Investigation on optimization of self-adaptive closure law for load rejection to a reversible pump turbine based on CFD

Abstract

Pumped storage plants (PSP) are operated under transient processes frequently in the case of the intermittent and unpredictable renewable energy. When PSPs are working in the load rejection process, the serious accident may be caused by the significant fluctuations of rotating speed and pressure. Seeking an appropriate law of guide vane movement in load rejection process is an approach to improve operating stability of PSP. This paper focuses on the optimization of self-adaptive closure law of pump turbine model for one Chinese PSP, based on sliding mesh technique and current closure law. Variations of speed and pressure are regarded as judgment functions. Meanwhile, detached eddy simulation(DES) is adopted to characterize internal flow field of pump turbine(PT) with adaptation of the optimized closure law. Not only the distribution of pressure and the turbulence kinetic energy in flow domains is analyzed details, but also the fluid evolution in passage is investigated. As a result, the optimized closure law is beneficial to impair the fluctuating rates of speed and pressure in transient process. It is illustrated that both the rotor-rotor and rotor-stator interaction in vaneless spaces are the sources of increased fluid instability in pump turbine. Note that the unstable flow regime emerges at the same moment in the inlet and outlet conduits, whereas their locations are opposite to the unit.