Simulation of Unadiabatic Intake Flow of 4 Cycle Engine

Abstract

In this paper an equation for an unadiabatic mass flow rate through the nozzle iS derived by application of polytropic analysis. The author performed experiment to estimate validity of the flow equation, and found difference in flow coefficient between adiabatic and unadiabatic flows. This difference can be analized by laminar boundary layer theory which considers temperature distribution. Simulation of intake process of a 4 cycle engine was done by solving this flow equation and energy equation in a cylinder by Runge-Kutta-Gill method. Heat transfer at poppet valve affects flow rate only when valve lift is small, so it can change the total intake flow rate by a few percent. But, heat transfer in a cylinder can change the total intake flow rate by 10 or 20%, because it affects the cylinder pressure which governs the pressure difference between before and behind poppet valve.