Numerical Studies on Flames Established in Reacting Film-Cooling Experiment
Integration of turbine turning vanes into a combustor is needed for the development of ultra-compact combustors. A viable approach for protecting the combustor from the high-temperature fuel-rich environment is to inject air through the holes drilled on surfaces. However, it is possible that air intended to cooling may react with the fuel rich combustion products and increase the heat flux. Air Force Research Laboratory has initiated several experimental/numerical studies for investigating the flames that might develop between the injected air and fuel-rich flows in the combustor and their impact on film cooling. A time-dependent, detailed-chemistry computational-fluid-dynamics model is used in the present study for understanding the flames formed in reacting film cooling. Combustion of propane fuel with air is modeled using a chemical-kinetics mechanism involving 52 species and 544 reactions. Both laminar and turbulent flow simulations are performed. Effects of blowing ratio, equivalence ratio and sidewall cooling are investigated. Simulations have reproduced various flame characteristics observed in the experiments. Numerical results are used for explaining the non-intuitive shift in flame anchoring location to the changes in blowing ratio and equivalence ratio. The higher diffusive mass transfer rate of hydrogen in comparison to the local heat transport enhances cooling of cross-flow combustion products, which, in turn, affects the autoignition process. While increasing the blowing ratio abates the differences resulting from non-equal mass and heat transport rates, higher concentrations of hydrogen in the fuel-rich cross-flows accelerate those differences.