NUMERICAL SIMULATION OF UNSTEADY CAVITATION IN A CENTRIFUGAL IMPELLER

摘要

Several negative factors may lead to centrifugal pump's operation failure, in which cavitation is a complicated and headachy problem. So many researchers have had their interests attracted into the gas-liquid two-phase flow when cavitation is involved. Here cavitation occurring during the liquid transport process with a centrifugal pump was analyzed. The principle of adjusting net positive suction head(NPSH) was employed to induce cavitation. Through combination of two-fluid two-phase model and barotropic fluid assumption, simulation of unsteady cavitation inside a low-specific-speed centrifugal impeller was carried out. Comparison between the computational and relevant experimental results was performed as well. The research indicates: a) the inception of cavitation lies in a cavitation nucleus which cost a long period to set up its integrated shape; b) the cavitation steps further with decreasing of NPSH and the evolution of cavitation region is similar to turbulent diffusion; c) unsteady vortices may lead to irregular cavitation diffusion in the rotating impeller. The results also prove that severe cavitation can destroy the operating stability of a centrifugal pump.