Prediction of turbulent diffusion flames with a four-equation turbulence model |
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Authors: | W Kolbe W Kollmann |
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Institution: | Lehrstuhl für Technische Thermodynamik, RWTH Aachen, Germany;von Karman Institute, Rhode-St-Genèse, Belgium |
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Abstract: | For turbulent flame prediction a four-equation turbulence model consisting of the turbulent kinetic energy, the dissipation rate and the density-velocity correlations using unweighted statistics is suggested. The fluctuating concentrations are taken into account by using Spalding's (1971) equation for the variance of the mixture fraction f and by defining the probability density function of f as beta-function. The thermodynamic model for the combustion of H2 with air assumes infinitely fast reaction in a global single step. Preliminary results are shown for the calculation of Kent and Bilger (1972) turbulent H2-air diffusion flame. For this flame with fluctuating density the inclusion of the velocity-density correlations appears to be essential, because they have a strong effect especially on the development of the turbulent viscosity and the mean velocity and mass fraction profiles. Consequently the mean concentrations are in good agreement with the experimental results. |
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