| 1. |
- Afzelius, Mikael, et al.
(författare)
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Development of multipoint vibrational coherent anti-Stokes Raman spectroscopy for flame applications
- 2006
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Ingår i: Applied Optics. - 2155-3165. ; 45:6, s. 1177-1186
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Tidskriftsartikel (refereegranskat)abstract
- A novel technique for coherent anti-Stokes Raman spectroscopy (CARS) measurements in multiple points is presented. In a multipass cavity the pump and Stokes laser beams are multiply reflected and refocused into a measurement volume with an adjustable number of separated points along a line. This optical arrangement was used in a vibrational CARS setup with planar BOXCARS phase-matching configuration. The CARS spectra from spatially separated points were recorded at different heights on a CCD camera. Measurements of temperature profiles were carried out in the burned gas zone of a premixed one-dimensional flame to demonstrate the applicability of this method for temperature measurements in high-temperature regions. The ability to measure in flames with strong density gradients was demonstrated by simultaneous measurements of Q-branch spectra of N-2 and CO in a Wolfhard-Parker burner flame. Interference phenomena found in multipoint spectra are discussed, and possible solutions are proposed. Merits and limitations of the technique are discussed. (c) 2006 Optical Society of America.
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| 2. |
- Brackmann, Christian, 1973, et al.
(författare)
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CARS microscopy of lipid stores in yeast: the impact of nutritional state and genetic background
- 2009
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Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 0377-0486 .- 1097-4555. ; 40:7, s. 748-756
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Tidskriftsartikel (refereegranskat)abstract
- We have developed a protocol for sub-micrometer resolved and chemically specific imaging of lipid storage in vivo employing coherent anti-Stokes Raman scattering (CARS) microscopy of one of the most important model organisms Saccharomyces cerevisiae - the yeast cell. By probing the carbon-hydrogen vibration using the nonlinear process of CARS, lipid droplets in the yeast cells clearly appear, as confirmed by comparative studies on relevant labeled organelles using two-photon fluorescence microscopy. From the images, unique quantitative data can be deduced with high three-dimensional resolution, such as the volume, shape, number, and intracellular location of the neutral lipid stores. We exemplify the strength and usability of the method for two cases: the impact on lipid storage of the nutritional condition (starvation and type of carbon source available) as well as of genetic modification of two fundamental metabolic regulation pathways involving carbohydrate and lipid storage (BCY1 and DGA1, LRO1, ARE1/2 deletions), respectively. While the impact of carbon source on the total cellular lipid volume was minimal, long-term starvation induces a significant accumulation of lipid droplets. We also confirm that the lipid-storage-deficient mutant is indeed unable to synthesize lipid droplets, and that the inability of the bcy1-mutant to store carbohydrates is compensated by a two-fold increase in stored neutral lipids. We note that there is a significant cell-to-cell variability in neutral lipid storage in general, i.e. that there is a correspondence to the noise found for gene expression also in lipidomics. Copyright (C) 2009 John Wiley & Sons, Ltd.
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| 3. |
- Brackmann, Christian, et al.
(författare)
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Quantitative measurements of species and temperature in a DME-air counterflow diffusion flame using laser diagnostic methods
- 2006
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Ingår i: Combustion Science and Technology. - : Informa UK Limited. - 1563-521X .- 0010-2202. ; 178:6, s. 1165-1184
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Tidskriftsartikel (refereegranskat)abstract
- A diffusion flame of dimethyl ether (DME) and air in a counterflow burner has been investigated experimentally by means of different laser-based methods. Quantitative measurements of temperature, O-2 concentration, and OH concentration have been carried out using dual broadband rotational coherent anti-Stokes Raman Spectroscopy (CARS), Rayleigh scattering and laser-induced fluorescence (LIF). Furthermore a qualitative formaldehyde profile has been measured using LIF. The measured profile has been compensated for fluorescence signal quenching and the Boltzmann distribution to obtain a representative qualitative formaldehyde profile for the flame.
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| 4. |
- Brackmann, Christian, et al.
(författare)
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Strategies for formaldehyde detection in flames and engines using a single-mode Nd:YAG/OPO laser system
- 2005
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Ingår i: Applied Spectroscopy. - : SAGE Publications. - 0003-7028 .- 1943-3530. ; 59:6, s. 763-768
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents technical developments for the detection of formaldehyde (CH2O) using laser-induced fluorescence. The easily accessible third harmonic of the Nd:YAG laser at 355 nm was used for excitation of formaldehyde. In order to investigate potential background fluorescence, e.g., from large molecules such as polyaromatic hydrocarbons, special attention was paid to investigating the possibility of scanning the wavelength of a single-mode Nd: YAG laser under the gain profile, ∼3 cm-1, on and off resonance. Furthermore, a technique for simultaneous detection of formaldehyde and OH using one laser system is presented. The single-mode Nd: YAG laser at 355 nm in combination with an optical parametric oscillator (OPO) laser tuned to 283 nm was used for simultaneous two-dimensional imaging of both species using one charge-coupled device (CCD) detector equipped with a dual filter image separator. The techniques are demonstrated with measurements in laboratory flames and the combined measurements are also demonstrated in an engine.
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| 5. |
- Brackmann, Christian, et al.
(författare)
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Strategies for formaldehyde engines using a single-mode detection in flames and Nd : YAG/OPO laser system
- 2005
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Ingår i: Applied Spectroscopy. - 1943-3530. ; 59:6, s. 763-768
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents technical developments for the detection of formaldehyde (CH2O) using laser-induced fluorescence. The easily accessible third harmonic of the Nd:YAG laser at 355 nm was used for excitation of formaldehyde. In order to investigate potential background fluorescence, e.g., from large molecules such as polyaromatic hydrocarbons, special attention was paid to investigating the possibility of scanning the wavelength of a single-mode Nd:YAG laser under the gain profile, similar to 3 cm(-1), on and off resonance. Furthermore, a technique for simultaneous detection of formaldehyde and 011 using one laser system is presented. The single-mode Nd:YAG laser at 355 nm in combination with an optical parametric oscillator (OPO) laser tuned to 283 nm was used for simultaneous two-dimensional imaging of both species using one charge-coupled device (CCD) detector equipped with a dual filter image separator. The techniques are demonstrated with measurements in laboratory flames and the combined measurements are also demonstrated in an engine.
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| 6. |
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| 7. |
- Enejder, Annika, 1969, et al.
(författare)
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CARS and SHG microscopy for the characterization of bacterial cellulose
- 2009
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Ingår i: Progress in Biomedical Optics and Imaging - Proceedings of SPIE. - : SPIE. - 1605-7422. - 9780819474292 ; 7183
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- We have developed a protocol employing dual-mode non-linear microscopy for the monitoring of the biosynthesis of bacterial cellulose at a single-fiber level, with the fundamental aim to achieve a product with material properties similar to those of human blood vessels. Grown in a tubular geometry it could then be used as a natural and biocompatible source of replacement tissue in conjunction with cardiovascular surgery. The bacteria (Acetobacter xylinum) were selectively visualized based on the CH2 vibration of its organic macromolecular contents by the Coherent Anti-Stokes Raman Scattering (CARS) process and, simultaneously, the non-centrosymmetrically ordered, birefringent cellulose fibers were depicted by the Second Harmonic Generation (SHG) process. This dual-channel detection approach allows the monitoring of cellulose-fiber formation in vivo and to determine the influence of e. g. different growth conditions on fiber thickness and orientation, their assembling into higher-order structures and overall network density. The bacterial and fiber distributions were monitored in a simple microscope cultivation chamber, as well as in samples harvested during the actual fermentation process of tubular cellulose grafts. The CARS and SHG co-localization images reveal that highest bacterial population densities can be observed in the surface regions of the cellulose tissue, where the primary growth presumably takes place. The cellulose network morphology was also compared with that of human arteries and veins, from which we conclude that the cellulose matrix is comparatively homogeneous in contrast to the wavy band-like supra-formations of collagen in the native tissue. This prompts for sophisticated fermentation methods by which tunnels and pores of appropriate sizes and shapes can be introduced in the cellulose network in a controllable way. With this protocol we hope to contribute to the fundamental knowledge required for optimal production of bioengineered cellulose tissues, eventually being available for clinical use.
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| 8. |
- Enejder, Annika, 1969, et al.
(författare)
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CARS Microscopy
- 2008
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Ingår i: Biomedical Imaging: Principles and Applications. - 9780813816784
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 9. |
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| 10. |
- Enejder, Annika, 1969, et al.
(författare)
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CARS microscopy for the monitoring of lipid storage in C. elegans
- 2008
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Ingår i: Proc. Soc. Photo-Opt. Instrum. Eng.. ; 6860
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Konferensbidrag (refereegranskat)abstract
- After several years of proof-of-principle measurements and focus on technological development, it is timely to make full use of the capabilities of CARS microscopy within the biosciences. We have here identified an urgent biological problem, to which CARS microscopy provides unique insights and consequently may become a widely accepted experimental procedure. In order to improve present understanding of mechanisms underlying dysfunctional metabolism regulation reported for many of our most wide-spread diseases (obesity, diabetes, cardio-vascular diseases etc.), we have monitored genetic and environmental impacts on cellular lipid storage in the model organism C. elegans in vivo in a full-scale biological study. Important advantages of CARS microscopy could be demonstrated compared to present technology, i.e. fluorescence microscopy of labelled lipid stores. The fluorescence signal varies not only with the presence of lipids, but also with the systemic distribution of the fluorophore and the chemical properties of the surrounding medium. By instead probing high-density regions of CH bonds naturally occurring in the sample, the CARS process was shown to provide a consistent representation of the lipid stores. The increased accumulation of lipid stores in mutants with deficiencies in the insulin and transforming growth factor signalling pathways could hereby be visualized and quantified. Furthermore, spectral CARS microscopy measurements in the C-H bond region of 2780-2930 cm-1 provided the interesting observation that this accumulation comes with a shift in the ordering of the lipids from gel- to liquid phase. The present study illustrates that CARS microscopy has a strong potential to become an important instrument for systemic studies of lipid storage mechanisms in living organisms, providing new insights into the phenomena underlying metabolic disorders.
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| 11. |
- Enejder, Annika, 1969, et al.
(författare)
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Dual-CARS microscopy
- 2007
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Ingår i: PROCEEDINGS OF THE SOCIETY OF PHOTO-OPTICAL INSTRUMENTATION ENGINEERS (SPIE). - 0277-786X. - 9780819465559 ; 6442:15
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Konferensbidrag (refereegranskat)abstract
- We present a new Coherent Anti-Stokes Raman Scattering (CARS) microscopy technique for label-free imaging of bio-molecules in living cells; dual-CARS microscopy. The use of three synchronized laser pulses in a dual-pump/dual-detection configuration enables imaging of two species with different molecular vibrations simultaneously, as well as acquisition of images free of non-resonant background. We show the power of the method by imaging deuterated nonadecane slowly diffusing into a suspension of living yeast cells in medium, clearly distinguishing the medium and the lipid droplets in the cells by probing the CH2 vibration from the D-nonadecane by probing the CD vibration. In addition, images of lipid stores in living C. elegans nematodes free of non-resonant background are shown. This results in a significant enhancement of the image contrast, allowing the visualization of emerging, low-density lipid stores in a dauer larva, difficult to distinguish in conventional CARS microscopy. The separation of the non-resonant background is shown to be beneficial also when monitoring molecules with weak vibrational modes. The improved sensitivity obtained is illustrated by probing the C=C vibration in polyunsaturated lipids extracted from fish. This enables the monitoring of the degree of unsaturation of lipids, a high value of which is reported in foods known to have positive effects on human health.
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| 12. |
- Hagmar, Jonas, 1974, et al.
(författare)
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Image analysis in non-linear microscopy
- 2008
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Ingår i: Journal of Optical Society of America. ; 25, s. 2195-2206
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Tidskriftsartikel (refereegranskat)abstract
- The ability to automatically extract quantitative data from non-linear microscopy images is here explored, taking their non-linear character into account. Objects of different degree of complexity were investigated: theoretical images of spherical objects, experimentally collected Coherent Anti-Stokes Raman Scattering images of polystyrene spheres in background generating agar, well-separated lipid droplets in living yeast cells and conglomerations of lipid droplets in living C. elegans nematodes. The in linear microscopy useful measure of Full-Width-at-Half-Maximum (FWHM) was shown to provide inadequate measures of object size due the non-linear density dependence of the signal. Instead, the capability of four state-of-the-art image analysis algorithms was evaluated. Among these Local thresholding was found to be the widest applicable segmentation algorithm.
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| 13. |
- Hagmar, Jonas, 1974, et al.
(författare)
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Image analysis of lipid deposits in living organisms visualized by CARS microscopy
- 2007
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Ingår i: Proc. Soc. Photo-Opt. Instrum. Eng. (SPIE). - 9780819466297 ; 6511:17
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Konferensbidrag (refereegranskat)abstract
- CARS microscopy is a novel technique for imaging bio-molecules in living cells using the molecular vibration as contrast mechanism. Global and local thresholding, state-of-the art image analysis techniques (watersheds, level sets) and a recent technique for anisotropic Gaussian fitting are used to segment lipid droplets in CARS microscopy images of, S. cerevisiae (yeast cells). The ability to extract quantitative information, such as vesicle size, is validated by means of images of polystyrene beads of well-defined size. Theoretical modeling of the CARS signal is performed, linking the physical object to its representation as a CARS microscopy image, as an attempt to take the non-linear relationship into account for refined image analysis. Theoretically modeled images of polystyrene beads correspond well to those experimentally obtained. Of the image analysis tools, it is found that global and local thresholding have limited use for segmentation of CARS microscopy images. Watershed and level set segmentation underestimate the size of a segmented object. Anisotropic Gaussian fitting overestimates the size of the object in the presence of non-resonant background. Reduced overestimation is achieved by background suppression. This emphasizes the importance of background removal in the CARS microscopy images, both experimentally as well as analytically. Automated image analysis of CARS microscopy images of S. cerevisiae is shown to be an excellent approach for in-depth studies of fat deposits in living organisms, with prospects for including human cells. Such a methodology will be of outmost importance for improved understanding of the mechanisms behind the development of obesity.
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| 14. |
- Hellerer, Thomas, 1973, et al.
(författare)
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Monitoring of lipid storage in Caenorhabditis elegans using coherent anti-Stokes Raman scattering (CARS) microscopy
- 2007
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 104:37, s. 14658-14663
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Tidskriftsartikel (refereegranskat)abstract
- Better understanding of the fundamental mechanisms behind metabolic diseases requires methods to monitor lipid stores on single-cell level in vivo. We have used Caenorhabditis elegans as a model organism to demonstrate the limitations of fluorescence microscopy for imaging of lipids compared with coherent anti-Stokes Raman scattering (CARS) microscopy, the latter allowing chemically specific and label-free imaging in living organisms. CARS microscopy was used to quantitatively monitor the impact of genetic variations in metabolic pathways on lipid storage in 60 specimens of C. elegans. We found that the feeding-defective mutant pha-3 contained a lipid volume fraction one-third of that found in control worms. In contrast, mutants (daf-2, daf-4 dauer) with deficiencies in the insulin and transforming growth factors (IGF and TGF-beta) signaling pathways had lipid volume fractions that were 1.4 and 2 times larger than controls, respectively. This was observed as an accumulation of small-sized lipid droplets in the hypodermal cells, hosting as much as 40% of the total lipid volume in contrast to the 9% for the wild-type larvae. Spectral CARS microscopy measurements indicated that this is accompanied by a shift in the ordering of the lipids from gel to liquid phase. We conclude that the degree of hypodermal lipid storage and the lipid phase can be used as a marker of lipid metabolism shift. This study shows that CARS microscopy has the potential to become a sensitive and important tool for studies of lipid storage mechanisms, improving our understanding of phenomena underlying metabolic disorders.
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| 15. |
- Nogenmyr, Karl-Johan, et al.
(författare)
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Large Eddy Simulation and Experiments of Stratified Lean Premixed Methane/Air Turbulent Flames
- 2007
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Ingår i: Proceedings of the Combustion Institute. - : Elsevier BV. - 1540-7489. ; 31:1, s. 1467-1475
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a joint large eddy simulation and laser diagnostic investigation of premixed turbulent low swirl flames. A lean premixed methane/air mixture, of the equivalence ratio 0.60-0.66, is injected from a 50 mm diameter low swirl burner to a low speed co-flowing air at room temperature and pressure. The level-set G-equation is employed to simulate the inner layer flame front. Flamelet chemistry is used to determine the flame properties in the reactive zones. Mixing and heat transfer in the post-flame zone down-stream are modeled using transport equations. In addition to large eddy simulation, simultaneous 2-D laser induced fluorescence of OH and 2-D particle image velocimetry are used to characterize the basic flame structure. Laser Doppler velocimetry is employed to further analyze the flow velocity along the central axis above the burner, and 2-D filtered Rayleigh scattering is used to measure the temperature field in the lower part of the flame. A bowl-shaped, highly wrinkled turbulent flame is stabilized at a position about one-half diameter above the burner. The flame consists of two distinct parts; around the burner axis, a premixed flame with uniform mixture fraction is stabilized in the low speed flow region induced by the inflow swirl; off the axis of the burner, a stratified lean premixed flame is found in the shear layer of the flow field. Flame holes (local extinction) owing to overly lean mixtures are observed in the off-axis lean stratified part of the flame. A unified level-set G-equation is developed to model the flame holes. The basic flow and flame structure from the model simulations are compared to the laser diagnostic measurements; the height of flame stabilization (lift-off height), the mean temperature profile, and the mean axial and radial velocity components together with rms velocity components are in fairly good agreement with measurement data. © 2006 The Combustion Institute. Published by Elsevier Inc. All rights reserved.
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| 16. |
- Petersson, Per, et al.
(författare)
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Simultaneous PIV/PH-PLIF, Rayleigh thermometry/OH-PLIF and stereo PIV measurements in a low-swirl-flame
- 2007
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Ingår i: Applied Optics. - 2155-3165. ; 46:19, s. 3928-3936
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Tidskriftsartikel (refereegranskat)abstract
- The diagnostic techniques for simultaneous velocity and relative OH distribution, simultaneous temperature and relative OH distribution, and three component velocity mapping are described. The data extracted from the measurements include statistical moments for inflow fluid dynamics, temperature, conditional velocities, and scalar flux. The work is a first step in the development of a detailed large eddy simulation (LES) validation database for a turbulent, premixed flame. The low-swirl burner used in this investigation has many of the necessary attributes for LES model validation, including a simplified interior geometry; it operates well into the thin reaction zone for turbulent premixed flames, and flame stabilization is based entirely on the flow field and not on hardware or pilot flames.
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| 17. |
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| 18. |
- Seyfried, Hans, et al.
(författare)
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Optical investigations of the combustion characteristics of a gas turbine pilot burner
- 2007
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Ingår i: Collection of Technical Papers - 45th AIAA Aerospace Sciences Meeting. ; 8, s. 5630-5641
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Konferensbidrag (refereegranskat)abstract
- This paper presents the application of several optical measurement techniques for the characterization of the combustion behavior of the pilot burner of a gas turbine combustor developed according to the lean premixed prevaporized (LPP) concept. The vaporization of the kerosene fuel (Jet-A) and its consequent mixing with air has been visualized using combined Laser-Induced Fluorescence (LIF) and Mie scattering measurements. In addition the feasibility of using Laser-Induced Incandescence (LII) for soot characterization has also been investigated. Furthermore, spontaneous flame emission (i.e. chemiluminescence and thermal radiation) have been measured providing information on the overall characteristics of the combustion. The LIF/Mie measurements can also be used to estimate the length and time scales for evaporation and mixing with air of Kerosene (Jet-A) for the LP(P)4 pilot burner.
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| 19. |
- Vestin, Fredrik, et al.
(författare)
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Dual-broadband rotational CARS thermometry in the product gas of hydrocarbon flames
- 2005
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Ingår i: Symposium (International) on Combustion. - : Elsevier BV. - 0082-0784. ; 30:1, s. 1673-1680
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Tidskriftsartikel (refereegranskat)abstract
- Coherent anti-Stokes Raman spectroscopy (CARS) is an established technique for gas-phase thermometry in combustion. In this work, rotational CARS in the dual-broadband approach has been investigated for flame thermometry in the product gas of ethylene/air flames in a wide range of equivalence ratios (0.5 < phi < 2.5). The nitrogen lines dominated the rotational CARS spectra in the whole equivalence range, but for fuel-lean flames also oxygen lines gave significant spectral contributions. Therefore, the temperature evaluation was based on spectral fitting of both nitrogen and oxygen. Product gas species such as carbon dioxide, water, carbon monoxide, and hydrogen contribute to the non-resonant susceptibility of the gas and influence the nitrogen and oxygen linewidths through collisions. In this work, the main focus was on the influence of these collisions on the nitrogen and oxygen Raman linewidths and consequently the evaluated temperature in the product gas of flames. In the range of studied equivalence ratios with various amounts of different product gas species, the evaluated temperature was raised up to 45 K when including broadening from CO2, H2O, and CO on the measured nitrogen and oxygen lines. It was also concluded that H2O was the main contributor in all non-sooting flames. The influence of the non-resonant susceptibility in the spectral evaluation is discussed, and its coupling to the inclusion of the line broadening from product gas species as well. It has thus been shown that line-broadening effects from product gas species are highly important for quantitative rotational CARS thermometry in flames. (c) 2004 The Combustion Institute.
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