| 1. |
- Franke, Axel, et al.
(författare)
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Application of advanced laser diagnostics for the investigation of the ionization sensor signal in a combustion bomb
- 2005
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Ingår i: Applied Physics B. - : Springer Science and Business Media LLC. - 0946-2171 .- 1432-0649. ; 81:8, s. 1135-1142
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Tidskriftsartikel (refereegranskat)abstract
- The ionization sensor is an electrical probe for diagnostics in internal combustion engines. Laser-induced fluorescence (LIF) imaging of fuel, hydroxyl (OH), and nitric oxide (NO) distributions has been employed to extend our knowledge about the governing processes leading to its signal. By monitoring the flame propagation in quiescent and turbulent mixtures, the cycle-to-cycle variations in the early sensor signal was attributed to the stochastic contact between flame front and electrodes. An analysis of the relationship between gas temperature and sensor current in the post-flame gas suggests a dominant role of alkali traces in the ionization process at the conditions under study. Significant cooling of the burned gas in the vicinity of the electrodes was observed in quiescent mixtures. Imaging of the post-flame gas in turbulent combustion revealed moving structures with varying NO and OH concentrations, which were identified as sources of variation in the sensor current.
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| 2. |
- Hardalupas, Y, et al.
(författare)
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Chemiluminescence sensor for local equivalence ratio of reacting mixtures of fuel and air (FLAMESEEK)
- 2004
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Ingår i: Applied Thermal Engineering. - : Elsevier BV. - 1359-4311. ; 24:11-12, s. 1619-1632
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes a Cassegrain optics-based chemiluminescence sensor (CS) for measurements in gas turbine combustors. The chemiluminescence sensor measures the equivalence ratio of reacting fuel and air mixtures, and can identify the flame location, in partially premixed flames. It has the potential for monitoring the degree of premixedness of reacting fuel and air in industrial gas turbine combustors, where operation with lean premixed mixtures is important for reduction of NO, emissions. The spatial resolution of the sensor is evaluated by comparing OH* chemiluminescence measurement from the CS with laser induced OH fluorescence, in the cone-shaped premixed flame of a Bunsen burner. The ability of the sensor to measure in a modified micro-gas turbine environment burning a methane/air, as well as, a methane/ water/air flame (humidified flame) is also demonstrated.
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| 3. |
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| 4. |
- Hrastinski, Stefan, 1980-, et al.
(författare)
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Critical Imaginaries and Reflections on Artificial Intelligence and Robots in Postdigital K-12 Education
- 2019
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Ingår i: Postdigital Science and Education. - : Springer Science and Business Media LLC. - 2524-485X .- 2524-4868 .- 2662-5326. ; 1:2, s. 427-445
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Tidskriftsartikel (refereegranskat)abstract
- It is commonly suggested that emerging technologies will revolutionize education. In this paper, two such emerging technologies, artificial intelligence (AI) and educational robots (ER), are in focus. The aim of the paper is to explore how teachers, researchers and pedagogical developers critically imagine and reflect upon how AI and robots could be used in education. The empirical data were collected from discussion groups that were part of a symposium. For both AI and ERs, the need for more knowledge about these technologies, how they could preferably be used, and how the emergence of these technologies might affect the role of the teacher and the relationship between teachers and students, were outlined. Many participants saw more potential to use AI for individualization as compared with ERs. However, there were also more concerns, such as ethical issues and economic interests, when discussing AI. While the researchers/developers to a greater extent imagined ideal future technology-rich educational practices, the practitioners were more focused on imaginaries grounded in current practice.
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| 5. |
- Jaldemark, Jimmy, 1970-, et al.
(författare)
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Att förstå hur man deltar via redskap i en lärgemenskap
- 2005
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Ingår i: Att förstå lärgemenskaper och mötesplatser på nätet. - Lund : Studentlitteratur. - 9144043708 ; , s. 109-147
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Bokkapitel (refereegranskat)abstract
- Syftet med detta kapitel är att fördjupa förståelsen av ett deltagande via redskap i utbildningsrelaterade nätbaserade lärgemenskaper. För att kunna sammanfläta redskap med deltagande, och samtidigt lyfta fram hur innebörden av deltagandet kan tillskrivas ett teoretiskt perspektiv, problematiserar vi behavioristisk, kognitiv och sociokulturell teoribildning. De nämnda perspektiven utgör en tolkningsram för en generell analys och diskussion av användningen av redskap vid deltagande i utbildningsrelaterade nätbaserade lärgemenskaper. I kapitlet illustreras deltagandet via redskapen med hjälp av chatt, e-post och videokonferens. En diskussion förs kring konsekvenserna av att deltaga i en utbildningsplattform där flera redskap ingår. Skillnader mellan perspektiven tydliggörs för deltagandet.
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| 6. |
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| 7. |
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| 8. |
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| 9. |
- Jaldemark, Jimmy, 1970-, et al.
(författare)
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Learning through others as learning for myself
- 2004
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Ingår i: Paper presented at The Challange of integrating ICT in teacher education. The need for dialogue, change and innovation. A scandinavian/Asian Pacific conference, June 2-4 2004. - Jönköping : Högskolan i Jönköping.
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Konferensbidrag (refereegranskat)abstract
- This paper is about ICT and participation. Our aim is to initiate a discussion about student participation in a web-based learning environment. The paper contains some early results of a philosophical hermeneutical study of a distance-based teacher education in which ICT is used for sharing materials and teaching. Data was collected by interviewing 19 students, who had been using ICT in their teacher education for more than two years. As a framework for understanding, interpretations about student participation were made based on an explicit description of three different perspectives of learning � social constructivist, social constructionist, and sociocultural - and the divergent assumptions these perspectives could be claimed to hold. Preliminary findings indicate that students participate in distance-based teacher education in such a way that their participation is not part of a social, but rather, an individual process of learning. The findings suggest that there is a need to be more explicit about expectations inherent in the use of ICT as a learning environment, and that the current design of such environments for collaboration and learning are challenging.
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| 10. |
- Jaldemark, Jimmy, et al.
(författare)
-
Learning with others as learning by myself
- 2005
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Ingår i: The Challenge of Integrating ICT in Teacher Education. The Need for Dialogue, Change and Innovation.
-
Konferensbidrag (refereegranskat)
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| 11. |
- Jaldemark, Jimmy, 1970-, et al.
(författare)
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Sharing the distance or a distance shared : Social and individual aspects of participation in ICT-supported distance-based teacher education
- 2005
-
Ingår i: ICT in teacher education. - Jönköping : Jönköping University Press. - 9197495344 ; , s. 142-160
-
Bokkapitel (refereegranskat)abstract
- This chapter is about ICT and participation. Our aim is to initiate a discussion about student participation in a web-based learning environment. The chapter contains some results of a philosophical hermeneutical study of a distance-based teacher education in which ICT is used for sharing materials and teaching. Data was collected by interviewing 19 students, who had been using ICT in their teacher education for more than two years. As a framework for understanding, interpretations about student participation were made based on an explicit description of three different perspectives of learning � social constructivist, social constructionist, and sociocultural - and the divergent assumptions these perspectives could be claimed to hold. The findings indicate that students participate in distance-based teacher education in such a way that their participation is not part of a social, but rather, an individual process of learning. The findings also suggest that there is a need to be more explicit about expectations inherent in the use of ICT as a learning environment, and that the current design of such environments for collaboration and learning are challenging.
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| 12. |
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| 13. |
- Kluge, NE Jimmy, et al.
(författare)
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Compression moulding of sheet moulding compound : Modelling with computational fluid dynamics and validation
- 2015
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Ingår i: Journal of reinforced plastics and composites (Print). - : SAGE Publications. - 0731-6844 .- 1530-7964. ; 34:6, s. 479-492
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Tidskriftsartikel (refereegranskat)abstract
- Compression moulding experiments of sheet moulding compound, visual observations of a vacuum test with prepregs and numerical models with two main approaches for computational fluid dynamics simulations of the mould filling phase are presen ed. One assumes that there are layers near the mould surfaces with much less viscosity and the other only use one viscosity model. The numerical experiments showed that the pressure could be accurately predicted with both approaches. The property ne essary to predict correct pressure with altered mould closing velocities was that the bulk material had to obey shear-thinni g effects. Preheating effects before compression were neglected, but altering the heating time until the prepreg was assumed to start flow had a significant effect. The experiments confirmed that the pressure is predominantly affected by the mould c osing velocity. Regardless of the considered process settings, a first pressure top always appeared approximately at the logarithmic strain 0.25. A second top was associated with a slowdown of the press. The location of this was affected by the velocity and the vacuum, the latter indicating that vacuum assistance prevents a build-up of back pressure. Furthermore, heated prepreg above a critical temperature is observed to swell immediately as vacuum assistance is applied.
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| 14. |
- Lindbergh, Lars, et al.
(författare)
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Project Ålidhem : a case study of a sustainable Swedish municipal public housing installation
- 2017
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Ingår i: Energy Procedia. - Amsterdam : Elsevier. - 1876-6102. ; 121, s. 11-17
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Tidskriftsartikel (refereegranskat)abstract
- A refurbishment project conducted within a municipal public housing complex is described and discussed through Project Ålidhem in northern Sweden. The overall energy efficiency goal within the project was a 40-50% reduction in the supplied energy for domestic hot water, building electricity and space heating. In the pilot study, a 43% improvement was observed. This paper focuses on the performance of four buildings constructed under a Delegation for Sustainable Cities program that specified an energy efficiency goal of 65 kWh/m2. This goal was approached, but not attained. Observations of utilization in four free-standing buildings were 68.3, 76.8, 87.2 and 87.6 kWh/m2 per year respectively, which are described and discussed herein.
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| 15. |
- Lindbergh, Lars, et al.
(författare)
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Reflections on sustainable Ålidhem : a case study in Swedish municipal public housing refurbishment
- 2018
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Ingår i: Property Management. - : Emerald Group Publishing Limited. - 0263-7472 .- 1758-731X. ; 36:2, s. 203-220
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: This work is initiated under the premise that reliable evaluation methods are necessary to ensure investments in energy conservation, and the purpose of this paper is to contribute to that literature. It describes some pilot changes and their impact in an actual field study oriented toward upgrading municipal public housing (MPH) units.Design/methodology/approach: The research for this paper was connected to an MPH refurbishment project situated in northern Sweden. The overall energy efficiency goal within the project was a 40-50 percent reduction in the supplied energy for central electricity, domestic hot water and space heating. In order to evaluate if these goals were feasible, a measurement system was installed in a pilot building and in a neighboring building used as a reference. The evaluation was conducted by comparing the post-retrofit performance of the pilot building with the performance of the reference building when it was kept in its initial state (a comparison possible because both buildings had initial similarities).Findings: Impacts could be quantified insofar as a reference (control) building in the same environment was sustained for comparison purposes. A 43 percent improvement was observed in energy utilization in the pilot building compared to its reference companion (99.8 vs 174.5 kWh/m2 per year). When the approach described herein was applied to new construction, the present goal of 65 kWh/m2 was approached as measured by Swedish standards.Practical implications: Results should be of interest to academics in the housing field, professionals involved in refurbishment and residents themselves, renting MPH flats.Originality/value: This study is unique in the following ways: first, it really was a field experiment with a control, thus it did not have any exogenous interference in interpreting results. To the best of our knowledge, this is the first study of its kind. The second interesting characteristic was that results were subsequently used in the refurbishment of other buildings in the complex and in the construction of others. The major value of the paper may be associated with its timing. It comes at a time when the Kyoto agreement has raised concerns about sustainability, but also at a time when many buildings are facing a need for refurbishment.
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| 16. |
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| 17. |
- Nicholls, Ian A., et al.
(författare)
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Can we rationally design molecularly imprinted polymers?
- 2001
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Ingår i: Analytica Chimica Acta. ; 435:1, s. 9-18
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Tidskriftsartikel (refereegranskat)abstract
- The nearly exponential growth in the molecular imprinting literature has to a large extent been fuelled by an increasing awareness of the potential of molecular imprinting based technologies. Despite the acceptance of the technique by cognate disciplines and the demonstration of its usefulness in a number of enabling technologies, relatively little is known about the molecular level events underlying the imprinting process and subsequent recognition events. What rules govern imprint formation? Can we use such rules to rationally design molecularly imprinted polymers?
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| 18. |
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| 19. |
- Nogenmyr, Karl-Johan, et al.
(författare)
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Large Eddy Simulation and Experiments of Stratified Lean Premixed Methane/Air Turbulent Flames
- 2007
-
Ingår i: Proceedings of the Combustion Institute. - : Elsevier BV. - 1540-7489. ; 31:1, s. 1467-1475
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents a joint large eddy simulation and laser diagnostic investigation of premixed turbulent low swirl flames. A lean premixed methane/air mixture, of the equivalence ratio 0.60-0.66, is injected from a 50 mm diameter low swirl burner to a low speed co-flowing air at room temperature and pressure. The level-set G-equation is employed to simulate the inner layer flame front. Flamelet chemistry is used to determine the flame properties in the reactive zones. Mixing and heat transfer in the post-flame zone down-stream are modeled using transport equations. In addition to large eddy simulation, simultaneous 2-D laser induced fluorescence of OH and 2-D particle image velocimetry are used to characterize the basic flame structure. Laser Doppler velocimetry is employed to further analyze the flow velocity along the central axis above the burner, and 2-D filtered Rayleigh scattering is used to measure the temperature field in the lower part of the flame. A bowl-shaped, highly wrinkled turbulent flame is stabilized at a position about one-half diameter above the burner. The flame consists of two distinct parts; around the burner axis, a premixed flame with uniform mixture fraction is stabilized in the low speed flow region induced by the inflow swirl; off the axis of the burner, a stratified lean premixed flame is found in the shear layer of the flow field. Flame holes (local extinction) owing to overly lean mixtures are observed in the off-axis lean stratified part of the flame. A unified level-set G-equation is developed to model the flame holes. The basic flow and flame structure from the model simulations are compared to the laser diagnostic measurements; the height of flame stabilization (lift-off height), the mean temperature profile, and the mean axial and radial velocity components together with rms velocity components are in fairly good agreement with measurement data. © 2006 The Combustion Institute. Published by Elsevier Inc. All rights reserved.
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| 20. |
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| 21. |
- Olofsson, Jimmy, et al.
(författare)
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Development of high temporally and spatially (three-dimensional) resolved formaldehyde measurements in combustion environments
- 2006
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Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 1089-7623 .- 0034-6748. ; 77:1
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Tidskriftsartikel (refereegranskat)abstract
- In the present article a multi-YAG laser cluster and a framing camera have been applied for ultrahigh framing rate and three-dimensional measurements of formaldehyde distribution in flames and engines. The measurement technique utilizes a laser/detection system which has been adopted for the generation of eight laser pulses at 355 nm. By combining these lasers with a framing camera, short movies showing the formaldehyde distributions in combustion phenomena can be recorded, by means of planar laser-induced fluorescence. The technique is successfully demonstrated in a laboratory flame as well as in an engine. In addition to the temporally resolved experiments also three-dimensional measurements are performed by sweeping the eight generated laser sheets across the flame by the use of a fast scanning mirror. By proper triggering of the laser sweep and the detector a three-dimensional image showing the formaldehyde distribution in the flame can be created, which is also demonstrated. (c) 2006 American Institute of Physics.
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| 22. |
- Olofsson, Jimmy, et al.
(författare)
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High-Speed Lif Imaging for Cycle-Resolved Formaldehyde Visualization in Hcci Combustion
- 2005
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Ingår i: SAE, Session: Combustion and Flow Diagnostics. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. ; 114:3, s. 645-652
-
Konferensbidrag (refereegranskat)abstract
- High-speed laser diagnostics was utilized for single-cycle resolved studies of the formaldehyde distribution in the combustion chamber of an HCCI engine. A multi-YAG laser system consisting of four individual Q-switched, flash lamp-pumped Nd:YAG lasers has previously been developed in order to obtain laser pulses at 355 nm suitable for performing LIF measurements of the formaldehyde molecule. Bursts of up to eight pulses with very short time separation can be produced, allowing capturing of LIF image series with high temporal resolution. The system was used together with a high-speed framing camera employing eight intensified CCD modules, with a frame-rate matching the laser pulse repetition rate. The diagnostic system was used to study the combustion in a truck-size HCCI engine, running at 1200 rpm using n-heptane as fuel. By using laser pulses with time separations as short as 70 μs, cycle-resolved image sequences of the formaldehyde distribution were obtained. Thus, with this technique it is possible to follow the formaldehyde formation and consumption processes within a single cycle. The combustion evolution was studied in terms of the rate and spatial structure of formaldehyde formation and consumption for different engine operating conditions, e.g. different stoichiometries. Also, the impact on the rate of heat-release was investigated.
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| 23. |
- Olofsson, Jimmy
(författare)
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Laser Diagnostic Techniques with Ultra-High Repetition Rate for Studies in Combustion Environments
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- When conducting laser based diagnostics in combustion environments it is often desirable to obtain temporally resolved information. This can be due to several factors such as combustion taking place in a turbulent flow field, flame propagation from a spark plug in an initially quiescent combustible mixture, or rapid, multi-point fuel consumption in a homogeneous charge as a result of compression ignition in an engine cycle. A multi-YAG laser cluster and a high-speed framing camera capable of recording sequences of up to eight image frames, and having a framing rate up to the megahertz range were originally set up for these types of studies. Within the framework of this thesis, further developments of this high-speed diagnostic system aiming at extending the wavelength palette and thus the range of detectable species, was carried out. In addition, the system was used for measurements with ultra-high repetition rates for the detection of different flame species in a variety of combustion devices. The high-speed laser system was redesigned for the generation of laser radiation at 355 nm, in addition to the original 532 nm and 266 nm, and a successful feasibility test for high-speed formaldehyde planar laser-induced fluorescence (PLIF) was carried out for the new design. Moreover, a novel multi-dye laser cluster has been set up. By pumping each of the four dye lasers individually using the Nd:YAG lasers in the multi-YAG cluster, tunable laser radiation with an ultra-high repetition rate can be produced, without the drawback of either losses in laser pulse energy or significant deterioration of the beam intensity profile often occurring when a single dye laser is pumped at ultra-high repetition rates. The multi-YAG and multi-dye laser clusters were used for high-speed visualization of the OH radical by means of planar laser-induced fluorescence in a low-swirl methane/air flame for tracking flame front movements over time while simultaneously measuring the flow-velocity field. Simultaneous high-speed OH visualization and imaging of the temperature field was also performed. The work carried out was a first step in the development of a detailed Large Eddy Simulation validation database for turbulent, premixed methane/air flames. High-speed OH PLIF using a single dye laser was employed in several other studies of the reaction zone, including an investigation of the ignition properties of hot jets in explosive environments, a study of combustion processes in a pulse combustor, and an investigation of the governing processes leading to electrical signals in an ion-current sensor. The last of these also included high-speed fuel tracer LIF. An alternative technique for flame studies involving measurement of the chemiluminescence from OH and CH in order to determine the equivalence ratio was investigated in terms of spatial and temporal resolution. The capability of the technique for resolving flame fronts was compared to reference measurements of OH PLIF. The tests showed that the spatial resolution in the depth direction suffered from line-of-sight detection, which significantly reduced the resolution. As the sensor was designed for monitoring spatial and temporal inhomogenities in mixtures within industrial gas turbine combustors, the temporal and spatial scales in such a combustor were evaluated using the high-speed laser diagnostic system for time-resolved visualization of OH. Also, fuel tracer PLIF was performed in order to visualize the fuel distribution in the combustor. The multi-YAG laser cluster was used in several studies of combustion processes in a homogeneous charge compression ignition (HCCI) engine, involving both high-speed fuel tracer PLIF and formaldehyde PLIF, with the aim of studying different types of ignition control. Acetone was used as a fuel tracer in investigating the effects of combustion chamber geometry on combustion. In studies of spark-assisted HCCI operation, the engine was run on a fuel mixture containing n-heptane, which produces formaldehyde early in the cool-flame region. Formaldehyde can thus be used as a fuel marker, eliminating the need of an added fuel tracer in this situation. Furthermore, three-dimensional imaging of formaldehyde in a laboratory flame as well as of Jet-A vapour in a slow non-reacting flow was demonstrated. This was achieved by rapidly scanning the laser sheet across a measurement volume spatially separating the eight laser pulses. A stack of closely spaced PLIF images was acquired by the framing camera, which could be used to re-create the three-dimensional shape of the investigated species by means of interpolation between the sheets.
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| 24. |
- Olsson, Jimmy, et al.
(författare)
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Compression moulding of SMC : coupling between the flow and the local void contents
- 2009
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Ingår i: ICCM 17, Edinburgh. - London : IOM Communications.
-
Konferensbidrag (refereegranskat)abstract
- During compression moulding of sheet moulding compound (SMC), voids are formed that can deteriorate the properties of the final product. Here, experimental work and CFD-simulations have been carried out in order to increase the knowledge of the SMC compression moulding behaviour which highly affects the quality of the final products.
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| 25. |
- Olsson, Jimmy, et al.
(författare)
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Design of experiment study of compression moulding of SMC
- 2009
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Ingår i: Plastics, rubber and composites. - 1465-8011 .- 1743-2898. ; 38
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Konferensbidrag (refereegranskat)abstract
- The effect of vacuum assistance, mould temperature and ram velocity on the void transport and flow behaviour for sheet moulding compound (SMC) have been investigated with a design of experiment approach of the compression moulding phase. The relative amount of voids has been quantified with a high voltage insulation test and the flow behaviour has been quantified with image analysis of samples moulded with coloured SMC. In conclusion, the setting of high vacuum, low ram velocity and low mould temperature creates a homogeneous flow and minimises the amount of voids. © 2009 Institute of Materials, Minerals and Mining.
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| 26. |
- Olsson, Jimmy, et al.
(författare)
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Process study on compression moulding of SMC using factorial design
- 2008
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Ingår i: 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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Konferensbidrag (refereegranskat)abstract
- During compression moulding of sheet moulding compounds, voids are formed that can deteriorate the properties of the final product. A large number of processing and material parameters can however be tuned in order to reduce the amount of voids. A factorial design is here applied to plan an experimental series where, in particular, vacuum assisted mouldings are carried out in a circular shaped mould. One result is that the electrical insulation can be considerably improved by choosing optimal processing conditions. Another is that the size of weld lines can be reduced in the same fashion.
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| 27. |
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| 28. |
- Petersson, Per, et al.
(författare)
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Simultaneous PIV/PH-PLIF, Rayleigh thermometry/OH-PLIF and stereo PIV measurements in a low-swirl-flame
- 2007
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Ingår i: Applied Optics. - 2155-3165. ; 46:19, s. 3928-3936
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Tidskriftsartikel (refereegranskat)abstract
- The diagnostic techniques for simultaneous velocity and relative OH distribution, simultaneous temperature and relative OH distribution, and three component velocity mapping are described. The data extracted from the measurements include statistical moments for inflow fluid dynamics, temperature, conditional velocities, and scalar flux. The work is a first step in the development of a detailed large eddy simulation (LES) validation database for a turbulent, premixed flame. The low-swirl burner used in this investigation has many of the necessary attributes for LES model validation, including a simplified interior geometry; it operates well into the thin reaction zone for turbulent premixed flames, and flame stabilization is based entirely on the flow field and not on hardware or pilot flames.
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| 29. |
- Sadanandan, R, et al.
(författare)
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Detailed investigation of ignition by hot gas jets
- 2007
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Ingår i: Proceedings of the Combustion Institute. - : Elsevier BV. - 1540-7489. ; 31:1, s. 719-726
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Konferensbidrag (refereegranskat)abstract
- Experimental and numerical investigations of the ignition of hydrogen/air mixtures by jets of hot exhaust gases are reported. An experimental realisation of such an ignition process, where a jet of hot exhaust gas impinges through a narrow nozzle into a quiescent hydrogen/air mixture, possibly initiating ignition and combustion, is studied. High-speed laser-induced fluorescence (LIF) image sequences of the hydroxyl radical (OH) and laser Schlieren methods are used to gain information about the spatial and temporal evolution of the ignition process. Recording temporally resolved pressure traces yields information about ambient conditions for the process. Numerical experiments are performed that allow linking these observables to certain characteristic states of the gas mixture. The outcome of numerical modelling and experiments indicates the important influence of the hot jet temperature and speed of mixing between the hot and cold gases on the ignition process. The results show the quenching of the flame inside the nozzle and the subsequent ignition of the mixture by the hot exhaust jet. These detailed examinations of the ignition process improve the knowledge concerning flame transmission out of electrical equipment of the type of protection flameproof enclosure.
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| 30. |
- Seyfried, Hans, et al.
(författare)
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High-Speed PLIF Imaging for Investigation of Turbulence Effects on Heat Release Rates in HCCI Combustion
- 2007
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Ingår i: Session: Homogeneous Charge Compression Ignition (HCCI) (Part 4 of 8) Combustion Modeling / Optical Diagnostics. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International.
-
Konferensbidrag (refereegranskat)abstract
- High-speed laser diagnostics was utilized for single-cycle resolved studies of the fuel distribution in the combustion chamber of a truck-size HCCI engine. A multi-YAG laser system consisting of four individual Nd:YAG lasers was used for planar laser-induced fluorescence (PLIF) imaging of the fuel distribution. The fundamental beam from the lasers at 1064 nm was frequency quadrupled in order to obtain laser pulses at 266 nm suitable for excitation of acetone that was used as fuel tracer. Bursts of up to eight pulses with very short time separation were produced, allowing PLIF images with high temporal resolution to be captured within one single cycle event. The system was used together with a high-speed framing camera employing eight ICCD modules, with a frame-rate matching the laser pulse repetition rate. The combustion evolution was studied in terms of spatial distribution and rate of fuel consumption for different engine hardware configurations as well as operating conditions e.g. different stoichiometries and combustion phasing. Two different piston crown geometry were used for altering the degree of turbulence in the combustion chamber. In addition to the optical investigations, the impact of turbulence effects was also studied by calculating the rate of heat-release and combustion phasing from the pressure trace.
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| 31. |
- Vesterberg, Jimmy, 1976-
(författare)
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A regression approach for assessment of building energy performance
- 2014
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Reliable evaluation methods is needed to ensure that investments in energy conservation measures (ECMs) and the construction of new energy efficient buildings lives up to the promised and expected performance.This thesis presents and evaluates a regression method for estimation of influential building parameters: transmission losses above ground (including air leakage), ground heat loss, and overall heat loss coefficient.The analysis is conducted with separately metered electricity, heating and weather data using linear regression models based on the simplified steady-state power balance for a whole building.The evaluation consists of analyzing the robustness of the extracted parameters, their suitability to be used as input values to building energy simulations (BES) tools. In addition, differences between uncalibrated and calibrated BES models are analyzed when they are used to calculate energy savings. Finally the suitability of using a buildings overall heat loss coefficient as a performance verification tool is studied.The presented regression method exhibits high robustness and good agreement with theory. Knowledge of these parameters also proved beneficial in BES calibration procedures as well as in performance verifications. Thus, the presented method shows promising features for reliable energy performance assessments of buildings.
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| 32. |
- Vesterberg, Jimmy, 1976-, et al.
(författare)
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A single-variate building energy signature approach for periods with substantial solar gain
- 2016
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Ingår i: Energy and Buildings. - : Elsevier BV. - 0378-7788 .- 1872-6178. ; 122, s. 185-191
-
Tidskriftsartikel (refereegranskat)abstract
- The use of regression analysis for the identification of building performance parameters based on measurements is often difficult due to collinearity between the outdoor temperature and the global solar radiation (S). This study proposes a method to overcome this issue. The proposed method is based on using the seasonal symmetry of S to pair data from time-periods equidistant from the winter solstice. In addition, a method to utilize synthetic data to fine-tune the paired-data approach is presented. To evaluate the paired-data approach, two years data from a multifamily building in Umeå was used to estimate the heat loss factor (air-to-air transmission including air leakage). The results were compared with results obtained when S was very low (S ≈ 0). It was found that, the fine-tuned paired-data approach resulted in a modest deviation in the heat loss factor with an average absolute deviation of 4.0%. The small deviation indicates that the paired-data approach can extend the use of single-variate regression models for accurate identification of heat loss factors to situations where the solar gain is substantial. The paired-data approach was also used to calibrate a commercial energy building simulation tool.
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| 33. |
- Vesterberg, Jimmy, 1976-, et al.
(författare)
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Calibration of low-rise multifamily residential simulation models using regressed estimations of transmission losses
- 2016
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Ingår i: Journal of Building Performance Simulation, Taylor & Francis. - : Informa UK Limited. - 1940-1493 .- 1940-1507. ; 9:3, s. 304-315
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Tidskriftsartikel (refereegranskat)abstract
- In this study, we evaluated a proposed calibration approach for whole-building energy simulation models. This approach was based on a regression analysis of measured data collected during a time period when the global solar radiation was the lowest. The proposed approach was compared with a more conventional calibration approach with different degrees of complexity, starting from design stage assumptions, through audits, and lastly by refining the model with detailed measurements and numerical calculations. The evaluation was performed using measured data from two multifamily buildings located in Umeå, Sweden, and the IDA ICE 4.61 simulation software. The best agreement between simulated and measured data was obtained with the proposed calibration approach. The monthly normalized mean bias error and the coefficient of variation was less than 5.0% and 6.0% respectively. For the conventional calibration approach, detailed measurements and time-consuming numerical calculations were required to reach similar results.
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| 34. |
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| 35. |
- Vesterberg, Jimmy, 1976-
(författare)
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Improved building energy simulations and verifications by regression
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- It is common with significant differences between calculated and actual energy use in the building sector. These calculations are often performed with whole building energy simulation (BES) programs. In this process the analyst must make several assumptions about the studied building and its users. These calculations are often verified with measured data through the EUI benchmark indicator which is calculated by normalizing the annual energy use (from the grid) with the floor area. Due to the highly aggregated nature of the EUI indicator it is problematic to use this indicator to deduce erroneous assumptions in the calculations. Consequently, the learning process is often troublesome.Against this background, the main aim of this thesis has been to develop methods that can provide feedback (key building performance parameters) from measured data which can be used to increase simulation accuracy and verify building performance. For the latter, regression models have been widely used in the past for verifying energy use. This thesis has the focus on the use of regression analysis for accurate parameter identification to be used to increase the agreement between BES predictions and actual outcome. For this, a BES calibration method based on input from regressed parameters has been developed which has shown promising features in terms of accurate predictions and user friendliness. The calibration method is based on input from regressed estimations of air-to-air-transmission losses, including air leakage (heat loss factor) and ground heat loss. Since it is known that bias models still can give accurate predictions, these parameters have been evaluated in terms of robustness and agreement with independent calculations. In addition, a method has been developed to suppress the bias introduced in the regression due to solar gain. Finally, the importance of calibrated simulations was investigated.The regressed parameters were found to be robust with yearly variations in the heat loss factor of less than 2%. The regressed estimates of ground heat loss were also in good agreement with independent calculations. The robustness of the heat loss factor based on data from periods of substantial solar gain was also found to be high, with an average absolute deviation of 4.0%. The benefit with calibrated models was mainly found to be increased accuracy in predictions and parameters in absolute terms. With increased access to measured data and the promising results in this thesis it is believed that the presented regression models will have their place in future energy quantification methods for accessing energy performance of buildings.
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| 36. |
- Vesterberg, Jimmy, 1976-, et al.
(författare)
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Robustness of a regression approach, aimed for calibration of whole building energy simulation tools
- 2014
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Ingår i: Energy and Buildings. - : Elsevier. - 0378-7788 .- 1872-6178. ; 81, s. 430-434
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Tidskriftsartikel (refereegranskat)abstract
- An approach, able to easily and effectively integrate field measured data in whole Building Energy Simulation (BES) models is crucial to increase simulation accuracy for existing buildings. In this paper the robustness of a linear regression method for extracting transmission losses above ground (including air leakage) and ground heat loss parameters are analyzed. The regression method is evaluated on two documented and monitored multifamily buildings with mechanical supply and exhaust ventilation systems, with and without heat recovery. The obtained results are found to be robust, with variations less than 2% in the extracted estimates of transmission losses above ground (including air leakage) and with a high goodness of fit (R2>0.96) against measured data from two years. In addition, the estimations of the buildings ground heat loss were in good agreement with calculations in accordance with EN ISO 13370:2007. The high quality output from the used regression method serves as good prerequisites for the method to be used in conjunction with BES models to aid the analyst in a BES calibration process
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| 37. |
- Vesterberg, Jimmy, 1976-, et al.
(författare)
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The influence from input data provided by the user on calculated energy savings
- 2014
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Ingår i: 10th Nordic Symposium on Building Physics, Lund, Sweden,15-19 June, 2014. - 9789188722539 ; , s. 1301-1308
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Konferensbidrag (refereegranskat)abstract
- It is generally accepted that the most correct decisions are made when the used support system provides the most accurate description of the starting point as possible. That is, in this case, a detailed initial description of a building, planned to be refurbished and evaluated with the building energy simulation software IDA ICE (v 4.5).In order to assess this statement, we have used two different models to predict energy savings due to different planned energy conservation measures (ECMs): - A basic model based on inputs from currently available standards and as-built drawings. - A calibrated model based on an analysis of measurements from two months, together with measured air handling unit parameters, hourly electricity usage and indoor temperatures.The relative prediction differences between the models are investigated as well as compared with the actual outcome in a neighboring building where the analyzed ECMs have been implemented. The result indicates that a calibrated model should be used, in order to accurately determine the post-retrofit energy demand. However, if only investigation of ECMs which aims to decrease a buildings transmission loss is of interest, the findings suggest that BES calibration is of minor importance.
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| 38. |
- Wallgard, Elisabet, et al.
(författare)
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Paladin (X99384) is expressed in the vasculature and shifts from endothelial to vascular smooth muscle cells during mouse development
- 2012
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Ingår i: Developmental Dynamics. - : Wiley. - 1058-8388 .- 1097-0177. ; 241:4, s. 770-786
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Tidskriftsartikel (refereegranskat)abstract
- Background: Angiogenesis is implicated in many pathological conditions. The role of the proteins involved remains largely unknown, and few vascular-specific drug targets have been discovered. Previously, in a screen for angiogenesis regulators, we identified Paladin (mouse: X99384, human: KIAA1274), a protein containing predicted S/T/Y phosphatase domains.Results: We present a mouse knockout allele for Paladin with a beta-galactosidase reporter, which in combination with Paladin antibodies demonstrate that Paladin is expressed in the vasculature. During mouse embryogenesis, Paladin is primarily expressed in capillary and venous endothelial cells. In adult mice Paladin is predominantly expressed in arterial pericytes and vascular smooth muscle cells. Paladin also displays vascular-restricted expression in human brain, astrocytomas, and glioblastomas.Conclusions: Paladin, a novel putative phosphatase, displays a dynamic expression pattern in the vasculature. During embryonic stages it is broadly expressed in endothelial cells, while in the adult it is selectively expressed in arterial smooth muscle cells.
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| 39. |
- Weinrotter, Martin, et al.
(författare)
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Optical Diagnostics of Laser-Induced and Spark Plug-Assisted Hcci
- 2005
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Ingår i: SAE, Session: Homogeneous Charge Compression Ignition (HCCI) Combustion (Part 6 & 7). - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. ; 114:3, s. 284-295
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Konferensbidrag (refereegranskat)abstract
- HCCI (Homogeneous Charge Compression Ignition), laser-assisted HCCI and spark plug-assisted HCCI combustion was studied experimentally in a modified single cylinder truck-size Scania D12 engine equipped with a quartz liner and quartz piston crown for optical access. The aim of this study was to find out how and to what extent the spark, generated to influence or even trigger the onset of ignition, influences the auto-ignition process or whether primarily normal compression-induced ignition remains prevailing. The beam of a Q-switched Nd:YAG laser (5 ns pulse duration, 25 mJ pulse energy) was focused into the centre of the cylinder to generate a plasma. For comparison, a conventional spark plug located centrally in the cylinder head was alternatively used to obtain sparks at a comparable location. No clear difference in the heat releases during combustion between the three different cases of ignition start could be seen for the fuel of 80/20 iso-octane/n-heptane used. However, with optical diagnostic methods, namely PLIF (Planar Laser-Induced Fluorescence), Schlieren photography and chemiluminescence imaging, differences in the combustion process could be evaluated.
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| 40. |
- Yu, Rixin, et al.
(författare)
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Effect of Turbulence on HCCI Combustion
- 2007
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Ingår i: Session: Homogeneous Charge Compression Ignition (HCCI) (Part 4 of 8) Combustion Modeling / Optical Diagnostics. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International.
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Konferensbidrag (refereegranskat)abstract
- This paper presents large eddy simulation (LES) and experimental studies of the combustion process of ethanol/air mixture in an experimental optical HCCI engine. The fuel is injected to the intake port manifolds to generate uniform fuel/air mixture in the cylinder. Two different piston shapes, one with a flat disc and one with a square bowl, were employed to generate different in-cylinder turbulence and temperature field prior to auto-ignition. The aim of this study was to scrutinize the effect of in-cylinder turbulence on the temperature field and on the combustion process. The fuel tracer, acetone, is measured using laser induced fluorescence (LIF) to characterize the reaction fronts, and chemiluminescence images were recorded using a high speed camera, with a 0.25 crank angle degree resolution, to further illustrate the combustion process. Pressure in the cylinder is recorded in the experiments. Spatial and temporal resolved LES was used to gain information on the turbulence mixing, heat transfer and combustion process. It was shown that gas temperature in the piston bowl is generally higher than that in the squish, leading to an earlier ignition in the bowl. Compared to the disc engine, the square bowl engine has a higher temperature inhomogeneity owing to the turbulence wall heat transfer. The experimentally observed higher combustion duration and slower pressure rise rate in the square bowl engine as compared to the disc engine can be explained by the higher temperature inhomogeneity in the square bowl engine.
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