Flame structure and flame reaction kinetics - VIII. Structure, properties and mechanism of a rich hydrogen + nitrogen + oxygen flame at low pressure

Abstract

The structure of a rich hydrogen + nitrogen + oxygen flat flame at a pressure of 93 Torr has been examined both experimentally and theoretically. The theoretical approach involved solution of the one-dimensional flame equations, and the reaction mechanism used was that proposed by Day, Dixon-Lewis & Thompson (1972). While essentially confirming this mechanism, the results also draw attention to difficulties in applying the one-dimensional theoretical approach to many experimental flame systems with thicker reaction zones, because of the larger possible contributions of flow divergence or other two-dimensional effects in the latter. Using the same reaction mechanism, a theoretical investigation has also been made of the effect of pressure on the properties of a specific hydrogen + nitrogen + oxygen flame. It was found that the burning velocity S u ∝ p -0.27 between 93 and 760 Torr. This prediction does not correspond with those of the analytical solutions obtained from global reaction rate approaches.