Developmental Research on Computer Aided Analysis and Design of an Engine Combustion System

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A quantitative analysis of fuel vapor concentration in a fuel sprayh was made for obtaining fundamental knowledge of mixture formation which was necessary for the development of a sumulation program of diesel engine combustion. For this purpose, the technique for processing the spray image taken by the schlieren and shadow photography was developed, and applied to the axisymmetric spray in a high-pressure and high-temperature atmosphere. Internal structure of the spray distorted in a cross air flow was analyuzed by combining this image processing technique with the program for the computed tomographic transformation. Several informations obtained through these analysed were incorporated into the simulation program of the diesel engine combustion, which was composed of an air flow sub-program, and a mixture formation and combustion sub-program. The air flow sub-program was created for mainly predicting the swirling air flow during a compression stroke, especially at fuel injection timin … More g. Taking the computational cost and accuracy of into consideration, a two-zone model was adopted, and the angular velocities of the swirling air flow in the zones inside and outside the piston cavity radius were computed. The principle consideration of the mixture formation and combustion sub-program was to find the injection and combustion chamber parameters matching with the swirling air flow, and to predict the over-swirl phenomenon. The comubustion chamber was mapped with non-uniform rectangular soulid cells in cylindrical coordinates. The conservation equations for fuel vapor concentration, combustion product concentration and gas enthalpy were discretized in a finite difference technique. By numerically solving these conservation equations, the spatial distributions of fuel vapor concentration, combustion product concentration and gas temperature were obtained. The comparison between the computed result, and the angular velocity measured with the laser doppler velocimeter and fthe flame behavior observed in a high-speed combustion movie, demonstrates the potential of this simulation program. Less