Research On The Cavitation Performance Of Axial Flow Pump By Slotted Blade

Since 1893,when the destroyer’s propeller was broken down and cavitation was discovered,experts and scholars in the field of hydraulic machinery have begun to study cavitation for more than 100 years.To this day,cavitation is still the focus of attention of domestic and foreign scholars.Although in the fields of medical,chemical and national defense,people have begun to use the high energy conversion characteristics of cavitation,but in hydraulic machinery,cavitation will produce vibration,noise and cavitation and other negative effects,which will affect the normal operation of hydraulic machinery.Cause harm,but these negative effects cannot be completely eliminated.Therefore,exploring the cavitation control technology of hydraulic machinery has certain research value.Due to the large distortion of the blades of the axial flow pump,the complicated flow,and the serious cavitation phenomenon,the control of the cavitation of the axial flow pump has always been the focus of attention by scholars at home and abroad.Through theoretical analysis,it introduces the research status of axial flow pump cavitation characteristics and cavitation research methods in detail,briefly summarizes the research and development status of domestic and foreign scholars on cavitation control methods,as well as the research status of slotting technology in the field of hydraulic machinery.Introduce the turbulence model and cavitation models in the field of cavitation numerical simulation.Combined with previous research results,the turbulence models and cavitation models used in this paper are modified SST k-ωturbulence model and Zwart-Gerber-Belamri cavitation model..On the basis of the research results of domestic and foreign scholars,this project opened a groove at the front edge of the back of the axial flow pump blade to study the effect of the slotted blade on the cavitation control of the axial flow pump,and analyzed the cavitation flow inside the axial flow pump.It also puts forward the influence of different slot sizes and different slot numbers on the cavitation of axial flow pumps,mainly including the following research contents:(1)Taking the submersible axial flow pump as the research object,analyze its external characteristics and cavitation characteristics through numerical calculation methods.By comparing the external characteristic results of the experiment and the numerical simulation,the reliability of the numerical calculation is verified.By analyzing the characteristics of the internal flow field of the impeller under different cavitation degrees,the results show that cavitation first appears at the position of the inlet side of the blade near the rim,and gradually expands toward the outlet side.As the degree of cavitation deepens,cavitation in the middle and rear of the blade Gradually intensify.(2)Compare and analyze the steady and unsteady calculation results of the original model and the three slotted models,study the effect of the slotted blade on the cavity volume fraction distribution,pressure distribution,turbulent kinetic energy and pressure fluctuation changes in the impeller,and explore the blade slot size improves the flow inside the impeller runner and the mechanism for enhancing the cavitation performance.The research has concluded that opening a rectangular groove at the leading edge of the back of the blade can improve the head and efficiency of the axial flow pump;opening the groove increases the flow area of the blade inlet,improves the pressure distribution on the back of the blade,and reduces the position of the blade inlet.The distribution of turbulent kinetic energy makes the flow more stable,and the volume fraction of cavitation in each stage of cavitation decreases.Among them,the effect on the initial stage of cavitation development is the most obvious,which can effectively inhibit the development of cavitation.(3)Compare the internal flow field simulation results of the original model and the four slotted models,and analyze the effects of the original model and the four slotted blades on the pressure distribution,velocity vector distribution,cavity volume fraction and pressure pulsation changes at the slot position,To explore the mechanism of improving the flow in the impeller runner and enhancing the cavitation performance with different slot numbers of the blades.The study concluded that four rectangular grooves of 1mm×1mm with a pitch of 3mm are opened in sequence at the leading edge of the back of the blade,which can improve the head and efficiency of the axial flow pump,increase the relative high pressure area at the blade inlet,and the pressure gradient on the back of the blade.The increase in the low-velocity area of the flow increases,and the volume fraction of cavitation in each stage of cavitation decreases.Among them,the effect on the initial stage of cavitation development is the most obvious.Therefore,a reasonable distribution of multiple grooves can effectively inhibit the development of cavitation.