Using a profiled endwall is an effective method to reduce secondary losses in axial turbines. This approach has been widely investigated in the past decade on many real engines. Much of the previous analysis, however, was conducted in a steady state, with mixing plane conditions where the effects of unsteady interaction between inter-blade rows could not be taken into account. Since a profiled endwall has notable influences on the secondary flow and trailing shed vorticity, it is unavoidable that the profiled endwall may also alter the unsteady flow field. Previously, we executed an optimization procedure  to design profiled endwalls for a one-and-half stage, high work axial turbine. Steady state results indicate an improvement in stage efficiency due to profiled endwalls on both the stator one and rotor one. In this work, the effects of profiled endwalls on the turbine unsteady flow features have been analyzed by conducting unsteady simulations. Numerical results indicate that profiled endwalls on the upstream stator not only reduce the secondary loss and trailing edge shed vorticity of the stator, but also reduce the secondary losses of the downstream rotor by affecting the development of the passage vortex. However, a profiled endwall on a rotor has nearly no influence on the upstream stator performance. Transient results indicate that with the profiled endwalls of S1, the periodic fluctuations of flow fields are reduced, due to a weaker stator/rotor unsteady interaction. With profiled endwall of R1, the fluctuations of a flow fields become stronger over time, which means a profiled endwall of R1 can introduce significant unsteady effects to the turbine. Unsteady effects of profiled endwalls will be experimentally confirmed before this design is applied to a real turbine.
Unsteady Effects of Profiled Endwalls on a 1.5 Stage Axial Turbine
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Tang, H, Liu, S, Luo, H, & Hou, W. "Unsteady Effects of Profiled Endwalls on a 1.5 Stage Axial Turbine." Proceedings of the ASME Turbo Expo 2015: Turbine Technical Conference and Exposition. Volume 2A: Turbomachinery. Montreal, Quebec, Canada. June 15–19, 2015. V02AT38A040. ASME. https://doi.org/10.1115/GT2015-43871
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