Stabilization of premixed flames on rotating Bunsen burners

The effect of rotation on stabilization of methane-air premixed Bunsen flames is experimentally investigated. Both the flame blowoff and flashback contours are determined in the fuel mole fraction versus Reynolds number plane (X_F-Re) with the rotational Reynolds number Re_r as a parameter. It is found that rotation of the gas increases the flame stabilization area A_s = A_B - A_F defined as the difference between the flame blowoff A_B and flashback A_F areas in the (X_F-Re) plane. The flame stabilization efficiency is defined as η_s = 1 - A_F/A_B that approaches unity in either A_B → ∞ or A_F → 0 limit. The experimental results suggest that rotation decreases the flame stabilization efficiency. However, rotation is found to substantially increase the flame stabilization coefficient defined as β_s = A_s/A_st, where A_st is the stabilization area of the standard nonrotating burner. The parameters η_s and β_s may be useful in combustion technology for quantitative evaluation of the stabilization performance of different types of flame holders. In addition, the local hydrodynamics near the center of rotating Bunsen burner is simulated by investigating stabilization of planar laminar premixed flames on rotating porous disks with uniform surface velocity. Physical concepts concerning mechanisms of flame stabilization are discussed in terms of three important parameters namely the translational Reynolds number Re, the rotation Reynolds number Re_r, and the fuel mole fraction X_F. The results of the experimental findings are shown to be in accordance with prior theoretical investigation.