Abstract

Migration of inlet hot streaks and the clocking effects are investigated by three-dimensional unsteady numerical simulations in a 1-1/2 turbine stage. Two hot streak circumferential positions with respect to first-stage stator, passage centered and vane centered, are simulated. Results indicate that hot streaks tend to accumulate on rotor blade pressure side and move towards shroud, causing hot spots on these parts. Separation of hot and cold fluid is observed in rotor, thus influence of hot streaks spreads to second-stage stator. Hot streaks are broken into fragments by rotor blade wakes and rotor-stator interactions in second-stage stator. Impinging hot streaks on first-stage stator passages results in separation of hot and cold lats longer in rotor, but area-averaged temperature at rotor outlet is relatively lower. Hot streaks keep a higher temperature through rotor, yet area-averaged temperature has a quicker drop in second-stage stator. Impinging hot streaks on first-stage stator vanes brings a more uniform temperature distribution at rotor and turbine outlet while a higher area-averaged temperature at the same time. Hot streaks adhere to the first-stage stator vane surfaces and move towards hub due to tip leakage, causing extra heating to these parts compared with passage centered hot streaks. Rortex, as a new way to identify vortexes in fluid, is employed to understand how vortexes contribute to migration and dissipation of hot streaks. Also, Proper Orthogonal Decomposition analysis is applied to identify flow features that impact migration and dissipation of hot streaks, and a few connections between the flow features and POD modes are made.

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