EPA-AA-SDSB-82-12
Technical Report
Characterization of a Heavy-Duty Diesel
Engine Modified for Operation on Neat Methanol
By
Randy Jones
June 1982
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.
Standards Development and Support Branch
Emission Control Technology Division
Office of Mobile Source Air Pollution Control
Office of Air, Noise and Radiation
U. S. Environmental Protection Agency
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I. Introduction
Because of the increased interest in methanol as a motor
vehicle fuel, EPA's Office of Mobile Source Air Pollution Control
(OMSAPC) has initiated a vehicle and engine testing program to
characterize the emissions and performance of the most likely
methanol applications. In one study an International Harvester
DT-466B heavy-duty diesel engine was modified and subsequently
tested on diesel fuel and on neat methanol. This report describes
the conductance and results of the study.
II. Background
The growing dependence of many countries on unstable supplies
of imported petroleum has created a need to evaluate the use of
alternative fuels. One of the most promising and extensively
studied alternate fuels is methanol.
Methanol is well suited for use in the fuel-inducted,
spark-ignition (SI) engine and much research and attention has
been concentrated in this area. Methanol has been generally
disregarded for use in the fuel-injected, compression-ignition
(CI) engine, because its low cetane properties make it difficult
to compression-ignite. However, if an ignition source is
provided, methanol's combustion properties are such that it can be
used in the traditional CI engine and potentially result in
environmental benefits when compared to diesel fuel or other
alternate fuels.
Methanol1s high octane rating allows for the higher
compression ratios, hence higher thermal efficiencies, of SI
engines. Methanol use in the CI engine would take advantage of
the inherently better efficiency of unthrottled operation.
Methanolfs ability to burn at lower flame temperatures contribute
to better efficiency and lower NOx emissions. The organic
emissions from methanol combustion are primarily unburned fuel and
aldehydes, which are controllable with standard oxidation
catalysts. Since methanol fuel contains no catalyst-poisoning
heavy metal or sulfur compounds, unburned fuel and organic
emissions may perhaps be controlled with a base metal catalyst
instead of the more expensive noble metal catalysts currently in
use. Methanol also burns free of carbonaceous particulates, a
major emission problem of diesel engines today. In short,
methanol use offers the potential to achieve comparable
performance and engine efficiency as diesel fuel with
significantly lower exhaust gas and particulate emissions.
The most common methods to accomplish ignition of methanol in
a diesel type engine, so far, have been the use of cetane
improving additives to the fuel,[1,2,3,4] diesel-fuel
pilot-injection systems,[5,6,7] or an electrical ignition
system.[8,9,10,11,12] The use of cetane improvers has resulted in
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acceptable performance but to date has proven otherwise
undesirable because of increased emissions, cost, and safety
concerns. Diesel-fuel pilot-injection systems have also been
demonstrated with acceptable performance and emissions, but the
additional cost and complexity of a second injection system is a
major drawback to this type of system.
Electrical ignition sources have been used successfully in
several test projects to achieve methanol combustion in CI
engines. In a project conducted in Brazil,[10] glow plugs were
used in a small diesel engine to burn methanol, resulting in
comparable performance and emissions as diesel fuel. Spark
ignition systems have also been used successfully to assist
combustion of alcohol fuels in standard diesel engines as well as
in multiple fuel engines such as the MAN-FM[11] and White/Texaco
stratified charge engine.[12]
Because of the demonstrated success and feasibility of the
test projects which utilized electrical ignition, OMSAPC
investigated this method to obtain methanol combustion in a
common, domestic diesel engine. In addition, three combustion
concepts represented by the Brazil project and the MAN-FM engines
were investigated. The combustion concepts and test program are
discussed next.
III. Test Program
A. Engine Concepts Investigated
This project centered on the investigation of three
combustion concepts for the use of neat methanol in a CI engine.
These concepts were:
1. Glow Plug "Torch" Ignition - This configuration
consisted of the addition of a glow plug directly into the
combustion chamber, and modification of the injector nozzle to
concentrate the fuel spray near the glow plug. The glow plug
provides a ,source of ignition as the concentrated spray is
introduced. This system is based on the Brazil project and
approximates the White-TCCS lean-burn, stratified charge
combustion.
2. Spark Plug "Torch" Ignition - This configuration is
similar to the glow plug ignition concept except a spark is used
to initiate combustion. The fuel spray is concentrated near the
ignition source, and, thus also approximates the White-TCCS
stratified charge combustion.
3. Fuel Deposition, Spark Ignition - This concept is based
on the MAN-FM process where fuel is deposited on the piston bowl,
combustion is initiated with a spark and sustained by continued
evaporation of the fuel into the hot rotating air. The heat for
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vaporization is theoretically supplied by flame radiation,
therefore, the rate of mixture formation is proportional to the
intensity of combustion. This functional segregation of the fuel
and air provides the stratified charge necessary for combustion in
an unthrottled engine.
With these combustion concepts and the required modifications
for engine optimization in mind, a set of criteria were developed
to select the best engine possible for testing. The engine
selection is discussed next.
B. Engine Selection
This engine was chosen after a careful review of the
technical specifications and design parameters of all domestic
heavy-duty diesel engines certified for 1981. The following
criteria were used to select the engine.
The engine should be/have:
1. A small heavy-duty engine (150-220 rated HP).
2. Adequate space in the head and combustion chamber for
the addition of a glow plug or spark plug and sleeve in each
cylinder.
3. The capacity for a two-fold increase in fuel delivery
volume since methanol's energy density is roughly half that of
diesel fuel.
4. Direct fuel injected with easily controlled injection
parameters such as timing, opening pressure, spray pattern, and
spray direction.
5. A high swirl, mexican hat type piston.
6. As few engine cylinders as possible to lessen the
modification effort.
The turbocharged IHC DT-466B was one of four engines which
best met the above criteria for selection for the project.
International Harvester generously agreed to donate the test
engine to the project, and engine selection was complete.
IV. Test Operation and Results
A. Diesel Baseline
The engine was first tested, as received, to determine
baseline performance and emissions levels on diesel fuel for
comparison to operation on neat methanol. The following test
sequence was observed:
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1. Two fine-fuel maps - These consisted of measurements of
output power, fuel flow, and air flow over a 90 point speed-load
matrix, i.e., ten power points from 10-100 percent load at each
speed increment of 200 rpm from 1,000-2,600 rpm.
2. Also performed were 13-mode steady-state emissions
tests.
3. Three transient emissions tests over the 1984
Heavy-Duty Federal Test Procedure with two additional hot-start
tests were also performed.
4. Results - This engine exhibited emissions and brake
thermal efficiency results typical for its size and class. The
transient emissions results are summarized in Table 1 and an
engine efficiency map is shown in Figure 1.
B. Glow Plug "Torch" Ignition
Several modifications were first performed in order to
operate the engine on pure methanol with glow plug ignition.
These modifications are listed below.
1. A second cylinder head was procured and fitted with
steel sleeves through the water jacket to hold the glow plug (and
spark plugs for later configurations). Because of space
limitations the glow/spark plug could only be placed in one
location, near the edge of the piston cup on the exhaust valve
side (see Figure 2).
2. Several standard and also blank, unhardened nozzle tips
were procured from their— manufacturer for machining of four
different spray patterns. These consisted of:
a. A set with a single spray hole twice the area of a
standard hole directed towards the ignition source;
b. A set with a single spray hole four times the area of a
standard hole directed towards the ignition source;
c. A set with four standard size spray holes arranged in a
135° quadrant directed towards the ignition source;
d. A set of standard nozzles with an extra spray hole
pointed directly at the ignition source.
3. To increase the fuel delivery capacity, the rotary head
assembly on the injection pump was replaced by one with a larger
plunger bore and zero retraction delivery valve.
4. A system was devised to quickly change the static
injection timing in 11° increments by rotating gear teeth on the
main drive of the injection pump.
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Table 1
Diesel Baseline Transient Test Results
Composite FTP Emissions Results
Number
3
Number
3
Number
5
HC
(g/BBP-hr)
CO
(g/BHP-hr)
NOx
(g/BHP-hr)
Fuel
(#/BHP-hr)
Particulate
(g/BHP-hr)
1.31 3.55 9.29 .49
.12 .08 .40 .02
Composite Cold-Start Emissions Results
HC CO NOx
(g/BBP-hr) (g/BHP-hr) (g/BHP-hr)
Fuel
(#/BHP-hr)
Particulate
(g/BHP-hr)
1.43 3.73 9.29 .49
.21 .17 .36 .003
Composite Hot-Start Emissions Results
HC
(g/BBP-hr)
1.36
.13
CO
(g/BHP-hr)
3.50
.09
NOx
(g/BHP-hr)
9.32
.35
Fuel
(#/BHP-hr)
.49
.02
Particulate
(g/BHP-hr)
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Figure 1
Engine Thermal Efficiency Map
IHC DT-466B Diesel Baseline
100
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rigure
Combustion Chamber
Glow Plug "Torch" Ignition
figure
Conbustion Chamber
Spark i:Torch': Ignition
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5. A system was devised to rotate the injectors so the
spray could be directed to any location in the combustion chamber.
6. Test Matrix - A test matrix was conceived to determine
the optimum operating configuration by varying several control
parameters. The parameter variations and speed sequence which
comprised the test matrix are listed in Table 2. The testing was
conducted such that nearly all possible combinations of parameter
adjustments were evaluated. The performance measure was simply
maximum torque at given speeds.
When an optimum configuration was obtained, the engine was to
be tested over fine-fuel maps, steady-state emissions tests and
transient emissions tests. However, as will be discussed later,
no configuration proved to be acceptable for emissions testing.
7. Results - The performance and efficiency results of the
best configurations are shown in Table 5. The best performance
obtained was 246 ft/lbs at 1800 rpm and best efficiency 28 percent
brake thermal efficiency at 1400 rpm. The best power obtained is
48 percent and best efficiency 84 percent of corresponding diesel
operation. This relatively poor performance on methanol may be
attributed to several factors. Methanol's high heat of
vaporization, hence long ignition delay, necessitated early fuel
injection (as much as 91° BTDC) to achieve best performance. This
early injection combined with the high swirl and typically lean
diesel operation probably resulted in a nearly homogeneous mixture
far too lean to sustain complete combustion. Analysis of raw
exhaust revealed that large amounts (6,000 ppm) of unburned fuel
were present, indicating that incomplete combustion was
occurring. The poor results are likely indicative of the tradeoff
between an early injection allowing methanol to become
combustible, and an early injection allowing the charge to be more
thoroughly dissipated. Ignition delays probably were too large
and flame propagation too inadequate to permit late injection.
Also, the location of the ignition source in the combustion
chamber may not have been ideal, but could not be changed because
of space limitations.
Because of the poor performance, this engine combustion
concept was not subjected to fine-fuel maps and emissions tests.
C. Spark "Torch" Ignition
The operation and optimization of this engine with spark
assistance required, in addition to the modifications listed
previously for glow plug ignition, the following changes:
1. Installation of spark plugs (see Figure 3).
2. Mountings were fabricated and electronic controls
assembled so two different ignition systems could be used: a high
energy ignition and a multiple spark discharge ignition.
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Table 2
Parameters Varied for Methanol Glow Plug Ignition
Sequence Static Injection
Speed Injection Nozzles Nozzle Rotation Glow Plug Depth Timing (BTDC)
800
1,000
1,200
1,400
1,800
2,200
2,600
5-hole
1 hole, 2x area
1 hole, 4x area
quadrant
Stock
45° CCW from
stock (upswirl)
45° CW from
stock (down-
swirl)
3/4"
her,
3/8"
into cham-
5/8", 1/2",
,1/4", 1/8"
\
16°
49°
82°
,27°, 38°,
,60°, 71°,
Table 3
Parameters Varied for Methanol Spark Ignition
Sequence
Speed
800
1,000
1,200
1,400
1,800
2,200
2,600
Injection Nozzles
5-hole
1 hole, 2x area
1 hole, 4x area
quadrant
Nozzle
Rotation
Stock
45° CCW
90° CCW
45° CCW
90° CCW
180° CCW
Spark Plug
Depth
1/4"
1/2"
9/10"
into
chamber
"^
Ignition Ignition
System Timing
High Energy, MET
Multiple
Spark
Static
Injection
Timing
(BTDC)
16°, 27°
38°, 49°
82°, 60°,
Table 4
Parameters Varied for Methanol Fuel Deposition
Sequence Injection Nozzle Piston Spark Ignition
Speed Nozzles Rotation Type Plug System
Static
Injection
Ignition Timing
Timing (BTDC)
800
1,000
1,200
1,400
1,800
Pintle
Tube
Stock
45° CCW
45° CCW
"Bowl" 1/4"
"Dam" 1/2"
9/10"
High Energy, MET
Multiple Spark,
Glow Plug
16°, 27°,
38°, 49°,
60°, 71°,
338°, 349°,
360°, 371°
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Table 5
Best Performance Configurations with Glow Plug Ignition
Speed
1000
1400
1800
2000
Torque
169
203
246
235
Brake Fuel
Horsepower (Ib/hr)
32.18
54
84
89
.11
.31
.49
37
57
139
160
.20
.41
.40
.00
Air /Fuel
Ratio
16.6
16.4
9.8
9.8
Thermal Nozzle
Efficiency Type
25.6%
28.02%
18.1%
16.6%
2x area
2x area
2x area
2x area
Rotation
Stock
Stock
Stock
Stock
Injection
Timing
60°
60°
60°
60°
BTDC
BTDC
BTDC
BTDC
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3. A device was installed to change ignition timing
electronically.
4. Extended electrode spark plugs, specifically designed
for this project, were procured. Three different electrode length
sets were used; one extending 1/4" into the combustion chamber,
one extending 1/2" into the chamber with the ground electrode
parallel to the center electrode, and one extending 9/10" into the
chamber, (see Figure 6).
5. Test Matrix - The optimization test matrix for the
spark ignition configuration was performed in the same manner as
for glow plug ignition. Nearly all combinations of the parameter
adjustments and speed sequence listed in Table 3 were evaluated.
6. Results - The performance and efficiency results of the
best spark, ignition configurations are shown in Table 6. The
best performance obtained was 230 ft/lbs. at 1800 rpm which is 46
percent of diesel baseline levels, and best brake thermal
efficiency, estimated at 30 percent at 1400 rpm, is 84 percent of
diesel baseline.
These results were very similar to those obtained with glow
plug ignition. The relatively poor performance may be attributed
to the same factors discussed previously for glow plug ignition
combustion, namely methanol's high heat of vaporization
necessitating early injection, high swirl precluding a stratified
charge at early injection timings, and non-optimum ignition source
placement. Even throttling the intake air could not achieve
better performance.
D. Fuel Deposition
The additional modificatons required for the Fuel Deposition
Concept testing are listed below.
1. A set of pistons with a bowl shape cavity and a lip to
aid fuel retention was machined. (See Figure 4)
2. A set of pistons with two dams welded to form a 90°
quadrant directly beneath the ignition source for fuel retention
was machined. (See Figure 5)
3. A set of pintle nozzles was procured.
4. A set of fuel nozzles with a fuel passage extension
brazed onto the tip and a threaded tube extending to just beneath
the ignition source was machined. (See Figure 7)
5. A set of spark plugs with three extended ground
electrodes was procured and machined to fit the sleeves.
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'"'able 6
Best Performance Configurations with Spark Ignition
Brake Fuel Air/Fuel Thermal Nozzle Injection Ignition
Speed Torque Horsepower (Ib/nr) Ratio Efficiency Type Rotation Ti-ming Timing
Spark Plug
1000
1400
1800
2000
1000
1400
1800
2000
183
220
230
184
110
100
150
110
34.84
58.64
78.82 129.41
77.07
20.94 43.86
26.66 61.81
51.41 83.75
46.08 108.22
-
Est
9.4 18
-
12.3 14
12.5 12
13.6 18
13.6 12
-
. 30%
.11%
-
.16%
.81%
.24%
.65%
Quad
Quad
Quad
Quad
5-hole
5-hole
5-hole
5-hole
Stock
Stock
Stock
Stock
Stock
StOCK.
Stock
Stock
71°
71°
71°
71°
71°
71°
71°
71°
BTDC
BTDC
BTDC
BTDC
BTDC
BTDC
BTDC
BTDC
32° BTDC
32° BTDC
32° BTDC
32° BTDC
41° BTDC
35° BTDC
28° BTDC
16° BTDC
1/4"
1/4"
1/4"
1/4"
i/4"
1/4"
1/4"
1/4"
into chamber
into chamber
into chamber
into chamber
into cnamber
into chamber
into cnauioer
into caainber
NJ
I
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Figure 4
Bowl Combustion Chamber
•Fuel Deposition - Spar!; Ignition
Figure 5
Dan Combustion Chanber
Fuel Deposition - Spark Ignition
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Fi^ure 6
Extended Electrode Spark Plugs
1/4"
ft]
1/2'
Figure 7
Fuel Deposition Tube Nozzles
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6. Test Matrix - The optimization test matrix for the fuel
deposition combustion concept was performed first with the "bowl"
pistons and then with the dam pistons. Two sets of injector
nozzles capable of depositing fuel on the piston cup surface were
evaluated. The first set, the Bosch pintle nozzles, had good
deposition characteristics with a mid-pressure, concentrated fuel
stream formed by injection. A major drawback to these nozzles was
that the spray direction could not be varied, and the resulting
injection was directly opposite the ignition source (see Figure
4). The second set of nozzles, the machined tube nozzles, had
good fuel location with the stream directed just beneath the
ignition source, however they possessed a large sac volume
resulting in some "dribbling" of the fuel and a more disperse
spray. A combinations of these two nozzles would have been
preferable, although not practically possible. Also investigated
with this combustion concept was the injection of fuel at the
beginning of the intake stroke. The parameters varied for the
test matrix are listed in Table 4.
7. Results - No detectable combustion was achieved with
any of the deposition test configurations. The fuel deposition
type of operation demonstrated by the MAN engine was not
achievable with this engine and the particular fuel injection,
ignition, and air flow characteristics. The major contributing
factor was probably the inability to present the spark to a region
of combustible vapors above the fuel pool in the piston. Whether
sufficient vaporization existed to create a combustible mixture at
any location in the piston cup is open for question. Other
contributing factors were: non-optimum fuel injection
characteristics, non-optimum spark location, and potentially a
failure to cold-start (a warmed-up engine may have enhanced
combustion by providing heat for initial fuel vaporization).
V. Summary
1. Combustion of neat methanol was achieved in a common
heavy-duty diesel engine, an IHC DT-466B, using glow plugs and
spark plugs as ignition sources.
2. Three combustion concepts for operation on neat
methanol were attempted with this engine: glow plug "torch"
ignition, spark "torch" ignition, and fuel deposition-spark
ignition. For each concept, several engine parameters were varied
to obtain optimum performance.
3. Results for glow and spark "torch" ignition were
comparable. The best performance obtained was 246 ft-lbs at 1800
rpm and best brake thermal efficiency 30 percent at 1400 rpm.
This was 48 percent (power) and 84 percent (efficiency) of
corresponding diesel baseline operation.
4. No combustion was achieved with the fuel deposition
concepts.
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5. Combustion of neat methanol in the engine was very
sensitive to the engine operational parameters, and was probably
inhibited by the limitation on ignition source location, high
swirl in the combustion chamber, and very lean air-fuel mixtures.
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References
1. "The Utilization of Alcohol in Light-Duty Diesel
Engines," Ricardo Consulting Engineers, EPA-460/3-81-010, May 28,
1981.
2. "The Suitability of Different Alcohol Fuels for Diesel
Engines by Using the Direct Injection Method," Pischinger, F.,
Havenith, C., Fourth International Symposium on Alcohol Fuels
Technology, Brazil, 1980.
3. "Alcohols in Diesel Engines - A Review," Henry Adelman,
SAE Paper No. 790956.
4. "The Utilization of Alternative Fuels in a Diesel
Engine Using Different Methods," E. Holmer, P. S. Berg, and B. I.
Bertilsson, SAE Paper No. 800544.
5. "Emission Characterization of an Alcohol/Diesel-Pilot
Fueled Compression-Ignition Engine and Its Heavy-Duty Diesel
Counterpart," Terry L. Ullman and Charles T. Hare, Southwest
Research Institute, EPA-460/3-81-023, August 1981.
6. "The Utilization of Different Fuels in a Diesel Engine
with Two Separate Injection Systems," P. S. Berg, E. Holmer, and
B. I. Bertilsson, Paper II-29, Third Symposium on Alcohol Fuels
Technology, May 29-31, 1979, Published by DOE in April 1980.
7. "Alternative Diesel Engine Fuels; An Experimental
Investigation of Methanol, Ethanol, Methane, and Ammonia in a D.I.
Diesel Engine with Pilot Injection," Klaus Bro and Peter Sunn
Pedersen, SAE Paper No. 770794.
8. "Spark Asssted Diesel for Multi-Fuel Capability,"
Dominyama, K. and Hashimoto, I., SAE 810072.
9. "Surface Ignition Initiated Combustion of Alcohol in
Diesel Engines - A New Approach," Nagalingam, B., et al., SAE
800262.
10. "Use of Glow-Plugs in Order to Obtain Multiful
Capability of Diesel Engines," Institute Maua de Tecnologia,
Fourth International Symposium on Alcohol Fuels Technology,
Brazil, October 5-8, 1980.
11. "Results of MAN-FM Diesel Engines Operating on Straight
Alcohol Fuels," A. Neitz and F. Chmela, Fourth International
Symposium on Alcohol Fuels Technology, Brazil, October 5-8, 1980.
12. "Performance, Emissions, and Fuel Consumption, of the
White L-1635 Stratified Charge Engine Using Various Fuels," SA
Paper No. 780641.
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