The effects of equivalence ratio on the formation of polycyclic aromatic hydrocarbons and soot in premixed ethane flames

Atmospheric pressure, laminar, premixed, fuel-rich flames of n-heptane/oxygen/argon and n-heptane/oxygenate/oxygen/argon were studied at an equivalence ratio of 1.97 to determine the effects of oxygenate concentration on species mole fractions. The oxygen weight percents in n-heptane/oxygenate mixtures were 2.7 and 3.4. Three different fuel oxygenates (i.e. MTBE, methanol, and ethanol) were tested. A heated quartz micro-probe coupled to an on-line gas chromatography/mass spectrometry has been used to establish the identities and absolute concentrations of stable major, minor, and trace species by the direct analysis of samples, withdrawn from the flames. The oxygenate addition has increased the maximum flame temperatures and reduced the mole fractions of CO, low-molecular-weight hydrocarbons, aromatics, and polycyclic aromatic hydrocarbons. The reduction in mole fractions of aromatic and polycyclic aromatic hydrocarbon species by an increase in oxygenate concentration was more significant. q

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“…10-12). A similar profile for toluene has also been reported for the combustion of n-heptane [15,36] and other hydrocarbon fuels [37].…”

Section: K3supporting

confidence: 79%

Effects of oxygenate concentration on species mole fractions in premixed -heptane flames

İnal

Şenkan

2005

Fuel

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“…Toluene (C 6 H 5 CH 3 ) is utilised in transportation fuels at high levels because of its high energy density and research octane number 12,13 and is also an intermediate in schemes of polycyclic aromatic hydrocarbon (PAH) and soot formation. 14 The primary combustion intermediate associated with toluene is generally considered to be the benzyl radical (C 6 H 5 CH 2 ), rather than methylphenyl radical isomers (C 6 H 4 CH 3 ), due to the relatively large difference in C-H bond dissociation energies for methyl (ca. 90 kcal mol À1 ) and ring (ca.…”

Section: Introductionmentioning

confidence: 99%

Hydroxyl radical formation in the gas phase oxidation of distonic 2-methylphenyl radical cations

Prendergast

Cooper

Kirk

et al. 2013

Phys. Chem. Chem. Phys.

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The reactions of distonic 4-(N,N,N-trimethylammonium)-2-methylphenyl and 5-(N,N,Ntrimethylammonium)-2-methylphenyl radical cations (m/z 149) with O 2 are studied in the gas phase using ion-trap mass spectrometry. Photodissociation (PD) of halogenated precursors gives rise to the target distonic charge-tagged methylphenyl radical whereas collision-induced dissociation (CID) is found to produce unreactive radical ions. The PD generated distonic radicals, however, react rapidly with O2 to form [M + O2]•+ and [M + O2 -OH]•+ ions, detected at m/z 181 and m/z 164, respectively. Quantum chemical calculations using G3SX(MP3) and M06-2X theories are deployed to examine key decomposition pathways of the 5-(N,N,N-trimethylammonium)-2-methylphenylperoxyl radical and rationalise the observed product ions. The prevailing product mechanism involves a 1,5-H shift in the peroxyl radical forming a QOOH-type intermediate that subsequently eliminates •OH to yield charge-tagged 2-quinone methide. Our study suggests that the analogous process should occur for the neutral methylphenyl + O2 reaction, thus serving as a plausible source of •OH radicals in combustion environments. The prevailing product mechanism involves a 1,5-H shift in the peroxyl radical forming a QOOH-type intermediate that subsequently eliminates OH to yield charge-tagged 2-quinone methide. Our study suggests that the analogous process should occur for the neutral methylphenyl + O 2 reaction, thus serving as a plausible source of OH radicals in combustion environments.

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“…They approximated the soot volume fraction growth by a first order expression with a temperature dependent rate constant. In addition, the amount of soot finally present varied with C/O ratio and also depended on temperature above 1500 K. Recently, Melton et al [8,9] investigated the effects of equivalence ratio (i.e. (fuel/oxidizer) ratio divided by the stoichiometric (fuel/oxidizer) ratio) on the formation of PAH and soot in premixed methane/oxygen/argon and ethane/oxygen/argon flames.…”

Section: Introductionmentioning

confidence: 99%

Experimental and artificial neural network modeling study on soot formation in premixed hydrocarbon flames☆

İnal

Tayfur

Melton

et al. 2003

Fuel

Self Cite

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The formation of soot in premixed flames of methane, ethane, propane, and butane was studied at three different equivalence ratios. Soot particle sizes, number densities, and volume fractions were determined using classical light scattering measurement techniques. The experimental data revealed that the soot properties were sensitive to the fuel type and combustion parameter equivalence ratio. Increase in equivalence ratio increased the amount of soot formed for each fuel. In addition, methane flames showed larger particle diameters at higher distances above the burner surface and propane, ethane, and butane flames came after the methane flames, respectively. Three-layer, feedforward type artificial neural networks having seven input neurons, one output neuron, and five hidden neurons for soot particle diameter predictions and seven hidden neurons for volume fraction predictions were used to model the soot properties. The network could not be trained and tested with sufficient accuracy to predict the number density due to a large data range and greater uncertainty in determination of this parameter. The number of complete data set used in the model was 156. There was a good agreement between the experimental and predicted values, and neural networks performed better when predicting output parameters (i.e. soot particle diameters and volume fractions) within the limits of the training data. q

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The effects of equivalence ratio on the formation of polycyclic aromatic hydrocarbons and soot in premixed ethane flames

Cited by 81 publications

References 20 publications

Effects of oxygenate concentration on species mole fractions in premixed -heptane flames

Effects of oxygenate concentration on species mole fractions in premixed -heptane flames

Hydroxyl radical formation in the gas phase oxidation of distonic 2-methylphenyl radical cations

Experimental and artificial neural network modeling study on soot formation in premixed hydrocarbon flames☆

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