Kinetic study of the effect of sub-atmospheric conditions on the laminar burning velocity of high C₂H₆ content natural gas mixtures

Abstract

The laminar burning velocity (S_L) was measured at sub-atmospheric pressure (0.84 atm) and an environmental temperature of 295 ± 2 K for two high C₂H₆ content fuel mixtures, 75% CH₄ – 25% C₂H₆ (mixture M1), and 50% CH₄ – 50% C₂H₆ (mixture M2), as well as the pure constituent fuels. The equivalence ratios for the experiments ranged between 0.8 and 1.4. Numerical calculations predicting S_L were performed using 3 detailed reaction mechanisms, finding GRI-Mech 3.0 to achieve the best agreement at the pressure conditions evaluated. The pre-exponential factor of reaction H + O₂= O + OH (R38) was modified in order to improve the numerical results at sub-atmospheric conditions. Kinetic analysis by means of the defined reaction factor ($F_{\text{R},i}^{\pm j}$) was carried out to identify the mechanism for S_L changes at sub-atmospheric conditions. According to the experimental results, S_L increased by 15.9% and 26.3% for mixtures M1 and M2, respectively, at 0.84 atm as compared to 1.0 atm. The reaction pathways elaborated employing F_R indicate that the increase in S_L at sub-atmospheric conditions is caused by increased CH₃ radical production by reaction C₂H₅+ H = 2CH₃ (R159), which increases the formation of H radical through reactions O + CH₃= H + CH₂O (R10) and O + CH₃= H + H₂+ CO (R284). The recombination reactions associated with the production of CH₄ and C₂H₆ also contribute to S_L increases at sub-atmospheric conditions.

KEYWORDS:

• Laminar burning velocity
• sub-atmospheric conditions
• natural gas
• ethane
• kinetic analysis

Acknowledgment

The authors gratefully acknowledge to Colombia Scientific Program, within the framework of Ecosistema Científico (Contract No. FP44842-218-2018), to Minciencias for financing the international mobility programme, to ECOSNORD Colombia-France for researchers, 2018–2022, agreement FP44842-451-2017, and to ‘Division de Investigación y Extensión – DIE’ from Universidad Francisco de Paula Santander Ocaña by financing the project with code 158-19-004.

Disclosure statement

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

Supplemental data

Supplemental data for this article can be accessed at https://doi.org/10.1080/13647830.2021.2016981.

Correction Statement

This article has been republished with minor changes. These changes do not impact the academic content of the article.