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... 3 —
Figure 1
Diagram of Valve Arrangement
For Individual Cylinder -
H2/CO Fueling System
Project:
Conversion of 16-Valve, 4-Cylinder
Engine to Operation On 112/CO Fuel
Date:
06/21/38
Hot to Scale
Drawn By:
Gregory K. Piotrowski
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-4-
The hole in the assembly left by the power valve slide was
sealed to prevent leakage of fuel and air. 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 CA18DE test engine referred to in this paper. 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 proposed
air/fuel lobe scheme for the intake camshaft.
Nissan reported that the valve timing events for the
MIOO-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.
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
reported that the engine head was milled to increase the
compression ratio on the modified engine; this modification may
also account for some of the timing dif-ference.
The redesign of the intake camshaft to accommodate H2/CO
fueling has been outsourced to General Kinetics Co., Inc.,
Detroit, Michigan. A summary of the proposed camshaft
specifications for the redesigned shaft is given in Table 3.
Timing and design for the air as well as the fuel cams will be
altered. Air valve opening will commence at 15 crankshaft
degrees before top dead center (BTDC), and will close at 30
crankshaft degrees after bottom dead center (ABDC). Shortening
the period during which the air intake valve will be open may
necessitate decreasing air valve lift; this dimension has not
yet been finalized. Opening of the fuel valve will commence at
15 degrees ABDC, and will close at approximately 65° BTDC, for
an open time of 100 crankshaft degrees. The height of the fuel
valve lift will be less than or equal to .200 inch. Valve head
diameter for both air and fuel valves will be similar to stock
intake valve, 1.340 inch.
-------
Fuel Lobes
Fioure 2
CA18DE Engine Intake
Cam Lobes Indicated
Project:
Conversion Of 16-Valve, 4-Cylinder
Engine To Operation On H2/CO Fuel
Dace:
06/22/83
Not To Scale
Drawn By:
Gregory K. Piotrowski
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-6-
Table 1
Current Intake Valve Event Timing Measured By EPA
Crankshaft Position Valve Lift
7-1/2 degrees ATDC .005 inches
15 degrees ATDC .020 inches
24 degrees ATDC .050 inches
35 degrees ATDC .100 inches
59 degrees ATDC .200 inches
129 degrees ATDC .332 inches (maximum lift)
17 degrees ABDC .200 inches
42 degrees ABDC .100 inches
53-1/2 degrees ABDC .050 inches
65 degrees ABDC .020 inches
91-1/2 degrees ABDC .005 inches
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-7-
Table 2
Current Intake Camshaft Specifications
Specification
Cam height
Valve Lift
Valves open*
(crankshaft degrees)
Valves close*
Standard
CA18DE Engine
1.5939 — 1.5951 inches
.335 inches
15° BTDC
53° ABDC
Measured By EPA
On Test Engine
.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
Proposed Intake Camshaft Specifications
Specification
Cam height
Valve lift
Valve head diameter
Valve opens*
(crankshaft degrees)
Valve closed*
(crankshaft degrees)
Total value event
Air Valve
Less than 1.59 inches
.335 inches
1.340 inches
15° BTDC
30° ABDC
225°
Fuel Valve
To be determined
.200 inches
1.340 inches
15° ABDC
65° BTDC
100°
Valve lift = 0.005 inches.
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-8-
A buildup of the gas could occur in the engine during
operation due to leakage past the valve stem seals and from
blowby. This buildup might reach explosive proportions if the
crankcase ventilation system is unable to remove the Hz gas
quickly enough. To prevent the accumulation of an unsafe
concentration of explosive gases and air, the engine was
modified to provide a blanket of inert gas where this buildup
might occur. A valve cover was modified to accept a connection
from a bottle of N2 gas. A port on the valve cover over the
exhaust side camshaft was connected to the room air system
scrubber. N2 gas at 2-4 SCFH will be admitted to the engine
during H2/CO gas operation. This carrier gas will mix with
and dilute blowby, also providing an inert atmosphere which
will not promote an explosion. This blowby/carrier gas mixture
will be exhausted to the scrubber; the line which vents the
crankcase to the combustion chambers will be plugged, ensuring
flow to the scrubber only.
Several other minor modifications will be made to ensure
better control of the air/fuel mixture from the control room,
engine start from the control room, etc. Further major engine
modifications may be made after testing on HZ/CO fuel begins.
B. Fuel System
It was necessary to construct a special fuel system to
accommodate the fueling of the test engine with the gaseous
blend. A diagram of the system is provided in Figure 3.
The H2/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 1800-1850
psi. A fuel supply cylinder will be 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, will be 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
acctuator 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
operation.
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-9-
Regulator
Pressure Gauge
Test Cell Wall
Electrically Actuated
Solenoid Valve
Shutoff Valve
H2/CO Fuel
N2 Purge
To Scrubber
Conpressed Air on
Pressure Gauge
Twin Bay Regulator
H2 Flame Arrestor
To
Engine
Control Valve Assembly
0-10 SCFM Flow Meter
Figure 3
Fuel System for H2/CO Operation
Project:
Conversion of 16-Valve, 4-Cylirder
Engine to Operation On H2/CO Fuel
Date:
06/21/88
Not To Scale
Drawn By:
Gregory K. Piotrowski
-------
-10-
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 <=i-ream 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.
H2/CO 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 will flow 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 hydrogen flame arrester. The flame
arrester is located immediately upstream from a cylindrical
plenum, this plenum serving as a header to four flexible fuel
lines. The fuel lines are connected to threaded fittings which
are screwed into the fuel injection ports in the valve control
assembly. H2/CO fuel is then directly supplied to the
combustion chambers by the opening of the fuel valves.
C. Emissions Measurement
An emissions measurement system was fabricated for the
test cell; a flowchart of the system is given in Figure 4.
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.
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"11-
cvs
Exhaust Fran Engine
Water In
DNPH Cartridges
Solenoid Valves
Solenoid Valve
Heat
^ Exchanger
Hater Out
\
Heated Manifold
vooo/
iial Filters
To Bag Sample Ports
Figure 4
Emissions Measurement System
Project:
Conversion Of 16-Valve, 4-Cylinder
Engine To Operation On H2/CO Fuel
Date:
06/22/38
Drawn By:
Gregory K. Piotrowski
Not To Scale
-------
-12-
A second sample line extends from the CVS to a heated
manifold. This manifold contains ports for three
dinitrophenylhydrazine-coated (DNPH) formaldehyde 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 Cast
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.
Several attempts were made to characterize the emissions
profile of the test engine when it was operated on M100 fuel.
These test results will be compared to emission levels measured
when the engine is fueled with H2/CO to quantify any
reduction in emission levels due to the change of fuels.
Nissan has requested that the engine not be operated at
wide open throttle conditions due to poor intake mixing. We
therefore decided to measure emission over four speed and load
conditions that do not excessively burden the engine: idle (no
load), 1600 rpm/30.8 ft-lb, 2400 rpm/40.5 ft-lb and 3200
rpm/48.5 ft-lb respectively.
Air/fuel ratio and injection timing may be varied through
the use of a rheostatically equipped control panel that Nissan
provided with the engine. Our first attempts at testing the
engine with M100 fuel utilized the same control settings that
the engine was equipped with upon arrival at EPA. The air/fuel
ratio settings provided by the manufacturer were fairly rich.
The engine was warmed to steady-state conditions and tested
over four modes: idle, 1600 rpm/30.8 ft-lb, 2400 ppm/40.5
ft-lb and 3200 rpm/43.4 ft-lb. A/F ratio was measured with an
NTK Micro Oxivision MO-1000 air/fuel ratio meter. A/F ratio
varied from a low of 4.67 at 1600 rpm to 5.60 at 3200 rpm.
Ignition timing was 23° BTDC for all modes tested.
Fuel consumption during this testing was excessively high;
we were unable to determine HC and CO emissions levels because
they were offscale on the most concentrated analyzer ranges.
NOx emissions were so low as to be unmeasurable during this
testing, however. A problem with the solenoid valve system
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-13-
prevented the acquisition of good formaldehyde data. The
overhead pipe carrying exhaust from the engine to the CVS also
developed several leaks at critical joints during this testing;
a considerable amount of fluid leaked from the exhaust system.
Testing was finally halted during the 3200 rpm mode because a
severe backfire problem developed in the exhaust system.
This testing was repeated using the Micro Oxivision meter
as a guide to leaning out engine A/F ratio over the modes upon
which we evaluated the engine. The results of this testing are
given in Table 4.
A/F ratio was controlled to near stoichiometric conditions
for this testing. HC emissions were very low; at 2400 rpm/40.5
ft-lb torque no HC were detected. The bag sampling system
appeared to function normally during testing, however. NOx
emissions varied considerably from the 1600 rpm/30.8 ft-lb mode
to the others tested. Both NOx and formaldehyde emissions were
considerably higher at the 1600 rpm/30.8 ft-lb torque point
compared to the higher speed/load points. Again, engine
backfire problems curtailed testing at idle conditions.
This testing was again repeated; results are provided in
Table 5. A/F ratios for this testing were held to ratios
similar to those given in Table 4. Engine speed/load
conditions here given also approximated those given in Table 4.
The very high HC emission level at the 1600 rpm mode in
Table 5 contrasts sharply with the .002 g/bhphr figure from the
earlier testing. CO levels between the two data sets are also
difficult to compare. No CO was detected in the bag samples at
idle and 1600 rpm conditions; this contrasts with the .46
g/bhphr at 1600 rpm recorded earlier. CO levels at 2400 and
3200 rpm conditions from the later testing increased more than
three hundred percent from earlier levels.
NOx levels indicate differences between emission levels
determined during these two test periods. Results from the
later testing show much lower NOx levels at 1600, 2400 and 3200
rpm than those from the tests conducted earlier. HCHO levels
remained approximately the same at 1600 rpm between the data
sets; again no HCHO was detected at 2400 and 3200 rpm
conditions.
No engine operability problems were encountered during
this later testing, and an idle test was conducted to measure
emission levels at no-load conditions. Emissions are expressed
as g/hr or mg/hr. No earlier idle tests were completed, so
figures for comparison are not available.
Emission levels by pollutant vary considerably between the
data sets presented in Tables 4 and 5. While these levels may
be of interest as a first approximation, the variability is too
great to allow for a reliable characterization of emission
levels from M100 operation. Additional testing is being
conducted in order to make this characterization possible.
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Table 4
Emission Testing, Nissan CA18DE Engine
M100 Fuel, First Data Set
Engine
Speed
(rpm)
1600
2400
3200
Torque
(ft-lb)
30.8
40.5
48.4
— Denotes none
Air
Fuel
(Ratio)
6.60
6.34
Brake
Horsepower
(bhp)
9.62
18.97
6.35 30.22
detected.
BSHC
(q/BHPhr)
.002
—
.004
Table
Brake
BSCO
(q/BHPhr)
.46
.35
.14
5
Emission Testing, Nissan CA18DE
M100 Fuel, Second Data Set
Engine
Speed
(rpm)
750
1600
2400
3200
Torque
(ft-lb)
Idle
30.4
40.8
42.5
Air
Fuel
(Ratio)
6.88
7.00
6.38
6.35
'Brake
Horsepower
(BHP)
0.0
9.39
18.90
26.25
BSHC
(g/BHPhr)
0.38*
11.81
0.07
0.04
Brake
BSCO
(q/BHPhr)
—
—
1.45
2.63
Specific
BSCO 2
(q/BHPhr)
781
472
686
Engine
Specific
BSCO 2
(q/BHPhr)
1826*
762
634
457
Emissions
BSNOx
(q/BHPhr)
8.89
0.20
0.79
Emissions
BSNOx
(q/BHPhr)
.05*
.86
.01
.01
HCHO
(mq/BHPhr)
1.48
—
HCHO
(mq/BHPhr)
11.9**
1.16
—
—
Denotes none detected.
* g/hr
* * mg/hr
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-15-
IV. Future Effort
This document is an interim report only; a substantial
amount of work remains to be accomplished on this project. An
outline of some of these tasks in given below, together with
short comments concerning progress being made toward completion
of the work.
A. New Emissions Tests: M100 Fuel
The emission test results provided in Tables 4 and 5 are
inconclusive. We are currently retesting the engine with M100
fuel to obtain a reference emissions profile. This testing
will be redone utilizing two separate (bag sampling and
continuous sample) banks of HC and NOx analyzers in order to
improve the accuracy of these measurements.
B. Rebuild Continuous Emissions Measurement System
An emissions measurement system capable of continuously
measuring HC and NOx emissions is present in the test cell.
This system has not been operational because of analyzer pump
problems. New pumps were ordered and received; this analyzer
system is now being made operational. We plan to use these
analyzers as a check on the bag analysis system for gaseous
pollutants.
C. Finish Camshaft Modification; Test Engine
The camshaft redesign to accommodate the fueling scheme in
Figure 1 is currently underway. After this new shaft is
designed and built, it will be installed on the test engine and
evaluated. The need for any redesign change should be made
apparent during this evaluation; any succeeding shaft will
incorporate these changes.
D. Develop Leanness Indicator
The testing referred to in C, above, has as its goal the
determination of 1) the lean limit, at certain speed and load
points, of the test engine when operated on H2/CO gaseous
fuel and 2) any improvement in the emissions profile resulting
from the use of H2/CO as a fuel. In order to quantify the
maximum lean limit information a correlation of engine
performance with increasingly lean operation is necessary.
This correlation could be done mechanically or through the use
of electronic data acquisition hardware.
Our current plan is to gather a magnetic signal, convert
it to a voltage and process the voltage as a time interval with
reference to an algorithm that relates crankshaft rotation time
to engine roughness. Engine roughness increases as the lean
misfire limit is approached, hence a quantifiable correlation
should be possible. If it is not possible to determine the
lean misfire limit electronically due to equipment availability
problems, etc. a mechanical means of making this determination
will be developed and used.
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A-l
APPENDIX A
Test Engine Specifications
Manufacturer
Basic engine designator
Displacement
Cylinder arrangement
Valvetrain
Combustion chamber
Bore x stroke
Compression ratio
Compression pressure
Fuel control system
EGR
Valve clearance
Idle speed
Engine oil
Fuel
Air/fuel control
Spark advance control
Nissan Motor Co., LTD
CA18DE
1809 cc
4-cylinder, in-line
Dual-overhead camshaft
Pentroof design
83 mm x 83.6 mm
11.0
16.5 kg/square cm (350 rpm,
80°C)
Electronically controlled fuel
system
EGR not used
0 mm (automatically adjusting)
750 rpm
Special formulation supplied by
Nissan for methanol engine
operation
M100 neat methanol
Excess-air ratio may be varied
from 2.0 to 0.5 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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