The Improved Volumetric-Efficiency of an Axial-Piston Pump Utilizing a Trapped-Volume Design

In this research, the volumetric efficiency of the axial-piston pump is examined as it relates to the compressibility losses of the fluid. In particular, two valve-plate geometries are compared to show that alterations in the valve-plate design can cause differences in the operating efficiency of the pump. In this paper, a standard valve-plate design which utilizes slots is compared to a trapped-volume design which eliminates the slots altogether. In the analytical result of this paper, it may be shown that the standard valve-plate design introduces a volumetric loss which may be accounted for by the uncontrolled expansion and compression of the fluid that occurs through the slots themselves. By eliminating these slots, and utilizing a trapped volume design, it may be shown that improvements in the operating efficiency can be achieved. Though this paper does not claim to provide the ideal valve-plate design for all pump applications, it does provide the theoretical reason for utilizing trapped volumes and lends general insight into the overall problem of valve-plate design.