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- Rosell, Joakim, et al.
(författare)
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Multi-species PLIF study of the structures of turbulent premixed methane/air jet flames in the flamelet and thin-reaction zones regimes
- 2017
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Ingår i: Combustion and Flame. - : Elsevier BV. - 0010-2180. ; 182, s. 324-338
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Tidskriftsartikel (refereegranskat)abstract
- Simultaneously planar laser-induced fluorescence (PLIF) measurements of OH, CH, CH2O and toluene are carried out to investigate the structures of turbulent premixed methane/air jet flames in the flamelet regime and the thin-reaction zones regime. A premixed flame jet burner of an inner diameter of 1.5 mm is employed. Stoichiometric methane/air mixtures introduced as a jet are ignited and stabilized in a hot co-flow generated by a coaxial porous plug pilot flame surrounding the jet. The Reynolds number for the studied jet ranges from 960 to 11,500 with the characteristic Karlovitz number ranging from 1 to 60. The focus of this study is on the characterization of the structures and turbulent burning velocity of premixed flames in the flamelet and the thin-reaction zones regimes. The preheat zone is analyzed using the CH2O and toluene PLIF fields, whereas the reaction zone is analyzed using the CH and OH PLIF fields. Laser Doppler Anemometer (LDA) measurements are performed to characterize the turbulence field and it is noted that when the Reynolds/Karlovitz number increases a successive thickening of the preheat zone is observed, whereas the reaction zone, characterized by the CH layer maintains nearly the same thickness. The heat release zone, characterized by the combination of the OH and CH2O PLIF fields, is shown to nearly maintain the same thickness under the present experimental conditions. The flame surface wrinkle ratio is shown to be Reynolds number and Karlovitz number independent when the Reynolds number is high enough such that the smallest wrinkle scales reach to the length scales of the thin reaction layers. The global fuel consumption speed of the jet flame is analyzed using the toluene PLIF field and the OH PLIF field. A discrepancy in the two consumption velocities is found as the Karlovitz number increases. This is found to be a result of the broadening of the oxidation zone. These findings provide experimental support to the flamelet and thin-reaction zone regime hypotheses of turbulent premixed combustion.
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| 2. |
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| 3. |
- Sjöholm, Johan, et al.
(författare)
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Simultaneous visualization of OH, CH, CH2O and toluene PLIF in a methane jet flame with varying degrees of turbulence
- 2013
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Ingår i: Proceedings of the Combustion Institute. - : Elsevier BV. - 1540-7489. ; 34, s. 1475-1482
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents simultaneous, single shot planar laser-induced fluorescence (PLIF) imaging of four species: OH, CH, CH2O (formaldehyde) and toluene (C6H5CH3) in methane/air jet flames. The jet flames were stabilized by a flat pilot flame generated using a McKenna type burner. Both flames were operated with a stoichiometric premixed methane/air mixture at room temperature and atmospheric pressure. Several flames, with varying jet flow speeds, were investigated, spanning from laminar (10 m/s jet exit velocity) up to highly turbulent flame conditions, with high Karlovitz numbers, (150 m/s jet exit velocity). Measuring the four species presented above provides detailed information on jet flame structures including the transition from fuel (indicated by the fuel tracer toluene) via the preheat zone (indicated by CH2O) and the inner layer of the flame front (indicated by CH) to the oxidation layer and the postflame zone (both indicated by OH). Furthermore, the simultaneously recorded PLIF images enable the study of correlations between these key species. Especially, overlapping regions between the species in the flames is of interest. The result indicates that turbulence in the present jet flames affects primarily the mixing in the preheat zone and the wrinkling of the reaction layers. It does however not significantly affect the inner flame front structures, represented by the CH radicals, as the thickness of the CH layer remains fairly constant under the investigated flame conditions. (C) 2012 The Combustion Institute. Published by Elsevier Inc. All rights reserved.
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| 4. |
- Sprei, Frances, et al.
(författare)
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How can e-scooter better contribute to a sustainable transport system?
- 2023
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The eSPARK project examines the sustainability profile of the popular shared e-scooters through policy analysis, usage data analysis, surveys, and life cycle assessment. Policies and attempts to regulate e-scooters in Swedish and European cities are studied and discussed with stakeholders. The LCA-results suggest that factors such as how e-scooters are collected and distributed, and the total ridden kilometers have significant impact on their environmental impact. The project also suggests different methods that can support cities to predict the geographical area of the e-scooters and offers insights about how e-scooters are used in the cities. Usage data and the surveys show that they are used by active people in areas with a lot of activities, especially restaurants and clubs. Users are likely to have a driving license, to frequently use a car but also to have a monthly pass for public transport. Thus, escooters have a potential to mitigate congestion on roads and public transport but may lead to more traffic on bike infrastructure instead.
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