Study On Flow Field Characteristics And Optimization Design Of Four Assignment Windows Axial Piston Pump

Axial piston pump is the power component of hydraulic system,it widely used in the field of construction machinery because of its advantages of high working pressure and easy variable control.In hydraulic control system,compared with valve control system,pump control system can eliminate throttling loss and save energy significantly.When the asymmetric hydraulic cylinder moves,the flow rates of the two chambers are not equal,so it is impossible to realize the direct control of the asymmetric cylinder by a single axial piston pump.It is necessary to use two hydraulic pumps or other components to exchange excess flow,which increases the complexity of the hydraulic circuit.Four assignment windows axial piston pump is a modification of the flow distribution structure of the common axial piston pump,which can realize a single axial piston pump directly control the asymmetric cylinder movement.The flow distribution structure has a direct impact on the flow pulsation,pressure pulsation and cavitation of the piston pump,which in turn affects the operating characteristics of the piston pump and the hydraulic system.In this paper,the four assignment windows axial piston pump is taken as the research object,the flow field characteristics of the pump are studied by using simulation technology,and study methods to improve the working characteristics of the axial piston pump,providing a theoretical basis for the structure optimization of the axial piston pump.This paper adopts the computational fluid dynamics method to study the flow field of the axial piston pump,firstly,it introduces the working principle of four assignment windows axial piston pump,and establishes the mathematical model of axial piston pump kinematics and pressure flow model to provide the theoretical basis for simulation analysis.Then,the flow field geometry model of axial piston pump was established by Solid Works software.Finally,the flow field simulation model was established in Pumplinx software.The model considered four oil film models of friction pairs.The motion and deformation of the mesh model were realized by using dynamic grid technology and writing motion equations,and adds a cavitation model to simulate the cavitation effect,which establishes a more complete transient simulation model of the axial piston pump flow field.The distribution characteristics of the internal flow field parameters of the axial piston pump,including pressure field,velocity field,flow rate and cavitation characteristics,were obtained by numerical simulation.The causes of flow pulsation,pressure overshoot and cavitation of piston pump were analyzed in combination with flow field visualization technology.The influence law of different outlets pressure,swash plate angle and speed on the flow field characteristics of piston pump was analyzed.The structure of the damping groove of the valve plate has a large impact on the operating characteristics of the piston pump,in order to improve the operating characteristics of the piston pump,the damping groove structure is optimized.A prediction model based on radial basis function neural network and NSGA-II genetic algorithm was proposed.The design variables were depth angle,width angle and circumferential wrap angle of the damping groove,and the flow pulsation rate and pressure pulsation rate of the piston pump were the optimization objectives.The prediction model between the design variables and the optimization target is established by RBF neural network,and the NSGA-II algorithm was used to find the optimization of the prediction model.The simulation results show that the flow pulsation rates of the two outlets were reduced by 10.62% and 13.20%,and the pressure pulsation rates were reduced by 22.38% and 24.33%,which verifies the effectiveness of the optimization method.The research results provide a certain reference for the optimization design of the axial piston pump.