TY - JOUR

T1 - Toward improved ion chemistry in flames: revisiting C3H3+ reaction pathways and mechanism validation against mass spectrometric measurements in non-sooting premixed flames of small aliphatic hydrocarbons

AU - Черепанов, Андрей Вячеславович

AU - Kiselev, Vitaly

AU - Dmitriev, Artëm

AU - Шмаков, Андрей Геннадьевич

AU - Князьков, Денис Анатольевич

N1 - This work was supported by Russian Science Foundation (project 23-23-00521).

PY - 2024/4

Y1 - 2024/4

N2 - While the neutral combustion chemistry of hydrocarbon fuels is nowadays relatively well established, there is a growing demand for the reliable kinetic models including ion-molecular reactions. In this work, we present an updated ion chemistry model for the flames of small hydrocarbons. It is built upon the mechanism reported recently (Knyazkov et al., Proc. Combust. Inst., 2023) with the improved reaction subset for C3H3+, a key cation species under fuel-rich conditions. The reaction pathways involving this cation were analyzed using modern predictive W2-F12 quantum chemical calculations. As compared to the original mechanism, which includes the reaction subset for a cyclic C3H3+ isomer only, the updated mechanism is augmented with the reactions of a linear C3H3+ isomer. Moreover, the kinetic parameters of some reactions involving cyclic C3H3+ isomer were modified in accordance with the previous findings reported in the literature. The mechanism with these modifications was validated against the experimental literature data on the cationic structure of premixed burner-stabilized flames of methane and ethylene. We also complemented these values with new data on the premixed flames fueled by ethane, propane, and n-butane at 1 atm. The spatial distributions of the cations were measured by molecular beam mass spectrometry in the flames with the equivalence ratios ϕ=1.0 and 1.5. In contrast to the previous versions, the updated mechanism quantitatively reproduces well the measured mole fraction of C3H3+ in all flames while retaining the same predictive ability for other cations. Apart from this, in the reaction zone of flames, we also experimentally detected many CxHy+ cations not included in the model. Their abundance increases upon the rise of equivalence ratios and the molecular weight of the fuels. The predominance of these cations in the flames results in the late production of H3O+ under fuel-rich conditions not predicted by the model. We also discussed the possible reaction pathways leading to CxHy+ production and the ways for the further improvement of the mechanism.

AB - While the neutral combustion chemistry of hydrocarbon fuels is nowadays relatively well established, there is a growing demand for the reliable kinetic models including ion-molecular reactions. In this work, we present an updated ion chemistry model for the flames of small hydrocarbons. It is built upon the mechanism reported recently (Knyazkov et al., Proc. Combust. Inst., 2023) with the improved reaction subset for C3H3+, a key cation species under fuel-rich conditions. The reaction pathways involving this cation were analyzed using modern predictive W2-F12 quantum chemical calculations. As compared to the original mechanism, which includes the reaction subset for a cyclic C3H3+ isomer only, the updated mechanism is augmented with the reactions of a linear C3H3+ isomer. Moreover, the kinetic parameters of some reactions involving cyclic C3H3+ isomer were modified in accordance with the previous findings reported in the literature. The mechanism with these modifications was validated against the experimental literature data on the cationic structure of premixed burner-stabilized flames of methane and ethylene. We also complemented these values with new data on the premixed flames fueled by ethane, propane, and n-butane at 1 atm. The spatial distributions of the cations were measured by molecular beam mass spectrometry in the flames with the equivalence ratios ϕ=1.0 and 1.5. In contrast to the previous versions, the updated mechanism quantitatively reproduces well the measured mole fraction of C3H3+ in all flames while retaining the same predictive ability for other cations. Apart from this, in the reaction zone of flames, we also experimentally detected many CxHy+ cations not included in the model. Their abundance increases upon the rise of equivalence ratios and the molecular weight of the fuels. The predominance of these cations in the flames results in the late production of H3O+ under fuel-rich conditions not predicted by the model. We also discussed the possible reaction pathways leading to CxHy+ production and the ways for the further improvement of the mechanism.

U2 - 10.1016/j.combustflame.2024.113344

DO - 10.1016/j.combustflame.2024.113344

M3 - Article

VL - 262

JO - Combustion and Flame

JF - Combustion and Flame

SN - 0010-2180

M1 - 113344

ER -