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- Bengtsson, Per Erik, et al.
(författare)
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C2 Production and Excitation in Sooting Flames using Visible Laser Radiation : Implications for Diagnostics in Sooting Flames
- 1991
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Ingår i: Combustion Science and Technology. - : Informa UK Limited. - 0010-2202 .- 1563-521X. ; 77:4-6, s. 307-318
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Tidskriftsartikel (refereegranskat)abstract
- Swan band emission of C2. which had been produced and excited (d3∏x←a 3∏u, Δ v = 0) by focused, tunable, visible laser radiation, was studied in sooting ethylene flames. The C2signal from the sooting regions of the flames was found to be proportional to the measured volume fractions of soot, indicating laser-vaporized soot to be the source of the signal, and as such it can be used as a diagnostic tool for point measurements of the volume fraction of soot. C2emission was detected for all incident wavelengths between 485 and 540 nm, with a C2signal 1–2 orders of magnitude higher when the wavelength was tuned to a C2 resonance than when tuned to a wavelength between the Swan bands. High concentrations of laser-produced C2 and emission from C2Swan bands can, through interference effects, limit the applicability of laser diagnostic techniques to sooting flames.
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- Bengtsson, Per Erik, et al.
(författare)
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Dual-broadband rotational cars measurements in an IC engine
- 1994
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Ingår i: Symposium (International) on Combustion. - 0082-0784. ; 25:1, s. 1735-1742
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Tidskriftsartikel (refereegranskat)abstract
- This is the first report of pure rotational coherent anti-Stokes Raman spectroscopy (CARS) measurementsin an internal combustion (IC) engine. Single-shot, dual-broadband rotational CARS (DB-RCARS) spectra were recorded both prior to ignition and in the postcombustion gases. From these spectra, both temperature and relative oxygen concentrations were evaluated. The pressure was registered simultaneously with the CARS measurements in the spark-ignition engine burning natural gas and air. Prior to ignition, normally at temperatures below 1000 K and pressures below 2 MPa, a rotational CARS spectrum is very temperature sensitive, and the technique can be used for temperature measurements with high accuracy. Evaluated temperatures show a negligible dependence on uncertainties in parameters such as the nonresonant susceptibility of the gas and the slit width. Moreover, no collisional narrowing of the lines has to be taken into account. The relative standard deviation of evaluated temperatures and of relative oxygen concentrations from single-shot measurements were as low as 1, and 1.4-1.9%, respectively. In the postcombustion gases at temperatures above 2000 K and pressures above 1.5 MPa, the nonresonant CARS background gave a large contribution to the total spectrum. In this temperature and pressure range, the evaluated values of temperature and nonresonant susceptibility are not independent, and the nonresonant susceptibility had to be fixed at a precalculated value to get a reliable temperature evaluation. The avantages and disadvantages of rotational CARS in comparison with vibrational CARS for IC engine measurements are discussed.
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- Bengtsson, Per Erik, et al.
(författare)
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Rotational cars thermometry in sooting flames
- 1992
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Ingår i: Combustion Science and Technology. - : Informa UK Limited. - 0010-2202 .- 1563-521X. ; 81:1-3, s. 129-140
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Tidskriftsartikel (refereegranskat)abstract
- Coherent anti-Stokes Raman scattering of pure rotational transitions, rotational CARS, is demonstrated as an efficient method for temperature determination in sooting flames. The dual broadband CARS approach was used to measure temperature profiles in premixed, sooting ethylene flames at atmospheric pressure by probing the nitrogen gas. The recorded spectra were of equally high quality in non-sooting and sooting flames with volume fractions of soot of up to 7 x 10 7 cm3 soot/cm3The advantages of rotational CARS in comparison with several other techniques for the measurement of temperatures in sooting flames, and the general applicability of the technique to different combustion conditions, are discussed. Potential limitations in the application of rotational CARS to sooting flames that are more heavily sooting than the ones investigated in this study, are outlined.
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- Bengtsson, Per-Erik, et al.
(författare)
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Vibrational CARS thermometry in sooty flames: Quantitative evaluation of C2 absorption interference
- 1990
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Ingår i: Combustion and Flame. - 0010-2180. ; 82:2
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Tidskriftsartikel (refereegranskat)abstract
- The application of nitrogen vibrational CARS thermometry to sooty, premixed, atmospheric pressure flames has been investigated using a Nd:YAG laser based system. It was found that laser-produced C2 radicals strongly absorb part of the fundamental band peak in the CARS spectrum. This was the most severe interference to the CARS signal. A quantitative investigation of temperature errors caused by the C2 absorption effect is presented. The correlation between the absorption interference and the soot volume fraction was examined for different flame conditions. Also, the increase of the nonresonant susceptibility in sooty flame regions is clearly illustrated and its effect on thev evaluated temperature is quantitatively determined. The single-shot temperature standard deviation has also been investigated in flames with different soot loadings. Finally, other interference effects to the CARS signals in sooty flames are described and discussed.
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- Lissner, Lauren, 1956, et al.
(författare)
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Energy and macronutrient intake in relation to cancer incidence among Swedish women
- 1992
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Ingår i: European Journal of Clinical Nutrition. ; 46, s. 501-507
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Tidskriftsartikel (refereegranskat)abstract
- Department of Primary Health Care, Gothenburg University, Sweden. Two dietary reporting methods were used to examine associations between macronutrient intake and subsequent cancer incidence in a cohort of Swedish women born between 1908 and 1930. 1361 subjects gave 23-h dietary recalls at their baseline examinations in 1968-1969, and 412 of them also provided detailed dietary histories. The cohort was followed up 19 years later by means of linkages with the National Cancer and Death Registries. Both dietary methods indicated that subjects who were ranked in the highest tertile of energy intake, relative to the lowest, were at significantly greater risk of developing cancer (all-site). Relative risks across energy intake tertiles were 1, 1.15 and 2.04, respectively, using the dietary history method and 1, 1.02 and 1.55 using the 24-h recall data. Examination of specific macronutrient energy sources indicated that dietary fat and carbohydrate are likely to have made the largest contribution to this association. However, after adjustment for total energy, none of the individual macronutrients was significantly associated with all-site cancer, by either dietary reporting method. When expressed as a percentage of total energy, low protein density of the diet was associated with increased cancer risk, by both dietary methods. However, this appeared to be a function of high energy intake rather than low protein intake. Simultaneous statistical adjustment for seven potential confounders of the association between energy intake and cancer was performed using both the 24-h recall and the dietary history data.(ABSTRACT TRUNCATED AT 250 WORDS) PMID: 1623854 [PubMed - indexed for MEDLINE]
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- Martinsson, Lars, et al.
(författare)
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A test of different rotational Raman linewidth models: Accuracy of rotational coherent anti-Stokes Raman scattering thermometry in nitrogen from 295 to 1850 K
- 1993
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 99:4, s. 2466-2477
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Tidskriftsartikel (refereegranskat)abstract
- Rotational Raman linewidths calculated from three different models have been used in temperature measurements by rotational coherent anti-Stokes Raman scattering (CARS)—a semiclassical ab initio model, the modified exponential energy gap model (MEG), and the energy corrected sudden scaling law (ECS). Experimental rotational CARS spectra were generated, using the dual-broadband approach, in pure nitrogen at atmospheric pressure in a heat pipe in the temperature range from 295 to 1850 K. Below 1500 K, the temperatures evaluated using the ECS linewidths agreed with the heat-pipe temperatures to within 20 K. Above 1500 K, the errors in the evaluated temperatures increased steeply for all linewidth models, reaching errors of several hundreds of Kelvins at 1850 K. This behavior of the evaluated temperature is probably caused by the uncertainty in the values of the rotational Raman linewidths for high rotational states at high temperatures. This work therefore illustrates that rotational CARS can be used for experimentally studying Raman linewidths and in particular their dependence on temperature and rotational quantum number. The influence of different experimental parameters on the evaluated temperatures is discussed, and the spectral synthesis program is presented. The Journal of Chemical Physics is copyrighted by The American Institute of Physics.
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