Modelling Near Wall Temperature Gradients in “Motored” Spark Ignition Engines

A new type of model has been developed to predict near wall temperature gradients and local instantaneous heat fluxes in a “motored” engine. The unburnt charge in an existing “phenomenological” model is divided into a number of discrete masses which are assumed to be “stacked” adjacent to the cylinder surfaces. A sub-model based on the one-dimensional Enthalpy Equation is applied to the system of discrete masses in order to predict the near wall temperature distribution. Predicted temperature profiles are compared with those measured by other researchers and show good agreement under both low and high swirl conditions. Local instantaneous heat fluxes are calculated from the near wall temperature gradients, and these also show good agreement with measured results.

Near wall velocity and turbulence data have been used in modelling turbulent eddy transport processes rather than using conventional boundary layer theories. This technique has proven to be very successful in both high and low swirl situations, leading to the conclusion that conventional boundary layer theory may not be applicable to engine type flows.