High-pressure fluctuation and flow ripple may cause unexpected vibration and noise when the piston pump works under severe conditions, and eventually lead to hydraulic transmission failure. The geometry of the valve plate has a great influence on the pressure fluctuation of the piston chamber. In order to optimize the structure of the valve plate, a mathematical model considering the slot geometry and the flow leakage of the lubricating interfaces was established in this paper. The model was used to investigate the pressure of the piston chamber, and then the accuracy of the model was validated by comparing simulation and experimental results. Further simulation results show that the pressure fluctuation in the piston chamber can be effectively suppressed by optimizing the triangular slots parameter of the valve plate, and a good design of the slot geometry could reduce the undershoot and overshoot of the pressure in piston chamber at the starting moment.

Critical inlet pressure (CIP) is a key parameter for ensuring the long life and steady operation of aircraft piston pumps. In the past, this parameter was determined through experimental methods that had drawbacks such as a long duration and narrow application range. To identify an alternate approach that can be substituted for the traditional approach, a numerical model for determining the CIP that considers the dynamic effects of the transient period is proposed in this paper. First, a dynamic model of the pressure-controlled piston pump was established in the form of differential equations based on the lumped parameter method. Next, the fluid model for vapor cavitation and air aeration was derived using homogeneous mixture theory with consideration of the effects of compressibility of both liquid and gaseous phases. Simulation investigation highlighted how the shaft speed, inlet pressure, and transient time influence the fluid properties inside the piston chamber, and a method for determining the CIP both for steady and transient conditions is presented. Finally, tests were conducted on an aircraft piston pump in open-circuit applications for verifying the applicability of the proposed numerical model.

This study investigates the lubrication properties of GCr15 steel textured surfaces under the conditions of low speed, heavy load, and boundary lubrication, with varying concentrations of Al₂O₃ particles. Through pin-on-disk tests in 46# hydraulic fluid, it was found that the texture density had little effect on the friction in the absence of abrasive particles and that the friction increases with an increasing texture density in the presence of abrasive particles. Abrasive particle concentration significantly increases the friction on smooth surfaces, while textured surfaces can retain abrasive particles and lubricants, mitigating the increase in friction. The impact of abrasive particles can wear down the texture edges and weaken its friction-reducing effect. This study reveals the interaction between abrasive particle concentration and texture density, providing a theoretical basis for designing textured surfaces suitable for abrasive-containing lubrication environments.