Effect of vortical structures on cavitation on impeller blades in pumps with suction chambers

27th IAHR Symposium on Hydraulic Machinery and Systems

Škerlavaj, A.^1 ; Pavlin, R.^2

Department for Basic Research and Education, Turbointitut, Rovnikova 7, Ljubljana

1000, Slovenia^1

Pumps Programme, Turbointitut, Rovnikova 7, Ljubljana

1000, Slovenia^2

关键词: Curvature correction;    Direction of rotation;    Double suction pumps;    Impeller geometry;    Shear-stress transport;    Steady-state simulations;    Transient simulation;    Vortical structures;   

Others  :  https://iopscience.iop.org/article/10.1088/1755-1315/22/5/052002/pdf
DOI  :  10.1088/1755-1315/22/5/052002

来源: IOP

【 摘 要 】

A double-suction pump operating at relatively low suction head and with poorly designed suction chambers was analysed by the computational fluid dynamics (CFD). Two impeller geometries were considered - one with thicker and one with thin layer of predicted vapour cavity on blades. Steady-state simulations (SSS) were performed with shear-stress- transport (SST) turbulence model with curvature correction (CC). Transient simulations were performed with scale-adaptive-simulation SST (SAS-SST) model with CC. For both analysed geometries, transient simulations predicted higher maximal thickness of cavities than SSS. In transient simulations it was observed that, because of poor design of suction chambers, near the rib of the suction chambers two stronger (non-cavitating) vortices appeared. Near the main vortical structures, vortices with smaller intensity appeared, with direction of rotation opposite to the main vortices. Depending on their position and direction of rotation, the vortices either decreased or increased the extent of cavitation. The most important adverse effect was to increase the size of the sheet cavity by local elongation and thickening. The local effect seemed to be more pronounced for impeller with smaller thickness of sheet cavity.