Numerical Analysis of Gas Exchange and Combustion Process in a Small Two-Stroke Gasoline Engine

This paper analyses the scavenge process of a conventional two-stroke engine in order to find ways to significantly reduce the scavenge losses by applying a combination of 1D and 3D simulation procedures. A special evaluation method was developed which allows a clear distinction between the main hydrocarbon loss mechanisms. Furthermore, the paper presents an approach to simulate the highly turbulent combustion at a speed of 9000 rpm. The results of the numerical investigations are compared with experimental results.

The engine chosen for this purpose was a 64 cm³ four-port production two-stroke engine. The CFD calculations were performed using the finite volume CFD code STAR-CD. The mesh generation process was automated using pro*am. Combustion was modelled with the one-equation Weller flamelet model.

The results of the present study show that the combination of 1D and 3D simulation procedures is a powerful tool for further investigations (e.g. stratified charge, GDI).