Non-premixed Lifted Flame Stabilization Coupled With Vortex Structures In A Coaxial Jet

摘要

An experiment concerning the non-premixed lifted flame stabilization studies the coupling between the flame behavior and the vortices developed in the inner mixing layer of a coaxial airlmethane jet. It completes a previous global approach in which we show that "macro parameters" (potential cores, inner jet spreading) were efficient to describe the overall lifted flame behavior. Here, the jet dynamics is locally determined in vertical and transverse planes by means of particle image velocimetry and time resolved laser tomography. A systematic identification of vortices, obtained from PIV fields, is developed from a criterion proposed by Graftieaux et al. The analysis relies on the quantification of the Kelvin-Helmholtz vortices and the secondary streamwise vortices. Local parameters characterizing the vortices are quantified as functions of the air flow rate velocity, U_o.They contribute to formulate a scenario explaining how a small change of U_o produces a great change in the flame behavior.