Study On Gas-liquid Two-phase Flow Characteristics Of Jet Centrifugal Pump

As one of the main equipment of water saving irrigation,jet centrifugal pump plays an important role in the development of water-saving irrigation.In this paper,the gas-liquid two-phase flow simulation of the jet centrifugal pump is carried out by using the double Euler model provided by CFX.And the numerical simulation results are compared and analyzed,and the flow law of the gas-liquid two-phase flow in the jet centrifugal pump is obtained,which can provide reference for the follow-up optimization.The main research contents and innovations are as follows:1)The liquid flow simulation of JET750 jet centrifugal pump was carried out by flow field analysis software CFX.It was found that the circulation flow at the nozzle outlet decreased gradually with the increase of operating conditions,the same as the vorticity value at the nozzle outlet,the throat of the static pressure and the turbulence inside the jet.The velocity of the jet fluid at the outlet of jet device tends to be well-distribute and the flow separation of the diffusion section is gradually reduced.In addition,the overflowing capacity of fluid is enhanced obviously.2)In order to exploring the gas-liquid two-phase flow law of jet centrifugal pump,the gas-liquid two-phase simulations have been carried out separately at the inlet of the pump by setting different operating conditions of different gas concentration and the same imported gas concentration.After the analysis for the simulation results of different rates of vapor content,it is found that as the rates of vapor content at the inlet increase,while the nozzle circulation flow gradually decreases.The impeller gas flow rate as well as the rate of vapor content on each section inside the jet also gradually increase,and the average velocity of the gas phase gradually decreases.After the analysis for the simulation results of different operating conditions and the same kind of imported gas rate,it is found that with the increase of operating conditions,the circulation flow of the nozzle increases gradually.Meanwhile,the impeller's internal gas-phase over-current capacity gets strengthened,with a relatively smaller glide as conditions of low flow.3)The numerical simulation of the gas-liquid two-phase flow has been performed separately by extracting the ejector from the jet centrifugal pump.By setting the nozzle diameter of the jet,The throat diameter,The throat length,and the distance of tube to nozzle as the four testing factors,and the flow rate of the outlet gas phase as the objective function,the orthogonal test sample is fixed.According to the results of the simulation,the following formula is obtained by the matching the four factors of the jet and the objective function through the Isight software:R-squared can be 0.88,the fitting goodness satisfies the requirement of solving,and the influence of each factor on the gas flow capacity of the jet is important,from large to small,respectively asP_o?P_o²?P₁²?P₁?P₁^*P₃?P₀^* P₁?P₁^*P₂ ?P₂²?P₃ ?P₃².However,changing the nozzle diameter and the diameter of the throat will change the area ratio,the area ratio changes for the performance of the self-priming pump plays a vital role.In the test part of the waiting distance and the length of the throat of these two factors to modify,through the self-priming performance and external performance test found that the appropriate increase in the length of the pipe is conducive to improving the self-priming performance,self-priming height from the original 7.45 m raised to 9.1 m,self-priming time from the original 145 s shortened to 90 s,while the external characteristics of the basic remains unchanged,if continue to increase the length of the pipe,the jet flow loss increased dramatically,the external characteristics began to decline.Through the simulation found that the appropriate length of the pipe is not only in the over-current capacity has improved,the pressure at the throat has been reduced,the suction capacity has improved,which for gas-phase over-current capacity is beneficial.This time for the self-priming performance optimization has been applied to the company's products.