An analytical investigation of oil film thickness for the apex seal in a small Wankel rotary engine

- Quasi-static equation of apex seal with hydrodynamic lubrication is proposed.
- Lateral movement of apex seal modifies the pressure distribution greatly.
- The gas pressure peak makes the oil film thicknesses descend to local minimum.
- High operation speed increases the minimum and average oil film thicknesses.

The purpose of this paper is to research the oil film thickness between apex seal and epitrochoidal housing in a small Wankel rotary engine. Firstly, a quasi-static equilibrium equation of apex seal is derived with considering interacting forces. It is supposed that oil pressure is the only force supporting the apex seal against other loads. Then, the oil film thickness is evaluated by solving the equilibrium equation and Reynolds equation within a cycle. In addition, the operation speed's influence on the oil film thicknesses is studied. Results indicate that the oil film thickness is a comprehensive parameter affected by many factors, and these factors exert varying degree of influence on the oil film thickness at different positions within a cycle.