TEMPORALLY AND SPATIALLY-RESOLVED INVESTIGATION OF FLAME PROPAGATION AND EXTINCTION IN THE VICINITY OF WALLS

Flame propagation and extinction near a solid surface have been invest igated. The flow configuration chosen was an impinging reactant jet an d the flame was stabilised around the stagnation point. An interesting phenomenon of alternative combustion modes under exactly the same col d flow condition has been observed, namely the so called ''disc-like'' and ''ring-like'' flames. The two flames can be established in a cont rolled manner dependent on how the flame was ignited. The alternative combustion modes demonstrate the complex nature of flame propagation i n the vicinity of a solid surface. Besides global observation and meas urement of flame propagation and extinction, a high speed laser sheet tomography technique has also been employed to investigate further int o the disc-like flame case studied. Detailed local flame extinction (i dentified by the reactant touching the water cooled surface) has been resolved by the high speed laser sheet tomography technique. The time resolved images also indicate that local flame extinction will not nec essary lead to global flame extinction and the extinguished part can b e reignited as long as there is enough hot product from which flame pr opagation can occur. Time resolved global flame extinction data has al so been obtained by the same technique.