Internal Combustion Engines

In an internal combustion engine (ICE), for example a gasoline engine, the process of combustion takes place in a cylinder (or cylinders) within the engine. The working fluid is a fuel and oxidizer mixture (usually air), which reacts to form combustion products.

Currently, there are three combustion models that you can use to simulate combustion within an internal combustion engine:

ECFM-3Z or ECFM-CLEH: Only available when using Simcenter STAR-CCM+ In-cylinder. Provides an efficient method for simulating internal combustion engines without the expense of modeling complex chemistry.
Complex Chemistry: Provides a more accurate, yet more expensive, method for simulating internal combustion engines compared to the ECFM models.


Model	Ignition		Soot	NOx / Emissions
ECFM-3Z ECFM-CLEH	FI Spark Ignition Subgrid Spark Ignition ISSIM Spark Ignition ECFM Standard Auto-Ignition ECFM TKI Auto-Ignition		The Soot Two-Equation model is built-in. The Soot Moments model is also available.	The NOx Thermal model is built-in for ECFM-3Z and an optional model for ECFM-CLEH. The following NOx emission models are also available: NOx Fuel NOx Prompt NOx NORA
Complex Chemistry	Subgrid Spark Ignition Fixed Temperature Ignitor ISSIM Spark Ignition		The following soot models are available: Soot Moments Soot Two-Equation	The following NOx emission models are available: NOx Fuel NOx Prompt NOx Thermal

ECFM-3Z

The Extended Coherent Flame Model Three Zone (ECFM-3Z) model is capable of simulating the complex mechanisms of turbulent mixing, flame propagation, diffusion combustion, and pollutant emission that characterize modern internal combustion engines. It can also be used for in-cylinder analysis in a multi-injection environment and for multi-cycle simulations. There are four major components to the mathematical structure of the ECFM-3Z model:

Mixing model
Flame propagation model
Post-flame and emissions model
Spark ignition model and auto-ingition/knock models

In the diagram above, EGR denotes exhaust gas recirculation, $Σ$ denotes the flame surface, $U_{L}$ is laminar flame speed (denoted elsewhere as $S_{l}$ ), $T_{u}$ and $T_{b}$ are the unburnt and burnt temperatures respectively, and $Y_{u}$ and $Y_{b}$ are the unburnt and burnt mass fractions.

ECFM-CLEH

ECFM-CLEH is a combustion model in which burning rates are limited by a thermodynamic equilibrium given by complex chemistry. In this model, the computational cells are split into four zones: unmixed, premixed, diffusion, and post-oxidation. This leads to the need for distinguishing four combustion modes: auto-ignition, flame propagation, diffusion combustion, and post-oxidation. The fuel in these zones is then distinguished as:

Fuel Premixed
Fuel Unmixed
Fuel Diffusion
Fuel Post-oxidation

The unmixed and premixed zones are defined for the unburnt gases only, whereas the diffusion and post-oxidation zones are defined only for the burnt gases.

Complex Chemistry

See Reacting Species Transport: Complex Chemistry.

Ignition Models

Spark Ignition

Currently, the following spark ignition models are available with the ECFM models:

FI Spark Ignition
ISSIM Spark Ignition
Subgrid Spark Ignition

See Spark Ignition Models Reference.

Auto-Ignition

Currently, the following auto-ignition models are available with the ECFM models:

ECFM Standard Auto-Ignition
ECFM TKI Auto-Ignition

See Auto-Ignition Models Reference.