Jacques Vandooren

Experimental investigation of methanol oxidation in flames: Mechanisms and rate constants of elementary steps

Using molecular beam sampling coupled with mass spectrometric analysis, the detailed mechanisms of lean methanol flames burning at 40 Torr have been investigated. About 70% of the fuel molecules are consumed by reaction with hydroxyl radical and 30% by reaction with hydrogen atom. The main product is CH2OH (or CH3O radical). This conclusion is reinforced by the low value of chemi-ionization observed for these systems. The CH2OH radicals react further, principally with the molecular oxygen. According to the proposed mechanism, one molecule of formaldehyde is produced per molecule of methanol consumed. The occurrence of electronically excited CH2O (Emeleus cool flame bands) has been detected and attributed to highly exothermic reactions between CH2OH and O, H, or OH radicals. The formaldehyde reacts either in a reaction with radicals, mainly OH, or disappears in a bimolecular decomposition process which is responsible for the necessary increase of the number of species in the flame front. The rate constants in cm3/mole.s derived for the following elementary steps: CH3OH+H→CH2OH+H2 k1=3.4 1013 exp(−2600/RT) CH3OH+OH→CH2OH+H2O k2=4.8 1013 exp(−4500/RT) CH2OH+O2→H2CO+HO2 k19=1 1014 exp(−5000/RT) CH2O+M→H2+CO+M k9=2.5 1014 exp(−29000/RT).

Essential Features in the Chemistry of Burning Systems Dissociation Reactions

Abstract A direct stiffness method of analyzing the elastic ftexural-torsional buckling of rigid-jointed plane frames composed of l-section members and subjected to in-plane loads is presented. The in-plane stiffness matrix and the fixed-end resultants are obtained from the member stiffness matrices derived from the in-plane differential equations. These member stiffness matrices are assembled and solved, and their solutions are used to linearize the flexural-torsional buckling equations. The out-of-plane member stiffness matrices are then obtained numerically from the buckling equations by the method of finite integrals. The out-of-plane frame -stiffness matrix is assembled, and the critical loads are obtained when its determinant is zero. A computer program is developed which carries out either a first- or second-order in-plane analysis, and then determines the flexural-torsional buckling loads. The effects of in-plane deformations prior to buckling can be included. Very good agreement is obtained betwe...