Comparison of Hypotrochoidal and Epitrochoidal Gerotors

Abstract

The planar rotary mechanisms, by virtue of its volume changing ability can be used as a pump, engine, or compressor. Most of the types of rotary mechanisms used today, from the Wankel rotary engine to the gerotor pump, are based on epitrochoidal generation and its conjugate shape. This paper presents a very general mathematical relationship for a generating arc traveling on a hypotrochoidal path and also compares the flow rate, pocket displacement, and compression ratios of the hypotrochoidal and epitrochoidal generated profiles.