Unstable head-flow characteristics of pump-turbine under different guide vane openings in pump mode
LI Deyou1, GONG Ruzhi1, WANG Hongjie1, WEI Xianzhu1, 2, LIU Zhansheng1, QIN Daqing1, 2
1.School of Energy Science and Engineering, Harbin Institute of Technology, Harbin, Heilongjiang 150001, China; 2.State Key Laboratory of Hydro-Power Equipment, Harbin Institute of Large Electrical Machinery, Harbin, Heilongjiang 150040, China
In order to obtain the unstable head-flow characteristics of pump-turbines under different guide vane openings, firstly, experiments are carried out on the pump-turbine model for a pump storage power plant in pump mode. It is shown that the head gets higher and its slope becomes stepper at a low flow rate; the unstable head-flow effect exhibits more obviously with decreasing guide vane opening, but the flow rate range for the effect is shrunk. Further, a 3D geometrical model of the pump-turbine model is generated and a set of mesh for its fluid domain is created. The steady turbulent flows in in the pump-turbine model are simulated by using the SST k-ω, standard k-ω, RNG k-ε and standard k-ε turbulence models at various flow rates under 19 mm guide vane opening, showing the SST k-ω turbulence model can result in more accurate performance curves than the others against the experimental measurements. Consequently, the flows in the pump-turbine model are simulated by means of that turbulence model at 13 mm, 19 mm and 25 mm guide vane openings and the head, torque and efficiency curves are obtained and compared with the experimental observations, and good agreement is demonstrated between them. Finally, the internal flow patterns in the unstable region, at part-load, best efficiency and over-load points are analysed at 19 mm guide vane opening. It is identified that the unstable head-flow effect is related to flow separation and vortex occurrence in the runner and a few stay vane passages.
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