EFFECT OF AN INHIBITOR ON HIGH-SPEED TURBULENT FLAMES AND THE TRANSITION TO DETONATION

The influence of an inhibitor (CF3 Br or Halon 1301) on the propagatio n of high-speed turbulent flames, quasi-detonations and the transition to detonation has been investigated for methane-air, propane-air and acetylene-air mixtures. The experiments are carried out in a 13 m tube (15 cm diameter) filled with regularly spaced orifice plates (blockag e ratio of 0.39) to ensure rapid flame acceleration. In all cases, the addition of the inhibitor reduces the turbulent flame velocity and ex tinguishes the flame with sufficient inhibitor concentration (2.7% and 7.5% for methane-air and propane-air, respectively). For acetylene-ai r mixtures, the quasi-detonation speed is progressively reduced with i ncreasing inhibitor concentration and eventually causes the failure of the quasi-detonation and transition back to a fast turbulent flame. T he inhibitor also narrows the propagation limits in all cases. To eluc idate the inhibition mechanism, detailed modelling of both the turbule nt flame structure as well as the chemical kinetics are required.