Hydrocarbon flame inhibition by C6F12O (Novec 1230): Unstretched burning velocity measurements and predictions

This study experimentally and numerically determined the unstretched laminar burning velocity of premixed CH4-air and C3H8-air flames with added C6F12O (Novec 1230). High-speed shadowgraphy of spherically expanding flames provided the burning velocity as a function of stretch, which was extrapolated to zero-stretch conditions using non-linear methods. Unstretched burning velocities predicted using a recently assembled kinetic mechanism were generally in good agreement with the measurements, but tended to have poorer agreement for highly-inhibited very lean flames. To benchmark the performance of C6F12O, measured burning velocities were compared to previously measured burning velocities of premixed flames inhibited by CF3Br (Halon 1301). The two agents provided similar reductions in the burning velocity of rich flames, whereas CF3Br provided greater reductions when added to stoichiometric and lean flames. Lastly, experiments and simulations showed the influence of water vapor on the burning velocity of lean C3H8-air flames with added C6F12O. The presence of water vapor in the oxidizer increased the burning velocity by up to 23% when the fluorine to hydrogen ratio of the reactant mixture was greater than unity.