# 4.12.2. EDC Combustion Model

The eddy-dissipation concept model in Fuego can be activated through a block in solution options describing with a number of associated options. The EDC fuel name determines the species considered to be “fuel” by the underlying chemistry model used by EDC and must match a species name, see Cantera Material Properties for details on how to define a set of species in Fuego.

    # Sierra > Fuego Procedure > Fuego Region > Solution Options
    BEGIN EDC MODEL SPECIFICATION
        EDC FUEL NAME = C8H18
        EDC MINIMUM PRODUCT FRACTION = 1.0e-6
        EDC IGNITION TIME = 0.0
        EDC REACTION TIME SCALE = 70.0e-6
        USE SINTEF SOOT MODEL
        MINIMUM SOOT PRODUCTION TEMPERATURE = 900.0
        ACTIVATE ABSORPTION MODEL
        INCLUDE EDC LAMINAR LIMIT MODEL
    END

Soot and absorption models can also be activated in this command block, with the added requirement that the soot mass fraction and soot nuclei are also activated. Some necessary or useful equations to solve with EDC are

> - `Enthalpy` - Solves enthalpy conservation for `enthalpy`, activates a post-processor utility to compute `temperature` after each solve. Required with EDC.

> - `Species` - Solves species conservation equations for `mass_fraction`, the last species mass fraction is evaluated analytically to ensure the mass fractions sum to 1. Required with EDC. One of the species must match the EDC fuel name. See Cantera Material Properties for defining transported species.

> - `Soot` - Solves transport of soot mass fraction. Needed for soot transport with the EDC model. See Soot Generation Model for Multicomponent Combustion for more information.

> - `Nuclei` - Solves transport of soot nuclei number density. Necessary for soot transport with the EDC model. Activated automatically if `soot` is activated.

> - `EDC_Product` - Solves transport of the EDC product species. Not commonly used but is needed if product species are being injected into the domain or are present in significant quantities in the ambient.

Additional parameters specific to the EDC model, described in more detail in EDC Turbulent Combustion Model, can also be set in this block. Some commonly used options are

> - `EDC reaction time scale` - Controls the residence time for the EDC extinction model

> - `EDC ignition time` - Offset time for when the EDC model activates (turning on combustion).

> - `Minimum soot production temperature` - Minimum temperature at which soot forms.

> - `EDC minimum product fraction` - A minimum product mass fraction threshold for EDC.

> - `Include EDC laminar limit model` - The EDC model is designed for fully turbulent combustion, and the laminar limit model prevents near singular behavior in near laminar regions of the flow in a RANS context and near fully resolved regions in an LES context

More options are available to be set in this block and can be seen in command references.