Observations on the Application of the k-E Model to Internal Combustion Engine Flows

Abstract

Multi-dimensional flow calculations o f a motored, pancake geometry engine were performed with a standard two-equation k-E turbulence model. The results revealed the presence o f secondary recirculating flows near the head-cylinder and piston-cylinder intersections which are very different in nature from those calculated for a laminar flow. A detailed analysis showed that these flow features are driven by the nonisotropic contributions to the normal components of the Reynolds stress tensor as predicted by the k-E model. Comparison calculations o f the one-dimensional compression of homogeneous turbulence using the k-E model, and a Reynolds stress model derived from direcl simulation of turbulence, indicate that the k-E predictions of the Reynolds stresses are satislaclory early in the compression stroke. However, near TDC. they become highly inaccurate. This finding pertains only to the central homogeneous region o f the flow and does not provide direct insight into the accuracy o f the k-E predictions i n the inhomogeneous zones near the cylinder corners. Without a careful experimental study it cannot be conclusively said whether the k-E predicted secondary flows are physically correct.