Study on Pressure Fluctuations of Unsteady Flow in a Circulating Water Pump

摘要

Based on computational fluid dynamics (CFD) method, the pressure fluctuation characteristics of a circulating water pump are studied by simulating three-dimensional unsteady flow. For discarding any impact on the numerical results, the turbulence model is confirmed through comparison of shear stress transport model (SST k-ω) and renormalized group theory model (RNG k-ε), according to the hydraulic performance experiment. The Fast Fourier Transform (FFT) technology is then adopted to process those fluctuating pressure signals obtained. In addition, the principles of monitoring positions and sampling time are investigated for making a good frequency resolution of the whole pressure fluctuations in the pump. It is founded that the flow is characterized by periodic fluctuations, and the frequency components of pressure fluctuations of monitoring points in the whole flow passage of the pump are basically identical. However, the frequency components are different from each other in proportion. Specially, the blade passing frequency dominates the pressure fluctuations in the impeller outlet. While, the frequencies lower than the blade passing frequency become dominant near the tongue. Moreover, the amplitude increases along the blade passage from leading edge to trailing edge, and the pressure fluctuations on the suction surface are larger than that on the pressure surface. They are similar on the same measuring surface for the suction chamber inlet and circular chamber outlet. Comparing with a volute-type centrifugal pump, the most intense pressure fluctuations appear in the impeller outlet rather than near the tongue, it is supposed that the large gap and the circular shape of the pumping chamber affect the propagation of rotor-stator interaction.