Abstract
Film cooling is used extensively to cool the hot surfaces and extend the life of the gas turbine's hot end components. In some modern and future engines, the average turbine inlet temperature (TIT) is increased to about 2,400K and the length of the combustor is reduced. The TIT is increased to improve the thermal efficiency while the combustor is shortened to increase the thrust-to-weight ratio. Both developments are meant to reduce the fuel and operational costs of the power plant. Increasing TIT to above 1,850K CO2 dissociation starts to compete with CO oxidation. Shortening the combustor reduces the fuel residence time and increases the likelihood of UHCs entering the turbine. When CO and UHCs enter the turbine, they could react with the cooling air, potentially increasing the blade metal temperature. An increase of about 30K can reduce the blade life by half: secondary combustion of reactive species entering the turbine section could lead to serious durability concerns. In a review of the literature, it was found that an estimated 10% of fuel energy is available for combustion in the turbine section and a maximum heat flux augmentation of 18% due to secondary combustion occurs. Secondary combustion in the turbine components is reviewed through a discussion of the analysis of reactive film cooling, developments driving the need to develop an in-depth understanding of reactive film cooling, scaling of reaction kinetics and heat release potential, performance of cooling hole geometries and configurations and mitigation strategies.
