Research On The Hydraulic Excitation Characteristics Of Multiphase Pump Based On Gas-liquid Two-phase Condition

Multiphase pump is one of the main equipment for the oil and gas mixed transmission in the petroleum industry.The transportation medium is mixture of gas-liquid two-phase and various impurities.The gas volume fraction often exceeds the working range of the conventional pump.Therefore,the multiphase pump must have two performances of pump and compressor.Due to the different flow mechanism in the multiphase pump under the different working conditions,the hydraulic excitation characteristics in the multiphase pump are also different,especially under the partial design condition,the hydraulic excitation phenomenon is more obvious.It can be seen that the performance of multiphase pump is very important for its continuous and reliable operation.Therefore,the internal flow characteristics of the multiphase pump are critical to the stability of the multiphase pump during operation.In order to explore the characteristics of internal flow,hydraulic excitation and vibration mode of multiphase pump,this paper uses the method of theoretical analysis and numerical calculation to analyze the internal flow characteristics of multiphase pump.And the reliability of the impeller and diffuser is analyzed in depth,from the perspective of fluid-solid coupling,including the change law of stress and strain on the multiphase pump,the vibration law of the rotor and the natural frequency,and so on.Through study,the following conclusions are drawn:(1)Study on gas-liquid two-phase flow law of multiphase pump under the different conditions.The effects of different liquid phase viscosity and gas volume fraction on streamline distribution,velocity distribution and static pressure distribution in the compress cell were studied.The research shown that the greater the liquid phase viscosity the lower the head of the multiphase pump,the greater the liquid viscosity the greater the shaft power of the multiphase pump.The smaller the liquid phase viscosity the greater the hydraulic efficiency of the multiphase pump.And as the liquid phase viscosity increases,the highest efficiency point moves to the small flow direction.As the viscosity increases,the axial vortex strength at the outlet of the impeller increases first and then decreases.As the gas volume fraction increases,the axial vortex in the compress cell gradually decreases,and the pressure distribution in the diffuser becomes more uniform.(2)Distribution of stress and strain in impeller and diffuser of multiphase pump under the different conditionsIn order to study the law of stress and strain changes on the blade surface,the effects of medium viscosity,flow rate and gas volume fraction on the stress and strain of the blades were systematically analyzed.It is found that the maximum stress is mainly concentrated at the inlet near the hub and the maximum deformation is mainly concentrated at the inlet near the shroud.The maximum stress and maximum deformation in the diffuser occur at the position near the shroud.As the flow rate and viscosity increase,the equivalent stress and deformation of the blade gradually increase,with the increase of gas content,it gradually decreases.(3)Vibration modal analysis of the multiphase pumpIn order to study the modals characteristic of the multiphase pump,the modals with and without prestress were selected and compared,and it analyzes each mode and critical speed under the different axial spacing ratio.The study found that the prestress has little effect on the natural frequency of the rotor,but axial spacing ratio has a greater effect on the natural frequency of the multiphase pump.In the case of prestress,the natural frequency of the rotor is large,and the natural frequency of the rotor is small when there is no prestress.The natural frequency and critical speed of the rotor increase with the increase of the axial spacing ratio.