Numerical optimisation of scavenging in two-stroke engines with transfer ducts, an exhaust port and a moving piston

L. Klassen, A. Klimek, D. Kröner and D. Trescher

Mathematics - Key Technology for the Future, Joint Projects between Universities and Industry, W. Jäger, H.-J. Krebs Eds., Springer, pp. 22-32, 2003.

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For the benefit of the environment, the HC-emission of the two-stroke engines has to be reduced. This can be done by reducing the losses of scavenging by improving the geometry of the transfer ducts and the exhaust port. Numerical simulations of the flow thought the two-stroke engine should be performed for different geometries in order to reveal the geometry with an optimal scavenge process. The simulations can help to accelerate the development of new two-stroke engines. The underlying mathematical model consists of the compressible Navier-Stokes equations in the cylinder with a moving piston. For the discretization we use a stabilized finite volume scheme on a hexahedral mesh. Up to now we have developed a numerical code for computing the flow in the cylinder and the most important integral quantities such as trapping efficiency and the percentage of exhaust gas at the exhaust port. Now we are able to analyse quantitatively the scavenge process and to estimate the quality of different drafts for the geometrical design.