33.3.27 SOx Model Dialog Box

The SOx Model dialog box allows you to set parameters related to the SOx postprocessor. See Section  21.2.1 for details about the items below.

Controls

Model   contains the control to enable the model.

SOx Formation   enables the model.

Fuel Streams   allows you to define multiple fuel streams for SOx formation.

Number of Fuel Streams   sets the number of fuel streams. You are allowed up to three fuel streams.

Fuel Stream ID   specifies the fuel stream you are defining in the Fuel Species selection list and the Formation Model Parameters group box.

Fuel Species   is a list containing all of the defined species. This list is used to specify the species that is the fuel associated with a particular Fuel Stream ID, for any combustion model other than non-premixed combustion. You cannot select more than 5 fuel species for each fuel stream, and the total number of fuel species selected for all the fuel streams combined cannot exceed 10.

PDF Stream ID   specifies the PDF stream species associated with a particular Fuel Stream ID, when calculating SOx formation in conjunction with the non-premixed combustion model.

primary   indicates the primary fuel stream species, as defined in the PDF table.

secondary   indicates the secondary fuel stream species, as defined in the PDF table.

Turbulence Interaction Mode   contains parameters related to the effect of turbulent fluctuations on the SOx formation. See this section in the separate Theory Guide for details.

PDF Mode   is a drop-down list containing options that take into account turbulent fluctuations when you compute the specified SO $_2$ formation. See Section  21.1.1 for details.

none   specifies the use of laminar SOx rate calculations, so that the effects of turbulence are ignored.

temperature   includes fluctuations of temperature.

temperature/species   includes fluctuations of temperature and mass fraction of the species selected in the Species drop-down list (which appears when you select this option).

mixture fraction   includes fluctuations of the mixture fraction(s). This is available for non-premixed combustion calculations only.

PDF Type   allows you to specify the shape of the PDF.

beta   models the PDF using this equation in the separate Theory Guide.

gaussian   models the PDF using this equation in the separate Theory Guide.

PDF Points   controls the number of points at which the beta function in this equation or this equation in the separate Theory Guide will be integrated. The default value of 10, which indicates that the beta function will be integrated at 10 points on a histogram basis, will yield an accurate solution with reasonable computation time. Increasing this value may improve accuracy, but will also increase the computation time. This text box is only available when temperature or temperature/species is selected from the PDF Mode drop-down list.

Temperature Variance   allows you to specify the form of transport equation that is solved to calculate the temperature variance.

algebraic   is an approximate form of the transport equation (see this equation in the separate Theory Guide).

transported   solves this equation in the separate Theory Guide.

Tmax Option   provides various options for determining the maximum limit(s) for the integration of the PDF used to calculate the temperature.

global-tmax   sets the limit as the maximum temperature in the flow field.

local-tmax-factor   yields cell-based maximum temperature limits by multiplying the local cell mean temperature by the value entered in Tmax Factor.

specified-tmax   sets the limit for each cell to be the value entered in Tmax.

user-defined   allows you to hook a user-defined function that specifies custom values for the maximum limit ( $T_{\rm max}$), which is used for the integration of the temperature PDF. This option is only available if you have already compiled a UDF and selected it in the SOx Rate drop-down list in the User-Defined Functions group box.

Species   is a drop-down list which appears when temperature/species is selected from the PDF Mode drop-down list. Here you will select the species whose mass fraction fluctuations will be factored into the SOx rate calculations.

User-Defined Functions   allows you to use a user-defined function (UDF) to contribute to the rate of SOx production. See the separate UDF Manual for details. Note that you may also use a UDF to specify custom values for the maximum limit ( $T_{\rm max}$) that is used for the integration of the temperature PDF (when temperature is accounted for in the turbulence interaction modeling).

SOx Rate   allows you to select a compiled UDF.

UDF Rate   provides options for the treatment of the SOx production specified by the UDF.

Replace FLUENT Rate   replaces ANSYS FLUENT's SOx rate calculations with the custom SOx rate produced by your UDF.

Add to FLUENT Rate   adds the custom SOx rate produced by your UDF to ANSYS FLUENT's SOx rate calculations.

Fuel Stream Settings   contains the parameters associated with a particular fuel stream of the SOx model, as specified in the Fuel Stream ID text box in the Fuel Streams group box.

Fuel Type   enables selection of the fuel.

Solid   enables the calculation of solid fuel SOx.

Liquid   enables the calculation of liquid fuel SOx.

Gas   enables the calculation of gas fuel SOx.

S Intermediate   drop-down list enables you to select intermediate species ( h2s, so2, or h2s/so2).

Volatile S Mass Fraction   specifies the mass fraction of sulfur in the volatiles. This parameter appears only for Solid fuel streams.

Fuel S Mass Fraction   field sets the value for correct mass fraction of sulfur in the fuel (kg sulfur per kg fuel). This parameter appears only for Liquid and Gas fuel streams.

Conversion Fraction   specifies the overall mass fraction of the fuel S (for liquid or gas fuels), or the volatile S or char S (for solid fuels), that will be converted to the intermediate species and/or product SO $_2$. The S Intermediate Conversion Fraction has a default value of 1.

Partition Fractions   specifies the mass fraction of the fuel S (for liquid or gas fuels), or the volatile S or char S (for solid fuels) that will become h2s. The remainder will become SO $_2$. This parameter only appears when you select h2s/so2 for the S Intermediate or Char S Conversion drop-down lists.

Char S Conversion   drop-down list selects the char S conversion path as so2, h2s, or so2/h2s. This parameter appears only for Solid fuel streams.

Char S Mass Fraction   specifies the mass fraction of sulfur in the char. This parameter appears only for Solid fuel streams.

Formation Model Parameters   allows you to include SOx products and intermediates.

Include SO3 Product   includes SO3 as a product in all of the fuel streams, as described in this section in the separate Theory Guide.

Include SH and SO Intermediaries   includes SH and SO as intermediates in all of the fuel streams, as described in this section in the separate Theory Guide.

[O] Model   drop-down list specifies the method by which O will be calculated in all of the fuel streams, i.e., equilibrium, partial-equilibrium, or instantaneous in the [O] Model.

[OH] Model   drop-down list specifies the method by which OH will be calculated in all of the fuel streams, i.e., equilibrium, partial-equilibrium, or instantaneous in the [OH] Model.

To use the predicted O and/or OH concentration, select instantaneous in the [O] Model or [OH] Model drop-down list.