Laser-saturated fluorescence measurements of nitric oxide in an inverse diffusion flame

Inverse diffusion flames (IDFs) are a primary component of staged-air combustion processes, which are often used to achieve ultralow NOx emissions. Unfortunately, such IDFs created by mixing air with hot fuel-rich combustion products rather than the usual unreacted fuel have received little previous attention in the literature. Here, we use laser-saturated fluorescence (LSF) to make nonintrusive point measurements of nitric oxide concentration throughout a single atmospheric IDF of this type; thermocouple-based temperature measurements are also made at specific locations including those of the concentration measurements. These measurements demonstrate similarities between IDF and normal diffusion flame behavior, and indicate that the majority of the IDF-attributable NO is generated at the IDF tip. The results suggest that the dominant NO mechanism varies throughout the flame, and provide data relevant to assessment of future kinetics models. (C) 1998 by The Combustion Institute