| The electric submersible centrifugal pump is one of the main artificial lift technology.It is suitable for high production wells and inclined straight wells.The electric submersible pump has the characteristics of low maintenance cost and small occupation area etc.However,when gas is entrained with liquid into an ESP,the lifting capacity is poor and the pump efficiency is low.When the gas-liquid ratio is large,the gas lock phenomenon will occur,which seriously endangering the normal operation of the pumping well.Research results on the flow properties of two-phase flow in the submersible electric pump is not perfect,Therefore,the research is applied in some electric submersible pump characteristics and flow characteristics,and further reveal the mechanism of two-phase flow,when the gas is entrained with liquid into an ESP.Based on computational fluid dynamics theory,establish a two-phase flow mechanics model of electric submersible pump.Application of CFD software CFX to simulate the condition of single-phase flow and two-phase flow in electric submersible pump.The simulation results are compared with the experimental results to verify the correctness of the simulation results.The gas-liquid two phase flow is simulated in variable flow condition and variable speed.From the steady and transient aspects,the gas volume distribution in the flow field,the pressure field,the velocity field and the change law of the blade load are analyzed in the two phase flow.The results of the analysis are as follows,due to the gas entrainment into electric submersible pump cause the mild deterioration of head,power and efficiency.The gas entrainmented makes the pressure in the flow field increase slightly,and the flow velocity is slightly increased.The severe degradation of ESP performance occurred at higher volume fracture of gas.The distribution of gas phase in the flow field is not uniform.In the axial direction,the gas phase is gathered from the front cover plate to the outlet of the flow channe l in the impeller.The gas void fraction decreases from the front cover to the flow channel.in the rear section of the blade near the front cover plate inside the impeller the gas phase is separated from the liquid phase.When the impeller rotating gas phase showed periodic regular changes of aggregation and spreading in the flow field.When the gas volume fraction increases and the gas void fraction increases,the occupied area expands to the blade working face,and the period increases,the area of the separation of gas and liquid phase is reduced and moves towards the front plate,the pressure in the pump increases slightly,the main flow velocity increases and the eddy current range increases.When the impeller speed increases,the time of gas phase periodic aggregation diffusion is shortened,the maximum concentration of gas gathering in the impeller decreases,and the maximum value of gas gathering concentration in the diffuser increases,the area of high gas void fraction in the impeller is reduced,while the high gas void fraction in the diffuser is increased.The load curve of the blade is not smooth when two phase flow.When the volume fraction of gas phase increases,the amplitude of load fluctuation increases.When the volume fraction of gas phaseincreases,the pressure of the working face at the tail edge of the blade is low.There is regular periodic aggregation and diffusion in the flow path of gas phase,causing the load on both sides of the blade to change regularly,and the pressure difference on both sides of the blade fluctuates in a small amplitude range.The results of this study improve the flow mechanism of the internal flow field when the gas-liquid two phase flow is transported by an electric submersible centrifugal pump.Provides a theoretical guidance for the electric submersible pump for gas-liquid application,and provides theoretical basis for optimizing the structure and performance of electric submersible pump. |
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