Capped piston: A promising design to reduce compressibility effects, pressure ripple and cavitation for high-speed and high-pressure axial piston pumps

Abstract

Raising rotational speed and operating pressure is an effective way to increase the power density of axial piston pumps. However, the axial piston pump with standard hollow pistons suffers from problems of volumetric losses, pressure ripple, and cavitation at high rotational speed and operating pressure. To reduce these fluid-related problems, the capped piston design is a promising alternative to the standard piston design by minimizing the dead volume. The capped pistons have been applied in commercial axial piston pumps but it remains unclear how the flow characteristics of axial piston pumps benefit from them. Therefore, this paper aims to clarify the mechanism of capped pistons in improving the flow characteristics of axial piston pumps. A computational fluid dynamics model is developed to compare the pump’s flow characteristics between standard and capped pistons. The simulation results show that compared with the standard hollow pistons, the capped pistons can significantly reduce the compressibility effects, pressure ripple, and cavitation over a wide range of operating conditions.