Carbon conversion mechanism of volatile gas flame based on multi-spectral analysis methods

Abstract

Volatile combustion is a critical process in solid fuel combustion, requiring a deeper understanding of its carbon conversion mechanisms. This study investigates the synergistic effects of different volatile fraction components CH₄, CO, C₂H₄, and H₂ on carbon conversion using a McKenna flat-flame burner. The spatial distribution characteristics of excited-state radicals in flames, namely OH∗, CH∗, and C₂∗, were qualitatively measured using image spectroscopy. Additionally, the final product H₂O concentration and flame temperature were quantitatively determined through Tunable Diode Laser Absorption Spectroscopy (TDLAS). Combined with chemical kinetics simulations, the study reveals the volatile combustion reaction pathways and the synergistic effects of multi-component co-combustion on carbon conversion. The experimental and kinetic analysis results indicate that H₂ promotes CH₂ and CH formation, thereby facilitating the production of C₂∗ and OH∗. C₂H₄ enhances C₂H formation, which promotes the production of CH∗. Additionally, H₂ increases H₂O production and raises temperature in flame, while CO inhibits both. While maintaining consistent combustible carbon content in fuel, H₂ primarily inhibits the carbon conversion from fuel to CO₂ by reducing the pathway proportions involving the main chain reactions HCO and CO, as well as the branch reactions CH₂∗ and CH₂. In contrast, CO and C₂H₄ promote carbon conversion to CO₂ by increasing the pathway proportions of the branch reactions CH₂∗ and CH₂. When multi-component co-combustion, the gain in pathway proportion is influenced by both individual component effects and complex synergistic effects, which may result in various outcomes such as synergistic promotion, synergistic inhibition, or a simple additive effect.