Effect of the nozzle structure on the flame stability and OH* chemiluminescence of CH4/O2 inverse diffusion impinging flame

In the present study, the stability of CH4/ O2 inverse diffusion impinging flame is studied using OH* chemiluminescence diagnosis. The effects of different nozzle incidence angles and the impinging distance (H) on the stability of impinging flame and OH* chemiluminescence are investigated. The obtained results show that the flame root of the 45 degrees nozzle breaks and makes noise near the blowout, the lift-off limit has a linear correlation with the impinging distance. It is found that the 90 degrees nozzle has the maximum lift-off limit, the 45 degrees nozzle has the maximum blowout limit. When the impinging distance is more than 20 mm, the lift-off state does not occur for the 60 degrees nozzle. The flame is in the attachment state, the OH* chemiluminescence of the three nozzles enhances as the oxygen flow rate (uO2) increases. The radial distribution of OH* radicals shows that the peak intensity of the flame decreases with decreasing nozzle incidence angle. The position of the core area of 45 degrees and 60 degrees nozzles increases with the increase of oxygen flow rate. Meanwhile, the position of the reaction core area of the 90 degrees nozzle increases with the oxygen flow rate in the attachment state and decreases monotonically in the lift-off state.