Experiments concerning the mechanism of flame blowoff from bluff bodies

The general problem of flame stabilization on bluff objects centers about the determination of the maximum stream velocity at which stable combustion may be achieved for various flame holder geometries, gas mixtures and conditions of the approaching combustible stream. Since the process involves both gas dynamic problems and chemical kinetic problems of great complexity, the most reasonable approach is one of similarity, that is, to determine under what conditions the behavior of one flame holder is similar to the behavior of another one. Because a very large number of physical and chemical variables is involved in a combustion problem, similarity conditions can be formulated most easily after experimental investigations have indicated which parameters or groups exert little influence on the mechanism and hence may be neglected. The experiments described in this paper were conducted with the object of clarifying the role of the more important parameters in the flame holding mechanism. The results indicate that a relatively simple formulation of the similarity conditions may be obtained in which the fluid mechanical parameters and chemical parameters are effectively separated