FLOW RIPPLE REDUCTION OF AXIAL PISTON PUMP WITH PRE-COMPRESSION VOLUME AND EMBEDDED SEQUENCE VALVE

In the aircraft hydraulic system, constant pressure piston pump, as the main power supply component, is widely utilized due to its high power efficiency. The flow ripple caused by the axial piston pump may induce pipe vibration and lower hydraulic components' reliability, which becomes an especially concerned issue. Compared with the traditional relief groove, the pre-compression volume (PCV) used in piston pumps could precharge the piston chamber's pressure to reduce the backflow more evidently. However, the pressure in PCV is affected by system pressure, pump speed and swashplate angle, which refer to the discharge pressure, the time duration of this transient and the volume of piston chamber, respectively. In the piston pump's constant pressure zone, the discharge pressure is higher at zero swashplate angle compared with that at full swashplate angle, while PCV needs lower pressure to charge the piston chamber because its volume is smaller. For the purpose of flow ripple reduction for different swashplate angles, this study proposes to employ an embedded sequence valve (ESV), with open neutral position, placed between PCV and discharge port. The opening of ESV becomes smaller when the discharge pressure goes higher. This design could change the pressure in PCV automatically and help reduce the piston chamber's backflow. Based on the modelling of PCV type pump, the mathematical model of pump's flow ripple including the pump with PCV type pump with ESV is established. The key parameters of the valve are investigated and designed. The computational fluid dynamic (CFD) model of the proposed pump is established, and the numerical validation of different working statuses is carried out. The result indicates that significant flow ripple reduction and pressure pulsation reduction at different pump displacements are achieved.