Analysis of flow characteristics in pumped storage unit during start-up in turbine mode

During the start-up, the unit enters into speed-no-load from static state. The runner is full of complex vortex, which hinders the water flow into the runner, and even leads to the failure of starting up. It is necessary to study the vortex and flow state to evaluate the stability of start-up. In this paper, the coupling method of one-dimensional pipeline system and three-dimensional flow inside the unit is used to simulate the startup process and analyse the three-dimensional flow state in runner. The flow instability during the start-up process is deeply studied by analysing the pressure distribution, streamline and turbulent kinetic energy. The results show that the turbulence intensity in the runner decreases with the increase of discharge. During start-up, the vortices in the runner occupy the whole blade passage, and then disappear. With the decrease of discharge, the turbulent kinetic energy at the runner inlet rises and small vortex appears at runner inlet.