Leading-Edge Flame Fluctuations in Lifted Turbulent Flames

Abstract

Studies are presented that examine the fluctuations in liftoff height of lifted methane flames in the presence of air coflow. At a certain jet exit velocity, a flame will lift from the burner exit and stabilize at some downstream position. The partially-premixed flame front of the lifted flame oscillates in the axial direction, with the fluctuations becoming greater in flames stabilized further downstream. These fluctuations are also observed in flames where blowout is imminent. This work investigates the role of fuel velocity and air co-flow on flame fluctuations in both stable and unstable regimes. The results of video imaging of a lifted methane-air diffusion flame are presented and discussed. Images are used to ascertain the changes in the reaction zone that influence these fluctuations and relate the movement to blowout.

Keywords:

• Blowout
• Coflow
• Combustion
• Flame stability
• Methane

ACKNOWLEDGEMENTS

The research reported in this paper has been supported by the U.S. Army Research Office (Contracts W911NF0510045 and W911NF0810142).

Notes

Note. Pipe diameter (d) = 3.5 mm.