| 41. |
- 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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| 42. |
- Stylidis, Konstantinos, 1978, et al.
(författare)
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Perceived quality and the core values in the automotive industry: A corporate view
- 2015
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Ingår i: DS79: Proceedings of The Third International Conference on Design Creativity, Indian Institute of Science, Bangalore. - 9781904670605 ; , s. 166-173
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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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| 43. |
- Stylidis, Kostas, 1978
(författare)
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Perceived Quality of Cars. A Novel Framework and Evaluation Methodology.
- 2019
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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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| 44. |
- Vieira, Tiago, 1984-, et al.
(författare)
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Evaluation of uncertainty on Shore hardness measurements of tyre treads and implications to tyre/road noise measurements with the Close Proximity method
- 2020
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Ingår i: Measurement. - : Elsevier. - 0263-2241 .- 1873-412X. ; 162
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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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| 45. |
- Cervantes, Michel, et al.
(författare)
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Porjus U9A full-scale hydropower research facility
- 2008
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Ingår i: Hydro technology and the evironment for the new century. - Foz do Iguassu.
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Konferensbidrag (refereegranskat)abstract
- Hydropower still faces complex scientific and technical challenges in order to secure the availability and reliability of the power plants despite more than a century of development. The main challenge is due to new market constrains such as electrical market deregulation and introduction of renewable sources of energy. The major problem is related to the dynamic of the rotor involving several fields: hydraulics, power engineering and mechanics. On the other side, the large and growing hydropower world market represents an opportunity for technically advanced companies offering better efficiency. The difficulty to scale rigorously any technical advance makes full-scale experiment a necessity. World unique facilities are available at Porjus, Sweden, for this purpose. The Porjus Hydropower Centre is composed of a Francis (U8) and a Kaplan (U9) turbine of 10 MW, each exclusively dedicated to education, research and development. In order to further investigate specific issues related to availability and reliability, a project was initiated in 2006. The main objective is to make U9 a full-scale hydropower laboratory able firstly to furnish the necessary data for the development of rotor-dynamic models but also turbines and bearings. To this purposes more than 200 sensors have been installed to measure displacements, forces, pressure, film thickness, strains... The work presents an overview of the newly upgrade facility as well as some of the problems faced during the instrumentation of the machine.
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| 46. |
- Korkmaz, Kadir Burak, 1989
(författare)
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Improved Power Predictions of Ships Using Combined CFD/EFD Methods for the Form Factor
- 2020
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Performance prediction of a ship is one of the most important tasks during the design phase. Once the design is finalized, the speed attained at a certain power consumption has to be verified with the most accurate prediction as it is specified at the contract of a new ship order and also required by the legal authorities. Considering the current commercial tendencies and the requirements enforced by legal authorities, towing tank testing and the extrapolation methods recommended by the International Towing Tank Conference (ITTC) are used and regarded as a highly accurate power prediction methodology for common cargo vessels. However, some aspects of this methodology have been questioned such as the scale effects on the form factor and its determination method. It is argued in this thesis that if a part of the Experimental Fluid Dynamics (EFD) based measure or the extrapolation procedure causes higher uncertainty than the numerical uncertainty and modelling errors of a Computational Fluid Dynamics (CFD) application, the corresponding part of the performance prediction method can be replaced or supplemented by CFD. In this study, the possibility to improve the power predictions by the introduction of a combined CFD/EFD Method was investigated by replacing the experimental determination of the form factor with double body computations based on the Reynolds-Averaged Navier-Stokes (RANS) equations, i.e. CFD based form factors. As a result of a joint, study where the double body simulations performed with seven different CFD codes, the CFD based form factors compared well with the experimentally determined form factors. Additionally, the standard deviations of the CFD based form factors were similar to the experimental uncertainty of the form factors even though the abundance of unsystematically varied methods and grids. Following the Quality Assurance Procedure proposed by the ITTC, a best practice guideline has been derived for the CFD based form factor determination method by applying systematic variations to the CFD set-ups. After the verification and validation of the CFD based form factor method in model scale, the full scale speed-power-rpm relations between large number of speed trials and full scale predictions were investigated using the CFD based form factors in combination to the ITTC-57 line and the numerical friction lines. It is observed that the usage of CFD based form factors improves the predictions in general and no deterioration in the prediction accuracy is noted within the limits of this study. Therefore, the combination of EFD and CFD is expected to provide immediate improvements to the 1978 ITTC Performance Prediction Method.
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| 47. |
- Lindgren, Ronny, 1976, et al.
(författare)
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Modeling gasoline spray-wall interactions and comparison to experimental data
- 2004
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Ingår i: SAE Technical Papers. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191 .- 2688-3627.
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Tidskriftsartikel (refereegranskat)abstract
- The effects of a gasoline spray impinging on a heated surface were investigated under simulated engine conditions in an earlier study. The data from the experimental investigation have now been compared to results obtained from Computational Fluid Dynamic (CFD) simulations generated using several different numerical models for spray-wall impingement found in the literature. It was found that the models based on single-drop experiments do not predict the outcome of spray impingement well in some respects. Their major drawback was that the predicted diameter distributions of the reflected drops in the secondary spray were shifted downwards from the measured drop size distributions. The tested models predicted the normal velocity component relative to the wall well. However, they were less good at capturing the tangential velocity component relative to the wall. Since the models did not capture the velocities in the tangential direction correctly, the spread of the secondary spray above the wall was under-predicted.
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| 48. |
- Mill, O., et al.
(författare)
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Analysis and development of hydro power research : synthesis within Swedish Hydro Power Centre
- 2010
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The market for hydropower re-investments in Sweden is approx 2.5 billion SEK/yr the coming decade. Large investments will also be carried out in Swedish tailing dams. This will result in challenging projects and need of experts. A crucial factor for a successful management of these challenges is the supply of engineers and researchers with hydro power and dam skills and knowledge. Swedish Hydro Power Centre (Svenskt vattenkraftcentrum, SVC) is a competence centre for university education and research environments within hydro power and mining dams. SVC comprises of two knowledge areas: Hydraulic Engineering and Hydro Turbines and Generators, respectively. SVC builds high-quality and long term sustainable knowledge at selected universities...
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| 49. |
- Saha, Ranjan, 1984-, et al.
(författare)
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Aerodynamic Implication of Endwall and Profile Film Cooling in a Transonic Annular Cascade
- 2013
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Ingår i: 21st ISABE Conference. - Busan, Korea.
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Konferensbidrag (refereegranskat)abstract
- An experimental study is performed to observe the aerodynamic implications of endwall and profile film cooling on flow structures and aerodynamic losses. The investigated vane is a geometrically similar transonic nozzle guide vane with engine-representative cooling geometry. Furthermore, a new formulation of the cooling aerodynamic loss equation is presented and compared with the conventional methods. Results from a 5-hole pneumatic probe show that the film coolant significantly alters the secondary flow structure. The effect of different assumptions for the loss calculation is shown to significantly change the measured loss.
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| 50. |
- Saha, Ranjan, 1984-, et al.
(författare)
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Suction and Pressure Side Film Cooling Influence on Vane Aero Performance in a Transonic Annular Cascade
- 2013
-
Ingår i: Proceedings of the ASME Turbo Expo. - 9780791855225
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Konferensbidrag (refereegranskat)abstract
- An experimental study on a film cooled nozzle guide vane has been conducted in a transonic annular sector to observe the influence of suction and pressure side film cooling on aerodynamic performance. The investigated vane is a typical high pressure gas turbine vane, geometrically similar to a real engine component, operated at an exit reference Mach number of 0.89. The aerodynamic results using a five hole miniature probe are quantified and compared with the baseline case which is uncooled. Results lead to a conclusion that the aerodynamic loss is influenced substantially with the change of the cooling flow rate regardless the positions of the cooling rows. The aerodynamic loss is very sensitive to the blowing ratio and a value of blowing ratio higher than one leads to a considerable higher loss penalty. The suction side film cooling has larger influence on the aerodynamic loss compared to the pressure side film cooling. Pitch-averaged exit flow angles around midspan remain unaffected at moderate blowing ratio. The secondary loss decreases (greater decrease in the tip region compared to the hub region) with inserting cooling air for all cases compared to the uncooled case.
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