Thermodynamic modeling of spark-ignition engine: Effect of temperature dependent specific heats

This paper presents thermodynamics analysis of spark-ignition (SI) engine. A theoretical model of air-standard Otto cycle having temperature dependent specific heats has been implemented. It was compared to that which uses constant temperature specific heats. Wide range of engine parameters was studied. In most cases there were significant variations between the results obtained by using temperature dependent specific heats with those obtained at constant specific heats especially at high engine speeds. Therefore, it is more realistic to use temperature dependent specific heat. This should be considered in cycle analysis; especially that temperature variation in the actual cycles is quite large.