A Numerical Study on the Effects of Fluid Motion at Inlet-Valve Closure on Subsequent Fluid Motion in a Motored Engine

A multidimensional computer model was used to assess the effects of the initial swirl level, swirl velocity distribution and turbulence kinetic energy level at inlet-valve closure on the turbulence level and mean motion during the compression stroke of a motored reciprocating engine. Two piston geometries were considered in the study. The first was a flat-crown piston and the second was a piston with a reentrant bowl. For the test cases examined, the salient results obtained were the following: (a) both mean motion and turbulence level near top dead center (TDC) are sensitive to variation of the initial level of swirl, (b) both the turbulence and the mean motion are influenced by the shape of the initial swirl-velocity profile independently of the level of swirl, and (c) the value of the turbulence kinetic energy at inlet-valve closure has no effect on the turbulence near TDC in the presence of swirl. In the absence of swirl, however, the initial levels of turbulence did have a small influence on turbulence near TDC.