Low-Mach-Number Simulations of Diffusion Flames with the Chemical-Diffusive Model

We describe the calibration and implementation of the chemical-diffusive model (CDM) for the simulation of diffusion flames. The CDM uses the relatively simple functional form of an Arrhenius rate along with diffusion parameters, energy, and a progress variable to control the conversion of reactants to products and the rate of chemical energy release. The constants for the model are determined by an optimization procedure. Input into this procedure is obtained from detailed chemical models or experimental data. Prior CDM applications computed properties of flames and detonations for single equivalence-ratio (ER) mixtures or mixtures with variable ER, but generally for premixed combustion. Now we have taken the variable-ER form of the CDM, incorporated it into a low-Mach-number solution of the Navier-Stokes equations (based on the BIC-FCT algorithm), and calibrated it for simulations of a diffusion flame. Computations of test problems, such as laminar and co-flow diffusion flames are demonstrated, culminating in a three-dimensional simulation of a fire whirl.