For the prediction of the properties of the turbulent jet diffusion flames, it is necessary to combine the turbulence models with the combustion models. As the turbulence models, so-called zero equation model and two equation model are used. As the combustion models which include both the reaction model and the thermodynamics model, spalding model which is to solve the conservation equations for chemical species and the stagnation enthalpy, and the concentration fluctuation model for which clipped normal probability distribution function is proposed for the mixture fraction fluctuations, are used. All the combined models are tested by comparing predictions with experimental data for two round free jet turbulent flows ; inert and isothermal flow (cold jet), unpremixed reacting flow (diffusion flame).
For inert and isothermal flows, the two equation model gives very good agreements. And for unpremixed reacting flows, the combined models have, on the whole, the similar tendency with data but qualitatively there are some discrepancies in parts.
More experimental data and physical modelling for diffusion flames are urgently required. For efficient computations, a general computer coded for two dimensional boundary layer flows, GENMIX, were used in this study.