Constrained-temperature solutions of coflow laminar diffusion flames

The use of an experimental two-dimensional temperature profile was studied to constrain detailed numerical solutions of a sooting coflow laminar diffusion flame. Experimentally, four optical diagnostic techniques were employed to measure the two-dimensional temperature field in an ethylene-air coflow flame. This experimental temperature field was then applied to impose the temperature in the solution process. Results showed a 40% ethylene-air flame on the Yale Coflow Burner. In the unconstrained solution of the complete set of governing equations, the location of maximum temperature was found along the flame wings, while the experimental temperature field had its maximum along the centerline. Similarly, the location of peak soot volume fraction migrated from along the flame wings in the unconstrained calculation, where soot surface growth processes dominate, to the centerline in the constrained case, where soot inception was the dominant condensed-phase formation mechanism. The distribution of soot in the constrained solution was much more consistent with experimental observations, validating how a soot sub-model may be complicated by the necessity of modeling distributed heat losses in the flame.