| 1. |
- Simonsson, Johan, et al.
(författare)
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Soot Concentrations in an Atmospheric Entrained Flow Gasifier with Variations in Fuel and Burner Configuration Studied Using Diode-Laser Extinction Measurements
- 2016
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Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 0887-0624 .- 1520-5029. ; 30:3, s. 2174-2186
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Tidskriftsartikel (refereegranskat)abstract
- Soot concentration measurements were performed using diode-laser extinction in an atmospheric air-blown entrained flow gasifier at two vertical levels. The gasifier was operated at different air-fuel equivalence ratios and with variations in fuel and burner configurations. Two fuels were investigated: wood powder and peat powder. These were burned using two burner configurations, one giving a rotating flow inside the gasifier (swirl), and one where the fuel and air were injected parallel with the gasifier axis (jet). The diode-laser measurements were performed at the wavelength 808 nm from which the soot concentrations were estimated, and additionally at 450 nm in order to gain insight into the spectral dependence of the extinction to estimate measurement quality. Additional diagnostic techniques were used, such as an electrical low-pressure impactor (ELPI) for soot size distributions and gas chromatography for species concentration measurements. The results show that wood powder produces higher soot concentrations than peat powder, especially at lower air-fuel equivalence ratios. Furthermore, the burner configuration had in general much less impact than the choice of fuel on the soot concentration.
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| 2. |
- Bladh, Henrik, et al.
(författare)
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Probing the smallest soot particles in low-sooting premixed flames using laser-induced incandescence
- 2015
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Ingår i: Proceedings of the Combustion Institute. - : Elsevier BV. - 1540-7489. ; 35, s. 1843-1850
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Tidskriftsartikel (refereegranskat)abstract
- In this work we investigate nascent soot particles by analyzing laser-induced incandescence (LII) signals obtained in low-sooting premixed flames. The analysis covers two data sets obtained in separate experimental campaigns. The first data set was obtained in a previous work (Mouton et al., 2013) in methane/oxygen/nitrogen flames (equivalence ratio range 1.95 < Phi < 2.32) at 26.7 kPa, whereas the second was performed in atmospheric ethylene/air flames (1.77 < Phi < 2.00). Both studies show similar trends, i.e. a gradual change of the fluence curves (evolution of the LII signal as function of the laser fluence) from the well-known S-shaped curve for mature soot found at high heights above the burner (HAB) and high equivalence ratio, to a nearly linear behavior for nascent soot found at low HAB and reduced equivalence ratio. With this change comes a decrease in the LII decay time (and hence inferred particle size). Also, this decay time appears to be almost constant with HAB in flames having the lowest equivalence ratio at which the incandescence signal could be detected. In these flames, so-called nucleation flames, the stability of the particle size with HAB suggests that recently nucleated particles have undergone marginal surface growth and coagulation. Existence of such nucleation flames is of great interest for improving the theoretical description of the nucleation step. Experimental results are analyzed by using a theoretical model for LII to determine the particle size evolution throughout the flame at various experimental conditions. We highlight the size difference from nascent soot particles up to mature soot, giving insight into the particle nucleation and the surface growth processes as a function of reaction time and flame conditions. (C) 2014 The Combustion Institute. Published by Elsevier Inc. All rights reserved.
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| 3. |
- Gallo, Yann, et al.
(författare)
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A Study of In-Cylinder Soot Oxidation by Laser Extinction Measurements During an EGR-Sweep in an Optical Diesel Engine
- 2015
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Ingår i: SAE Technical Papers. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191.
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Tidskriftsartikel (refereegranskat)abstract
- Two competing in-cylinder processes, soot formation and soot oxidation, govern soot emissions from diesel engines. Previous studies have shown a lack of correlation between the soot formation rate and soot emissions. The current experiment focuses on the correlation between soot oxidation rates and soot emissions. Laser extinction is measured using a red (690nm) laser beam, which is sent vertically through the cylinder. This wavelength is long enough to minimize absorption interference from poly-aromatic hydrocarbons, while still in the visible regime. It is modulated at 72 kHz in order to produce 10 pulses per crank angle degree at an engine speed of 1200 rpm. The intake oxygen concentration is varied between 9% and 21%. The time resolved extinction measurements are used to estimate soot oxidation rates during expansion. High-speed video imaging is used in conjunction with the laser-extinction technique to indicate the location of the sooting regions, and to assess beam steering effects. The oxidation processes are described using single exponential decay fits and an attempt to correlate them with the late cycle rate of heat release was made.
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| 4. |
- Nordström, Emil, et al.
(författare)
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Local gas heating in sooting flames by heat transfer from laser-heated particles investigated using rotational CARS and LII
- 2015
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Ingår i: Proceedings of the Combustion Institute. - : Elsevier BV. - 1540-7489. ; 35, s. 3707-3713
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Tidskriftsartikel (refereegranskat)abstract
- Soot particles strongly absorb radiation in the visible and infrared spectral regions, and the soot interaction with laser light during laser diagnostic interrogation leads to particle heating and often to subsequent sublimation. Consequently, laser-heated particles transfer heat to the ambient gas leading to local gas heating, a process that has received minor attention so far in the diagnostic community. In the present work, this specific local gas heating is measured in a pump-probe-type experiment. A 1064-nm laser beam heated the soot particles in an ethylene/ air diffusion flame (on a Gulder-burner) with known soot volume fraction, and a two-beam rotational coherent anti-Stokes Raman spectroscopy (CARS) setup was used to probe the local gas temperature on time scales from nanoseconds to milliseconds. The temperature of the heated particles was simultaneously probed using a two-color laser-induced incandescence (2C-LII) detection system. The results show that laser heating of soot particles from flame temperatures to sublimation temperatures leads to local gas heating of similar to 100 K at a soot volume fraction of 4 ppm, in good agreement with theoretical predictions. The implication of these results to the application of laser diagnostic techniques is briefly discussed. (C) 2014 The Combustion Institute. Published by Elsevier Inc. All rights reserved.
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| 5. |
- Olofsson, Nils-Erik, et al.
(författare)
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Evolution of properties for aging soot in premixed flat flames studied by laser-induced incandescence and elastic light scattering
- 2015
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Ingår i: Applied Physics B. - : Springer Science and Business Media LLC. - 0946-2171 .- 1432-0649. ; 119:4, s. 669-683
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Tidskriftsartikel (refereegranskat)abstract
- A detailed study has been made of soot growth in two premixed flat ethylene/air flames, at I broken vertical bar = 2.1 and I broken vertical bar = 2.3, where focus has been on following the change in optical properties from nascent to more mature soot, and the importance of these properties for laser-induced incandescence (LII). A combination of two-color LII (2C-LII) and elastic light scattering was utilized for studies of soot absorption and sublimation for a range of laser fluences in a pump-probe experiment, and the experimental results were compared with LII model predictions. Both flames show similar trends, indicating that the soot becomes less transparent during the growth process until some level of maturity is reached at higher flame heights, where the measured properties reach almost constant values. A sublimation fluence threshold of similar to 0.14 J/cm(2) (at 1064 nm for a flame temperature around 1700 K) was evaluated for mature soot, corresponding to a sublimation temperature of similar to 3400 K. Soot peak temperatures from 2C-LII were evaluated both using a constant E(m) and a wavelength dependence for E(m) extracted from extinction measurements, leading to a discussion on how the sublimation temperature relates to the maturity of soot.
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| 6. |
- Pettersson, Christer, et al.
(författare)
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Handbok för provledare vid jägarexamen : Handbok 2018:1 Utgåva 1 April 2018
- 2018
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Den 15 december 1983 beslutade regeringen att jägarexamen skulle införasi hela landet den 1 januari 1985. Samtidigt bemyndigade regeringen Naturvårdsverketatt bland annat utfärda föreskrifter för jägarexamen.Naturvårdsverketsföreskrifter är bindande. Nu gällande föreskrifter;Naturvårdsverketsföreskrifter (NFS 2015:10) om jägarexamen trädde i kraftden 1 januari 2016 efter vissa ändringar i tidigare föreskrifter.Handboken vänder sig framför allt till provledare för jägarexamen ochär avsedd att medverka till att jägarexamen genomförs på ett enhetligt sätt ihela landet. Tillsammans med jägarorganisationernas PM, som också finnsi denna publikation, ger den till exempel anvisningar om provplatsernasutformning och om hur proven ska genomföras och bedömas. Naturvårdsverketsvarar för handbokens innehåll, liksom jägarorganisationerna svararför sin PM.Arbetet med publikationen har bedrivits av Christer Pettersson, DanielBladh och Elisabet Perming för Naturvårdsverketoch jägarexamenssamordnareHenrik Falk för Svenska Jägareförbundet och jägarexamenssamordnareSivertBorup för Jägarnas Riksförbund.Stockholm 2018NaturvårdsverketClaes SvedlindhAvdelningschef Naturavdelningen
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| 7. |
- Robert, Etienne, et al.
(författare)
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Soot Formation in Unstrained Diffusion Flames
- 2015
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Ingår i: Combustion Science and Technology. - : Informa UK Limited. - 1563-521X .- 0010-2202. ; 187:4, s. 577-593
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Tidskriftsartikel (refereegranskat)abstract
- The formation of soot particles has been investigated in CH4/O-2 diffusion flames using a unique burner design, which allows the creation of a nearly unstrained planar reaction sheet. Spatially resolved soot volume fractions were obtained using laser-induced incandescence. These soot measurements and the sooting limits were obtained as a function of bulk flow across the flame and mixture strength. Samples were collected using thermophoretic sampling and analyzed using electron microscopy, revealing a broad range of microstructures including particles with unusually large primary diameters and carbon nanotubes. A theoretical model is presented, which confirms that under certain conditions the 1D nature of the flow field of the burner and the strong adverse temperature gradient on the fuel side of the flame result in the soot particles being held in place by thermophoretic forces and allowed to grow for very long time periods. Some of these so-called super aggregates reached sizes of tens of microns and became visible to the naked eye in the soot layer.
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| 8. |
- Simonsson, Johan, et al.
(författare)
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Influence of potassium and iron chloride on the early stages of soot formation studied using imaging LII/ELS and TEM techniques
- 2017
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Ingår i: Proceedings of the Combustion Institute. - : Elsevier BV. - 1540-7489. ; 36:1, s. 853-860
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Tidskriftsartikel (refereegranskat)abstract
- Laser-induced incandescence (LII), elastic light scattering (ELS) and extinction were used to investigate the early stages of soot formation when seeding metal salts at various concentrations into a premixed ethylene/air flame on a PerkinElmer burner. The investigation contained seven salts, where we in this work mainly focus on two of these salts, potassium chloride (KCl) and iron chloride (FeCl3), as these for mature soot resulted in the largest reduction and highest increase in soot concentration, respectively. The optical measurements show that the potassium chloride significantly reduces the build-up of larger soot precursors and also decreases the sizes of the primary soot particles both at the nucleation stage as well as for more mature soot later in the formation process. This is also confirmed by analysis of transmission electron microscopy (TEM) images, which clearly show smaller primary soot particles for the potassium chloride-seeded flame. The iron chloride-seeded flames were found to have marginal influence on the primary particle sizes based on the optical data, although somewhat more irregular shapes could be observed in TEM images.
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| 9. |
- Simonsson, Johan, et al.
(författare)
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Wavelength dependence of extinction in sooting flat premixed flames in the visible and near-infrared regimes
- 2015
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Ingår i: Applied Physics B. - : Springer Science and Business Media LLC. - 0946-2171 .- 1432-0649. ; 119:4, s. 657-667
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Tidskriftsartikel (refereegranskat)abstract
- A diode-laser-based setup was used for extinction measurements at various heights in two flat premixed sooting ethylene/air flames in order to investigate the wavelength dependence of the extinction. Twelve laser wavelengths were used in the interval 405-1064 nm, and with this setup, a sensitivity of similar to 10(-4) was achieved for the extinction. Soot volume fractions inferred from the extinction measurements were always higher in the visible spectral region than in the infrared, an effect associated with additional absorption by large hydrocarbons, such as polycyclic aromatic hydrocarbons. For wavelengths greater than around 700 nm and at high heights above burner (HAB), the extinction shows an inverse dependence with wavelength, in concurrence with wavelength-independent optical properties of soot. In the same spectral region at lower HAB, the wavelength dependence is observed to be stronger, indicating that the soot optical properties show variation with wavelength. Furthermore, a continuous change in the wavelength dependence of the absorption function E(m) is shown from nascent soot at lower heights to more mature soot at higher heights. The presented results are of importance for soot diagnostics relying on the efficiency of light absorption by soot such as laser-induced incandescence (LII).
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