Flame stability of rod stabilised premixed butane/air flames

Regions of flame stability were obtained experimentally for a premixed butane/air flame stabilised by an axially mounted solid rod for low Reynolds numbers (Re<3600). Equivalence ratios ranging from 0.4 to 3.0 were applied in the present study. There were two non-dimensional parameters proposed to represent the variation of geometrical configurations: rod protrusion BR(0-2) and rod to tube ratio BT(0.51-0.8). Inverted, partially inverted and regular (Bunsen) flames were fundamental flame types identified across the stable regions. Inter-regions wore characterised by the existence of more than one stable flame type, primarily depending on the axial and radial distances of the ignition source from the burner port. The size of the unstable region extended with increasing BR, and the effect of BTshowed a similar trend. The use of rod of smaller diameter extended the flashback region, whereas blow-off limits were less dependent on these geometrical parameters. The rod stabilised method enabled the premixed flame to operate with a very fuel lean mixture.