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The new combustion method in DISC engine has been developed. It has a double structure combustion chamber characterized as ‘Caldera’. The chamber is constructed by a center cavity for the purpose of forming a stable mixture around a spark plug electrode, and by an outer cavity which has a role of a main chamber. This method makes possible a perfect un-throttling operation, and a fuel consumption equal to a diesel engine is achieved. With regard to an out-put of DISC engine, a stoichmetric combustion and a high torque are achieved by controling a fuel injection timing with an electro-magnetic injection system device. With regard to emission regulations, a heavy EGR include residual gas decreases greatly NOx and HC emissions simultaneously, and which suggests a possibility to achieve LEV/ULEV regulations.

The study of the phenomena of in-cylinder flow, spray and combustion by measurement and calculation has been vigorously pursued, because thermal efficiency and emissions of the D. I. diesel engine are influenced by them. To investigate the effects of in-cylinder flow on spray and combustion, the D. I. diesel engine simulation model has been developed. This model is composed of in-cylinder flow, spray and combustion models. In the spray model, spray non-uniformity is considered, and physical and chemical processes are considered in the combustion model. The effects of swirl, number of nozzle holes, injection pressure and squish area on thermal efficiency and emissions have been investigated, and the existence of optimum values of these parameters against thermal efficiency have been predicted and these predictions have been verified by measurement.