Pressure fluctuation of solid-liquid flow in stator and rotor cascades of pump as turbine
HAN Wei1,2, LI Xuefeng1,2*, SU Min3, LI Rennian1,2, CHEN Hao1,2
1.School of Energy and Power Engineering, Lanzhou University of Technology, Lanzhou, Gansu 730050, China; 2.Gansu Key Laboratory of Fluid Machinery and System, Lanzhou, Gansu 730050, China; 3.College of Electrical and Information Engineering, Lanzhou University of Technology, Lanzhou, Gansu 730050, China
In order to study the pressure fluctuation characteristics of solid-liquid flow in stator and rotor cascades of pump as turbine, the centrifugal pump with space diffuser as turbine is chosen, and then the unsteady 3D flow field was simulated based on the large-eddy simulation(LES)and Mixture multiphase flow model with structured hexahedral mesh generated in ICEM. The pressure fluctuations under three different flow in water and solid-liquid two-phase were monitored in the numerical calculation. The results showed that the point P3 between the stator and the rotor and the point P6 in the guide vane are due to the pressure gradient alternating change in the impeller under the water and solid-liquid two-phase, the periodicity of the pressure fluctuations in time domain is obvious, and consis-tent with the blade passing period. The presence of particles reduces the backflow of the draft tube, which makes the pressure fluctuation more stable at the small flow rate, and the existence of particles increases the flow field disturbance at the large flow rate. The results of the pressure fluctuations in frequency domain reveal that the main frequency are of the blade passing frequency(BPF)and the harmonic frequency is a multiple of the blade passing frequency at different conditions, and its amplitude shows exponential decay. The vortex induces second-harmonic in the impeller obviously. The particles enhance the high-frequency pressure fluctuation at the small flow rate while those weaken it at the large flow rate.
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