9.2.1. Which Model is the Most Appropriate?

The following table is meant as a guide in helping you choose which combustion model is most suitable for your simulation. You are also encouraged to read the following sections, which describe how to set up each model to obtain the most accurate results.

Eddy Dissipation Model

Turbulent

Fast reaction compared to turbulent time scale (high Damköhler number)

Reaction rate dominated by turbulent mixing of reactants or fresh and burned gases (premixed)

Finite Rate Chemistry Model

Laminar or turbulent

If turbulent, reaction rate slow compared to turbulent time scale (low Damköhler number)

Reaction rate dominated by kinetics (chemistry)

Kinetic data for reaction rates required

May need special initialization for flame ignition (temperature dependence of reaction rates)

Combined EDM/FRC Model

Turbulent

Whole range of Damköhler numbers

Kinetic data for reaction rates required

May need special initialization for flame ignition (temperature dependence of reaction rates).

Laminar Flamelet Model

Fast chemistry (high Damköhler number)

Turbulent

Non-premixed

"Fuel" and "Oxidizer" well defined,

Chemistry library required

Burning Velocity Model, BVM (Partially Remixed), (Turbulent Flame Closure)

Turbulent

Premixed or partially-premixed

"Fuel" and "Oxidizer" can be mixed (specify inlet mixture fraction)

Chemistry library required

The Damköhler number is the ratio of flow-time scale to chemical-time scale:

(9–11)