes.
These instructions are provided in lieu of an official NAPCA publication and
are subject to revision.
-------
C-5
Operation and Maintenance of the PHS Inline Smokemeter
General
The PHS inline smokemeter consists of an optical unit containing the
light source and photocell assemblies, which is mounted in the exhaust
system, and a remote readout-control box containing purge air controls,
a meter to indicate smoke opacity, and controls to zero and upscale the
smokemeter during calibration. A 0-10mv output is available from the
readout box for use of a strip chart recorder, if desired.
Smokemeter Power Supply
The same power supply and lamp voltage (6. OvDC) that are used for
the end-of-line smokemeter are satisfactory for the inline instrument.
A toggle switch has been added to the panel of the conventional read-out
box to permit the normal ten mv output from the voltage divider. This
switch deletes the ZOO ohm and 750 ohm resistors from the voltage divider,
as shown on the wiring diagram (p. C-8 ).
Smokemeter Purge Air
The usual air supply controlled through the regulator in the read-out
box is connected to the stainless steel center body to purge the small
sealed optical tubes. Set the pressure gage at 45 psig. This setting pro-
duces three SCFM of air, which is satisfactory. It is important to turn
this purge air on before starting the engine and, since excessive heat may
damage the Viton gaskets used to seal the small tubes at the glass lens,
the purge should be left on for at least ten minutes after engine shut-down.
A separate air supply for the large collimating tubes is furnished, and
includes a regulator, flow orifice, pressure gage, and water separator.
This purge system is provided to cool the lamp and photocell and also to
keep the collimating tubes clear of any smoke circulating in the vicinity of
the smokemeter. The pressure should be set to about 29 psig for about
two SCFM flow.
Calibrating the Inline Smokemeter
The inline instrument should be calibrated with the same two-in dia-
meter neutral density filters that are furnished with the regular PHS
smokemeter. Calibration is complicated somewhat by the instruments
position in the exhaust system. One end of the smokemeter must be dis-
connected from the exhaust system and the filter held in the light beam
passing through the pipe. The filter should be held at a right angle to the
light beam. The pertinent calibration data for the inline smokemeter is
given as follows:
-------
C-6
CALIBRATION DATA FOR PROTOTYPE IN-LINE
VERSION OF PHS SMOKEMETER
SERIAL NUMBER IL1002
Neutral Density Calibration Results
ND Filter Recorder
Calibrated Opacity. % Opacity, %
22.5 22.5
37.5 37.6
49.5 49.7
61.0 61.3
69.0 69.3
73.5 73.5
77.0 77.2
82.5 82.4
86.0 86.1
89.5 89.5
With the toggle switch in position "Increase Output to Recorder" and
lamp burning at 6. Ov DC, the following values should be observed:
(1) With ten-turn pot labeled "Recorder Adjust" set
at 2.07, output to recorder is ten mv.
(2) With this pot at its maximum setting, recorder
output is 12 mv.
(3) With ten-turn pot labeled "Calibrate" at its maxi-
mum setting, panel meter reading is 65%.
Several minutes should be allowed between engine shut-down and any
attempt to zero the smokemeter. This wait will allow smoke in the pipe to
dissipate and hence permit a true zero reading to be obtained.
Cleaning the Smokemeter
The glass lenses can be removed for cleaning by the following procedure.
First, unbolt completely the mounting bracket -which locates the ten-in
diameter optical ring to the central stainless steel exhaust pipe. Or,
alternatively, remove both large collimating tubes from the ring at the
four-bolt flange. Either of these steps will allow access to the brass male-
type threaded nut at the end of the small sealed tube. The lens and the
Viton gaskets can then be removed from the tube. The lens is cleaned by
wiping with a clean cloth, while the inside of the small tube can be cleaned
by running a swab through it, much like cleaning a rifle bore.
-------
C-7
Reassembling the Smokemeter
Replace the gaskets and lens in the end of the small tube, making
sure the gaskets fit squarely against the lens. Tighten the brass'nut
just enough to achieve a snug fit. Do not overtighten the nut, as the
lenses are easily cracked by excessive pressure. Reassemble the large
collimating tubes and their mounting bracket onto the central exhaust
pipe. With the lamp burning and a ten mv-span recorder connected to
the output, adjust the position of the mounting bracket on the pipe so that
a minimum of ten mv output is obtained with some gain adjustment re-
maining on the ten-turn pot labeled "Recorder Adjust".
-------
MINIATURE LAMP
G.E.NO. 1630
6.9V,2.73A,2Z.SC.P.
O.C. PREF. (A)
SEC ORWG.NO.C-IIBC
KNIFE DISCONNECT TERMINAL3-
API NO. 32446
t HEO'O PER UNIT
BEE ORWO. NO. C-II8C
MEASURING POINT FOR
METER VOLTAGE CALIBRATION
PHEFOCUS LAVP SOCKET
COLE-KERSEE NO. 2722
SEE ORWO NO C-IIBC
FOR MODIFICATION
INTERNAL LAUP SUPPLY WIRING
MO. 14 STRANDED
CHASSIS CONNECTOR
MS-3I02A-IOSL-4P
CABLE CONNECTOR
MS-3I06A-IOSL-4S
A-BLACK a B-REO
BELDEN 1959
NO. 14 STRANOCO
INCASED IN
PLASTIC TUBING
LENGTH t FT.
: BARRIER TERMINAL BLOCK
CINCH-JONES. I4O SERIES
4 CONTACTS
• TERMINAL CONNECTOR
API NO. 3EI»S
(BEND AS SHOWN ON E-IOO)
(TTP. S PLACES) SOLDER TO LEADS
TO STABLE D.C. SOURCE
10 VOLT 9 AMP POWER SUPPLY
KEGULATEO TO ZXIO-8 VOLT*
BOO OHM IO TURN POT.
SPECTROL MODEL 930
WITH TURNS COUNTER DIAL
0-IOMV RECORDER SPAN
BANANA JACK
H.H. SMITH 269-RB
•DTE - ALL RESISTORS ARE
VZ W. 9% UNLESS OTHERWISE
NOTED
14
Jk
?<^J OPTICAL UNIT
C
ALL LEADS ENCASED •
CN PLASTIC TUBING 9
LENGTH 20 FT. .-^j
A-BLACK 8 B-REO 1
TOGGLE SWITCH -• BELOEN 1999
t
£
*
0
\
S
5
C
4'
I
+
0
/
/ /
/ /
n /
J /
-------
APPENDIX D
SMOKE TRACE EVALUATION SHEETS FOR
FEDERAL SMOKE TESTS WITH PHS END-OF-LINE
AND INLINE SMOKEMETERS
-------
D-2.
SMOKE TRACE EVALUATION SHEET
Smokemeter: End-of-Line Date: March 7, 1972
Engine: Cummins NHC-250 Truck No: 274
Accelerations
First Sequence Second Sequence Third Sequence
Interval No. Smoke % Interval No. Smoke % Interval Nov Smoke %
/
^
3
./
S~
^
7
a
1
/o
//
/J2.
y5
/•/
/£•"
Total Smoke %
9,O
/•¥-, o
/^ O
/9.0
<=y^. 0
<7?3.$~
J3 6
^ A/ ^^
&ftT' ^
J7. o
Jf.0
<3$ S^
J7.6
^^f o
J)t,. 3
ol4-. O
33A*
Factor (a) -Jotil.'Z'- ,^-^f
/
-2.
'J
4-
S~"
&
7
$
y
/o
,i
X2
X-5
//
/S~
j%
y If ^^^
&& / f3
•2^0
J7.!T
33. S'
**£.£*'
30.O
ot&.6
°*1,O
Ja.o
3*ko
33.0
33.0
32. f
34,0
¥fe,.£>
/ G tj
&c & * Q
/x.o
<3<3.O
<>i O
<3 /-S~~
^ 3 5^
3/.3
3/.0
33 2t
36,0
/ft. ^
/
^
3
<
,3^"
2>3. 0
31 ^
3J.O
J4.0
-53.6
tto.f
y
^
y
?
g~
3f.o
3*7.0
3? 0
36, 6
f£> O
f?9.o
Factor (b) = >$/#£ Q = 33.<2%
15
omments:
-------
D-3.
SMOKE TRACE EVALUATION SHEET
Smokemeter: Inline Date: March 7, 1972
Engine: Cummins NHC-250 Truck No: 274
Accelerations
First Sequence Second Sequence Third Sequence
Interval No. Smoke % Interval No. Smoke % Interval NOT Smoke %
/
j?
3
*£
•^
&
f
f
'7
.'^
/>•
/Jl
>''J
,(•'
/j-"
Total Smoke %
9. S~~
Jf.3
I? 0
JJ< /
3f,O
dPff-f
J^. f
jf.3
JUsX"
o?3^o
•34..O
^?3.&
JU.1
-?t>.3
36>.O
3?>£>.J
Factor (a) = /orf.'X- <£$•
/
• J.
J
^
£T
(,
?
g
f
/o
//
xa/
/3
i*
J5T
/3,o
tf.o
»22.O
-SS'.O
JZ.O
tj'f.S'
30.6
3/. O
~2X X
30 1)
<21.o
jl.f
Jo.o
30. Z~
£c.O
¥-&*£• 3
45
Lugging
First Sequence Second Sequence
/
^
3
4
S-"
C
7
/
1
/o
//
tJL
/3
/•*
'S^
/3.jf
/«d
U.O
•?o. o
cfo.O
?/. .0
J?8 ,Z~
<=3$. O
ajl.O
-Z
3fe.O
Third Sequence
Interval No. Smoke % Interval No. Smoke % Interval No. Smoke %
/
.?
3
4
^
3D.O
~s9.0
3o. O
^fc.$^
o?8 ,0
Total Smoke % /^T ^
Factor (b) = >^^/ ^ -
/
^.
J
^
^ —
31. 3 %
JV D
J3.0
33.0
3^-.G
ji.o
M.D
/
J.
3
J
^
30.O
30.0
•?
-------
D-4.
SMOKE TRACE EVALUATION SHEET
Smokemeter: End-of-Line
Engine: Cummins V-903
Date: March 17, 1972
Truck No: 972
Accelerations
First Sequence Second Sequence Third Sequence
Interval No. Smoke % Interval No. Smoke % Interval No? Smoke %
/
«2
3
<£
f
£
9
j
f
/ts
//
/*•
/.$
'S
,
<29. 8
Jf.S'
^o.o
/J.f
/£ O
/7,o
x^o
/to
<2&O
30*. /
Factor (a) ; &*/. (, = /"•-
f
^
3
y
^
6,
7
^
f
/o
//
/^
S3
'4
/x~
3V
7.0
/.5~"
// ^
/j-^
/S.o
fl.-z.
-2% $ '
j'^.d;
-«?/<2^
JfJ 0
^>4 o
•JS.S*
^23 4— '
~?3.O
cj^.O
j>c?-7
45
Lugging
First Sequence Second Sequence
J
^
3
y.
^
£
7
2
q
10
//
/I,
/3
/y
/r"
3.0
7^
/c,e
/*>,&
J S'
/o.o
//.O
/£,?
/L.O
^
Factor (b) = 3^^. 3 - <=£
/
^?
J
<
5^
/ //^
15
Comments :
oZO 0
J?/.0
<*?&&
<=J0.$ —
<£4).3
/0<2.&
/
^
J
*£
j— *
ojy.j"
-^7. ^
=?j?..s — '
«Z-?. 4x
-*/,£>
//!.<£,
-------
SMOKE TRACE EVALUATION SHEET
Smokemeter: Inline Date; March 17, 1.o
/r.o
/f.o
M
/to
<2(e.O
^^.f
£0 0
/£ o
/3.O
/¥•.$
/4 ' ^
/^•O
/7,O
JSj. O
Factor (a) -£0T; ^ = /-^'o
/
2,
3
^
5-
6
7
g
q
/o
/,
/£,
/3
/*L
/S^
2y.
-f' 0
b. O
If
8 ^
S3.o
/7,f
J3.O
Js'.o
,£/.£'
/f ^
/1.O
-2O.O
JL0.2,
//. f
/ST.O
J3S.A,
45
Lugging
First Sequence Second Sequence
i
^
j
x
5"
^
7
0
q
/O
//
/^
/3
//
/^ —
J.o
£.0
r.c.
7,f
S.O
J*,5^
9.X~
/O
/7<3
/to
/7.3
/ft?
Third Sequence
Interval No. S^oke % Interval No. Smoke % Interval No. Smoke %
/
^
$ —
/J £>
rt.1
/s.z'
/7.X"
/X.^L
Total Smoke % J&. /
Factor (b) = oZ& /• fa =
/
oZ
3
y
s~
,r.ty.
/f.J
jfiO
;x.f>
/7.f
/7. ^
f%3
/
^i
3
y
S"~
/7.f
/L. 0
/(*.£>
/£.. 3
/({..<£•
/^,^
15
Comments:
-------
D-6.
SMOKE TRACE EVALUATION SHEET
Smokemeter: End-of-Line Date: March 24, 1972
Engine: Mack ENDT 673B Truck No: 60124
Accelerations
First Sequence Second Sequence Third Sequence
Interval No. Smoke % Interval No. Smoke % Interval NOT Smoke %
/
_£
3
«/
$
42 o
/-? f
//.^
j 0
H.3
J30. 1
45
Lugging
First Sequence Second Sequence
i
2
3
/
//
/=2
/5
/*r
/r"
tf.o
.23. 0
•*/.o
~2C3
/6,S^
/7.Z~
/^.^
/g'.g'
/?. 3
/J.o
// ^
/^?. <5
1.3
S'.f
J0.3
~te^7
Third Sequence
Interval No. Smoke % Interval No. Smoke % Interval No. Smoke %
/
_2
3
y
,j-~
J.o
l.t
9.3,
f.o
J.S"
Total Smoke % ^^ $""*
Factor (b) = /*Jl£C> - $
/
^L
3
*/
^ —
'/%
7. S''
^ ^
f O
1.0
q.f
^.0
/
^
^
^
f
^,d
^.-2,
7.0
7.3
to
33, J-~
15
Comments:
-------
D-7.
SMOKE TRACE EVALUATION SHEET
Smokemeter: Inline
Engine: Mack ENDT 673B
Date: March 24, 1972
Truck No: 60124
Accelerations
First Sequence Second Sequence Third Sequence
Interval No. Smoke % Interval No. Smoke % Interval NOT Smoke %
/
5
•3
^
S^
df
'/
./
-.•'
';?
/-?.
'.3
/-'•
/_j"
Total Smoke %
/ ^~- ^>
f(0, £
//./
/J. 0
y/ J*
yx 5^
t£.3
/3. O
//.g
;c.o
9.x
j.g'
J. o
to
7 g-
/1L6
/
^
j>
•^
s~
^
7
/'
y
Jo
//
S3,
/3
/^
/s**
/3.O
/7o
/S.o
/to
/4-.0
y^/, ^
yj_ *7
/4a
/3.o
//.£>
/£). &
/o.o
7
/
.2
J
^
S~
£
7
g
q
/O
//
/2
/J
/•<
/S^"
y-j4 ^?
ys*. f
/ytg'
/^.^
/£•£'
/J.S*'
//£>
/J".^
/^. <5
_S-S^
g g~
<$,&
?.o
6,.^
^, /
/££-7
Factor (a) : S/9-4 = //.£*%
45
Lugging
First Sequence Second Sequence
Third Sequence
Interval No. Smoke % Interval No. Smoke % Interval No. Smoke %
/
-^
3
•*/.
^
7.c
£.0
V^' *J
y^ , J5
^r^>
Total Smoke % ^^ #
Factor (b) = ^/ / : ^
/
^
^
/
s~~
\3K
4.3
£.^
7,0
<£-E/
7.o
33,0
/
.2.
3
^
J^
S.ji
s^.3
w/01^*
^ -^C
-?tj
15
Comments:
-------
|