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Experimental study of flame-hole reignition mechanisms in a turbulent non-premixed jet flame using sustained multi-kHz PIV and crossed-plane OH PLIF

2010; Elsevier BV; Volume: 33; Issue: 1 Linguagem: Inglês

10.1016/j.proci.2010.06.134

1873-2704

Adam M. Steinberg, Isaac Boxx, Christoph M. Arndt, Jonathan H. Frank, Wolfgang Meier,

Fire dynamics and safety research

The dynamics of flame-hole reignition were studied experimentally in a turbulent non-premixed CH4/H2/N2 jet flame at Red=22,800 (flame 'DLR-B' from the TNF workshop). Simultaneous measurements of the OH combustion radical and velocity field were performed using planar laser induced fluorescence (PLIF) and particle image velocimetry (PIV) at a sustained rate of 10 kHz. The dynamics of the reignition process were tracked through time and two reignition mechanisms were identified. Particular care was taken to reduce the influence of out-of-plane motion on the analyzed events by simultaneously measuring the OH distribution in crossed planes. Flame-holes reignited due to both edge-flame propagation and turbulent transport of burning flame segments. However, the edge-flame propagation mechanism was dominant and accounted for over 90% of the flame-hole reignition rate on average. Furthermore, the presence of large scale turbulent structures adjacent to a flame-hole did not necessarily result in reignition due to turbulent transport. Instead, the edge-flames propagated around the perimeter of such structures, indicating intervening regions of well mixed gas. The range of measured edge-flame propagation speeds agreed well that of highly-preheated premixed flames, with a mode of approximately 4 m/s and a mean of approximately 7 m/s.