A flame sheet calculation of a confined buoyancy laminar diffusion flame

A numerical model of an axisymmetric confined diffusion flame formed between a CH4 jet and coflowing air is presented. The model utilizes the flame sheet concept to locate the stoichiometric fuel-oxygen interface and,hence, the points of heat release. The numerically simulated steady-state flame assumes a nonunity Lewis number. Despite the low Mach number of the flow, the viscous dissipation term is allowed in the simulation. Allowances are made for natural convection effects and variable thermodynamic and molecular transport properties. The model developed solves the boundary layer equations for describing the thermal and aerodynamic fields established in the confined, laminar diffusion flame under the restriction that the outer oxidizer tube diameter be very large in comparison with the fuel jet diameter. Numerical predictions of temperature, velocity, and stable species concentrations are compared with measured data by Mitchell et al. (1980) of a laminar methane-air diffusion flame.