The Calculation of the Structure of Laminar Counterflow Diffusion Flames Using a Global Reaction Mechanism

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Abstract
—Counterflow diffusion flames burning undiluted and diluted methane-air and propane-air mixtures have been computed using global reaction schemes involving only major species. Agreement for the undiluted methane-air and propane-air flames has been found to be excellent and realistic variations of species profiles with increasing rates of strain are obtained. Computations of diluted methane-air flames at different rates of strain confirm the experimental findings that the critical parameter determining name extinction is the maximum reaction zone temperature, which is found to be in acceptable agreement with measurements. The critical fuel concentration at the limit of low strain for the case of fuel diluted with nitrogen is also in acceptable agreement with measurements. Effects of varying degrees of approximation of transport properties is also investigated, including the common approximation of unity Lewis numbers. Implications of the results as regards to the inclusion of direct kinetic effects into turbulent computations and to the generation of laminar flamelets are also discussed.