Influence of molecular hydrogen on acetylene pyrolysis: Experiment and modeling

Aghsaee, M.; Dürrstein, Steffen H.; Herzler, Jürgen; Böhm, Heidi; Fikri, Mustapha; Schulz, Christof

doi:10.1016/j.combustflame.2014.03.012

Cited by 17 publications

(6 citation statements)

References 37 publications

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“…The addition of non-or low-sooting tendency fuels in conventional hydrocarbons has long been regarded as a potential approach. Previous laboratory-scale studies demonstrated that the addition of hydrogen (H2) could inhibit soot formation in shock tubes [5][6][7][8], laminar premixed flames [9,10], coflow diffusion flames [11][12][13][14][15][16][17], as well as counterflow diffusion flames [18,19]. The suppression of soot emissions through the addition of H2 has also been reported under practical combustion conditions, such as in internal combustion engines [20][21][22] and turbulent non-premixed flames [23].…”

Section: Introductionmentioning

confidence: 95%

Chemical effects of hydrogen addition on soot formation in counterflow diffusion flames: Dependence on fuel type and oxidizer composition

Yan

Wang

et al. 2020

Combustion and Flame

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We experimentally studied and kinetically modeled the effects of hydrogen addition on soot formation in methane and ethylene counterflow diffusion flames (CDFs). To isolate the chemical effects of hydrogen in such flames, we also ran a set of experiments on flames of the same base fuels but with the addition of helium. Specifically, we measured the soot volume fractions of the flames using the planar laser-induced incandescence technique. We simulated detailed sooting structures by coupling the gas-phase chemistry with the polycyclic aromatic hydrocarbon (PAH)-based soot model, using a sectional method to resolve the soot particle dynamics. Our experimental and numerical results show that hydrogen chemically inhibits soot formation in ethylene CDFs. While in methane flames, it is interesting to observe that the difference in soot production between the hydrogen-and helium-doped cases became much smaller when the oxygen concentration in the oxidizer stream (XO) was reduced.This suggests that for methane CDFs the chemical soot-inhibiting effects of hydrogen was highly dependent on oxidizer composition (i.e., XO). Explanations are provided through detailed kinetic analysis concerning the effects of hydrogen addition on the growth of PAH, soot inception, and soot surface growth processes. Our results suggest that hydrogen's chemical role in soot formation not only depends on fuel type (ethylene or methane), it also may be sensitive to oxidizer composition.

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Section: Introductionmentioning

confidence: 95%

Chemical effects of hydrogen addition on soot formation in counterflow diffusion flames: Dependence on fuel type and oxidizer composition

Yan

Wang

et al. 2020

Combustion and Flame

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“…The obtained progress in simulations of concentration profiles of C 4 H 2 , H 2 CCCCH, C 6 H 2 and i-C 4 H 5 measured in shock tubes [67][68][69][70] and laminar flames [71][72][73] is shown in Figures 4-6 and Figures S4-1-7 of Supplement-4. At the same time, the Model-2 and final Model match concentrations of C 2 H and main reaction products equally well, showing that the modifications, performed for the PAH precursors, did not disturb the earlier accomplished quality of the fuel decomposition and oxidation process.…”

Section: 1small Pah Precursorsmentioning

confidence: 99%

“…The revision and analysis of the production/consumption of H 2 CCCH, C 4 H 2 , C 4 H 4 and i-C 4 H 5 was carried out on the species profiles measured in shock tubes [67][68][69][70], laminar flames [19,[71][72][73] and flow reactors [31,74,75], Table S3-1, Supplement-3. A summary of the species measured in those experiments is provided in Table 3, showing that the main investigated species are products of acetylene oxidation and pyrolysis.…”

Section: Model-2 Validation and Improvement Of Concentration Profile mentioning

confidence: 99%

“…As we did not find other error analyses, we assigned this uncertainty to all of the experimental concentration profiles from PFR studies [31,74,75], which were measured with the similar methodology and gas chromatography. For the concentration profiles from the shock tube data [67][68][69][70] uncertainty factor of 2 has been assumed. For the laminar flame data [19,[71][72][73] an error of about 30% was assumed based on the empirical rules described in [6].…”

Section: Model-2 Validation and Improvement Of Concentration Profile mentioning

confidence: 99%

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A modelling study of acetylene oxidation and pyrolysis

Slavinskaya

Mirzayeva

Whitside

et al. 2019

Combustion and Flame

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This study initiates the gradual upgrade of the DLR reaction database. The upgrade plan has two main steps: an optimisation of the C 1-C 4 oxidation chemistry and a revision of the polyaromatic hydrocarbon (PAH) formation sub-mechanism based thereupon. The present paper reports the main principles applied to model improvements and results obtained for the acetylene (C 2 H 2) oxidation sub-mechanisms. The principle acetylene oxidation reactions have been revised as well as the detailed chemistry of important intermediates, i.e. methylene, ethynyl, vinylperoxy radical and also diacetylene, vinylacetylene and higher diacetylenes, important for PAH formation. The uncertainty intervals of the studied reactions were statistically evaluated, providing general bounds for the performed modifications to reaction rate coefficients. The first stage of the presented update was performed through revision of the thermochemical data and model optimisation on ignition delay data and laminar flame speed data, since they exhibit lower uncertainty in comparison to species profile data. The final model optimization was obtained through simulations of concentration profiles measured in shock tubes and laminar flames for improvement of the reaction paths and rate coefficients related to acetylene pyrolysis and PAH precursor formation. Approximately 500 data points were analysed. The updated reaction mechanism predicts all simulated experimental data, also not included in the optimisation loop data prom plug flow and jet-stirred reactors, either with good or satisfactory agreement. It was found that the vinylperoxy radical formation and consumption dictate the reaction progress at low temperatures. The performed study clearly determined that acetylene combustion proceeds through the strongly coupled reaction paths of fuel oxidation and PAH precursor formation; the same species are involved in these parallel processes. Therefore, the self-consistent reaction model for acetylene combustion could be obtained only by an optimisation performed on the experimental dataset encompassing both processes.

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“…Knorre et al (1996) have obtained the similar effects of hydrogen addition on soot formation from acetylene and ethylene, and found that hydrogen affects soot precursors formation at the beginning of the pyrolysis process. Aghsaee et al (2014) have studied influence of molecular hydrogen on acetylene pyrolysis using a shock tube with TOF-MS. They have concluded that reactions of H atom in the early stage of soot formation have a significant impact on kinetics of acetylene and polyacetylenes.…”

Section: Introductionmentioning

confidence: 99%

Effects of hydrogen addition on soot formation in iso-octane pyrolysis behind a reflected shock wave

Murata

Ishii

2016

JTST

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In the present paper, soot formation process was studied in pyrolysis of iso-octane added hydrogen highly diluted with argon in the temperature range of 1800-2600 K and in the pressure of 1.2 ± 0.1 MPa behind a reflected shock wave. As a test gas, 1% iso-C8H18 + 0-1% H2 diluted with Ar was used. Soot formation process was characterized by induction time and soot volume fraction, which was measured from laser light extinction measurement. In addition, time history of soot particle temperature was calculated based on spectral dependence of monochromatic emissive power from thermal radiation from the soot particles. The experimental results show that soot formation has bell-shaped temperature dependence exhibiting maximum at 2000 K with and without hydrogen addition. Adding hydrogen to iso-octane decreases soot volume fraction clearly for an initial ambient temperature T5 = 1800 K. Additionally, hydrogen addition prolongs induction time for T5 = 1800 K and 2000 K. Soot particle temperature TP is higher than T5 by about 200-400 K except for around 1800 K in the case of hydrogen addition. Consequently, soot formation is obviously suppressed for T5 = 1800 K, while no significant effects of hydrogen addition can be seen for T5 = 2000 K and 2500 K.

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Influence of molecular hydrogen on acetylene pyrolysis: Experiment and modeling

Cited by 17 publications

References 37 publications

Chemical effects of hydrogen addition on soot formation in counterflow diffusion flames: Dependence on fuel type and oxidizer composition

Chemical effects of hydrogen addition on soot formation in counterflow diffusion flames: Dependence on fuel type and oxidizer composition

A modelling study of acetylene oxidation and pyrolysis

Effects of hydrogen addition on soot formation in iso-octane pyrolysis behind a reflected shock wave

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