Research On Inflow And Rotor Dynamic Characteristics Of High-Speed Submersible Axial-Flow Pump

Combined with the characteristics of submersible pump and axial flow pump,the submersible axial-flow pump can be submerged into the water for electromechanical operation,and has the characteristics of large flow and low head.Submersible axial-flow pumps are vane pumps,one of the development directions of vane pumps are high-speed.Increasing the speed can greatly reduce the volume and weight of the pump,which is convenient for miniaturization and lightweight of the submersible pump.Although many excellent hydraulic models of submersible axial flow pump have been developed,most of the axial flow pump products are in low speed range,the current high-speed of submersible axial-flow pumps are still restricted by many factors.Based on numerical simulation and experiments,the high-speed submersible axial-flow pump is analyzed,and the inflow characteristics,cavitation characteristics,and rotor dynamic characteristics of the pump under high-speed conditions are mainly studied.The main research contents are as follow:(1)UG was used to model the submersible axial-flow pump,ANSYS ICEM was used to structure the mesh,ANSYS CFX was used to simulate the model pump and compared with the results of external characteristic tests to verify the accuracy of the numerical simulation results.The inflow characteristics of the high-speed submersible axial-flow pump under different operating conditions were analyzed.(2)The SST k-? turbulence model is used to perform transient calculations on high-speed submersible axial-flow pumps.The variation of pressure fluctuation and axial force in the main components of the axial-flow pump are studied.The pressure fluctuations at the impeller inlet of the pump are relatively regular.The pressure fluctuations at the impeller outlet and the guide vane outlet are relatively disordered under small flow.The basic frequency at each monitoring point in the submersible axial flow pump is mainly the blade passing frequency.The absolute value of the impeller outlet velocity is relatively large,and the high backflow impact causes the main frequency at the impeller exit monitoring point to be different from the shaft frequency under the condition of small flow.The axial force changes periodically with time under various flow conditions,and the flow change has little effect on the axial force of impeller as a whole.(3)Three cavitation models(Zwart,Kunz and Schnerr-Sauer)were selected and the external characteristics were simulated on large flow.The simulation results obtained bydifferent cavitation models were compared with the external characteristic experiment results,respectively.The prediction accuracy of Schnerr-Sauer model is higher than the other two cavitation models.The cavitation of the blades becomes more serious with the increase of flow and the load increases first and then decreases from the leading edge to the trailing edge of the blade at the same cavitation number.The bubbles generated at the leading edge of the suction of the blade at first and then expended to the trailing edge of the blade along the mainstream flow direction until it occupies the whole suction of the blade with the decreasing of cavitation number.The cavities in the trailing edge of the triangle cloud cavitation at the back of the blade are extremely unstable.As the impeller rotates,the bubbles at the trailing edge gradually shedding and move toward the adjacent blades,resulting in erosion damage and load change of adjacent blades.(4)The fluid-structure coupling calculation is performed on the rotor components of the high-speed submersible axial flow pump.Under different working conditions,the total deformation of the pressure surface and suction surface of the blade gradually increases from the root of the blade to the top of the blade in the radial direction,and reaches the maximum near the top of the blade at the leading edge of the blade inlet,the main deformation of the impeller is the circumferential deformation.The stress on the impeller is gradually reduced from the hub to the rim in the radial direction,and reaches the maximum near the hub of the blade leading edge.Under each cavitation number,the total deformation and stress of blade are smaller than that without cavitation,and the total deformation and equivalent stress of blade decrease with the decrease of cavitation number and increase with the increase of rotating speed.The loading of the pre-stress does not change the mode shapes of the rotor system,but only causes a slight change in the amplitude and natural frequency of each order,and the changes in speed and flow will not have a more obvious impact on the natural frequency of the rotor system.