Species Concentrations and Turbulence Properties in Buoyant Methane Diffusion Flames

Past measurements of mean velocities and temperatures in buoyant turbulent, axisymmetric methane diffusion flames burning in still air have been extended to include mean species concentrations (CH₄, N₂, O₂, CO₂, H₂O, CO, and H₂) and turbulence quantities. The new measurements were used to evaluate a Favre-averaged, k-ε-g turbulence model of the process—with all empirical constants fixed by measurements in noncombusting flows. Use of the laminar flamelet method to treat scalar properties yielded reasonably good predictions of mean properties. Turbulence predictions were less satisfactory, generally underestimating fluctuation levels and Reynolds stresses in highly buoyant regions of the flows. Measurements indicated significant anisotropy of turbulence properties in the same regions. These findings suggest the need for multistress closure to adequately model turbulence properties in buoyant flames.