Characterization of hydrogen triple flame propagation in vitiated laminar coaxial flow

This paper numerically analyzes the propagation characteristics of a hydrogen flame in coaxial vitiated flow in a confined quartz tube. The transient propagation of the flame is calculated using Li's Mechanism of hydrogen oxidation, and the propagation characteristics are discussed based on these calculations. The formation of the reaction zone, the ignition of fuel, the transformation of the flame's base structure, and the propagation behavior of the hydrogen jet flame base are characterized in the present study. The flame characteristics is analyzed based on calculated results, the information provide several insight into the flame propagation and ignition layer at the leading edge in vitiated situations. The results show that the leading point of a hydrogen flame in coaxial fresh air propagates along the preferred equivalence ratio isoline as the flame has a triple flame structure. On the contrary, in vitiated coaxial flow, the propagation of the hydrogen flame fits triple flame theory more precisely. The flame's kinetic properties show that hydrogen flame propagation in coaxial vitiated flow is still dominated by the triple flame. The results also suggest that the transformation of the flame during propagation is affected by the pool of radicals as well as the chemical reactions.