Leakage and Groove Pressure of an Axial Piston Pump Slipper with Multiple Lands

This article presents a new analytical model, based on Reynolds equation of lubrication, to evaluate the leakage and pressure distribution for an axial piston pump slipper taking into account the effect of nonvented grooves. The equations consider slipper spin and tilt and are extended to be used for a generic slipper with any number of grooves. A test rig has been designed and used to check experimentally the applicability of the theoretical equations and comparisons between theoretical and experimental results show a good agreement. The new theory can predict slipper leakage and pressure inside the groove with a high level of accuracy, especially at the very low slipper tilts that exist in practice. Experimentally, it is demonstrated that although a groove maintains a constant pressure along its path, under abnormal conditions the pressure differential can exist inside the groove. The effect of tangential velocity on groove pressure and slipper leakage is then studied experimentally, showing that as the rotational speed increases, there is a small decrease in leakage and a small increase in the average pressure inside the groove.