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The characteristics of exhausted smoke of a methanol DI diesel engine which is ignited by diesel fuel are investigated to clarify the soot formation process. At this engine, very little smoke is exhausted when diesel fuel is kept below a certain amount, so soot and smoke emitting characteristics are studied under the various diesel fuel amounts. By analyzing microstructure of soot, it is found that the soot emitted from the methanol diesel engine is composed of inner core and outer shell, similar to that of the conventional diesel engines. From more detailed qualitative analysis, the calcium percentage from the lubricating oil in outer shell is much higher than that of the conventional diesel engines. In consideration of soot characteristics, spray structure and combustion characteristics, the soot formation process of the methanol diesel engine was clarified.

Ignition and combustion control of HCCI (Homogeneous Charge Compression Ignition) in DI (Direct Injection) Diesel Engine were examined. In this study, double injection technique was used by Common Rail injection system. The first injection was used as an early injection for fuel diffusion and to advance the changing of fuel to lower hydrocarbons (i.e. low temperature reaction). The second injection was used as an ignition trigger for all the fuel. It was found that the ignition of the premixed gas could be controlled by the second injection when the early injection was maintaining low temperature reaction. It was found that as the boost pressure increased, ignition timing advanced slightly and the rate of pressure increase markedly decreased. The rate of pressure increase is one of the factors concerning operation limit in this combustion. Therefore, the VNT (Variable Nozzle Turbo-charger) was applied to the production engine to allow boost pressure control.

The UNIBUS (Uniform Bulky Combustion System) based on the HCCI (Homogeneous Charge Compression Ignition) concept uses an early injection quantity, timing, boost pressure, EGR, etc. for ignition control [1]. To further expand the operation range from the present level, the effects of the atmospheric conditions on ignition and combustion were calculated using CHEMKIN in the present study. When controlling the start timing of the high temperature reaction to suppress the early ignition, it is more effective to apply EGR than boost pressure. If fuel quantity is increased to expand load, it is possible to suppress a sharp cylinder pressure rising rate by increasing the boost pressure. Furthermore, it has become apparent that the cause of this is an increase in heat capacity.

Abnormal fuel injection in light-duty, high-speed diesel engines was analyzed by developing a mathematical simulation program. It predicts the transient hydraulic phenomena and the dynamics of the mechanical components by applying the injection system design data. The results show the existence of marked changes of injection quantity against residual pressure, cavity content and pump speed, in the case of abnormal fuel injection. Closer observation reveals that the injection rate change from two-stage to one-stage causes a marked change in injection quantity.