3D Numerical Investigation of Ignition Timing Effects on the SI Engine Exergy

In this paper, the effect of ignition timing on exergy has been investigated. At the first step, 3D-scheme numerical simulation of a complete engine cycle including combustion process has been taken to account for S81 engine geometry. 3D computational modeling process requires complete simulation of flow field in a fine mesh geometry which includes combustion modeling and dynamic mesh process in region of valve and piston movement surfaces. According to the aforementioned reasons, numerical simulation is assumed to be a highly expensive process which requires high CPU process and CPU time costs. To reduce the cost of the solution, numerical simulation of cold flow (without combustion) is accomplished for motoring cycle on the first step. The results of flow field are taken to account for combustion stage as initial condition. Numerical results are validated using experimental data of FEV institute for current engine with known initial and boundary conditions. The exergies of heat transfer, total work, fuel, and irreversibility of different engine revolutions are studied for different ignition timings, and the results indicate that while the crack angle in which ignition occurs comes closer to the top dead center position, all exergies increase as the consequences.