Structure of Nonpremixed CH₄/N0₂ Flames

Abstract

The structure of nonpremixed CH₄/N0₂ flames is investigated for various values of the strain rate and pressure. Numerical calculations are performed using a detailed chemical kinetic mechanism comprising 137 reactions among 33 species, a skeletal chemical kinetic mechanism comprising 92 reactions among 25 species and reduced chemical-kinetic mechanism comprising 10 and 7 overall reactions. The skeletal mechanism is derived from the detailed mechanism, and the reduced mechanisms are derived from the skeletal mechanism. Chemical reactions in the flame are found to take place in three regions-a fuel-consumption region, a N0₃ - consumption region and a product-formation region. In the fuel-consumption region the predominant reactions taking place are those between the fuel and the radicals to form the intermediate compounds H₂ and CO. In the N0₂ - consumption region the predominant reactions are between the N0₂ and radicals to form the intermediate compounds NO and 0₂. In the product-formation region the products C0₂, H₂0 and N₂ are formed from the intermediate species. The radicals are also formed in the product-formation region. The flame structure and critical conditions of extinction calculated using the various mechanisms are found to agree with each other.

Keywords:

• Reduced mechanism
• nonpremixed flames