Stabilization in turbulent lifted deflected-jet flames

Abstract

The stabilization region of two turbulent lifted deflected-jet flames injected at 45° into a cross-flow is investigated. The two flames with the same jet Reynolds number ( Re d =6000), but with different crossflow speeds ( U cr =1.8 and 3.0 m/s), are compared to understand the stabilization mechanism of such jet flames. The flame base location and the velocity field at the flame base are obtained simultaneously by CH planar laser-induced fluorescence and particle image velocimetry. The deflected-jet flame with a higher cross-flow speed is observed to have lower liftoff height and generally be more stable when compared to the deflected-jet flame with a lower cross-flow speed, unlike the case of jet flames in coflow where the opposite has been observed. Instantaneous flame base locations scatter around the mean stoichiometric velocity contour, which is the theoretical velocity of the flame surface. Therefore, the flame base of the deflected-jet flame with the lower corss-flow speed is exposed to higher incoming velocity and shows wider CH distribution. These observations are consistent with the idea that the velocity at the flame base is proportional to the stoichiometric velocity and that the increase of the velocity at the flame base beyond the leading edge flame propagation speed leads to blowout.