79-8
Evaluation of Exhaust Collection Configuration
on Diesel Particulate Measurement
May 1979
Thomas Penninga
Technology Assessment and Evaluation Branch
Emission Control Technology Division
Office of Mobile Source Air Pollution Control
Environmental Protection Agency
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Background
On February 1, 1979 the EPA published proposed rules regulating parti-
culate emissions for light-duty diesel vehicles. Section 86.110-81(b)(3)
describes the proposed exhaust collection configuration to be used in
transferring the exhaust gas from the vehicle tailpipe to the dilution
tunnel. The proposed regulation reads as follows:
86.110-81(b)(3)
The transfer of heat from the vehicle exhaust gas shall be minimized
between the point where it leaves the vehicle tailpipe(s) and the
point where it enters the dilution tunnel (not more than 12 feet
(365 cm) airstream. To accomplish this, a short length of stainless
steel tubing from the tailpipe to the dilution tunnel is required.
This tubing shall have a maximum inside diameter of 4.0 in. (10.2
cm). Short sections of flexible tubing at connection points are
allowed.
i
Questions both internal and external to EPA concerning the practicality
and necessity for these requirements resulted in the initiation of a
testing program to evaluate the effect of the following parameters on
diesel exhaust particulates:
1. Diameter of the exhaust collection configuration,
2. Length of the exhaust collection configuration,
3. Shape or number of bends in the exhaust collection configuration,
4. Internal smoothness of the exhaust collection configuration,
5. Temperature of the exhaust collection configuration.
Test Procedure
The test data was run according to the proposed Federal Register require-
ments for both FTP and HFET cycles. The two test vehicles were a 1975
Mercedes Benz 300D and a 1979 Oldsmobile 350 CID Diesel. A better
description of the two vehicles is given in Table 1.
Five different configurations of exhaust collection hardware were /
tested. The two vehicles were tested twice in each configuration. The
configurations are described as follows:
Configuration #1: Twelve feet of convoluted, 2 1/2" diameter pipe,
one 90 bend.
Configuration #2: Thirteen feet of convoluted, 2 1/2" diameter pipe,
three 90° bends.
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Configuration #3: Twenty feet of convoluted, 2 1/2" diameter
pipe, one 90 bend.
Configuration #4: Twelve feet of convoluted, 4" diameter pipe, one
90° bend.
Configuration #5: Twelve feet of smooth pipe, 2 1/2" diameter, one
90 bend, insulated.
Baseline Data
Previous testing programs had established a baseline particulate emission
number for each vehicle. The baseline exhaust collection configuration
was twelve feet 2 1/2" diameter smooth pipe with one 90° bend. The FTP
test results used to determine the baseline are presented below:
Mercedes 300D Oldsmobile 350
FTP (gms/mile) HFET FTP (gms/mile) HFET
.434
.423
.425
.409
.419
Average: .422 gms/mile Average: .982 gms/mile
Average of .439 .316 .859 .458
this study
Test Results
All of the individual FTP and HFET tests results are tabulated in Table
2. The average FTP and RFET results for each configuration were calculated
and compared to both the baseline data average, if available, and to the
average result of this study. No baseline HFET data was available.
The average results and percent deviation from the baseline and study
averages is as follows:
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Mercedes 300D
Oldsmobile
FTP
Configuration #1
Average .404
% Dev. from Baseline (-) 4.27%
% Dev. from Study Ave. (-) 7.97%
Configuration #2
Average .447
% Dev. from Baseline (+) 5.92%
% Dev. from Study Ave. (+) 1.82%
HFET
.306
.3375
(+)6.89%
Average . 386
% Dev. from Baseline (-) 8.65%
% Dev. from Study Ave. (-)12.19
Average . 452
% Dev. from Baseline (+) 6.99%
% Dev. from Study Ave. (+) 2.85%
Average .4905
% Dev. from Baseline (+)16.23%
% Dev. from Study Ave. (+)11.73%
FTP
.854
(-)3.60%
HFET
.462
..87%
.872 .478
.20%
(-) 1.57% (+)4.37%
.837 .423
(-) 5.52% (-)7.64%
.910 .464
(-) 7.28%
(+) 2.78% (+)1.42%
.949 .4755
(-) 3.36%
(+) 7.12% (+)3.82%
Configuration #3
.288
(-)8.79%
Configuration #4
.328
(+)3.88%
Configuration #5
.3235
(+)2.46%
Attached are graphical representation of this tabulated data.
Rejected .Data .
Two tests on the Oldsmobile were considered to be invalid because the
data was so removed from the norm. This data was an FTP value of 1.734
grams/mile and a HFET value of .027 grams/mile.
Temperature Data
Midway through the test program it was requested that temperature data
be taken at the inlet to the dilution tunnel. Graphical presentation of
the temperature data is not available for the 20 foot length of collection
tubing (configuration No. 3). The relationship between temperature at
the tunnel entrance is not a simple relationship as the temperature
varies during the test. It is true, however, that the highest mass
particulate values were noted in the highest average temperature con-
figuration.
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Conclusions
There appears to be direct correlation between collection configurations
and mass parti'culate emissions. It should be noted that the same trends
occur on each vehicle as displayed in the graphs. These graphs clearly
show that the results are significant and repeatable.
1. Differences in collection pipe configuration have a larger
effect on vehicles with lower exhaust volume flow rate. Thus the
Mercedes 300D was more effected by exhaust collection configuration
than the Oldsmobile. The Mercedes Benz showed a maximum of 24.88%
delta and the Oldsmobile showed a maximum of 13.04%.
2. Convoluted Exhaust Pipe results in lower particulate emissions
than smooth pipe.
3. A 4" diameter pipe results in higher particulate emissions
than a 2*2" diameter pipe.
4. A twenty foot 2^" diameter pipe results in lower particulate
emissions than a twelve foot length.
5. An insulated exhaust collection system results in higher
particulate emissions than uninsulated systems.
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Table 1
Test Vehicle Description
Model Year
Make
Emission Control System
Type
Bore x Stroke
Displacement
Rated Horsepower
Transmission
Axle Ratio
Chassis Type
Tire Size
Inertia Weight
VIN
Oldsmobile
1978
Delta 88
None
V-8, Diesel
4.06 x 3.39
350 CID
120
A-3
2.41
Sedan
FR78xl5
4500
3N69N8M153542
Mercedes 300D
1975
300D
None
1-5, Diesel
3.58 x 3.64
3.00 litre
77
A-4
3.46
Sedan
175 SR14
4000
11511412019885
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Table 2
Tabulated Test Results
Configuration Mercedes Oldsmobile
FTP HFET FTP HFET
#1 .404 .280 .812 .027*
//I VOID .333 .896 .462
n .452 .339 .872 VOID
#2 .442 .326 1.734* .478
#3 .396 .298 .864 .433
#3 .375 .278 .810 .413
#4 .493 .332 .946 .478
//4 .410 .324 .875 .451
#5 .528 .358 .918 .476
#5 .453 .289 .980 .475
*Rejected Data
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