| 1. |
|
|
| 2. |
- Lejon, Marcus, 1986, et al.
(författare)
-
Multidisciplinary Design of a Three Stage High Speed Booster
- 2017
-
Ingår i: ASME Turbo Expo 2017: Turbine Technical Conference and Exposition. - : ASME Press. ; 2B-2017
-
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.
|
|
| 3. |
- Thulin, Oskar, 1987, et al.
(författare)
-
First and Second Law Analysis of Radical Intercooling Concepts
- 2018
-
Ingår i: Journal of Engineering for Gas Turbines and Power. - : ASME International. - 1528-8919 .- 0742-4795. ; 140:8, s. 081201-081201-10
-
Tidskriftsartikel (refereegranskat)abstract
- An exergy framework was developed taking into consideration a detailed analysis of the heat exchanger (HEX) (intercooler (IC)) component irreversibilities. Moreover, it was further extended to include an adequate formulation for closed systems, e.g., a secondary cycle (SC), moving with the aircraft. Afterward, the proposed framework was employed to study two radical intercooling concepts. The first proposed concept uses already available wetted surfaces, i.e., nacelle surfaces, to reject the core heat and contributes to an overall drag reduction. The second concept uses the rejected core heat to power a secondary organic Rankine cycle and produces useful power to the aircraft-engine system. Both radical concepts are integrated into a high bypass ratio (BPR) turbofan engine, with technology levels assumed to be available by year 2025. A reference intercooled cycle incorporating a HEX in the bypass (BP) duct is established for comparison. Results indicate that the radical intercooling concepts studied in this paper show similar performance levels to the reference cycle. This is mainly due to higher irreversibility rates created during the heat exchange process. A detailed assessment of the irreversibility contributors, including the considered HEXs and SC, is made. A striking strength of the present analysis is the assessment of the component-level irreversibility rate and its contribution to the overall aero-engine losses.
|
|
| 4. |
- Thulin, Oskar, 1987
(författare)
-
On the Analysis of Energy Efficient Aircraft Engines
- 2017
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Aero engine performance analysis is highly multidimensional using various measures of component performance such as turbomachinery and mechanical efficiencies, and pressure loss coefficients. Using conventional performance analysis, relying on only the laws of thermodynamics, it is possible to understand how the performance parameters affect the component performance, but it is difficult to directly compare the magnitude of various loss sources. A comprehensive framework has been detailed to analyze aero engine loss sources in one common currency. As the common currency yields a measure of the lost work potential in every component, it is used to relate the component performance to the system performance. The theory includes a more detailed layout of all the terms that apply to a propulsion unit than presented before. The framework is here adopted to real gases to be used in state of the art performance codes. Additionally, the framework is further developed to enable detailed studies of two radical intercooling concepts that either rejects the core heat in the outer nacelle surfaces or uses the core heat for powering of a secondary cycle. The theory is also extended upon by presenting the installed rational efficiency, a true measure of the propulsion subsystem performance, including the installation effects of the propulsion subsystem as it adds weight and drag that needs to be compensated for in the performance assessment.
|
|
| 5. |
- Heshmati, Mohsen, 1987, et al.
(författare)
-
Dependency of cohesive laws of a structural adhesive in Mode-I and Mode-II loading on moisture, freeze-thaw cycling, and their synergy
- 2017
-
Ingår i: Materials and Design. - : Elsevier BV. - 1873-4197 .- 0264-1275. ; 122, s. 433-447
-
Tidskriftsartikel (refereegranskat)abstract
- In recent years, adhesive bonding has found its way to construction applications such as bridges. Given the harsh conditions that such structures are usually exposed to, it is necessary to account for environmental factors, particularly moisture and temperature, in the design phase. Cohesive zone modelling has attracted much attention in the last decade as a promising method to design adhesive joints. Despite this interest, the effects of moisture and thermal cycles on cohesive laws have not been investigated to the knowledge of the authors. In this paper, we present a method to directly measure the environmental-dependent cohesive laws of a structural adhesive loaded in pure Mode-I and Mode-II. Special consideration is given to overcome issues such as the time-consuming nature of moisture ingression and specimen dimensions, which could be problematic due to the size-limitations of conditioning equipment. The accuracy of this method was verified through simulation of the experiments using the finite element analysis. The effects of exposure to 95% relative humidity, immersion in saltwater and distilled water, and freeze-thaw cycles in the presence or absence of moisture were investigated. The results indicate the damaging effects of combined saltwater and freeze-thaw cycles which were clearly reflected on the shape of the cohesive laws.
|
|
| 6. |
|
|
| 7. |
- Shetty, Sandeep
(författare)
-
Optimization of Vehicle Structures under Uncertainties
- 2017
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Advancements in simulation tools and computer power have made it possible to incorporate simulation-based structural optimization in the automotive product development process. However, deterministic optimization without considering uncertainties such as variations in material properties, geometry or loading conditions might result in unreliable optimum designs. In this thesis, the capability of some established approaches to perform design optimization under uncertainties is assessed, and new improved methods are developed. In particular, vehicle structural problems which involve computationally expensive Finite Element (FE) simulations, are addressed.The first paper focuses on the evaluation of robustness, given some variation in input parameters, the capabilities of three well-known metamodels are evaluated. In the second paper, a comparative study of deterministic, reliability-based and robust design optimization approaches is performed. It is found that the overall accuracy of the single-stage (global) metamodels, which are used in the above study, is acceptable for deterministic optimization. However, the accuracy of performance variation prediction (local sensitivity) must be improved. In the third paper, a decoupled reliability-based design optimization (RBDO) approach is presented. In this approach, metamodels are employed for the deterministic optimization only while the uncertainty analysis is performed using FE simulations in order to ensure its accuracy.In the fifth paper, two new sequential sampling strategies are introduced that aim to improve the accuracy of the metamodels efficiently in critical regions. The capabilities of the methods presented are illustrated using analytical examples and a vehicle structural application.It is important to accurately represent physical variations in material properties since these might exert a major influence on the results. In previous work these variations have been treated in a simplified manner and the consequences of these simplifications have been poorly understood. In the fourth paper, the accuracy of several simple methods in representing the real material variation has been studied. It is shown that a scaling of the nominal stress-strain curve based on the Rm scatter is the best choice of the evaluated choices, when limited material data is available.In this thesis work, new pragmatic methods for non-deterministic optimization of large scale vehicle structural problems have been developed. The RBDO methods developed are shown to be flexible, more efficient and reasonably accurate, which enables their implementation in the current automotive product development process.
|
|
| 8. |
- Sundin, Maria, 1965, et al.
(författare)
-
Space Sports - Sailing in Space
- 2016
-
Ingår i: Proceedings from icSports 2016, 4th International Conference on Sport Sciences Research and Technology Support, Porto, Portugal, 7-9 november 2016. - : SCITEPRESS - Science and Technology Publications. - 9789897582059 ; , s. 141-146
-
Konferensbidrag (refereegranskat)abstract
- Titan is the largest moon of Saturn, and apart from the Earth it is the only body in our solar system where a liquid exists on the surface. Within the last ten years a system of lakes and rivers have been discovered. The climate and seasonal cycles of Titan are still not very well known, but the composition and pressure are fairly well established. Perhaps in the future boats will sail the lakes of Titan for research purposes or even sport. The purpose of this paper is to give an overview of the concept of space sports, the conditions of Titan and to calculate important parameters of sailing such as floatability, stability, hull resistance and sail forces. This paper shows that if a sailing yacht on Titan will have twice as large displacement as on Earth, it will be 2.6 times less stable for the same beam. Since friction will be smaller, it will be faster than on Earth at low speed, but significantly slower at high speeds due to the wave generation. The same sail area is required to get the same sail forces if the average wind is 3 m/s, while a 9 times larger sail area is required for if the wind speed is only 1 m/s.
|
|
| 9. |
- Safavi, Edris, et al.
(författare)
-
Implementation of collaborative multidisciplinary design optimization for conceptual design of a complex engineering product
- 2016
-
Ingår i: Concurrent Engineering - Research and Applications. - : Sage Publications. - 1063-293X .- 1531-2003. ; 24:3, s. 251-265
-
Tidskriftsartikel (refereegranskat)abstract
- This study investigates the performance of the collaborative multidisciplinary design optimization framework and how it facilitates the knowledge integration process. The framework is used to design and optimize an innovative concept of a tidal water power plant. The case study helps to highlight the challenges that may occur during implementation. The result is presented as a modified framework with less implementation difficulties. The improved framework shows significant reduction in design time and improvement in collaborative design optimization for a design team. The geometry of the product is optimized to minimize weight and maximize the power generated by the turbine with respect to some mechanical constraints.
|
|
| 10. |
- Forslund, Anders, 1982
(författare)
-
Uncertainty and Robustness in Aerospace Structures
- 2016
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Engineering is not an exact science. In fact, all engineering activity contain some degree of assumption, simplification, idealization, and abstraction. When engineered creations meet reality, every manufactured product behaves differently. This variation can be detrimental to product quality and functionality. In an aerospace context, this variation may even result in serious threats to the safety and reliability of aircraft. However, it is not the variation in and of itself that is harmful, but the effects it imposes on functionality—an important distinction to make. Reducing sources of variation is often associated with tightening tolerances and increasing cost. Instead, it is preferable to eliminate the effects of this variation by making designs more robust. This idea is at the core of robust design methodology. Aerospace is an industry characterized by the complexity of its products and the multidisciplinary nature of its product development. In such contexts, there are significant barriers against implementing uncertainty-based design practices. The research presented in this thesis aims at identifying the role of robust design in general, and geometry assurance in particular, in the early phases of aerospace component design. Further, this thesis proposes a methodology by which geometry assurance practices may be implemented in this setting. The methodology consists of a modelling approach linked to a multidisciplinary simulation environment. In a series of case studies, the methodology is tested in an industrial setting. The capability of the methodology is demonstrated through several applications, in which the effects of geometric variation on the aerodynamic, thermal, and structural performance of a load-bearing turbofan component are analysed. Investigated effects include part variation, fixture variation, part configuration and welding. The proposed methodology overcomes many of the current barriers, making it more feasible to assess geometric variation in the early design phases. Despite some limitations, the methodology contributes to an academic understanding of how to evaluate geometric variation in multidisciplinary simulations and provides a tool for industry. Geometric variation is only one source of uncertainty amongst many others. By evaluating geometric variation against the framework of uncertainty quantification, this thesis addresses the relative importance of geometry assurance against other product development activities.
|
|
