Effect of shear-thinning property on vortex evolution and pressure fluctuation in an axial flow pump

Most of the mediums in the chemical industry exhibit the shear-thinning property, i.e., the effective viscosity decreases with the increasing shear rate. In this work, the effect of shear-thinning property on the vortex structure evolution and induced pressure fluctuation of an axial flow pump is numerically studied. The CMC solution is used as the shear-thinning fluid, and the viscous Newtonian fluid (viscosity equals the apparent viscosity of the shear-thinning fluid as the flow index is 1) is adopted for comparison. The results show that the apparent viscosity variation in the guide vane is more obvious than that of the impeller. In the Newtonian fluid case, two passage vortexes are found in the guide vane passage outlet, but only one larger-scale passage vortex exists for shear-thinning fluid. Meanwhile, the shear-thinning property enhances the interaction between vortices and mainstream, leading to higher pressure fluctuation. Different from the Newtonian fluid case, the rotor-stator interaction and the shear-thinning property play a dominant role in pressure fluctuation, and the shear-thinning property can arouse low-frequency fluctuation components.