| 1. |
- Persson, Urban, 1961-
(författare)
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Realise the Potential! : Cost Effective and Energy Efficient District Heating in European Urban Areas
- 2011
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The Member States of EU27 need to accelerate the integration of energy efficient technology solutions to reach the 20% energy efficiency target set for 2020. At current pace, projections indicate that only half of expected primary energy reductions will be reached. To meet the energy demands of growing populations and a vibrant economy, while simultaneously reducing primary energy supplies, the European continent faces a new kind of challenge never previously encountered. The identification and application of feasible, competitive, and comprehensive solutions to this problem are of highest priority if the remaining gap is to be closed in time. How is this multi-dimensional and complex dilemma to be dissolved? In this work, expanded use of district heating technology is conceived as a possible solution to substantially reduce future primary energy demands in Europe. By extended recovery and utilisation of vast volumes of currently disregarded excess heat from energy and industry sector fuel transformation processes, district heating systems and combined generation of heat and power can improve the general efficiency of the European energy balance. To investigate the possible range of this solution, this thesis introduces a set of methodologies, theoretical concepts, and model tools, by which a plausible future excess heat utilisation potential, by means of district heat deliveries to residential and service sectors, is estimated. At current conditions and compared to current levels, this potential correspond to a threefold expansion possibility for directly feasible district heating systems in European urban areas and a fourfold increase of European excess heat utilisation.
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| 2. |
- Franke, Axel, et al.
(författare)
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The effect of in-cylinder gas flow on the interpretation of the ionization sensor signal
- 2003
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Ingår i: SAE Technical Papers. - Warrendale : S A E Inc..
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Konferensbidrag (refereegranskat)abstract
- The location of the peak pressure can serve as a control parameter to adjust ignition timing and optimize engine performance. The ionization sensor, an electrical probe for combustion diagnostics, can provide information about the peak pressure location. However, the reliability of such information is rather poor. In-cylinder gas flow at the electrodes may be one reason for this. We present results from an investigation of the relationship between ionization sensor current and pressure under various gas flow conditions. The gas flow velocity in the vicinity of the electrode gap was measured by LDA. From the results one may infer how the in-cylinder gas flow affects the reliability of the prediction of pressure peak location from the ionization sensor signal. One finding is that high bulk gas flow impairs the precision of the prediction in certain configurations.
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| 3. |
- Rebeggiani, Sabina, 1980-, et al.
(författare)
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Towards In-Line Measurements of Sawn Wood Surfaces
- 2024
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Ingår i: Sustainable Production through Advanced Manufacturing, Intelligent Automation and Work Integrated Learning. - Amsterdam : IOS Press. - 9781643685106 ; , s. 15-26
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Konferensbidrag (refereegranskat)abstract
- Metrology and characterisation of products' functional surfaces are of key importance in smart and sustainable manufacturing. By proper measures of resulting topography and dimension at the micro-cm level, higher process control can be achieved, leading to more efficient production with products closer to defined targets. Commercial surface metrology systems for lab- and in/on-line applications have increased in the last decades, but the wood sector has not yet benefited from this development. A better understanding of sawn wood topography combined with smart online metrology systems is expected to lead to a substantial reduction of waste in sawmill production, both by transforming waste pieces and sideboards into engineered wood products and by optimising the sawing process (e.g. by using thinner saw blades and reduced tolerances). It would also open new design possibilities and challenge the construction sector to replace today’s materials with renewable raw materials. Additionally, sawmills will be less dependent on incoming timber dimensions. This study is the first step towards a better understanding of sawn wood topography and how relevant surface features can be detected and analysed to enable the next generation of functional wood surfaces for various applications. By identifying the measuring instrument’s capability to capture surface topographical features of sawn wood, this paper discusses the requirements for efficient measurement techniques. It opens for future implementation of machine learning algorithms to in-line monitor and control the machining process. All tested metrology techniques showed promising results. To capture machining marks, the instrumentation needs to have lateral resolutions on the um level and a measurement area covering some cm; thus, the laser scanning system seemed to be a good compromise. © 2024 The Authors.
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| 4. |
- Anderberg, Cecilia, et al.
(författare)
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Cylinder Liners and Consequences of Improved Honing
- 2006
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Ingår i: Proceedings of Nordtrib conference 2006, Helsingor, Danemark. ; , s. 13-
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Konferensbidrag (refereegranskat)abstract
- The demands on decreased environmental impact from vehicles are resulting in a strong push for decreased engine oil and fuel consumption. Engine oil and fuel consumption are to a great extent controlled by the topography of the cylinder liner surface.Recent engine tests have shown a promising reduction in oil consumption when using cylinder liners with a smoother finish than the current plateau honing.One approach to produce smoother liner surfaces is to replace SiC ceramic honing stones with diamond tools. However, event though the diamond honing process results in higher productivity, improved demands of quality control is needed to monitor the degree of cold worked material - “blechmantel” (German), and the resulting risk of increased wear and scuffing.A number of petrol and diesel engine cylinder liners have been mapped to be able to verify the quality and consequences, in terms of wear and function, of the honing process. A new mapping method, combining SEM images and quantitative image analysis with traditional 2D profilometry has been developed and tested in this study. The liners where tested in a reciprocating rig of 8 mm stroke and with a frequency of 10 Hz, simulating the top-dead center conditions in a running engine.The tests where carried out in high- and low pressure conditions with smooth respectively rough liner roughnesses against PVD coated piston rings. The developed surface mapping method was employed before and after the test to study effect of running-in wear on the surface, features characterized with the SEM- and the 2D profilometer.The results show that combining SEM- and profilometric methods gives a good picture of the effects of varying the cylinder liner pressure and roughness. The core roughness decrease more for diesel liners than for petrol liners. In average (rough and smooth liners) the diesel core roughness decrease 265% while the petrol liners average on a 60% decrease. Blechmantel- and Irregularities ratio show a high sensitivity to varying conditions and decrease 1180% to 100% for the diesel liners while the parameters increase between 106% to 18% for all the petrol liners. A probable cause is the more severe diesel high pressure run-in conditions are able to effectively “truncate” the plateaux and remove residing plastically deformed un-cut honing residues while the less severe petrol liner conditions not manage to remove the blechmantel and irregularities in an important extent.
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| 5. |
- Dimkovski, Zlate, 1974-, et al.
(författare)
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Evaluation of Durability of SOG-layers on Steel Surfaces by Wear and Scratch Tests
- 2014
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Konferensbidrag (refereegranskat)abstract
- Steel moulds with high precision surfaces are being used in various branches. Process aspects, like tool life and tribological properties, as well as design issues are of great importance. This work summarises experimental studies performed to test durability properties of SOG (spin-on-glass)-layers on steel surfaces. This coating technique is based on a newly developed method for surface preparation of tools which has been demonstrated to be durable for more than 66.000 replications in injection moulding processes without loss of surface fidelity. The procedure allows surface roughness reduction from approximately 200 nm Ra down to some few nm for high gloss applications, as well as easy transfer of large-area functional nanostructures on complex 3D surfaces.Three different types of surfaces were investigated: SOG-layered metal surfaces with three different layer thicknesses, one ingot casted and one electro slag remelted material (with hardness level of 950 and 2500 MPa, respectively). The metal surfaces were ground and polished to mirrorlike finishes.Three circular samples of each type were rubbed against a hard steel ball of 6.35 mm radius on a commercial pin-on-disk tribometer. To resemble the molding process a sliding speed of 2 mm/s and a load of 8 N were chosen. The tests were performed with 5 minutes intervals until the first damage on the surface were observed. In parallel, scratch tests were performed in the same tribometer. The surfaces were measured in-situ by a portable microscope and a stylus, and afterwards by a white light interferometer and scanning electron microscope to evaluate the size of the wear/scratch traces.The surface type with the longest time to damage and/or smallest wear/scratch traces was considered to be the most durable one.
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| 6. |
- Khoshkangini, Reza, 1984-, et al.
(författare)
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A Snapshot-Stacked Ensemble and Optimization Approach for Vehicle Breakdown Prediction
- 2023
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Ingår i: Sensors. - Basel : MDPI. - 1424-8220. ; 23:12
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Tidskriftsartikel (refereegranskat)abstract
- Predicting breakdowns is becoming one of the main goals for vehicle manufacturers so as to better allocate resources, and to reduce costs and safety issues. At the core of the utilization of vehicle sensors is the fact that early detection of anomalies facilitates the prediction of potential breakdown issues, which, if otherwise undetected, could lead to breakdowns and warranty claims. However, the making of such predictions is too complex a challenge to solve using simple predictive models. The strength of heuristic optimization techniques in solving np-hard problems, and the recent success of ensemble approaches to various modeling problems, motivated us to investigate a hybrid optimization- and ensemble-based approach to tackle the complex task. In this study, we propose a snapshot-stacked ensemble deep neural network (SSED) approach to predict vehicle claims (in this study, we refer to a claim as being a breakdown or a fault) by considering vehicle operational life records. The approach includes three main modules: Data pre-processing, Dimensionality Reduction, and Ensemble Learning. The first module is developed to run a set of practices to integrate various sources of data, extract hidden information and segment the data into different time windows. In the second module, the most informative measurements to represent vehicle usage are selected through an adapted heuristic optimization approach. Finally, in the last module, the ensemble machine learning approach utilizes the selected measurements to map the vehicle usage to the breakdowns for the prediction. The proposed approach integrates, and uses, the following two sources of data, collected from thousands of heavy-duty trucks: Logged Vehicle Data (LVD) and Warranty Claim Data (WCD). The experimental results confirm the proposed system's effectiveness in predicting vehicle breakdowns. By adapting the optimization and snapshot-stacked ensemble deep networks, we demonstrate how sensor data, in the form of vehicle usage history, contributes to claim predictions. The experimental evaluation of the system on other application domains also indicated the generality of the proposed approach.
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| 7. |
- Lygnerud, Kristina, 1976-, et al.
(författare)
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Risk assessment of industrial excess heat collaborations – Empirical data from new and ongoing installations
- 2022
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Ingår i: Energy. - London : Elsevier. - 0360-5442 .- 1873-6785. ; 255
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Tidskriftsartikel (refereegranskat)abstract
- Excess heat could meet approximately 25% of the heat demand in the European building sector. However, the recovery of excess heat is low, which has been attributed to financial, technical and organisational barriers. There is limited information on the perceived risk exposure of excess heat recovery at different points in time, before undertaking the investment or after having undertaken the investment, and at locations with existing district heating networks or not (greenfield). This is unfortunate because experience can enable new collaborations. In this paper, we compare the perceived risk exposure of four greenfield and two ongoing industrial excess heat recovery collaborations. In doing so, we confirm previously identified barriers, such as difficulty to agree on the value of excess heat, the risk of a single heat source and lack of regulation. We also find that, with experience, changes to the excess heat-generating processes are increasingly important, whereas, greenfield sites find the lack of ‘know-how’ to be risky. However, the main conclusion from this paper is that the risks of industrial excess heat recovery collaborations appear to be over-emphasised. In fact, risk exposure of industrial activity can be reduced through industrial waste heat recovery as excess heat is characterized by limited price fluctuations and new environmental requirements from customers and authorities can be met proactively. Combining experience with a standardised excess heat recovery policy should significantly reduce the risk exposure of new collaborations. © 2022 Published by Elsevier Ltd.
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| 8. |
- Olofsson, Ulf, 1962-, et al.
(författare)
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A pin-on-disc study of airborne wear particle emissions from studded tyre on concrete road contacts
- 2018
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Ingår i: Wear. - Amsterdam : Elsevier Ltd. - 0043-1648 .- 1873-2577. ; 410-411, s. 165-172
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Tidskriftsartikel (refereegranskat)abstract
- Studded tyres wear surfaces of winter roads, generating inhalable airborne particles. In this study, four concrete road materials and two stud geometries were investigated in terms of wear, road material hardness and airborne particle concentration. The sliding contact between studded tyres and road materials was studied using a pin-on-disc machine in a clean chamber. The results show that the normal load and the stud size have a large influence on the wear and particle emission. It was found that the wear and particle concentration are inversely proportional to the hardness of the aggregate in the road material and proportional to the sliding distance. The particle size distribution has peaks at 0.2 µm, 1 µm and 2 µm.
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| 9. |
- Ottermo, Fredric, et al.
(författare)
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An upper size of vertical axis wind turbines
- 2014
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Ingår i: Wind Energy. - Chichester : Wiley. - 1095-4244 .- 1099-1824. ; 17:10, s. 1623-1629
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Tidskriftsartikel (refereegranskat)abstract
- The scaling behaviour of a straight-bladed vertical axis wind turbine is considered. A scaling scheme is described that, in the presence of a wind shear profile, aims at leaving the material stresses of the scaled construction unchanged. On the basis of a recent 200 kW three-bladed H-rotor design, a structural upper size of the turbine is proposed, this size being the scale at which the gravitational force starts to become important. As gravity has a much worse scaling behaviour than the aerodynamic and centrifugal forces, the construction work will become increasingly more difficult above this scale. The upper size is estimated to be around 30 MW.
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| 10. |
- Werner, Sven, 1952-, et al.
(författare)
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Sparse district-heating in Sweden
- 2008
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Ingår i: Applied Energy. - Amsterdam : Elsevier. - 0306-2619 .- 1872-9118. ; 85:7, s. 555-564
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a review of the sparse district-heating research programme undertaken in Sweden between 2002 and 2006. The goal of the programme was to increase the future competitiveness for district heat in low heat density areas, e.g., suburban single-family houses and small villages. Such areas are unfavourable, since revenues from heat sold are low compared with the investment cost for the local distribution network. In Sweden, district heat has a dominant position in the heat market for residential and service-sector buildings. In order for the business to grow, it is necessary to increase the rate of expansion in the detached-house segment. This is why the programme was initiated. The extent of the programme was set at € 3.6 million with equal financing from the Swedish District-Heating Association and the Swedish Energy-Agency. The research was carried out in three phases: a state of the art survey; a development phase focused on productivity gains where new research on both technology and customer interaction was performed; and finally a demonstration phase where new methods were tested in full-scale field operation. The programme has shown that the Swedish district-heating industry needs to adjust in order to reach a higher profitability for sparse district-heating investments. Tradition from large-scale high-density district heating is hard to scale to fit sparse district-heating systems. For example, the construction becomes very labour intensive and the industry is weak when it comes to market-oriented business logic, sales and private customer interaction. Innovation seems to be a way forward and active management of innovations is a way to create increased value of the investments. Other keys to improving the profitability of sparse district-heating investments are more efficient working routines (resulting in higher productivity) and revised ways of customer communications. These seem more important than increasing efficiency in district-heating technology. © 2007.
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