Application of Escimo to the Turbulent Hydrogen-Air Diffusion Flame

摘要

A simplified version of the ESCIMO program is applied to the hydrogen-air diffusion flame and is compared with experimental data. The reaction is assumed to be laminar-diffusion controlled within the fold. Fold properties depend upon age alone, at a given point in the flame. Fold properties at birth can be deduced by tracing upstream along a line of constant mean fuel-air ratio. Fold creation rate is proportional to entrainment rate, distributed in arbitrary ways across the jet. Fold size at birth is proportional to local jet width; and the fold stretching rate is proportional to the average velocity gradient in the mean flow along the postulated trajectory. Comparisons with the experimental data show that: the agreement in respect of hydrodynamic features is good; suitable choice of input parameters permits the experimental data for unmixedness to be fitted fairly well; and the conceptual content of ESCIMO must be enlarged in order to allow for intermittency effects.