Analysis of soot surface growth pathways using published plug-flow reactor data with new particle size distribution measurements and published premixed flame data

Kronholm, David F.; Howard, Jack B.

doi:10.1016/s0082-0784(00)80672-4

Cited by 38 publications

(28 citation statements)

References 26 publications

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“…Kyriakides and Dent (1986) assume a density for soot particles of 2 g/cm 3 in their phenomenological model of Diesel combustion, as do Pontikakis et al (2001) or Saathoff et al (2002), although this latter reference assumes this value only for spark ignition soot, while a density of 1.7 g/cm 3 is assumed for Diesel engine soot. Other works propose values for soot density between 1.8 g/cm 3 (Kronholm and Howard 2000;Corcione et al 2002) and 1.5 g/cm 3 (Yu and Xu 1986).…”

Section: Resultsmentioning

confidence: 99%

Diesel Particle Size Distribution Estimation from Digital Image Analysis

Lapuerta

Armas

Gómez

2003

Aerosol Science and Technology

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One of the most serious problems associated with Diesel engines is pollutant emissions, specially nitrogen oxides and particulate matter. However, although current emissions standards in Europe and America with regard to light vehicles and heavy duty engines refer to the particulate limit in mass units, there has been increasing concern of late to know the size and number of particles emitted by engines. This interest has been promoted by the latest studies about the harmful effects of particles on health and is enhanced by recent changes in internal combustion engine technology. This study is focused on the implementation of a method to determine the particle size distribution that could be appropriate for the current methodology of vehicle certification in Europe. This method uses an automated Digital Image Analysis Algorithm (DIAA) to determine particle size trends from Scanning Electron Microscope (SEM) images of filters charged in a partial dilution system used for measuring specific particulate emissions. The experimental work was performed on a stationary electric generation direct injection Diesel engine with 0.5 MW (671 hp) rated power, which is considered as a typical engine in middle power industries. Particulate size distributions obtained using DIAA were compared with distributions obtained using an Optical Particle Counter (OC) and a Scanning Mobility Particle Sizer (SMPS), the latter currently considered as the most reliable technique. Although the number concentration detected by this method does not represent the real flowing particle concentration, the algorithm gives a fair reproduction of the trends observed with on-line techniques (SMPS and OC) when the engine load is varied.

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Section: Resultsmentioning

confidence: 99%

Diesel Particle Size Distribution Estimation from Digital Image Analysis

Lapuerta

Armas

Gómez

2003

Aerosol Science and Technology

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“…Calculating the amount of carbon that is needed to cover primary particles of d XRD ‫ס‬ 39 nm [ Figs. 3(a), 3(c), and 4(a)-4(c)] with a 2.3-nm-thick C layer (using C ‫ס‬ 1.8 17 ) or 1.9-nmthick C layer (using C ‫ס‬ 2.27 18 ) results in powders containing 15 wt.% carbon. This is in good agreement with thickness of the C layer observed from TEM for the 15 wt.% C and consistent with the EELS measurements, ) and lower left part of (d) are not coated and do not contain crystal reflections that are typical for crystalline TiO 2 suggesting that these are carbon particles coexisting with carbon-coated titania particles that can be observed in the other parts of this picture.…”

Section: Discussionmentioning

confidence: 99%

“…When the weighed particle diameter from nitrogen adsorption is calculated using anatase ‫ס‬ 3.84 g/cm 3 , rutile ‫ס‬ 4.26 g/cm 3 , and carbon ‫ס‬ 1.8 g/cm 3 for soot 17 (or 2.27 g/cm 3 for graphite 18 ) as well as the average XRD crystallite size 15 ( Fig. 2) as functions of the powder carbon content, two distinct regimes are observed (Fig.…”

Section: Hk Kammler Et Almentioning

confidence: 99%

Carbon-coated titania nanostructured particles: Continuous, one-step flame-synthesis

Kammler

Pratsinis

2003

J. Mater. Res.

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Concurrent synthesis of titania-carbon nanoparticles (up to 52 wt.% in C) was studied in a diffusion flame aerosol reactor by combustion of titanium tetraisopropoxide and acetylene. These graphitically layered carbon-coated titania particles were characterized by high-resolution transmission electron microscopy (HRTEM), with elemental mapping of C and Ti, x-ray diffraction (XRD), and nitrogen adsorption [Brunauer-Emmett-Teller (BET)]. The specific surface area of the powder was controlled by the acetylene flow rate from 29 to 62 m 2 /g as the rutile content decreased from 68 to 17 wt.%. Light blue titania suboxides formed at low acetylene flow rates. The average XRD crystal size of TiO 2 decreased steadily with increasing carbon content of the composite powders, while the average BET primary particle size calculated from nitrogen adsorption decreased first and then approached a constant value. The latter is attributed to the formation of individual carbon particles next to carbon-coated titania particles as observed by HRTEM and electron spectroscopic imaging.

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“…These reactions can involve either the step-wise addition of low-molecular weight species, such as acetylene, to radical sites on larger aromatic compounds [92], or the coagulation of two larger specific PAH molecules and/or carbon clusters [93]. Similar to the HACA mechanism proposed for PAH formation [94], the step-wise addition mechanism for fullerenes would proceed through abstraction of an H-atom from an aromatic molecule. This would be followed by C 2 H 2 addition and cyclization leading to ring closure.…”

Section: Fullerene Formation Mechanismsmentioning

confidence: 99%

Combustion synthesis of fullerenes and fullerenic nanostructures

Goel

Hebgen

Sande

et al. 2002

Carbon

117

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Fullerenes are molecules comprised entirely of sp 2 -bonded carbon atoms arranged in pentagonal and hexagonal rings to form a hollow, closed-cage structure. Buckyballs, a subset which contains C 60 and C 70 , are single-shell molecules while fullerenic nanostructures can contain many shells and over 300 carbon atoms. Both fullerenes and nanostructures have an array of applications in a wide variety of fields, including medical and consumer products. Fullerenes were discovered in 1985 and were first isolated from the products of a laminar low-pressure premixed benzene/oxygen/argon flame operating at fuel-rich conditions in 1991. Flame studies indicated that fullerene yields depend on operating parameters such as temperature, pressure, residence time, and equivalence ratio. High-resolution transmission electron microscopy (HRTEM) showed that the soot contains nanostructures, including onions and nanotubes.Although flame conditions for forming fullerenes have been identified, the process has not been optimized and many flame environments of potential interest are unstudied. Mechanistic characteristics of fullerene formation remain poorly understood and cost estimation of large-scale production has not been performed. Accordingly, this work focused on: 1) studying fullerene formation in diffusion and premixed flames under new conditions to identify optimal parameters; 2) investigating the reaction of fullerenes with soot; 3) positively identifying C 60 molecules in HRTEM by tethering them to carbon black; and 4) providing a cost estimation for industrial fullerenic soot production.Samples of condensable material from laminar low-pressure benzene/argon/oxygen diffusion flames were collected and analyzed by high-performance liquid chromatography (HPLC) and HRTEM. The highest concentration of fullerenes in a flame was always detected just above the height where the fuel is consumed. The percentage of fullerenes in condensable material increases with decreasing pressure and the fullerene content of flames with similar cold gas velocities shows a strong dependence on length. A shorter flame, resulting from higher dilution or lower pressure, favors the formation of fullerenes rather than soot, exhibited by the lower amount of soot and precursors in such flames. This indicates a stronger correlation of fullerene consumption to soot levels than of fullerene formation to precursor concentration. The maximum flame temperature seems to be of minor importance in formation. The overall highest amount of fullerenes was found for a surprisingly high dilution of fuel with argon. The HRTEM analysis showed an increase of the curvature of the carbon layers, and hence increased fullerenic character, with increasing distance from the burner up to the point of maximum fullerene concentration, after which it decreases, consistent with the HPLC analysis. The soot shows highly ordered regions that appear to have been cells of fullerenic nanostructure formation. The samples also included fullerenic nanostructures such as tubes and sp...

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Analysis of soot surface growth pathways using published plug-flow reactor data with new particle size distribution measurements and published premixed flame data

Cited by 38 publications

References 26 publications

Diesel Particle Size Distribution Estimation from Digital Image Analysis

Diesel Particle Size Distribution Estimation from Digital Image Analysis

Carbon-coated titania nanostructured particles: Continuous, one-step flame-synthesis

Combustion synthesis of fullerenes and fullerenic nanostructures

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