Numerical Simulation And Optimal Design Study On Centrifugal Pumps With Splitters

The low-specific-speed centrifugal pumps are used widely in petrochemical industry, light industry and aerospace engineering because of their little discharge, high water-head, compact structure, easy maintenance features. Concerning for their extensive usage, it’s important for the running being safety, stability and high efficiency. In order to improve centrifugal pump performance, three impellers with splitters were studied from the perspective of internal flow field in this paper. Three compound impellers with different short vanes were designed. A three-dimensional turbulent numerical simulation method was used to research their internal and external characteristics under varied rotating speeds, their transient characteristics, the optimal way to set slots on the long blades. The main works and achievements are as follows:(1) A large amount of achievements about compound impeller centrifugal pump design,the operation of pump under variable speeds, the transient characteristics on centrifugal pump and the application of flow control technology in rotating machinery were analyzed and concluded. After the works had been done, the research directions were proposed.(2) The internal flow characteristics were analyzed using the superposition of the plane potential.The differences between no viscous assumption flow and viscous flow were compared. The reason of flow separation phenomenon at the impeller outlet near the suction surface under a wide variety of forces was discussed. In order to improve the situation, three compound impellers with the same long blades and different short blades and a supporting volute were designed.(3) By using the method of three dimensional turbulent numerical simulation, the internal and external features of the compound impeller pumps under different rotational speeds were obtained. The law of fluid particles’velocity vector deflection to the pressure side due to the increase of implications centrifugal acceleration, the relative acceleration, the increase of the Coriolis acceleration, the increase of velocity circulation caused by the viscous force was analyzed. The conclusions show that the velocity vector deflections become greater as the speed increases and the dimensionless performance curves’offset increases.(4) How the slots’radial location D1, radial width W1and angle β3effect on the performance of the pumps was studied by Orthogonal experiment design method. Furthermore, an appropriate slot setting way for improving pump performance was put forward. The results reveal that the impeller with slots at0.37(D1+D2), the width of2mm is of good hydraulic performance.(5) In order to research the compound impeller centrifugal pumps" transient characteristics, three-dimensional unsteady turbulent numerical simulations were conducted on the three compound impellers under three working conditions. The numerical results indicate that the internal flow field and the pressure at pumps’outlets change periodically as the impeller rotate under different working conditions. The frequency-domain characteristics figures indicate that C impeller’s pressure pulsation amplitude is larger than the others. The pumps’ outlet pressure pulsation amplitudes appear increasing trend as the mass flow increase.