Analysis and design of the optimal radius gap of the piston pair

The axial piston pump plays a crucial role as a power component in the hydraulic system. As one of the important friction pairs, the piston pair has a significant influence on the mechanical and volumetric efficiency of the axial piston pump, where the gap of the piston pair has a considerable effect on the lubrication and overall efficiency of the piston. However, there are a few studies on the gap of the piston pair and there is a lack of relevant theoretical support for the design of the gap of the piston pair, especially when the piston has spin motion. To tackle this problem, we propose a CORG (critical and optimal radius gap) design method for the gap of the piston pair based on the critical radius gap and the optimal radius gap. Specifically, we first provide a theoretical proof for the existence of the critical radius gap. Then, considering that the piston has spin motion, we analyze the power loss of the piston pair and define the leakage power loss and viscous dissipation power loss according to the physical meaning. Meanwhile, the minimum value of the total power loss of a single piston pair is taken as the optimization metric of the piston pair, and we further propose the optimal radius gap. Then, by combining the critical radius gap and the optimal radius gap of the piston pair, we propose the CORG design method for the radius gap of the piston pair and obtain a dimensionless CORG constant that should be satisfied in the design of the radius gap of the piston pair. In framework of the CORG design method, it can not only ensure that the total power loss of a single piston pair is minimized but also prevent the volumetric efficiency of the piston pair from being too low. Finally, the simulation model of the piston pair is built by AMESim software, and the correctness of the theoretical calculation results are further verified by comparing the simulation results with the theoretical calculation results. The CORG design method can further provide theoretical references for the design of the piston pair.