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3. |
- Etikyala, Sreelekha, 1991
(författare)
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Particulate Formation in GDI Engines
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The need to comply with stringent emission regulations while improving fuel economy and reducing criteria pollutant emissions from transportation presents a major challenge in the design of gasoline Direct Injection (DI) engines because of the adverse effects of ultrafine Particulate Number (PN) emissions on human health and other environmental concerns. With upcoming advances in vehicle electrification, it may be the case that electric vehicles completely replace all current vehicles powered by internal combustion engines ensuring zero emissions. In the meantime, Gasoline Direct Injection (GDI) engines have become the primary mode of transportation using gasoline as they offer better fuel economy while also providing low CO2 emissions. However, GDI engines tend to produce relatively high PN emissions when compared to conventional Port Fuel Injection (PFI) engines, largely because of challenges associated with in-cylinder liquid fuel injection. Cold-starts, transients, and high load operation generate a disproportionate share of PN emissions from GDI engines over a certification cycle. The mechanisms of PN formation during these stages must therefore be understood to identify solutions that reduce overall PN emissions in order to comply with increasingly strict emissions standards. This work presents experimental studies on particulate emissions from a naturally aspirated single cylinder metal gasoline engine run in a homogeneous configuration. The engine was adapted to enable operation in both DI and PFI modes. In PFI mode, injection was performed through a custom inlet manifold about 50 cm from the cylinder head to maximize the homogeneity of the fuel-air mixture. The metal head was eventually modified by incorporating an endoscope that made it possible to visualize the combustion process inside the cylinder. The experimental campaigns were structured to systematically isolate and clarify PN formation mechanisms. Tests were initially performed in steady state mode to obtain preliminary insights and to screen operating conditions before conducting transient tests. Particulate emissions were measured and correlated with the images obtained through endoscope visualization where possible. Key objectives of these studies were to find ways of reducing PN formation by increasing combustion stability. It was found that by avoiding conditions that cause wall wetting with liquid fuel, PN emissions can be substantially reduced during both steady state operation and transients. Warming the coolant and injecting fuel at later timings reduced PN emissions during warmup and cold transient conditions. Additionally, experiments using fuel blends with different oxygenate contents showed that the chemical composition of the fuel strongly influences particulate formation under steady state and transient conditions, and that this effect is load-dependent. Overall, the results obtained in this work indicate that wall wetting is the dominant cause of particulate formation inside the cylinder and that fuel-wall interactions involving the piston, cylinder walls, and valves during fuel injection account for a significant proportion of PN emissions in the engine raw exhaust.
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4. |
- 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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5. |
- Li, Xiaojian, 1991, et al.
(författare)
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Installation effects on engine design
- 2020
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Increasing the engine bypass ratio is one way to improve propulsive efficiency. However, an increase in the bypass ratio (BPR) has usually been associated with an increase in the fan diameter. Consequently, there can be a notable increase in the impact of the engine installation on the overall aircraft performance. In order to achieve a better balance between those factors, it requires novel nacelle and engine design concepts. This report mainly reviews installation effects on engine design. Firstly, the installation effects assessment methods are introduced. Then, the installation effects on engine cycle design, intake design and exhaust design are sequentially reviewed.
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6. |
- Bergdahl, Lars, 1943, et al.
(författare)
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Time simulation of the motion of a tension leg platform
- 1988
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Ingår i: BOSS'88 Proceedings of the international conference on behaviour of offshore structures. - 8251908558 ; 2, s. 875-890
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Konferensbidrag (refereegranskat)abstract
- The time-domain motion of a Tension Leg Platform is studied. The used method is based on a convolution technique in which the hydrodynamic reaction force from the frequency-domain solution is Fourier transformed to the time domain. Such a method allows one to consider arbitrary time varying external forces as for example non-linear reaction forces from tendons as well as transient loads.In the developed model time series of first-order wave forces and second-orde slowly varying wave forces are calculated for irregular plane and short-crested waves. Exciting forces due to wind and current are calculated using drag coefficients from model tests. The equations of motion in the time domain are solved for a tension-leg platform performing rigid body motion and results in time series of the motions as well as of the tension in the tendons.Numerical simulations have been carried out and the results are discussed. A comparison is made between calculations and model tests for a tension-leg platform in irregular long-crested waves.
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7. |
- Edman, Jonas, 1973
(författare)
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Modeling Diesel spray combustion using a Detailed Chemistry Approach
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The rapid development of computer hardware during the past decade has contributed substantially to advances in almost all branches of science. Computer modeling is being applied to increasingly small physical scales and increasingly large domains, facilitating the generation of advanced phenomenological models and models based on first principles. These developments have been especially valuable in fields where highly complex micro-scale events are observed or modeled, such as combustion studies, allowing (for instance) the incorporation of complex chemical combustion kinetics into engine spray combustion models. The crude models and global curve fits that were previously used to represent combustion phenomena have now been largely replaced by models based on "first principles". These modeling developments have coincided fortuitously with a shift in the focus of combustion concepts, from mixing-oriented combustion modes like Diesel and stratified charge Otto combustion to the kinetically controlled combustion modes usually referred to as Homogeneous Charge Compression Ignition (HCCI). The driving forces behind the development of the HCCI concept are environmental considerations, manifested in the form of emission legislation. Theoretically, HCCI combustion (characterized by fuel lean mixtures and low peak temperatures) has the potential to reduce soot and NOx emissions to current emission legislation levels even without after-treatment systems. In practical production engine applications, due to current drawbacks such as poor high load capability, the capacity to switch to conventional mode at high load operation is required. For the above reasons, computer modeling that is capable of describing both old and new combustion modes is required. In the work underlying this thesis, CFD modeling was applied to the passenger car Dl Diesel engine operated in both HCCI and conventional Diesel combustion modes. The aim was to couple chemical combustion kinetics and turbulent mixing in order to capture relevant phenomena related to ignition and emission formation for both modes. The resulting, coupled model is referred to as the Partially Stirred Reactor model (PaSR), and is the main component in the Detailed Chemistry Approach currently utilized in combustion modeling at Chalmers University of Technology (CTH). Other essential components of the Detailed Chemistry Approach are the Reference Species Technique (used to determine the relevant chemical timescales) and the Diesel fuel surrogate model (constructed to facilitate realistic treatment of the fuel in both liquid and gaseous states). The gaseous kinetic treatment of the Diesel fuel surrogate model, represented by a blend of aliphatic and aromatic components, consists of a chemical kinetic mechanism considering -75 chemical species participating in -330 elementary or global reactions describing n-heptane and toluene oxidation. Although most of the modeling was done in the CFD code KIVA-3V rel2, the development and validation of the chemical kinetic combustion mechanism was done using the SENKIN code and the CHEMKIN package. The chemical kinetic modeling has provided a kinetic mechanism for Diesel combustion that is capable of reproducing experimental ignition delay characteristics of both n-heptane and toluene oxidation in both low and high pressure regimes. In addition, it reproduces the negative temperature coefficient behavior that is an important feature of commercial Diesel fuels. It has also been able to reproduce cool flame phenomena, which play important roles in HCCI combustion. Results from the constant volume spray modeling have shown that the spray development, liquid and gas penetration and ignition characteristics observed in high pressure Diesel spray experiments are properly reproduced. Furthermore, major combustion variables such as ignition timing, heat release and pressure traces generated in engine simulations have satisfactorily reproduced experimental data acquired in tests using a single cylinder engine at Chalmers University of Technology.
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8. |
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INNOTRACK: Concluding technical report
- 2010
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Samlingsverk (redaktörskap) (refereegranskat)abstract
- The track structure, rails, switches and crossings account for more than 50% of maintenance and renewal costs for the rail industry. To improve the competitiveness of rail transportation, the cost-efficiency of these areas needs to be addressed.This the background to INNOTRACK, an integrated research project funded by the European Commission’s 6th research framework pro- gramme. Running from September 2006 to December 2009, INN- OTRACK has developed a multitude of innovative solutions in the areas of track substructure, rails & welds, and switches & crossings. The solutions have been assessed from technical, logistics and life cycle cost point of views.This Concluding Technical Report of INNOTRACK includes an overview of the project. It further details implementable results, and clusters them into ”highlight” areas. In addition, the book acts as a ”key” to the vast amount of information from INNOTRACK: All sections refer to project reports where more information can be found.
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9. |
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10. |
- Stylidis, Kostas, 1978, et al.
(författare)
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Perceived quality framework in product generation engineering: an automotive industry example
- 2019
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Ingår i: Design Science. - : Cambridge University Press (CUP). - 2053-4701 .- 2053-4701. ; 5
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Tidskriftsartikel (refereegranskat)abstract
- Perceived quality refers to customers’ cognitive and emotional responses to a particular design, often also associated with craftsmanship and customer satisfaction. Previous research defined a taxonomy of perceived quality and provided understanding about how engineering design decisions impact customer satisfaction. Furthermore, development of new products is frequently based on carrying over attributes of existing products, either from the same producer or from competitors. Previous research offered a new product development methodology combining variations of subsystems to carry over from existing products. This brief presents how these two lines of research combined to design the central console of the Porsche Panamera automobile and discusses the opportunities and challenges posed in the practical implementation of this research.
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11. |
- Stylidis, Kostas, 1978, et al.
(författare)
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Perceived quality of products: a framework and attributes ranking method
- 2020
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Ingår i: Journal of Engineering Design. - : Informa UK Limited. - 1466-1837 .- 0954-4828. ; 31:1, s. 37-67
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Tidskriftsartikel (refereegranskat)abstract
- Perceived quality is one of the most critical aspects of product development that defines the successful design. This paper presents a new approach to perceived quality assessment by examining its elements, decomposed into a structure with the bottom-up sensory approach from the level of basic (‘ground’) attributes, covering almost every aspect of quality perception from the engineering viewpoint. The paper proposes a novel method for perceived quality attributes relative importance ranking, resulting in the balanced perceived quality of the final product within the given conditions. The proposed method helps to reach the equilibrium of the product’s quality equation from the perspective of design effort, time, and costs estimations. The authors introduce the Perceived Quality Framework (PQF), which is the taxonomy system for perceived quality attributes and the core of the attributes importance ranking (PQAIR) method. The research outcomes are based on findings of the qualitative exploratory study, including European and North American premium and luxury automotive manufacturers. An empirical structural validity test was performed to assess the usability and rigour of the proposed method. The results indicate that perceived quality evaluation can be significantly improved during all stages of product development.
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12. |
- Stylidis, Konstantinos, 1978, et al.
(författare)
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Towards Overcoming the Boundaries between Manufacturing and Perceived Quality: An Example of Automotive Industry
- 2017
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Ingår i: Procedia CIRP. - : Elsevier BV. - 2212-8271. ; 63, s. 733-738
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Konferensbidrag (refereegranskat)abstract
- Automotive manufacturing enterprises face many challenges today. Remaining as one of the biggest among them is delivering value to the customers through product quality. Moreover, good manufacturing or technical quality does not always result in high perceived quality from a customer perspective. At the same time, perceived quality is a property that has to be incorporated into the product during the whole product lifecycle, from design to production. Throughout the production stage, every manufacturing operation contributes to the building of final product's perceived quality. Thus, there is a need to control manufacturing operations related to this matter. This paper addresses the connection of the perceived quality framework, which defines dimensions of the perceived quality, to a manufacturing model that represents the manufacturing variation and propagation during different assembly operations. The aim of the study is to overcome boundaries between manufacturing and perceived quality. An industrial example, within the automotive premium sector, has been used to draw this connection illustrating the case of welded assemblies.
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13. |
- Binder, Christian, 1988-, et al.
(författare)
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Phosphor Thermometry for In-Cylinder Surface Temperature Measurements in Diesel Engines
- 2019
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Ingår i: Measurement science and technology. - 0957-0233 .- 1361-6501.
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Surface temperature measurements in technically relevant applications can be very hallenging and yet of great importance. Phosphor thermometry is a temperature measurement technique that has previously been employed in technically relevant applications to obtain surface temperature. The technique is based on temperature-dependent changes in a phosphor’s luminescence. To improve the accuracy and precision of temperature measurements with this technique, the present study considers, by way of example, the impact of conditions inside the cylinder of a diesel engine on decay time based phosphor thermometry. After an initial, general assessment of the effect of prevailing measurement conditions, this research investigates errors caused by soot luminosity, extinction, signal trapping and changes of phosphors’ luminescence properties due to exposure to the harsh environment. Furthermore, preferable properties of phosphors which are suitable for in-cylinder temperature measurements are discussed. 16 phosphors are evaluated, including four which – to the authors’ knowledge –have previously not been used in thermometry. Results indicate that errors due to photocathode bleaching, extinction, signal trapping and changes of luminescence properties may cause an erroneous temperature evaluation with temperature errors in the order of serval tens of Kelvin.
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14. |
- Wadekar, Sandip, 1989
(författare)
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Large-eddy simulation on the effects of fuel injection pressure on gasoline spray characteristics
- 2019
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Increasing the injection pressure in gasoline direct injection engines has a substantial potential to reduce emissions while maintaining high efficiency in spark ignition engines. Present gasoline injectors operate at pressures of 20 to 30 MPa. However, the use of higher-pressure fuel injection (40 to 60 MPa or more) could potentially reduce emissions and increase fuel efficiency. To fully exploit the capabilities of high-pressure fuel injection technology, a fundamental understanding of gasoline spray characteristics and behavior at such high injection pressures is vital. Such an understanding could also be used to further model development and facilitate the integration of advanced injection systems into future gasoline engines. This work presents numerical simulation studies on gasoline sprays formed at fuel injection pressures between 40 and 150 MPa. Three nozzle hole shapes (divergent, convergent, and straight) with different configurations (6 or 10 holes) were considered in the simulation to determine how a nozzle geometry affects spray formation. The numerical calculations were performed in a constant volume spray chamber under non-vaporizing conditions to best match the experimental setup. The gas flow was modeled using a large-eddy simulation (LES) approach, while a standard Lagrangian model was utilized to describe the liquid fuel spray. Spray atomization was modeled using the Kelvin Helmholtz –Rayleigh Taylor (KH-RT) atomization model, with the droplet size distribution being assumed to follow a Rosin-Rammler distribution function. Simulation results for the spray liquid penetration length are validated with experimental findings under different fuel injection pressures. Afterwards, an arithmetic mean droplet diameter (D10) and a Sauter mean droplet diameter (D32) as a function of pressure are compared against the measured droplet diameters. Simulated drop size distributions are presented and compared with measured droplet sizes. The results indicate that high fuel injection pressures increase the liquid penetration length and significantly reduce droplet sizes, and that nozzle shape significantly affects spray characteristics and spray formation. In addition, raising the injection pressure from 40 to 150 MPa with a divergent nozzle was predicted to reduce the SMD from 13.4 to 7.5 μm while increasing the probability of observing droplet diameters of 5-10 μm from 40% to 72%. Similar results were obtained for the other nozzle shapes.
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15. |
- Brahma, Arindam, 1987, et al.
(författare)
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A study on the mechanisms of change propagation in mechanical design
- 2021
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Ingår i: Journal of Mechanical Design - Transactions of the ASME. - : ASME International. - 1050-0472. ; 143:12
-
Tidskriftsartikel (refereegranskat)abstract
- Design changes and change propagation have been recognized as ubiquitous in the engineering design process. But why are some design changes propagated while others are absorbed? This paper reports on a study to investigate the specific properties of a mechanical design that influence whether a change is either propagated or absorbed. Student participants in the study were asked to complete a well-defined mechanical design task and then to introduce several design changes. Analysis of the recorded design processes reveals new insight into the mechanisms of change propagation in terms of properties of the design. The insights suggest avenues for future research to make designs more tolerant to potential future change and to develop improved methods to predict change propagation.
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16. |
- Högman, Ulf, 1961, et al.
(författare)
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Requirements on New Technology and the Technology Implementation Process
- 2010
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Ingår i: 8th International NordDesign Conference, NordDesign 2010; Goteborg; Sweden; 25 August 2010 through 27 August 2010. ; 2, s. 289-300
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Konferensbidrag (refereegranskat)abstract
- In literature, many authors have pointed to the importance of technology and technology development for company competitiveness. In this study we aim to study the technology in more detail and attempt to develop an understanding on the requirements and needs on “technology” from the perspective of product development. The research question which we aim to answer in this study is:“What are the requirements on maturity of technology when this technology is about to enter into the product development process?“A qualitative research strategy, based on three study cases involving 17 interviewees, has been chosen. All three cases come from one single company, Volvo Aero Corporation (VAC) in Sweden, in the context of the aero engine industry. The study contributes with a broad mapping of requirements and how they relate to different categories of technologies, showing big differences both regarding content and timing. It is concluded that attention should be payed both to how the organization builds new capabilities and to the capabilities of the technology itself. A surprisingly complicated picture on the requirements relating to the implementation of new technologies has emerged in the study. This contributes to the understanding regarding the difficulties of developing new technology and integrating it into an application.
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17. |
- 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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18. |
- Johansson, Anders, 1985, et al.
(författare)
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Experimental Investigation of Soot in a Spray-Guided Single Cylinder GDI Engine Operating in a Stratified Mode
- 2013
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Ingår i: SAE Technical Papers. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191 .- 2688-3627. ; 6
-
Tidskriftsartikel (refereegranskat)abstract
- Forthcoming reductions in legal limits for emissions of particle matter (PM) from direct injection engines have increased the need for understanding particle distributions in the engines and the factors affecting them. Therefore, in the presented study the influence on PM-emissions of potentially important factors (fuel injection pressure, load, speed and 50% mass fraction burned phasing) on particle mass, number and size distributions were experimentally investigated. The experimental system was a spray-guided, direct injection, single-cylinder research engine operated in stratified charge mode (using gasoline with 10% ethanol as fuel), under five load and speed settings that are appropriate for stratified combustion. The particle distributions obtained from operating the engine in homogeneous combustion and stratified combustion modes were also compared. The particle distributions were measured using a Cambustion DMS500 fast particle analyzer in combination with a Dekati FPS4000 fine particle sampler and a thermodenuder in all tests except the comparison of distributions under stratified and homogeneous combustion conditions. The sampling system was designed to remove as much of the volatile unburned hydrocarbons as possible in order to sample mostly solid particles. Under all of the stratified operating conditions studied, the results indicate that the particle distribution has a characteristic shape with a tail and one large peak. The operating speed significantly affected the size of the largest particles and the quantity of the particles represented by the tail. An almost linear, positive relationship was found between the load and particle number. Increasing the fuel injection pressure reduced particle numbers whereas combustion phasing had no significant observed effects. More particles were generated in stratified combustion mode than in homogeneous mode.
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19. |
- Bergseth, Ellen, 1979-
(författare)
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On tribological design in gear tooth contacts
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The correct tribological design will have a considerable effect on a gear’s service life and efficiency. The purpose of this thesis is to clarify the impact of variation in the gear tooth flank tribological system on the gear contact load capacity – to increase the understanding of how surface topography and lubricant interact.In this thesis the variation in surface topography inherent in the manufacturing method has been shown, by experimental work and computer simulations, to be an important factor for the contact condition in the early life of gears. Surface analysis revealed that the formation and composition of surface boundary layers depends strongly on the chemical composition of the lubricant, but also on pre-existing surface boundary layers. Additionally, surface boundary layers play a major role in frictional behaviour, wear and in allowing the lubricant to react properly with the surfaces.Paper A presents the current ISO 6336 calculation of surface durability. A robust design approach was used to investigate the extent to which the current standard for calculation of surface durability allows for manufacturing variations and the choice of lubricant.Paper B investigates the extent to which a logarithmical profile modification can increase gear contact pressure robustness compared to traditional lead profiles for gears.Paper C compares different gear manufacturing methods and their as-manufactured (fresh unworn) surface topographies, using measured surface topographies as input to a contact simulation program.Paper D examines surface boundary layer formation and the corresponding wear in relation to different anti-wear additives in an environmentally adapted base oil.Papers E and F make use of specimens with surface topographies imitating two gear manufacturing methods (grinding and superfinishing) to be used in a twin-disc and barrel-on-disc machine respectively. The contacts are analysed by friction measurements and simulations combined with methods for surface analysis.
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20. |
- Dahlén, Leon, et al.
(författare)
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Vegetable and synthetic hydraulic fluids to improve the overall efficiency of a hydrostatic transmission
- 2001
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Ingår i: Journal of Synthetic Lubrication. - : Wiley. - 0265-6582 .- 1557-6841. ; 17:4, s. 263-276
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of the investigation reported here was to determine whether or not a hydrostatic transmission can act as an alternative to a conventional one, and, if so, to ascertain to what extent the fluid type contributes to an improvement in the efficiency of the hydrostatic transmission. The results presented in this paper are derived from an experimental field test of the hydrostatic transmission of a belt conveyor. This belt conveyor is one part in an ore-transport line at LKAB mining company in Kiruna. The hydrostatic transmission replaced a conventional transmission consisting of an electric motor, a belt drive and a gearbox. The hydrostatic transmission was operated using three different hydraulic fluids: Shell Tellus TX 68, a conventional mineral oil; Mobil SHC 526, a synthetic fluid; and Binol Hydrap II, a vegetable fluid. All fluids have the same ISO viscosity grade, VG 68. The measurements on the transmission show a 3% overall efficiency improvement when using vegetable and synthetic hydraulic fluids compared with the mineral oil. The current at the start of the transmission was reduced by a factor of 6, compared to that of the conventional transmission. The installed 110 kW electric motor was replaced with one of 55 kW. The test also showed that a closer study of all operating conditions, and a selection of components suited to the size of the load, can improve the overall efficiency of the hydrostatic transmission.
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21. |
- Reddy, Akepati Bhaskar, 1990-
(författare)
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Sustainable Lubrication and Tribotronics enabled by Ionic Materials
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Developments in machine design play a crucial role in the global endeavor towards sustainability. The potential for energy conservation and emission reduction has pushed lubrication research to the forefront, with the lubricant considered to be a vital machine component. As a result of the need for high machine efficiency and longevity, as well as that of greener lubricants, ionic liquids (ILs) are gaining attention for lubrication applications, especially in combination with biodegradable oils. ILs also present a unique opportunity for developing active lubrication, tribotronic systems. To make them an industrially viable option, however, an in-depth understanding of IL lubrication behavior is required. In this doctoral work, investigations of the tribologically relevant ionic boundary films formed by non-halogenated ILs dispersed in a carrier medium (polar solvent or bio-oil) were conducted using a variety of tribological techniques and neutron reflectance. The effect of external actuation by electric potential on the extent, ionic composition, and tribological relevance of the interfacial boundary films was also studied. The results revealed that the ionic architecture and the condition of IL in the oil play an important role in defining the lubricity of the adsorbed boundary films. Clear electroresponsivity was also observed across methods, with the relative concentration of cations and anions in the interfacial film and the lubricating film thickness changing with the electric potential bias. It was established that the anions, playing an anchor role on the surface, are crucial for the formation of robust load-carrying boundary films. A methodology using electrochemical impedance spectroscopy was developed for measuring and characterizing the electric conductivity of complex lubricating greases with ionic and non-ionic additives. According to these measurements, the electrical characteristics of greases depend on the interactions of IL with the grease matrix. Overall, this work contributes towards the development of sustainable lubrication and tribotronic systems using ILs.
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22. |
- Clasén, Kristoffer, 1992, et al.
(författare)
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Investigation of Homogeneous Lean SI Combustion in High Load Operating Conditions
- 2020
-
Ingår i: SAE International Journal of Advances & Current Practices in Mobility. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 2641-9645 .- 2641-9637. ; 2:4, s. 2051-2066
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Tidskriftsartikel (refereegranskat)abstract
- Homogeneous lean combustion (HLC) can be utilized to substantially improve spark ignited (SI) internal combustion engine efficiency. Higher efficiency is vital to enable clean, efficient and affordable propulsion for the next generation light duty vehicles. More research is needed to ensure robustness, fuel efficiency/NOx trade-off and utilization of HLC. Utilization can be improved by expanding the HLC operating window to higher engine torque domains which increases impact on real driving. The authors have earlier assessed boosted HLC operation in a downsized two-litre engine, but it was found that HLC operation could not be achieved above 15 bar NMEP due to instability and knocking combustion. The observation led to the conclusion that there exists a lean load limit. Therefore, further experiments have been conducted in a single cylinder research DISI engine to increase understanding of high load lean operation. HLC is known to suppress end-gas autoignition (knock) by decreasing reactivity and temperatures, but during the experiments knock was observed to be prominent and increasing in severity when engine load was increased despite operating ultra-lean close to lambda 2. Knock is normally mitigated by spark retardation which decreases peak cylinder pressure. However, to maintain stable combustion at lambda = 2 the combustion phasing had to be kept close to TC which resulted in high peak cylinder pressures. Therefore, the combustion event had to be balanced in a window where early combustion promoted knock and late resulted in instability and partial burns. A tumble flap was introduced to increase in-cylinder tumble which reduced knock and improved combustion stability. It could be observed that for most load-points assessed; increased tumble could suppress knock and increase the air-dilution limit which proved beneficial in decreasing the NOx emissions. The highest engine load that could be achieved with highly diluted combustion was 16 bar NMEP.
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23. |
- Pradas Gómez, Alejandro, 1986, et al.
(författare)
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Design automation strategies for aerospace components during conceptual design phases
- 2023
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This paper explores the different design automation strategies used for the design of aerospace components. A literature review of the applicable strategies, together with the strategies used in the DEFAINE project are presented and compared. An opportunity to explore the combination of two strategies is presented (Enhanced Function-Mean and Knowledge Based Engineering), which has the potential to increase the discovery of novel design solutions while being able to assess their structural performance. The preliminary results of the combined strategy are presented, using a DEFAINE use case of a Turbine Rear Structure jet engine component.
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24. |
- Asadi, Saeed, 1987, et al.
(författare)
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Global Sensitivity Analysis of High Speed Shaft Subsystem of a Wind Turbine Drive Train
- 2018
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Ingår i: International Journal of Rotating Machinery. - : Hindawi Limited. - 1542-3034 .- 1023-621X. ; 2018
-
Tidskriftsartikel (refereegranskat)abstract
- The wind turbine dynamics are complex and critical area of study for the wind industry. Quantification of the effective factors to wind turbine performance is valuable for making improvements to both power performance and turbine health. In this paper, the global sensitivity analysis of validated mathematical model for high speed shaft drive train test rig has been developed in order to evaluate the contribution of systems input parameters to the specified objective functions.Thedrive train in this study consists of a 3- phase induction motor, flexible shafts, shafts’ coupling, bearing housing, and disk with an eccentric mass.The governing equations were derived by using the Lagrangian formalism and were solved numerically by Newmark method. The variance based global sensitivity indices are introduced to evaluate the contribution of input structural parameters correlated to the objective functions. The conclusion from the current research provides informative beneficial data in terms of design and optimization of a drive train setup and also can provide better understanding of wind turbine drive train system dynamics with respect to different structural parameters, ultimately designing more efficient drive trains. Finally, the proposed global sensitivity analysis (GSA) methodology demonstrates the detectability of faults in different components.
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25. |
- Berbyuk, Viktor, 1953
(författare)
-
Controlled Multibody Systems with Magnetostrictive Electric Generators
- 2005
-
Ingår i: Proc. The ECCOMAS Thematic Conference Multibody Dynamics 2005 on Advances in Computational Multibody Dynamics, Madrid, June 21-24, 2005, Eds. J.M. Goicolea, J. Cuardrado and J.C. Garcia Orden.. - 8474933536 ; , s. 1-14
-
Konferensbidrag (refereegranskat)abstract
- The proposed paper addresses the problem of modeling and analysis of controlled multibody systems with embedded magnetostrictive transducers. Main emphasis is put on the modeling of the considered mechatronic systems for applications in the field of power harvesting from vibrations, namely vibration-to-electric energy conversion, using novel giant magnetostrictive materials. Mathematical model of the considered mechatronic system has been developed. It comprises the constitutive equations of magnetoelastic behavior of magnetostrictive rod (active element of transducers), standard formulae of electromagnetism for induced voltage and current in the pick-up coil due to variation of magnetic field intensity, and finally the equations of motion of multibody system itself. The last one can be derived using one of the well-known multibody dynamics formalism. Assuming that massinertia parameters of magnetostrictive transducers are negligible small the inverse dynamics based algorithm has been proposed for modeling the controlled motion of multibody systems with embedded transducers. This algorithm is also suitable to evaluate electrical power output of magnetostrictive electric generators for different controlled motions of the system and to optimize the generators design. The inverse dynamics based algorithm was implemented in Matlab/Simulink with user friendly interface. Its efficiency has been confirmed by simulation of performance of different magnetostrictive electric generators under the periodic excitations exerted by the hosting multibody system.
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26. |
- Berbyuk, Viktor, 1953
(författare)
-
Inverse dynamics and Fourier-based approach to solve optimal control problems for multi-link mechanisms
- 1997
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Ingår i: The NATO Advanced Study Institute on Computational Methods in Mechanisms. ; 2, s. 431-440
-
Konferensbidrag (refereegranskat)abstract
- This paper is concerned with the investigation of multi-link mechanism controlled motion between fixed boundary conditions and given constraints on the phase coordinates. The moduli of the controlling moments at the hinges between the links are bounded. A computational method to the mathematical modeling of the optimal control laws which govern multi-link mechanism reaching motion is presented. This method is based on Fourier and spline approximations of the independently variable functions and inverse-dynamics approach. The method proposed makes it possible to satisfy the boundary conditions and some constraints on the phase coordinates automatically and accurately. The efficiency of the proposed method is illustrated by the solution of the energy-optimal control problem of a plane mobile three-link manipulator with a load on the grip.
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27. |
- Berntsson, Andreas, 1978, et al.
(författare)
-
A LIF-study of OH in the Negative Valve Overlap of a Spark-assisted HCCI Combustion Engine
- 2008
-
Ingår i: SAE Technical Papers. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191 .- 2688-3627.
-
Tidskriftsartikel (refereegranskat)abstract
- Future requirements for emission reduction from combustionengines in ground vehicles might be met byusing the HCCI combustion concept. In this study,negative valve overlap (NVO) and low lift, short duration,camshaft profiles, were used to initiate HCCIcombustion by increasing the internal exhaust gas recirculation(EGR) and thus retaining sufficient thermalenergy for chemical reactions to occur when a pilot injectionwas introduced prior to TDC, during the NVO.One of the crucial parameters to control in HCCI combustionis the combustion phasing and one way of doingthis is to vary the relative ratio of fuel injected inpilot and main injections. The combustion phasing isalso influenced by the total amount of fuel supplied tothe engine, the combustion phasing is thus affectedwhen the load is changed. This study focuses on thereactions that occur in the highly diluted environmentduring the NVO when load and pilot to main ratio arechanged.To monitor these reactions, planar laser-induced fluorescence(PLIF) from OH radicals was analyzed ina series of experiments with an optical single-cylinderengine, since these radicals are known to be associatedwith high temperature reactions. A series of experimentswas also performed using a multi-cylinderengine with varied NVO timings, which showed thatthe combustion phasing was influenced by both theratio between the pilot and main injection amountsand the total amount of fuel. Data acquired from correspondingoptical analysis showed the occurrenceof OH radicals (and thus high temperature reactions)during the NVO in all tested operating conditions. Theresults also indicate that the extent of the high temperaturereactions was influenced by both varied parameters,since decreasing the relative amount of the pilotinjection and/or increasing the total amount of fuel ledto larger amounts of OH radicals.
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28. |
- Cheung, Hon Lam, et al.
(författare)
-
A multi-fidelity data-driven model for highly accurate and computationally efficient modeling of short fiber composites
- 2024
-
Ingår i: Composites Science and Technology. - 0266-3538. ; 246
-
Tidskriftsartikel (refereegranskat)abstract
- To develop physics-based models and establish a structure–property relationship for short fiber composites, there are a wide range of micro-structural properties to be considered. To achieve a high accuracy, high-fidelity full-field simulations are required. These simulations are computationally very expensive, and any single analysis could potentially take days to finish. A solution for this issue is to develop surrogate models using artificial neural networks. However, generating a high-fidelity data set requires a huge amount of time. To solve this problem, we used transfer learning technique, a limited amount of high-fidelity full-field simulations, together with a previously developed recurrent neural network model trained on low-fidelity mean-field data. The new RNN model has a very high accuracy (in comparison with full-field simulations) and is remarkably efficient. This model can be used not only for highly efficient modeling purposes, but also for designing new short fiber composites.
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29. |
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30. |
- Okhovat, Reza, 1984
(författare)
-
Dynamic Equations foe Spherical and Cylindrical Shells Using Power Series Method
- 2013
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Shells are commonly used in many branches of engineeringand have therefore beeninvestigated for a number of different types of shells.A shell can be considered as a curved plate having small thickness compared to the other geometrical dimensions as well as to the wavelengths of importance. The most important superiority of shells in comparison to plates is that shell structures can provide high strength and low weight because of their membrane stiffness.Spherical and cylindrical shells appear in manyapplicationsand some dynamic shell theories have thus been developed for these cases.All these theories seem to depend on more or less ad hoc kinematical assumptions and/orother approximations.In this thesis, dynamic equations for an isotropic spherical and an anisotropic cylindrical shell are derived by using a method developed during the last decade for bars, plates, and beams.The main advantage with the method is that it is very systematic and can be developed to any order. It also seems that the resulting structural equations are asymptotically correct to any order.First, dynamic equations are derived for a spherical shell made of a homogeneous, isotropic material.The starting point is a power series expansion of the displacement components in the thickness coordinate relative to the mid-surface of the shell. By using these expansions, the three-dimensional elastodynamic equations yield a set of recursion relations among the expansion functions.Applying the boundary conditions on the surfaces of the spherical shell and eliminating all but the six lowest order expansion functions give the shell equations as a power series in the shell thickness.In principle, the equations can be truncated to any order in the shell thickness, leading to very complicated expressions. Surface differential operators are introduced to decrease the length of the shell equations and tackle this complexity.the displacement field is split into a scalar (radial) part and a vector (tangential) part, and the shell equations are given in terms of the surface operators. After some manipulations, the final four shell equations are obtained in a more compact form which can be presented explicitly.Dynamic equations for an anisotropic cylindrical shell are also derived using the same technique. As a special case a 2D circular ring is considered and the eigenfrequencies are computed and are compared with the exact solution which is obtained by expressing the displacements in terms of Bessel and Neumann functions. Graphite epoxy is considered as an anisotropic material.For all cases, results are compared to exact three-dimensional theory. The computations for eigenfrequencies from the power series approximation are in good correspondence with results from the exact solution.
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31. |
- 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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32. |
- Stylidis, Konstantinos, 1978, et al.
(författare)
-
Perceived quality and the core values in the automotive industry: A corporate view
- 2015
-
Ingår i: DS79: Proceedings of The Third International Conference on Design Creativity, Indian Institute of Science, Bangalore. - 9781904670605 ; , s. 166-173
-
Konferensbidrag (refereegranskat)abstract
- This study explores how professionals from the Volvo Car Group and VolvoGroup Truck Technology understands their company’s core values and transfers these into perceived quality attributes. Traditionally, both of the companies share the same core values: Quality, Safety, Environmental Care, but they transform these values in different ways due to different customer needs. In general, technical quality has been one of the key features in the automotive industry premium segment for many years, but in recent years, it has shifted from being the primary purchasing criterion into being a basic requirement. Today, maintaining a forefront position in the premium segment of the car industry can only be achieved by delivering products that are perceived by the customers as high-quality products. Perceived quality becomes a cutting edge in the competition between car manufacturers. The purpose of this study is to investigate emerging industry trends and make steps towards elicitation,objectification and distribution of issues regarding perceived quality.
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33. |
- Stylidis, Kostas, 1978
(författare)
-
Perceived Quality of Cars. A Novel Framework and Evaluation Methodology.
- 2019
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The supremacy of the automotive manufacturers today is no longer driven by them achieving a superior manufacturing quality but increasingly depends on the customer’s quality perception. Average car consumers see a car’s quality as a fancy mixture of design, aesthetics, their own previous experiences and performance characteristics of the vehicle, unlike a combination of mechanical parts, software pieces, advanced materials, cutting-edge manufacturing processes, with technical knowledge, skills and high production volumes – all ingredients involved in the modern car creation. Perceived quality is one of the most critical aspects for product development that defines successful car design. Speaking of perceived quality, we are dealing with a complex, multifaceted adaptive system; a system where a human is the main agent. “Which product characteristics require the most attention for successful car design?” This is the question engineers and designers need to answer under the pressure of shrinking product development time, available technologies, and financial limitations, not to mention that the answer is expected to be given in numbers to sustain the fierce competition in today’s automotive industry. For this reason, the perceived quality must be understood and controlled during all stages of product development. The research presented in this thesis justifies the engineering viewpoint on perceived quality as an inevitable part of new product development. The core of this research is the Perceived Quality Framework (PQF), a taxonomy structure of perceived quality attributes and the Perceived Quality Attributes Importance Ranking (PQAIR) method, a novel method for perceived quality evaluation that can be applied to a variety of products, including cars. The PQF communicates the attribute-centric engineering viewpoint on quality perception, developed through cumulative studies in the premium and luxury market segment of the automotive industry. The PQAIR method equips engineers with practical tools for perceived quality evaluation. The proposed method helps to reach the equilibrium of the product’s quality equation from the perspective of design effort, time, and costs estimations. Altogether this introduces a new paradigm of perceived quality as the inevitable element integrated into the process of engineering endeavor regarding product attributes that communicates quality to the customer.
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34. |
- Vieira, Tiago, 1984-, et al.
(författare)
-
Evaluation of uncertainty on Shore hardness measurements of tyre treads and implications to tyre/road noise measurements with the Close Proximity method
- 2020
-
Ingår i: Measurement. - : Elsevier. - 0263-2241 .- 1873-412X. ; 162
-
Tidskriftsartikel (refereegranskat)abstract
- Shore hardness measurements subject rubber bodies to standardized indentations. While easily performed, the measurements are subject to uncertainties. Although typical variances for Shore hardness are found in standards, operator and instrument effects are not well described, requiring statistically designed experiments to estimate effects and variance components. This paper focuses on uncertainty in Shore A hardness measurements of tyre tread elements and quantifies operator and instrument effects. Evaluation of uncertainty of Shore A measurements were performed on tyres under controlled conditions using three instruments, two tyres and five operators. Results show that the operator variance component and instrument effects are larger than the reference variance contribution in ISO 11819-3:2017. The interaction between operator and instrument is estimated to be the largest source of variation, while operator and instrument main effects are of similar size as the error component. Recommendations to reduce uncertainties include ignoring instantaneous values and requiring an instrument stand.
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35. |
- Evertsson, Magnus, 1967, et al.
(författare)
-
Control systems for improvement of cone crusher yield and operation
- 2014
-
Ingår i: Proceedings of Comminution '14.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Gyratory and cone crushers are regaining interest and are becoming more frequently used in order to create more energy efficient comminution circuits. A typical example is found in coarse comminution circuits were HPGRs are used as a first milling stage. In this case the preparation of a suitable feed with a well-defined width of the particle size distribution and a controlled top size are of high importance. In turn, this emphasizes the importance of a stable and controlled operation of the preceding crushing stages. Control systems for cone and gyratory crushers were first introduced during the early 60ths. The common opinion is that if these systems are able to compensate for the wear of the crushing liners the production yield can be increased with 20-25%. Over the years these types of systems have been widely used but the theory behind the principles have not been thoroughly scientifically scrutinized and presented. Of special interest is the capability to protect the crushers from long term overloading commonly defined as fatigue.With developments in electronics and plant control the crusher control systems have become more refined over the years. Though, there are sometimes conflicting interests in the control strategies between process requirements and crusher protection. In the paper an overview of the challenges, opportunities and existing control systems for cone and gyratory crushers is presented. A requirement specification for a system that is possible to fully integrate into modern plant control systems is outlined.
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36. |
- Evertsson, Magnus, 1967, et al.
(författare)
-
Monitoring and validation of life time prediction of cone crusher with respect to loading and feeding conditions
- 2016
-
Ingår i: Comminution 16. - 9781510826670 ; 904 (1 Vol)
-
Konferensbidrag (refereegranskat)abstract
- The interest and need for compressive crushing in gyratory, cone and HPGR crushers are increasing since ores become more competent and more difficult to break. Compressive crushing is energy efficient as a consequence of the crushing principle and the imposed stress-state. The stress variations can be described by stress amplitudes and it is a known fact that many different materials, components and machines suffer from cyclic loading which shortens the service lifetime. This phenomena is explained by density variations of the particle beds in the equipment which in turn originates from particle segregation and feeding alignment. The phenomena is often called fatigue and the consequence is premature breakdowns and a relatively shorter lifetime than expected. In this paper, a previously developed theory for lifetime assessment of cone crushers will be used as a foundation for evaluation of full-scale operating cone crushers in minerals processing plants. Lifetime is calculated as a consequence of the load spectrum. The data shows that improper feeding conditions will substantially decrease the lifetime of the crusher equipment leading to excessive operating costs. An adequate control system should be able to recognise the hazardous lifetime decreasing overloads and to warn the operator. There are sometimes conflicting interests in the control strategies between production yield (process requirements) and crusher protection.
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37. |
- Linnéusson, Gary, et al.
(författare)
-
Towards strategic development of maintenance and its effects on production performance by using system dynamics in the automotive industry
- 2018
-
Ingår i: International Journal of Production Economics. - : Elsevier. - 0925-5273 .- 1873-7579. ; 200, s. 151-169
-
Tidskriftsartikel (refereegranskat)abstract
- Managing maintenance within an economical short-termism framework, without considering the consequential long-term cost effect, is very common in industry. This research presents a novel conceptual system dynamics model for the study of the dynamic behaviors of maintenance performance and costs, which aims to illuminate insights for the support of the long-term, strategic development of manufacturing maintenance. By novel, we claim the model promotes a system's view of maintenance costs that include its dynamic consequential costs as the combined result of several interacting maintenance levels throughout the constituent feedback structures. These range from the applied combination of maintenance methodologies to the resulting proactiveness in production, which is based on the rate of continuous improvements arising from the root cause analyses of breakdowns. The purpose of using system dynamics is to support the investigations of the causal relationships between strategic initiatives and performance results, and to enable analyses that take into consideration the time delays between different actions, in order to support the sound formulation of policies to develop maintenance and production performances. The model construction and validation process has been supported by two large maintenance organizations operating in the Swedish automotive industry. Experimental results show that intended changes can have both short and long-term consequences, and that obvious and hidden dynamic behavioral effects, which have not been reported in the literature previously, may be in the system. We believe the model can help to illuminate the holistic value of maintenance on the one hand and support its strategic development as well as the organizational transformation into proactiveness on the other.
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38. |
- Löfstrand, Magnus, et al.
(författare)
-
A model for predicting and monitoring industrial system availability
- 2012
-
Ingår i: International Journal of Product Development. - Bucks, United Kingdom : InderScience Publishers. - 1477-9056 .- 1741-8178. ; 16:2, s. 140-157
-
Tidskriftsartikel (refereegranskat)abstract
- This paper describes the integration of a sensor data stream monitoring system into a proposed functional product model capable of predicting functional availability. Such monitoring systems enable predictive maintenance to be carried out pre-emptive maintenance that is scheduled in response to imminent hardware failure and are in widespread use in industry. The industrial motivation for this research is that agreed upon system availability is a critical element of any business-to-business agreement regarding functional sales. Such a model is important when making strategic choices regarding FPs and can be used to develop a high availability product design through simulation driven development, as well as to provide operational decision support that reflects the current reality to enable optimal availability to be achieved in practice. The proposed model integrates hardware, support system and monitoring system models, and is able to incorporate actual operational data. It has been partly verified based on previous research.
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39. |
- Löfstrand, Magnus, 1974-, et al.
(författare)
-
A model for predicting and monitoring industrial system availability
- 2012
-
Ingår i: International Journal of Product Development. - Bucks, United Kingdom : InderScience Publishers. - 1477-9056 .- 1741-8178. ; 16:2, s. 140-157
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- This paper describes the integration of a sensor data stream monitoring system into a proposed functional product model capable of predicting functional availability. Such monitoring systems enable predictive maintenance to be carried out pre-emptive maintenance that is scheduled in response to imminent hardware failure and are in widespread use in industry. The industrial motivation for this research is that agreed upon system availability is a critical element of any business-to-business agreement regarding functional sales. Such a model is important when making strategic choices regarding FPs and can be used to develop a high availability product design through simulation driven development, as well as to provide operational decision support that reflects the current reality to enable optimal availability to be achieved in practice. The proposed model integrates hardware, support system and monitoring system models, and is able to incorporate actual operational data. It has been partly verified based on previous research.
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40. |
- Reed, Sean, 1982-, et al.
(författare)
-
Quantified economic and environmental values through Functional Productization : A simulation approach
- 2018
-
Ingår i: Environmental impact assessment review. - : Elsevier. - 0195-9255 .- 1873-6432. ; 70, s. 71-80
-
Tidskriftsartikel (refereegranskat)abstract
- Industrial companies rely on hardware and services from external providers to deliver functions that are critical to their operations, increasingly demanding solutions that not only meet technical and availability requirements but are sustainable too. Traditionally, industrial companies choose and purchase hardware and maintenance support to fulfil their functional requirements. An alternative arrangement, known as Functional Product (FP), involves external providers supplying customers with the functionality they require through contracts that specify guaranteed functional availability whilst giving providers freedom to choose and retain ownership of the supplied hardware and services. This paper describes an innovative simulation modelling and optimization approach to quantitatively compare economic and environmental values resulting from transition from traditional to FP arrangements. The approach is demonstrated through the analysis of a scenario involving a hydraulic drive system provider and set of customers in Sweden, with the results exhibiting simultaneous improvement in economic and environmental values at each stage of the transition.
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41. |
- Khodadad, Davood, et al.
(författare)
-
Full-field 3D deformation measurement : Comparison between speckle phase and displacement evaluation
- 2016
-
Ingår i: Applied Optics. - : Optical Society of America. - 1559-128X .- 2155-3165 .- 0003-6935 .- 1539-4522. ; 55:27, s. 7735-7743
-
Tidskriftsartikel (refereegranskat)abstract
- The objective of this paper is to describe a full-field deformation measurement method based on 3D speckle displacements. The deformation is evaluated from the slope of the speckle displacement function that connects the different reconstruction planes. For our experiment, a symmetrical arrangement with four illuminations parallel to the planes (x,z) and (y,z) was used. Four sets of speckle patterns were sequentially recorded by illuminating an object from the four directions, respectively. A single camera is used to record the holograms before and after deformations. Digital speckle photography is then used to calculate relative speckle displacements in each direction between two numerically propagated planes. The 3D speckle displacements vector is calculated as a combination of the speckle displacements from the holograms recorded in each illumination direction. Using the speckle displacements, problems associated with rigid body movements and phase wrapping are avoided. In our experiment, the procedure is shown to give the theoretical accuracy of 0.17 pixels yielding the accuracy of 2 × 10-3 in the measurement of deformation gradients
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42. |
- Simmons, Gregory F, et al.
(författare)
-
Steady state and dynamic characteristics for guide bearings of a hydro-electric unit
- 2014
-
Ingår i: Proceedings of the Institution of mechanical engineers. Part J, journal of engineering tribology. - : SAGE Publications. - 1350-6501 .- 2041-305X. ; 228:8, s. 836-848
-
Tidskriftsartikel (refereegranskat)abstract
- Experiments are conducted using a 10-MW Kaplan hydropower machine which is outfitted with an extensive array of sensors to determine oil film thickness, pad load and oil temperature in all three guide bearings as well as motion of the shaft in relation to both the bearing housings and the concrete foundation. Test results for all journal bearings are compared to a commercial rotor dynamics model and results for the central journal bearing are compared to a multi-physics model to provide insight into the machine's steady state and dynamic characteristics and their variations during normal operation.
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43. |
- Soltani Dehkharqani, Arash, et al.
(författare)
-
Fluid added polar inertia and damping for the torsional vibration of a Kaplan turbine model runner considering multiple perturbations
- 2019
-
Ingår i: IOP Conference Series. - : Institute of Physics (IOP).
-
Konferensbidrag (refereegranskat)abstract
- A water turbine runner is exposed to several perturbation sources with differentfrequencies, phases, and amplitudes both at the design and off-design operations. Rotor-statorinteraction, cavitation, rotating vortex rope, and blade trailing edge vortices are examples of suchperturbations which can disturb the runner. The rotor dynamic coefficients require beingdetermined to perform a reliable dynamic analysis. Fluid added inertia, damping, and stiffnesshave previously been investigated for individual perturbation frequencies for the torsionalvibration of a Kaplan turbine model runner. However, a number of perturbation sources mostlytake place simultaneously and alter the dynamics of the runner. Soltani et al. [1] have evaluatedthe torsional added parameters for a Kaplan turbine runner using numerical simulationsconsidering single perturbation frequency. In the present work, the fluid added parameters areassessed in the presence of multiple perturbation sources. A similar methodology is used. Asingle-degree-of-freedom (SDOF) model for the dynamic model and unsteady ReynoldsaveragedNavier–Stokes approach for the flow simulations are assumed. Perturbations withdifferent frequencies are applied to the rotational speed of the runner to determine the fluid addedparameters for the torsional vibration. A number of previously investigated frequencies arechosen and their combinations are investigated. In addition, two different phase shifts areconsidered between the applied perturbations to study the effect of phase. Two more test caseswith higher perturbation amplitude are also conducted to investigate its influence on the fluidadded inertia and damping. The results are compared with the previous study and the interactionof multiple perturbations on the added parameters is investigated.
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44. |
- Yu, Rixin, et al.
(författare)
-
Effect of Turbulence on HCCI Combustion
- 2007
-
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
- 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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45. |
- Bergman, Martin, 1985
(författare)
-
Affective Surface Engineering for Product Design
- 2016
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Design research, sensation and perception, hard metrology, emotional functions, semantics, surface roughness, product interaction, core values, total appearance… the list of scientific phrases never ends. Yet, what do they mean and how shall we use it when we are communicating with the industry and our end users? Is it possible to link the product experience to process parameters, put a number onto it? When you can measure spoken needs or even better, implied needs, of a product, and relate that data to the production, it is possible do create advanced products with high interaction stimuli. By joining engineering sciences (hard metrology) with design science (soft metrology) correlations between customer’s product experience (emotional functions) and surface properties (technical functions) can be established.The research briefly handles an optimization process where the framework from Kansei Engineering (KE) is used to evaluate the semantics issues primarily regarding materials and functional surfaces of products. The basic idea is that; the stakeholder’s experience shall be observed already at the phase of ideation in the product development process, which then facilitates the project (in regard to the total appearance) later on when a concept reaches the production stage. The results presented in this thesis are carried out through a number of case studies together with the industry. The main result and aim of the research is a developed robust approach that links emotional functions with technical functions, which in the next step facilitates the improvement of the total appearance of a product. Nevertheless, it should be recognized that research is not yet complete. It is an iterative process, which confirms that the loop of the method needs to be complete. The developed method is a toolbox with the fundamental tools and workshops to facilitate the correlation process mentioned above, however the packaging of the final step in the method is not yet complete. The future research outlook will focus on the “independent industry implementation” where the method is used by the industry by guidelines only, thus without researchers support.
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46. |
- Berlin, Cecilia, 1981, et al.
(författare)
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Using the ACD3-ladder to manage multi-phase requirements on end-user products
- 2017
-
Ingår i: Proceedings of the International Conference on Engineering Design, ICED. - 2220-4334 .- 2220-4342. - 9781904670872 ; 4:DS87-4, s. 425-434
-
Konferensbidrag (refereegranskat)abstract
- During the development of any end-user product, a multitude of design decisions need to be made. But if design activities and decisions happen at the wrong time, or not at all, unintentional and sometimes negative design outcomes can be the result. Determining all requirements early in the product development is traditionally recommended, but may force design decisions to be made prematurely onthe basis of incomplete preconditions. Requirements at different degrees of resolution are useful and purposeful at different stages of the development process. To address these requirements management challenges, this paper proposes an approach for incrementally developing requirements in parallel with design, based upon a previously developed framework called ACD³, which draws on a combination of theoretically compatible ideas and concepts from Design Engineering, Human Factors/Ergonomics,Usability and Systems Theory. This approach helps designers identify and handle the possible interdependencies of design variables. The paper also theoretically motivates and demonstrates with an example how the different resolution levels of requirements relate within the framework.
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47. |
- Brahma, Arindam, 1987, et al.
(författare)
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A new model for capturing design information with an aim to aid change propagation assessment and subsequent redesign
- 2018
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Ingår i: DS 92: Proceedings of the DESIGN 2018 15th International Design Conference. - : Faculty of Mechanical Engineering and Naval Architecture, University of Zagreb, Croatia; The Design Society, Glasgow, UK. - 1847-9073.
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Konferensbidrag (refereegranskat)abstract
- A new model is developed to investigate the causes of change propagation and guide the redesign process. The model offers a micro-level perspective on the mechanisms through which changes propagate or are absorbed. Extending the Information Structure Framework (ISF) reported by Ahmad et al. (2013), the model uses a multi-domain approach combined with a reformulated detail design process layer. It is illustrated through a desk-based case study of routine mechanical design. Advantages and limitations are discussed along with possibilities for further work.
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48. |
- Brahma, Arindam, 1987, et al.
(författare)
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Concepts of change propagation analysis in engineering design
- 2023
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Ingår i: Research in Engineering Design - Theory, Applications, and Concurrent Engineering. - : Springer Science and Business Media LLC. - 1435-6066 .- 0934-9839. ; 34:1, s. 117-151
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Tidskriftsartikel (refereegranskat)abstract
- Interest in change propagation analysis for engineering design has increased rapidly since the topic gained prominence in the late 1990s. Although there are now many approaches and models, there is a smaller number of underlying key concepts. This article contributes a literature review and organising framework that summarises and relates these key concepts. Approaches that have been taken to address each key concept are collected and discussed. A visual analysis of the literature is presented to uncover some trends and gaps. The article thereby provides a thematic analysis of state-of-the-art in design change propagation analysis, and highlights opportunities for further work.
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49. |
- Dabhilkar, Mandar, et al.
(författare)
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Supplier selection or collaboration? : Determining factors of performance improvement when outsourcing manufacturing
- 2009
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Ingår i: Journal of Purchasing and Supply Management. - : Elsevier BV. - 1478-4092 .- 1873-6505. ; 15:3, s. 143-153
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Tidskriftsartikel (refereegranskat)abstract
- An empirical study was designed to determine factors of performance improvement when outsourcing manufacturing. Findings from a survey of 136 manufacturing plants in Sweden show that most of them achieve their outsourcing motives, but not without trade-offs. Factors of performance improvements such as economies of scale or operations in low-cost countries can improve one performance dimension, such as product cost, yet negatively impact volume flexibility, speed or product innovation. The results show part characteristics and supplier operating capabilities are more important than supplier relationship strategies when outsourcing manufacturing, meaning that supplier selection trumps supplier collaboration in the make-or-buy decision.
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50. |
- Finnsgård, Christian, 1974
(författare)
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Assembly processes and materials supply systems design
- 2009
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Lean production has over the last decades emerged as the most important paradigm for production, with the assembly processes in focus, including the objective to minimize non-value-adding work. Thus, much attention has been on the work of the assembly operator. However, little focus has been devoted to how the new requirements from lean production have been transformed into materials supply systems supporting the assembly processes. Hence, the purpose of this thesis is to contribute to increased knowledge about the relation between assembly processes and materials supply systems design.A framework is introduced in this thesis, describing how requirements from the assembly processes are transformed by the materials supply system into the actual materials flow. In the results of this thesis, a model structuring requirements in materials supply and assembly processes is proposed, tested, and subsequently different requirements were identified. Materials exposure is introduced as the transition from the materials supply system to the assembly system. Results show that that the materials exposure has a large impact on assembly workstations performance in terms of space needed, non-value-adding work and ergonomics. Further, an experiment showed that the materials exposure factors with the largest impact on picking time were packaging, angle of packaging and height above floor.Major contributions in this thesis are the identification and structuring of requirements in assembly processes and materials supply systems, and explaining how the materials exposure affects the assembly processes. How this knowledge can be applied in the design of new, or redesign of existing, production systems and materials supply processes in particular, is a managerial contribution.
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