Roles of inhibitors in global gas-phase combustion kinetics

• Published in: Proceedings of the Combustion Institute 2002, Vol.29 (1), p.337-344
• Main Author: Saso, Yuko
• Format: Article
• Language: English
• ISSN: 1540-7489; 1873-2704
• DOI: 10.1016/S1540-7489(02)80045-1

The roles of inhibitors in the global kinetics of methane combustion were investigated computationally, by employing the Arrhenius equation to express the global rate constant. When the concentrations of the fuel and the oxidizer in a combustible mixture are kept constant, the global reaction rate is controlled by the flame temperature T g , the global frequency factor A, and the global activation energy E a. Changes in A and E a with the additions of various inhibitors were estimated using the relationship between these parameters and the laminar burning velocity. The inhibitors investigated are He, CO 2, CF 4, CHF 3, C 3HF 7, CF 3Br, CF 3I, NaOH, and Fe(CO) 5. The global kinetic parameters were found to vary according to the inhibitors' actions, physical, non-catalytic scavenging, and catalytic scavenging. That is, while He and CO 2 caused negligible changes in both A and E a, CHF 3 and C 3HF 7 caused a significant reduction in A without a remarkable change in E a. In contrast, CF 3Br, CF 3I, NaOH, and Fe(CO) 5 caused a noticeable increase in E a. Although the increase in E a seems to be a general characteristic of catalytic scavengers, its magnitude showed complicated variation due to many factors, including combustion promotion at higher temperatures and the saturation effect. Using the variation in E a, the present study demonstrates the roles of inhibitor thermochemistry and recombination kinetics in catalytic flame inhibition.