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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.

Pilot fuel quantity and intake temperature are two important parameters controlling the combustion process in dual fuel engines. Experiments were conducted on a LPG diesel dual fuel engine at various intake temperatures and pilot quantities. Ignition delay, rate of pressure rise, combustion duration and heat release patterns have been presented at low and high loads. An increase in the concentration of the gaseous primary fuel significantly increased the ignition delay. At high outputs the combustion of the gas by flame propagation which follows the ignition process of the pilot and the entrained gas was the dominant feature. However, at low loads combustion of the pilot fuel and the gas entrained in it were only significant.. The rapid combustion of the gaseous fuel at high output conditions, particularly when the intake temperature was high, resulted in rough engine operation.

In the past, a number of reported developments have indicated the problems of high specific output engines and the special measures to combat these problems, namely Atkinson cycle, low and variable compression ratio, manoeuvring timing and rate of injection, multiple introduction of fuel etc. Recent studies have shown that low heat rejection and turbocompounding could be applied to existing engine series to improve fuel economy. As experimental evaluation of the effectiveness of above measures for a single system is a complex and costly task, this paper reports a systematic analytical investigation using diesel cycle simulation in which the potential of each measure in terms of specific output and fuel economy has been assessed and compared with other alternatives when a diesel engine is uprated from naturally aspirated mode.

The present reserves of liquid petroleum fuels indicate that it may not last for longer period. It has become necessary to search for an alternative fuel which can be used in the present engines. Coal, having large reserves and being abundantly available in India comes to be the first choice. This paper considers steps necessary for making ability of normal engines to accept coal fuels. The program for development of the coal fueled engine has a initial stage of feasibility validation. Some specific areas were selected for investigations of this stage. The investigations were proceeded in sequence of study of the literature and systems, solid fuels and preparation specially suitable for conditions in India. The fuel feed system was developed for the above engine. The initial assessment of combustion process of the coal fuels in the engine was performed with the help of analytical and experimental method.

In this paper, a thermodynamic simulation model for a four-stroke medium speed, diesel engine is described. The model deals with the fuel injection system, combustion and gas exchange processes. Special emphasis is laid on the latter two processes. In the first phase, a single zone combustion model is discussed. Subsequently, an improved two zone combustion model, which needs lesser computational time is presented. Both these models have satisfactorily predicted the performance of a single cylinder and locomotive engines and a comparison has been made between the results obtained from them. The Leap-Frog scheme has been applied to solve the unsteady equations during the gas exchange process and the computed data from this scheme are found to agree well with the measured data.

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.