Characteristics of nitric oxide formation rates in turbulent nonpremixed jet flames

The formation of oxides of nitrogen, NOx, in turbulent nonpremixed flames i s experimentally analyzed making use of velocity, temperature, and major sp ecies concentration measurements in jet propane flames. The analysis consid ered the contributions of Zeldovich (thermal) and Fenimore (prompt) mechani sms at different locations of attached vertical flames with Reynolds number s of 20,400 and 37,600. The analysis of NO mass formation rates suggests th at prompt mechanism dominates NO formation throughout the flames, with peak formation rates occurring in the rich flame region, at locations r/x appro ximately equal to 0.08, where r and x are the radial and axial coordinate, respectively. NO concentrations are shown to decrease with Reynolds number, as the gas residence times are reduced, although mass flow rates of NOx pe r unit mass flow rate of fuel are independent of Reynolds number. (C) 1999 by The Combustion Institute.