MECHANISM REDUCTION VIA PRINCIPAL COMPONENT ANALYSIS

Principal component analysis, an advanced technique of sensitivity ana lysis, has been used to determine reduced mechanisms that can model sp ecies and temperature profiles in Plug Flow Reactors (PFR), Premixed L aminar Flames (PLF), and Perfectly Stirred Reactors (PSR) for two H-2/ air and two CH4/air mechanisms over a range of input parameters includ ing initial temperature, equivalence ratio, and residence time. The re sults show that principal component analysis can be used effectively t o reduce a comprehensive mechanism that contains unimportant reactions to a reduced mechanism that contains necessary and sufficient reactio ns. The accuracy of a reduced mechanism determined from principal comp onent analysis can be easily controlled by carefully selecting reducti on criteria. For the conditions chosen here, namely the requirement th at radical profiles computed with reduced and comprehensive mechanisms agree to within 5%, substantial reductions were not achieved. Princip al component analysis is able to resolve the influence of stoichiometr y, combustor type, and mechanism on mechanism reduction. The two H-2/a ir mechanisms were each reduced to mechanisms that can model ail the c ases 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 n umber of required reactions decreasing from PFR to PLF to PSR combusti on. Relative to the H-2/air system, principal component analysis of th e CH4/air system is more difficult because of mechanism size. For CH4/ air combustion, if we consider all equivalence ratios, PLFs require th e most reactions, if individual equivalence ratios are examined, PFRs require the greatest number of reactions. Combustor type influences me chanism reduction substantially because of the different couplings bet ween the fluid mechanics and chemistry. In H-2/air combustion rich com bustion required the fewest reactions and in CH4/air, it required the most. Reduction must be achieved by considering the entire mechanism s ince reactions interact in concert, for example, reactions unimportant in one CH, mechanism are often important in the other. (C) 1997 John Wiley & Sons. Inc.