| 1. |
- Nybacka, Mikael, et al.
(author)
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Project: CASTT - Centre for Automotive Systems Technologies and Testing
- 2007
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Other publication (pop. science, debate, etc.)abstract
- Through the Centre for Automotive Systems Technologies and Testing, Luleå University of Technology aims to first of all support automotive winter testing in Northern Sweden. This means to support the local automotive test entrepreneurs and through them their customers: the car manufacturers and their suppliers. To succeed in this task, the center relies on the university's areas of leading research and most importantly on the cooperation between those areas.
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| 2. |
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| 3. |
- Cervantes, Michel, et al.
(author)
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Porjus U9A full-scale hydropower research facility
- 2008
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In: Hydro technology and the evironment for the new century. - Foz do Iguassu.
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Conference paper (peer-reviewed)abstract
- Hydropower still faces complex scientific and technical challenges in order to secure the availability and reliability of the power plants despite more than a century of development. The main challenge is due to new market constrains such as electrical market deregulation and introduction of renewable sources of energy. The major problem is related to the dynamic of the rotor involving several fields: hydraulics, power engineering and mechanics. On the other side, the large and growing hydropower world market represents an opportunity for technically advanced companies offering better efficiency. The difficulty to scale rigorously any technical advance makes full-scale experiment a necessity. World unique facilities are available at Porjus, Sweden, for this purpose. The Porjus Hydropower Centre is composed of a Francis (U8) and a Kaplan (U9) turbine of 10 MW, each exclusively dedicated to education, research and development. In order to further investigate specific issues related to availability and reliability, a project was initiated in 2006. The main objective is to make U9 a full-scale hydropower laboratory able firstly to furnish the necessary data for the development of rotor-dynamic models but also turbines and bearings. To this purposes more than 200 sensors have been installed to measure displacements, forces, pressure, film thickness, strains... The work presents an overview of the newly upgrade facility as well as some of the problems faced during the instrumentation of the machine.
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| 4. |
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| 5. |
- Cervantes, Michel, et al.
(author)
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Group dynamics [hydro power equipment]
- 2005
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In: International Water Power and Dam Construction. - 0306-400X. ; 57:12, s. 40-45
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Journal article (other academic/artistic)abstract
- An interdisciplinary research group was created at the Lulea University of Technology in Sweden to help develop world leading competencies and knowledge for cutting-edge technologies in hydro power generation. Based on the studies of this Swedish research group, this paper provides a description of the power system from a dynamic point of view to obtain an overall picture, and is completed with a detailed description of the bearings and turbines. The state-of-the-art in each field is presented, together with suggestions for further development.
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| 6. |
- Cupillard, Samuel, et al.
(author)
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Pressure buildup mechanism in a textured inlet of a hydrodynamic contact
- 2008
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In: Journal of tribology. - : ASME International. - 0742-4787 .- 1528-8897. ; 130:2, s. 1-10
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Journal article (peer-reviewed)abstract
- A flow analysis is carried out for an inclined slider bearing with the aim of showing the governing mechanism at conditions where an optimum in load carrying capacity is achieved. The effects of surface texture on pressure buildup and load carrying capacity are explained for a textured slider bearing geometry. Numerical simulations are performed for laminar, steady, and isothermal flows. The energy transferred to the fluid from the moving wall is converted into pressure in the initial part of the converging contact and into losses in the second part. The convergence ratio can be increased, in order to get the greatest pressure gradient, until the limiting value where flow recirculation begins to occur. The texture appears to achieve its maximum efficiency when its depth is such that the velocity profile is stretched at its maximum extent without incurring incoming recirculating flow. The wall profile shape controlling the velocity profile can be optimized for many hydrodynamic contacts.
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| 7. |
- Jourak, Amir, et al.
(author)
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CFD analysis of a journal bearing with a microgroove on the shaft
- 2008
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In: Proceedings of the 19th International Symposium on Transport Phenomena (ISTP-19). - : University of Iceland, Faculty of Industrial Engineering, Mechanical Engineering and Computer Science.
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Conference paper (peer-reviewed)abstract
- Journal bearings are used in many applications. An increase of their load carrying capacity and/or decrease of their losses may allow for savings of an enormous amount of energy. One way to enhance the characteristics of journal bearings is to modify the surface texture of the stator. The purpose of the present study is to investigate the influence of a textured rotor on journal bearing characteristics. Computational Fluid Dynamics is used to model the flow between the rotor and the journal. The full Navier-Stokes equations are solved under unsteady conditions with the commercial software ANSYS CFX 11. A two-dimensional geometry is used to model the bearing. In order to make a simulation, a separate rotor and stator are made and are attached to each other using a rotor-stator interface. Firstly, a single mesh for the smooth journal bearing is used to evaluate possible numerical artefacts created by the interface. The results illustrate a difference of 2.8 % in the load carrying capacity. Simulation with a dimpled rotor followed. Comparison between a dimpled rotor and smooth rotor shows no significant increase in load carrying capacity of the journal bearing when thermal effects are not taken into account.
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| 8. |
- Engström, Niclas, et al.
(author)
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Road grip test in Arjeplog
- 2008
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Reports (other academic/artistic)abstract
- The Swedish road administration sees a need to improve the road grip estimation capacity for the Swedish road system. The challenge is to find methods to measure road grip fast and reliable. There where six different system types at the tests in Arjeplog, three continuous, two system measuring road grip through deceleration and one system based on GPS and accelerometers. Two system types used air craft runway tires. The other systems used either studded winter tires or friction winter tires. Test runs where performed and road grip where recorded for three different surface types, old system 2000 ice, polished ice and new system 2000 ice. Weather data was collected during the three days. It is clear that all systems can detect changes in road grip. It is clear that continuous systems hold an information advantage over the sequence oriented systems. For measurements of road grip on winter roads, we recommend that rubber compounds adapted for cold conditions are used, as the resolution of the road grip measurement where better. In extreme condition like on polished ice, studded winter tires increase the road grip significantly.
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| 9. |
- Bäckström, Mikael, 1963-, et al.
(author)
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People and Skis
- 2006
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In: Science-First Hand. - Novosibirsk : INFOLIO Publishing House. - 1810-8520. ; :3, s. 110-125
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Journal article (pop. science, debate, etc.)
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| 10. |
- Dimkovski, Zlate, et al.
(author)
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Characterisation of Worn Cylinder Liner Surfaces by Segmentation of Honing and Wear Scratches
- 2009
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In: Proceedings of the 12th International Conference on Metrology and Properties of Engineering Surfaces. - Rzesow, Poland : Rzeszow University of Technology. - 9788371995453 ; , s. 187-192
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Conference paper (peer-reviewed)abstract
- The presence of the honing scratches/grooves in cylinder liner surfaces is intended and desired as they improve the lubrication and retain the debris reducing the piston assembly/liner friction and consequently improve the fuel economy and longevity of the internal combustion (IC) engines. Axial scratches caused by the abrasive wear between the tribological partners and/or entrained wear particles are undesired since they are correlated with increased oil consumption and noxious emissions of the IC engines. Due to the imperfection of the manufacturing process, the honing grooves, especially the deep ones, are smeared and interrupted by folds. A portion of the folds would eventually detach during the running process and act as abrasive particles increasing the wear in the cylinder. To closely examine the influence of all these features on the liner's function, it emerges a need to objectively quantify the axial wear scratches, plateau honing grooves, deep honing grooves and their interrupts. The existing techniques fail to segment a groove containing interrupts as they usually appear as summits at several locations in the course of the groove. Combining the profile and image analyses, the deep grooves and their interrupts were successfully identified and quantified in earlier works of the authors. In this paper those algorithms are extended, so that the deep honing grooves, plateau honing grooves and axial scratches crossing different depth levels are sequentially segmented in three levels/steps in an immersing way. A number of parameters derived from this method were utilised to compare 3D interference measurements from the top dead centre, middle and bottom region of a liner run in a truck engine test whereas the three regions represent different wear regimes due to the different running conditions. The results show that: (i) the axial scratches are densest in the top dead centre and about the same size as the plateau grooves in all three regions, while in the bottom region there are only few scratches; (ii) the presence of plateau grooves in the top region clearly decreases, (iii) the deep groove interrupt and coverage are lowest in the top region, and (iv) the groove height and distance between grooves spread mostly. © 2010 Elsevier B.V. All rights reserved.
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