Numerical Study of the Effect of Splitter Blades on the Flow-Induced Noise of Hydraulic Turbine

Abstract

In order to study the effect of splitter blades on the internal and external sound field of the hydraulic turbine, the paper chose a centrifugal pump with a specific speed n s = 33 reversed as a hydraulic turbine as the research object, and added the short blades on the original impeller to form a new splitter impeller. Based on the Re-Normalization Group (RNG) k-ε turbulence model to conduct numerical simulation for the hydraulic turbine, this thesis calculated the internal and external acoustic field by means of the acoustic boundary element (BEM) and finite element (FEM) and analyzed the noise radiation characteristics of the two models under different working conditions. The results show that the blade frequency is the main factor affecting the inlet and outlet sound pressure, and the optimized model decreases the inlet and outlet sound pressure levels by 6.84 and 7.24 dB in optimal working conditions. Rotor-stator interaction is the main reason for the flow-induced noise of hydraulic turbine volute appearing, the optimized model can effectively reduce the impeller and volute rotor-stator interaction and the flow-induced noise of volute. Outfield maximum sound pressure appears at the inlet and the volute tongue, which decreased by 1.84, 6.07, and 5.24 dB at each operating condition. To sum up, splitter blades can improve hydraulic characteristics and flow field noise in the hydraulic turbine. KEYWORDSHydraulic turbine; splitter blades; pressure fluctuation; sound field Nomenclature D 1 Impeller inlet diameter (mm) D 2 Impeller outlet diameter (mm) b 2 Inlet width (mm) Z Impeller outlet diameter (mm) D 3 Volute base circle diameter (mm) b 3 Volute outlet width (mm) D Volute inlet diameter (mm) D sb short blade inlet diameter (mm)