Experimental and kinetic modelling study on the laminar burning velocities of ultra-lean n-heptane flames at atmospheric pressure
(2024) In Combustion and Flame 268.- Abstract
Ultra-lean combustion is a promising strategy for enhancing engine efficiency and reducing pollutant emissions. In the present study, laminar burning velocity, SL, of n-heptane, a key gasoline surrogate component, was measured at 298 K and 1 atm using the heat flux method. The experimental conditions cover ultra-lean conditions with an equivalence ratio as low as 0.5 that have never been reported before for the n-heptane flames, which was achieved through H2 and O2 enrichment, coupled with extended averaging periods to mitigate flame oscillations. The measured SL data, along with evaluated uncertainties in SL, equivalence ratio, and oxygen ratio, were compared with simulations using... (More)
Ultra-lean combustion is a promising strategy for enhancing engine efficiency and reducing pollutant emissions. In the present study, laminar burning velocity, SL, of n-heptane, a key gasoline surrogate component, was measured at 298 K and 1 atm using the heat flux method. The experimental conditions cover ultra-lean conditions with an equivalence ratio as low as 0.5 that have never been reported before for the n-heptane flames, which was achieved through H2 and O2 enrichment, coupled with extended averaging periods to mitigate flame oscillations. The measured SL data, along with evaluated uncertainties in SL, equivalence ratio, and oxygen ratio, were compared with simulations using seven widely-used mechanisms. None of the mechanisms accurately reproduce all the present experimental data, and each mechanism shows mixed behaviour under low- and high-xO2 conditions. Comparisons were also made between existing literature and the current n-heptane + air SL results under different equivalence ratios at 1 atm, and a σ function was employed to quantitatively assess the standard deviation of the simulation results using each mechanism. By sensitivity analysis, the importance of the C0-C1 reactions in predicting ultra-lean n-heptane flame behaviour was recognized, contrasting with the dominance of reactions involving C2-C3 species under stoichiometric and fuel-rich conditions. Together with the comparison with the literature ultra-lean C0-C1 SL data, discrepancies between simulation outcomes and experimental data were attributed to inaccuracies in rate expressions for several small-molecule reactions, particularly concerning their temperature dependencies. It is recommended that mechanism updates consider the ultra-lean flame characteristics of small molecules like syngas and methane to enhance predictive accuracy.
(Less)
- author
- Han, Xinlu LU ; Weng, Wubin LU ; He, Yong ; Wang, Zhihua and Konnov, Alexander A. LU
- organization
- publishing date
- 2024-10
- type
- Contribution to journal
- publication status
- published
- subject
- keywords
- Heat flux method, Kinetic modelling, Laminar burning velocity, N-heptane, Ultra-lean
- in
- Combustion and Flame
- volume
- 268
- article number
- 113613
- publisher
- Elsevier
- external identifiers
-
- scopus:85198608310
- ISSN
- 0010-2180
- DOI
- 10.1016/j.combustflame.2024.113613
- language
- English
- LU publication?
- yes
- id
- df54c3d1-e0ae-4e96-ba42-92c0aa09b860
- date added to LUP
- 2024-09-02 15:48:31
- date last changed
- 2024-09-02 15:49:41
@article{df54c3d1-e0ae-4e96-ba42-92c0aa09b860,
abstract = {{<p>Ultra-lean combustion is a promising strategy for enhancing engine efficiency and reducing pollutant emissions. In the present study, laminar burning velocity, S<sub>L</sub>, of n-heptane, a key gasoline surrogate component, was measured at 298 K and 1 atm using the heat flux method. The experimental conditions cover ultra-lean conditions with an equivalence ratio as low as 0.5 that have never been reported before for the n-heptane flames, which was achieved through H<sub>2</sub> and O<sub>2</sub> enrichment, coupled with extended averaging periods to mitigate flame oscillations. The measured S<sub>L</sub> data, along with evaluated uncertainties in S<sub>L</sub>, equivalence ratio, and oxygen ratio, were compared with simulations using seven widely-used mechanisms. None of the mechanisms accurately reproduce all the present experimental data, and each mechanism shows mixed behaviour under low- and high-x<sub>O2</sub> conditions. Comparisons were also made between existing literature and the current n-heptane + air S<sub>L</sub> results under different equivalence ratios at 1 atm, and a σ function was employed to quantitatively assess the standard deviation of the simulation results using each mechanism. By sensitivity analysis, the importance of the C0-C1 reactions in predicting ultra-lean n-heptane flame behaviour was recognized, contrasting with the dominance of reactions involving C2-C3 species under stoichiometric and fuel-rich conditions. Together with the comparison with the literature ultra-lean C0-C1 S<sub>L</sub> data, discrepancies between simulation outcomes and experimental data were attributed to inaccuracies in rate expressions for several small-molecule reactions, particularly concerning their temperature dependencies. It is recommended that mechanism updates consider the ultra-lean flame characteristics of small molecules like syngas and methane to enhance predictive accuracy.</p>}},
author = {{Han, Xinlu and Weng, Wubin and He, Yong and Wang, Zhihua and Konnov, Alexander A.}},
issn = {{0010-2180}},
keywords = {{Heat flux method; Kinetic modelling; Laminar burning velocity; N-heptane; Ultra-lean}},
language = {{eng}},
publisher = {{Elsevier}},
series = {{Combustion and Flame}},
title = {{Experimental and kinetic modelling study on the laminar burning velocities of ultra-lean n-heptane flames at atmospheric pressure}},
url = {{http://dx.doi.org/10.1016/j.combustflame.2024.113613}},
doi = {{10.1016/j.combustflame.2024.113613}},
volume = {{268}},
year = {{2024}},
}