Analysis of Frictional Power Losses Associated With the Side and Apex Seals of a Wankel Rotary Engine

A mathematical model has been implemented in a computer code to predict seal dynamics in a rotary engine. Using cell pressure and engine speed as inputs, along with geometric housing equations, one is able to model apex seal lift off, shifting and frictional power associated with the apex and side seals. Results show that at moderate to high engine speeds the apex seal's fore and aft movement is dominated by a transverse acceleration because the velocity of the seal must change as it follows the trochoidal housing. The seal lift off from the housing is dominated by a radial acceleration which also depends on the engine speed. The resultant frictional power loss associated with the apex seals is an exponential function of the engine speed, whereas the frictional power loss associated with the side seals is a linear function of engine speed. For a medium power output condition (412.5 kPa at 5000 rpm), the magnitude of the apex seal frictional power surpasses the side seal frictional power at slightly above 5000 rpm.