Heat Transfer in Reacting Cooling Films: Influence and Validation of Combustion Modeling in Numerical Simulations

Abstract

The demand for increased performance and lower weight of gas turbines gives rise to higher fuel-to-air ratios and a more compact design of the combustion chamber, thereby increasing the potential of fuel escaping unburnt from the combustor. Chemical reactions are likely to occur when the coolant air, used to protect the turbine blades, interacts with the unreacted fuel. Within this work, Reynolds-averaged Navier–Stokes (RANS) simulations of reacting cooling films exposed to high temperature fuel-rich exhaust gases are performed using the commercial computational fluid dynamics (CFD) code ansys fluent and validated against experimental results obtained at the Air Force Research Laboratory in Ohio. The results underline that the choice of the turbulence model has a significant impact on the evolution of the flow field and the mixing effectiveness. The flamelet as well as the equilibrium combustion model is able to predict an adequate distance of the reaction zone normal to the wall. Its thickness, however, is still much smaller and its onset too far upstream as compared to the experimental results. According to the present analysis, the flamelet combustion model applied along with k–ω shear stress transport (SST) or k–ε turbulence model turned out to be an appropriate choice in order to model near wall reacting flows with reasonable prospect of success.