71-30
Exhaust Emission Analysis of the
Williams Research Gas Turbine Volkswagen
May 1971
Leonard D. Verrelli
Bureau of Mobile Source Pollution Control
Office of Air Programs
ENVIRONMENTAL PROTECTION AGENCY
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Vehicle Tested
The Williams Gas Turbine, 131-Q, regenerative turbine auto-
motive engine was mounted in a 1965 Volkswagen squareback
test bed. The engine utilizes a two stage turbine to
develop 70 horsepower. It incorporates the standard VW
automatic transmission coupled to the engine through a gear
reduction system. Non-leaded gasoline was used as fuel for
these tests.
Test Conducted
The standard 1972 Federal test procedure using the LA 4-S4
driving cycle with constant volume sampling was used.
The 1200 cfm CVS used for this test was modified slightly
by blocking off the CVS filters and drawing dilution air
from the room with mixing occurring at the vehicle exhaust
outlet.
Oxides of nitrogen were measured using both the wet chemical
modified Saltzman technique and the chemiluminescence
instrument. Carbon monoxide was measured using non-dispersive
infrared and hydrocarbons were determined using both the
cold and hot flame ionization detector. Concentrations of
all pollutants were measured in the CVS bag and hydrocarbon
concentration was monitored continuously in the raw exhaust
using the hot flame ionization detector.
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Emission Results
The normal practice of subtracting the concentration of the
background hydrocarbons in the dilution air from the hydro-
carbon concentration measured in the CVS bag could not be
used in this study. When sampling from low emission
vehicles the hydrocarbons in the dilution air can contribute
a major portion of the total hydrocarbons and the straight
subtraction correction is no longer rigorous. Since the
volume flow of the engine was known an alternate more
correct calculation procedure could be used.
The concentration (Ct) of the diluted sample in the CVS bag
can be expressed as follows: !
Ct = Ce Y^ + Cb ^ "' Ve (!)
Vt Vt
Where:
Ct = concentration of total sample in bag
Ce = concentration of integrated undiluted exhaust
volume
Cb = concentration of background contaminant dilution
air
Vt = volume of total sample (exhaust plus dilution air)
Ve = volume of exhaust
Equation (1) can be rearranged solving for concentration
of exhaust (Ce):
Vt - Ve
Ce = (Ct - Cb —ITT -)
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The weight of emission (gm/mi) of each pollutant is obtained
from:
W = K Ce
Where: K = constant relating weight of emission
to volume of exhaust per mile
Ve = volume of exhaust per mile
Four LA 4-S4 tests were run, there was one aborted test
because of a leaking exhaust manifold. There is some
question to the validity of test #1 due to suspected sample
contamination.
In Table 1 comparisons are made of all three tests using
!
the 1972 Federal test procedure. . Hydrocarbons in tests #2
and #3 are consistent, but in test #1' the value is consider-
ably higher possibly reflecting the hydrocarbon contamination
mentioned above. Carbon monoxide data is inconsistent, and
nitrogen oxides also show a slight inconsistency.
In keeping with report policy for tests such as these
oxides of nitrogen will be reported as N02 and an overall
value will be arrived at by averaging two sets of data.
Conclusions
By averaging two sets of data it was determined that the
test vehicle did meet the 1975 standards; however, it should
be noted that some slight inconsistencies do exist.
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Because a new combustor design had been incorporated in the
engine it was unadvisable at this time to perform a larger
number of tests. Until such a series of tests can be
performed to substantiate the data collected during this
short test, a positive determination of emission levels
cannot be made.
The driveability of this turbine car did not compare to a
conventional internal combustion engine vehicle. Very
little engine retardation was evident; acceleration was
smooth but not rapid.
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Table 1
1972 Federal Test Procedure
HC gpm
CO gpm
C02 gpm
NO gpm
NO 2 gpm
Test #1*
12-1448
.89
1.78
1086.5
1.44
2.21
Test #2
12-1449E
.36
5.4
1094.5
• 1.55
2.30
Test #3
12-1455
.32
3.6
988.4
1.27
1.95
Average of tests #2 and #3:
HG gpm CO gpm NO2 gpm NOX**
.34 4.5 2.12 1.81
NOX corrected for Humidity:
Test #1 Test #2 Test #3
1.92 1.97 1.65
gpm indicates calculated mass in grams per mile.
* not used in calculations because of possible effect from
the sample contamination on emissions;
** NOX corrected for humidity.
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