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The market for hydropower re-investments in Sweden is approx 2.5 billion SEK/yr the coming decade. Large investments will also be carried out in Swedish tailing dams. This will result in challenging projects and need of experts. A crucial factor for a successful management of these challenges is the supply of engineers and researchers with hydro power and dam skills and knowledge. Swedish Hydro Power Centre (Svenskt vattenkraftcentrum, SVC) is a competence centre for university education and research environments within hydro power and mining dams. SVC comprises of two knowledge areas: Hydraulic Engineering and Hydro Turbines and Generators, respectively. SVC builds high-quality and long term sustainable knowledge at selected universities... Godkänd; 2010; 20110411 (andbra)

Performance of an inlet textured contact is analysed for a temperature dependent lubricant flow. Thermal effects are analysed for different shear rates. Shearing of lubricant and subsequent heating reduce load carrying capacity and frictional losses compared with isothermal conditions. Load carrying capacity of a parallel surface contact can be improved by using texturing at the inlet when thermal effects are considered. It is also shown that for the different convergence ratios considered, the texture enables the sustaining of a load until a certain critical shear rate is reached. This critical shear rate depends on a number of factors such as the convergence ratio and lubricant parameters including the viscosity-temperature coefficient and the dynamic viscosity at reference temperature. Godkänd; 2008; Bibliografisk uppgift: CD-ROM; 20080828 (cervante)

Analysis of a 3D inlet textured slider bearing with a temperature dependent fluid is performed. Numerical simulations are carried out for a laminar and steady flow. Hot and cold lubricant mixing in the groove is modelled and examined for different operating conditions. Thermohydrodynamic performance of the bearing is analysed for different texture lengths. Results show that texture has a stronger and positive influence on load carrying capacity when thermal effects are considered. This beneficial effect is at a maximum for the longest dimples with a length shorter than the pad length. Texture is also beneficial for the load carrying capacity when the sliding speed and inlet flow rate are varied: with an appropriate supply mass flow, load carrying capacity can be increased by 6-7% at low sliding speeds. Godkänd; 2008; Bibliografisk uppgift: 1 CD-ROM; 20080812 (cervante)

An analysis of a lubricated journal bearing is performed with special attention to the influence of textured surfaces which may improve hydrodynamic performance. The bearing is subjected to an external applied load and the force balance is fulfilled with the force of the flow acting on the bearing. The position of the shaft is fixed whereas the bearing, centred at the starting time, moves under the forces until equilibrium is reached. A mesh deformation technique is used with CFD (Computational Fluid Dynamics) in order to perform the simulations. The flow is laminar, isothermal, three-dimensional (3D) and unsteady. Cavitation is taken into account. Results are analysed with smooth and textured surfaces on the bearing. Friction force and eccentricity ratio are compared for different configurations.It is found that shallow grooves under light loading (ε < 0.15) enhance the minimum film thickness while reducing the friction force. Under high loading (ε > 0.5), deep grooves are able to reduce the friction force despite a reduced minimum film thickness. For the second case, the predicted performance is superior to those of a smooth journal bearing with thinner lubricant. Godkänd; 2008; Bibliografisk uppgift: 1 CD-ROM; 20081111 (ysko)

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. Godkänd; 2008; Bibliografisk uppgift: CD-ROM; 20080828 (cervante)

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. Godkänd; 2008; Bibliografisk uppgift: CD-ROM; 20081103 (cervante)