Dynamic and scalar turbulent fluctuation in a diffusion flame of an-axisymmetric methane jet into air

Abstract

A study of turbulence/combustion interactions in a relatively large turbulent diffusion flame of an axisymmetric methane jet into air is presented. A first order k-e turbulence closure model is used along with two different models (equal scales and non-equal scales) for the submodel describing the scalar dissipation rate. The flamelet concept is used to model the turbulent combustion along with a joint mixture fraction/strain rate probability density function (PDF) for the prediction of the average parameters of the turbulent diffusion flame. The numerical approach is that of Patankar and Spalding, while the flamelet simulations are obtained from the RUN-1DL code of Rogg and co-workers based on a 17 species detailed reaction mechanism. The chosen configuration is that of the experimentally studied turbulent diffusion flame of Streb [1]. A comparison between these experimental results and the obtained numerical ones is thus presented. Relatively good agreements are obtained which show the usefulness of the two-scale model compared to the classical one-scale model for predicting turbulent diffusion flames. Nonetheless some discrepancies are obtained in the outer and downstream regions of the jet, especially in comparison with the experimental data. These are attributed to short coming of the considered turbulence model and soot radiation which is not accounted for.List of symbols a laminar strain rate, s À1 D nozzle diameter, m F generalized turbulent parameter G mixture fraction k turbulent kinetic energy, m 2 s À2 P probability density R s time scale ratio r radial distance, m T temperature, K U velocity, m s À1 x axial distance, m z scalar varianceGreek symbols l dynamic viscosity, kg m À1 s À1 m kinematic viscosity, m 2 s À1 r Schmidt number e dissipation rate, m 2 s À3 g scalar dissipation rate, s À1 q density, kg m À3 Subscripts 0 reference point b burning part q quenching st stoichiometric

Experimental and Numerical Study of Swirling Diffusion Flame Provided by a Coaxial Burner: Effect of Inlet Velocity Ratio

“…The comparison between the computed results and experimental data showed that both RANS and DDES obtained the distribution of axial velocity, tangential velocity and temperature. Hidouri et al [23] studied turbulent diffusion flames using the first-order k-ε model, along with two different methods for the sub-model, describing the scalar dissipation rate. They showed that the use of a non-equal scale model improved the obtained numerical results.…”