Multi-stage axial hydraulic turbine is a kind of power machinery widely used in oil and gas exploration and development, and its key working parts are the stator and rotor. There are complex vortex structures in the rotor blade cascade, which have a significant impact on the flow loss and output characteristics. Therefore, it is necessary to analyze the vortex structures in the rotor blade cascade. In this paper, the CFD method is used to calculate the internal flow field of the turbine stator and rotor, and the vortex structures in rotor blade cascade are identified by Liutex method, and the influence of fluid viscosity changes on the vortex structure is analyzed. The research results show that there are vortices of spatial structure and face-sheet structure in the rotor blade cascade. Among them, the spatial structure vortices have a large scale, occupy a large flow channel space, have a significant impact on the flow around the blade cascade, and their scale increases with the increase of viscosity. These vortices mainly include horseshoe vortices, passage vortices, separation vortices, corner vortices, and wake vortices. The face-sheet structure vortex is mainly formed by the high-speed friction between the fluid and blades, with the maximum vorticity, and its vorticity slightly decreases with the increase of viscosity, which is the main region of flow loss. This type of vortex is mainly the suction surface boundary layer vortex. The study in this paper elucidates the vortex structures in rotor cascades and their characteristics that vary with viscosity, providing theoretical support for suppressing vortex structures in cascades.

Vortex Identification, Liutex, Hydraulic Turbine, Variable-Viscosity