Research On The Influence Of Different Obstacle Structures On The Cavitation Performance Of Centrifugal Pump

Cavitation in the centrifugal pump mainly occurs to the leading edge of the impeller blade and the leading edge cavitation is the origin of the decline in the hydraulic performance of the centrifugal pump.Although the external performance of the centrifugal pump is less affected by cavitation in the initial stage of cavitation,if the centrifugal pump runs for a long time at this stage,it will inevitably cause great cavitation damages to the inlet of the impeller blade.In order to suppress the occurrence of cavitation in the centrifugal pump,this paper takes a low specific speed centrifugal pump as the research object.By arranging single obstacle,discontinuous obstacle and transverse obstacle at the leading edge of the suction surface of the centrifugal pump blades,through the combination of experimental testing and numerical simulation,the influence of these three structures on the initial cavitation performance of the centrifugal pump was analyzed.Under the premise of obtaining a better structure of suppressing the initial cavitation of the centrifugal pump,the geometric parameters of the obstacles were changed,including the position and cross-sectional sizes of the obstacle.The optimal parameters of obstacle to restraining the initial cavitation of centrifugal pump were obtained.The main contents and results in this paper are as follows:(1)This article summarizes the basic theoretical concepts of cavitation and three methods of studying cavitation.Summarize and introduce the research progress of centrifugal pump cavitation and cavitation control in recent years;summarizes the numerical calculation method of turbulence and revises the turbulence model,and improves the prediction accuracy of centrifugal pump cavitation performance by revising the viscosity coefficient;The cavitation models that can be called in the current simulation software and the applicable conditions of each model are summarized.(2)The external characteristic test of the centrifugal pump was carried out on the closed test bench of the centrifugal pump.At the same time,the full channel unsteady numerical simulation of the low specific speed centrifugal pump is carried out.The simulation values were in good agreement with the experimental values,which verified the reliability of the numerical simulation.The cavitation test of the centrifugal pump was carried out at the design flow rate Q=8.6m~3/h,and the variation trend of the simulation curve of the cavitation performance was basically consistent with that of the test curve,which verified the feasibility of the cavitation model.(3)Three different structures,single obstacle,discontinuous obstacle and transverse obstacle,were arranged at the suction front edge of the centrifugal pump blade,and the influences of these three different obstacle structures of the cavitation initial performance of the centrifugal pump were analyzed.The results show that the three kinds of obstacle structures have little influence on the external characteristics of the centrifugal pump,and all the three kinds of obstacle structures can improve the cavitation performance of the centrifugal pump.Among them,the distribution range of low pressure in the impeller with transverse obstacles decreases most obviously,the volume of cavitation decreases the most,and the effect of inhibiting cavitation is the best.(4)Based on the conclusion that the structure of better inhibiting effect on the cavitation initiation of the centrifugal pump is the transverse obstacle,the transverse obstacle structure of the centrifugal pump is taken as the research object,the geometric parameters of the obstacle were changed,and the influence of the position and cross-sectional size of the obstacle on the cavitation performance of the centrifugal pump was studied.Unsteady constant values are calculated for centrifugal pumps with obstacles located at 30%,40%,and 50%of the impeller radius and the cross-sectional shape of the obstacles are 0.5mm×0.5mm,1mm×1mm,and 2mm×2mm.The results show that the inlet velocity at 30%of the radius of the impeller is larger,and the main flow velocity is most affected by obstacles.The obstacles have the best effect on the pressure improvement in the inlet low-pressure area,and thus have the best effect on the inhibition of cavitation.The cross-section size of0.5mm×0.5mm rectangular transverse obstacle structure is smaller,which induces a smaller relative high pressure area and has a smaller inhibitory effect on cavitation.The inhibiting effect of the transverse obstacle structure of the section shape of 2mm×2mm rectangles on cavitation is similar to that of the transverse obstacle structure of the section shape of 1mm×1mm rectangles.However,the transverse obstacle structure of the section shape of 2mm×2mm has a larger size and produces a greater interference from the flow in the impeller.After comprehensive consideration,it is recommended to selecting a transverse obstacle structure of a rectangular section shape of 1mm×1mm arranged at 30%of the impeller radius to inhibit cavitation.