| 1. |
- Lejon, Marcus, 1986, et al.
(författare)
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Multidisciplinary Design of a Three Stage High Speed Booster
- 2017
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Ingår i: ASME Turbo Expo 2017: Turbine Technical Conference and Exposition. - : ASME Press. ; 2B-2017
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Konferensbidrag (refereegranskat)abstract
- The paper describes a multidisciplinary conceptual design of an axial compressor, targeting a three stage, high speed, high efficiency booster with a design pressure ratio of 2.8. The paper is outlined in a step wise manner starting from basic aircraft and engine thrust requirements, establishing the definition of the high speed booster interface points and its location in the engine. Thereafter, the aerodynamic 1D/2D design is carried out using the commercial throughflow tool SC90C. A number of design aspects are described, and the steps necessary to arrive at the final design are outlined. The SC90C based design is then carried over to a CFD based conceptual design tool AxCent, in which a first profiling is carried out based on a multiple circular arc blade definition. The design obtained at this point is referred to as the VINK compressor. The first stage of the compressor is then optimized using an in-house optimization tool, where the objective functions are evaluated from detailed CFD calculations. The design is improved in terms of efficiency and in terms of meeting the design criteria put on the stage in the earlier design phases. Finally, some aeromechanical design aspects of the first stage are considered. The geometry and inlet boundary conditions of the compressor are shared with the turbomachinery community on a public server. This is intended to be used as a test case for further optimization and analysis.
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| 2. |
- Yang, Shun-Han, 1987, et al.
(författare)
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Parametric study of the dynamic motions and mechanical characteristics of power cables for wave energy converters
- 2018
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Ingår i: Journal of Marine Science and Technology. - : Springer Science and Business Media LLC. - 0948-4280 .- 1437-8213. ; 23:1, s. 10-29
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Tidskriftsartikel (refereegranskat)abstract
- A case study of a point-absorber wave energy converter (WEC) system is presented. The WEC system forms an array, with several WECs located around a central hub to which they are each connected by a short, free-hanging power cable. The objective of the study is to analyse the dynamic characteristics and estimate the fatigue life of the power cable which is not yet in use or available on the commercial market. Hence, a novel approach is adopted in the study considering that the power cable’s length is restricted by several factors (e.g., the clearances between the service vessel and seabed and the cable), and the cable is subject to motion and loading from the WEC and to environmental loads from waves and currents (i.e., dynamic cable). The power cable’s characteristics are assessed using a numerical model subjected to a parametric analysis, in which the environmental parameters and the cable’s design parameters are varied. The results of the numerical simulations are compared and discussed regarding the responses of the power cables, including dynamic motion, curvature, cross-sectional forces, and accumulated fatigue damage. The effects of environmental conditions on the long-term mechanical life spans of the power cables are also investigated. Important cable design parameters that result in a long power cable (fatigue) service life are identified, and the cable service life is predicted. This study contributes a methodology for the first-principle design of WEC cables that enables the prediction of cable fatigue life by considering environmental conditions and variations in cable design parameters.
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| 3. |
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| 4. |
- Malmek, Karolina, 1990, et al.
(författare)
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Rapid aerodynamic method for predicting the performance of interacting wing sails
- 2024
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Ingår i: Ocean Engineering. - : Elsevier Ltd. - 0029-8018 .- 1873-5258. ; 293
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Tidskriftsartikel (refereegranskat)abstract
- Rapid performance prediction tools are required for the evaluation, optimization, and comparison of different wind propulsion systems (WPSs). These tools should capture viscous aerodynamic flow effects in 3D, particularly the maximum propulsion force, stall angles, and interaction effects between the lift-generating units. This paper presents a rapid aerodynamic calculation method for wing sails that combines a semiempirical lifting line model with a potential flow-based interaction model to account for 3D interaction effects. The method was applied to a WPS that consisted of several wing sails with considerable interaction effects. The results were compared to CFD RANS simulations in 2D and in 3D. For the evaluated validation cases, the interaction model improved the prediction considerably compared to when the interaction was not accounted for. The method provided acceptable driving force, moments, and stall predictions, with negligible computational cost compared to 3D CFD simulations.
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| 5. |
- Marimon Giovannetti, Laura, et al.
(författare)
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Multi-wing sails interaction effects
- 2022
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Ingår i: SNAME 24th Chesapeake Sailing Yacht Symposium, CSYS 2022. - : The Society of Naval Architects and Marine Engineers.
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Konferensbidrag (refereegranskat)abstract
- The effects of multiple wings interacting and the change in efficiency due to those effects as well as optimal sheeting angles are becoming an important area of study with the advent of wind-propelled ships for goods transport. This research presents a first analysis of wind tunnel tests carried out at the University of Southampton R.J. Mitchell wind tunnel where three wings are subject to turbulent flow with Reynolds number in excess of 1 million. A range of possible variations of ship heading and apparent wind angles are tested taking into consideration the blockage effects and the geometrical characteristics of the working section. The forces and moments are captured on each individual wing as well as in the overall wind tunnel balance with 6-components dynamometers. Furthermore, pressure sensors and PIV data are recorded during the tests to provide the experimental campaign with results that can validate both qualitatively and quantitatively the numerical tools developed to aid the design stage of wind propelled vessels.
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| 6. |
- Finnsgård, Christian, 1974
(författare)
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Assembly processes and materials supply systems design
- 2009
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Lean production has over the last decades emerged as the most important paradigm for production, with the assembly processes in focus, including the objective to minimize non-value-adding work. Thus, much attention has been on the work of the assembly operator. However, little focus has been devoted to how the new requirements from lean production have been transformed into materials supply systems supporting the assembly processes. Hence, the purpose of this thesis is to contribute to increased knowledge about the relation between assembly processes and materials supply systems design.A framework is introduced in this thesis, describing how requirements from the assembly processes are transformed by the materials supply system into the actual materials flow. In the results of this thesis, a model structuring requirements in materials supply and assembly processes is proposed, tested, and subsequently different requirements were identified. Materials exposure is introduced as the transition from the materials supply system to the assembly system. Results show that that the materials exposure has a large impact on assembly workstations performance in terms of space needed, non-value-adding work and ergonomics. Further, an experiment showed that the materials exposure factors with the largest impact on picking time were packaging, angle of packaging and height above floor.Major contributions in this thesis are the identification and structuring of requirements in assembly processes and materials supply systems, and explaining how the materials exposure affects the assembly processes. How this knowledge can be applied in the design of new, or redesign of existing, production systems and materials supply processes in particular, is a managerial contribution.
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| 7. |
- Finnsgård, Christian, 1974, et al.
(författare)
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Impact of materials exposure on assembly workstation performance
- 2011
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Ingår i: International Journal of Production Research. - : Informa UK Limited. - 0020-7543 .- 1366-588X. ; 49:24, s. 7253-7274
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Tidskriftsartikel (refereegranskat)abstract
- This paper examines how the choice of materials exposure impacts workstation performance, in terms of non-value-adding work, space requirements and ergonomics. In a typical Swedish automotive setting, components are exposed in wooden pallets with frames beside the assembly line and supplied by forklift truck. In a case study, three workstations on an assembly line were studied and redesigned following the principles of lean production, using smaller plastic containers for the materials exposure. After the redesign, the space required for materials was reduced by 67%, non-value-adding work decreased by 20%, and walking distance was reduced by 52%. Furthermore, the ergonomics for the assembly operator improved greatly, with a 92% reduction of potentially harmful picking activities, thereby almost eliminating potentially harmful body movements. The theoretical contribution of this paper is firstly the development of an analysis model describing the impact of material exposure on workstation performance and secondly development of the existing categorization of work operations to include different materials handling activities. The most important managerial implication is an increased understanding of the relationship between space, ergonomics, non-value-adding work and materials exposure. These findings have direct implications on workstation design in industry.
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| 8. |
- Finnsgård, Christian, 1974
(författare)
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Materials exposure: The interface between materials supply and assembly
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis concerns the supply of components to assembly in production sys- tems, and introduces materials exposure as the interface between materials sup- ply systems and assembly systems. The purpose of the thesis is to explain how materials exposure influences the performance of materials supply systems and assembly systems. The supply of components is crucial for assembly, for in serving the requirements from assembly. Still, the materials supply system has to remain efficient. In this way, materials exposure impacts the performance of a production system as a whole.The thesis is a based on five studies, all of which depart from theoretical frame- works developed from literature and empirically applied within the Swedish automotive industry. Four case studies and one experiment were conducted to answer three research questions, and the results are published in five papers.The results of the thesis provide several theoretical and practical contributions. Both the position of the exposure and the size of the packaging for a component impact the performance of the assembly workstation performance in terms of space required, non-value-adding work, and ergonomics. Materials exposure impacts manual picking time at assembly lines, for which packaging is the most influential factor, followed by angle of exposure and height of the exposed com- ponent. Materials exposure further impacts the configuration of the in-plant ma- terials supply system by requiring additional activities in the in-plant materials supply system, which impacts its performance. Concerning the impact of choice of packaging used in materials exposure, a model to evaluate the impact a pack- aging has on the performance of the materials supply system was developed. The Materials Flow Mapping methodology is another contribution that describes the activities in materials supply systems, as well as categorises the activities in material flows into materials handling, transportation, storage, and administra- tive activities.This thesis explains how the materials exposure influences the performance of materials supply systems and assembly systems. It shows how materials expo- sure impacts the assembly system performance and the in-plant materials supply system performance, and finally, how the packaging for materials exposure im- pacts the performance of the materials supply systems and assembly systems. The thesis can further be used as a guide for how materials should be exposed and in the selection of packaging for materials exposure. The most beneficial managerial use would be in the design and operation of assembly systems, mate- rials supply systems, and in particular, materials exposure.
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| 9. |
- Finnsgård, Christian, 1974, et al.
(författare)
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Swedish shippers’ strategies for coping with slow-steaming in deep sea container shipping
- 2018
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Ingår i: Journal of Shipping and Trade. - : Springer Singapore. - 2364-4575. ; 3:8
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Tidskriftsartikel (refereegranskat)abstract
- When container shipping lines experience over-capacity and high fuel costs, they typically respond by decreasing sailing speeds and, consequently, increasing transport time. Most of the literature on this phenomenon, often referred to as slow-steaming, takes the perspective of the shipping lines addressing technical, operational and financial effects, or a society perspective focusing on lower emissions and energy use. Few studies investigate the effects on the demand side of the market for container liner shipping. Hence, the aim of this study is to elaborate on the logistics consequences of slow-steaming, particularly the strategies that Swedish shippers purchasing deep sea container transport services employ to mitigate the effects of slow-steaming. Workshops and semi-structured interviews revealed that shippers felt they had little or no impact on sailing schedules and were more or less subject to container shipping lines’ decisions. The effects of slow-steaming were obviously most severe for firms with complex supply chains, where intermediate products are sent back and forth between production stages on different continents. The shippers developed a set of strategies to cope with the low punctuality of containerised shipping, and these were categorised in the domains of transfer-the-problem, transport, sourcing and distribution, logistics and manufacturing, and product design. All firms applied changes in the transport domain, although the lack of service segmentation limited the effects of the strategy. Most measures were applied by two firms, whereas only one firm changed the product design.
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| 10. |
- Hanson, Robin, 1981, et al.
(författare)
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Impact of unit load size on in-plant materials supply efficiency
- 2014
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Ingår i: International Journal of Production Economics. - : Elsevier BV. - 0925-5273 .- 1873-7579. ; 147:PART A, s. 46-52
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Tidskriftsartikel (refereegranskat)abstract
- The unit loads, e.g.; plastic containers or EUR-pallets, used in an assembly plant can have a significant impact on time efficiency, and hence cost, of both the materials supply and the receiving assembly stations. Smaller unit loads can reduce the time the assemblers spend fetching parts. However, larger unit loads result in fewer moves for a given volume of materials, which implies efficient in-plant materials supply. The current paper explores how the time efficiency of in-plant materials supply is affected by the size of unit loads. Based on the case study, it is clear that the efficiency of the in-plant materials supply is not proportional to the size of the unit loads. There are fundamental differences between how large pallets, compared to smaller unit loads, are delivered, meaning that the increased delivery frequency required for smaller unit loads does not necessarily result in an increased man-hour consumption.
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