Flux Projection
Tree Method for Mechanism Reduction
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Abstract
Merits and demerits of the directed
relation graph (DRG) method
are analyzed. On the basis of these analyses, a flux projection tree
(FPT) method for mechanism reduction is proposed. A tree-type structure
is constructed in FPT based on the contribution of each species to
the global flux; that is, the importance of each species is quantified
by normalized projection of its participation flux vector upon the
total species flux vector. Because a tree-type structure is simpler
than a graph-type structure, FPT tends to be more efficient than DRG
and path flux analysis (PFA) in computation. Additionally, the significance
of each species in a mechanism is estimated on the basis of its contribution
to the global species flux, instead of its contribution to the flux
of a single species in a pre-chosen important species set, as in DRG
and PFA. Thus, a reduced model obtained by FPT is more accurate in
most cases. Detailed mechanisms for oxidation of ethylene, <i>n</i>-heptane, and PRF50 were reduced with FPT, and the reliability
of the resulting skeletal mechanisms is comparable or even better
than that of the skeletal mechanisms obtained by DRG or PFA with similar
size. Because of its high efficiency, FPT can be used as the first-step
reduction method or on-the-fly mechanism reduction approach in numerical
simulations of reaction flow