Bunsen Flame Blow-Off: Velocity-Matching Method

The effect of the incoming velocity on the anchoring point of a Bunsen flame is studied by theoretical analysis and experiments, since the anchoring point is essential to the flame holding. In order to predict the locations of the anchoring point, the velocity-matching (VM) method, which compares the profile of the flow velocity of the cold flow with that of the flame speed near the exit of a Bunsen burner, is employed together with the consideration of the cold wall quenching. The anchoring point is predicted to be located at x = Cx1u0 + Cqdq0u01/2+ Cx2dq0y = −Cy1SL01/2u0−1 + Cy2SL0u0−2+ Cy3SL01/2u0−2 + Cy4. The experiment on the variation of the anchoring point with the incoming gas velocity is done with a laminar premixed methane-air flame. The equivalence ratios of the pre-mixture are 1.0, 0.9, and 0.8, respectively, and the incoming velocity is less than 2.00 m/s in the experiment. The results show that the anchoring point moves downstream and towards instead of away from the centerline of the jet as estimated by Bernard Lewis with increasing incoming gas velocity. The prediction of the locations of the anchoring point by VM method agrees well with the experiment within the uncertainty of less than ±20%.Copyright © 2011 by ASME