Ignition and flame stabilization of a premixed reacting jet in vitiated crossflow

Ignition and flame liftoff height characteristics of a premixed ethylene-air jet injected into a crossflow of hot combustion products are studied experimentally. The windward edge of the flame is found to be lifted from the nozzle exit while the leeward side is almost always located near the nozzle exit. The windward flame liftoff height is characterized as a function of jet-to-crossflow momentum ratio, jet equivalence ratio and jet mixture temperature. It is found that the windward flame liftoff height is best correlated with respect to a Damkohler number defined based on the chemical autoignition time scale for the most reactive mixture fraction. In order to analyze the mixing between the non-reacting part of the jet and the crossflow, planar laser Rayleigh light scattering measurements were conducted to image the temperature field in that region. Mixing between the jet and the crossflow was determined from the Rayleigh data to characterize the mixing characteristics between the jet and the crossflow upstream of the lifted flame location. Scalar dissipation was computed from the Rayleigh data and the time scales associated with scalar dissipation were determined. Experimental results suggest that the flame stabilization is governed by the autoignition characteristics of the jet mixture for the conditions studied in this paper. (C) 2018 The Combustion Institute. Published by Elsevier Inc. All rights reserved.