Numerical Simulation Research On Pump-turbine During Dynamic Process Of Guide Vane

With the development of society, people are constantly increasing demand for electricity, in order to be more efficient and rational to make use of energy, pump turbine plays an important role. It would seriously threat the stability and safety of pump turbine when unstable flow occurs during the process of converting conditions. To analyze the aspect of internal flow and the characteristics of pressure, velocity and vortex, unsteady numerical simulations have been conducted by using the RNG k-ε turbulence to simulate model of a pump turbine under different guide vanes’ opening angles and guide vanes’ moving process in pump mode. Pressure fluctuation has been discussed in detail, so as to provide a reference for pump turbine operating in pump mode. The main contents of this thesis are as follows:1. The unsteady CFD simulation of different guide vane openings in 13 mm, 19 mm and 25 mm was conducted respectively to analyze the evolutions of internal flow states under these three different kinds of opening angles, which includes the characteristics of pressure, velocity and the structures of vortex, as well as the relationship between internal flow and pressure fluctuation by the method of FFT.2. Moving mesh method was used for pump turbine unsteady simulation with guide vanes opening from 9mm to 26 mm. Compared with guide vanes fixed opening process, this thesis figure out the differences of characteristics and structures of pressure, velocity and vortex. By the method of FFT and STFT, the effect of guid e vanes’ moving on the characteristics of pressure fluctuation was explored.3. Unsteady simulation in pump mode under different guide vanes’ angular speed and different guide vanes’ way of moving was conducted. To analyze the effects of guide vanes moving in different angular speeds and ways on internal flow states and the distribution characteristics of pressure fluctuation, the simulation results have been discussed in detail including counter, streamline and vortex, especially pressure pulsation amplitude in time domain and frequency domain characteristics. This thesis also discussed the pressure fluctuation propagation regulation in pump mode.The results show that, there’re many complicated structures of vortex and flow blockages in pump mode with small guide vane openings. The main pressure fluctuation frequencies in pump mode are from runner blade passing frequency and its harmonic frequency, as well as some other low frequencies coming from unsteady flow states. Compared with guide vanes fixed openin g process, the flow states are more unstable and complicated under guide vanes moving process, also the amplitude of main frequencies becomes higher. And faster guide vanes move, more complicated the flow states are, higher the amplitude of low frequencies is. Compared with uniform motion and uniform accelerated motion, flow states are more stable and the amplitude of pressure fluctuation is lower when guide vanes move in the way of segmented motion. The amplitude of pressure fluctuation in vaneless region is higher than any other components of pump turbine, and because of runner rotation, it’s easier to propagate downstream for vaneless region pressure fluctuation in pump mode.