Investigation of the leakage in the flow distribution pair of radial piston hydraulic motors through CFD analysis and experiments

Abstract

The internal leakage of a radial piston motor (RPM) is an unavoidable structural characteristic, and the amount of internal leakage has a critical effect on the volumetric efficiency of the motor. Using the distribution plate as the force body, an equation for the balance between the preload spring force and the hydrodynamic force is analytically derived, the variation range of the clearance of the flow distribution pair (FDP) is determined, and a model for the internal leakage flow of the FDP is developed. Based on computational fluid dynamics (CFD) simulations, the effects of the oil film thickness, inlet pressure, motor speed, and oil temperature on the leakage volume are investigated. An efficiency test system for RPMs is built and tests are performed on motor prototypes. The experimental results show that the error between experimental and simulation results decreases gradually with increasing motor speed. When the motor runs at the rated speed, the error is stable within 5%. The experimental results verify the correctness of both the theoretical and CFD models. The CFD analysis method can be used as a technical means to optimize the motor volumetric efficiency and the preload spring design.