| 1. |
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| 2. |
- Mill, O., et al.
(författare)
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Analysis and development of hydro power research : synthesis within Swedish Hydro Power Centre
- 2010
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- 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...
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| 3. |
- Sandberg, Marcus, et al.
(författare)
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A modelling methodology for assessing use of datacenter waste heat in greenhouses
- 2017
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Konferensbidrag (refereegranskat)abstract
- In Sweden, the number of datacenters establishments are steadily increasing thanks to green, stable and affordable electricity, free air cooling, advantageous energy taxes and well-developed Internet fiber infrastructures. Even though datacenters use a lot of energy, the waste heat that they create is seldom reused. A possible cause is that this waste heat is often low grade and airborne: it is therefore hard to directly inject it into a district heating system without upgrades, which require additional energy and equipment that generate extra costs. One option for reusing this heat without needs for upgrades is to employ it for heating up greenhouses. But assessing the feasibility of this approach by building physical prototypes can be costly, therefore using computer models to simulate real world conditions is an opportunity. However, there is a lack of computer modelling methodologies that can assess the possibility of using waste heat from datacenters in greenhouses in cold climates.The objective of this paper is therefore to propose such a methodology and discuss its benefits and drawbacks in comparison with other research studies. This methodology combines computational fluid dynamics, process modelling and control engineering principles into a computer model that constitutes a decision support system to study different waste heat and greenhouse or mushroom house scenarios.The paper validates the strategy through a case study in northern Sweden, where we assess the amount of produced waste heat by collecting temperature, relative humidity, and fan speed data for the air discharged from the datacenter.The resulting methodology, composed by conducting measurements and computer models, calculations can then be used for other datacenter operators or greenhouse developers to judge whether it is possible or not to build greenhouses using datacenter waste heat.
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| 4. |
- Kyprianidis, Konstantinos, 1984, et al.
(författare)
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Multidisciplinary Analysis of a Geared Fan Intercooled Core Aero-Engine
- 2014
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Ingår i: Journal of Engineering for Gas Turbines and Power. - : ASME International. - 1528-8919 .- 0742-4795. ; 136:1
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Tidskriftsartikel (refereegranskat)abstract
- The reduction of CO2 emissions is strongly linked with the improvement of engine specific fuel consumption, along with the reduction of engine nacelle drag and weight. One alternative design approach to improving specific fuel consumption is to consider a geared fan combined with an increased overall pressure ratio intercooled core performance cycle. The thermal benefits from intercooling have been well documented in the literature. Nevertheless, there is very little information available in the public domain with respect to design space exploration of such an engine concept when combined with a geared fan. The present work uses a multidisciplinary conceptual design tool to analyze the option of an intercooled core geared fan aero engine for long haul applications with a 2020 entry into service technology level assumption. With minimum mission fuel in mind, the results indicate as optimal values a pressure ratio split exponent of 0.38 and an intercooler mass flow ratio of 1.18 at hot-day top of climb conditions. At ISA midcruise conditions a specific thrust of 86 m/s, a jet velocity ratio of 0.83, an intercooler effectiveness of 56%, and an overall pressure ratio value of 76 are likely to be a good choice. A 70,000 lbf intercooled turbofan engine is large enough to make efficient use of an all-axial compression system, particularly within a geared fan configuration, but intercooling is perhaps more likely to be applied to even larger engines. The proposed optimal jet velocity ratio is actually higher than the value one would expect by using standard analytical expressions, primarily because this design variable affects core efficiency at midcruise due to a combination of several different subtle changes to the core cycle and core component efficiencies at this condition. The analytical expressions do not consider changes in core efficiency and the beneficial effect of intercooling on transfer efficiency, nor do they account for losses in the bypass duct and jet pipe, while a relatively detailed engine performance model, such as the one utilized in this study, does. Mission fuel results from a surrogate model are in good agreement with the results obtained from a rubberized-wing aircraft model for some of the design parameters. This indicates that it is possible to replace an aircraft model with specific fuel consumption and weight penalty exchange rates. Nevertheless, drag count exchange rates have to be utilized to properly assess changes in mission fuel for those design parameters that affect nacelle diameter.
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| 5. |
- Van der Kelen, Christophe, 1986-, et al.
(författare)
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Measurement and Inverse Estimation of the Full Anisotropic Flow Resistivity Tensor of Glass Wool
- 2010
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The air flow resistivity of nine adjacent glass wool samples is measured and estimated using a previously published method. The samples are extracted from a large slab of glass wool material. Identifying the full flow resistivity tensors for nine adjacent cubic glass wool samples allows for an estimation of the spatial distribution of normal and planar flow resistivity throughout the measured material. The average density of the samples tested is 27.8 kg/m3. The estimated flow resistivity tensors are validated by comparison to uni-directional measurements on cylindrical samples, extracted from the cubic glass wool samples tested. Furthermore, the uni-directional measurement method is studied, providing useful insights on the effect of sample thickness on the measured flow resistivity for an anisotropic material.
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| 6. |
- Van der Kelen, Christophe, 1986-, et al.
(författare)
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Measurement and Inverse Estimation of the Full Anisotropic Flow Resistivity Tensor of Melamine Foam
- 2010
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The flow resistivity tensor, which is the inverse of the viscous per- meability tensor, is one of the most important material properties for the acoustic performance of open cell foams used in acoustic treatments. Due to the manufacturing processes, these foams are most often geomet- rically anisotropic on a microscopic scale. For such a materials there is a need for improved characterisation methods, and this paper discusses the estimation of the flow resistivity tensor of Melamine samples using a methodology which is an improvement of a method previously published by Go ̈ransson et al. The validity of the new method is in addition ver- ified for a wider range of anisotropy. Measurements are performed on cubic Melamine samples, and the resulting 3D flow resistivity tensors are presented. The anisotropic flow resistivity tensors are validated by com- parison to measurements performed on uni-directional cylindrical samples extracted from the previously measured cubic samples. The results sug- gest that there is a relation between the direction of highest flow resistivity, and the rise direction of the material.
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| 7. |
- Lafont, T., et al.
(författare)
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Modelling tyre noise in finite element simulations for pass-by noise predictions
- 2019
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Ingår i: Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science. - : SAGE Publications. - 2041-2983 .- 0954-4062. ; 233:18, s. 6398-6408
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Tidskriftsartikel (refereegranskat)abstract
- © IMechE 2019. Fulfilling the current pass-by noise regulation is a challenge for the original equipment manufacturers and their suppliers. And it's not going to improve over time. Any possible ways to reduce the exterior noise can happen to be beneficial. In this context, simulations are natural alternatives to costly and long measurement campaigns to quantify the benefits of acoustic treatments. Nevertheless, modelling procedures to tackle this type of issues are far from being well-established, even though the literature is rich with studies describing the complex processes involved in the tyre–road contact. Very often, when it comes to full-vehicle modelling, tyre sources are replaced by simple sources as monopoles, thus introducing a physical simplification. This paper is concerned with the tyre noise modelling in finite element simulation in the perspective to assess the pass-by noise of a car. For that, the sound radiated by validated velocity maps from a tyre–road noise simulation model at different speeds and for different loads is compared with the noise radiated by monopoles in the close vicinity of the tyres. The aim is to define the limitation related to the use of the monopoles in order to correctly capture the relevant physics in the simulation.
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| 8. |
- Gantasala, Sudhakar, et al.
(författare)
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Numerical Investigation of the Aeroelastic Behavior of a Wind Turbine with Iced Blades
- 2019
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Ingår i: Energies. - : MDPI. - 1996-1073. ; 12:12
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Tidskriftsartikel (refereegranskat)abstract
- Wind turbines installed in cold-climate regions are prone to the risks of ice accumulation which affects their aeroelastic behavior. The studies carried out on this topic so far considered icing in a few sections of the blade, mostly located in the outer part of the blade, and their influence on the loads and power production of the turbine are only analyzed. The knowledge about the influence of icing in different locations of the blade and asymmetrical icing of the blades on loads, power, and vibration behavior of the turbine is still not matured. To improve this knowledge, multiple simulation cases are needed to run with different ice accumulations on the blade considering structural and aerodynamic property changes due to ice. Such simulations can be easily run by automating the ice shape creation on aerofoil sections and two-dimensional (2-D) Computational Fluid Dynamics (CFD) analysis of those sections. The current work proposes such methodology and it is illustrated on the National Renewable Energy Laboratory (NREL) 5 MW baseline wind turbine model. The influence of symmetrical icing in different locations of the blade and asymmetrical icing of the blade assembly is analyzed on the turbine’s dynamic behavior using the aeroelastic computer-aided engineering tool FAST. The outer third of the blade produces about 50% of the turbine’s total power and severe icing in this part of the blade reduces power output and aeroelastic damping of the blade’s flapwise vibration modes. The increase in blade mass due to ice reduces its natural frequencies which can be extracted from the vibration responses of the turbine operating under turbulent wind conditions. Symmetrical icing of the blades reduces loads acting on the turbine components, whereas asymmetrical icing of the blades induces loads and vibrations in the tower, hub, and nacelle assembly at a frequency synchronous to rotational speed of the turbine.
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| 9. |
- 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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| 10. |
- Carlsson, Per, et al.
(författare)
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High-speed imaging of biomass particles heated with a laser
- 2013
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Ingår i: Journal of Analytical and Applied Pyrolysis. - : Elsevier BV. - 0165-2370 .- 1873-250X. ; 103, s. 278-286
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Tidskriftsartikel (refereegranskat)abstract
- In this work two types of lignocellulosic biomass particles, European spruce and American hardwood (particle sizes from 100 μm to 500 μm) were pyrolysed with a continuous wave 2 W Nd:YAG laser. Simultaneously a high-speed camera was used to capture the behavior of the biomass particle as it was heated for about 0.1 s. Cover glasses were used as a sample holder which allowed for light microscope studies after the heating. Since the cover glasses are not initially heated by the laser, vapors from the biomass particle are quenched on the glass within about 1 particle diameter from the initial particle. Image processing was used to track the contour of the biomass particle and the enclosed area of the contour was calculated for each frame.The main observations are: There is a significant difference between how much surface energy is needed to pyrolyses the spruce (about 75% more) compared to the hardwood. The oil-like substance which appeared on the glass during the experiment is solid at room temperature and shows different levels of transparency. A fraction of this substance is water soluble. A brownish coat is seen on the unreacted biomass. The biomass showed insignificant swelling as it was heated. The biomass particle appears to melt and boil at the front that is formed between the laser beam and the biomass particle. The part of the particle that is not subjected to the laser beam seems to be unaffected.
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