Velocity measurements in neighboring lifted edge flames

Measurements that characterize the structure of edge flames with more complicated imposed composition and velocity flow fields allowing for the stabilization of multiple neighboring edge flames were presented. A burner with five 5-mm by 40-mm parallel slots was created, and several flame conditions were examined by passing through each slot a rich CH₄/air mixture with φ = l.7 (R), a lean CH₄/air mixture with φ = 0.4 (L), or nitrogen. In each case, the velocity of the flows was around 1 m/sec, which was greater than the laminar flame speed for methane. For the first case with a lean mixture and rich mixture in neighboring slots and nitrogen in the remaining three slots (NLRNN), a single fuel composition gradient was created above the burner with a single stoichiometric location. More complicated inflow composition profiles were examined by passing alternating lean or rich mixtures through three slots. This inflow produced two separate composition gradients at the base of the lifted flame with two stoichiometric locations. Thus, two separate edge flames in close proximity are established. In one case, a rich central flow surrounded by two lean flows (NLRLN) produced stoichiometric crossings ≈ 7.4 mm apart. In another case, a central lean flow surrounded by two rich flows (NRLRN) produced stoichiometric crossings ≈ 20% closer. This is an abstract of a paper presented at the 30th International Symposium on combustion (Chicago, IL 7/25-30/2004).