A Two-Fluid Model for Turbulent Diffusion Flames at Moderate Damkoehler Numbers

Article abstract of DOI:10.1021/j100371a020

Since most practical combustors involve turbulent, nonpremixed flames, research has focused on developing a fundamental understanding of such flames.In the present paper, the oxidation of carbon monoxide by air in a turbulent flow is investigated.The turbulent reacting flow is described adopting Spalding's intermittency model, the two-fluid model, which was developed to improve the modeling of exchange processes within the turbulent mixing layer of the two gas streams.The turbulent flow field is modeled adopting a classical k-ε turbulence model.Since the oxidation of carbon monoxide at moderate Damkoehler numbers cannot be considered as being diffusion controlled, the two-fluid model is extended to include the finite reaction rate adopting a global rate expression.The reaction model is closed by using a three dimensional probability density function with respect to the mixture fraction, the mass fraction of carbon monoxide, and enthalpy.The results of the calculations are compared with results from a corresponding single-fluid model as well as results of measurements in a turbular furnace 5 m in length and 0.5 m in diameter which clearly show an improvement of the simulations of the turbulent diffusion flame with the two-fluid model compared to the single-fluid calculations within the turbulent mixing layer.