| 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, Daniel, 1980-
(författare)
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Didaktiska val i partidemokratin : Om partiskolning och lärande i politiken
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Syftet med avhandlingen är att undersöka de överväganden och skäl som ligger bakom didaktiska val som fattas när utbildning organiseras för partipolitiskt aktiva personer. De anordnare som främst står i fokus för avhandlingen är de nationella partiorganisationerna medan den kommunala förvaltningen fungerar som en kon-trastpunkt. Avhandlingens teoretiska perspektiv utgörs av vuxendidaktik samt av ett analytiskt schema där politiska partier förstås som strategiska aktörer. Det didaktiska kunskapsintresset riktar sig främst mot det politiska systemet, partierna som aktörer samt de egna partimedlemmarna. Det är kvalitativ forskning som ligger till grund för de specifika studier som avhandlingen omfattar. Det empiriska materialet har genererats genom kvalitativa forskningsintervjuer, insamling av olika typer av dokument samt omfattande kartläggning.Avhandlingen utgör en sammanläggningsavhandling som omfattar fyra artiklar. Artikel I analyserar organisering av partiskolning som verktyg för nationella partiorganisationer. Artikel II lyfter fram fostransprocesser som de nationella partiorganisationerna söker främja genom organisering av partiskolning riktat till partimedlemmar och lokalföreningar. Artikel III lyfter blicken gentemot det politiska systemet och visar hur partiskolning både kan påverka och påverkas av hur olika partifunktioner utövas. Artikel IV tar sikte på den utbildningsverksamhet som genomförs i svenska kommuner och lyfter fram tre tankelinjer som uttryck för hur de kommunala anordnarna resonerar kring och motiverar den utbildning som de erbjuder till lokala folkvalda. Sammantaget bidrar avhandlingen med kunskap om vad som sker i mötet mellan utbildning och partidemokratin. Påverkan och fostran lyfts fram som två centrala skäl bakom de didaktiska val som fattas av de nationella partiorganisationerna vid organisering av partiskolning. Hur de nationella partiorganisationerna motiverar och resonerar kring den utbildningsverksamhet som de organiserar diskuteras i samband med samlingsbegreppen personer, process och platsen. Avhandlingen visar också hur partiskolning innehar en strategisk potential för partierna. Organisering av utbildningsverksamhet i politiska partier och kommuner kan även påverka konstruktionen av deltagarnas demokratiska kompetens, vilket kan spela roll för hur partimedlemmarnas aktiva medborgarskap kommer till uttryck.
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| 3. |
- Bladh, Daniel, 1980-, et al.
(författare)
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Lines of Reasoning When Designing Education for Municipal Councillors in Sweden
- 2023
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Ingår i: Scandinavian Journal of Educational Research. - : Taylor & Francis. - 0031-3831 .- 1470-1170. ; 67:1, s. 113-125
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Tidskriftsartikel (refereegranskat)abstract
- Although elected representatives play an imperative role for the functioning of a formal democracy, educational research has so far not given much attention to the education and training offered to this group of people. A democratic dilemma may arise in the design and organisation of this education that relate to local governance and policy processes. This paper investigates introductory education that Swedish municipalities offer to municipal councillors and explore the reasons behind its design. The study draws on a comprehensive set of empirical material, consisting of educational programmes from 261 Swedish municipalities and interviews with municipal representatives. The results suggest three different lines of reasoning, denoted system-oriented, relationship-oriented, and market-oriented lines, behind the design of this education. The importance of these results can be considered in relation to previous findings that a strained relation exist between elected representatives and local administrations in Sweden.
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| 4. |
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| 5. |
- Bladh, Henrik, et al.
(författare)
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Characteristics of laser-induced incandescence from soot in studies of a time-dependent heat- and mass-transfer model
- 2004
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Ingår i: Applied Physics B. - : Springer Science and Business Media LLC. - 0946-2171. ; 78:2, s. 241-248
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Tidskriftsartikel (refereegranskat)abstract
- The temporal behavior of the laser-induced incandescence (LII) signal is often used for soot-particle sizing, which is possible because the cooling behavior of a laser-heated particle is dependent on the particle size. The heat- and mass-transfer model describing the temporal LII-signal behavior has in this work been extended to include the influence of the primary particle-size distribution and the spatial distribution of laser energy. When evaluating primary particle size, a monodisperse size distribution is often assumed, although it is well known that a polydisperse distribution is a better description of the real situation. In this work the impact of this assumption is investigated for Gaussian and lognormal size distributions of different widths, and the result is a significant bias towards larger particle sizes because of the higher influence of larger particles on the LII signal. Moreover, the dependence of the LII signal on the laser fluence is studied for different spatial distributions of the laser energy. The top-hat, Gaussian sheet and Gaussian beam distributions were tested and it is established that the LII signal is strongly dependent on the choice of distribution. However, in this case the influence of particle size is minor.
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| 6. |
- Bladh, Henrik, et al.
(författare)
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Experimental and theoretical comparison of spatially resolved laser-induced incandescence (LII) signals of soot in backward and right-angle configuration
- 2006
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Ingår i: Applied Physics B. - : Springer Science and Business Media LLC. - 0946-2171 .- 1432-0649. ; 83:3, s. 423-433
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Tidskriftsartikel (refereegranskat)abstract
- In-situ measurements of soot volume fraction in the exhausts of jet engines can be carried out using the laser-induced incandescence (LII) technique in backward configuration, in which the signal is detected in the opposite direction of the laser beam propagation. In order to improve backward LII for quantitative measurements, we have in this work made a detailed experimental and theoretical investigation in which backward LII has been compared with the more commonly used right-angle LII technique. Both configurations were used in simultaneous visualization experiments at various pulse energies and gate timings in a stabilized methane diffusion flame. The spatial near-Gaussian laser energy distribution was monitored on-line as well as the time-resolved LII signal. A heat and mass transfer model for soot particles exposed to laser radiation was used to theoretically predict both the temporal and spatial LII signals. Comparison between experimental and theoretical LII signals indicates similar general behaviour, for example the broadening of the spatial LII distribution and the hole-burning effect at centre of the beam due to sublimation for increasing laser pulse energies. However, our comparison also indicates that the current heat and mass transfer model overpredicts signal intensities at higher fluence, and possible reasons for this behaviour are discussed.
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| 7. |
- Bladh, Henrik, et al.
(författare)
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Experimental and theoretical comparison of spatially resolved laser-induced incandescence signals in a sooting flame
- 2005
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Ingår i: Proceedings of the European Combustion Meeting.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- A detailed experimental and theoretical investigation has been made on the use of Laser-Induced Incandescence (LII) in two configurations; right-angle LII and backward LII. Both right-angle and backward LII imaging measurements were conducted in simultaneous experiments at various pulse energies. The theoretically calculated LII signals were based on a heat transfer model for soot particles exposed to laser radiation, and were compared with the experimental LII images. Both the experimental and theoretical results from this initial comparison showed similar general behaviour, for example the broadening of the spatial LII distribution and the hole-burning effect at centre for increasing laser pulse energies.
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| 8. |
- Bladh, Henrik, et al.
(författare)
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Flame propagation visualization in a spark-ignition engine using laser-induced fluorescence of cool-flame species
- 2005
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Ingår i: Measurement Science & Technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 16:5, s. 1083-1091
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Tidskriftsartikel (refereegranskat)abstract
- The flame propagation in a spark-ignition engine has been studied using laser-induced fluorescence (LIF) of species formed during the first ignition stage of hydrocarbon combustion. The detected two-dimensional LIF images showed the distribution of unburned regions. For the excitation, two Nd:YAG lasers operating at 355 mn were used for two consecutive measurements within the same engine cycle with adjustable time separation between the pulses. Two ICCD cameras that were synchronized to each of the laser pulses recorded pairs of fluorescence images, i.e. the movement of the flame front could be tracked. It is well known that formaldehyde is excited using a wavelength of 355 nm and a spectral signature of this species was also identified in engine LIF spectra. Programme routines were developed and used for evaluation of the flame propagation velocity from the fluorescence images. This paper presents the potential and the characteristics of the experimental technique as well as the evaluation procedure. The measurements of cool-flame intermediates have also been compared with measurements of fuel-tracer as an indicator of unburned fuel-air mixture. A good agreement between position and shape of the signal areas was obtained at crank angles where both fluorescence signal from cool-flame species excited at 355 nm and added 3-pentanone excited at 266 nm could be detected.
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| 9. |
- Bladh, Henrik, et al.
(författare)
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Influence of Soot Particle Aggregation on Time-Resolved Laser-Induced Incandescence Signals
- 2011
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Ingår i: Applied Physics B. - : Springer Science and Business Media LLC. - 0946-2171 .- 1432-0649. ; 104:2, s. 331-341
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Tidskriftsartikel (refereegranskat)abstract
- Laser-induced incandescence (LII) is a versatile technique for quantitative soot measurements in flames and exhausts. When used for particle sizing, the time-resolved signals are analysed as these will show a decay rate dependent on the soot particle size. Such an analysis has traditionally been based on the assumption of isolated primary particles. However, soot particles in flames and exhausts are usually aggregated, which implies loss of surface area, less heat conduction and hence errors in estimated particle sizes. In this work we present an experimental investigation aiming to quantify this effect. A soot generator, based on a propane diffusion flame, was used to produce a stable soot stream and the soot was characterised by transmission electron microscopy (TEM), a scanning mobility particle sizer (SMPS) and an aerosol particle mass analyzer coupled in series after a differential mobility analyzer (DMA-APM). Despite nearly identical primary particle size distributions for three selected operating conditions, LII measurements resulted in signal decays with significant differences in decay rate. However, the three cases were found to have quite different levels of aggregation as shown both in TEM images and mobility size distributions, and the results agree qualitatively with the expected effect of diminished heat conduction from aggregated particles resulting in longer LII signal decays. In an attempt to explain the differences quantitatively, the LII signal dependence on aggregation was modelled using a heat and mass transfer model for LII given the primary particle and aggregate size distribution data as input. Quantitative agreement was not reached and reasons for this discrepancy are discussed.
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| 10. |
- Bladh, Henrik, et al.
(författare)
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Influence of spatial laser energy distribution on evaluated soot particle sizes using two-colour laser-induced incandescence in a flat premixed ethylene/air flame
- 2009
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Ingår i: Applied Physics B. - : Springer Science and Business Media LLC. - 0946-2171 .- 1432-0649. ; 96:4, s. 645-656
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Tidskriftsartikel (refereegranskat)abstract
- Time-resolved laser-induced incandescence (LII) has been developed rapidly during the last decade as a useful non-intrusive technique for particle size determination. Still several parameters should be investigated in order to improve the accuracy of LII for particle sizing and the spatial distribution of the laser energy is one of these. Generally a top-hat profile is recommended, as this ensures a uniform heating of all particles in the measurement volume. As it is generally not straightforward to create a uniform beam profile, it is of interest to establish the influence of various profiles on the evaluated particle sizes. In this work we present both an experimental and a theoretical investigation of the influence of the spatial profile on evaluated sizes. All experiments were carried out using a newly developed setup for two-colour LII (2C-LII) which provides online monitoring of both the spatial and temporal profile as well as the laser pulse energy. The LII measurements were performed in a one-dimensional premixed sooting ethylene/air flame, and evaluated particle sizes from LII were compared with thermophoretically sampled soot particles analysed using transmission electron microscopy (TEM). The results show that although there is some influence of the spatial laser energy distribution on the evaluated particle sizes both in modelling and experiments, this effect is substantially smaller than the influence of the uncertainties in gas temperature and the thermal accommodation coefficient.
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