39.
Flame structure and NO emission characteristics in counterflow diffusion flame of blended fuel of H
2/CO
2/Ar have been numerically simulated with detailed chemistry. The combination of H
2, CO
2 and Ar as fuel is selected to clearly display the contribution of hydrocarbon products to flame structure and NO emission characteristics due to the breakdown of CO
2. A radiative heat loss term is involved to correctly describe the flame dynamics especially at low strain rates. The detailed chemistry adopts the reaction mechanism of GRI 2.11, which consists of 49 species and 279 elementary reactions. All mechanisms including thermal, NO
2, N
2O and Fenimore are taken into account to separately evaluate the effects of CO
2 addition on NO emission characteristics. The increase of added CO
2 quantity causes flame temperature to fall since at high strain rates a diluent effect is prevailing and at low strain rates the breakdown of CO
2 produces relatively populous hydrocarbon products and thus the existence of hydrocarbon products inhibits chain branching. It is also found that the contribution of NO production by N
2O and NO
2 mechanisms are negligible and that thermal mechanism is concentrated on only the reaction zone. As strain rate and CO
2 quantity increase, NO production is remarkably augmented. Copyright © 2002 John Wiley & Sons, Ltd.
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