Experimental and Numerical Investigation of Structure and Extinction Limits of Biofuels in Laminar Counterflow Diffusion Flames

Extinction of laminar counterflow diffusion flames were investigated at atmospheric pressures as a function of nitrogen dilution through experiment and two-dimensional axisymmetric full domain numerical analysis. An opposed-jet burner with two flow configurations was used in experiments and an advanced, state-of-the-art, high-fidelity, solution algorithm was used to obtain the numerical results.;A comprehensive investigation of flame extinction process was conducted. Nozzle velocity flow distributions and burner geometry were found to influence global extinction strain rate significantly, whereas effects of radiative heat loss and gravity were minimal. The local strain rate at extinction was shown to be a fundamental property of the fuel. Chemical kinetic mechanisms best suited for extinction limit calculations were also identified.;Using these insights, gaseous biofuels and ethanol extinction were studied. The numerical prediction of gaseous biofuels agreed well with experimental results. However, over-predictions were observed for ethanol, likely caused by limitations of available chemical kinetic mechanisms.