Experimental Blowout Limits and Computational Flow Field of Axial Single and Multijet Flames

Abstract

Measurements of the lean blowout equivalence ratio (Φoverall,b) along with the numerical simulations of flame structure and dynamics of the flow field for coaxial burner configurations are reported. The burner comprises central mixture (air+liquefied petroleum gas) issuing either through six holes distributed radially each of 2mm diameter or through a circular single port of area equal to the total areas of the six holes. A bluff-body stabilizer is attached to provide recirculation of the coaxial air surrounding the central flame. The study covers the effect of the central injection configuration with emphasis on the multijet on the overall lean equivalence ratio at which flame is extinguished. The dynamics of the flow field for the multiflame configurations were identified and compared with the single flame, using the generalized finite-rate chemistry model of FLUENT 6.2 with the detailed chemical reaction mechanism defined by GRI-MECH 3.0 and other mechanisms for the higher carbon species. The computed flow field of the multijet flame provides an extra intermediate vortex in addition to the two counter-rotating vortices observed for cases of the single central stream configuration. Such a vortex is believed to enhance the stability characteristics for all the test flames in the form of reduced experimental Φoverall,b-values.