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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.