Influence Of Blade Profile Deviation On Internal Flow And Cavitation Performance Of Centrifugal Pump

Impeller is the core overflowing part of centrifugal pump,and blade,as the basic unit of impeller,plays an important role in the performance of centrifugal pump.The blade bending,torsion and other spatial characteristics make the blade difficult to process,and often fail to meet the design requirements,which has an impact on the performance of the pump.This paper focuses on the profile deviation of blade processing and takes a single stage single-suction centrifugal pump as the research object.The profile of impeller blade was biased 1mm in forward and negative directions respectively,composed of three different profile centrifugal pumps(Ori model,model of A1,B1).Study the internal and external characteristics and cavitation of centrifugal pump due to the machining deviation of blade profile.The main contents and conclusions of the study are as follows:Firstly,taking the Clark-Y hydrofoil as the model,the morphological structure of cavitation flow field around the hydrofoil is simulated,and the adaptability of the two turbulence models(RANS and DDES)is compared and analyzed.The two turbulence models can better calculate the generation,development,shedding and collapse of holes in one period.The DDES model is more suitable than the RANS model to calculate the unsteady large separation flow.Secondly,using RNG k-? turbulence model,three kinds of centrifugal pumps with different blade contours are simulated without cavitation.The results show that the deviation of blade profile has great influence on the head of centrifugal pump,and has little effect on efficiency.The positive bias profile has the function of lifting the head of the centrifugal pump,and the negative bias profile has the effect of decreasing the head of the centrifugal pump.Under the same flow condition,the greater the blade profile,the greater the outlet pressure of the impeller and the volute,and the higher the high pressure area.The weaker the turbulence pulsation is,the more stable the flow is.The load distribution on the blade is related to the working condition.Under rated working conditions,the blade profile machining deviation has little effect on the flow in the pump,but when deviating from the design condition,the influence is great.Thirdly,the cavitation state of three centrifugal pumps with different blade contours is simulated.The results show that,compared with the original model,when the blade profile is positively biased,the primary cavitation point lags behind,the critical cavitation point is advanced,and the cavitation resistance is poor.When theprofile is negative bias,the primary cavitation point is advanced and the critical cavitation point lags behind,which can restrain the cavitation flow.The thinner the blade profile is,the greater the anti-cavitation performance of the pump is.In the process of cavitation occurring in the centrifugal pump,the process of cavitation development is different among different channels,and the velocity of cavitation development is also different in each channel,which makes the cavitation state of different channels obviously different.Finally,DDES turbulence model is used to simulate the unsteady cavitation state of three centrifugal pumps with blade contours.The results show that the severe cavitation condition,compared to the original model,the blade profile of a negative bias,the pump pulse is most intense,the blade profile of the forward bias,the pump pressure fluctuation in the impeller inlet most gently.At the inlet of the impeller,the fluctuation on the back side is obviously smaller than that on the working face,while at the outlet of the impeller,the fluctuation on the back side is stronger than that on the working face.At the critical cavitation point in the pump,the amplitude of pressure fluctuation is larger and the high frequency region is disordered.In the serious cavitation state,the high frequency region is relatively stable and the pressure fluctuates slightly.