Development of General-Purpose Computer Programs to Predict the Performance of Four-Cycle Internal Combustion Engines for Improving Their Thermal Efficiency

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A simulation program has been developed to predict the engine performance, achieving little numerical diffusion by the use of teh characteristic method with two mesh series. The dimension effect of the intake system on the EGR rate has been estimated for a four-cylinder engine. The availability of the program is recognized by the good agreement between the calculated and experimental results. A scheme to calculate the shock wave in pipes has been fundamentally investigated. A new procedure to perform characteristics has been developed and found to provide accurate and efficient evaluations of gas flows in pipes including the gas flow in a tapered pipe or gas flow with numerical diffusion. The flow characteristics of the turbine and the compressor used in compound power systems have been expressed as function forms containing several parameters. These enable us to evaluate the performance of compound power systems with their various configurations.In three-dimensional analysis of the pressure wave and the gas flow in intake and exhaust systems, the CIP method has been improved by applying the general curvilinear coordinate transformation in order to calculate the gas flow and pressure wave in arbitrarily-shaped passages such as silencers. The effect of the configuration of silencers on the attenuating characteristics and the pressure losses has been made clear by examining the calculated results. For numerically analyzing three-dimensional gas flows in engine intake ports and combustion chambers, a calculation method (GTT) which can deal with engine models having complicated shapes by using body-fitted grids has been developed. The forming and collapsing processes of tumbling vortices have been made clear using the GTT program. By incorporating fuel spray models into this program, the behavior of fuel droplets and the distribution of fuel vapor concentration in liquid fuel injection engines have been predicted.