Research on three dimensional viscous unsteady flow and excitation force of turbine stage

Aimed at the effect of unsteady flow on turbine aerodynamic characteristics and the induced excitation force causing blade vibration fatigue, the research on unsteady flow in turbomachinery, conducted domestically and abroad, was widely reviewed and summarized. RNG κ-ε turbulence model and dual time step method were described. Two examples, studied by the writers, for unsteady flow and excitation forces analysis on high pressure and last stages of two steam turbines were provided. Results show that a more detailed and accurate flow field and a more realistic efficiency can be obtained through analysis of unsteady flow field by adoption of RNG κ-ε turbulence model and dual time step method; And there exists a close relation of flow excitation force and excitation force level with the status of the flow field. When the factors affecting (such as back pressure, flow rate and clearance between nozzle and blade) change, it will impact on the flow excitation factors. At last, the ideas and methods for further studies were proposed by the writers.