UV absorption, laser excited fluorescence and direct sampling in the study of the formation of polycyclic aromatic hydrocarbons in rich CH4/O2 flames

Lorenzo, A. Di; D’Alessio, Antonio; Cincotti, V.; Masi, S.; Menna, P.; Venitozzi, C.

doi:10.1016/s0082-0784(81)80054-9

Cited by 23 publications

(20 citation statements)

References 2 publications

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“…cp tot in premixed flames ranged between 10-2 and 10-3 , apart from higher values in the early combustion zone ( z ~ 2 mm) [54]. The percentage extinction in the diffusion flame was below 1 %, at the limit of detectability ofthe present set-up, so that the lower estimate of the quantum efficiency was around 0.1.…”

mentioning

confidence: 54%

“…The scattered light was analyzed with a 0.25 Jarrell-Ash monochromator, which had its 100 p,m entrance slit parrallel to the scattering plane. Procedures for calibrating the spectral response of the detection system in the different polarization planes and for determining stray light effects were reported elsewhere [54].…”

Section: Experimental Aspectsmentioning

confidence: 99%

“…More recent and systematic work has been done by Menna in his thesis [80] and it is partly reported in ref. [54]. Fig.…”

mentioning

confidence: 99%

“…More recent and detailed analysis of this effect has been reported by MUller-Dethlefs [60] in premixed and counter-flow diffusion ethylene-air flames , by Haynes et al in premixed and laminar flames stabilized on a double WolfhardParker burner [59,69] and by Mallard and Schenck [70] and Di Lorenzo et af. [54] in premixed flames.…”

mentioning

confidence: 99%

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Laser Light Scattering and Fluorescence Diagnostics of Rich Flames Produced by Gaseous and Liquid Fuels

D’Alessio

1981

Particulate Carbon

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Rich combustion systems present a much more complex chemistry than stoichiometric or lean ones: compounds from unsaturated C2 hydrocarbons to polynuclear aromatic hydrocarbons (P AH) are formed and destroyed, soot particles nucleate, grow and agglomerate and eventually burn out at different stages of the combustion. Furthermore, the fuel is introduced in the form of liquid droplets in many practical systems.The present paper presents initially a short summary of the scattering and extinction properties of spherical particles, from the Rayleigh regime to the ray optics limit (geometric regime), referring particularly to the simultaneous presence of soot particles and fuel droplets.Problems connected with polydispersion of spheres and the presence of particles of different shapes (spheroids, clusters, chains, etc.) are also briefly discussed.The paper reviews subsequently the u. v ./visible absorption and fluorescence spectra of some P AH compounds and discusses their interferences with the extinction due to soot particles and/or droplets and the spontaneous Raman effects due to low molecular mass compounds. The experimental section presents initially some laser light scattering (LLS) and extinction measurements carried out on large diesel oil spray flames. A procedure for distinguishing between fuel droplets and soot particles is illustrated, and average size and number concentration of soot particlesare evaluated. The effects of swirl on the spatial distribution of soot particles and fuel droplets for these types of flames are also shown. Optical results obtained on premixed and diffusion CH402 flames are compared in the next section: LLS measurements provide evidence for zones of early formation of soot particles while u. v. absorption and fluorescence spectra are related to the build-up ofPAH compounds.The final part of the paper compares the experimental results with the theoretical models and discusses agreement and limits; suggestions are LIST OF SYMBOLS

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mentioning

confidence: 54%

Section: Experimental Aspectsmentioning

confidence: 99%

“…More recent and systematic work has been done by Menna in his thesis [80] and it is partly reported in ref. [54]. Fig.…”

mentioning

confidence: 99%

mentioning

confidence: 99%

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Laser Light Scattering and Fluorescence Diagnostics of Rich Flames Produced by Gaseous and Liquid Fuels

D’Alessio

1981

Particulate Carbon

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“…In the post flame zone radical mole fractions are much lower and PAH might be formed by molecular mechanisms or heterogeneous mechanisms on the surface of soot particles. Such PAH formation mechanisms would be very sensitive to the hydrocarbon composition in the post flame zone, which in turn is very sensitive to changes in cpo The recent results of DiLorenzo et al [71] provide some support for this picture.…”

Section: Formation Of Pah and Soot In Acetylene Flamesmentioning

confidence: 92%

Pre-Particle Chemistry in Soot Formation

Bittner

Howard

1981

Particulate Carbon

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Species and reactions involved in the early stages of soot formation prior to the formation of particles have been studied in flat low pressure flames of benzene using a molecular beam mass spectrometer system. In a near-sooting (equivalence ratio c/J = 1.8) benzene-oxygen-argon flame, the profiles of molar flux versus distance from the burner for several reactant, intermediate, and product species were calculated from the mole fraction profiles. The flux profiles indicate that CO, C6H60 and CSH6 are early intermediates in the ring destruction process but that C2H2 is not. The flux profiles of C6H6 and C2Hz are consistent with benzene consumption by OH addition and the OH + C6H6 reaction having a much larger rate coefficient than OH + C2H2. A mechanism is outlined for production of Ct, C2, C3, C4 and Cs species from benzene that is consistent with the flux profiles of intermediate species. The production of more hydrogenated species from those of low H/C ratio as they diffuse toward the burner surface is discussed.Relative measurements of high molecular weight material (> 200 amu) as the fuel equivalence ratio is increased past the sooting limit (c/J = 1.9) in benzene flames suggest a sequential growth process from polycyclic aromatic hydrocarbons (PAH) in the mass range 120-210 amu to higher molecular weight hydrocarbons and then to soot. A preliminary analysis of reaction mechanisms suggests that the role of the aromatic hydrocarbon is to provide a structure capable of stabilizing by internal aromatic substitution reactions radicals formed from addition of non-aromatic species. The presence of P AH in the oxidation zone of sooting C2H2 flames was also observed and suggests that aromatics may playa similar role in flames of non-aromatic fuels.

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Determination of the U.V.-Visible Optical Properties of Submicronic Carbonaceous Particles at High Temperature from Scattering and Extinction Measurements

Vaglieco

Beretta

D’Alessio

1988

Experiments on Cosmic Dust Analogues

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UV absorption, laser excited fluorescence and direct sampling in the study of the formation of polycyclic aromatic hydrocarbons in rich CH4/O2 flames

Cited by 23 publications

References 2 publications

Laser Light Scattering and Fluorescence Diagnostics of Rich Flames Produced by Gaseous and Liquid Fuels

Laser Light Scattering and Fluorescence Diagnostics of Rich Flames Produced by Gaseous and Liquid Fuels

Pre-Particle Chemistry in Soot Formation

Determination of the U.V.-Visible Optical Properties of Submicronic Carbonaceous Particles at High Temperature from Scattering and Extinction Measurements

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