Stabilization of premixed flames on rotating Bunsen burners

Abstract

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.