Experimental and numerical study of the laminar burning velocity of syngas in oxyfuel conditions

ABSTRACT

This study evaluates the laminar burning velocity of oxyfuel syngas mixtures. Experimental measurements were performed in standard conditions (298 K and 1 atm), varying the oxyfuel syngas composition (H₂/CO/CO₂/O₂) and equivalence ratio for lean mixtures. The experimental setup uses the heat flux method, validated with CH₄/air and H₂/CO/air measurements. The results were compared with six chemical kinetic mechanisms developed for syngas, aiming at evaluating their predictive capabilities. The mixtures presented a tendency to the appearance of cellular instability in the flame front that was prevented to a certain extent. The CO₂ effects on the flames were explored through numerical analysis, isolating the thermodynamic properties, transport properties, thermal radiation, and chemical effects. The CO₂ or N₂ effect as bath gas in the oxidizer is also evaluated in terms of the laminar burning velocity and mixture’s effective Lewis number. Limitations due to cellular instability were studied, analyzing the influence of fuel dilution and composition on the onset of cellular instability at the flames. The results showed a good prediction of the experimental data by the evaluated kinetic mechanisms. The expected reduction in the laminar burning velocity with CO₂ dilution is primarily due to the effect of carbon dioxide’s thermodynamic properties, followed by its transport properties (when compared to N₂ dilution), chemical effects, and heat losses by radiation. Cellular instability is attenuated with high dilution levels due to the reduction of hydrodynamic instability. At the same time, the increase of the H₂ concentration in the mixture leads to more unstable flames due to both hydrodynamic and thermal-diffusive instability. A laminar burning velocity threshold above which the measurements were not possible due to the effects of cellular instabilities was identified and analyzed in detail.

KEYWORDS:

• Laminar burning velocity
• oxyfuel syngas
• heat flux method
• cellular instability
• chemical kinetic mechanism
• dilution effect

Disclosure statement

No potential conflict of interest was reported by the author(s).

CRediT authorship contribution statement

R.T. Perin: Conceptualization, Methodology, Investigation, Writing – original draft, Formal analysis. I.M. Machado: Investigation, Formal analysis. L.A. Quezada: Investigation, Formal analysis. C.S. Bresolin: Supervision, Writing – review & editing. F.M. Pereira: Conceptualization, Supervision, Writing – review & editing, Resources, Funding acquisition.

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/00102202.2022.2126315