COUETTE-FLOW HEAT-LOSS MODEL FOR THE ROTARY COMBUSTION ENGINE

A novel model for predicting heat transfer in a rotary engine was form ulated and implemented in a zero-dimensional engine performance model. Results were compared with a commonly used intermittent combustion en gine heat transfer model and with results from a three-dimensional sim ulation 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 fla t plate type heat transfer correlations. These correlations, though us eful, do not model the flow physics in the rotary engine faithfully. R ather than flow over a flat plate, flow in the rotary engine was appro ximated as turbulent Couette flow. The Couette model was altered to ac count for centre-line velocities higher than half the rotor speed. The re me two advantages to using the Couette flow model. Firstly, as note d, the underlying physics of the Couette flow model is closer to condi tions in the rotary engine. Secondly, with the Couette flow model it i s possible to differentiate between the rotor and housing heat transfe r coefficients.