Influence Of Different Blade Trailing Edge On Internal Unstable Flow And Vibration Characteristics In Centrifugal Pump

As a core component of fluid conveying system,centrifugal pump is widely used in various industrial and national defense fields.The safe and stable operation of the pump is an important guarantee for the normal operation of the system.However,the vibration caused by the unstable flow in the pump will seriously affect the safe and stable operation of the centrifugal pump.Changing the shape of the trailing edge of the centrifugal pump blade is one of the effective means to reduce the fluid excitation of the centrifugal pump,which can effectively improve the unstable flow between the trailing edge of the blade and the volute.In this paper,the vibration of the centrifugal pump is improved by changing the cutting angle of the blade trailing edge.The influence of the cutting angle of the blade trailing edge on the centrifugal pump performance,unstable flow and pressure pulsation was analyzed by numerical simulation method.And the vibration characteristics of the different blade trailing edge impellers were analyzed under the design conditions.This study is important for improving the unstable flow and vibration on the centrifugal pump.The main research contents of this paper are as follows:(1)The three dimensions full flow field and rotor structure of the centrifugal pump with different blade trailing edge were modeled,and the fluid and solid domains were meshed separately.Based on FLUENT and ANSYS Workbench software,the fluid-solid coupling numerical simulation of the internal flow field and rotor system of the centrifugal pump was carried out.The characteristics,pressure pulsation and rotor structure vibration displacement results of original pump obtained by numerical simulation were compared with the experimental results to verify the adoption.(2)Through the analysis of the performance of the centrifugal pump and the internal flow numerical simulation results of different blade trailing edges,it is found that the cutting angle of different trailing edge promoted or inhibited the pump head,efficiency,minimum efficiency index CMEI value and internal unstable flow structure of the centrifugal pump.Among them,the centrifugal pump with the blade trailing edge cutting angle of 30°,45° and 60° has better performance.And these three schemes have certain improvement effects on unstable flow structures such as the backflow vortex of the tongue region and the shedding vortex of the blade trailing edge.(3)The pressure pulsation spectrum,pressure pulsation energy and intensity of the centrifugal pump with different blade trailing edge were analyzed.At different flow rates,it was found that when the blade trailing edge cutting angle was 30°,45° and 60°,the pressure pulsation main frequency amplitude,pressure pulsation energy and intensity were all reduced and less affected by the flow rate.When the blade trailing edge cutting angle was 15°,75° and 90°,the pressure pulsation were increased.The bispectrum analysis of the pressure pulsation signal at the tongue of the centrifugal pump at a small flow rate shows that the nonlinear fundamental characteristic frequencies of the tongue are different due to the different influences of the different trailing edge blades on the unstable vortex structure of the tongue(4)Under the design conditions,the dynamics and vibration characteristics of the rotor system with different blade trailing edge were analyzed.It was found that the impeller with the blade trailing edge cutting angle of 30° and 45° has the effect of reducing the radial fluid excitation force of the impeller,the equivalent dynamic stress at each position of the trailing edge of the blade,the vibration displacement of the impeller,the vibration intensity and the vibration energy of the impeller.