Optimization And Experimental Research Of High-speed Magnetic Pump

High-speed magnetic pump has been widely used because of its simple structure and zero leakage.In this paper,the impeller,volute and magnetic coupling of a high-speed magnetic pump were optimized by numerical simulation,empirical formula calculation and experimental verification.The main research contents and achievements are summarized as follows:(1)According to the requirements of the contract,a high-speed magnetic pump was designed and developed,which has the characteristics of high speed,large supporting power,compact structure,easy installation and disassembly,and durability.The performance of high-speed magnetic pump was predicted by CFD numerical simulation method.A real prototype was developed and tested.The predicted results were compared with the measured values,and the simulation results were reliable.The cutting performance of high-speed impeller was studied.The calculation results of four kinds of impeller cutting formulas were compared with the measured values at different high speeds.The results show that the calculated results of the four cutting formulas are different from the measured values.For the high-speed magnetic pump designed and developed in this paper,the calculated results of the domestic traditional formula on the performance of the high-speed impeller after cutting are the closest to the measured values.(2)The influence of magnetic block with different axial length on the performance of highspeed magnetic pump was studied.Five kinds of magnetic block schemes with different axial length were designed.The hydraulic friction loss and magnetic eddy current loss of different schemes were calculated by using CFX flow field simulation software and Maxwell magnetic field analysis software respectively,and the performance tests of two schemes were compared.The results show that the energy loss in the magnetic coupling accounts for a large proportion of the total loss of the high-speed magnetic pump unit.With the increase of flow rate,the transmission efficiency of magnetic coupling increases gradually.With the shortening of the length of the magnetic block,the eddy current loss and the friction loss between the inner magnetic rotor and the fluid of the high-speed magnetic pump are reduced,and the unit efficiency and the transmission efficiency of the magnetic coupling are improved.With the increase of the axial length of the magnetic block,the magnetic torque generated by the inner and outer magnetic blocks increases,and the eddy current loss on the isolation sleeve increases in proportion.The proportion of the maximum eddy current loss of high-speed magnetic pump gradually decreases with the increase of flow rate.When the length of magnetic block is shortened,the maximum eddy current loss decreases.Comprehensive calculation verifies that the hydraulic friction loss and magnetic eddy current loss of magnetic coupling of high-speed magnetic pump are innovative.The magnetic field intensity at the junction of adjacent magnets is the largest,and the magnetic equipotential lines generated by the inner and outer magnets form a loop in the corresponding magnets.The local resistance loss in the cooling return channel and the friction loss between the guide bearing and the shaft sleeve during operation cannot be ignored.(3)By optimizing the parameters of high-speed magnetic pump impeller,the performance of the pump was improved.By combining the optimal Latin hypercube sampling method with CFD numerical simulation,8 impeller parameters were optimized.The response surface approximation modeling method and RBF neural network optimization method of ISIGHT software were used to further analyze the correlation between the eight parameters and the performance results.The results show that the blade wrap angle and the profile of the back cover plate have a great influence on the pump efficiency,and the number of blades of the impeller has a great influence on the pump head.After optimization,the impeller model with good efficiency and head was obtained,and the flow field was compared with the original pump.The results show that the flow at the beginning and end of the diaphragm and the region near the volute tongue in the double volute basin is complex,and it will be affected by the dynamic and static interference between the stationary volute and the rotating impeller.The shape of the diaphragm and tongue has a great influence on the backflow and flow around it.(4)The influence of different diaphragm length of double volute on pressure fluctuation in volute and outlet pipe of high-speed magnetic pump was studied.Five kinds of double volute diaphragms with different lengths were designed,and a total of seven monitoring points were set up in the volute and outlet pipe basin.The results show that the main frequency of pressure fluctuation at all monitoring points of different double volute schemes are blade passing frequency and shaft frequency.The fluid flow at the end of the diaphragm and the tongue of the double volute has a great influence on the pressure pulsation inside the volute.When the end of the double volute diaphragm is behind the tongue section,the increase of the length of the diaphragm improves the pressure fluctuation at the volute outlet.When the end of the double volute diaphragm is in front of the diaphragm tongue section,the fluctuation of the diaphragm tongue position becomes more severe with the increase of the diaphragm length.The peak value of scheme 2 is 2.57 times of scheme 1 at the double blade passing frequency.The influence of variable pitch inducer on the pressure fluctuation at the impeller inlet was studied.Three monitoring points were set in the impeller inlet basin of scheme 3 high-speed magnetic pump,and the pressure fluctuation simulation,pressure fluctuation test and cavitation test were carried out with or without front inducer.The results show that the variable pitch inducer can effectively improve the pressure fluctuation near the impeller inlet,but the fluctuation in the inducer basin is more severe.The experimental results show that the variable pitch inducer can effectively improve the cavitation performance of the high-speed magnetic pump.Compared with the pump unit without inducer,the NPSH of the pump with inducer is reduced by 3.39 m,but the efficiency of the high-speed magnetic pump unit is slightly reduced,and the head changes little.