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20.3.1 Overview and Limitations

FLUENT provides two empirical models for the prediction of soot formation in combustion systems. In addition, the predicted soot concentration can be included in the prediction of radiation absorption coefficients within the combustion system. You can include the effect of soot on radiation absorption when you use the P-1, discrete ordinates, or discrete transfer radiation model with a variable absorption coefficient.



Predicting Soot Formation


FLUENT predicts soot concentrations in a combustion system using one of two available models:

The Khan and Greeves model is the default model used by FLUENT when you include soot formation. In both models, combustion of the soot (and particle nuclei) is assumed to be governed by the Magnussen combustion rate [ 229]. Note that this limits the use of the soot formation models to turbulent flows. Soot formation cannot be predicted by FLUENT for laminar or inviscid flows.

Both soot formation models are empirically-based, approximate models of the soot formation process in combustion systems. The detailed chemistry and physics of soot formation are quite complex and are only approximated in the models used by FLUENT. You should view the results of these models as qualitative indicators of your system performance unless you can undertake experimental validation of the results.



Restrictions on Soot Modeling


The following restrictions apply to soot formation models:


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