The role of the NNH mechanism in NO_x formation is investigated using a jet stirred reactor (JSR). Two sets of experiments are performed over a wide range of fuel-air equivalence ratios (0.8-1.3) for combustion of hydrogen. Each set of experiments use a different diluent to maintain the temperature of the JSR at a constant value while the fuel-air equivalence ratio is varied from lean to rich. Nitrogen and argon are the diluents used to maintain the temperature of the JSR at 1635K and 1525K respectively. The two sets of experiments show that NO_x decreases as fuel-air equivalence ratio is increased from 0.8 to 1.3 Chemical kinetic modeling is used to explain the trends seen in the experiments. Different chemical reactor networks are developed to model the NO_x emission in the JSR using CHEMKIN 17.2. Chemical kinetic modeling shows reasonable agreement with both sets of experimental data. The sensitivity analysis of this modeling shows that NNH is a major contributor for NO_x production on the rich region, for both the diluents.
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