Hot particle ignition of methane flames

• Published in: Proceedings of the Combustion Institute Vol. 29; no. 2; pp. 1605 - 1612
• Main Authors: Egolfopoulos, Fokion N., Campbell, Charles S., Andac, M. Gurhan
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 2002
• ISSN: 1540-7489; 1873-2704
• DOI: 10.1016/S1540-7489(02)80197-3

Ignition by sparks, glowing embers, or other hot particulate materials presents serious safety hazards.This paper describes a detailed numerical study conducted on the bulk ignition of premixed and non-premixed atmospheric methane flames by hot inert particles in opposed-jet configurations. The coupled conservation equations were solved for both phases along the stagnation streamline, with detailed descriptions of gas-phase chemical kinetics, molecular transport, and radiative heat transfer. Results showed the effects of independently varying the reactant concentrations, strain rate, particle injection orientation, number density, temperature, and velocity. For both premixed and non-premixed configurations, increasing the amount of methane was found to inhibit ignition under all conditions considered. Analysis showed that the H-production is sensitive to the CH 4→CH 3→CH 3O→H path that is strengthened under fuel-lean conditions. While premixed ignition by hot particles was found to be similar to ignition triggered by impinging a mixture on heated air or O 2, differences were observed for non-premixed systems. For nonpremixed particle ignition, increasing the fuel concentration was found to always inhibit ignition, while in non-premixed gas-phase ignition, this inhibiting effect was found to reverse at very low fuel concentrations. This is a result of the noticeably different gas-phase temperature profiles that are induced during particle and gas-phase ignition. Finally, there is a major alteration in the ignition response of non-premixed particle ignition caused by moving the particle seeding from the fuel to the oxidizer side. This is attributed to the different thermal properties of the air and fuel that result in different heat transfer rates between the particles and air, in turn affecting the kinetic paths leading to the production of H radicals.