Influence Of Blade Outlet Angle On Flow Induced Noise Inside Centrifugal Pump

Flow-induced noise is one of the primary noises in centrifugal pumps. The level anddirectivity of the noise is related to the pressure fluctuation inside the pump, which isgenerated by the strong interaction among the blades, volute and fluid as pump isrunning. The geometric parameters of the blade have important effects on pressurefluctuation and flow-induced noise. Blade outlet angle is one of the most importantgeometric parameters of centrifugal pumps. The research about the influence of bladeoutlet angle on pressure fluctuation and flow induced noise is very beneficial tocontrolling the flow induced noise. Both experimental and numerical methods wereemployed in this paper to study the production mechanism and distributioncharacteristic of pressure fluctuation and vibration of a centrifugal pump, and then theeffect of blade outlet angle was investigated with numerical method. The maincomponents of this paper are listed as follows:1According to the GB/T3216-2005and GB/T3214-2007, a test-bed for themeasure of the performance, pressure fluctuation and vibration of a centrifugal pump.A damping screen and clapboards were designed to cutting down the pressure wave ofinlet; Reasonable measuring instruments and data acquisition scheme were designed;2Performance and pressure fluctuation parameters of the centrifugal pumpIS100-80-160were measured on the test-bed and compared with the numerical data.The result shows that both head and efficiency measured by experiment are fit wellwith the numerical solution. The maximum error of the head between them is about7%and the error of efficiency is about11.5%. Experiment results show that the pressure offluid fluctuates mainly at blade passing frequency (BPF) and shaft frequency whilenumerical method only catch the pressure fluctuation at blade passing frequency.Results of volute vibration show that the vibration acceleration is around1~3m/s2.3The performances of a centrifugal pump under different blade outlet angles arepredicted and large eddy method is applied to simulate the unsteady flow field in themodels. Results show that the head of pump increases7%while the efficiencydecreases5.1%as the blade outlet angle increases from18°to39°. The Pressurefluctuation intensity at BPF frequency decreases and the intensity increases at secondorder harmonic frequency. And the total power of pressure fluctuation has increased12%as outlet angle increases from18°to39°. Blade force acting on the impeller in radial direction is much higher than in axial direction and the fluctuation frequency issame to blade passing frequency.4Based on mode of volute and the pressure fluctuation which exported fromunsteady flow-field computation, a vibro-acoustic coupling method is used to calculatethe vibration and noise induced by the flow exciting force. Result shows that thevibration velocity of the volute wall in second order harmonic frequency is higher thanin other frequencies. The sound pressure level has increased8.6dB as blade outletangle grows from18°to39°. Results of acoustic power level show that the acousticpower level increases as blade outlet angle grows.