| In the crude oil development project,to achieve the purpose of improving the production capacity of crude oil and increasing the profit of oil field development,it is necessary to use gas-liquid mixing pump to pressurize and transport the multi-phase mixing medium.Among them,the spiral axial flow gas-liquid mixing pump has the advantages of conveying large flow rate and simple and compact structure,and has wide application prospects.However,when conveying gas-liquid two-phase medium,it is easy for the gas phase to gather in the impeller flow channel and block the flow channel,resulting in pump failure and performance degradation.Therefore,this paper conducts an in-depth study on the gas-phase flow law and gas-phase agglomeration in the spiral axial flow gas-liquid hybrid pump,which has a certain reference value for improving the performance and stability of the gas-liquid hybrid pump.In this paper,we use Eulerian multiphase flow model and SST k-ω turbulence model to analyze the external and flow characteristics of the spiral axial flow gas-liquid hybrid pump with different gas content,different rotational speeds and different liquid phase viscosities,and investigate the influence of different operating conditions on the hybrid pump.The trajectory of the gas phase inside the impeller and guide vane in the flow channel and the changes under different working conditions are analyzed,the theoretical equations of motion of the bubble are established according to the bubble forces,as well as the numerical equations of motion of the bubble established by using the surface interpolation method and the volume interpolation method,and finally the agglomeration process of the gas phase inside the impeller and the influencing factors are analyzed.The main conclusions are as follows:(1)When the gas-liquid mixed flow pump is used to transport two-phase flow media,an increase in gas content,speed,and liquid viscosity will decrease the pump’s performance.For example,when the gas content is 60%,increasing the speed from3000 rpm to 5000 rpm results in an increase in head coefficient Ψ by 0.537 and efficiency η by 39.2%;however,when the liquid viscosity increases from0.001-0.17838Pa·s,the head coefficient Ψ decreases by 0.4419 and efficiency ηdecreases by 61.37%.The flow characteristics of the helical axial mixed flow pump also change under different operating conditions.It was found that the gas volume fraction on the back of the blade is higher than the working surface,and the gas mainly moves towards the suction surface of the blade.High gas content will cause more severe gas accumulation inside the impeller and guide vanes,and high speed will cause bubbles to break and more small bubbles to gather at the hub.However,an increase in liquid viscosity can alleviate the phenomenon of gas accumulation.(2)The gas phase appears differently at each flow surface in the flow channel.The gas phase gathers in the second half of the working surface of the impeller and moves toward the hub,the first half of the back of the impeller moves toward the hub,the second half moves toward the wheel edge due to the backflow,the gas phase moves toward the wheel edge at the working surface of the guide vane,and the gas phase moves toward the wheel hub at the back of the guide vane.And under different working conditions,the trajectory of gas phase movement will not change.(3)When analyzing the degree of gas-phase aggregation,the gas continuously gathers in the latter half of the impeller and eventually stabilizes.The highest degree of gas-phase aggregation occurs under high gas content,high speed,and high viscosity,with a maximum value of 16.Analysis of the factors influencing gas-phase aggregation revealed that changes in pressure gradients within the impeller and vortices generated by flow are the main causes of aggregation development.As the gas flows,the pressure within the impeller changes with position,and vortices generated by flow also affect gas flow and distribution,resulting in the development of gas-phase aggregation. |
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