Recent studies on flame stabilization of premixed turbulent gases

FLAME stabilization is of importance in the practical design of ramjets and afterburners. It has been studied extensively in recent years, particularly with reference to bluff-body flame-holders. In the present survey we describe the investigations relating to flame holding by bluff bodies as well as new techniques (e.g.,. flame holding by the use of reverse jets) which may prove to be of practical importance in new engine configurations. In Section II we consider the flow field downstream of a bluff-body flame-holder which includes the recirculation zone behind the body and a region of flame spreading farther downstream. Explicit reference is made to crucial experiments which illustrate the nature and magnitude of the velocity field, the physical extent, the temperature, and the gas composition of the recirculation zone. Experimental studies and theoretical predictions of the angle of flame spreading, as well as some observations on unstable flow and the onset of blowoff, will be reviewed. The variation of blowoff velocity with flame-holder design, pressure, and mixture composition is considered briefly in Section III both for single and for adjacent bluff bodies. Also included is a summary of results for blowoff velocities obtained with a reverse-jet flame-holder and with wall recesses. Theoretical studies on the mechanism of flame stabilization form the subject of Section IV. We shall indicate the points on which various proposed models agree and disagree with experiment and attempt to formulate a composite description which is consistent with most of the currently available experimental data both for bluff-body and for reverse-jet flameholders.