Structure of Opposed Jet Flame and NO_x Formation

Abstract

High-intensity premixed combustion (0.71-1.12×10⁹ kJ/m³h) was achieved using an opposed jet burner. The NO_x emission was measured by an NO/NO_x chemiluminescence analyzer. Maximum NO_x formation measured was extremely low and varied from 20 ppm to 40 ppm, depending on the combustion intensity. Such a low NO_x formation is attributed to the short residence time and the structure of the distributed reaction zone. The equivalence ratio at which NO_x is maximized was found to be 1.3. The temperature dependence of NO_x concentration can be given empirically by an Arrhenius expression, and the apparent activation energy is small compared with that of the Zel'dovich mechanism. On the basis of these results, we can conclude that the contribution from the Zel'dovich mechanism is suppressed in the distributed reaction zone and that the NO_x originating from prompt NO is predominant.