ECFM-3Z Model Reference

The ECFM-3Z model includes the NOx Zeldovich and Soot One-Step models.


Theory	See ECFM-3Z.
Provided By	[physics continuum] > Models > In-Cylinder Models
Example Node Path	Continua > Physics 1 > Models > ECFM-3Z
Requires	Simcenter STAR-CCM+ In-cylinder (open separate add-on) Space: Three Dimensional Material: Multi-Component Gas Reaction Regime: Reacting StarIce: In-Cylinder StarIce: In-Cylinder Combustion
Properties	Key properties are: Start Time of ECFM, ECFM Fuels. See ECFM-3Z Properties.
Activates	Physics Models	ECFM Post Flame Models
	Initial Conditions	Fuel/Oxidizer Mixing State Specification. See Initial Conditions.
	Boundary Inputs	Fuel/Oxidizer Mixing State Specification See Boundary Settings.
	Solvers	ECFM-3Z Combustion. See Solvers.
	Field Functions	AImode Combustion Heat Release Rate, Enthalpy of [species], Equivalence Ratio, Exhaust Gas Recirculation Mole Fraction, FPmode Combustion Heat Release Rate, PSTOXmode Combustion Heat Release Rate, SImode Combustion Heat Release Rate, Specific Heat of [species], and Total Conditional Fuel Mass Fraction. See Field Functions.

ECFM-3Z Properties

Convection

In transport equations, you can choose from a range of schemes that calculate the convection term at a cell face. This calculation requires Simcenter STAR-CCM+ to compute the face value of a quantity from the surrounding cell values. The method used for computing this face value has a profound effect on the stability and accuracy of the numerical scheme. For guidance on selecting a convection scheme, see Convective Flux.

1st-order: First-order convection scheme.
2nd-order: Second-order convection scheme.

Start Time of ECFM

Time at which ECFM combustion begins.

ECFM Fuels

The fuel selection for ECFM combustion. Any fuel containing C, H, O, or N is suitable.

Combustion Reset Time

When regressing the progress variable back to 0 in multiple-cycle simulations, the mass fractions of species and their tracers are changed at each time step according to Eqn. (3932) until this time at which combustion reset will be complete.

The combustion reset time is set automatically to 5 degCA before intake valve opening (IVO).

In-Cylinder Cyclic Period

Time that is required for one cycle. Typically, in four-stroke engines, this is the time taken for 720 crank-angle degrees—or in two-stroke engines, 360 crank-angle degrees.

Set to the same value as the Spark Ignition Period.

Regression Temperature

Temperature below which the regression model is active. See Regression.

Secondary Gradients

Neglect or include the boundary secondary gradients for diffusion and/or the interior secondary gradients at mesh faces.

On: Default value. Solves for interior and boundary types of secondary gradient.
Off: Does not solve for either type of secondary gradient.
Interior Only: Solves for the interior secondary gradients only.
Boundaries Only: Solves for the boundary secondary gradients only.

Flow Boundary Diffusion

When activated, this property includes the flow-boundary diffusion fluxes (or viscous fluxes for flow models) as given by Eqn. (899). This property is activated by default.

Coefficient RapCo

CO adjustment factor in the unburnt fuel reaction mechanism.

r_{C O}

in Eqn. (3927).

Coefficient BetaMix

Coefficient for the turbulent mixing between fuel and air + EGR (exhaust gas recirculation).

β_{m i x}

in Eqn. (3837) andEqn. (3838).

Cross Gradient Option

When activated, allows a cross gradient contribution in the diffusion term of the unburnt species and enthalpy equations.

\nabla

in Eqn. (3947).

Initial Conditions

Fuel/Oxidizer Mixing State Specification: Allows you to specify if the fuel and oxidizer are unmixed or premixed at the subgrid level.; When the property Allow Per-Part/Part Surface/Contact Values is activated on the associated region, boundary, or interface, the optional property to specify the Fuel/Oxidizer Mixing State Specification by Part Subgroup node also becomes available.
Species Specification: Allows you to choose if the species mass fraction or mole fraction is used. A corresponding sibling node appears which allows you to set the Species Mass Fraction or Species Mole Fraction using constant or composite values.

Boundary Settings

Applies to Inlet and Outlet boundary types.

Fuel/Oxidizer Mixing State Specification: At the domain boundaries, allows you to specify if the fuel and oxidizer are unmixed or premixed at the subgrid level. Unmixed is the default.

ECFM-3Z Combustion Solver Properties

Under-Relaxation Factor: In order to promote convergence, this property is used to under-relax changes of the solution during the iterative process. If residuals show solution divergence or do not decrease, reduce the under-relaxation factor.
Verbosity: Allows you to choose how much information Simcenter STAR-CCM+ reports in the Output window while the simulation is running. This property is useful for debugging problems when they occur. The available options are None, Low, and High.
Solver Frozen: When On, the solver does not update any quantity during an iteration. It is Off by default. This is a debugging option that can result in non-recoverable errors and wrong solutions due to missing storage. See Finite Volume Solvers Reference for details.
Reconstruction Frozen: When On, Simcenter STAR-CCM+ does not update reconstruction gradients with each iteration, but rather uses gradients from the last iteration in which they were updated. Activate Temporary Storage Retained in conjunction with this property. This property is Off by default.
Reconstruction Zeroed: When On, the solver sets reconstruction gradients to zero at the next iteration. This action means that face values used for upwinding (Eqn. (905)) and for computing cell gradients (Eqn. (917) and Eqn. (918)) become first-order estimates. This property is Off by default. If you turn this property Off after having it On, the solver recomputes the gradients on the next iteration.
Temporary Storage Retained: When On, Simcenter STAR-CCM+ retains additional field data that the solver generates during an iteration. The particular data retained depends on the solver, and becomes available as field functions during subsequent iterations. Off by default.

Field Functions

AImode Combustion Heat Release Rate: Heat release rate due to auto-ignition in the unburnt gases zone.
FPmode Combustion Heat Release Rate: Heat release rate due to flame propagation.
PSTOXmode Combustion Heat Release Rate: Heat release rate due to post-flame oxidation.
SImode Combustion Heat Release Rate: Heat release rate due to spark ignition.
Enthalpy of [species]: The enthalpy of the specified species.
Equivalence Ratio: $Φ$ in Eqn. (3576).
Exhaust Gas Recirculation Mole Fraction: $X_{e g r}$ in Eqn. (3946).
Specific Heat of [species]: The specific heat of the given species.
Total Conditional Fuel Mass Fraction: $Y_{f u e l}^{u}$ in Eqn. (3837).