Optical and chemical investigations on fuel-rich methane-oxygen premixed flames at atmospheric pressure

D’Alessio, Aldo; Lorenzo, A. Di; Beretta, F.; Venitozzi, C.

doi:10.1016/s0082-0784(73)80086-4

Cited by 37 publications

(14 citation statements)

References 14 publications

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“…A linear change in gain setting on the camera changes the actual gain constant exponentially; thus, the ratio in calibration constant is not linear. The value of the soot absorption function, E(m), used for comparison with the work of Shaddix [9,10], is assumed to be 0.26, based on an estimated value of the index of refraction m = 1.57 − 0.56i by D'Alessio et al [57]. However, as discussed above, the particular value of the constant is not important for the comparisons, but only for the absolute value obtained of the soot volume fraction.…”

Section: Calibrationmentioning

confidence: 99%

“…Dalzell et al suggested that within the wavelength range from 435.8 to 806.5 nm, the mean value of m is 1.57 − 0.46i for acetylene and 1.57 − 0.50i for propane diffusion flames [60]. In 1973, D'Alessio [57] suggested the value 1.57 − 0.56i as a mean value in visible range [61]. Whilst this value has been widely cited for its simplicity, a number of values of m have been reported by various of investigators as well, as shown in Table 2.…”

Section: Uncertainty From E(m)mentioning

confidence: 99%

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High spatial resolution laser cavity extinction and laser-induced incandescence in low-soot-producing flames

et al. 2015

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Accurate measurement techniques for in situ determination of soot are necessary to understand and monitor the process of soot particle production. One of these techniques is line-of-sight extinction, which is a fast, low-cost and quantitative method to investigate the soot volume fraction in flames. However, the extinction-based technique suffers from relatively high measurement uncertainty due to low signal-to-noise ratio, as the single-pass attenuation of the laser beam intensity is often insufficient. Multi-pass techniques can increase the sensitivity, but may suffer from low spatial resolution. To overcome this problem, we have developed a high spatial resolution laser cavity extinction technique to measure the soot volume fraction from low-soot-producing flames. A laser beam cavity is realised by placing two partially reflective concave mirrors on either side of the laminar diffusion flame under investigation. This configuration makes the beam convergent inside the cavity, allowing a spatial resolution within 200 μm, whilst increasing the absorption by an order of magnitude. Three different hydrocarbon fuels are tested: methane, propane and ethylene. The measurements of soot distribution across the flame show good agreement with results using laser-induced incandescence (LII) in the range from around 20 ppb to 15 ppm.

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Section: Calibrationmentioning

confidence: 99%

Section: Uncertainty From E(m)mentioning

confidence: 99%

High spatial resolution laser cavity extinction and laser-induced incandescence in low-soot-producing flames

et al. 2015

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“…This paper is meant only to give a short survey on some recent results of the investigation of charged particles in flames. For a more extended treatise see [5].…”

Section: Introductionmentioning

confidence: 99%

Investigation of the Formation of High Molecular Hydrocarbons and Soot in Premixed Hydrocarbon‐Oxygen Flames

Bockhorn

Fetting

Wenz

1983

Ber Bunsenges Phys Chem

269

120

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Apparate und Methoden / Flammen / ReaktionskinetikMeasurements of concentrations of high molecular hydrocarbons in laminar flat low pressure flames with various hydrocarbons under sooting conditions are reported. The results show that for all fuels investigated in that region of the flames where the bulk of soot is formed besides the main combustion products some characteristic groups of species are to be found. Within these groups of species only few fuel specific charactersitics are stated. The main fuel specific influence lies in the relative concentration for the species. A reaction scheme for the qualitative explanation of the results found is discussed.

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“…A variety of experimental results have been obtained in recent years using the optical methods outlined above [55][56][57][58] so that only a few specific topics will be examined here. Fig.…”

Section: Resultsmentioning

confidence: 99%

“…21 shows that an asymmetry arises in both Qyy (tJ) and QHH (tJ) components and becomes more and more pronounced as the residence time increases [56]. Other evidences of non-Rayleigh behavior come from the wavelength variation of the ratio QHH/Qyy at tJ == 7ff' and tJ == 8ff' and the departure from the A -4 law ofQVV in the range 270-510 run [55]. The first approximation taken for these features is monodisperse Mie scattering which is able to predict those effects in a qualitatively consistent way.…”

Section: Lls Measurements In Premixed Flames -mentioning

confidence: 96%

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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Optical and chemical investigations on fuel-rich methane-oxygen premixed flames at atmospheric pressure

Cited by 37 publications

References 14 publications

High spatial resolution laser cavity extinction and laser-induced incandescence in low-soot-producing flames

High spatial resolution laser cavity extinction and laser-induced incandescence in low-soot-producing flames

Investigation of the Formation of High Molecular Hydrocarbons and Soot in Premixed Hydrocarbon‐Oxygen Flames

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

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