C{sub 1}/C{sub 2} chemistry in fuel-rich post-flame gases: Detailed kinetic modelling
- Univ. of Sydney (Australia). Dept. of Chemical Engineering
Measurements have been made of concentrations of hydrocarbons from C{sub 1} to C{sub 4} in sooting and non-sooting postflame gases at atmospheric pressure. The experimental results have been compared with the predictions of the detailed Miller-Melius mechanism for the interactions of hydrocarbons up to C{sub 6}. The modelling of the postflame behavior of small hydrocarbons is extremely sensitive to the rates and mechanisms of oxidation of C{sub 2}H{sub 2} and CH{sub 3} by OH. The Miller-Melius mechanism underpredicts the rates of both processes by a large amount but needs modification of only a few reactions for it to be accurate for postflame hydrocarbons up to at least C{sub 4}. The oxidation of acetylene by OH is effectively irreversible and may be described simply as C{sub 2}H{sub 2} + OH {leftrightarrow} CH{sub 2}CO + H with k{sub 113} = 1.1 {times} 10{sup 13} exp({minus}7170 cal/mol/RT) cm{sup 3} mol s ({+-}30%). The underprediction of the rate of CH{sub 3} oxidation in the Miller-Melius mechanism derives mainly from the reversibility of the process under postflame conditions. A substantial increase in the rate constant assumed for the unimolecular decomposition of CH{sub 2}OH is indicated. The rate constant for CH{sub 3} + OH {leftrightarrow} CH{sub 2}OH + H is found to be k{sub 32} = 1.9 {times} 10{sup 13} cm{sup 3} mol s ({+-}30%). An additional process is responsible for substantial destruction of C{sub 1}`s in the richest flames. This is suggested to be CH{sub 2}CO + CH{sub 3} {leftrightarrow} C{sub 2}H{sub 5} + CO with k{sub 220} = 5 {times} 10{sup 12} cm{sup 3} mol s ({+-}50%). The modelling of the concentrations of the higher hydrocarbons is governed by a tendency towards partial equilibria with the C{sub 1}`s and C{sub 2}`s. Despite good agreement between measurement and prediction, the present results do not allow a detailed assessment of the mechanistic details in the model.
- OSTI ID:
- 93239
- Report Number(s):
- CONF-940711-; TRN: IM9537%%283
- Resource Relation:
- Conference: 25. international symposium on combustion, Irvine, CA (United States), 31 Jul - 5 Aug 1994; Other Information: PBD: 1994; Related Information: Is Part Of Twenty-fifth symposium (international) on combustion; PB: 1838 p.
- Country of Publication:
- United States
- Language:
- English
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