Dual-fuel characteristics of a lean azimuthal flame (LEAF) combustor

Lean azimuthal flame (LEAF) is a recently introduced novel combustion concept that aims to bring down emissionsfrom aviation [1]. Dual-fuel operations of the LEAF combustor presented in this work comprised simultaneousinjections of jet A-1 and hydrogen accompanied by opposed air crossflow. An axisymmetric combustorhouses three pairs of a straight spray flame and an inclined hydrogen flame at equidistance in circumference. Eachof these pairs is entrained by a hot vitiated flow (mixture of combustion products and opposed fresh air) such thatit ignites the next pair to maintain sequential combustion. This rapid interaction constituted a toroidal reactionzone and hence lean azimuthal flame. This study evaluated the potential of operating LEAF combustor under awide range of operating conditions. Different combustion regimes are identified by varying thermal power, changingspray properties in terms of atomization-air to liquid mass flow ratio (ALR), altering the strength of toroidalmotion with variable opposed air mass flow, and for two different chamber lengths. The stability of LEAF configurationand its transition into tubular flame is studied through simultaneous high-speed OH∗ chemiluminescenceimaging and measurement of chamber pressure fluctuation. Results of OH∗ chemiluminescence analysis showedthe topological variation of LEAF with thermal power and with chamber length. The regime of stable LEAF isidentified and explained. Moreover, the transient LEAF behavior is also captured and described in this paper.