Modeling of Extinction in Turbulent Diffusion Flames by the Velocity-Dissipation-Composition PDF Method

The velocity-dissipation-composition probability density function (pdf) method is used to model a turbulent CO/H2/N2-air-piloted jet diffusion flame in the regime of extinction. The thermochemistry is modeled by a three-scalar simplified formulation obtained by the intrinsic low-dimensional manifold (ILDM) method. Calculations are performed for five different jet velocities, and the scalar pdfs are compared with experimental data. Overall good agreement is obtained between the calculations and the experimental results, with the only significant difference being the high level of scatter in the experimental data compared with the pdf results: reasons for this difference are discussed. The pdf method is found to~,predict flame extinction at approximately the same jet velocity as that of the experiment. A small amount of local extinction is observed in the pdf results for the high-jet-velocity cases.