67
Research
on Methano1-fueled
Marine
Diesel Engine*
By Yoichi
Nakamura'hk, Tadahiro Ozu**, Hisashi YanLashita***,
Nobuyoshi
Nakayamab'< and Tatsuo Fujii**
Nowadays concerns about methanol
has increased from the viewpoints of environrnental protection and versatility
of fuels at a global scale. Desire for saving of maintenance cost and lobour
prevails as well as the environmental problems in the field of marine engines.
From these rnotives we have carried out research and development of a methanol
fueled marine diesel engine which is quite different from automobile en9ines in
the size, main particulars, working condition and durability.Although we have
made a great use of invaluable knowledge from automotive techno1ogy, sorne special
studies were neccessary due to these differences. Ignition method is a typical
one. Dual fuel injection system was tried for trouble-free ignition of methanol
fuel. This system is thought to be the most favourable ignition method for
marine diesel engines which have to withstand quick load change and accept no
mis-firing. Under the leadership of Ministry of Transportation and with the aid
from The Japan Shipbuilding Industries Foundation and The Japan Marine
Machinery Developrnent Association the work has proceeded from elementary
studies of injection and tribo1ogy to the running test. In this article the
effects of configurations as to fuel injection system on the engine
perforrnance are described. Fundamental running test with a single cylindered 4-stroke
test engine reveals that the marine deisel engine can afford to have such a
good performance as an original diesel engine has, when suitable reconditioning
of fuel injection-and governing systems being applied to.
1.
Introduction
Energetic research on
methano1-fueled automobile engines has been forwarded from the viewpoints of
low environmental pollution and the use of alternate fuel since the oil crisis,
and they are now being tested on vehicles in various
Countries in the world. Various technical issues have already been solved or
the prospect is bright for them. It can be said that this type of engine is
very c1ose to completion at present. On the other hand, it is an actual
situation in the marine engine field that the research on this type of engine
has hardly been tested so far, since it has seldom been evaluated from the
viewpoint of environmental pollution control because it is used at sea and the
idea tO use methano1 on marine engines is not established yet.
――――――――――――――――――――――――
*
Translated from Journal of MESJ
Vo1.26, No.9 (manuscript
received June 7, 1991) Lectured May 16, 1991
**KAWASAKI
Heavy Industries, Ltd. (3-1-1, Higashi-kawasaki-cho, Chuo-ku, Kobe, 650 Japan)
***KAWASAKI
Heavy Industries, Ltd. (1-1, Kawasaki
-cho, Akashi, 673 Japan)
However, IM0 (International
Maritime 0rgan-ization) is now investigating to include exhaust gas from ships
in the objects to be controlled from the viewpoint of environmental protection
on a worldwide scale that has been loudly emphasized recentlyl). In case clean
methanol is used as fuel,work for handling complicated machines such as
centrifuges for heavy fuel oil and for treating sludge discharged from them can
be avoided, and further it can be expected to lessen frequent engine
maintenance work. It has therefore been strongly desired to use methanol on
marine diesel engines from main1y the viewpoint of pursuing ec0nomy.
Though knowledge which has
been gained with automobile engines can be used in principle,many subjects to
be so1ved still remain, since marine diesel engines have large bores and mean
effective pressures of more than two times as much, their operating conditions
are extremely severe and they need high reliability and durability in comparison with
automobile engines. The authors have conducted the above
captioned R&D for the purpose of gaining knowledge which can so1ve these issues and contribute to engine
October
1992
(1)
68 Yoichi
Nakamura, Tadahiro Ozu, Hisashi Yamashita, Nobuyoshi Nakayama, Tatsuo Fujii
design. Methano1 has a cetane number of
threeh and,consequently,
extremely low ignitability. For automobile engines, ordinary technologies can cope with
the issues on ignition, since ignition plugs have actual service results over
prolonged periods on Otto engines and starting plugs have also been used to
date on. diesel engines. On the other hand, rnarine engines with spark ignition
can not exhibit mean effective pressures as high as those of ordinary diesel
engines because of the high rate of pressure rise during ignition and they can
not perrnit misfiring because of the large volume of their exhaust systems. The
dual fuel injection system which has actual service results on large-sized gas
engines has therefore been selected as the ignition system for this research.
Since methanol is not only
corrosive but also insufficient in lubricating ability, elemental resea-rch has
been neededto so1ve these
issues.However, elemental research will be explained at another
opportunity and this paper describes the operating performance of a methanol
diesel engine without touching elemental research.
2.
Experimental Engine
A single-,cylinder, four-stroke,
direct-injection type diese1 engine having a cylinder bore of 250mrn has been
modified so as to be suitable for this experiment. The rated speed of this
experim-ental engine has been set lower than that of the original type so that
the results of this research can be utilized as widely as possible. Table l and
Fig.1 show the principal particulars of the expeimental engine and the
schematic drawing
Fig.1 Schematic Drawing of Experimental
Engine
The combustion system of the
experimental engine is of a dual fuel injection type such that the main fuel
injection valve (methano1) is 1ocated at the center of the combustion chamber
and atomized fuel from this va1ve is ignited by the pilot oil injection frorn
the secondary injection valve (oil) 1ocated on the cylinder head near the
periphery of the combustion space. This system has been adopted from the
reasons that it has the high stability of ignition, good low load perform-ance
and high reliability, and that it serves as a rneasure to prevent corrosion,
since combustion deposits made by pilot oil injection cover the inside surface
of the combustion chamber. The rnethanol injection pump is of a forced
lubrication type to prevent lubrication troubles. Since metha-nol is highly
vo1ati1e, the auxiliary equipment of
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Bulletin of the M.E.S.J., Vo1. 20, No.2
Research
on Methano1-fueled Marine Diesel Engine
69
Fig.
3 Schematic Drawing of Fuel
Regulating
Linkage of
E xperimental Engine
the
methano1 system such as the fuel tank, strainer, supply
pump and valves have been
installed in an enclosed chamber (a fuel supply unit) as shown in Fig.2. A fan
and a gas detector have been installed to sufficiently ventilate the inside of
the unit for safety.
Pipe joints are also of
speciaI structure to prevent fueI leakage.
Though the dual fuel
injection system invo1-ves such a demerit that its fuel system becomes
complicated, auxiliary machinery such as generat-ing engines and a boiler burn
fuel oil on board in case of a ship, and large gain can not be expected even
though only the main engine adopts a system of burning only methanol unless
these auxiliary machines also burn only methano1. The dual fuel system is
therefore considered proper.
Fig.3 shows the schematic
drawing of the fuel
regulating linkage of the
experimental engine. In this drawing, l is the methanol injecti-on pump,
2 is the pilot oil injection pump, 5 is the governor and 31 is the actuator
necessary for controlling the ratio of the quantity of methanol and pilot oil
to be injected. To grasp the condition of deposits in the combustion chamber,
methanol with purity of 99.9% and JIS No.2 gas oil for pilot injection have
been used.
3.
Operation Test under Normal Condition
Under the full 1oad
condition of the above-m-entioned
experimental engine (mean effective pressure Pe : 16.13kgf/cm), influence on engine
performance, the contamination condition of
engine inside and Iubricating oil, and the propert-ies of exhaust gas have been
investigated by changing the specifications of the pilot oil injecti-on nozzle,
main fuel injection nozzle and main fuel injection pump, fuel injection timing
and the quantity of pilot oil.
3.I
Influence of Pilot Oil Injection Nozzle
The effect of the pilot oil
injection nozzle has been confirmed by changing the nurnber and diameter of
nozzle holes and the direCtion of injection in the range shown in Fig.4.
As a result, the one-hole
nozzle I
s the best
in terms of fuel consumption, the stability of cylin-der pressure and the
reduction in the quantity of pilot oil. However, the difference in perf0rmance
among various types of nozzles is not remarkable. As mentioned later, when
priority is given to the issues of startability, accelerating ability and sudden load change like the
engagement of a clutch, or to the problem when the pilot oil injection nozzle
ho1es have been c1osed, it can be said that the three-hole nozzle is the best
and the
October
1992
(3)
69 Yoichi
Nakamura, Tadahiro Ozu, Hisashi Yamashita, Nobuyoshi Nakayama, Tatsuo Fujii
Fig.5 Engine Performance
vs Number of
Pilot Oil
Nozzle Holes
1argest
possible nozzle hole diameter is desirable.Though the influence of the
direction of the pilot oil injection nozzle in relation to the main fuel injection nozzle has also been confirmed, no
improvement has been found. It is conjectured that the reasons for the above
are that swirls in the
combustion chamber of the
experimental engine are not strong and the quantity of pilot oil is
enough.
Fig.5 shows engine
performance when the total nozzle hole area of the pilot oil injection valve
has been kept constant (35% of the total nozzle hole area of the injection
valve for burning only oil) and the number of nozzle holes has been
changed. The two-hole nozzle
shows slightly better fuel consumption.
However, it is not preferable from the viewpoint of ignition
stability,since the variation of maximum cylinder pressure (Pmax) is large.
Fig.6 shows engine
performance when the total nozzle hole area of the pilot oil injection valve
has been changed. It has turned out that,
Fig.6 Engine Performance
vs Total Pi1ot
Nozzle
Hole Area
when the
total area is made too sma11, it becomes difficult to start the engine, and
that it is also difficult to continue the operation of the engine on
methano1/oil even if it could be started and the engine finally stops, since
the quantity of pilot oil necessary for causing perfect ignition can not be
supplied. However, when keeping the quantity of pilot oil constant, smaller
total nozzle hole area gives the better stability of pilot injection.
3.2
Influence of Methanol Injection Nozzle
Engine performance has been
confirrned using methanol injection nozzles of which the number of nozzle holes
are 8, 9, 10 and 12, and nozzle hole diameters have been selected in the range
from 0.39mm to 0.48mm (90% to 200% of the nozzle
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Bulletin of the M.E.S.J., Vo1. 20, No.2
Research
on Methano1-fueled Marine Diesel Engine
71
Fig.
7 Engine Performance
vs Number of
Methano1 Injection Nozzle Holes
area of
the injection nozzle for burning only oil).As a result, it has turned out that,
in case of the experimental engine, the injection nozzle which has ten nozzle
holes of 0.46mm in diameter, i.e.150% of the nozzle area of the injection
nozzle for burning only oil, shows the best fuel consumption.
Fig.7 shows engine performance
against the number of injection nozzle holes using intake air pressure as a
parameter when using injection nozzles of which areas have
been kept constant (130% of the nozzle area of the injection nozzle for burning
only oil) and the number of nozzle holes has been 8, 10 and 12.
Though the 8-hole nozzle
shows the specific fuel consumption on almost the same level as that for the
lO-hole nozzle, the former shows better performance, since both Pmax and exhaust
temperature are 1ower. However, it is considered in this case that thermal
1oads on the combustion chamber components become high due to the longer fuel
spray travel by about 7% than that for gas oil according to the calculation
using the experimental formula of
YAMASHITA etal.y,since the
nozzle diameter of the 8-hole nozzle is larger. Fig.8 shows measured
temperatures on the
Fig.
8 Liner Temperature vs the Number
of
Methano1
Injection Nozzle Holes
inner
surface of the cylinder liner (above TDC position of the top ring). It shows
that temperatu-res for the 8-hole nozzle are higher by nearly 401C than those
for other nozzles and the abovementio-ned conjecture is correct.
When considering the
ignition characteristic of methanol burning from the periphery of a spray, issues remain
from the viewpoint of reliability including sliding conditions, since the
quantity of atomized fue1 reaching the surface of the cylinder liner is
estimated to be more. The 12-hole nozzle shows slightly worse fuel consump-tion
probably due to the interference of sprays.According to the research by WAKURI
et al.u, the spray angle in this case becomes 17 or 18 degrees and sprays do not directly
touch each other.However, when taking account of
the behavior of sprays after impinging on the surface of the liner and the
entrainment of air into sprays, it
is thought that the limit of the number of nozzle holes is 12 or so.
Fig.9 shows test results in
the case where the nozzle diameters of the 10-hole and the 12-hole methanol
injection nozzles have been changed. No large change of characteristics has
been found
October
1992
(5)
72 Yoichi
Nakamura, Tadahiro Ozu, Hisashi Yamashita, Nobuyoshi Nakayama, Tatsuo Fujii
Fig.9 Engine Performance vs
Methano1
Injection
Nozzle Hole Diameter
even
though the diameters of nozzle holes have been changed except injection
pressure. In order to obtain sprays similar to those of gas oil, it is
necessary to use a methanol injection nozzle with the number of holes of l.5 to
2 times and a hole diameter of 1.l to 1.2 times of those of a gas oi1
injection nozzle, taking account of the spray characteristic of methanol having a shorter fuel travel
and a difference in calorific value between gas oil and methano1. However, the
number of holes is limited to 12 or so in terms of the
machining of injection nozzles in practice and injection duration for methanol becomes relatively
longer than that for gas oil. It is likely that this characteristic is
cancelled out by the high combu-stion
speed of methanol and does not badly influence the heat release periOd of a running engine so
much.
3.3
lnfluence of P1unger Diameter of Methano1
Injection
Pump
Fig.10 shows engine
performance in case where the
plunger diameter of the methanol
injection pump has been changed in the range from 22mm to 28mm.
The test has been carried
out with injection timing
being set at 23 degrees before TDC (statically) for pumps having plunger diameters from
22mm to 27mm and at 20 degrees before TDC
(statically)for the pump having plunger
diameter of 28mm, since
maximum cylinder pressure
has been predicted to exceed an al1ow-able limit in this case. As seen in this
figure, the
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Bulletin of the M.E.S.J., Vo1. 20, No.2
Research
on Methano1-fueled Marine Diesel Engine
73
injection
duration and the specific fuel consumpti-on are almost constant in the range of
plunger diameter from 26mm to 28mm. Since Pmax has an allowable limit and
injection timing must be changed when the rate of injection is increased,the
improvement in fuel consumption is small even though the plunger diameter of
the metha-nol injection pump is made too large. It can therefore be said that
the limit to the plunger diameter is about l.3 times of that for only oil
burning.
It can be seen from Figs.11
and 12 that the influence of the plunger diameter on the distribut-ion of heat
release rates and on injection pressure and the lift pattern of the needle
valve becomes smal1.
3.4
Influence of Injection Timing
Fig.13 shows engine
performance in case where the injection timing for
methanol has been kept constant and that for pilot oil has been changed. As
seen in this figure, the engine
performance
becomes better in case where pilot oil is injected earlier by two degrees than
metha-no1. Though the test where pilot oil is injeCted later than methanol has
also been carried out,combustion
has not stabilized and continuous
running has been difficult. Another test has also been carried out, where the
relative difference in injection timing between methanol and pilot oil has been
fixed and the timing for both fuels has been advanced in parallel. However it
haS turned out that the improvement in fuel consumption is smal1.
3.5
Influence of the Quantity of pilot Oi1
Fig.14 shows engine
performance in case where the
quantity of pilot oil has been changed for each pilot oil injection nozzle. It
can be seen from this figure that the lowest points of specific fuel
consumption differ with the specifications of pilot oil injection valves. That
is, the percentage of pilot oil in total consumed fuel for the lowest point of
specific fuel consumption is between l1 and 12% for the one-hole nozzle and
that is near 15% for the three-hole nozzle. Thus, the lowest point shifts toward
the larger percentage of pilot oil. Though the quanttty ot piLot aiL can be
decreased down to about 4% by making the pilot oil injection nozzle area
smaller, proper quantity.is
October 1992
(7)
73 Yoichi
Nakamura, Tadahiro Ozu, Hisashi Yamashita, Nobuyoshi Nakayama, Tatsuo Fujii
considered
to be 12-15% in practice, since the startability of an engine must be
considered as mentioned later.
Smoke density and NOx have also been measured during these tests.
Though detailed results
will be explained later, the results can be summarized as fol1ows. Compared
with a diese1 engine being operated on gas oil, the smoke density is 1ower by
one order by Bosch scale and NOx is sbout half under the same load
condition.Thus, exhaust gas characteristics
have been confirmed to be
superior. Furthermore, overhaul inspection and the results of
lubricating oil analysis
after tests have shown less contamination of the engine inside. As mentioned
above, it has been confirmed that the possibility of lowering environmental
pollution and decreasing maintenan-ce work for diesel engines is large.
4.
Starting Test
4.l Test
Method
The stable combustion of
dual fuel engines under normal operation can be ensured by pilot oil of several
percent of total fuel which is injected under full 1oad condition. However, a considerably large quantity of fuel
is needed when starting engines, since accelerating
torque is necessary in
addition to normal running torque.
For this
reason, starting tests have been carried out under the fol1owing conditions.
a) Constant quantity of methano1 (full
1oad)
and
varying quantity of pilot oi1
b) Constant quantity of pilot oil and
varying
quantity
of methano1
c) Operation on only pilot oi1
d) Starting on pilot oil and injection of
metha-
nol after
that
e) Constant quantity of methano1 (50%) and
varying
quantity of pilot oi1
For al1 conditions
except e), cold conditions of intake air temperature ts # 191C , cooling water
temperature tw t 191C , 1ubricating oil temperatu-re to # 201C and liner
temperature tL # 201C have been adopted. For a part of e) condition,warm
conditions of ts t 301C , tw # 58 C , to # 50 t and tL # 391C have been
adopted.
4.2 Test
Results
Fig.15 shows the summaries of test
results
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Bulletin of the M.E.S.J., Vo1. 20, No.2
Research
on Methano1-fueled Marine Diesel Engine
75
taking the
quantity of pilot oil on the abscissa and that of methanol1 on the ordinate. .
mark shows that no ignition has been detected. } and J marks show that,
though ignition has been detected, it has not been continued and torque has not
been generated. > and O marks show that ignition has been detected and
continued stably and engine speed has risen up to its set speed. Suffixes show
test numbers.
As can be seen from this
figure, under the cold condition (0 J .), ignition has not been detected at all
like Test Nos. 1-5 in case where a large
quantity of methanol has
been injected together with oil.
On the other hand, under the warm condition (O }) like engines just after
operation, starting has been possible like Test Nos. 21, 22 and 13. However,
there has been an example such as Test No.12 where operation
could not
be continued due to pilot oilless by few percent than that of Test No.13. When
pilot oil is plenty, starting even under the cold condition is possible like
Test No.25 even though a considera-bly 1arge quantity of methanol is injected.
Test Nos.8, 9 and l0 have been carried out in such a way that the engine has
been started on only pilot oil and methanol has been injected after detecting
ignition. These are examples where the engine has misfired and not generated
effective torque and operatiOn could not be continued because of much methanol and less pilot oil. It has
turned out that, since pilot flames are blown out by the injection of meth1no1,
energy necessary for starting can not be made up by methanol and a necessary
quantity of pilot oil must be inj:?cted under the cold condition.
Fig.16 shows the transition
of engine speed for Test Nos.3, 7, 11
and 13 which have been carried out under typical starting conditions.
Test No.3 shows the case where methano1 of the quantity
corresponding to the limit of the injection pump rack has been injected
under the cold condition. Engine speed rises up
to only that by starting air. Test No.7 shows that accelerating torque is not
generated though slight ignition is detected, because the quantity of methanol
has been decreased to 30%.
Test No.11 shows the case
where only pilot oil is injected. Though the rate of speed increase is smal1,
engine speed rises up to the set speed.Test No.13 shows the case where methanol
of the quantity of 50% has been injected under the warm condition. It can be seen that engine speed quickly rises by the
combustion of methano1.Fig.17 summarizes the results
of starting tests using
accelerating time and mean effective
pressure (Pmi) obtained from indicator diagrams as coordinates. O and X marks
show cases where starting has succeeded and failed respectively.The solid line
shows the relationship between minimum mean effective pressure necessary for
accelerating engine speed which has been calcula-ted from mean accelerating
torque and accelerat-ing time. It can be seen from this figure that,apart from
the length of accelerating time related to inertial mass, Pmi of at least 4 or
5 kgf/cm2 must be generated for starting engines.
5. Quick
Load Throw-in Test
5.l Test
Method
Tests simulating the
condition of engaging clutches which are often installed on medium to
October
1992
(9)
76 Yoichi
Nakamura, Tadahiro Ozu, Hisashi Yamashita, Nobuyoshi Nakayama, Tatsuo Fujii
Fig.
18 Procedure8 of Quick Load
Throw-in Test
high speed
engines have been carried out by
quickly throwing-in 1oads on the dynamometer (eddy current type) according to
the procedures shown in Fig.18. Rotating mass is added between the engine shown
in Fig.l and the dynamometer to be able to simulate a shafting of a marine
engine. The engine has been imposed with a load during four or five seconds
after changing over from oil operation to
methano1/oil operation
under no lobd condition, and engine speed and pressure in the
cylinder have been recorded.Supposing the loaded condition of an engine after
engaging a clutch, 1oads (40-150 kgf ) correspondi-ng to 20-70% of the load at
full engine output and also the quantity of
fuel to be injected corresponding to these loads have been selected.For
intake air pressure, two cases of naturally aspirated and
supercharged (0.35 kgf/cm) conditions have been selected.
Since intake air of this experimental engine is supplied by an indep-endent
motor driven blower, the transient chara-cteristics of a turbocharged engine
can not be simulated exactly. However, it is considered that engine
characteristics can qualitatively be grasped by this test.
The governor of this engine is Woodward
UG8 type
with a torque limiter. The test has been carried out by controlling the
quantity of pilot oil with the lever 34 and that of methanol by limiting the
output of the lever 6 with the torque limiter of the governor in Fig.3.
5.2 Test
Results
Fig.19 shows the test
results of the quick load throw-in test. Measured points are p1otted by
selecting Pmi, which has been converted from a dynamometer load, for the abscissa and the
percentage of methanol injected, which has been calculated from the rack position
of the injection pump, for the ordinate.
In this figure, ^ , O , O ,
and O' marks show cases where engine speed has returned to its set values after
quickly imposing loads ; ^ ,., . and .'
marks show cases where the engine has stalled and could not
carry loads ; and J , J' and > show cases where the engine had not sta1led
but the engine speed has not returned to its set values. Suffixes show test
numbers.
The magnitude of load which can
be thrown-in is effective only in the hatched range under naturally aspirated condition
and the engine output is limited to Pmi =
9-1Okgf/cm2. Since this limit can not be raised even under the warm condition,
it is not influenced by the phenomenon of
blowing out pilot flames by methanol as
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Bulletin of the M.E.S.J., Vo1. 20, No.2
Research
on Methano1-fueled \4arine Diesel Engine
77
detailed
under the section of starting test, and it is thought that output can not be
increased due to the shortage of intake air even though the quantity of
methanol is increased. It can be seen from examples marked with O' that the
limit of output can considerably be increased by d small degree of
supercharging and Pmi of 12.5kgf/cm2 can be developed. It means that the
magnitude of load which can be thrown-in, i.e. the speed of engaging the c1utch
(the rising speed of oil pressure
for operating the clutch), depends on the accelerating ability of the
turbocharger and it can be said that the clutch must be operated linking with
intake air pressHre. The quantity of pilot oil has almost no influence on the
limit of output in the range shown in Fig.19. Fig.20 and 21 show the transitions
of engine performance after load throw-in under naturally aspirated condition
and under supercharged condition wiht the intake air pressure of 0.35kgf/cm2
respectively. Though Pmi #
1Okgf/cm2 can be obtained just after load acceptance in every case under
naturally aspirated condition, the balance between generated engine torque and
load can not be maintained due to the shortage of air (small air/fuel ratio)
and the cooling effect by the latent heat of vaporization of methanol when the
quantity of injected methanol is
much. Both Test Nos.19 and 25 have this
tendency,
and engine speed lowers halfway and
can not
recover.
Under supercharged condition, the engine generates Pmi # 15kgf/cm2 and
engine speed quickly returns to the set value, since a conside-rably large
quantity of air, i.e. specific air consu-mption 4kgf/PSh, is supplied to the
engine. Test Nos.41 and 42 show the cases where the engine can not develop
enough output because of too little quantity of injected methanol against the
thrown-in engine load. As mentioned before, the experimental engine does not represent the dynamic characteristics of actual turbocharged engines,
since the experimental engine is not equipped with an exhaust turbocharger.
However,it is expected that the above-mentioned
load throw-in test can offer matters to be considered when methanol is
applied to diesel engines.
6.
Conclusion
Tests have been carried out
under static and dynamic
conditions in order to grasp engine performance when methanol is
applied to marine
October
1992
(11)
78
Yoichi Nakamura, Tadahiro Ozu, Hisashi Yamashita, Nobuyoshi Nakayama,
Tatsuo Fujii
diesel
engines. As a result, it has turned out that the performance
of a methano1/oil burning engine can be improved near to the performance level
of an oil burning engine by optimizing the fuel injection sysytem and the
combustion chamb-er geometry and by adapting the fuel regualting system and tbe
intake air system of the former.
7.
Acknowledgements
This research has been
carried out in co-op-eration with KOKKA SANGYO, coastal Shipping company, and
HANSHIN Diesel Works, engine manufacturer for coasters. The authors wish to
express our deep gratitude to people concerned.
Discussion
Yasuhiro
Ito (NIICATA ENGINEERING CO.,LTD.)
I pay my respects to you
for your presentation of valuable research. I am happy if you give me your
answers to the fol1owing two questions.
1. How do you evaluate
the properties of
exhaust
gas from the viewpoint of low environmental pollution ?
To what
extent does NOx in particular decrease in comparison with diesel engin-es ?
I think
soot is more or less influenced by pilot injection. How do you think about this
matter ?
2. Please let me know if there is any
point to
be particularly noted in the
respect of d urability.
Author'8
reply
1. Though exhaust
emissions which are
problematical
are formaldehyde and unbur-ned methano1, they are not so much probl-ematical in
marine engines compared with automobile engines. NOx was from 2/3 to 1/2 of
that of gas oil burning engines,since the combustion temperature of met-hanol
was 1ow.
Soot was
so little that it could hardly be measured by a Bosch smoke meter in spite of
pilot injection.
2. Though we were worried about the occur-
rence of
piston ring scuffing, we could confirm that no problem would occur by selecting
proper lubricating oil. However,for the durability of the methanol injection
system, we experienced the stick of the plunger and the corrosion and breakage
of the spring.
On these troubles,
we are scheduled to present in detail at the autumn lecture
meeting. Pleae see this paper.
Keijiro
Shiode (SHIP RESEARCH INSTITU-TE )
I pay my respects to you
for your presentation of very valuable experimental data. Please let me know if
you have experienced any trouble on the fue1 injection valve when alcohol fuel
has been used.
Author's
reply
On the trouble of the methanol
injection system, we are scheduled to present in detail. Please see this
paper. Though we experienced the wear of the needle valve and the corrosion
and breakage of the spring due to the low viscosity and corrosiveness of
methano1, we could solve these troubles
by changing their shapes and
materials.
Hiromi
Kondo (DAIHATSU DIESELMFG.CO., LTD.)
I pay my respects to you
for your valuable research on the combustion of methano1. Please give me your answers to the
fol1owing questions.
1. What phenomenon can I think about by
the
description
"In case the quantity of injected oil is the same, smaller area of nozzle
holes is ..." on Page 70 in the text ?
2. Please tell me the locations of
measuring
points for
liner temperature and of the pilot oil nozzle in Fig.6.
3. Please tell me the process of
calculating
Pmi from
mean accelerating torque shown in Fig.6 on Page 70.
4. How should I consider compression
ratios
for
methanol engines ? I should be obliged if you would tell me the compression
ratio used in this experiment.
Author's
reply
l. The pilot
injection system actually has considerably
larger capacity than that necessary
for normal operation, taking account of engine starting and the engag-ement of a
clutch. Consequently, injection characteristics under normal operation tend to
deteriorate. It is therefore necessary to throttle nozzle area to maintain
necessary
(12)
Bulletin of the M.E.S.J., Vo1. 20, No.2
Research
on Methano1-fueled Marine Diesel Engine
79
injection
pressure.
2. Eight sensors for measuring liner
tempera-
ture are
inserted on the periphery of the liner at intervals of 45 degrees and the pilot
oil injection nozzle is located near the periphery of the combustion chamber.
The difference in liner temperature which was thought to be due to pilot flame
was not observed .
3. Though the rate of engine speed
increase
after
starting is not uniform, this minimum Pmi curve has been made by the way of
thinking of the mean rate of acceleration for the sake of simplification to
investigate its tendency. Friction torque has been made constant.
4. Though tests with various compression
ratios
were not conducted, we think the compression ratios for engines with pilot
injection can be considered in the
same way as those of oil burning engines. Tho-ugh the compression ratio of the
experimental engine is the same as that for the case of burning only oil (
E = 13), the
effective compression ratio becomes higher than that for the case of burning
only oil,since the timing of intake valve c1osing is advanced a little.
References
(1)
Yonebayashi A., "Activities of IMO MEPC regarding exhaust enlission fron-1
ships", Pre-text of the 47th M.E.S.J-Conference, p.l44,199l.
(2) Hikino
K., et al, "Recent trends of ignitability improvements on methanoI diesel
en9ines", Journal of S.A.E.J,
vo1.44, No.8,p.92, 1990.
(3)
Yamashita H., et aI, Journal of M.E.S.J,vo1.26, No.9, 1991.
(4) Wakuri
Y., et al, Transaction of J.S.M.E,256-156 (24-8), p.820.
October
1992
(13)