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The industrial diesel engines are used in many types of applications, and the market has strong needs for low-cost, compact, high-output and high-reliability. In addition, exhaust emissions regulations for industrial diesel engines are being strengthened and all engines must conform to all of them. Therefore, low-emission is an essential condition. This paper describes attempt of optimizing the shapes of an inlet port and a combustion chamber to achieve high power and low emission using Computational Fluid Dynamics (CFD). In addition, a new water passage structure was developed against increasing thermal load caused by high outputs and improved reliability and durability. High-stiffness ladder-frame was employed at crankshaft supports to achieve low noise and low vibration, and gear train was placed on the flywheel side to reduce gear noise.

In order to realize the stratification of mixture within a port injection gas engine, an experimental engine having two intake ports (i. e. swirl and straight port) per cylinder was prepared and investigations were made to see the effect of injection position on in-cylinder fuel distribution. To understand the flow within the engine, CFD calculation and PIV measurement were carried out and the effects were examined. Also firing tests and the measurement of in-cylinder fuel distribution by LIF method were conducted with the various injection positions to verify the predictions. As a result, it was found that the performance of the engine was affected by the injection position and proper charge stratification was realized by injection into a certain area of the intake port.

In order to see the effect of injection timing and directions on the performance of a DI gas engine, an experimental engine was prepared, and firing tests were carried out. Also a laser induced fluorescence method was used to see in-cylinder fuel distribution. As the result, following conclusions were obtained. 1) NO2 could be used as a tracer substance to visualize in-cylinder gaseous fuel distribution. 2) Injection timing had large influence on the fuel distribution and the performance of the DI engine. 3) In-cylinder fuel distribution and operation stability of the DI engine was also affected by injection directions.

The influence of injection timing on the performance of a manifold injection gas engine was investigated with the results of firing tests. Also the in-cylinder fuel distribution of the engine was measured by a tracer LIF method and used to understand the results of the firing tests. These results showed that the in-cylinder fuel distribution of the engine in the direction of a cylinder axis was changed by the variations of injection timing.

This paper studied suitable methods to use reformed gas (H2 67% and CO 33% mixed), hydrogen as alternative fuels for an internal combustion engine. Both the internal mixture formation and the external mixture formation were studied. PIMGI (Port and Intake Manifold Gas Injection) engine of the external mixture formation was equipped with two electro-magnetic injectors per cylinder. One injector was installed in the intake manifold for the homogeneous mixture and the other was installed near intake port for stratified charge. The fuel pressure for PIMGI was 0.8 MPa. In GDIC (Gas Direct Injection into Cylinder) engine of the internal mixture formation, the gas injector driven by the hydraulic pressure was installed in the cylinder head. The fuel pressure for GDIC was 5.0 MPa. In the GDIC, the fuel was injected early after intake valve was closed because the gas pressure was relatively low for direct injection.