Specifying Multiple Devolatilizing Species for Combusting Particles — Lesson 2

How do you specify multiple devolatilizing species for combusting particles in Fluent software, as you can select only single species as the devolatilizing species?

Sometimes it is required to specify the multiple species as the evaporating species in DPM. This is one of the requirements for volatile breakup while modeling coal combustion or gasification. However, in Fluent software, only one species is allowed as the evaporating species.

The above limitation can be worked around using a pseudo species and a pseudo reaction. Fist, define a pseudo species (e.g., volatile) in the mixture. Specify this species as the evaporating species. Then, define a pseudo reaction (e.g., volatile breakup reaction). The reactant of this reaction is the pseudo species, and the products would be the required multiple species of the volatile breakup.

This reaction should be faster than other reactions included in the model so that the species evolved due to volatile breakup are not limiting the other reactions. This can be done by specifying large pre-exponential factor for the laminar finite rate model or large mixing rate constant, A for the eddy dissipation model.

Molecular weight and standard state enthalpy for the pseudo species can be adjusted so that no heat is produced or consumed in the volatile breakup reaction.