Dynamic Characteristics Analysis Of Liquid Ring Pump Rotor Based On Fluid-structure Interaction

Liquid ring pump is a kind of fluid machinery used to pump gas.It is often used to pump and compress flammable,explosive,dust-containing and toxic gas.Because of its large flow rate,isothermal compression,no contact between rotor and pump body,it is widely used in petroleum,coal mine,chemical industry and nuclear power.Aiming at the problems of stress concentration,crack failure and poor stability of rotor operation caused by unsteady stress of rotor blade in liquid ring pump,this study intends to analyze the response characteristics of rotor structure caused by unsteady gas-liquid two-phase flow in liquid ring pump.Based on the combination of numerical simulation and experimental test,the fluid-solid coupling stress and strain analysis of rotor parts of liquid ring pump was carried out.The distribution of stress and deformation of rotor parts under different rotation angles and flow rates was analyzed.The distribution characteristics of maximum deformation of different blades along the circumferential direction were analyzed.The variation law of stress and deformation on impeller blades was analyzed,and the strength of rotor parts was checked.At the same time,the dry modal analysis without prestress,the dry modal analysis with prestress and the wet modal analysis of the rotor parts of the liquid ring pump were carried out respectively.On this basis,the critical speeds of the rotor parts of the liquid ring pump were analyzed,and the possibility of resonance of the pump during operation was predicted.It is expected to provide a theoretical reference for the structural optimization design of the liquid ring pump.The main research contents and conclusions of this paper are as follows:(1)The complex gas-liquid two-phase flow and performance in the liquid ring pump were analyzed by numerical simulation and experimental test.The results show that the numerical simulation of the liquid ring pump is basically consistent with the external characteristic curve of the experimental results,and the gas-liquid distribution law inside the liquid ring pump and the shape of the gas-liquid interface are also consistent with the experiment.In the case of little deviation from the working condition,the distribution characteristics of the phase field in the pump are basically the same.The pressure in the radial direction of the pump gradually increases from the root of the blade to the top,and the pressure along the circumferential direction gradually increases from the suction zone to the compression zone and the exhaust zone.The pressure in the pump is asymmetrically distributed along the circumferential direction.The load distribution of each blade is different,and the blade is subjected to alternating load during rotation.(2)The influence of rotation angle on the stress and deformation of the rotor components of the liquid ring pump is analyzed.The results show that the maximum equivalent stress and the maximum deformation of the rotor components fluctuate periodically with the rotation of the impeller due to the non-uniformity of the impeller outlet flow and the circumferential asymmetry of the impeller flow field.In a rotation period of blade angle,with the increase of rotation angle,the maximum equivalent stress decreases first and then increases.When the distance between the blade tip and the inner wall of the shell is the smallest,the maximum equivalent stress is the maximum.The change trend of the maximum deformation of the rotor component with the rotation angle is completely consistent with the change trend of the maximum equivalent stress.(3)The distribution characteristics of the maximum deformation of different blades along the circumferential direction were analyzed.The results show that the maximum stress distribution of the 18 blades along the circumferential direction of the impeller is different,and the maximum deformation of the 18 blades decreases first and then increases as the impeller rotation angle changes from 0°to 16°.When the rotation angles of the impeller with large deformation are 0°and 4°,the maximum deformation of the blade gradually decreases from the beginning of the suction zone(blade 18)to the beginning of the compression zone(blade 10),and the maximum deformation of the blade gradually increases from the beginning of the compression zone(blade 10)to the end of the exhaust zone(blade 18).(4)The variation law of stress and deformation on the impeller blade was analyzed.The results show that the deformation distribution on the blade increases approximately linearly from the hub to the tip along the radial direction.The stress increases sharply first and then decreases slowly along the radial direction,and reaches the maximum at the position of 0.1 r The stress and deformation on the blade remain basically constant along the axial direction.(5)The dry modal analysis of the rotor parts of the liquid ring pump without prestress,the dry modal analysis with prestress and the wet modal analysis were carried out respectively.The results show that the vibration modes in these three cases are the same.The first-order mode is the torsional deformation of the impeller around the rotating shaft.The second and third-order modes are mainly swing deformation.The fourth,fifth and sixth modes are the swing of the impeller blade around the rotating shaft.After considering the fluid-solid coupling prestress,the first six natural frequencies of the rotor parts increase to varying degrees,and the increase is not obvious,while the first six order amplitudes also change to varying degrees,but the change is not large.The working condition and the rotor angle position have little effect on the natural frequency and amplitude of the rotor components.(6)The test system was built to measure the natural frequency of the rotor parts of the liquid ring pump.The results show that the natural frequency obtained by the modal analysis of the rotor parts of the liquid ring pump is basically consistent with the experimental result.The maximum prediction error of the first three modal frequencies is 5.02%.(7)On the basis of modal analysis,the critical speed analysis of the rotor components of the liquid ring pump under the action of no prestress,the critical speed analysis under prestress and the critical speed analysis in the water environment were carried out respectively.The results show that the rotor components of 2BEA-202liquid ring pump will not resonate under the action of prestress,without prestress and in the water environment,and the structure meets the design requirements of the critical speed.