The mixing and subsequent combustion within turbulent reacting shear layers is examined. To conduct this study, a computer program has been written to solve the axisymmetric Reynolds-averaged, Navier-Stokes equations. Turbulence is modeled using three algebraic turbulence models, and the chemical kinetics is modeled using a seven-species, seven-reaction, finite-rate chemistry model. Three separate flowfields are investigated. The effect of turbulent mixing upon the extent of combustion is demonstrated. No single turbulence model considered accurately predicted the degree of mixing for all three cases.
Work has been underway for a number of years at the NASA Langley ResearchCenter to develop a supersonic combustion ramjet or scramjet that is capable of propelling a vehicle at hypersonic speeds in the atmosphere or beyond. A recent part of that research has been directed toward the optimization of the scramjet combustor, and in particular the efficiency of fuel-air mixing and reaction in the engine. A supersonic, spatially developing and reacting mixing layer serves as an excellent physical model for the mixing and reaction processes that take place in a scramjet combustor. This paper describes a study of fuel-air mixing and reaction in a supersonic mixing layer and discusses several techniques that were applied for enhancing the mixing processes and the overall combustion efficiency in the layer. Based on the results of this study, an alternate fuel injector configuration was computationally designed, and that configuration significantly increased the amount of fuel-air mixing and combustion over a given combustor length that was achieved.
A supersonic coaxial jet facility has been designed to provide experimental data suitable for the validation of CFD codes used to analyze high-speed propulsion flows. The center jet is of a light gas and the coflow jet is of air, and the mixing layer between them is compressible. Various methods have been employed in characterizing the jet flow field, including schlieren visualization, pitot, total temperature and gas sampling probe surveying, and RELIEF velocimetry. A NavierStokes code has been used to calculate the nozzle flow field and the results compared to the experiment.
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