Home – Home – Jornals – Combustion, Explosion and Shock Waves 2026 number 4

Using the detailed kinetic mechanism of GRI-Mech 3.0, a computational verification of the applicability limits of Zel’dovich's assumption on quasi-equilibrium concentrations of atomic N in NO formation reactions via the thermal mechanism in a methane-air diffusion flame at high process pressures and temperatures was performed. In contrast to Zel’dovich's assumption, with an increase in the flame diffusion rate (χ _st ), the CH + N₂ reaction becomes the main source of nonequilibrium N compared to the O + N₂ reaction, but only a portion (62 ÷ 87 %) of the released N directly participates in oxidation reactions. As a result, the rates of the N + O₂ and N + OH reactions in the Zeldovich mechanism increase by 30 and 26 times, respectively, while under the assumption of a quasi-equilibrium N concentration, their overall rate increases by only 30 %. It is shown that this assumption in the Zeldovich thermal mechanism is applicable in the range of χ _st = 1 ÷ 8 s^-1, with the calculated NO _x emission index values deviating within ±37 % at the extremes of this range.