The chemical reactions that occur in combustion simulations can be described by chemical kinetic mechanisms that define the reaction pathways and the associated reaction rates leading to the change in species concentrations. In detailed chemical kinetic mechanisms, the reversible (or irreversible) reactions involving K chemical species can be represented in the general form [15]
 | (2–41) |
The production rate of the k th species in the i th reaction can be written as
 | (2–42) |
where q i is the rate of progress of reaction i.
Ansys Forte uses the Ansys Chemkin chemistry solver. Details of the various types of reactions available in Chemkin can be found in the Chemkin Theory Manual , in these chapters:
Chapter 3: Gas-phase Chemical Rate Expressions:
Chapter 4: Surface Chemical Rate Expressions:
The summation of 
over all the reactions gives the chemical source term
in the species continuity equation (Equation 2–1
) as
 | (2–43) |
Correspondingly, the chemical heat release term in the energy equation is given by
 | (2–44) |
where Q i is the heat of reaction of reaction i at absolute zero,
 | (2–45) |
