A Model for the Instantaneous Heat Transfer and Turbulence in a Spark Ignition Engine

The heat transfer and turbulence are modeled for a spark-ignition engine. The heat transfer is described in terms of unsteady boundary layers for both the burned and unburned gas regions. These boundary layers are influenced by both the free stream turbulence level and the rate of flame propagation. Turbulence levels are characterized by a K-ε model which includes the effects of compressibility and anisotropic behavior of the flow field. The flame propagation process is modeled using current entrainment model philosophy.

The results of the modeling are illustrated for an engine having a simple pancake geometry. The major accomplishments are the development of an unsteady, compressible turbulence model and the development of an instantaneous heat transfer model. The influence of the turbulent field on the heat transfer rate is given via the turbulent Reynolds number and the integral length scale. The averaged heat transfer rate is compared with the correlations of Annand and Woschni and the shortcomings of these simpler correlations are discussed.