Defining the Materials

Simcenter STAR-CCM+ In-cylinder requires information about the composition of air, fuel, and exhaust gas in the engine.

By default, Simcenter STAR-CCM+ In-cylinder uses the following air and exhaust gas materials:
  • Air: mixture of N2 (Nitrogen) and O2 (Oxygen) with a mass weighting of 0.7669 and 0.2331, respectively.
  • Exhaust: for combustion simulations, as calculated by the Automatic Composition Intitialization. See Simcenter STAR-CCM+ In-cylinder "Formulation—Exhaust Gas Composition."

You can replace, add, and delete material components as required.

Note

To modify the exhaust gas, you must de-activate Automatic Composition Initialization, see Setting the Operating Conditions.

The fuel can be composed of a single material or of multiple materials. A multi-component representation of the fuel usually increases the accuracy, at the expense of computational cost. For liquid fuels, you specify the components of the liquid and the vapor arising from these components, respectively. For a gaseous fuel, you specify the components of the gas.

The following material databases are available:

Standard
The Standard material database provides constant material properties for liquids and vapors.
ecfmProp
The ecfmProp material database provides constant and temperature dependent material properties in tabular form (Table(T)). For vapors, Simcenter STAR-CCM+ In-cylinder applies constant material properties by default. For liquids, Simcenter STAR-CCM+ In-cylinder uses Table(T) data for the following material properties:
  • Dynamic Viscosity
  • Saturation Pressure
  • Surface Tension
  • Specific Heat
  • Thermal Conductivity (if available)

For Latent Heat of Vaporization, which does not support Table(T) data, Simcenter STAR-CCM+ In-cylinderapplies a field function that interpolates the tabular data.

For ECFM combustion simulations, only the ecfmProp material database is available. For Complex Chemistry combustion simulations, you can select liquid fuels from the Standard or the ecfmProp material database. You select the vapor arising from that fuel or gaseous fuels from the imported Chemkin material database. Each material from the Chemkin material database can only be used for one fuel component.

The databases are stored as .mdb files in your main Simcenter STAR-CCM+ installation directory (Windows) or in the star subdirectory of that directory (Linux)—props.mdb (Standard) and ecfmProp.mdb, respectively.

Simcenter STAR-CCM+ In-cylinder allows you to modify material properties in the Simcenter STAR-CCM+ simulation tree.

To define the material of the air that passes through the engine:

  1. Right-click the Materials > Air node and select Edit.
    The Air Properties group-box displays the default air composition.
  2. To modify the default air components, set the following properties as required:
    • Air Component
    • Weighting
    NoteFor an ECFM or a Complex Chemistry combustion simulation, you cannot modify the air composition.
  3. To add a component:
    1. In the Air Properties group-box, click Add Components.
    2. In the Add Components dialog, select the required components from the material database and click OK.
  4. To delete a component:
    1. Right-click anywhere in the row of that component and select Delete Component.
    2. In the Confirm Component Deletion dialog, click Yes.
  5. Click Apply, then Close.
To define the material of the fuel:
  1. Right-click the Materials > Fuel node and select Edit.
  2. To add or delete a fuel component, follow Step 3 or Step 4, respectively.
  3. For a liquid fuel, for each added component, set the corresponding vapor material.
  4. For each component, set Mass Weighting to suit your fuel.
Below the fuel components, the Stoichiometric A/F Ratio shows the ideal ratio of air to the specified fuel to completely burn the fuel without excess air.

For a single-component fuel, LHV (Lower Heating Value) displays the lower heating value of the fuel according to the ECFM-3Z material database. You can replace the default value with a value obtained experimentally. Clicking Reset restores the default value.

  1. Click Apply, then Close.
    For more information, see Materials Reference.