Combustor-turbine misalignment commonly exists due to manufacturing tolerances and thermal transients. This study experimentally investigated the effect of the combustor-turbine misalignment on the heat transfer for a contoured endwall with a purge cooling scheme utilized in a land-based gas turbine engine at transonic conditions. Tests were conducted at engine-representative freestream exit Mach number of 0.85, exit Re of 1.5×10\^6 , inlet turbulence intensity of 16%, film cooling blowing ratio of 2.5 and 3.5, and density ratio of 1.95. Three different step misalignments, combustor exit being 4.86% span length higher than turbine inlet (backward-facing), no step (baseline), and combustor exit being 4.86% span length lower than turbine inlet (forward-facing), were tested to demonstrate the misalignment effect on the Nusslet number, film cooling effectiveness, and net heat flux reduction.  
Experimental results showed that with a backward-facing step, the step-induced cavity vortex led to more turbulent mixing between the coolant and freestream, thus reducing the coolant coverage area and adversely affected the cooling performance. This negative impact was more severe at a blowing ratio of 2.5 compared to 3.5. The forward-facing step induced more jet liftoff and shifted the coolant coverage downstream and closer to the pressure side. At a blowing ratio of 2.5, the step slightly enhanced the cooling performance, while at blowing ratio 3.5, it had no significant influence on the coolant. Based on this study, it is suggested that a backward-facing step be avoided as much as possible to prevent endwall burning in the nozzle guide vane when considering engine design decisions. 


Experimental Study of the Endwall Heat Transfer of a Transonic Nozzle Guide Vane With Upstream Jet Purge Cooling: Part 2  \u2014 Effect of Combustor-NGV Misalignment

Division / Sponsor:
International Gas Turbine Institute (IGTI)

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

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