ENERGY AND EXERGY BASED ANALYSIS OF SI ENGINES USING METHANE, METHANOL AND OCTANE

Abstract

In this study, the phenomena of air-fuel mixing and combustion of Methane, Methanol and octane has been studied numerically in order to assess the thermodynamic analysis of the system. For this purpose, a thermodynamic-based engine cycle model is developed without considering geometric features of fluid motion. Here a single cylinder four-stroke spark-ignition (SI) engine is considered as a system. Variable specific heat ratio is considered instead of constant specific heat ratio. Empirical correlations are used to predict heat loss from the engine cylinder. Developed fundamental equations and empirical relations have been used in this model with the help of FORTRAN 95. In this study, friction losses are also modeled to estimate the overall energy losses calculation. The effects of changing some design and operating parameters such as compression ratios and rpm on the variation and destruction of exergy have been investigated through the analysis. It was found that the design and operating conditions have considerable effects on the variation of energy, exergy and irreversibilities as well as the efficiency during investigated parts of the SI engine cycle. 1st law and 2nd law efficiencies were found to increase for all the (three) fuels with increasing engine speed and compression ratios. The Present study recommends the necessity of both energy and exergy analysis to identify the source of work potential losses for different fuels used in SI engine.