16.11 Postprocessing the Non-Premixed Model Results

The final step in the non-premixed combustion modeling process is the postprocessing of species concentrations and temperature data from the mixture fraction and flow-field solution data. The following variables are of particular interest:

• Mean Mixture Fraction (in the Pdf... category)

• Secondary Mean Mixture Fraction (in the Pdf... category)

• Mixture Fraction Variance (in the Pdf... category)

• Secondary Mixture Fraction Variance (in the Pdf... category)

• Fvar Prod (in the Pdf... category, which is the production term in the mixture fraction variance transport equation)

• Fvar2 Prod (in the Pdf... category)

• Scalar Dissipation (in the Pdf... category)

• PDF Table Adiabatic Enthalpy (in the Pdf... category)

• PDF Table Heat Loss/Gain (in the Pdf... category)

• Mass fraction of (species-n) (in the Species... category)

• Mole fraction of (species-n) (in the Species... category)

• Molar Concentration of (species-n) (in the Species... category)

• RMS (species-n) Mass Fraction (in the Species... category)

• Static Temperature (in the Temperature... category)

• RMS Temperature (in the Temperature... category)

• Enthalpy (in the Temperature... category)

• Mean Probability(in the Unsteady Flamelet... category)

• Mean Temperature(in the Unsteady Flamelet... category)

• Mean Mass Fraction of (species-n) (in the Unsteady Flamelet... category)

For the unsteady laminar flamelet model, mean species mass fractions are displayed for the first fifty species in the flamelet kinetic mechanism.

These quantities can be selected for display in the indicated category of the variable-selection drop-down list that appears in postprocessing dialog boxes. See Chapter  31 for their definitions.

In all cases, the species concentrations are derived from the mixture fraction/variance field using the look-up tables. Note that temperature and enthalpy can be postprocessed even when your ANSYS FLUENT model is an adiabatic non-premixed combustion simulation in which you have not solved the energy equation. In both the adiabatic and non-adiabatic cases, the temperature is derived from the look-up table.

Figures  16.11.1 and   16.11.2 illustrate typical results for a methane diffusion flame modeled using the non-premixed approach.

Figure 16.11.1: Predicted Contours of Mixture Fraction in a Methane Diffusion Flame

Figure 16.11.2: Predicted Contours of CO $_2$ Mass Fraction Using the Non-Premixed Combustion Model