Abstract:The Pelton turbine is widely used in hydro-plants in mountainous areas with a normally 500 m higher water head, which results in a higher than 100 m/s velocity at the nozzle outlet. The fine sand particles contained in the high speed jet not only can wear the bucket surfaces but also damage the injection mechanism. The injection mechanism is mainly used to obtain a high quality cylinder jet and to increase the energy conversion efficiency in the runner. The needle erosion caused by sand particles can affect the jet velocity and profile and result in an extra efficiency loss. In this paper, a 3D unsteady multiphase flow in the injection mechanism is simulated. The fine sand particles are simplified into spherical solid particles. The discrete particle model is adopted to predict the flow and needle erosion characteristics. It is shown that the trajectories of particles with different diameters vary a lot, causing different erosion patterns in the injection mechanism. The small particles can follow the streamlines and cause abrasive wear on the needle tip, while the large particles had a greater inertia and impact the upstream area of the needle orifice easily.
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