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Mechanism reduction via principal component analysis
Author(s) -
Brown Nancy J.,
Li Guoping,
Koszykowski Michael L.
Publication year - 1997
Publication title -
international journal of chemical kinetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.341
H-Index - 68
eISSN - 1097-4601
pISSN - 0538-8066
DOI - 10.1002/(sici)1097-4601(1997)29:6<393::aid-kin1>3.0.co;2-p
Subject(s) - principal component analysis , chemistry , combustion , combustor , equivalence (formal languages) , mechanism (biology) , reaction mechanism , stoichiometry , reduction (mathematics) , thermodynamics , biological system , mathematics , statistics , physics , organic chemistry , geometry , discrete mathematics , quantum mechanics , biology , catalysis
Principal component analysis, an advanced technique of sensitivity analysis, has been used to determine reduced mechanisms that can model species and temperature profiles in Plug Flow Reactors (PFR), Premixed Laminar Flames (PLF), and Perfectly Stirred Reactors (PSR) for two H 2 /air and two CH 4 /air mechanisms over a range of input parameters including initial temperature, equivalence ratio, and residence time. The results show that principal component analysis can be used effectively to reduce a comprehensive mechanism that contains unimportant reactions to a reduced mechanism that contains necessary and sufficient reactions. The accuracy of a reduced mechanism determined from principal component analysis can be easily controlled by carefully selecting reduction criteria. For the conditions chosen here, namely the requirement that radical profiles computed with reduced and comprehensive mechanisms agree to within 5%, substantial reductions were not achieved. Principal component analysis is able to resolve the influence of stoichiometry, combustor type, and mechanism on mechanism reduction. The two H 2 /air mechanisms were each reduced to mechanisms that can model all the cases considered, and the extent of reduction in each was very similar and modest. For H 2 /air chemistry, equivalence ratio had little effect on reduction. Combustor type was slightly more influential with the number of required reactions decreasing from PFR to PLF to PSR combustion. Relative to the H 2 /air system, principal component analysis of the CH 4 /air system is more difficult because of mechanism size. For CH 4 /air combustion, if we consider all equivalence ratios, PLFs require the most reactions, if individual equivalence ratios are examined, PFRs require the greatest number of reactions. Combustor type influences mechanism reduction substantially because of the different couplings between the fluid mechanics and chemistry. In H 2 /air combustion rich combustion required the fewest reactions and in CH 4 /air, it required the most. Reduction must be achieved by considering the entire mechanism since reactions interact in concert, for example, reactions unimportant in one CH 4 mechanism are often important in the other. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 393–414, 1997.