Numerical Visualization of Air Short-Circuiting in a Small Two-Stroke SI Engine

A 3-D CFD model for a small two-stroke SI engine has been developed using a commercial code. The model simulates the scavenging process from the exhaust port opening to closing. The fluid in this model is air only. RNG (re-normalized group) was adopted as the turbulence model. The moving piston was achieved using the deforming grid technique. Various methods for numerically visualizing the air short-circuited through the exhaust port were investigated. This paper reports the modified Janté method, particle spray and thermal images. Although the results are only qualitative identification of air short-circuiting, they show that all three methods have the potential to achieve quantitative identification of fresh charge short-circuiting.