Dynamic Numerical Analysis And Optimization Of Water-based Liquid Three-screw Pump

Three screw pump as a kind of high precision displacement pumps,It has a reputation for small pressure fluctuation,low noise,high efficiency,compact structure,can be reverse rotation etc.Over the past twenty years,as requirement of water-based hydraulic fluid rised dramadicly,the water-based hydraulic system powered by three-screw pump,which becomes one of the future research directions.The characteristics of the water-based hydraulic fluid are different from the mineral hydraulic oil,which will lead to pump leakage increase,vibration increase,abnormal noise and other problems.It is difficult to express the relationship between each parameter and pump performance with mathematical analytical model precisely because of the complex internal structure,many factors affecting pump performance and the interaction among various parameters.The current pump design usually follows the empirical formula derived from past tests.For the design of the water-based liquid three-screw pump,the design result of the empirical formula often deviates greatly from the actual result.Therefore,based on the dynamic numerical analysis technology,this paper systematically studies the influence of the working parameters of the three-screw pump on the performance of the water-based liquid,the cavitation problem,the force of the pump bushing,etc.And the optimum efficiency parameters of water-based liquid three-screw pump are analyzed and optimized.Through the analysis of three-screw pump structure and end face profile,the virtual prototype of three-screw pump is established,and the internal flow passage of three-screw pump is extracted.The viscosity-temperature characteristics of water-based hydraulic fluid and the corrosion resistance of material of main-slave screw and screw bushing in water-based hydraulic fluid are obtained.The complex flow channel inside the screw pump is divided into the structured hexahedral mesh,and the interaction surface is created in each calculation domain.The comparison between the static coordinate method in the rotating coordinate system,the adaptive dynamic mesh method and the static mesh reconstruction method is carried out.The same boundary conditions as the actual working conditions are set to realize the dynamic numerical analysis of the three-screw pump.The internal flow field characteristics of the water-based liquid three-screw pump were analyzed by CFD analysis technology.The flow and leakage of the three-screw pump,the force and torque of the master-slave screw were solved.The relationship between the flow rate of No.32 hydraulic fluid and water-based liquid and the torque of screw and temperature is compared and analyzed.And the influence of the inlet and outlet pressures of the pump and the screw speed on the cavitation phenomenon are analyzed.The allowable suction height of the water-based liquid three-screw pump is determined.At the same time,a test bench was set up to analyze and correct the simulation model.Thus,the correctness of the dynamic numerical analysis model is verified.The static analysis method is used to analyze the maximum stress and the position where the maximum stress applied to the screw bushing,which provides a theoretical basis for the friction and wear test of the screw and bushing.Based on the range analysis,five design factors that have the greatest influence on pump flow and pump efficiency are selected.Based on the Box-Behnken design theory,the least squares method is used to fit the quadratic regression model of each factor with pump flow and pump efficiency.An optimal efficiency model with rated outlet pressure and pump output flow as constraints is established.The optimal efficiency of the pump under different clearances was investigated.The optimal working parameters of the water-based liquid three-screw pump were solved.The superiority of the optimized results is verified by comparing the working characteristics of the optimized model with the original model.