Lumped Secondary Mechanism

To be able to model the chemistry of the products formed during the oxidation of an organic molecule, it is necessary to add a "secondary" mechanism (reactions whose reactants are the molecular products formed by the primary mechanism) to the comprehensive primary mechanism. Unfortunatly, to avoid an exponential increase of the size of the generated mechanism, it is impossible to use our method of the primary generation to obtain comprehensive secondary mechanisms for each product formed in the primary mechanism. Therefore, some reduction rules are to be taken into account, but without losing too many chemical informations.

The lumping of primary molecules
For the primary mechanism to be comprehensive, all the isomers of reactants, the primary free radicals and molecules are considered. Therefore, during the mechanism generation of the primary mechanism, EXGAS and the connected softwares use the detailed chemical formulae of all these molecules and free radicals, reactants and products. With the purpose of reducing the number of reactants of the secondary reaction mechanism, which are in fact the molecular products of the primary mechanism, the molecules which have the same molecular formulae and the same functional groups are lumped into one unique species, without distinguishing the different isomers.

The rules for the secondary mechanism generation This "secondary" mechanism is not generated in the same comprehensive way as the primary mechanism. The reactions of the lumped molecules, produced in the primary mechanism, are not elementary steps, but global reactions which produce in the smallest number of steps molecules or radicals whose reactions are included in the C0-C1-C2 reaction base. The secondary mechanism is generated using the rules summarized in the figure below.

Our method for secondary mechanism generation will be improved in the future.