Numerical Optimisation of the Scavenging Process of a Port-Controlled Engine

The project "Numerical Optimisation of the Scavenging Process of a Port-Controlled Engine" (Rechnerische Spülungsoptimierung eines 2-Takt Motors mit schlitzgesteuerten Überström- und Auslasskanälen und bewegtem Kolben)) is carried out at the University of Freiburg in collaboration with an industrial partner. It is directed by Prof. Dr. D. Kröner and Dr. A. Klimmek. The work is supported by the BMBF. The implementation of the new clean air act regulates the usage of two-stroke engines, taking into consideration the air pollution, and also specifies a significant reductionof the unburnt hydrocarbons. These emission are mostly caused by scavenging process losses (by mixing of the fresh and burnt gas). The goal of this project conducted by our group and the industrial partner is the improvement of engine geometry that will lead to the stabilisation of the scavenging flow and the minimisation of the deficit in process. (Team: P. Bachmann, A. Egelja, B. Schupp, D. Trescher)

Two different Models

On the pictures are shown two different models of a Port-Controled-Two-Stroke-Engines. The problem of the two-stroke-engine is the scavenging of the bournt gas out of cylinder by the incoming combustion mixture such that the unburnt gas itself does not flow out of the outlet.

The grids shown below are the discretisations of the geometries we used. Each of them has one outlet and one or more inlets.

Numerical simulation To simulate the exchange between the new ("unburnt") incoming gas and the old ("burnt") gas we solve nonstationary compressible Navier-Stokes equations.