This paper numerically performs a detailed unsteady analysis of flow and heat transfer characters in a 1-1/2 stage turbine with artificial hot streaks being introduced at the computation domain inlet. Both uniform boundary condition and hot streak boundary conditions are specified at the domain inlet. The inlet hot streaks, centre points of which align with turbine midspan for both hot streak cases, are round shape with a diameter of 20% span. Unsteady numerical simulations are carried out with hot streaks at two different circumferential positions, where hot streaks impinge on all first-stage stator leading edges and where hot streaks impinge on all first-stage stator mid-passages. This paper provides insight into the general phenomena exist in hot streak migration process in the turbine stage at first. Hot and cold fluid would segregate from each other, and hot streaks tend to accumulate on the first-stage rotor blade pressure side. The results also show that inlet hot streaks interact with first-stage stator wake, and that impacts of inlet hot streak can extend to the second-stage stator. The influence of rotor blade passing frequency on hot streak development is also considered. The effect of hot streaks on the extent of secondary flow in first-stage rotor is studied. Physical mechanisms that control the migration and development of hot streaks in turbine stage are discussed, and comparations between the results of two hot streak cases are conducted. When hot streaks impinge on first-stage stator leading edges, they dissipate more quickly, for they are cut into pieces by the blades, and are more influenced by rotor-stator blades interaction, which lead to a more uniform temperature distribution at second-stage stator exit consequently. When hot streaks impinge on the first-stage stator mid-passages, they keep relative integrality passing through turbine stage which leads to partial hot spot areas at first-stage rotor exit and second-stage stator exit, and hot streaks don’t move towards turbine hub like the other case does. Both unsteady temperature fluctuations in terms of maximum and minimum values and time-averaged temperature are examined to demonstrate blade temperature distribution, and to determine the resident time of hot streaks on turbine blades. Differences of blade temperature distribution bringing by hot streak clocking are studied. Proper Orthogonal Decomposition (POD) method is applied on unsteady numerical simulations data. The dominant modes are linked to the migration of hot streak through turbine stage. The variation of POD modes with different inlet hot streak circumferential positions characterize the disparities of the migration process. The application of ‘Rortex’ method identifies how the vortices in the turbine stage impacts the development of inlet hot streaks.


Unsteady Analysis of Inlet Hot Streaks Clocking Effects in a 1-1/2 Turbine Stage

Division / Sponsor:
International Gas Turbine Institute (IGTI)

Paper Proceedings: https://asmedigitalcollection.asme.org/GT/GT2020/volume/84058

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