Computational Fluid Dynamics of Cavitating Flow in Mixed Flow Pump with Closed Type Impeller

Abstract

LES(Large Eddy Simulation) with a cavitation model was performed to calculate an unsteady flow for a mixed flow pump with a closed type impeller. First, the comparison between the numerical and experimental results was done to evaluate a computational accuracy. Second, the torque acting on the blade was calculated by simulation to investigate how the cavitation caused the fluctuation of torque. The absolute pressure around the leading edge on the suction side of blade surface had positive impulsive peaks in both the numerical and experimental results. The simulation showed that those peaks were caused by the cavitaion which contracted and vanished around the leading edge. The absolute pressure was predicted by simulation with -10% error. The absolute pressure around the trailing edge on the suction side of blade surface had no impulsive peaks in both the numerical and experimental results, because the absolute pressure was 100 times higher than the saturated vapor pressure. The simulation results showed that the cavitation was generated around the throat, then contracted and finally vanished. The simulated pump had five throats and cavitation behaviors such as contraction and vanishing around five throats were different from each other. For instance, the cavitations around those five throats were not vanished at the same time. When the cavitation was contracted and finally vanished, the absolute pressure on the blade surface was increased. When the cavitation was contracted around the throat located on the pressure side of blade surface, the pressure became high on the pressure side of blade surface. It caused the 1.4 times higher impulsive peak in the torque than the averaged value. On the other hand, when the cavitation was contracted around the throat located on the suction side of blade surface, the pressure became high on the suction side of blade surface. It caused the 0.4 times lower impulsive peak in the torque than the averaged value. The cavitation around the throat caused the large fluctuation in torque acting on the blade.

Numerical Simulation of Interaction between Fluid and Vapor Structures in Multiphase Flow around Hydrofoil

“…The cavitation instabilities have been investigated experimentally and numerically also in mixed-flow pumps [3] [4] with results similar to the ones obtained with inducers. The problems of the surge instability of a cavitating propeller were studied experimentally in [5] and analyzed numerically in [6].…”

CFD Analysis of Cavitation Phenomena in Mixed-Flow Pump

“…[1][2][3][4][5][6][7], but they are mostly concerned with the steady cavitation. Kobayashi and Chiba [8] modelled unsteady hydraulic forces acting on the impeller of a mixed-flow pump operated under cavitation using the Large Eddy Simulations (LES) while Yamamoto and Tsujimoto [9] studied extensively the cavitation surge in a centrifugal pump. Nevertheless there is still lack of information in the literature concerning cavitation instabilities in the mixed-flow or radial-flow pumps.…”

Effects of Volute Throat Enlargement and Fluid Viscosity on the Performance of an Over Hung Centrifugal Pump

“…Liu et al [24] conducted an analysis of unsteady attached sheet cavitating flows in a centrifugal pump. Kobayashi and Chiba [25] carried out a research on the cavitating flow in mixed flow pump numerically. Their analyzed pump had five throats and behaviors.…”