Effect of ozone on the propagation speed of a tribrachial flame in laminar non-premixed jets

Although there have been studies on ozone enhancement to flame stabilization and flame propagation, there still lacks systematic information of ozone enhancement on tribrachical flame propagation. Due to its intrinsic importance on flame stabilization, the study is to experimentally investigate the addition of ozone to the propagation characteristics of a tribrachial flame in a laminar co-flow jet. A coaxial dielectric-barrier discharge is employed to produce ozone with a concentration up to 2850 ppm. It is shown that the flame displacement speed and thus the flame propagation speed are enhanced with ozone addition, resulting in a decrease in the flame lift-off height. The propagation speed of flames with ozone is also observed to increase in the near-nozzle region. This is probably associated with more sensitivity of off-stoichiometric flames to ozone. Both of the flame lift-off and reattachment velocities are enhanced with ozone for approximately 11.5% and 9.2%, respectively. The slightly larger enhancement for flame lift-off velocity than reattachment velocity is consistent with the normalized flame displacement speed during lift-off and reattachment processes.