Kinetic modeling for chemiluminescent radicals in acetylene combustion

Abstract

Uma modelagem cinética foi avaliada para reproduzir a quimiluminescência experimental dos radicais excitados OH*, CHO*, CH* e C 2 * formados na combustão de C 2 H 2 /O 2 em uma câmara fechada. Um mecanismo reacional com 37 espécies e 106 reações elementares foi validado para a combustão de C 2 H 2 /O 2 com Φ=1.00 e Φ=1.62, através das medidas de quimiluminescência. Para isso foram incluídas reações de formação e de decaimento dos radicais excitados. As simulações foram realizadas com o pacote KINAL; o programa DIFF foi utilizado para resolver as equações diferenciais ordinárias e o programa ROPA para realizar a análise das velocidades de produção. Houve uma boa concordância entre os perfis de quimiluminescência experimental e simulado de todos os radicais e para ambas reações. Os resultados mostraram que o CH tem um papel central na formação dos radicais. As reações: H + O 2 = OH* + O; CH + O = CHO*; C 2 H + O 2 = CH* + CO 2 e CH 2 + C = C 2 * + H 2 são as principais rotas reacionais para reproduzir os perfis experimentais.Kinetic modeling to reproduce the experimental chemiluminescence of OH*, CHO*, CH* and C 2 * excited radicals formed in C 2 H 2 /O 2 combustion in a closed chamber was evaluated. A reaction mechanism with 37 species and 106 elementary reactions for C 2 H 2 /O 2 combustion at Φ=1.00 and Φ=1.62 was validated through chemiluminescence measurements, where formation and decay reactions of excited radicals are included. KINAL package was used for simulations. Ordinary differential equations were solved by the DIFF program and production rate analysis were acquired by the ROPA program. There was good agreement between experimental and simulated chemiluminescence profiles of all radicals for both combustions. The results showed CH has a meaningful role in the production of excited radicals. Reactions: H + O 2 = OH* + O; CH + O = CHO*; C 2 H + O 2 = CH* + CO 2 and CH 2 + C = C 2 * + H 2 were the main reactions paths used to reproduce the experimental profiles.

Study of the H+O+M reaction forming OH∗: Kinetics of OH∗ chemiluminescence in hydrogen combustion systems

“…In [11] the rate coefficient of reaction (R4) in C 2 H 2 /O 2 system is assumed to be identical to the rate coefficient of the ground state reaction H + O 2 = OH + O. They found through a production rate mechanism that reaction (R4) as a principle path then would contribute to about 90% of the total OH * formation.…”

“…We used a simple analytical approach to quantify signal trapping for our experimental conditions that accounts for the homogeneous luminous and homogeneously absorbing gas mixture within the shock tube (79 mm maximum path length) for all the mixtures used in this study. To quantify signal trapping two OH lines R 1 (7) and R 1 (11) for the R-branch bandhead of the OH A-X (0,0) band were investigated. For both lines the peak maximum leads to a reduction in the detected OH * signal by $10%.…”

Temperature measurements by oh lif and chemiluminescence kinetic modeling for ethanol flames

“…It was built from two models: one for ethanol combustion in a closed chamber, which was validated through chemiluminescent emissions' data 35 and other related to nitrogen chemistry for reburning process to NO reduction in a furnace. 36 To these set of reactions, 20 ones for OH* and CH* non-radiative decays were inserted [42][43][44] although they have been discarded previously. 35,42 Two new reactions proposed for OH* formation in the recent works of Smith et al 45 and Harber and Vandsburger 46 was also considered.…”

“…36 To these set of reactions, 20 ones for OH* and CH* non-radiative decays were inserted [42][43][44] although they have been discarded previously. 35,42 Two new reactions proposed for OH* formation in the recent works of Smith et al 45 and Harber and Vandsburger 46 was also considered. Thermodynamic data for electronically excited species were calculated through FITDAT program of CHEMKIN software package 38 from thermodynamic coefficients of the species in their respective ground states, adding the photon energy, hn, for each radiative transition to the enthalpy of each ground state at 298 K. For CH 2 CN radical the thermodynamic coefficients were also calculated 36 using FITDAT, but the molecular vibrational frequencies were the inputs for fitting procedure.…”

Chemische Konzepte für saubere Abgase

“…Während diese sowie die Verbrennungseffizienz recht gut vorhersagbar sind, erfordert die quantitative Beschreibung der Schadstoffemissionen mehr Aufwand. Grund dafür sind diffizile Verknüpfungen vieler einzelner Elementarschritte in großen, unübersichtlichen Reaktionsnetzwerken (Abbildung 1) 3.…”