The anchoring of gaseous jet diffusion flames in stagnant air

A numerical analysis is presented to describe the structure of the attachment region of gaseous jet diffusion flames in stagnant air. For the typical Reynolds numbers encountered in applications, the region of flame attachment, in the near wake at the injector rim, is small compared with the injector radius. The local flow, which we consider to be laminar, quasi-steady and two-dimensional, is determined by the wall value of the fuel stream velocity gradient and the chemical reaction time or residence time in the premixed flame of a stoichiometric mixture of the fuel stream and required amount of air. When the Karlovitz number, or product of the velocity gradient and the flame residence time, grows above a critical value the flame is lifted off the injector.