Couette Flow Heat Loss Model for the Rotary Combustion Engine

Abstract

A novel model for predicting heat transfer in a rotary engine was formulated and implemented in a zero-dimensional engine performance model. Results were compared with a commonly used intermittent combustion engine heat transfer model and with results from a three-dimensional simulation of flow within a rotary engine. When squish effects associated with fluid motion within the chamber were included, the Couette flow model reproduced peak heat transfer rates and timing for the peak heat transfer rate was better than that of the commonly used heat transfer model.

Previously, rotary engine performance models have employed flat plate type heat transfer correlations. These correlations, though useful, do not model the flow physics in the rotary engine faithfully. Rather than flow over a flat plate, flow in the rotary engine was approximated as turbulent Couette flow. The Couette model was altered to account for centre-line velocities higher than half the rotor speed. There are two advantages to using the Couette flow model. Firstly, as noted, the underlying physics of the Couette flow model is closer to conditions in the rotary engine. Secondly, with the Couette flow model it is possible to differentiate between the rotor and housing heat transfer coefficients.