Complex CSP for chemistry reduction and analysis

The method of computational singular perturbation for the analysis and redu ction of complicated chemical mechanisms has been extended to the complex e igensystem. The characteristic time scale for each species was defined by u sing the time scales of the independent modes weighted by radical pointers, and the time scale of each species normalized by a characteristic time sca le of the system was used as a criterion in determining the quasi-steady-st ate species. Furthermore, for oscillatory modes the radical pointer and the importance index of the previous computational singular perturbation theor y were redefined. Results show that the time scales of chemical species cha nge dramatically and non-monotonically, and the oscillatory modes appear fr equently in large chemical reaction mechanisms. The present method was then employed to generate a 4-step and a 10-step reduced mechanism for the high -temperature H-2/air and CH4/air oxidation, respectively. The validity of t hese reduced mechanisms were evaluated based on the responses of the perfec tly stirred reactors and the one-dimensional planar propagating premixed fl ames. Comparisons between the reduced and detailed chemistries over a wide range of pressures and equivalence ratios show good agreement on the flame speed, flame temperature, and flame structure. A software package based on the present algorithm was compiled to generate reduced mechanisms for compl ex chemical mechanisms. The validity and efficiency of the present algorith m is demonstrated. (C) 2001 by The Combustion Institute.