Stabilization Mechanism of Turbulent Wake Flame Behind Bluff Bodies with Fuel Injection : 1st Report, Blow-off Limits

Stability of wake flames formed behind a bluff-body with fuel injection was investigated experimentally in various geometries of two-dimensional bluff-bodies such as cylinders with 10-20mm diameters, hemi-circle, 60°wedge and rectangular rods of 12.5mm width. The bluff-body was located in an air stream flowing 5-60m/s. Fuels used were propane, methane, ethylene and butane. Flame stability limits, length or geometry of recirculation zone, distribution of chemical species concentrations, temperature and equivalence ratio in the zone were measured. The results show that the equivalence ratio in the recirculation zone is important in determining the flame limit. The air velocity at blow-off is inversely proportional to the square root of the bluff-body width, and is independent of the direction of fuel injection and the geometry of flame holder except for the rectangular rod.