Experimental study of the influence of hydrogen as a fuel additive on the formation of soot precursors and particles in atmospheric laminar premixed flames of methane. (1st March 2021)

• Record Type: Journal Article
• Authors: Do, Hong-Quan; Tran, Luc-Sy; Gasnot, Laurent; Mercier, Xavier; El Bakali, Abderrahman
• Is Part Of: Fuel. Volume 287(2021)
• Publication Date: 2021-03-01
• Subjects: Hydrogen -- Methane -- Premixed flame -- PAHs -- Soot nucleation -- Soot; Fuel -- Periodicals; Coal -- Periodicals; Coal; Fuel; Periodicals; 662.6
• DOI: 10.1016/j.fuel.2020.119517
• Languages: English
• ISSNs: 0016-2361

Abstract

Highlights: Impact of H2 is investigated in atmospheric sooting premixed methane flame. H2 insignificantly modifies the maximum mole fraction of aliphatic species. Hydrogen strongly influences aromatics and soot volume fractions. Hydrogen has no effect on the aromatics enabling the inception of soot particles. Abstract: We report here the experimental investigation of lightly sooting methane premixed flames with and without hydrogen. Two different approaches were considered to introduce hydrogen in the methane flame, either by keeping the total gas flow rate constant or not. Speciation data were obtained using a set of analytical tools including Gas Chromatography, Fourier-Transform Infrared Spectroscopy, Jet-Cooled Laser-Induced Fluorescence, Laser-induced Incandescence coupled with Cavity Ring-Down Spectroscopy. The results include mole fraction profiles of gaseous species (C0 -C16 ) and soot volume fraction ( fv ) measured in all studied flames. These results demonstrate that the introduction of hydrogen to the flame insignificantly impacts the maximum mole fractions of small species (6 ) while it strongly influences the concentration of aromatics and fv . Interestingly, this influence is different, depending on how hydrogen was added to the reference methane flame. An excellent linear relationship between pyrene squared concentration [C16 H10 ] 2 and fv is demonstrated in all investigated flames. Moreover, hydrogen addition changes the slope of these data indicating a non-negligible impact of hydrogen on the rate of the soot nucleation process. These data and the observed linearity between fv and [C16 H10 ] 2 supports therefore the idea of a soot nucleation step initiated by a dimerization process implicating moderate-size polyaromatic hydrocarbons (PAHs) as pyrene. Finally, we note that PAH mole fractions at the beginning of soot formation highlight similar values regardless the flame conditions, which suggests that the inception of the soot formation might be dependent of a minimum concentration threshold of aromatic precursors required to initiate the soot nucleation process.