Optimization of Pressure Relief Grooves for Multi-Quadrant Hydraulic Machines in Different System Architectures

Abstract

In hydraulic axial piston machines, each chamber switches between the high-pressure and the low-pressure port with every revolution. How this process, the commutation, is done, is an essential part of pump design. The commutation typically targets a smooth pressure transition to minimize compressible flow pulsations. However, an ideal pressure match is not possible over the whole operating range of the machine. Thus, pressure relief grooves are considered a “necessary evil” in the state of the art, which can reduce flow pulsations over a wide operating range on the expense of slightly increased losses. Depending on the drive cycle and especially the number of quadrants a hydraulic machine is used in, the optimal pressure relief groove design differs. The increased losses and pulsations for enabling 4-quadrant operation of hydraulic machines are shown. Pump-controlled systems lead to hydraulic machines running in different drive cycles than in conventional valve-controlled systems, affecting ideal groove design. This paper focuses on how to optimize pressure relief grooves and thus presents the methodology incl. the simulation model, formulation of the objective function, and choice of optimization algorithm. Optimizations are carried out for 1-, 2- and 4-quadrant operation. Pareto fronts for a trade-off between flow pulsations and losses are presented, for both a valve-controlled system and a pump-controlled system carrying out the same task in an excavator boom application.