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When the compression ratio of the spark ignition engine is set high as a method of improving the fuel efficiency of passenger cars, it is often combined with the direct fuel injection system for knock mitigation. In port injection, there are also situations where the fuel is guided into the cylinder while the vaporization is insufficient, especially at the cold start. If the fuel is introduced into the cylinder in a liquid state, the temperature in the cylinder will change due to sensible heat and latent heat of the fuel during vaporization. Further, if the fuel is unevenly distributed in the cylinder, the effect of the specific heat is added, and the local temperature difference is expanded through the compression process. In this research, an experiment was conducted using a rapid compression machine for the purpose of discussing the effect of the temperature-pressure time history of fuel on ignition delay time.

As for homogeneous charge compression ignition (HCCI) combustion, many parameters influence on self-ignition timing. We formulated a self-ignition timing simulation model. A control algorithm for HCCI engine has been formulated on the basis of this self-ignition timing simulation model. And the application of the control algorithm to a 4-cylinder engine provided with an electromagnetic valve train demonstrated that it was possible to control HCCI combustion in response to operating conditions. In addition, when switching between spark ignition and HCCI operation, the control algorithm for HCCI engine compensating for the difference in exhaust temperature and the fuel wall-wetting compensating algorithm have enabled switching without torque shock.

Auto-ignition may be considered as the ultimate combustion process for vehicle engines. Regarding combustion control, ignition timing and heat release are the chief concerns. The former is finding a solution, however the latter has, as yet, several approaches. As a means to control the heat release, this paper introduces a universal parameter; ΔT, which is the difference between the adiabatic flame temperature and the initial in-cylinder gas temperature before combustion. Firing tests of a four-stroke auto-ignition gasoline engine revealed that the heat release process could be successfully controlled when ΔT was maintained at a proper level. As a result, the auto-ignition zone was greatly enlarged in the tested engine with a moderate compression ratio.