Emissions Workflow

Follow the steps in this workflow to simulate NOx and/or Soot emissions.

Before following this workflow, make sure that you have completed the model selection steps from the Reacting Flow General Workflow, and one of the following specific detailed workflows:

This emissions workflow is not suitable for use with the Interphase workflow. The Interphase workflow describes how to use emissions models that are specific to the Lagrangian phase.

The NOx Emission model requires species and enthalpy models to be activated, so a flow model must be selected unless one is already selected with the combustion model. Segregated Flow is the recommended choice when using the NOx Emission model.

  1. For the physics continuum that represents the reacting flow, select the following models—in addition to the models that are previously selected, with Auto-Select recommended models activated:
    Group Box Model
    Optional Models You can select one or both of these models.
    • NOx Emission: provides a framework for modeling the NOx transport equation by providing a tool to predict the NOx production from various sources.
    • Soot Emissions
    Specific NOx Models (available when NOx Emission is activated) You can select one or more of the NOx models to calculate the reactive source term in the NOx transport equation.
    • NOx Fuel: contributes the NOx emission that arise from the fuel portion. You can use this model for a pure gas-phase combustion. The NOx Fuel model transports three passive scalars: NO, NH3, and HCN. When this model is selected, HCN and NH3 boundary conditions are available for you to specify the inlet composition.
    • NOx Thermal: contributes to the source term by using the three-step extended Zeldovich reaction mechanism.
    • NOx Prompt: contributes the NOx emission that arise from the reaction of hydrocarbon fragments and molecular nitrogen. Often produced in combustion environments with relatively low-temperature and fuel-rich conditions—as in staged combustion systems and gas turbines.
    Thermal NOx Models (available when NOx Thermal is activated) For combustion set-ups that do not use the Complex Chemistry model, the NOx Thermal model uses the coefficients—A, B, C, and D, in Eqn. (3626)—that are stored in the flamelet table, to compute the averaged reactive source term in the NOx transport equation. When using the Complex Chemistry model, the Complex Chemistry model computes the source terms at each iteration.
    Soot Emissions Model (available when Soot Emissions is activated) You can select only one Soot model.
    • Soot Moments: uses the Method of Moments technique to calculate the soot particle size distribution function (PSDF). Can solve up to four moments: Moment 0, 1, 2, and 3.
    • Soot Two-Equation: solves transport equations for scaled number density and scaled mass density based on the Moss-Brookes-Hall (MBH) technique.
    • Soot Sections: solves a soot mass fraction transport equation for each section, based on a description of sections containing soot particles of equal volume, allowing a volume-based discretization of particle sizes together with conservation of the soot number density and mass.
  2. The Soot Sections model provides options to create various reports.
    For instructions on plotting the particle size distribution for soot sections, see Plotting Soot Sectional Particle Size Distribution.
  3. Return to the specific detailed workflow that you are following.