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 Damköhler 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.

预先混合的乙烯-空气射流喷射到热燃烧产物的横流中的点火和火焰剥离高度特征经过实验研究。发现火焰的迎风边缘从喷嘴出口抬起，而下风侧几乎总是位于喷嘴出口附近。迎风火焰抬升高度的特征是射流与横流的动量比，射流当量比和射流混合物温度的函数。已经发现，迎风火焰升起高度与基于反应性最高的化学成分的化学自燃时间尺度定义的Damköhler数最佳相关。为了分析射流的非反应部分和横流之间的混合，进行了平面激光瑞利光散射测量以成像该区域中的温度场。根据瑞利数据确定射流与错流之间的混合，以表征射流与火焰上升位置上游的错流之间的混合特性。根据瑞利数据计算标量耗散，并确定与标量耗散相关的时间标度。实验结果表明，在本文研究的条件下，火焰稳定取决于喷射混合物的自燃特性。