The hydrostatic/hydrodynamic behaviour of an axial piston pump slipper with multiple lands

This study considers an analytical approach towards the understanding of the hydrostatic leakage and lift characteristic of a flat slipper of the type used for piston/slipper units within an axial piston pump or motor. In particular it considers a slipper design incorporating a groove on the slipper face and also includes the effect of motion around its associated swash plate. A new set of equations are developed and in generic form for a slipper with any number of grooves. Experimental comparisons are then undertaken and extended to include the effect of relative motion around the swash plate and slipper tilt. A CFD study of the slipper is also presented. Comparisons between analytical, experimental and CFD results show a very good agreement, validating the equations presented and extending the conclusions when tilt and tangential speed are considered.