| 1. |
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| 2. |
- Andersson, Jennie, 1986, et al.
(författare)
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In-Behind Performance of an Ice Classed Propeller in Model and Ship-Scale
- 2021
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Ingår i: Proceedings of IX International Conference on Computational Methods in Marine Engineering, MARINE 2021.
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Konferensbidrag (refereegranskat)abstract
- A CFD study in both model and ship-scale is conducted to compare the in-behind performance of an ice classed to a conventional propeller. In ship-scale the performance degradation of the ice classed propeller in-behind is less than in open water. Through evaluation of the blades performance tangentially and radially in the wake it is observed that the ice classed blade is superior at very low load, the blunter profiles is less sensitive to negative angles of attack. Contrary, in model-scale a larger difference in performance is noted between the propellers in-behind than expected from open water performance. This is most probably related to differences in Reynolds number between model-scale open water and self-propulsion tests, the thicker profiles of the ice classed propeller makes it additionally punished by the low Reynolds numbers of the self-propulsion tests.
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| 3. |
- Andersson, Jennie, 1986, et al.
(författare)
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On the Selection of Optimal Propeller Diameter for a 120-m Cargo Vessel
- 2021
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Ingår i: Journal of Ship Research. - 1542-0604 .- 0022-4502. ; 65:2, s. 153-166
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Tidskriftsartikel (refereegranskat)abstract
- In the preliminary design of a propulsion unit, the selection of propeller diameter is most commonly based on open water tests of systematic propeller series. The optimum diameter obtained from the propeller series data is, however, not considered to be representative for the operating conditions behind the ship, instead a slightly smaller diameter is often selected. We have used computational fluid dynamics to study a 120-m cargo vessel with an integrated rudder bulb–propeller hubcap system and a four-bladed propeller series, to increase our understanding of the hydrodynamic effects influencing the optimum. The results indicate that a 3–4% smaller diameter is optimal in behind conditions in relation to open water conditions at the same scale factor. The reason is that smaller, higher loaded propellers perform better together with a rudder system. This requires that the gain in transverse kinetic energy losses thanks to the rudder overcomes the increase in viscous losses in the complete propulsion system.
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| 4. |
- Andersson, Jennie, 1986, et al.
(författare)
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On the Selection of Optimal Propeller Diameter for a 120m Cargo Vessel
- 2018
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Ingår i: SNAME 15th Propeller and Shafting Symposium, PSS 2018.
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Konferensbidrag (refereegranskat)abstract
- In the preliminary design of a propulsion unit the selection of propeller diameter is most commonly based on open water tests of systematic propeller series. The optimum diameter obtained from the propeller series data is however not considered to be representative for the operating conditions behind the ship, instead a slightly smaller diameter is often selected. We have used computational fluid dynamics (CFD) to study a 120m cargo vessel with an integrated rudder bulb-propeller hubcap system and a 4-bladed propeller series, to increase our understanding of the hydrodynamic effects influencing the optimum. The results indicate that a 3-4 % smaller diameter is optimal in behind conditions in relation to open water conditions at the same scale factor. The reason is that smaller, higher loaded propellers perform better together with a rudder system. This requires that the gain in transverse kinetic energy losses thanks to the rudder overcomes the increase in viscous losses in the complete propulsion system
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| 5. |
- Andersson, Jennie, 1986, et al.
(författare)
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Propeller-hull interaction beyond the propulsive factors-A case study on the performance of different propeller designs
- 2022
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Ingår i: Ocean Engineering. - : Elsevier BV. - 0029-8018. ; 256
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Tidskriftsartikel (refereegranskat)abstract
- The propulsive factors are critical for scaling of model-test data, and hence important for the final power prediction. When comparing different propulsion systems based on model-scale tests, differences in propulsive factors, and hence the propeller-hull interaction, are often not well understood. In this study the propeller-hull interaction is instead described and compared using CFD for three different propulsion systems, a tip-unloaded ice-classed propeller, an ice-classed propeller with conventional radial load distribution and a non ice-classed propeller with conventional radial load distribution. To post-process the results KT/KQ is evaluated for one blade around a revolution and complemented with radial distributions of the same measure. Both tip-unloaded blades and sharp leading edges suffer in-behind due to poor performance at low load. Open water performance dependency on Reynolds number reveals that ice-classed propellers are more negatively influenced by the low Reynolds numbers of self-propulsion tests. Further, it is noted that a more even radial load distribution favours a low thrust deduction factor. Since the propulsive factors to a large extent are influenced by scale-effects and also due to that their association to the observed hydrodynamics makes the commonly applied scaling procedure of them questionable, they are not considered representative for ship-scale power prediction.
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| 6. |
- Axaeus, Jennie, 1974-, et al.
(författare)
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Portar till språk och litteratur : CSL 2007
- 2007
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Bok (övrigt vetenskapligt/konstnärligt)abstract
- Språk och litteratur öppnar portar till nya världar. Detta var temat för 2007 års CSL-dag. I denna bok har vi samlat fjorton av bidragen som presenterades på konferensen, skrivna av forskare och studenter vid Karlstads universitet.Håller engelskan på att förstöra svenskan? Är dagens elever sämre på att skriva än ungdomarna var för tjugo år sedan? Skall vi ha en litteraturkanon i skolan - och läser eleverna över huvud taget böcker nu för tiden? Detta är några av de frågor som ställs i artiklarna där svaren kanske kan överraska.Andra artiklar handlar om hur man stimulerar elever till att läsa och skriva, problematiken när det gäller att undervisa i svenska som andraspråk och varför elever väljer - eller inte väljer - att studera något annat främmande språk än engelska. Porten kanske finns där - men den är inte alltid helt lätt att öppna!
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| 7. |
- Dreij, Kristian, et al.
(författare)
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Cancer Risk Assessment of Airborne PAHs Based on in Vitro Mixture Potency Factors
- 2017
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 51:15, s. 8805-8814
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Tidskriftsartikel (refereegranskat)abstract
- Complex mixtures of polycyclic aromatic hydrocarbons (PAHs) are common environmental pollutants associated with adverse human health effects including cancer. However, the risk of exposure to mixtures is difficult to estimate, and risk assessment by whole mixture potency evaluations has been suggested. To facilitate this, reliable in vitro based testing systems are necessary. Here, we investigated if activation of DNA damage signaling in vitro could be an endpoint for developing whole mixture potency factors (MPFs) for airborne PAHs. Activation of DNA damage signaling was assessed by phosphorylation of Chid and H2AX using Western blotting. To validate the in vitro approach, potency factors were determined for seven individual PAHs which were in very good agreement with established potency factors based on cancer data in vivo. Applying the method using Stockholm air PAH samples indicated MPFs with orders of magnitude higher carcinogenic potency than predicted by established in vivo-based potency factors. Applying the MPFs in cancer risk assessment suggested that 45.4 (6% of all) cancer cases per year in Stockholm are due to airborne PAHs. Applying established models resulted in <1 cancer case per year, which is far from expected levels. We conclude that our in vitro based approach for establishing MPFs could be a novel method to assess whole mixture samples of airborne PAHs to improve health risk assessment.
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| 8. |
- Eslamdoost, Arash, 1982, et al.
(författare)
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Analysis of Propeller-Hull Interaction Phenomena on a Self-Propelled Axisymmetric Body
- 2017
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Ingår i: 5th Int. Symposium on Marine Propulsor.
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Konferensbidrag (refereegranskat)abstract
- The Reynolds Transport theorem for energy is used to study propeller-hull interaction effects by analyzing different components of energy flux through a control volume around a self-propelled vessel. These components are the axial kinetic energy, the transversal kinetic energy, the turbulent kinetic energy, the internal energy and the pressure work. This energy balance approach is here used to study the influence of propeller diameter on the propulsive power. To this end, propellers of different diameters have been studied in behind condition. In order to keep the incoming wake into the propellers as simple as possible, an axi-symmetric hull shape is employed. The energy fluxes are calculated employing a RANS approach to solve the momentum transport and continuity equations together with the energy equation (the heat transfer equation in fluid). The latter equation is solved to compute the internal energy. The results show a minor difference on interaction effects. However, analyzing the energy flux components and their contribution to the total energy provides an extra tool for better understanding of the interaction effects.
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| 9. |
- Gustafsson, Eva, et al.
(författare)
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Characterization of Particulate Matter in the Hot Product Gas from Indirect Steam Bubbling Fluidized Bed Gasification of Wood Pellets
- 2011
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Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 0887-0624 .- 1520-5029. ; 25:4, s. 1781-1789
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Tidskriftsartikel (refereegranskat)abstract
- This study characterized the particulate matter (PM) formed during the indirect steam bubbling fluidized bed gasification of wood pellets at atmospheric pressure. A system including a dilution probe, a bed of granular activated carbon, and a thermodenuder was used to sample the PM at high temperature with the aim of separating it from condensing inorganic vapors and tars. The particle mass size distribution was bimodal with a fine mode in the <0.5-μm size range and a dominating coarse mode in the >0.5-μm size range. The coarse mode was representatively characterized while condensing inorganic vapors and tars complicated the evaluation of the results for the fine-mode PM. Morphological analysis of the PM indicated that the char content was low. The inorganic fraction was dominated by potassium and chlorine for fine-mode PM and calcium and silicon for coarse-mode PM.
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| 10. |
- Gustafsson, Jennie, 1988-
(författare)
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En hyresmarknad i förändring
- 2023
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Ingår i: Plan : tidskriften för samhällsplanering. - 0032-0560. ; :7, s. 5-7
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Tidskriftsartikel (populärvet., debatt m.m.)
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