Mathematical Modelling and Simulation of Spark Ignition Engine for Predicting Engine Performance Characteristics

Depletion of fossil fuels and environmental pollution concern has led researchers to develop alternate fuels. Alcohols are promising alternative. Ethanol can be blended in gasoline without modification in engine to improve performance characteristics. Since, field testing is expensive and time consuming and moreover it is difficult to maintain favourable condition throughout the experiment. Hence it is easy and convenient to carry out the simulation study in MATLAB environment. This paper put emphasis on the study of engine performance characteristics with ethanol-gasoline blend, a cylinder by cylinder model is designed in MATLAB/Simulink. Whole model is built in the form of blocks which are differential and empirical formulas of engine parameters. These formulas are describing the engine behaviour with respect to crank angle. The pressure inside the cylinder is predicted with another line of information of heat input. Heat input needs data from the mass flow and burn characteristics of combustible fuel which is described by Weibe function. Pressure obtained will be converted to mean effective pressure by subtracting frictional losses. Finally the brake mean effective pressure is calculated. The parameters calculated are brake power, brake specific fuel consumption, fuel consumed, brake thermal efficiency, burn duration and exhaust gas temperature. In this study it is found that ethanol blend with gasoline increases brake power and brake thermal efficiency by lowering the exhaust gas temperature.