Investigation of the effect of combustor swirl flow on turbine vane full coverage film cooling

Abstract

In response to the challenges posed by aviation engine energy consumption and the imperative to reduce NOx emissions, modern advanced aviation engines have increasingly embraced lean-burn and swirl-stabilized combustion chambers. Consequently, the impact of residual swirl flow at the combustion chamber exit on heat transfer to turbine blades has gained prominence. This study delves into the cooling characteristics and variations under swirling inlet conditions, employing both pressure-sensitive paint (PSP) experiments and numerical simulations. The experiments measured film cooling effectiveness (η) on full film cooling blades across different levels of swirl inflow, while numerical simulations dissected flow patterns under swirling and uniform inflow conditions. The results reveal that the extent of film migration does not exhibit a direct proportionality to the level of swirl intensity. Under low swirl conditions (SN = 0.3), film migration is subtle, resulting in a maximum area-averaged η reduction of 3.0%. Conversely, under high swirl conditions (SN = 0.45), film migration becomes notably pronounced, leading to a maximum area-averaged η reduction of 11.9%. Increasing the coolant flow rate mitigates the migration characteristics, albeit with limited effectiveness. The migration of film on the blade surface of full film cooling blades is partially induced by swirling vortices but is primarily attributed to the migration of the leading edge film. Swirling inflow induces the movement of the stagnation-point line, thereby affecting the distribution of cooling air on the blade surface. Finally, this study proposes a combination of measures as an improvement strategy, including an asymmetric counterflow arrangement for the leading-edge holes, a reduction in the outflow angle of the leading-edge holes, and forward-laidback fan-shaped holes. These improvement measures are anticipated to alleviate film migration, reduce the overall uneven film distribution, and increase the average η across the blade.