Axisymmetric Flow Model with and without Swirl in a Piston-Cylinder Arrangement with Idealized Valve Operation 800284

Axisymmetric cold flow calculations in a piston-cylinder configuration have been performed by means of a stretching and compression computational mesh with and without swirl and for four-stroke engines with turbulent conditions. The valve has been represented either as a centrally located orifice which opens and closes suddenly at BDC or as an annular orifice of varying area which simulates the valve lift profile as a function of time. The results without swirl for the annular valve configuration show two eddies, one behind the innermost valve circle and the other at the cylinder head. These two eddies persist up to TDC of the compression stroke; afterwards the piston drives the flow and the velocity and turbulent kinetic energy profiles are almost sectionally homogenious. The swirl calculations performed with the sudden-valve configuration show the same trends for the flowfield and the radial profile of tangential velocity is almost a straight line which corresponds to a solid-body rotation with a very sharp gradient at the cylinder wall.