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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.

Premixed diesel combustion modes including low temperature combustion and MK combustion are expected to realize smokeless and low NOx emissions. As ignition must be delayed until after the end of fuel injection to establish these combustion modes, methods for active ignition control are being actively pursued. It is reported that alcohols including methanol and ethanol strongly inhibit low temperature oxidation in HCCI combustion offering the possibility to control ignition with alcohol induction. In this research improvement of diesel combustion and emissions by ethanol intake port injection for the promotion of premixing of the in-cylinder injected diesel fuel, and by increased EGR for the reduction of combustion temperature.

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.