Auto-Ignition Models Reference

The Auto-Ignition model itself has no properties—when selected, it provides the option to further select one of the specific auto-ignition models.

Table 1. Auto-Ignition Models Reference
Model Names and Abbreviations	ECFM Standard Auto-Ignition		Standard
	ECFM TKI Auto-Ignition		TKI
Theory	See Auto-Ignition.
Provided By	[physics continuum] > Models > ECFM Auto-Ignition Models
Example Node Path	Continua > Physics 1 > Models > ECFM Standard Auto-Ignition
Requires	When using Simcenter STAR-CCM+ In-cylinder, the appropriate Simcenter STAR-CCM+ models are selected by the Simcenter STAR-CCM+ In-cylinder application.
Properties	Key properties are: Convection, Flow Boundary Diffusion. See Auto-Ignition Models Properties.
Activates	Other Nodes	[physics continuum] > Table Generators > TKI Table Generator (available with the ECFM TKI Auto-Ignition model). See Table Generators Reference.
	Materials	Cetane/Octane Number. See Materials and Methods.
	Monitors	Yigi
	Field Functions	Ignition Progress Variable. See Field Functions.

Auto-Ignition Models Properties Lookup


	Standard		TKI
		(with Knock)		(with Knock)
Burning Rate Factor			✓	✓
Convection	✓	✓	✓	✓
Delay Factor			✓	✓
Delay Activation Temperature	✓	✓
Delay Cetane Number Factor	✓
Delay Density Exponent	✓
Delay Fuel Exponent	✓
Delay Octane Number Factor		✓
Delay Octane Number Exponent		✓
Delay Oxidizer Exponent	✓
Delay Pre-Exponent Factor (Delay PreExp Factor)	✓	✓
Delay Pressure Exponent		✓
Dual Zone TKI Model Option			✓	✓
Flow Boundary Diffusion	✓	✓	✓	✓
Reaction Activation Temperature	✓	✓
Reaction Fuel Exponent	✓	✓
Reaction Oxygen Exponent	✓	✓
Reaction PreExp Factor	✓	✓

Auto-Ignition Models Properties

Burning Rate Factor

To adjust the auto-ignition reaction rate (derived from pre-computed TKI tables), you can specify the Burning Rate Factor (

F_{b r}

in Eqn. (4024)) by which the auto-ignition reaction rate is multiplied.

See TKI Tables.

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.

Delay Activation Temperature

τ_{d}

in Eqn. (4020).

Delay Cetane Number Factor

F_{c n}

in Eqn. (4020).

Delay Density Exponent

a_{ρ}

in Eqn. (4020).

Delay Factor

Specifies the factor (

F_{τ_{d}}

in Eqn. (4026)) by which the auto-ignition delay is multiplied.

Delay Fuel Exponent

a_{f}

in Eqn. (4020).

Delay Octane Number Factor

F_{o n}

in Eqn. (4021).

Delay Octane Number Exponent

The delay octane number exponent

a_{o n}

in Eqn. (4021).

Delay Oxidizer Exponent

a_{o}

in Eqn. (4020).

Delay Pre-Exponent Factor

A_{d}

in Eqn. (4020).

Delay Pressure Exponent

a_{p}

in Eqn. (4021).

Dual Zone TKI Model Option

Makes use of a progress variable that is different from the flame propagation, in order to remedy the heat releases at knock onset.

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.

Reaction Activation Temperature

Fuel consumption reaction activation temperature,

T_{c, a c t}

in Eqn. (4019).

Reaction Fuel Exponent

Ignition reaction fuel exponent,

b_{f}

in Eqn. (4019).

Reaction Oxygen Exponent

Ignition reaction oxygen exponent,

b_{o}

in Eqn. (4019).

Reaction PreExp Factor

Ignition reaction pre-exponential factor,

A

in Eqn. (4019).

Materials and Methods

Cetane/Octane Number: Specifies a constant value for the cetane number $C N$ in Eqn. (4020), or octane number $R O N$ in Eqn. (4021).

Monitors

Yigi: Ignition progress variable, $Y_{i g i}$ in Eqn. (4022).

Field Functions

Ignition Progress Variable: $Y_{i g i}$ in Eqn. (4022).