Time-Averaged and Unsteady Imaging Analysis of a Reacting Fuel Jet in Vitiated Cross-Flow at Elevated Pressure

Abstract

This paper describes an experimental imaging and analysis study of a reacting CH4/H2/CO jet in a vitiated crossflow. We present an extensive data set showing the variation of the time averaged and unsteady characteristics of the reacting jet over the momentum flux ratio range of 0.75<J<240. These results show that the reaction initiates on the lee side of the jet and stands off vertically from the injector. The ratio of this standoff distance to jet exit velocity is of the same order of magnitude as the calculated ignition delay of a nonpremixed flame at the most reactive mixture fraction. In the nearfield, the time averaged trajectory of the reacting jet is quite close to the Holdeman temperature centerline for nonreacting jets. In the far-field region, the jet penetration into the crossflow exceeded the nonreacting trajectory correlation, presumably due to gas expansion effects from heat release. Analysis of the unsteady jet motions showed that the reacting jet flaps in a sinuous manner with an amplitude that increases with downstream distance. For lower J jets, J<~20, an intermittent jet attachment effect was observed, where the flame attaches to the wall for some fraction of time that decreases with downstream distance and increasing J.