A study of homogeneous methanol oxidation kinetics using CSP

The homogeneous oxidation of methanol in air at constant pressure is examined using data generated by the method of computational singular perturbation (CSP). At any moment in time, the number of exhausted fast modes and the radicals (sometimes called the intermediaries) are computationally identified. The participation index, which quantifies the participation of any elementary reaction to an equations of state of the radicals, along with the importance index, which quantifies the importance of any elementary reaction to a particular species of interest, are computed and used to assess the sensitivities of the solution to the reaction rate constants. Every elementary reaction is classified so that it either belongs to the equilibrated set which contains fast reactions already equilibrated among themselves, and/ or the rate-controlling set which contains reactions controlling the current rate of activities, or neither of the above sets—in which case it is superfluous. A number of numerical experiments were performed to verify the assessments: (a) the relative effectiveness of the reaction rate constants of two reactions (#16, #160) in breaking up the fuel indicated by the importance index is verified, (b) that fuel breakup in an early time period can actually be slowed down by increasing the reaction rate constants of certain fuel breakup reactions (#156, #159) is verified. Numerical experiments also showed that species identified as radicals responded instantly to sudden changes in reaction rates, while the non-radicals responded more smoothly. The overall response of the unknowns to perturbations is always consistent with the CSP-derived effective stoichiometric coefficients. In addition, a minimum set of species is constructed with the help of the CSP data. This minimum set, which trims the original full set of 30 species to 15 species, generates numerical solutions in excellent agreement with solutions obtained with the full set.