Steady State Simulation of Gaseous Combustor Using Local Extiction Eddy Dissipation Concept

Abstract

Non-premixed turbulent reacting flow in a methane-fuelled coaxial jet combustor has been studied numerically employing Reynolds Averaged Navier-Stokes (RANS) models. A Local Extinction approach for treating chemical reaction kinetics within the Eddy Dissipation Concept (EDC) has been examined. It applies a database of pre-calculated chemical time scales, which contains the influence of chemical kinetics that is otherwise timeconsuming to calculate. Simulations were carried out using RNG k-epsilon turbulence models by open-source CFD-toolbox OpenFOAM. The results were compared to available numerical results and experimental data for velocity, and temperature fields. All simulations were conducted with a reasonable number of mesh to demonstrate the accuracy of turbulent RANS models in OpenFOAM solver, which has a wide range of engineering applications in such type of flows. Nomenclature ρ = mean density (kg/m 3 ) µ = molecular viscosity [kg/(m s -1 )] t µ = turbulent viscosity [kg/(m s -1 )] E = total energy per unit mass (J/kg) T = temperature (K) chem S = chemical source term in the energy equation (W/m 3 ) rad S = radiation source term in the energy equation (W/m 3 ) D = molecular diffusivity (m 2 /s) t Sc = turbulent Schmidt number Y = mass fraction of species k = Turbulent kinetic energy (m 2 /s 2 ) ε = Turbulent dissipation (m 2 /s 3 ) k G = production of turbulent kinetic energy by velocity gradient (W/m 3 ) b G = production of turbulent kinetic energy by buoyancy (W/m 3 ) ε α = RNG k-ε model parameter k α = RNG k-ε model parameter η = ratio of turbulence to mean shear time scale β = RNG k-ε model parameter p C = specific heat at constant pressure [J/(kg K -1 )] ij S = mean strain rate tensor ν * = kinematic viscosity of the fine-structure mixture 2 ch τ = chemical time (s) r q uu r = radiation flux (J/s) χ = reacting fraction of the fine structures m * & = mass transferred between the fine structures and the surroundings