Blade loading fluctuation investigation of LP final stage in steam turbine

Numerical simulation on the unsteady flow in the final two stages of a full speed steam turbine LP cylinder, with rotor blade height being 1200 mm, is carried out. Full channels domain and sliding grid method are used in the computation. Unsteady variation and blade aerodynamic loading fluctuation behaviors of the turbine stages are investigated. Unsteady disturbances and their influences on the upstream and downstream unsteadiness are also investigated using FFT method. Results show that for the long blade turbine stage investigated, along spanwise, unsteady blade loading fluctuation increases in stator and decreases in rotor. Meanwhile, pressure distortion along circumferential direction induced by trailing edge shock of upstream blade row is the dominant one among all the disturbance sources.