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

Abstract

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° 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° nozzle has the maximum lift-off limit, the 45° 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° 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° and 60° nozzles increases with the increase of oxygen flow rate. Meanwhile, the position of the reaction core area of the 90° nozzle increases with the oxygen flow rate in the attachment state and decreases monotonically in the lift-off state.