Numerical Simulation of Turbulent Diffusion Flame in Cross Flow

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Abstract
The effects of cross wind on the behaviour of a turbulent diffusion flame have been studied numerically. The multicomponent turbulent reacting flow is approached using a two-equation (κ - ϵ) statistical model constructed from the Favre averaging method. To improve the representation of turbulent fields in fully developed and weak turbulent regions, RNG (Renormalization Group) κ - ϵ turbulence modelling is adopted. Infinitely fast reaction is assumed and the combustion rate is fully determined by the turbulent mixing rate of fuel and oxygen using the Eddy Dissipation Concept (EDC). Energy lost by radiation is taken into account and soot formation is computed for the evaluation of the absorption coefficient of the soot-gas mixture using the gray gas assumption. Calculations have been performed both with and without wind. The numerical results show that the flow is characterized by oscillations which affect significantly the flame behaviour. The development of shear buoyancy-driven instabilities (Kelvin-Helmholtz) results in the occurrence of large eddies in the thermal plume. As the cross wind velocity increases, a transition from buoyancy dominated flow to cross wind dominated flow can be noted along with a reduction in oscillation amplitudes. The influence of cross flow on soot formation and the impact of the fire upon leeward neighbouring surfaces are examinated over the 0. - 1,5m/s cross flow velocity range.