v>EPA
United States
Environmental Protection
Agency
Industrial Environmental Research
Laboratory
Research Triangle Park NC 27711
EPA-600/7-79-232C
December 1979
Assessment of Diesel
Particulate Control:
Particle Size Measurements
Interagency
Energy/Environment
R&D Program Report
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development. U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
6. Scientific and Technical Assessment Reports (STAR)
7. Interagency Energy-Environment Research and Development
8. "Special" Reports
9. Miscellaneous Reports
This report has been assigned to the INTERAGENCY ENERGY-ENVIRONMENT
RESEARCH AND DEVELOPMENT series. Reports in this series result from the
effort funded under the 17-agency Federal Energy/Environment Research and
Development Program. These studies relate to EPA's mission to protect the public
health and welfare from adverse effects of pollutants associated with energy sys-
tems. The goal of the Program is to assure the rapid development of domestic
energy supplies in an environmentally-compatible manner by providing the nec-
essary environmental data and control technology. Investigations include analy-
ses of the transport of energy-related pollutants and their health and ecological
effects; assessments of, and development of, control technologies for energy
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mental issues.
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This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
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EPA-600/7-79-232c
December 1979
Assessment of Diesel
Particulate Control:
Particle Size Measurements
by
Joseph D. McCain and M. Gregory Faulkner
Southern Research Institute
2000 Ninth Avenue, South
Birmingham, Alabama 35205
Contract No. 68-02-2610
Task No. 8
Program Element No. EHE624A
EPA Project Officer: Dennis C. Drehmel
Industrial Environmental Research Laboratory
Office of Environmental Engineering and Technology
Research Triangle Park, NC 27711
Prepared for
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Research and Development
Washington, DC 20460
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ABSTRACT
The increasing appearance of the diesel engine on the
passenger car market has led to concern over particulate
emissions (smoke) from these engines. Possible control stra-
tegies involving particulate collection in the hot exhaust
stream requires knowledge of the concentrations and size dis-
tributions of the particulate matter at exhaust conditions.
Tests were performed on an Oldsmobile 98 diesel automobile to
obtain data on these parameters typical of a light duty vehicle,
Data are presented for operations under four simulated driving
conditions.
11
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CONTENTS
Abstract ii
Figures iv
Tables v
1. Introduction 1
2. Test Conditions 3
3. Test Results 7
4. Conclusions 16
5. References 17
111
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FIGURES
Number
1 Modified exhaust pipe and test equipment layout
for diesel emission testing 5
2 Particle size distribution for FET-cycle 9
3 Particle size distribution for 56 kmph no load
condition.. .' 10
4 Particle size distribution for 56 kmph with
load condition 11
5 Particle size distribution for 97 kmph condition.. 12
6 Relative concentration versus time for three
particle size ranges during several FET cycles.... 13
7 Electron micrograph of diesel particulate 14
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TABLES
Number Page
I Results of Cascade Impactor Sampling 8
v
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SECTION 1
INTRODUCTION
The federally mandated fuel economy standards for passenger
automobiles have resulted in considerable impetus being given
to the introduction of substantial numbers of diesel powered
automobiles into the passenger car fleet. Unfortunately, the
diesel engine has a much higher level of combustion by-products
than the spark ignition gasoline engine (by factors of 30 to 50
in particulate emissions). The diesel particulate emissions are
primarily carbonaceous, but 10 percent to 50 percent by weight
of the material is adsorbed higher molecular weight organics, a
significant portion of which may be polycyclic aromatics.1 Pre-
liminary results of Ames microbial mutagenicity bioassay tests
have indicated the possibility that these particulates may be
carcinogenic.
Possible methods for reducing diesel particulate emissions
are combustion modification or the use of aftertreatment devices
in the exhaust gas stream to collect and/or render the material
innocuous. Such treatment may be mandatory if the emissions do
prove to represent a significant carcinogenic risk. Selection
of candidate aftertreatment devices requires knowledge of the
chemical and physical properties of the particles. These include
particle morphology, particle size distribution, bulk densities
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of the collected material, and particulate mass concentration
and emission rates in the exhaust gas stream. Because the organic
fraction of the particles appears to be adsorbed on the surfaces
of graphitic carbon base particles, the temperature history of
the gas stream may be important. If the sorption process takes
place at elevated temperatures, then collection of the particu-
late at the normal, relatively hot, exhaust gas temperatures
may be sufficient. However, if the sorption takes place only
during and after cooling of the exhaust stream to near ambient
conditions, hot particle collection will not result in the removal
of the organic fraction.
The data presented in the following chapters represent the
first of a planned series of experiments to characterize the
exhaust emissions from the point of view of aftertreatment exhaust
gas cleanup and to collect samples for bioassays to determine
whether the biological effects of particles collected at exhaust
line temperatures are the same as those collected after dilution
and cooling by ambient air.
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SECTION 2
TEST CONDITIONS
The exhaust samples were obtained at the U.S. Environmental
Protection Agency facility located at Research Triangle Park,
North Carolina, from November 27 through December 1, 1978. The
source of particulate was a 1979 Oldsmobile 88 with a 350 cubic
inch displacement diesel engine which was operated on a Burke E.
Porter No. 1059 Chassis Dynamometer. The dynamometer was pro-
grammed to emulate the Clayton roadload curve for waterbrake dyna-
mometers which are used for vehicle certification. Test conditions
included the 13 minute Fuel Economy Test (FET) combined city-highway
test cycle, 97 kmph highway cruise, 56 kmph highway cruise, and 56
kmph no load conditions. However, the engine operating conditions,
the particulate sampling methods, and the exhaust temperature con-
ditions were all different from those required by EPA for vehicle
certification and the test results should not be compared to those
acquired by official certification methods and conditions.
The vehicle operating conditions and experimental setup were
selected to provide samples collected at elevated exhaust gas
temperatures for the same engine cycle as the very large (10 kg)
sample collected for bioassay work. This 10 kg bioassay sample
was collected during the FET test cycle using a standard "con-
stant volume" automatic dilution tunnel. The hot samples col-
lected were to be used for Ames tests to provide some indication
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of the relative mutagenicity of material collected at the exhaust
line temperatures and material collected after cooling and dilu-
tion. This information is intended to provide some insight into
whether hot collection of the particles will remove the carcino-
genic component of the exhaust.
Sampling and measurement methods included Andersen cascade
impactors, conventional filtration techniques followed by con-
densers and organic sorbent traps using XAD2 rosin, optical
single particle counters, and an electrical aerosol analyzer.
All samples were taken directly from a modified exhaust pipe
which was run out from under the chassis and down the passenger
side of the automobile to permit access to the exhaust stream.
Figure 1 is a diagrammatic sketch of the layout of the exhaust
system and measurement instrumentation during the tests.
Andersen Model III cascade impactors with glass fiber
impaction substrates and backup filters were used to obtain
total particulate loadings and particle size distributions on
a mass basis over the size range from about 0.4 ymA to 5 pmA.
The impactors, which were operated in an oven, were close-
coupled to the exhaust pipe. During runs at a steady engine
load (56 kmph and 97 kmph), the oven was maintained at the same
temperature as the exhaust gas temperature at the sampling point.
During the 13 minute FET cycle testing, the impactors and ovens
were maintained at about the average exhaust gas temperature for
the cycle, 175°C.
In addition to the cascade impactors, a Thermosystems Model
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BLOWER
EXHAUST
FOR ENGINE
COOLING
STANDARD
EXHAUST
SYSTEM TO
JUNCTION
DYNAMOMETER
ROLLERS
I
-I I-
I I
J I.
SEDS
EAA
::n
OPTICAL
COUNTER
HEAT TRACED
SAMPLE LINE
OVEN FOR
IMPACTORS
AND FILTERS
MODIFIED EXHAUST
"PIPE
FLEXIBLE PIPE
OUTSIDE OF
BUILDING
4181-288
Figure 1. Modified exhaust pipe and test equipment layout for
diesel emission testing.
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3030 Electrical Aerosol Analyzer (EAA) was used to determine
concentrations and size distributions of particles in the size
range of 0.01 ym to 0.5 ym. Particle concentrations ranging
from 0.3 ym to 2.5 ym were monitored using a Royco Model 225
optical particle counter. The Southern Research Institute
SEDS III sample extraction, conditioning, and dilution system
was used as an interface between the exhaust system and the EAA
and particle counter. This system provides a mechanism for the
removal of condensible vapors from the sample gas stream at ele-
vated temperatures followed by quantitative dilution to particle
concentrations within the operating ranges of the measurement
instruments.
The initial intent of the test program was to collect
particle samples at a number of points between the exhaust
manifold and the tailpipe in order to provide specimens col-
lected over a range of temperatures and engine loads. These
data were to have provided information on changes in particle
size distribution and composition as the exhaust gases were
cooled. Unfortunately, time limitations in preparing for and
performing the tests precluded carrying out the proposed plan.
Although it was found that a considerable swing in exhaust gas
temperature did occur with changes in engine load, it proved
impossible to differentiate between load/speed induced and
temperature induced concentration and composition changes in
the data obtained during this test.
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SECTION 3
TEST RESULTS
Overall particulate loadings, engine gas flows, and sampling
temperatures for the cascade impactor samples are given in Table
I. Particle size distributions for the various conditions are
given in Figures 2, 3, 4, and 5. Each figure in this series
contains a plot of cumulative percentage smaller than the indi-
cated diameter versus diameter from the impactor data alone and
that obtained by integrating the distributions from the electrical
aerosol analyzer up to 0.5 ym and continuing the integration
from 0.5 ym to 10 ym with the impactor data. A particle density
of 1.0 g/cm3 was assumed for the integrations of the EAA data.
The overall size distributions from 0.01 ym to 10 ym obtained
in this fashion agree very well with those obtained from the
impactors alone.
The variability in particulate concentrations through the
FET cycle is illustrated in Figure 6. This shows particle con-
centrations versus time in three particle size intervals through
several test cycles. These data were obtained using the optical
particle counter.
Figure 7 is an electron micrograph of diesel parti-
culate collected on the backup filter of one of the Andersen
impactors. These figures clearly show the branched, chainlike
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TABLE I. RESULTS OF CASCADE IMPACTOR SAMPLING
oo
Average exhaust
Average exhaust
temperature at
Aerodynamic
mass median
Operating volume flowrate sampling location
mode (m3/s) (°C)
FET cycle
97 kmph
56 kmph
(with load)
56 kmph
(no load)
0.051
0.057
0.033
(Not Available)
177
218
149
129
Particulate
loading (mg/NCM)
68
55
45
39
particle diameter
(umA)
0.26
0.54
0.46
0.33
-------
99.99T
99.8
5
99
98
95
90
80
70
50
40
30
10
5
B
0.5
olli
0.05^
0.01
. IMPACTOR
ONLY
INTEGRATION OF
EAA (0.01-0.5) AND IMPACTOR
(0.5-10)
10
rE
I I I IHI| 1 III Mll| 1 1 I I I l!l|
10
ri
10P
101
PARTICLE DIAMETER (MICROMETERS)
3858-6
Figure 2. Particle size distribution for FET-cycle.
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LJ
U
LY
y
.ATIVE 1
_i
LJ
99.99
RR.RS
9979
99.8-
99.5-
99-
98-
95-
90-
80^
70-
BO1-
50^
40 i
30 i
EO]
10 ]
5:
ET
li
0.5^
O.E:
o.oi:
1C
i
1- «
I""
1 tf
: T ti
- T ^r
1- IMPACTOR ***
ONLY .*
: * INTEGRATION OF EAA (0.01-0.5 pirn)
L i** AND IMPACTOR (0.5-10 /urn)
i
i.
:
.
rE lo'1 10° lo1
PARTICLE DIAMETER (MICROMETERS)
3858-5
Figure 3. Particle size distribution for 56 kmph no load condition.
10
-------
99.99-
zjzj . y -
99. B -
99.5-
99-
98-
95:
90^
80^
701
601
50 i
401
301
20 1
10^
5:
Ei
±1
«
Biii
^^X fl ^^X ^^j
OoOi4
B
:
1
K
: i
1
Tjl 1-
r IMPACTOR ONLY^ ^lli
1 V1
: it1
«
: 1
i- 0»f
: *
; * INTEGRATION OF EAA (0.01-0.5 ptn
' *" AND IMPACTOR (0.5-10 urn)
\
' *
c
A
10"5 10"1 10° 1C
PARTICLE DIAMETER (MICROMETERS)
3858-4
Figure 4. Particle size distribution for 56 kmph with load condition.
11
-------
1-
e
CL
>
H
H
_J
*
99.99-
991 B:
99.5-
99 ^
98 ^
95:
901
80^
70 -i
50 \
50 4
401
z?1
1
10 1
li
0.5^
O.E^
n.n-i -
^
: < i
! i
: I
i i.
«
;*
" IMPACTOR ONLY *9*»
\ ^jt
I ^_____INTEGATION OF EAA (0.01-0.5 Aim)
AND IMPACTOR (0.5-10 A/m)
0
;
:
*i j i < i H ii i 1 1 1 1 H i-i i i 1 1 1 1 1 i-i
10'
10
rl
10°
101
PARTICLE DIAMETER (MICROMETERS)
3858-3
Figure 5. Particle size distribution for 97 kmph condition.
12
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ROYCO DIESEL FET CYCLE W/LOAD 11/30
9-10:40
CO
o
x
V)
8
1 1 1
CHANNEL 5
^^
__
_
O
r o *
- * * *
' § e 1
i i i
i i i i i i
CHANNEL 1 0.36-0.63 pn CYCLE
CHANNEL 3 0.9-1.1 fJm NO.
CHANNEL 5 1.2-2.0 (Jm 1
2
3
A 4
<7 " 5
0 6
* 7
8
6
0 0 A
O
<7 °
i ' I
* 1
I I I II I
1 1 1
START
TIME SYMBOL
8:58 O
9:11 O
9:24 tf
9:37 &
9:50
10:02
10:15 9
10:28 A
* V
8
? i °
A
1 1 1
^" *
_
__
_
n0
14
12
10
x 8
o
4
2
0
150
i
125
°100a
x
00 .,_
I- 75
D
8 50
25
CHANNEL 1
1 1
i !
ft
i
i
6 7 8 9
CYCLE TIME, min
1 1 1 1 1 1
CHANNEL 3
v a
e
0
1 * O
" 5 7 9 6
A * "
,
1 1 1 1 1 1
_
O
A
° B . -
« 25°
- 1 l « -
i i i i i i
» a
8 « 1 8 s
10 11 12 13
Figure 6. Relative concentration versus time for three particle size
ranges during several FET cycles.
13
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3858-1
Figure 7. Electron micrograph of diesel paniculate.
14
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structure which gives rise to the low bulk density associated
with diesel particulate. The very small primary particle size
is also evident in Figure 7.
The particulates collected at exhaust gas temperatures
were found to be approximately 15 percent by mass organics. The
results of the biotesting of the samples from the impactors,
filters, and organic vapor traps will be reported elsewhere.
15
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SECTION 4
CONCLUSIONS
Typical particulate concentrations at exhaust line con-
ditions for the Oldsmobile 350 CID diesel engine were found to
be about 50 mg/NCM. Aerodynamic mass median diameters were
about 0.3 to 0.5 ym with the larger median diameters being
obtained from higher engine speed/load conditions under steady
state operating conditions. The results reported here are
qualitatively similar in size distribution to those found by
other investigators in measurements of emissions from heavy duty
diesel engines insofar as the impactor data are concerned.2'3
Additional particle size and composition data are required
under conditions where the engine speed and load can be main-
tained at a constant value while the exhaust gas temperature
is varied. This data would determine the suitability of par-
ticle collection at exhaust gas temperatures and would help
define the need for cooling the collection device.
16
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SECTION 5
REFERENCES
1. Blacker, S. M. EPA Program to Assess the Public Health
Significance of Diesel Emissions. Journal of the Air Pol-
lution Control Assoc. Vol 28, page 769, August 1978.
2. Lipkea, W. H., J. H. Johnson, and C. T. Vuk. The Physical
and Chemical Character of Diesel Particulate Emissions -
Measurement Technique and Fundamental Considerations. SAE
Paper #780108, presented at the SAE Congress and Exposition,
Detroit, Michigan, February 27-March 3, 1978.
3. Springer, K., and R. Stahman. Removal of Exhaust Particulate
from a Mercedes 300D Diesel Car. SAE Paper #770716, pre-
sented at the SAE Off-Highway Vehicle Meeting and Exhibition,
Mecca, Milwaukee, Wisconsin, September 12-15, 1977.
17
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-600/7-79-232c
2.
3. RECIPIENT'S ACCESSION-NO.
4. TITLE AND SUBTITLE
Assessment of Diesel Particulate Control: Particle
Size Measurements
5. REPORT DATE
December 1979
6. PERFORMING ORGANIZATION CODE
SORI-EAS-79-778
7. AUTHOR(S)
8. PERFORMING ORGANIZATION REPORT NO.
Joseph D. McCain and M. Gregory Faulkner
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Southern Research Institute
2000 Ninth Avenue, South
Birmingham, Alabama 35205
10. PROGRAM ELEMENT NO.
EHE624A
11. CONTRACT/GRANT NO.
68-02-2610, Task 8
12. SPONSORING AGENCY NAME AND ADDRESS
EPA, Office of Research and Development
Industrial Environmental Research Laboratory
Research Triangle Park, NC 27711
13. TYPE OF REPORT AND PERIOD CO\
Task Final; 11/78 - 11/79
COVERED
14. SPONSORING AGENCY CODE
EPA/600/13
is.SUPPLEMENTARY NOTES jERL-RTP project officer is Dennis C. Drehmel, Mail Drop 61,
919/541-2925.
16. ABSTRACT
The report gives results of tests on an Oldsmobile 98 dies el automobile to
obtain data on parameters typical of a light duty vehicle. Data are presented for
operations under four simulated driving conditions. (The increasing appearance of
the diesel engine on the passenger car market has led to concern over particulate
emissions (smoke) from these engines. Possible control strategies involving parti-
culate collection in the hot exhaust stream requires knowledge of the concentrations
and size distributions of the particulate matter at exhaust conditions.) Typical parti-
culate concentrations at exhaust line conditions for the 350 CID diesel engine were
found to be about 50 mg/Ncm. Aerodynamic mass median diameters were about 0.3
to 0. 5 micrometers with the larger median diameters from higher engine speed/load
conditions under steady state operation. Test results are qualitatively similar in
size distribution to those found by other investigators in measurements of emissions
from heavy duty diesel engines insofar as the impactor data are concerned. Addi-
tional particle size and composition data are required under conditions where the
engine speed/load can be maintained at a constant value while the exhaust temper-
ature is varied. This data would determine the suitability of particle collection at
exhaust gas temperatures and would help define collection device cooling needs.
7.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
c. COS AT I Field/Group
Pollution
Dust
Smoke
Aerosols
Diesel Engines
Automobiles
Exhaust Gases
Pollution Control
Particulate
13B
11G
21B
07D
21G
13 F
8. DISTRIBUTION STATEMENT
Release to Public
19. SECURITY CLASS (This Reportf
Unclassified
21. NO. OF PAGES
23
20. SECURITY CLASS (Thispage)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
18
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