Flowfield measurements and flame stabilization of a premixed reacting jet in vitiated crossflow

Flow field characteristics and flame stabilization behavior are studied experimentally for a premixed ethylene-air jet injected into a vitiated hot crossflow composed of products of fuel lean combustion. The jet was injected perpendicular to the crossflow in a rectangular duct with jet-to-crossflow momentum flux ratios (J) ranging from 5 to 23. High speed chemiluminescence imaging was used to capture unsteady and average behavior of the reacting jet in cross flow (JICF). Time resolved particle image velocimetry measurements were taken to characterize the flow field of non-reacting and reacting jets injected into the vitiated crossflow. Power law correlations for non-reacting JICF trajectory from the literature were found to over-predict the ex perimental non-reacting jet trajectories due to the greater degree of confinement present in the experimental configuration compared to previous studies. New jet trajectory correlations were developed, to fit the experimental non-reacting and reacting trajectory data, including the effects of confinement. In the case of reacting JICF, the flame was found to have two separate stabilization points, one on either side of the jet centerline. The windward flame stabilization was characterized by three distinct behaviors: complete flame attachment, an unsteady lifted flame, and windward blowoff. The average windward flame edge was lifted for all momentum ratios tested and the liftoff height showed strong dependence on J. The leeward flame consistently stabilized above the jet exit. Experimental strain rates, flame propagation speeds, and ignition delay times were found at the instantaneous flame stabilization locations. Consistencies between strain rate and ignition delay time at the windward flame edge for varying J suggest auto-ignition dominated flame stabilization behavior. (C) 2015 The Combustion Institute. Published by Elsevier Inc. All rights reserved.