Numerical Simulation And Experimental Study On Axial Piston Pump And Energy Recovery Machine For Seawater Desalination

In recent years,in order to solve the problem of water shortage in the areas,such as islands,vessels and drilling platforms,the demand for small and medium-sized desalination devices has increased rapidly.The axial piston pump and energy recovery machine is an important component in the seawater desalination system.The pump end increases the seawater pressure to meet the requirement of pressure for the reverse osmosis membrane seawater desalination,and the motor end recovers the energy in the high pressure waste-water.However,the flow,pressure fluctuation and cavitation generated during the operation of the axial piston pump and energy recovery machine can easily cause serious vibration and noise problems,affecting the stable operation of the desalination system.In this paper,a series of numerical simulation and experimental measurement work are carried out for the flow and pressure characteristics inside the seawater desalination axial piston pump and energy recovery machine,which provides a theoretical basis for the optimization of vibration and noise reduction of the axial piston pump and energy recovery machine.The main research contents and results of this paper are as follows:(1)Based on the internal structure of the seawater desalination axial piston pump and energy recovery machine,model of the pump end and the motor end are independently built.The flow and pressure solution of piston chamber and the outlet are solved for the pump end.At the same time,the flow and pressure of piston chamber and the inlet are solved for the motor end.The dynamic flow rate of the pump outlet at different rotation speeds is coMPared and analyzed,and the relationship between the outlet flow fluctuation and the rotational speed under one rotation period is obtained.According to the analysis of the outlet flow fluctuation rate under different parameters of damping groove,the geometric parameters of the damping groove are optimized.(2)Considering the dynamic elastic modulus of the seawater,the cavitation flow of the pump end and the motor end is numerically simulated based on the Schnerr-Sauer model,and the chamber contours is analyzed.During the changing process,it was found that the cavitation in the axial piston pump and energy recovery machine mainly appeared in thedamping groove of the pump end and the piston chamber.The change of pressure in the piston chamber chamber was analyzed in the cavitation state,and the starting time of cavitation in the piston chamber chamber was found.According to the relationship between the dead zone of the port plate and the initial position of the piston chamber chamber,the pressure fluctuation rate in the piston chamber chamber is optimized by changing the mismatch angle of the pump end.(3)In order to study the pressure fluctuation characteristics of axial piston pump and energy recovery machine in different rotational speed and outlet pressure,the pressure fluctuation monitors were arranged at the inlet and outlet of pump end in the working condition of 800 r/min,1000 r/min,1200 r/min,1450 r/min,1600 r/min,and outlet pressures of 4.5 MPa,5.5 MPa,6.5 MPa,and 7.5 MPa.The time-domain results obtained by the experiment showed that the fundamental wave of the pressure fluctuation curve at the pump end presents the shape of a triangular wave.The amplitude of the fundamental wave is attenuated with the increase of the rotational speed,and the amplitude of the harmonic gradually increases.The inlet pressure fluctuation curve presents a triangular wave shape at a low rotational speed,and the waveform changes irregularly as the rotational speed increases.The results of frequency domain analysis show that the shaft frequency is the main influence frequency of the pump end outlet at low speed,and the piston frequency becomes the main influencing factor with the higher rotation speed,and harmonics appear at 3Z multiples of the shaft frequency.As the outlet pressure of the pump increases continuously,the amplitude of the outlet pressure fluctuation increases continuously at the axial frequency and the piston frequency,the pressure fluctuation rate is basically constant,and the frequency distribution is more concentrated;the inlet pressure The fluctuation amplitude decreases at the axial frequency and rises at the piston frequency.