Research On Cavitation Suppression Of Low Specific Speed Centrifugal Pumps With Different Structures

Centrifugal pumps play an important role in the national economy.Cavitation has always existed in centrifugal pumps.Cavitation not only reduces the lift and efficiency of the centrifugal pump,but also affects the internal transient characteristics of the centrifugal pump and induces vibration and noise.The suppression of cavitation in centrifugal pumps has always been a research hotspot in academia.Understanding the mechanism of cavitation in centrifugal pumps and exploring suppression methods are extremely important significance in academic research and engineering applications.This paper uses a combination of experimental research and numerical calculation to explore a method of suppressing cavitation for a low specific speed centrifugal pump with a specific speed of n_s=32.During the research,the simulated value and the experimental value were compared,which proved that the SST k-ωturbulence model and the Zwart cavitation model used in the numerical calculation have good applicability.The numerical calculation method was used to observe the development of cavitation inside the centrifugal pump.And then deeply unders tand the cavitation mechanism of centrifugal pumps,and on this basis,three methods to inhibit the development of cavitation in centrifugal pumps are proposed.In the first part of this article,the hydraulic model of the centrifugal pump is introduced,the visualization experiment of the centri fugal pump is carried out,and the related devices of the visualization experi ment platform of the centrifugal pump,the visualization experiment scheme of the centrifugal pump and the data processing process after the experiment are completed are introduc ed in detail.And draw the external characteristic curve and cavitation charac teristic curve of the centrifugal pump.In the second part of this article,Proe5.0 software was used to model the computational domain in three dimensions,ICEM15.0 software was used to mesh the computational domain,and the grid independence was verified,Thereby eliminating the influence of the number of grids on the calculation results.The boundary conditions and solution settings in t he numerical calculation are introduced i n detail.The modified SST k-ωturbulence model and the Zwart cavitation model are used to perform numerical calculations on the centrifugal pump.The simulation values of the external characteristics and cavitation characteristics are compared with the experimental values,which proves the applicability of the SST k-ωturbulence model and the Zwart cavitation model in this study.The cavitation development process in the centrifugal pump is predicted by numerical me thods.Cavitation first occurs at the inlet side of the suction surface of the blade.With the development of cavitatio n,the volume of cavitation in the impeller flow passage continues to increase,and the low-pressure zone moves from the inlet to the out let.the main frequency amplitude of pressure pulsation near the impeller inlet becomes smaller and smaller with the development of cavitation,and the main frequency amplitude of pressure pulsation at other positions in the impeller channel becomes larger and larger with the development of cavitation.In the third part of this article,the effect of the bionic convex stru cture on the pressure surface of the blade,obstacles on the pressure surface and suction surface of the blade,and the bionic concave-convex structure on the suction surface of the blade are explored to inhibit the development of cavitation in the centrif ugal pump.After the blade is arranged with the bionic convex structure,the lift and efficiency of the centrifugal pump are slightly reduced.The bionic convex structure increas es the surface roughness of the blade and reduces the cavitation volume and tu rbulent kinetic energy in the impeller flow path under the same cavitation number.When the numberσ=1.42,the bionic convex structure has the best effect on suppressing cavitation in the centrifugal pump.At this time,the volume reduction of cavitation in the impeller channel is 57.9%.When obstacles are arranged on the pressure surface and suction surface of the blade at the same time,t he lift and efficiency of the centrifugal pump drop slightly.The obstacle effectively blocks the back jet,reduces the volume of cavitation and turbulent kinetic energy in the impeller flow path under the same cavitation number.When the cavitation numberσ=1.42 Obstacles have the best inhibitory effect on the development of cavitation in the centrifugal pump.At this time,the volume reduction of cavitation in the impeller channel is 53.6%.After the bionic concave-convex structure is arranged on the suction surface of the blade,the lift efficiency of the centrifugal pump decreases slightly.The bionic concave-convex structure increases the surface roughness of the blade,induces a relatively high pressure area near the blade wall,and effectively inhibi ts the increase of the cavity volume in the impeller.When the numberσ=0.82,the bionic concavo-convex structure has the best suppression effect on cavitation in the centrifugal pump.At this time,the volume reduction of cavitation in the impeller channe l is 51%.