United States
Environmental Protection
Agency
Air and Energy Engineering
Research Laboratory
Research Triangle Park NC 27711
Research and Development
EPA/600/S7-86/002 Apr. 1986
&EPA Project Summary
Environmental Assessment of
NOX Control on a Spark-Ignited,
Large-Bore, Reciprocating
Internal-Combustion Engine
C. Castaldini
This two-volume report gives emis-
sion results for a spark-ignited, large-
bore, reciprocating, internal-combustion
engine operating both under baseline
(normal) conditions, and with combus-
tion modification controls to reduce
NOX emissions to levels below the pro-
posed new source performance stan-
dard (NSPS) for such engines. Exhaust
gas measurements (in addition to con-
tinuous monitoring of criteria gas
emissions) included total organics in
two boiling point ranges, compound
category information within these
ranges, specific quantitation of the
semivolatile organic priority pollutants
(POMs), flue gas concentrations of 73
trace elements, and particulate matter.
Exhaust NOx emissions were reduced
almost 50 percent, from a baseline level
of 1,260 ng/J to 654 ng/J (730 to 420
ppm, corrected to 15 percent O2 dry) by
increasing the operating air/fuel ratio
of the engine. Accompanying this re-
duction was a slight increase in engine
efficiency. CO, methane, total hydro-
carbon, and total semivolatile organic
compound emissions were increased
from 10 to 65 percent under low-NO*
operation. However, total nonvolatile
organic emissions decreased 55 per-
cent. The organic emissions for both
tests consisted primarily of aliphatic
hydrocarbons with some carboxylic
acids, phenols, and low-molecular-
weight fused-ring aromatics. POMs
were detected in concentrations below
4 /^g/dscm.
This Project Summary was developed
by EPA's Air and Energy Engineering
Research Laboratory, Research Triangle
Park, NC, to announce key findings of
the research project that is fully docu-
mented in two separate volumes of the
same title (see Project Report ordering
information at back).
Introduction
This report describes emission results
obtained from field tests of the exhaust
gas from a spark-ignited, large-bore,
reciprocating, internal-combustion en-
gine. Objectives of the tests were to
measure exhaust gas emissions and
evaluate the operating efficiency of the
engine, both under baseline (normal)
operating conditions, and with combus-
tion modification controls to reduce NO,
emissions to levels below the proposed
new source performance standards
(NSPS) for such engines. Emission
measurements included continuous
monitoring of exhaust gas emissions;
source assessment sampling system
(SASS) sampling of the exhaust gas with
subsequent laboratory analysis of sam-
ples to give total flue gas organics in two
boiling point ranges, compound category
information within these ranges, specific
quantitation of the semivolatile organic
priority pollutants, and flue gas concen-
trations of 73 trace elements; and Method
5 sampling for particulate.
Exhaust NOx emissions were reduced
almost 50 percent, from a baseline level
of 1,260 ng/J to 654 ng/J by increasing
the operating air/fuel ratio of the engine.
Accompanying this reduction was a slight
increase in engine efficiency. CO, meth-
ane, total hydrocarbon, and total semi-
volatile organic compound emissions
-------
were increased from 10 to 65 percent
under Iow-N0x operation. However, total
nonvolatile organic emissions decreased
55 percent. Emissions of anthracene/
phenanthrene and chrysene/benz(a)
anthracene were 3 to 4 /ug/dscm for both
tests; levels of other ROMs were less than
detectable (2 /ug/dscm). The organic
emissionsfor both tests consisted primar-
ily of aliphatic hydrocarbons with some
carboxylic acids, phenols, and low-
molecular-weight fused-ring aromatics.
Summary and Conclusions
Test Engine
The test engine was a large-bore,
turbocharged, 1,120-kW (1,500-Bhp)
two-stroke, opposed-piston spark-ignited
Model 37TDSB-1 /8 engine manufactured
by the Fairbanks Morse Engine Division
of Colt Industries. Figure 1, a schematic of
the engine, shows the turboblower ar-
rangement for the inlet combustion air
and the opposed piston design. The
combustion air is drawn into the turbo-
charger, where it is compressed and
discharged through an air cooler to the
positive-displacement lobe-type blower.
The blower, driven by the upper engine
crankshaft, discharges the air directly to
the cylinders through the engine intake
manifold. The air/fuel mixture is com-
pressed between the two pistons which
work vertically toward each other in each
cylinder. The upper and lower pistons
drive separate crankshafts interconnected
by a vertical drive. Hot exhaust gas from
the lower cylinder ports drives the turbine
of the turbocharger assembly. The fuel is
ignited by spark ignition cells, arranged
two per cylinder.
Engine Operation and
Test Arrangements
The test program called for the analysis
of flue gas samples collected during
normal operation (baseline conditions)
and with combustion modifications ap-
plied to lower NO* emisisons. Table 1
summarizes the engine specifications and
operating parameters during both the
baseline and Iow-N0x tests.
Since this engine design is usually
marketed without the turbocharger and
manifold air cooler existing on the test
engine, it was necessary to reduce the
effect of turbocharging during the base-
line test. To reduce the effect of turbo-
charging, a portion of the combustion air
was bypassed around the manifold air
cooler. The resulting increase in combus-
tion airtemperature lowered the air mass
Upper
Crankshaft
Compressor
(1st stage)
Blower
(2nd stage
in series)
Exhaust
Outlet
Figure 1. Schematic of turboblower arrangement (courtesy of the Fairbanks Morse Division of
Colt Industries).
flowrate, giving an air/fuel ratio which is
more representative of the blower-
scavenged design. The percent bypass air
during the baseline tests was 16.4 per-
cent, determined by the air flow control
limits available on this test engine. Thus,
baseline operation was as representative
of normal blower-scavenged engine
operation as could be achieved with the
turbocharger in place.
The low-NOx operation consisted of
increasing the air/fuel ratio by elimina-
ting the manifold air cooler bypass used
during the baseline test and increasing
the efficiency of the inlet manifold cooler.
This modification reduced the inlet air
temperature as well as increasing the
air/fuel ratio. Engine power output was
maintained nearly constant by decreasing
fuel flow, while efficiency increased by
about 0.4 percent during the Iow-N0x
test.
Emission Measurements and
Results
The sampling and analysis procedures
used in this test program conformed to a
modified EPA Level 1 protocol. Except for
continuous monitoring of exhaust gas
emissions, all exhaust gas was measured
at the engine muffler exit into the un-
insulated exhaust stack. Emissions
measurements included:
• Continuous monitoring for NOX, NO,
CO, CO2, 02, TUHC, and CH4
• Source assessment sampling system
(SASS) for trace element and organic
emissions
• EPA Method 5 sampling for solid and
condensable particulate mass emis-
sions
• Grab sampling for onsite analysis of Ci
to Cs hydrocarbons by gas chroma-
tography
• Bosch smoke pot
In addition, samples of the engine lube oil
were collected for analysis.
• Analyzing the lube oil and SASS train
samples for 73 trace elements using
spark source mass spectrometry
(SSMS), supplemented by atomic ab-
sorption spectrometry (AAS)
-------
Ttble 1. Spark Engine Design and Operating Parameters
Design Parameters
(Engine Specifications)
Model designation
Configuration
Bore, m tin.)
Stroke, m (in.)
No. of cylinders
Displacement/cylinder m3 (in.3)
Compression ratio
BMEP, kPa (psi)
Power/cylinder at rpm, kWt (Bhpl
Spark timing
Lubricating oil
Hours since overhaul
Operating Parameters
38TDS8-1/8
2 stroke, O.P.
0.206(8-1/8)
0.254 (10) x 2
6
0.017(1037)
9.7:1
731 (106)
186 (250) at 900
4.5° before minimum
volume (BMV)
Pegasus 485
1050
Baseline
/V0« Control Test
RPM (percent rating)
KWt (Bhp) (percent rating)
kW, (percent rating)
BMEP, kPa (psi)
Fuel flow, m3/hr(ft3/hr)
BSFC. g/kW-hr (Ib/Bhp-hr)
Fuel rate, kW fuel/kW out (Btu/Bhp-hr)
Ignition timing
Compressor inlet air temp., K (°F)
Compressor outlet air temp.. K (°F)
Manifold air cooling bypass, percent
Blower suction air temp., K (°F)
Blower discharger air temp., K (°F)
Blower discharge pressure, kPa (psig)
Air flow, kg/s (Ib/min)
Fuel-air ratio
Combined cylinder exhaust temp., K (°F)
Turbine exhaust temp., K (°F)
Lube oil consumption, ml/s (gph)
Engine efficiency, percent
900(100%)
1,117(1,498)
(99.8%)
1.085 (97.8%)
731 (106)
354 (12.492)
217(0.356)
2.91 (7413)
4.5° BMV
302 (85)
356(181)
16.4
331 (136)
345(161)
60(8.7)
2.56(338.3)
0.0271
732 (858)
652 (715)
0.45 (0.43)
34.3
900 (100%)
1.123(1,505)
(100%)
1.091 (98.9%)
731 (106)
352 (12.426)
215(0.353)
2.88(7340)
4.5° BMV
302 (85)
359 (187)
0
316(110)
337(146)
71 (10.3)
2.90(383.4)
0.0240
699 (799)
617(652)
0.45 (0.43)
34.7
Average Ambient Atmospheric Conditions
Outdoor temp, dry bulb. K (°F) 281 (46)
Barometric pressure, kPa (in. Hg) 98.2 (29.08)
Humidity, percent 60
284(51)
98.6(29.20)
62
• Analyzing SASS train samples for total
organic content in two boiling point
ranges: 100 to 300°C by total chro-
matographable organics (TCO) analysis
and >300°C by gravimetry (GRAV)
• Analyzing the SASS train sorbent
module extract for 58 semivolatile
organic species including many POM
compounds
• Performing infrared (IR) spectrometry
analysis of organic sample extracts
• Performing liquid chromatography(LC)
separation of selected sample extracts
with subsequent TCO, GRAV, and IR
analyses of LC fractions
• Performing direct insertion probe and
batch inlet low resolution mass spec-
trometry (LRMS) of selected sample
extracts
Bioassay tests were also performed on
the exhaust sample SASS organic sorbent
module extract to estimate this sample's
potential toxicity and mutagenicity.
Table 2 summarizes exhaust gas emis-
sions measured in the test program.
Emissions are presented in both ng/J
heat input and as mg/dscm of exhaust
gas.
As noted in Table 2, NO* emissions
were decreased under Iow-N0« operation
to 654 ng/J from a baseline of 1,260
ng/J. This decrease in NO* emissions
was accompanied by increases in all
relatively volatile combustible emissions,
CO, TUHC, ChU, and total semivolatile
organics, although nonvolatile organic
emissions decreased. Emission levels of
the inorganic elements noted in Table 2
were relatively unchanged in going to
low-NOx operation from the baseline
condition.
As a measure of the potential signifi-
cance of emission levels for further
monitoring and evaluation. Table 2 also
lists occupational exposure guidelines for
most pollutants in the table. The guide-
lines listed are generally either the time-
weiflhted-average Threshold Limit Values
(TLV) established by the American Con-
ference of Governmental Industrial
Hygienists, or the 8-hour time-weighted-
average exposure limits estabalished by
the Occupational Safety and Health
Administration. These are noted only to
aid in ranking emissions for further
evaluation. In this respect, species emit-
ted at levels several orders of magnitude
higher than their guideline might warrant
further consideration. Species emitted at
levels significantly lower than their oc-
cupational exposure guideline might be
considered of lesser concern. Only ele-
ments emitted at levels exceeding 10
percent of their guideline are noted in
Table 2.
Table 2 shows that the only pollutants
emitted at levels which exceeded their
respective guidelines were N0>, CO, and
Cu in the baseline test and NO,, CO, Cu,
Fe, and Cr in the Iow-N0x test. The trace
elements were emitted at levels at most a
few times higher than their guidelines. In
contrast, the criteria pollutants CO and
NOx were present in the exhaust at levels
of almost one (CO) to well over two (NO,)
orders of magnitude higher than their
guidelines. This suggests that NO* emis-
sions achieved may be the most signifi-
cant change.
Analyses of SASS train samples for
POM and other organic compounds (the
semivolatile organic priority pollutant
species) were performed. Only anthra-
cene/phenanthreneandchrysene/benz-
(a)anthracene isomers were detected at
levels above 2 /yg/dscm. These were
present at 3 to 4 //g/dscm levels for both
tests.
SASS train organic extract samples
were subjected to LC fractionation with
TCO, GRAV, IR, and LRMS analysis of LC
fractions in attempts to elucidate the
chemical character of the exhaust gas
organic material. These analyses sug-
-------
Table 2. Summary of Flue Gas Emissions"
Baseline Test
Low-NO» Test
Compound
Per Heat
Input
(ng/J)
Average
Concentration
(mg/dscm)
Per Heat
Input
(ng/J)
Average
Concentration
(mg/dscm)
Occupational
Exposure
Guideline"
(mg/dscm)
Criteria Pollutant and
Other Vapor Species
NO, (as /VOW
CO
CH<
TUHC(asC3Hei
Solid paniculate
Condensable paniculate
Total chromatographabale
organicsfC-i -Cw)
Total nonvolatile organics
1.260
120
293
960
12.5
7.3
1.3
35
1,900
198
480
1,600
20
12
2.1
57.8
654
198
323
1,100
16.2
7.5
1.6
15
976
295
482
1,640
24.2
11.2
2.4
22.1
6.0
55
10.0"
Trace Elements
Copper, Cu
Iron, Fe
Chromium, Cr
Phosphorus, P
Silver, Ag
Potassium, K
Sodium, Na
Lead, Pb
Calcium, Ca
Selenium, Se
Cobalt, Co
Nickel, Ni
0.15
—
0.0/3
0.0067
0.0010
>0.48
>0.48
0.012
0.35
0.035
—
0.0014
0.25
_ e
0.022
0.011
0.0017
>0.80
>0.80
0.020
0.59
0.059
—
0.023
0.18
1.1
0.053
0.060
0.0046
>0.66
>O.54
0.0074
0.18
0.023
0.018
0.0013
0.27
1.6
0.079
0.090
0.0068
0.98
0.80
0.011
0.27
0.034
0.027
0.00/9
O./O"
1.0
0.050
0.10
0.010
2.0'
2.0"
0.050"
2.0
0.20
0.10
0.10
"Exhaust Oz and COz levels were 12.1 and 4.9 percent, respectively, for the baseline test and 13.2 and4.4 percent, respectively, for the low-NO, test.
"Time-weighted-average, TLV, unless noted.
"For nuisance paniculate.
"8-Hr time-weighted-average OSHA exposure limit.
'Dashes indicate the pollutant was not quantifiable.
'Ceiling limit.
gested that the exhaust gas organic for
both tests was primarily aliphatic hydro-
carbons, with some carboxylic acids,
phenols, and low-molecular-weight
fused-ring aromatics (e.g., naphthalene
and alkyl naphthalenes).
Health effects bioassay tests were
performed on the organic sorbent (XAD-
2) module extract from the SASS trains
for both the baseline and the low-NOx
tests. The bioassay tests performed were
the Ames mutagenicity and the CHO
cytotoxicity assay. The results of these
assays are summarized in Table 3 for the
exhaust gas sample (organic sorbent
module extract from the SASS train) for
both the baseline and Iow-N0x tests. The
results suggest that the exhaust gas
under both baseline and Iow-N0x opera-
tion is of moderate to high toxicity and
mutagenicity. This is a typical bioassay
response for combustion source XAD-2
extract.
Table 3. Bioassay Analysis Results
Bioassay Analysis
Sample Test
CHO"
Ames
XAD-2
Extract Baseline H/M H
XAD-2
Extract ' Low-NO, H/M M
*H = high toxicity; M - moderate toxicity.
"H = high mutagenicity;
M = moderate mutagenicity.
U. S. GOVERNMENT PRINTING OFFICE: 1986/646-116/20798
-------
C. Castaldini is withAcurex Corp., Mountain View, CA 94039.
Robert E. Hall is the EPA Project Officer (see below).
The complete report consists of two volumes, entitled "Environmental Assess-
ment of /VO, Control on a Spark-Ignited, Large-Bore, Reciprocating Internal-
Combustion Engine:"
"Volume I. Technical Results," (Order No. PB 86-156 809/AS; Cost: $16.95)
"Volume II. Data Supplement," (Order No. PB 86-156 817/AS; Cost: $16.95)
The above reports will be available only from: (cost subject to change)
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Air and Energy Engineering Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC27711
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
\*>«AXTy U.S,POSfflGt" i-
Official Business
Penalty for Private Use $300
EPA/600/S7-86/002
0000329 PS
AGENCY
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