| 1. |
- Da Silva, Edna, et al.
(författare)
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Preliminary design optimization of an organic Rankine cycle radial turbine rotor
- 2017
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Ingår i: PROCEEDINGS OF THE ASME TURBO EXPO: TURBINE TECHNICAL CONFERENCE AND EXPOSITION, 2017, VOL 3. - : American Society of Mechanical Engineers (ASME). - 9780791850831
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Konferensbidrag (refereegranskat)abstract
- The present study describes the application of a preliminary design approach for the optimization of an organic Rankine cycle radial turbine. Losses in the nozzle the rotor have initially been modelled using a mean-line design approach. The work focuses on a typical small-scale application of 50 kW, and two working fluids, R245fa (1,1,1,3,3,-pentafluoropropane) and R236fa (1,1,1,3,3,3-hexafluoropropane) are considered for validation purposes. Real gas formulations have been used based on the NIST REFPROP database. The validation is based on a design from the literature, and the results demonstrate close agreement the reference geometry and thermodynamic parameters. The total-to-total efficiencies of the reference turbine designs were 72% and 79%. Following the validation exercise, an optimization process was performed using a controlled random search algorithm with the turbine efficiency set as the figure of merit. The optimization focuses on the R245fa working fluid since it is more suitable for the operating conditions of the proposed cycle, enables an overpressure in the condenser and allows higher system efficiency levels. The R236fa working fluid was also used for comparison with the literature, and the reason is the positive slope of the saturation curve, somehow is possible to work with lower temperatures. Key preliminary design variables such as flow coefficient, loading coefficient, and length parameter have been considered. While several optimized preliminary designs are available in the literature with efficiency levels of up to 90%, the preliminary design choices made will only hold true for machines operating with ideal gases, i.e. typical exhaust gases from an airbreathing combustion engine. For machines operating with real gases, such as organic working fluids, the design choices need to be rethought and a preliminary design optimization process needs to be introduced. The efficiency achieved in the final radial turbine design operating with R245fa following the optimization process was 82.4%. A three-dimensional analysis of the flow through the blade section using computational fluid dynamics was carried out on the final optimized design to confirm the preliminary design and further analyze its characteristics.
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| 2. |
- Jansen, Jurgen, et al.
(författare)
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Functional analysis of monocarboxylate transporter 8 mutations identified in patients with X-linked psychomotor retardation and elevated serum triiodothyronine
- 2007
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Ingår i: Journal of Clinical Endocrinology and Metabolism. - : The Endocrine Society. - 1945-7197 .- 0021-972X. ; 92:6, s. 2378-2381
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Tidskriftsartikel (refereegranskat)abstract
- Context: T-3 action in neurons is essential for brain development. Recent evidence indicates that monocarboxylate transporter 8 (MCT8) is important for neuronal T-3 uptake. Hemizygous mutations have been identified in the X-linked MCT8 gene in boys with severe psychomotor retardation and elevated serum T-3 levels. Objective: The objective of this study was to determine the functional consequences of MCT8 mutations regarding transport of T-3. Design: MCT8 function was studied in wild-type or mutant MCT8-transfected JEG3 cells by analyzing: 1) T-3 uptake, 2) T-3 metabolism in cells cotransfected with human type 3 deiodinase, 3) immunoblotting, and 4) immunocytochemistry. Results: The mutations identified in MCT8 comprise four deletions (24.5 kb, 2.4 kb, 14 bp, and 3 bp), three missense mutations (Ala224Val, Arg271His, and Leu471Pro), a nonsense mutation (Arg245stop), and a splice site mutation (94 amino acid deletion). All tested mutants were inactive in uptake and metabolism assays, except MCT8 Arg271His, which showed approximately 20% activity vs. wild-type MCT8. Conclusion: These findings support the hypothesis that the severe psychomotor retardation and elevated serum T-3 levels in these patients are caused by inactivation of the MCT8 transporter, preventing action and metabolism of T-3 in central neurons.
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| 3. |
- Nordqvist, Melker, et al.
(författare)
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Conceptual Design of a Turbofan Engine for a Supersonic Business Jet
- 2017
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Konferensbidrag (refereegranskat)abstract
- In this work, a design for a new turbofan engine intended for a conceptual supersonic business jet expected to enter service in 2025 is presented. Due to the increasing competition in the aircraft industry and the more stringent environmental legislations, the new engine is expected to provide a low fuel burn to increase the chances of commercial success. The objective is to perform a preliminary design of a jet engine, complying with a set of specifications. The conceptual design has mainly been focused on the thermodynamic and aerodynamic design phases. The thermodynamic analysis and optimization have been carried out using the Numerical Propulsion System Simulation (NPSS) code, where the cycle parameters such as fan pressure ratio, overall pressure ratio, turbine inlet temperature and bypass ratio have been optimized for overall efficiency. With the cycle selected, and the fluid properties at the different flow stations known, the component aerodynamic design, sizing and efficiency calculations were performed using MATLAB. Several aspects of the turbomachinery components have been evaluated to assure satisfactory performance. The result is a two spool low bypass axial flow engine of similar dimensions as the reference engine but with increased efficiency. A weighted fuel flow comparison of the two engines at the key operating conditions shows a fuel burn improvement of 11.8 % for the optimized design.
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| 4. |
- Ramirez Camacho, Ramiro Gustavo, et al.
(författare)
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Cascade Optimization Using Controlled Random Search Algorithm and CFD Techniques for ORC Application
- 2016
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Konferensbidrag (refereegranskat)abstract
- The methodology for performance optimization of a cascade using CFD techniques for ORC (Organic Rankine Cycle) application are presented. The turbine ORC cascade is parameterized to achieve the maximum efficiency while using different organics fluids. The main objective of this work is to attain a maximal Cl/Cd ratio from a preliminary design. The CRSA (Controlled Random Search Algorithm) was chosen for the optimization process integrated with CFD techniques, using schemes with automatic building of parameterized geometries and meshes via "script files" interpreted by the commercial software ICEM-CFD®. Finally, for the numerical calculation of the fluid flow, the commercial software FLUENT® is used with the fluids properties, the real gases model, the turbulence model and the boundary conditions being set through "journal files". In this paper, R245fa and Toluene are used as working fluids, chosen for their characteristics curves being very different, directly influencing the behavior of the fluid during its expansion process. The results show that the methodology allows for making corrections in the initial design of the cascade shape. It will be necessary to introduce the camber function to correct for the separation of the boundary layer in the trailing edge, which is a proposal for future work.
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| 5. |
- Rezek, Thiago Junqueira, et al.
(författare)
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Multi-Objective Aerodynamic Optimization of an Unmanned Aerial Vehicle
- 2016
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In the present work, a global multi-objective optimization methodology with meta-models is developed and applied for optimizing the aerodynamic performance of an unmanned aerial vehicle (UAV) airfoil. The shape of the airfoil is obtained using a parameterization scheme based on Bezier curves. The aim is to optimize the performance of a high-lift airfoil by increasing the lift force while minimizing the pitching moment generated by the integration of the viscous and pressure forces acting on the airfoil. The proposed strategy for determining the optimal design solution for maximum lift and minimum moment is based on the construction of meta-models in conjunction with robust optimization algorithms. In more detail, a direct multi-objective optimization methodology using the concept of Pareto front is utilized. A relatively small number of design points is evaluated and their function values are stored in a database for meta-model construction. Radial Basis Functions such as multi-quadrics are used for the meta-model construction. The overall optimization process is integrated with Computation Fluid Dynamics techniques, using automatic schemes that build on parameterized airfoil geometries to construct a suitable mesh through scripts. Tcl/Tk language is employed along with the commercial software ICEM-CFD in batch mode. For the numerical calculation of the flow, the software FLUENT is used with fluid properties, turbulence model and boundary conditions set also in batch mode. It is demonstrated that the proposed methodology allows to develop realistic high performance airfoil conceptual designs, with relatively little computational effort. The methodology is generic and can be applied in a variety of problems related to fluid mechanics and heat transfer.
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