The ratio [formula omitted] in fuel-lean flames

Abstract

In fuel-lean premixed flames at atmospheric pressure, containing about 100 ppm of nitrogen oxides, the ratio NO 2 NO is large in the primary reaction zone. The ratio decreases in the post-flame gas where super-equilibrium concentrations of O, OH, etc., also decrease. During the decrease, the equilibrium NO + O = NO 2 is approximately satisfied, and a possible mechanism to maintain (2) can be suggested. The equilibrium fails in cooler gas: At around 1200 °K or less, NO 2 NO is quenched and no longer remains balanced with the concentration of O atoms.