4.

Task 44.1

Development of Power Generation Technology

R & D Targets

4.1.1
(1)

Development Targets for WEWE - NET Phase II (FY 1999 – FY 2003)
Development of a single cylinder 100 kW class hydrogen combustion diesel

engine for the purpose of developing an open-cycle hydrogen combustion diesel engine(600 kW class) with a thermal efficiency of approximately 40% after Phase II of theWE-NET Project.
(2)

Implementation of the performance test of the developed single cylinder engine

to identify R & D targets for the practical application of such an open-cycle hydrogencombustion diesel engine.
4.1.2
(1)

Targets for FY 2001
In relation to the element technologies for an open-cycle hydrogen combustion

diesel engine system, the function and capability of a developed hydrogen injection
unit is confirmed through testing; as for the engine system the building of a single
cylinder test diesel engine as well as testing facilities (a hydrogen diesel engine
laboratory building, a hydrogen compressor and a gas supply unit) for it is completed.
(2)

Numerical analysis of the phenomena in the hydrogen combustion diesel engine

is made, so that the results will be reflected in the process of engine development.
4.2
4. 2

Results on Accomplishment in FY 2001

4.2.1

Development of Element Technologies(1)Development of Hydrogen Injection Unit
Atest

wasconductedtoconfirm

theproperfunctioningof

theelectronically-controlled and hydraulically-actuated hydrogen injection unit for theexperimental 100 kW class single cylinder diesel engine and the proper operation ofthe injection valve, solenoid controller and hydraulic unit was confirmed. The
injection duration at the rated power condition was found to be approximately 40° by
crank angle compared to the target of 25° crank angle.
4.2.2
(1)

Investigation of the S ingle Cylinder Test Engine System

Study on Measures to Improve Thermal Efficiency

The thermal efficiency of two types of diesel engines fueled with hydrogen anddiesel fuel was calculated for comparison from the P-V diagram for the diesel cycle.
The comparison showed that at the same compression ratio, the indicated thermal-31-

efficiency of the hydrogen combustion engine is lower than that of a corresponding
diesel engine because of the increased quantity of water vapor generated bycombustion but that it is almost the same as that of a corresponding diesel engine
when a lower air supply pressure and a higher compression ratio are employed for thehydrogen combustion engine exploiting the fact that the air volume per quantity ofheat due to combustion is less.
Investigation of the jet using the spray momentum theory concluded that thehydrogen jet has twice the excess air ratio of that of diesel fuel. This finding suggeststhat the thermal efficiency of the hydrogen combustion engine is improved because of
its shorter heat release period than that of an engine using diesel fuel.
As a result of engine performance simulation calculation, if the present heatrelease period of some 100° crank angle is shortened to 80° by means of fast
combustion, the development target for the hydrogen combustion engine, i.e. 2%
higher than the thermal efficiency level of a corresponding engine using diesel fuel, isexpected to be achieved.
(2)

Study of Ignition

The possibility of the self-ignition of a hydrogen combustion engine with a highcompression ratio was investigated in view of the compression temperature of theworking gas and the results of the fundamental test on self-ignition conducted in FY1998. It was found that the self-ignition of hydrogen is possible at normal air supply
temperatures but that an ignition system is necessary at the time ofstarting when

the temperature of supply air is not enhanced by compression in the compressor of
the exhaust turbocharger.
(3)

Study of NOx Reduction Measures

According to a report by MAN B&W for a high pressure injection-type hydrogen
combustion engine, the NOx emission level is as high as 10g/kWh at an early
injection timing. Based on this estimation the NOx emission needs to be reduced to1/30 to meet the strictest emission standard of 0.35g/kWh for gas engines regulated
by municipal authorities.
It was also found that in the case of hydrogen being supplied in liquid form, the aircharge cooling obtained by taking advantage of the cold heat from the liquid hydrogenis effective to reduce NOx emission.
4.2.3
(1)

Construction of Single Cylinder Test Engine System

Construction of Test Engine

A single cylinder test engine for an open-cycle hydrogen combustion engine wasconstructed. A conventional-type single cylinder diesel engine originally designed for-32-diesel fuel was built and its fuel injection system was replaced by a hydrogeninjection unit. Fig. 4.2.3-1 is a photograph of this engine.

Fig. 4.2.34.2.3 - 1

Assembly of Single Cylinder Test Model-33-(2)Construction of Test Facilities

A laboratory building for the testing of the hydrogen combustion engine wasconstructed and a gas supply unit and a hydrogen compressor were installed in thelaboratory. Fig.4.2.3-2 presents the external view of the laboratory building.
Figs.4.2.3-3 and4.2.3-4 are photographs showing the installation of the hydrogen tankand the hydrogen compressor respectively.
(3)

Installation of Instruments and Electric Dynamometer

Instruments to measure and record the test data of the single cylinder hydrogen
combustion engine were installed inside the operation control room.

Fig. 4.2.34.2.3 - 2

External View of Laboratory Building-34-

Fig.4.2.3
Fig. 4.2.34.2.3 - 3

Fig.4.2.3
Fig.4.2.34.2.3 - 4

Hydrogen Tank

HydrogenHy drogen Compressor-35-

4.2.4(1)

Numerical Analysis

Investigation of Self-Ignition of Open-cycle Hydrogen Combustion Diesel Engine

In order to study the conditions for self-ignition of hydrogen under the air open
cycle, combustion analysis of hydrogen jets was conducted where the ambient gas waschanged from argon to air and the compression ratio was increased to increase thecompressed

airtemperature

inthecylinder.

The

calculation

revealed

that

self-ignition occurs when the air temperature is 1,000 K or higher at the time ofhydrogen injection but that it does not occur if the temperature is below 900 K.
(2)

Verification of Hydrogen Combustion Model

In order to conduct the numerical simulation of the combustion process of thehydrogen jet, a combustion analysis model was conducted, and the calculated results
were compared with the laboratory test results to verify the model. For this analysis,an analysis model was constructed that combines the piston (a miniature model of
one-quarter sector form of a real piston) and an injector with two nozzle holes used ina combustion test using a rapid compression/expansion machine in FY 2000. The
combustion of hydrogen jet was simulated using the model combined with a chemical
kinetic model. As the simulated results of the cylinder pressure showed goodagreement with the experimental results, it was concluded that the analysis ofhydrogen jet combustion for actual engines is feasible.
4.3
4. 3

R & D Themes in the Future

4.3.1

Development of Element Technologies for Hydrogen Injection Unit

Following the simulation exercise using actual data to examine possible measures toshorten the injection period, reduction of the mass of the moving parts (an actuatingpiston and a needle valve), strengthening of the spring force and matching of theorifices at the inlet and outlet of the working fluid will be attempted.
4.3.2
(1)

Development of Single Cylinder Test Engine System

Development and Testing of Ignition SystemThe self-ignition characteristics of a hydrogen combustion engine with a higher
compression ratio than that of a conventional diesel engine will be evaluated using asingle cylinder test engine to clarify the air supply conditions and the ranges of theload and speed requiring forced ignition. Following clarification of these issues, thetype of ignition unit and its installation location will be selected. The important
points to be considered for such selection are that ignition energy can be supplied tothe location where combustible mixed gas exists and at the right timing and that theignition system has sufficient durability.

-36-(2)Basic Performance Test

Basic performance data on the thermal efficiency, exhaust gas emission andtemperatures on the combustion chamber will be obtained through the testing of thesingle cylinder test engine of which the specifications do not incorporate measures toimprove the thermal efficiency and to reduce the NOx emission of a hydrogen
combustion engine.
(3)

Thermal Efficiency Improvement Test

The thermal efficiency improvement effect due to a lower air supply pressure and ahigher compression ratio for a hydrogen combustion engine will be evaluated. Inaddition, the effect of shortening of heat release duration on the improvement ofthermal efficiency will be evaluated by shortening of the fuel injection period andmixing enhancement with an optimized air swirl in the combustion chamber.
(4)

NOx Reduction Test

The effects of measures relevant to combustion, including exhaust gas recirculation,
will be evaluated. The feasibility of NOx reduction by way of the combination of theabove measures and the application of an after treatment system using a selective
catalytic converter.

-37-