Theoretical Study of the Effects of Combustion Duration on Engine Performance

Abstract

In this study, a thermodynamic cycle simulation of a four-stroke spark-ignition engine was conducted to predict the engine performance. The single-zone model was built based on the Wiebe function for the mass fraction burned and Woschni’s model for the convective heat loss. The first law of thermodynamics was applied to describe the engine behavior versus the crank angle. These formulas determine in-cylinder pressure, temperature, mean effective pressure, and effective power. This study was performed to evaluate the effects of the combustion duration on the engine performance characteristics. Simulations were carried out on a 98 cm3 four-stroke SI engine set up at 3600 rpm corresponding to the maximum torque (5.7 Nm). In this study, it was found that under the same operating conditions, accelerating the combustion does not always increase the power delivered by the engine. The best engine performance in terms of compromise between heat losses and power delivered was obtained for the combustion duration corresponding to 60° CA.&nbsp;<br>