ISSN:
0538-8066
Keywords:
Chemistry
;
Physical Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
We report laser absorption measurements of NH3 decay within the flame front region of rich, atmospheric pressure ammonia flames. These data are combined with earlier OH, NH, and NH2 measurements to obtain new estimates for the oscillator strength of NH2. This value, fi = 6.4 × 10-5 for the PQ1,7 line in the (0,9,0) ← (0,0.0) vibrational band of the A2A1 ← X2B1 transition, suggests ΔH°f(NH) ≅ 87 kcal/mol. The ammonia profiles were also combined with previous data on NO, NH, NH2, and OH to provide an extensive database at fuel equivalence ratios (ø) of 1.28, 1.50, and 1.81 for comparison to our kinetic model predictions. This modeling used a one-dimensional flame code which explicitly accounts for the diffusional component in our flame experiments. Modeling results using a conventional mechanism predicted concentration profiles which deviated markedly from our observations. It was possible to obtain much more satisfactory fits by postulating reactions between various NHi (i = 1, 2) species to form N - N bonds. The N2Hj (j = 1-3) species could then lose H atoms via dissociation to ultimately form N2. Inclusion of these reactions in the mechanism allowed us to predict concentration - distance profiles for five different species at three different equivalence ratios that are in good agreement with experiment. The most important component of this mechanism is the recognition that the NHi + NHi reactions dominate the kinetics in rich flames. A most satisfying aspect of these calculations is that the key rate constants in the NHi + NHi sequence were estimated using simple RRK theory.
Additional Material:
7 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/kin.550160603
