Flame Dynamics of a reactive spray in vitiated crossflow*

This work investigates experimentally and numerically the effect of the air-to-liquid massflow ratio (ALR) on the topology of a Jet A-1 airblast spray flame. The spray is injected transversely into a turbulent vitiated crossflow composed of products of a lean natural gas flame. The spray flame thermal power is varied between 2.5 and 5 kW and the ALR between 2 and 6. The reaction zone is characterized using OH* chemiluminescence and OH and fuel planar laser induced fluorescence. The Large Eddy Simulations of the multiphase reactive flow agree closely with the experiments. Our study shows a substantial effect of the ALR on the mean flame topology and dynamics due to its influence on flow field and spray characteristics. A low ALR results in a relatively small jet to crossflow momentum ratio (J) and a large spray Sauter mean diameter (SMD). A thick windward reaction region is formed due to poor mixing between the fuel spray and the crossflow. Meanwhile, the correspondingly high spray SMD leads to isolated penetration and combustion of bigger droplets. At high ALR, the reaction fronts are more homogeneous and distributed as a result of the efficient entrainment-induced mixing on the leeward side caused by the high J and the faster droplets evaporation due to the lower spray SMD.