Modeling and performance improvements of a pressure compensated axial piston pump

Aydoğan, Okan
Analysis of internal dynamics of a pressure compensated axial piston pump has an importance to predict the pump characteristics. In order to accomplish this mission physical model is developed to simulate pump pressure-flow characteristics for a given set of system parameters in Matlab/Simulink environment. The pump is modeled as two main groups, namely, pumping section, and compensation section. Pistons are orderly nested in cylinder block around shaft axis in the pump. In the pumping section model, multi-piston models arranged with a phase shift according to the piston number, 2.pi/N. The model includes leakages from these pistons. Forces on individual pistons are used to model the instantaneous hydraulic torque acting on the swash plate. Individual flow rates generated by movements of the pistons determine the instantaneous delivery flow of the pump. The pressure compensation section consists of a three-way valve, a bias actuator, a control actuator, and a swash plate. Dynamics of these components are also modeled in detail. Hence, the developed model represents a handy computational tool to get pump dynamics for various system parameters. An experimental setup is built to measure discharge pressure and delivery flow of the pump. In order to adjust discharge pressure of the pump, pump outlet port is loaded with an adjustable needle valve which covers the entire working range. Simulation results obtained by using the developed model are compared with experimental results to verify the model. Using this model, various configurations are further examined to obtain their effects on oscillations of pressure and flow. The aim of this work is to obtain performance improvements related with geometric dimensioning of pump internal parts. Three different configurations obtained by setting the angle of kidney-shaped flow passage area on the valve plate are used in the physical model to investigate their influence on the pump dynamics, especially leakages, and oscillations in pressure, flow, and torque. Smoother pressure transitions in piston chamber are obtained by utilizing line to line porting valve plate as opposed to using the original valve plate. The improvement in piston chamber pressure eliminates flow peaks when the piston aligns with the delivery port. As a result of this improvement, the oscillation amplitude of delivery flow is reduced. This improvement also reduces the hydraulic torque on swash plate due to pumping action. Even, lower torques are obtained by utilizing a smaller trap angle than the angles used in both original valve plate and line to line porting valve plate. Hence, the control actuator areas can be reduced for the same working pressure, resulting in lower package volumes for the pump.


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Citation Formats
O. Aydoğan, “Modeling and performance improvements of a pressure compensated axial piston pump,” M.S. - Master of Science, Middle East Technical University, 2018.