Laser-Induced Fluorescence Measurements and Modeling of Nitric Oxide Formation in High-Pressure Flames

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Abstract
We have obtained quantitative LIF measurements of NO concentration in the postflame zone of a series of flat, laminar, premixed C2H6/O2/N2 flames at pressures ranging from 3.05 to 14.6 atm. The temperatures of the flames were 1600-1850K, indicating that most of the NO produced in the flames is prompt NO. We have found that the equivalence ratio corresponding to the peak NO concentration at a given pressure shifts towards leaner conditions with increasing pressure. In addition, we have modeled the flames using two chemical kinetics models: the Glarborg-Miller-Kee mechanism as modified by Drake and Blint (GMK-DB), and the Miller-Bowman mechanism (MB). Both models accurately predict the pressure trends of NO formation, while the quantitalive agreement with measurements is, in general, good for the GM K-DB model and poor for the M B model. Explanations are provided both for the poor agreement found with the MB model and for the shift in peak NO concentration with pressure.