| Impeller and diffuser are important parts in the Axial-flow pump and the later is the important part to take back energy. Inner flow of Axial flow pump has direct influence on pumps performance and it's a considered problem by the pump designers. Axial flow pumps, diffuser mixed-flow pumps and tubular pumps are adopted in all pump stations of East Route of South to North Water Diversion Project. The matching of impeller and diffuser is considered in design of the pump stations. It is often needed to change the diffuser to improve the pump's efficiency.In recent years, with the development of the computer technology, CFD (computational fluids dynamics) developed rapidly, and many commercial computation softwares are applied widely. Through three-dimensional turbulent numerical simulation of Axial-flow pump inner flow by CFD, the distribution of the velocity, pressure and cavitation in the pump can be obtained, which give a responsible method to design of the impeller and choice of the diffuser. This method has become one of the important ways to improve efficiency of pumps .In this paper, based on the RANS equation and RNG turbulent model , the numerical simulation of the 3D turbulent flow in a Axial-flow pump impeller and different diffusers. The distribution of the velocity and pressure in the blade-to-blade passage and outside performance are presented at the design and off-design operating conditions , which were compared with the results measured. The computation results indicate that the numerical simulation method is reliable; the number and quality of mesh have influence on the computationed results; diffuser has little influence on impeller's inner inflow which can be ignored; diffuser has great influence on pump's performance; different design operating condition diffuser transfers the high efficiency of the pump; Axial-flow pump's cavitation capability is analyzed in the paper, which can be very helpful to improve and optimize the impeller design. |
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