Heat transfer measurement near endwall region of first stage gas turbine nozzle having platform misalignment at combustor-turbine interface

The effect of a misalignment between vane endwall and combustor exit in a gas turbine was investigated using a Computational Fluid Dynamics (CFD) simulation and experimental measurements. The misaligned endwall platform was simulated as a backward facing step in this study. The CFD simulation predicted two legs of the vortex, referred to as a step-induced vortex, created by the step flowing through nozzle passage. Heat transfer measurements demonstrated the effect of the step-induced vortex on the endwall and the vane surface indicated by locally increased heat transfer coefficients which corresponded to the locus of the vortex, as also predicted by the simulation. Although a boundary layer transition occurred early, the locally increased heat transfer persisted to the vane trailing edge. In summary, a misaligned endwall platform causes negative effects on the gas turbine with respect to the thermal design. A vortex was generated by the step, which caused a higher thermal load on the nozzle vane surfaces, especially near the endwall.