Numerical and experimental study of hydrostatic displacement machine

This paper presents a simulation tool to determine the structural deflections and corresponding leakage flow in a hydrostatic displacement motor. The simulation tool is applied to a new motor principle that is categorized as an extreme low-speed high-torque motor with dimensions that calls for attention to the volumetric efficiency. To counteract structural deflections the motor is equipped with compensation pressure volumes that may be used to limit the leakage flow across the end faces of the circular rotor. This leakage flow is investigated by solving Reynolds equation for the pressure distribution across both end faces. The fluid pressure is combined with structural calculations in a fluid structural interaction simulation, which evaluates the influence of structural deflections on the gaps and the leakage flow.
The numerical work is validated by prototype tests. Both deflections and leakage flows are measured and compared with those from the simulations with good correlation. The deflections, and hence leakage flow, are reduced by the use of compensation pressure volumes, which is validated both numerically and experimentally.