Optimization of Gerotor Pumps with Asymmetric Profiles through an Evolutionary Strategy Algorithm

Abstract

Gerotor pumps are widely used for fuel and lubricating oil distribution, since they provide an economic and compact solution for low-pressure fluid systems. Made of two internally coupled gears, their behavioral and operative performances are strictly tied to their geometrical designs. Traditionally, the external gear features circular lobes that give origin to a cycloidal profile for the internal rotor. In this paper, the use of profiles based on asymmetric lobes made of elliptic arcs is further explored and expanded. At first, a complete mathematical framework describing the pump geometry and its dynamic behavior is provided, while algorithms used to compute a selected number of performance indexes are presented and when possible, verified. Hence, a single-objective optimization procedure is applied to the traditional cycloidal profile, in order to minimize each of the following quantities: the flow rate irregularity, the expected wear rate, and the estimated rotor mass. Finally, a multi-objective optimization process based on evolutionary strategy is employed, to obtain several asymmetric profiles minimizing the combination of two or more performance indexes. The results are hence compared, and the merits associated with the use of asymmetric lobes are presented.