Measurements of NO in turbulent non-premixed flames stabilized on a bluff body

Spontaneous, single-point measurements of nitric oxide, NO, are made jointly with temperature, OH, and the major species using the Raman/Rayleigh/LIF technique. Turbulent non-premixed flames stabilized on a bluff body are studied with fuels ranging from simple H-2/CO to complex H-2/CH4 and gaseous methanol. The fuel jet velocity is varied to investigate the Damkohler number effects on the formation of NO. Data are presented for different axial and radial locations along the full length of most flames. It is found that the NO is generated either in the recirculation zone or further downstream of the neck zone. When the stoichiometric contour lies within the outer vortex, NO is produced mainly within the recirculation zone. Within the neck zone of the flame, the NO index levels are either constant or decreasing. This is due to the lower production of NO and the higher contribution of the consumption mechanisms such as NO reburn to N-2. The overall NO emission level in flames of CH3OH fuel is about a quarter of that measured in H-2/CO and H-2/CH4 flames.