Numerical Analysis of Pressure Fluctuations Caused by Impeller-Diffuser Interaction in a Mixed Flow Reactor Coolant Pump

Numerical simulation of unsteady three-dimensional turbulent flow in a mixed flow reactor coolant pump was achieved by using a phased-lagged method. Based on Reynolds averaged Navier-Stokes equations with S-A turbulence models in commercial software Numeca, pressure distribution in impeller, diffuser and volute was obtained, and focused on pressure fluctuations caused by impeller-diffuser interaction. The results showed that obvious periodic unsteady pressure fluctuations in impeller and diffuser, but aperiodic pressure fluctuations in volute. Pressure fluctuations became larger from the blade leading edge to the trailing edge. At the leading edge in the diffuser pressure fluctuated on the suction side fluctuations larger than on pressure side. In impeller the frequency of pressure fluctuation was mainly formed of rotation frequency and the frequency which led in by the diffuser. The frequency of pressure fluctuation in the diffuser was the same as the blade passing frequency. The combination of the number in the blade and the diffuser was one mainly factor which caused pressure fluctuation. As a result of this paper, numerical study helped to understand the pressure fluctuation caused by impeller-diffuser, and guided the future design and optimization for the model of the reactor coolant pump.