Geometrical analysis of a quadrilateral rotary piston engine

•We model the geometry of a quadrilateral machine.•The model includes a stator profile and a rotor flank profile.•The rotor flank includes flat and curved profiles.•The model includes volume variation, compression ratio and displacement volume.•The model shows the importance of eccentricity parameter on performance.

This paper presents geometrical analysis of a novel rotary device suitable for operation as an engine, an expander and a pump. The device comprises a stator having an elongated oval-shaped chamber encompassing a quadrilateral deformable rotor. The analysis includes derivation of the closed-form equations describing the inner stator profiles, compatible rotor-segment profiles, volume variation, compression ratio, and displacement volume. The study shows the pivotal importance of the chamber eccentricity ratio and inner offset parameters on the performance of the device. Verification of the analytical results was made by comparing them with those obtained by numerical integration at selected points.