Optimization of SI Engine Cycle with Variable Composition and Specific Heat

Abstract

The combustion modelling and simulation of four-stroke gasoline engine has been discussed in the chapter. The combustion parameters viz., pressure, temperature, and energy are calculated in a step by step analysis by assuming a homogenous single zone within the spark ignition engine cylinder and applying the first law of thermodynamics during the closed part of the cycle. The first law of thermodynamics is written in a suitable form to facilitate the computational procedure involved in the iterative technique to determine the temperature at the end of the step. The variation in gas composition during combustion and expansion is considered. The variation of specific heats with temperature and composition is also considered. Only six gases are considered, i.e., oxygen, nitrogen, carbon dioxide, carbon monoxide, hydrogen, and water vapour, and during the heat release, the composition is varied as required for perfect combustion. The computer code also calculates indicated mean effective pressure, power of the engine, and thermal efficiency. The results show that this program can be quite useful for the design of internal combustion engine parts by considering the peak values of various combustion parameters obtained during the analysis.