EPA/AA/CTAB-89-02
Technical Report
Conversion of MethanoI-Fueled 16-Valve,
4-CyUnder Engine to Operation On Gaseous
2H2/CO Fuel - Interim Report II
by
Gregory K. Piotrowski
James Martin
March 1989
NOTICE
Technical Reports do not necessarily represent final EPA
decisions or positions. They are intended to present technical
analysis of issues using data which are currently available.
The purpose in the release of such reports is to facilitate the
exchange of technical information and to inform the public of
technical developments which may form the basis for a final EPA
decision, position or regulatory action.
U. S. Environmental Protection Agency
Office of Air and Radiation
Office of Mobile Sources
Emission Control Technology Division
Control Technology and Applications Branch
2565 Plymouth Road
Ann Arbor, Michigan 48105
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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
ANN ARBOR. MICHIGAN 48105
OFFICE OF
AIR AND RADIATION
APR 24 1989
MEMORANDUM
SUBJECT:
FROM:
TO:
Exemption From Peer and Administrative Review
f^
Karl H. Hellman, Chief
Control Technology and Applications Branch
Charles L. Gray, Jr., Director
Emission Control Technology Division
The attached report entitled, "Conversion of Methanol-
Fueled 16-Valve, 4-Cylinder Engine to Operation On Gaseous
2H2/CO Fuel - Interim Report II," (EPA/AA/CTAB/89-02)
describes progress to date on a project to convert a Nissan
CA18DE engine previously modified for operation on M100 neat
methanol to operation on dissociated methanol (2H2/CO)
gaseous fuel. This engine has been operated, on both M100 and
simulated dissociated methanol (hydrogen and carbon monoxide)
gaseous fuels. This report describes the. modifications made to
the engine and summarizes the results of testing to date.
Further work on this project will be described in a future
technical report.
Since this report is concerned, only with the presentation
of data and its analysis and does not involve matters of policy
or regulations, your concurrence is requested to waive
administrative review according to the policy outlined in your
directive of April 22, 1982.
Concurrence
Date
_^ _ _
cfiTrles L. Gray, j/.,'.Dir., ECTD
Nonconcurrence :
Date
Charles L. Gray, Jr., Dir., ECTD
cc: E. Burger, ECTD
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Table of Contents
Page
Number
I . Summary 1
II. Introduction 2
III. Description of Test Engine 3
IV. Modifications For 2H2/CO Fuel Operation 4
A. Engine Modifications 4
B. Fuel System Modifications 9
V. Exhaust Analysis 10
VI. Results from Testing 11
VII. Project Highlights To Date 17
VI11.Future Effort 18
IX. Acknowledgments 19
X. References 19
APPENDIX A - Test Engine Specifications - A-1
M100 Fuel Operation
APPENDIX B - Air/Fuel Ratio Calculation With B-1
2H2/CO Fuel
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I. Summary
The work described in this report concerns the conversion
of a 16-valve, 4-cyUnder light-duty automotive engine to
operation on a mixture of hydrogen (H2) and carbon monoxide
(CO) gaseous fuel. This engine will be evaluated to determine
the difference in emission levels and lean limit operation
between two different fuels: M100 neat methanol and simulated
dissociated methanol gaseous fuel (2H2/CO). The engine will
eventually be used as a test bed for a practical, onboard
methanol dissociation fuel system.
Modifications made to the test engine to enhance the
characteristics of 2H2/CO fuel are discussed in this report.
A description of the CA18DE test engine modified for use on
M100 neat methanol by Nissan Motor Co., LTD, is also included.
The engine ran very smoothly at idle and under load
conditions with the simulated dissociated methanol 2H2/CO
fuel. Visible engine vibration from gaseous fuel operation was
noticeably reduced from levels experienced with the engine
operating on liquid methanol fuel.
The test engine was able to operate very lean with the
2H2 + CO fuel. The air/fuel (A/F) ratio was computed to be
14.8:1 at no load, 625 rpm and 26.5:1 at no load, 1500 rpm.
When 10.3 BMP was being produced (27.1 ft-lb torque, 2000 rpm),
the A/F ratio dropped to 11.9:1. All of these A/F values are
lean when operation on 2H2 + CO is concerned, since the
stoichiometric A/F ratio is the same as it is for methanol,
6.4:1. The leanest A/F ratio 26.5:1, is much closer to the
stoichiometr ic A/F ratio for H2 (34:1) than it is to that of
CO (2.5:1) so the operation seems to be enhanced by the H2 in
the gaseous fuel.
A direct comparison of emissions test results from the
engine when it was alternately fueled with M100 and 2H2/CO
fuels is not possible at this time. The testing with M100 fuel
utilized a catalytic converter in the exhaust stream while
2H2/CO fuel results are engine-out emissions. The 2H2/CO
fuel emissions test results may vary substantially between
tests because the limited amount of 2H2/CO fuel in the "T"
cylinder storage bottles did not permit starting and warming to
steady-state conditions prior to testing.
Additional emissions testing at various engine speed/load
operating conditions will be conducted to better characterize
the emissions profile of this engine when operated on both M100
and dissociated methanol. A/F ratio under these test
conditions will also be determined.
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11. Introduction
Section 211 of the Clean Air Act [1] requires the U.S.
Environmental Protection Agency (EPA) to play a key role in the
introduction of new motor vehicle fuels. EPA studies [2] have
suggested that methanol stands out from other alternative
transportation fuels from an environmental perspective. The
use of alcohol fuels can also play a significant role in the
reduction of the foreign trade deficit and aid the security
interests of the United States by reducing U.S. dependence on
imported petroleum.[3]
Methanol may be catalyt ical ly decomposed to H2 and CO
gases according to the reaction:
CH3OH( , , 2H2(g) + C0
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In order to assist this program at Ricardo, a project was
begun to convert a methanoI-fueled engine to operation on
2Hz/CO gaseous fuel. The goal of this project was to modify
a 16-valve, 4-cyUnder light-duty automotive engine for use
with 2H2/CO gaseous fuel and to evaluate this engine using
two fuels:
1. 2H2/CO bottled gas (in the same molar proportions
as dissociated methanol, 2H2/CO); and
2. M100 neat methanol (liquid fuel).
The criteria for evaluation was the engine's ability to
run without driveability problems at the lean limit of
operation and emission levels over several steady-state speed
and load conditions. Once the conversion and initial testing
were completed, the engine was to be used as a test engine for
the onboard dissociator under development at Ricardo. This
report contains a summary of the work to date performed to
facilitate conversion to the gaseous fuel, as well as results
from initial testing of the engine on both liquid and gaseous
fuels.
III. Description of Test Engine
The test engine used for this project was a Nissan CA18DE
engine. This engine is an in-line, 4-cyUnder, 1.8-liter
capacity powerplant. The valve arrangement is a 4-valve per
cylinder configuration, consisting of two intake and two
exhaust valves per cylinder. The valves are operated by two
overhead camshafts, one each for the intake and exhaust side.
The stock gasoline-fueled version of this engine has a
compression ratio of 10.0 and a standard compression pressure
of 14.0 kg/cm2 at 350 rpm.
A CA18DE engine was modified by Nissan Motor Company, LTD
to better utilize the qualities of M100 neat methanol, rather
than unleaded gasoline. Metal from the bottom of the head was
shaved in order to increase the compression ratio to 11.0.
Standard compression pressure was raised to 16.5 kg/cm2 at
350 rpm by this modification. A detailed description of engine
specifications from this engine after the modifications made
for methanol compatabiIity is given in Appendix A.
Two external control devices were also added by Nissan as
modifications to the stock engine. The first, an air/fuel
mixture control device, varied air/fuel ratio by controlling
fuel injection quantity. Excess air ratio (lambda) may be
varied from 0.5 to 2.0 through the use of this control. The
second device varied ignition timing between 0° before top dead
center (BTDC) and 54° BTDC.
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Following the conversion from gasoline to M100 fuel
operation, Nissan Motor Company, LTD lent this engine to the
U.S. EPA for use with methanol fuel research efforts.
IV. Modifications For 2H2/CO Fuel Operation
Several modifications to the engine were necessary in
order to operate on 2H2/CO fuel; these modifications are
discussed below. Included also is a discussion of the bottled
gas fueling system.
A. Engine Modifications
Dissociated methanol product gas is a mixture of H2 and
CO gases in the molar ratio 2H2/CO. We did not possess a
methanol dissociation system capable of generating the
necessary quantities of gaseous 2H2/CO fuel at the time work
on this project was begun. The engine was therefore tested on
a bottled gas mixture of 2H2/CO; several bottles of 66 volume
percent H2 and 34 volume percent CO were obtained from Linde
Gases, Inc. to simulate the products of the dissociation
reaction.
The Nissan CA18DE engine utilizes a 4-valve per cylinder
vaI vet rain configuration; both the stock gasoline and M100
methanol modified versions utilize two intake and two exhaust
valves per cylinder. This arrangement was modified to allow
for admission of air to the cylinder through one intake valve
only; the second intake valve supplied the gaseous fuel. The
exhaust-side valve scheme was not modified (Figure 1).
FIGURE 1
VALVE SCHEME
2H2/CO FUEL CONVERSION
NISSAN CA18DE ENGINE
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The advantages of structuring the intake process this way
are threefold. First, air flow into the engine may be less
restricted if the fuel, already in the gaseous state, is
introduced into only one of the intake runners. Second, there
may be less chance of flashback and a resulting manifold
ignition if fuel exclusively, and not a combustible fuel/air
mixture, is introduced at an intake valve. Finally, fuel may
enter the combustion chamber at the designer's discretion,
rather than at the same time the air needed for combustion is
admitted.
It was necessary to alter the fuel and air intake system in
order to allow for the admission of gaseous fuel only through
one of the intake valves. An intake air control assembly
encloses the swirl control valves and is situated between the
intake manifold and the combustion chambers on the liquid-fueled
engine. This assembly controls the air flow so that it is
through one intake runner and/or through both intake runners as
necessary. This is to control in-cyUnder charge motion on the
liquid-fueled engine. The control valve slide and actuator were
disassembled and the swirl control valves removed. The runners
through the valve assembly that contained wells for fuel
injectors were welded shut approximately 1/2-inch upstream from
the well holes. These seals prevent the admission of air to the
ports through which the gaseous fuel passes.
The hole in the assembly left by the power valve slide was
sealed to prevent leakage of fuel and air between runners. A
metal impregnation technique was used to seal the holes. The
sealed holes were then coated with a layer of epoxy.
Fuel injectors are not used to feed the gaseous state
fuel. The rail and the individual injectors were removed and
3/8-inch inside diameter stainless steel pipe fittings were used
in their place. The stainless steel fittings were threaded and
the insides of the aluminum injector wells were then threaded to
accept the fittings.
Stock dual-overhead camshafts were used by Nissan to equip
the CA180E engine modified for use on M100 methanol. A drawing
of the stock intake-side camshaft is presented in Figure 2. It
was necessary to redesign the intake side lobes in order to
accommodate the air/fuel induction strategy depicted in Figure 1
for the gaseous fuel. Figure 2 also presents the air/fuel lobe
scheme for the intake camshaft when operated on gaseous fuel.
Nissan reported that the valve timing events for the
M100-modified engine were similar to those of the stock
gasoline-fueled version. Valve timing was measured
independently, however, as these measurements were necessary as
a point of reference for the redesign of the intake side
camshaft. These measurements are given in Table 1. Table 2 is
a summary of the intake valve events in a stock (gasoline-fueled)
engine as well as the measured events from the modified engine.
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FIGURE 2
CA180E ENGINE INTAKE CAMSHAFT
FUEL/AIR CAM LOBES INDICATED
FUEL LOBES
Table 1
Stock Intake Valve Event Timing Measured By EPA
Crankshaft Position
7-1/2 degrees ATDC
15 degrees ATDC
24 degrees ATDC
35 degrees ATDC
59 degrees ATDC
129 degrees ATDC
17 degrees ABDC
42 degrees ABDC
53-1/2 degrees ABDC
65 degrees ABDC
91-1/2 degrees ABDC
Valve Lift
.005 i nches
.020 inches
.050 inches
.100 inches
.200 i nches
.332 inches (maximum lift)
.200 inches
.100 inches
.050 i nches
.020 inches
.005 i nches
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It should be noted that a valve lift of .005 inch was used
to denote valve-open and valve-closed events. The criteria
Nissan used to define opening and closing was not available.
There is a substantial difference, evident in Table 2, between
the valve timing information provided by Nissan and the timing
measured by EPA. The definition of what constitutes valve
opening may explain some of this difference. Also, Nissan
milled the engine head to increase the compression ratio on the
M100-modified engine; this modification may also account for
much of the timing difference.
The production of the intake camshaft to accommodate
2H2/CO fueling was outsourced to General Kinetics Co. Inc.,
Detroit, Ml. A summary of the camshaft specifications for the
redesigned shaft is given in Table 3. Timing and design for
the air as well as the fuel cams was altered. Air valve
opening commences at 15 crankshaft degrees before top dead
center (BTDC), and closes at 30 crankshaft degrees after bottom
dead center (ABDC). Opening of the fuel valve commences at 15
degrees ABDC: it closes at approximately 65° BTDC, for an open
time of 100 crankshaft degrees. The height of the fuel valve
lift is .0787 inch. Valve head diameter for both air and fuel
valves are similar to stock intake valve, 1.340 inch.
The intake cam lobes on the stock camshaft opened the
valves through a hydraulic lifter mechanism. To accommodate
the acceleration change caused by shortening the cam event to
100° from 248° while maximizing valve lift, it was necessary to
increase the diameter of the base circle of the fuel cam.
Lengthening the base circle diameter of the fuel cam, while
maintaining the same lift, mitigates wear caused by the contact
of the sharply accelerating cam on the lifter, hence increasing
Ii fter durabiIi ty.
The stock hydraulic lifter system, however, was clearly
unacceptable for the increased base circle diameter of the fuel
lobes. Had the stock lifter been used, contact with the
lengthened cam base circle would have kept the fuel valves open
continuously. It was necessary, then, to replace the hydraulic
lifters with mechanical lifters that could be tailored to the
new base circle height. A lash of .003 inch was also added to
the new mechanical lifters to improve wear. The design and
construction of the mechanical lifters was done by Batten
Engineering of Romulus, Ml.
A 4-cyUnder light-duty automotive engine with a stock
valve configuration similar to the test engine has been
modified for H2 fuel operation and is described in the
I iterature.[12] Though our gaseous fuel was of a different
composition than the pure H2 fuel in reference 12, this paper
was useful because it described a modified fuel system that
could potentially be adapted for our application. The valve
timing information was of particular interest to us; the fuel
valve timing specifications were used as a general guide during
the design of the gaseous fuel intake system for our engine.
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Table 2
Stock/Ml00-Modified Intake Camshaft Specifications
Specif icat ion
Cam height
Valve Lift
Valves open*
(crankshaft degrees)
Valves close*
Standard
CA18DE Engine
1.5939—1.5951 inches
.335 inches
15° BTDC
53° ABOC
Measured By EPA
On M100-Modified
Eng i ne
.332 inches
7.5° ATDC
91.5° ABDC
Indicates not measured by EPA.
Lift = 0.005 inches measured by EPA; criteria not
available for standard engine.
Table 3
Intake Camshaft Specifications -
2H?/CO Fuel Modification
Speci f icat ion
Valve lift
Valve head diameter
Valve opens*
(crankshaft degrees)
Valve closed*
(crankshaft degrees)
Total value event
Air Valve
.3220 inches
1.340 inches
15° BTDC
30° ABDC
225°
FueI VaIve
.0787 inches
1.340 inches
15° ABDC
65° BTDC
100°
Valve Iift = 0.005 inch.
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B. Fuel System Modifications
The 2H2/CO fuel is a gaseous blend with a composition of
66 and 34 volume percent H2 and CO respectively. This fuel
is stored in compressed gas cylinders ("T" size) at 1600-1800
psi. A fuel supply cylinder is anchored to a concrete safety
stop outside of the test cell, approximately 10 feet from the
cell wall during testing. The bottle, fitted with a regulator
and pressure gauge, is opened by a hand valve prior to
testing. The fuel line from the bottle is 1/4-inch stainless
steel tubing, 22 feet in length from bottle to cell wall.
The stainless steel fuel line enters the cell through a
hole drilled through the concrete block wall. A Gould
electrically controlled solenoid valve is located in the line
immediately after the wall. An electrical signal from an
accutator in the control room controls the opening of the valve
to accept flow from either of two lines. The first line is
connected to the fuel supply while the second extends from an
N2 gas source outside the cell. This N2 gas is used to
purge the fuel lines in the cell prior to and immediately after
testing. A shut-off valve in the purge line, when closed,
keeps N2 gas out of the cell fuel lines following the purge
operat ion.
The fuel line from the cell wall to a fuel flow regulator
measures approximately 54-1/2 feet. This regulator is a Twin
Bay Model TB-100. Gas flow through this regulator is
controlled by a flexible diaphragm. The diaphragm is opened
proportionally to the pressure exerted by a stream of air
provided by a tank of compressed air; the pressure exerted by
this airstream is controlled by a valve located in the cell
control room.
fuel flows from the Twin Bay regulator to a
switching valve. This valve has two positions: the first
supplies fuel to the engine, while the second diverts the gas
stream to the scrubber during purging of the test cell fuel
lines. During testing, the fuel flows from the valve to a
rotameter calibrated to measure 0-10 SCFM. The fuel passes
through this gauge and then through a tee; a pressure gauge in
the control room is operated by flow through this tee.
The final stage of the fuel system supplies the gaseous
fuel to the combustion chamber ports. From the tee mentioned
above, the fuel passes to a a cylindrical plenum, this plenum
serving as a header to four flexible fuel lines. Inserted in
each of the four fuel lines approximately 17 inches from each
cylinder is a 2-stage H2 flame arrestor. The fuel lines are
connected to threaded fittings which are screwed into the fuel
injection ports in the valve control assembly. The 2H2/CO
fuel is supplied to the combustion chambers by the opening of
the fuel valves.
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V. Exhaust Analysis
Engine exhaust passes from the exhaust pipe to a 2-1/2
inch diameter flexible metal tube. This tube passes the
exhaust overhead to a 6-inch rigid tube hung from ceiling
supports. The rigid tube delivers the exhaust to a Philco Ford
350 cfm constant volume sampler (CVS). Total length of the
flexible and rigid tube sections is 40 feet.
A gaseous sample line and electronic ties have been
extended through the cell ceiling and connect the mechanical
CVS with an electronic display panel in the cell control room.
A fitting in the sample line at the control room enables bag
sampling at this point. Analysis of bag samples is
accomplished at a bank of analyzers located in another test
cell. Emissions measured as hydrocarbons (HC) are measured on
Beckman model 400 flame ionization detector (FID). NOx level
determination is conducted on a Beckman model 951
chemiluminescent NO/NOx analyzer. CO is measured by infrared
technique using a Horiba model A1A23 infrared analyzer.
Exhaust formaldehyde was measured using a dinitrophenyI
hydrazine (DNPH) technique.[13] Exhaust carbonyls including
formaldehyde are reacted with DNPH solution forming hydrazine
derivatives; these derivatives are separated from the DNPH
solution by means of high performance liquid chromatography
(HPLC), and quantization is accomplished by spectrophotometric
analysis of the LC effluent stream.
A second sample line extends from the CVS to a heated
manifold. This manifold contains ports for three DNPH
sampling cartridges. Flow to individual cartridges is
controlled by three solenoid valves located downstream from the
DNPH cartridges. The hot sample gas flows through a cartridge
and then to a heat exchanger where the gas is cooled to 21°C.
Flow for the formaldehyde sampling system is measured with
a Porter Mass Flow Controller calibrated to 5 standard liters
per minute. Gaseous sample from the heat exchanger flows past
a solenoid valve and is pumped through a dual filtration system
to remove any water present in the sample. The pump is a Gast
model 746A with a maximum rated pressure of 100 psig. The
exhaust sample is then passed through the mass flowmeter where
sample flowrate is determined; an electronic gauge in the
control room is wired to the flowmeter and displays both
flowrate and total accumulated volumetric flow through a
selected DNPH cartridge.
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VI. Results From Testing
Several attempts were made to characterize the emissions
profile of the test engine when it was operated on M100 fuel.
These test results are compared below to emission levels
measured when the engine is fueled with 2H2/CO to quantify
any change in emission levels due to the different fuels.
Nissan requested that the engine not be operated at wide
open throttle conditions due to poor intake mixing. We
therefore measured emissions over speed and load conditions
that do not excessively burden the engine: idle (no load),
1600 rpm/30.8 ft-lb and 2400 rpm/40.5 ft-lb.
Air/fuel ratio (A/F) and injection timing may be varied
through the use of a rheostaticaIly equipped control panel that
Nissan provided with the engine. A/F ratio was measured with
an NTK Micro Oxivision MO-1000 A/F ratio meter. This meter was
used as a guide to control engine A/F ratio; A/F ratio was
controlled to near stoichiometric conditions for testing with
Iiquid fuel.
Following the conversion of the intake system for
operation with gaseous fuel the engine was again emission
tested over several modes with 2H2/CO bottled gas fuel. The
results from this preliminary testing on both liquid and
gaseous fuels are presented in tabular form below.
Though test results from operation on both fuels by mode
are presented in the same table for comparison, significant
differences in test conditions occurred. These differences
unfortunately make only general comparison of test results from
these fuels possible.
We initially set up the engine in the liquid fuel mode
with a catalytic converter in the exhaust stream. Emission
results from M100 testing were of course affected by the
placement of this converter in the exhaust stream. Emissions
from testing on the gaseous fuel were not influenced by a
catalytic converter; these are engine-out emissions. Future
efforts will include additional testing which will enable a
better comparison of engine-out emissions with both fuels. It
is also possible to run the test engine for only a short time
on the bottled gas fuel. Safety factors prohibit filling a gas
T-cylinder with the 2H2/CO mixture to more than 1800 psig.
This is enough fuel to allow for a brief warmup and 5 minute
emission test at 2000 rpm/27 ft x Ibs of torque, for example.
Consequently, warmed steady-state conditions were not reached
prior to emissions testing on the bottled gas fuel. Adequate
fuel storage for emissions testing is therefore another problem
to be addressed in our future efforts.
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Table 4 presents the results from emission testing with
both fuels at no load idle conditions. It was not possible to
warm the engine to steady-state conditions prior to testing
with the gaseous 2H2/CO fuel, however. Gaseous fuel testing
consisted of a cold start, adjusting engine speed by varying
the A/F mix until the desired speed was attained and then
sampling exhaust emissions over a 5-minute period. Exhaust
emissions sampling with M100 fuel was conducted over a 5-minute
period with the test engine warmed to steady-state conditions
(coolant and oil temperature monitored).
The engine idled at 750 rpm with M100 fuel under control
of the electronic control unit; the engine was idled at various
speeds with gaseous 2H2/CO fuel. The engine appeared to run
much smoother on the gaseous fuel; it did not appear to labor
perceptibly at 575 rpm.
A/F ratio with M100 fuel operation was measured with an
NTK MO-1000 meter. The warm engine was controlled to near
stoichiometric conditions using the A/F control box. The A/F
ratio meter proved unsuitable for the gaseous fuel mixture,
however. A maximum value for lambda (A/F actual over A/F
stoichiometr ic) of 2.29 can be displayed by the meter. This
equates to an A/F ratio of 14.7 (6.4 is approximately a
stoichiometric condition for M100).[14] The sensor to the
meter was calibrated as if methane I fuel was being used, as the
carbon/hydrogen and oxygen/carbon ratios are similar for M100
and the 2H2/CO mixture. The meter indicated a lambda value
of 2.29 at 625 rpm; adjustments to the fuel and air to raise
the engine speed cause the meter to tilt, indicating an
out-of-bounds (excessively lean for the meter) condition had
been reached.
Air and fuel were measured directly into the engine in
order to calculate A/F ratio for the gaseous fuei at idle. Air
was measured with a hot wire anemometer through a calibrated
orifice, while gaseous fuel was measured with a rotameter. An
example of the calculation of A/F from this data is included in
Appendix B.
A/F ratio with the gaseous fuel was very lean when
compared to liquid fuel operation. A/F ratio with gaseous fuel
was calculated at 14.8 for 625 rpm and no load idle
conditions. The mixture became leaner as engine speed
increased. Between 1200 and 1500 an A/F ratio of approximately
26.0 was measured. An A/F ratio of 26 equates to an
equivalence ratio of approximately 0.25; Hama, et al. [12]
obtained A/F ratios as low as 0.20 when operating on pure H2
fuel. A graph of A/F ratio versus engine speed at no-load idle
conditions for 2H2/CO fuel is given in Figure 3.
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Table 4
Emission Testing, Nissan CA18DE Engine
M-100, 2H2/CO Fuels, Cold Idle Mode
Fuel
M100*
2H2/CO
2H2/CO
2H2/CO
2H2/CO
2H2/CO
2H2/CO
2H2/CO
2H2/CO
2H2/CO
2H2/CO
Eng i ne
Speed
(rpm)
750
575
625
625
900
1000
1000
1200
1250
1500
1500
Air/
Fuel
(ratio)
6.88
N/A
N/A
14.8
N/A
20.2
24.3
26.0
26.5
26.0
26.0
HC CO
(q/hr) (q/hr)
0.38
0.01 61.96
98 . 24
47 . 03
0.02 66.36
0.28 166.01
247 . 38
346.15
261 . 64
0.14 439.32
309 . 06
C02
(q/hr)
1826
928
1541
1475
1696
2062
1945
2326
2545
3016
3127
NOx HCHO
(q/hr) (mq/hr)
0 . 05 11.9
21.5
21.1
28.3
18.2
0.55 27.6
0.06 35.1
0.12 15.1
0.11 18.4
0.12 22.9
0.11 18.8
Engine warmed to steady-state conditions;
converter in place in the exhaust stream.
N/A Not avai(able.
None detected.
catalyt ic
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FIGURE 3
A/F VERSUS ENGINE SPEED
NO LOAD IDLE CONDITIONS
30
25
20
15
10
A/F RATIO
700 900 1100 1300 1500
ENGINE SPEED (RPM)
— 2H2/CO FUEL + M100 METHANOL FUEL
Emissions measured as hydrocarbons (HC) with a propane
calibrated FID were 0.38 grams per hour with the engine fueled
with M100. Engine-out HC emissions were essentially negligible
with gaseous 2H2/CO; two tests indicated more than
insignificant amounts of HC, however. The gaseous fuel results
are engine-out emissions, however, while the M100 data was
influenced by the presence of a catalytic converter in the
exhaust system. Additional testing will have to be conducted
to confirm or deny these levels.
CO emissions are also presented in units of grams per
hour. The catalyst-equipped M100-fueled engine produced no
measureable amounts of CO; this was the result of a single
test, however. Additional testing under engine-out conditions
will have to be conducted in order to provide sufficient data
for comparison. CO emissions from gaseous fuel operation
increased as engine speed increased. It is interesting to
note, however, that in the case of the gaseous fuel, this CO
might be better described as "unburned fuel" rather than viewed
as a product of partial combustion.
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It was more difficult to identify a relationship between
engine speed and emissions levels of NOx and HCHO at no load
idle conditions with gaseous fuel. NOx emissions are
identified with higher temperature engine operation; as engine
oil and coolant temperature were not stabilized prior to
emissions testing, combustion chamber temperatures may have
varied during each emissions test. One test at 1000 rpm engine
speed gave a value of 0.55 grams per hour for NOx, much higher
than previous or successive tests. HCHO emissions do not
appear to correlate well with engine speed and hence fuel
consumption. One control test of a DNPH cartridge, however,
indicated contamination or a chromatograph inconsistency that
would have allowed an error of 10 milligrams per hour to be
added to HCHO actually measured. Several more tests will have
to be conducted to determine the magnitude of this error.
Table 5 presents the results of several emission tests
conducted with the engine operating under load. The tests with
M100 fuel were conducted with the engine operating at warmed,
steady-state conditions and with a catalyst in the exhaust
stream. The gaseous fuel tests measured engine-out emissions.
The engine was not run at speeds higher than 2000 rpm on
gaseous fuel.
The first tests with M100 fuel were conducted at an engine
speed of 1600 rpm and a brake torque of 30-31 ft x Ibs (9.4
-9.6 brake horsepower). Emissions results were inconclusive as
they varied considerably. Brake specific HC varied from 0.002
to 11.81 grams per brake horsepower hour (g/BHP-hr); brake
specific NOx varied from 8.89 to 0.86 g/BHP-hr. These tests
will be repeated after the engine is reconfigured to run on
liquid fuel again; catalyst light-off and the problem with
air/fuel mixing with liquid fuel that Nissan made us aware of
may have contributed to this variability. Testing at 2400 rpm
was also inconclusive, due greatly to the limited number of
tests conducted. C02 emissions varied from 472 to 634
g/BHP-hr over these two tests, a very substantial difference.
Testing with gaseous fuel was conducted at 2 different
engine speeds: 1500 and 2000 rpm. At 1500 rpm the throttle
was opened to 4.5 in. HG manifold vacuum. Fuel was adjusted to
bring A/F ratio to 16.07 and 11.9 at 1500 and 2000 rpm
respectively. A load of 24.1 ft x Ibs was placed on the engine
at 1500 rpm; 26.6 ft x Ibs was placed on the engine at 2000
rpm. Manifold vacuum at 2000 rpm was 7.0 in. HG.
The engine ran very smoothly under load with the gaseous
fuel. The lower manifold vacuum figures, however, suggest that
the throttle was substantially open, indicating that further
increases in power may be difficult to obtain at these engine
speeds with the engine as presently configured.
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Table 5
Emission Testing, Nissan CA18DE Engine
M100, 2HZ/CO Fuels, Load Testing
Engine Air/ Brake Brake Specific Emissions
Fuel
M100*
M100*
2H2/CO
M100*
M100*
2H2/CO
Speed
( rpm) i
1600
1600
1500
2400
2400
2000
Torque
(ft Ib)
30.8
30.4
24.1
40.5
40.8
26.6
Fuel
( ratio)
6.60
7.00
16.07
6.34
6.38
11.9
HP BSHC BSCO
(BHP) (g/BHPhr) (q/BHPhr)
9.
9.
7.
18.
18.
10.
62
39
01
97
90
32
.002
11.81
0.20
—
0.07
0.13
0.46
—
1.91
0.35
1.45
2.27
BSCO 2
(g/BHPhr)
781.
762.
717.
472.
634.
426.
BSNOx
(g/BHPhr)
8
0
2
0
0
8
.89
.86
.84
.20
.01
.57
BSHCHO
(mg/BHPhr)
1.5
1.2
4.7
—
—
2.0
* Engine warmed to steady-state conditions; catalytic converter in place in the
exhaust stream.
None detected.
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The emissions results from gaseous fuel testing are
inconclusive due to the limited number of tests performed at
the time of this report. NOx, however, was measured at 8.57
g/BHP-hr at 2000 rpm engine speed, a higher level than had been
recorded during liquid fuel testing at greater speed and load
conditions. Again, liquid fuel emission results were
influenced by the presence of a catalytic converter. CO, at
2.27 g/BHP-hr, 2000 rpm conditions might be considered somewhat
low when compared with the warmed, catalytic converter equipped
liquid fuel emission results. More carefully controlled
emission tests will be performed in order to properly
characterize the emissions profile from the engine when
operated on both the liquid and gaseous fuels.
VII. Project Highlights To Date
1. The engine ran very smoothly at idle and under load
conditions with the simulated dissociated methanol 2H2/CO
fuel. Visible engine vibration during gaseous fuel operation
was noticeably reduced from the level experienced with the
engine operating on liquid methanol fuel.
2. The engine was able to operate over a very wide
range of A/F ratio setpoints with the 2H;/CO gaseous fuel.
A/F ratio was calculated between 14.8 and 26.5 at no-load idle
conditions between 625 and 1500 rpm. At conditions of 2000 rpm
engine speed, 10.32 BMP, A/F ratio dropped to 11.9.
3. A direct comparison of emissions test results from
the engine when it is alternately fueled with M100 and 2H2/CO
is not available at this time. The testing with M100 fuel
utilized a catalytic converter in the exhaust stream while
2H2/CO fuel results are engine-out emissions. The 2H2/CO
fuel emissions test results may vary substantially between
tests because the limited amount of 2H2/CO fuel in the "T"
cylinder storage bottles did not permit starting and warming to
steady-state conditions prior to testing.
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VI11.Future Effort
This engine conversion project was begun to develop an
engine that could be used as a suitable test bed for a
practical, onboard methanol dissociation system. Further
development of this engine concept will be structured to
accommodate this goal. Immediate plans concern development of
two measures of engine performance:
1. Emissions/fuel economy; and
2. Engine performance at lean operating conditions.
Further emissions testing at various engine speed/load
operating conditions will be conducted to characterize the
emissions profile of this engine when operated on both M100 and
dissociated methanol. A/F ratio at these various test points
will also be determined.
Previous testing with M100 liquid methanol was conducted
with a catalytic converter in the exhaust stream. This
catalytic converter will be removed in order to provide
engine-out emissions data for comparison.
The effect of changes in spark timing on engine
performance and emissions in the testing reported on here was
not measured. Spark timing will be adjusted in future testing
in order to obtain mean for best torque (MBT) conditions for a
range of engine speeds.
One way to determine the proximity to the lean misfire
limit at various engine-operating conditions is to obtain a
quantifiable measure of increasing engine roughness as the
air/fuel mixture is leaned out. A measure of proximity to lean
misfire limit may be obtained directly, through measurement of
changes in cylinder pressure during the combustion effort. An
indirect method might involve the measurement of the
variability in successive crank rotation times as leanness
increases. The test engine is not equipped with a knock
sensor; it should therefore be possible to obtain a
quantifiable measure of engine performance as the lean misfire
limit is approached when the engine is fueled with the gaseous
2H2/CO blend.
Kistler Instrument Corporation has modified a spark plug
from this engine to accept a pressure transducer adaptor. This
adapter, when fitted with a Kistler Model 601B1 pressure
transducer will allow measurement of cylinder pressure in the
otherwise unmodified engine. Future work will include
measuring cylinder pressure changes and relating them to
changes in A/F ratio as the lean limit is approached.
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IX. Acknow Iedgment s
The CA18DE test engine described in this report was
modified for use with M100 neat methanol and loaned to EPA by
the Nissan Motor Corporation as part of an ongoing joint
cooperative effort to investigate the potential of neat
methanol as an alternative motor vehicle fuel. The authors
also appreciate the efforts of Jennifer Criss and Marilyn Alff
of the Control Technology and Applications Branch, ECTD, for
typing, formating, and editing this report.
X. References
1. The Clean Air Act As Amended Through July 1981,
Section 211(c)(1).
2. Speech by Charles L. Gray, Jr., EPA, OAR, QMS, to
1983 Midyear Refining Meeting of the API, May 11, 1983.
3. Policy Statement by Vice President of the U.S.A.,
George Bush, March 6, 1987.
4. "Basic Theoretical Investigations of Decomposed
Methanol," Bechtold, Richard L., Mueller Associates, Inc.,
Department of Energy CONF-8306135, October, 1983.
5. "Resistively Heated Methanol Dissociator for Engine
Cold Start Assist - Interim Report," Piotrowski, G.,
EPA/AA/CTAB/88-02, March 1988.
6. Proceedings of The Third International Symposium On
Alcohol Fuels Technology, Inagaki, T. , T. Hirota, and Z. Veno,
Asilomar, CA, May 29-31, 1979.
7. "Dissociated Methanol Engine Testing Results Using
Hz/CO Mixtures," Proceedings of the Eighteenth Intersociety
Energy Conversion Engineering Conference, Anthonissen, E. and
J. S. Wallace, Orlando, FL, August 21-26, 1983.
8. "Research and Development of Alcohol Fuel Usage in
Spark-Ignited Engines," Pefley, R. K. and L. H. Browning, U.S.
DOE DE-FG03-84CE50036, April, 1986.
9. "Dissociated Methanol Test Results," Presented at
the Automotive Technology Development Contractor Coordination
Meeting, Finegold, J. G., and J. T. McKinnon, Dearborn, Ml,
April, 1982.
10. "Design and Testing Of A Dissociated Methanol
Vehicle," Karpuk, M. E. et a I., Solar Energy Research
Institute, Golden, CO, October, 1988.
11. U.S. EPA Contract No. 68-03-3540.
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-20-
12. "Hydrogen-Powered Vehicle With Metal Hydride Storage
and D.I.S. Engine System," SAE Paper 880036, Hama, J., Y.
Uchiyama and Y. Kawaguchi, March 1988.
13. "Formaldehyde Measurement In Vehicle Exhaust At
MVEL," Memorandum, Gil key, R. L., OAR, QMS, EOD, Ann Arbor, Ml,
1981.
14. "Alternate Fuels Research Guidebook, Fuel
Characterization, Engine and Vehicle Testing," DOE/CE/50046-1,
December 1985.
15. "Internal Combustion Engines and Air Pollution,"
Obert, E. F., Harper and Row, New York, NY, 1973.
16. Introduct ion t^> ChemicaI Engineering Thermodynamics,
3rd Edition, Smith, J. M. and H. C. VanNess, McGraw-Hill, New
York, NY, 1975.
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APPENDIX A
TEST ENGINE SPECIFICATIONS - M100 FUEL OPERATION
Manufacturer
Basic engine designator
Displacement
Cylinder arrangement
VaI vet rain
Combustion chamber
Bore x stroke
Compression ratio
Compression pressure
Fuel control system
EGR
Valve clearance
Idle speed
Engine oiI
Fuel
Air/fuel control
Spark advance control
Nissan Motor Co., LTD.
CA18DE
1809 cc
4-cyIi nder, i n-1i ne
DuaI-ove rhead camshaf t
Pent roof design
83 mm x 83.6 mm
11.0
16.5 kg/square cm (350 rpm, 80°C)
Electronically controlled fuel
inject ion
EGR not used
0 mm (automatically adjusting)
750 rpm
Special formulation supplied by
Nissan for methanol engine
operat ion
M100 neat methanol
Excess air ratio may be varied
from 0.5 to 2.0 by means of an
external control
Ignition timing can be varied from
0° BTDC to 54° BTDC by means of an
external control
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APPENDIX B
AIR/FUEL RATIO CALCULATION WITH 2H2/CO Fuel
Air/fuel ratio is defined [15] as:
Mass flowrate of air , dimension I ess (1)
Mass flowrate of fuel
Molecular weight of air, 28.89, approximately.
Calculate molecular weight of fuel, 2H2/CO:
2/3 (molecular weight of H2, 2) = 1.333
1/3 (molecular weight of CO, 28) = 9.333
Molecular weight of fuel, approximately 10.666
At standard conditions, for gases,
PV = nRT (2)
Where:
P, pressure, atmosphere
V, volume, cubic feet
n, Ib. moles
R, constant, .7302 atm ftVlbmol °R [16]
T, temperature, °R
At standard conditions,
T = 492 °R
P = 1 atm
Mass flowrate may be defined as:
PVT (molecular weight) = nT(molecular weight) (3)
RT
Where:
VT, Volume/time, ftVminute
nT, Ib moles/minute
Given,
Air flowrate, 6.0 standard cubic feet/minute (SCFM)
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APPENDIX B (CONT'D)
AIR/FUEL RATIO CALCULATION WITH 2H2/CO Fuel
Fuel flowrate, 1.1 SCFM
Calculate A/F ratio:
Mass flowrate of air, from (3)
(latm)(6.0 SCFM)(28.89 Ib./lbmol) = .4825 Ib./minute, air
(.7302) (492°R)
Mass flowrate of fuel,
(latm)(1.1 SCFM)(10.666 Ib./lbmol) = .0327 Ib./minute, fuel
(.7302)(492°R)
From (1),
A/F = .4825 Ib/minute = 14.8, answer
.0327 Ib/minute
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