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Formulation and results of a CFD code for internal combustion engine are given in the paper. The CFD code, developed in-house, has proved helpful in studying the flow patterns like swirl, squish, tumble, and turbulence generation. Through numerical tracing of mass less particles, good idea about the possible stratification patterns is obtained. For GDI engines, where a very specific stratification pattern is required, geometry optimization is required. This code has proven useful in this regard. Results for two different configurations show that some changes in combustion chamber geometries prove helpful in achieving desired stratification patterns. This exercise would have taken huge efforts and resources, if done experimentally.

In a dual fuel engine a primary fuel that is generally gaseous is mixed with air, compressed and ignited by a small pilot spray of diesel as in a diesel engine. Dual fuel engines suffer from the problems of poor brake thermal efficiency and high HC emissions, particularly at low outputs. In the present experimental work, the effects of intake charge temperature, pilot fuel quantity, exhaust gas recirculation and throttling of the intake on improving the performance of a LPG-diesel dual fuel engine have been studied. Results indicate that at low outputs an increase in the intake temperature and pilot quantity is advantageous. HC level generally reduces with increase in pilot quantity and intake temperature. Exhaust gas recirculation (EGR) coupled with intake heating raises the brake thermal efficiency and lowers HC emissions. With throttling and EGR there is a significant reduction in the HC levels and an improvement in brake thermal efficiency at low loads.

A finite difference scheme comprising of two step Lax-Wendroff and Leap-frog techniques used to solve the continuity and momentum equations for a fuel injection system, is described in this paper in addition to the method of characteristics. Newton-Raphson method and Becchi's techniques have been tried to solve the boundary condition equations. A limited comparison with the well known Runge-Kutta scheme showed that the Newton-Raphson method is much simpler to apply and needs lass computational time. The validation of the above model has been carried out by comparing the predicted and experimental data of the fuel injection pressures and rates. This comparison showed that the present model could be utilized to predict the performance of the injection system with a reasonable degree of accuracy.