Effect of swirl and hot streak on unsteady thermal performances of film-cooled high pressure turbine rotor

Advanced aero-engines widely employ lean-burn combustors to comply with strict NOx emission regulations. Lean-burn combustor exit condition is characterized with swirl and hot streak (HS). Current work presents an unsteady numerical simulation on the film-cooled high pressure (HP) turbine stage subjected to HS and swirl. The combined effect of HS and swirl on unsteady thermal behaviors of film-cooled turbine rotor blade was examined. Results indicate that swirl’s induced incidence angle effect drives the radial migration of HS and film coolant inside nozzle guide vane (NGV) passage. Similar radial migration continues inside rotor passage, attributed to the unsteady vortex interactions among horseshoe vortex, swirl-induced vortices and residual swirl. Although swirl-driven radial migration of hot and cold fluids redistributes the heat load on uncooled rotor blade, film cooling effect markedly mitigates these variations. As for film cooling performance, blade-row interaction causes the periodic variations in rotor incidence angle, drives some film coolant intended for pressure side (PS) leading edge (LE) to flip toward suction side (SS) LE, or vice versa and consequently results in transient fluctuations in the film cooling effectiveness within rotor blade LE. Swirl reinforces that transient fluctuations, however, swirl exhibits limited effect on the time-averaged film cooling performance of rotor blade. The locally enhanced film cooling effectiveness on rotor PS is resulting from the reversed radial migration of cold and hot fluids induced by swirl, while on SS, inherent horseshoe vortex dominates, therefore, the film cooling effectiveness on that surface merely shows slight variation. Horseshoe vortex within rotor passage.