Combined experimental and numerical study of ethanol laminar flame extinction

Extinction strain rates of ethanol at atmospheric pressure were investigated in laminar counter-flow diffusion flames as a function of nitrogen dilution through both experiment and two-dimensional axisymmetric full domain numerical analysis. An opposed-jet burner configuration with straight-tube fuel and air nozzles and having two different design nozzle exit flow profiles was used in the experiments. An advanced numerical solution algorithm, which makes use of a block-based parallel implicit finite-volume scheme, was used to obtain the corresponding simulation results. A comparison of the numerical results for two different chemical kinetic mechanisms helped to identify key factors affecting the flame extinction. While the predicted values over estimated the experimentally observed global strain rate extinction limits, the general trends and nozzle flow profiles were well captured. The local strain rates near extinction were also examined numerically and shown to be independent of the nozzle velocity flow profile and a fundamental property of the reactants. The experimental data from the present study were also compared to previous measurements and good agreement was demonstrated. The predicted nozzle exit and axial velocity flow profiles arising from the two-dimensional analysis were examined and limitations of conventional one-dimensional counter-flow analyses were highlighted.