| 1. |
- Bordogna, Marco Tito, et al.
(författare)
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MUSCAT experiment : active free falling units for in situ measurements of temperature and density in the middle atmosphere
- 2013
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Ingår i: European Space Agency. - ESTEC, Noordwijk, The Netherlands : ESA Communications. - 9789290922858 ; , s. 575-582
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The main scientific objective of the MUSCAT Experimentis to develop a technique to reconstruct temperatures and density profiles in the middle atmosphere using active spherical probes. The MUSCAT experiment was launched on May 9, 2013 on the REXUS-13 sounding rocket from Esrange, in northern Sweden. The experiment ejected four probes that collected raw GPS signal. The experiment design and preliminary results are presented here.
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| 2. |
- Andersson, Petter, et al.
(författare)
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Demonstrating an approach for multidisciplinary set-based design within an aerospace research project - DEFAINE
- 2022
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Ingår i: ICAS Proceedings. - 2958-4647. ; 2022
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Konferensbidrag (refereegranskat)abstract
- This paper describes an approach for multidisciplinary set based design within an aerospace research project, DEFAINE. The project is a collaboration between the aerospace manufacturing industry, software providers and academia. The aim of the approach is to reduce the number of iterations conducted in a PD project and increase the number of design variants studied. This is expected to provide more innovative and cost efficient solutions.
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| 3. |
- Capitao Patrao, Alexandre, 1988, et al.
(författare)
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The heat transfer potential of compressor vanes on a hydrogen fueled turbofan engine
- 2024
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Ingår i: Applied Thermal Engineering. - 1359-4311. ; 236
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Tidskriftsartikel (refereegranskat)abstract
- Hydrogen is a promising fuel for future aviation due to its CO2-free combustion. In addition, its excellent cooling properties as it is heated from cryogenic conditions to the appropriate combustion temperatures provides a multitude of opportunities. This paper investigates the heat transfer potential of stator surfaces in a modern high-speed low-pressure compressor by incorporating cooling channels within the stator vane surfaces, where hydrogen is allowed to flow and cool the engine core air. Computational Fluid Dynamics simulations were carried out to assess the aerothermal performance of this cooled compressor and were compared to heat transfer correlations. A core air temperature drop of 9.5 K was observed for this cooling channel design while being relatively insensitive to the thermal conductivity of the vane and cooling channel wall thickness. The thermal resistance was dominated by the air-side convective heat transfer, and more surface area on the air-side would therefore be required in order to increase overall heat flow. While good agreement with established heat transfer correlations was found for both turbulent and transitional flow, the correlation for the transitional case yielded decent accuracy only as long as the flow remains attached, and while transition was dominated by the bypass mode. A system level analysis, indicated a limited but favorable impact at engine performance level, amounting to a specific fuel consumption improvement of up to 0.8 % in cruise and an estimated reduction of 3.6 % in cruise NOx. The results clearly show that, although it is possible to achieve high heat transfer rate per unit area in compressor vanes, the impact on cycle performance is constrained by the limited available wetted area in the low-pressure compressor.
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| 4. |
- Grönstedt, Tomas, 1970, et al.
(författare)
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Multidisciplinary assessment of a year 2035 turbofan propulsion system
- 2022
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Ingår i: 33rd Congress of the International Council of the Aeronautical Sciences, ICAS 2022. - : International Council of the Aeronautical Sciences. - 9781713871163 ; 7, s. 4981-4990
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Konferensbidrag (refereegranskat)abstract
- A conceptual design of a year 2035 turbofan is developed and integrated onto a year 2035 aircraft model. The mission performance is evaluated for CO2, noise and NOx and is compared with a notional XWB/A350-model. An OGV heat exchanger is then studied rejecting heat from an electric generator, and its top-level performance is evaluated. The fan, the booster and the low-pressure turbine of the propulsion system are subject to more detailed aero design based on using commercial design tools and CFD-optimization. Booster aerodynamic modelling output is introduced back into the performance model to study the integrated performance of the component. The top-level performance aircraft improvements are compared to top-level-trends and ICAO estimates of technology progress potential, attempting to evaluate whether there is some additional margin for efficiency improvement beyond the ICAO technology predictions for the same time frame.
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| 5. |
- Hammer, Steffen, et al.
(författare)
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Validation of a Forced Response Prediction Method for Design of Axial Compressors
- 2015
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Ingår i: International Symposium on Unsteady Aerodynamics, Aeroacoustics & Aeroelasticity of Turbomachines. ; , s. 1-8
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The linearized time-harmonic Navier-Stokes solver LINNEA is used to evaluate the forcing of a rotor blade in the transonic compressor Hulda, at part speed. Hulda is a 1½ stage demonstrator compressor consisting of a variable inlet guide vanes (VIGV), rotors, stators and outlet guide vanes (OGV). The forcing of the rotor is evaluated for different setting angles of the VIGV. The mesh study shows that, for this computational setup, a mesh independent solution was obtained in RANS simulation using CFX and in the linearized Navier-Stokes solver LINNEA for the same grid resolution.The results obtained using LINNEA are compared to results from three URANS simulations using CFX. The first URANS case uses scaled geometries and rotational periodic boundary conditions. The second and third case use the true geometry in conjunction with rotational periodic boundary conditions: “profile transformation” and with time-lagged periodic boundary conditions: “time transformation” in CFX’ nomenclature, which corresponds to time-inclined computational planes. LINNEA is run with two different boundary conditions at the inlet to the rotor domain, obtained from a RANS and URANS simulation, respectively.The forcing is evaluated at engine orders 15, 30 and 45, corresponding to VIGV passing frequency and multiples thereof. The results show that the amplitude of the tangential force variation calculated with the different methods and boundary conditions, is within a 1.3% interval based on the total tangential force for the nominal (0 degree) VIGV setting and within a 3.3% interval for the VIGV setting angle of 30 degrees at engine order 15.Using a linear time-harmonic Navier-Stokes solver to calculate forcing of a rotor blade interacting an upstream component is shown to be a possible and attractive alternative to URANS calculations. A linear harmonic simulation is less computationally demanding than a URANS simulation. The mean flow solution required by the linearized solver does not incur any additional computational effort since it is usually already available from general performance calculations. Further is shown that for URANS analyses a scaling of the model can be neglected since results obtained for a scaled model are in good agreement with results obtained for an unscaled model using profile transformation (PT) to handle the variation of pitch between components.
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| 6. |
- Jonsson, Isak, 1990, et al.
(författare)
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Design and pre-test evaluation of a low-pressure compressor test facility for cryogenic hydrogen fuel integration
- 2021
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Ingår i: Proceedings of the ASME Turbo Expo. ; 2A-2021
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Konferensbidrag (refereegranskat)abstract
- The use of hydrogen as aviation fuel is again resurfacing with unprecedented vigor. It is well known that hydrogen is a formidable heat sink and the use of heat sinks in the compression system of an aero engine may enable not only preheating of the fuel but also improve the gas turbine cycle itself. One such opportunity arises from extracting heat to the fuel as part of the compression process. This work presents the design process and pre-test evaluation of a low-speed compressor test facility dedicated to aerothermal measurements. The design has been derived from a high-speed transonic compressor developed for a large sized geared turbofan engine. The proposed pre-test evaluation methodology provides a comprehensive and affordable way to estimate facility accuracy by virtually addressing all the experimental procedures, from data acquisition to a final performance map. The evaluation of gathering compressor performance parameters via a gas-path investigation process was achieved while relying on results from numerical simulations. The pre-test evaluation details uncertainties introduced throughout this process with transducers, flow and probe specific errors, traverse discretization, and data normalization. A suitable instrumentation configuration is presented which shows that the performance parameters pressure ratio (P) and isentropic efficiency (hc) can be determined with uncertainties below 1% for most operating conditions and below 0.5% at design conditions.
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| 7. |
- Jonsson, Isak, 1990, et al.
(författare)
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Feasibility Study of a Radical Vane-Integrated Heat Exchanger for Turbofan Engine Applications
- 2020
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Ingår i: Proceedings of the ASME Turbo Expo. ; 7C
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Konferensbidrag (refereegranskat)abstract
- The density of liquid hydrogen (LH2), at the normal boiling point, is two times higher than that of highly compressed hydrogen. This makes LH2 the prime candidate for hydrogen storage in aviation. However, LH2 is stored at cryogenic temperatures that require adequate insulation, as well as the integration of heat exchangers to warm up the hydrogen on its way to the combustion chamber. Ideally, the required heat exchangers are strategically placed in the engine core to produce optimum heat management, thus improving the engine efficiency, increase its durability as well as to reduce emissions. Moreover, the combination of hydrogen high specific heat with cryogenic temperatures results in formidable cooling capacity, that can be explored by more compact HEX solutions. The present work numerically investigates a novel concept of a compact compressor vane-integrated heat exchanger, for application in cryogenically fuelled gas turbine engines. The baseline engine used for establishing the HEX requirements is a large geared turbofan, operating on liquid hydrogen. The HEX aero-thermal performance is first estimated using zero-dimensional models and Chalmers in-house gas turbine performance tool GESTPAN. After, the conceptual design of an outlet guide vane-HEX is developed and integrated into a three-stage low-pressure compressor. The baseline compressor geometry is a lightly loaded high-speed booster with a design pressure ratio of 2.8. The multi-stage compressor with the integrated HEX is evaluated using steady-state computational fluid dynamics. Results allow to estimate the heat exchanger performance in terms of total pressure loss, heat transfer effectiveness, and the potential enhanced radial flow turning capability. Further, the impact of the new developed OGV-HEX on the compressor characteristics is also reported and discussed.
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| 8. |
- Lejon, Kjell O., et al.
(författare)
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Less Religion, Better Society? On Religion, Secularity and Prosperity in Scandinavia.
- 2011
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Ingår i: Dialog. - Hoboken, NJ, U.S.A : Wiley-Blackwell. - 0012-2033 .- 1540-6385. ; 50:3, s. 297-307
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Tidskriftsartikel (refereegranskat)abstract
- Phil Zuckerman argues in his book Society without God that Scandinavian secularity is strongly correlated to Scandinavian prosperity. In this article, we argue that such usage is premature. First, there are methodological issues that are not properly dealt with. Second, providing a causal narrative in addition to mere correlation is needed. Third, we argue that the causes of Scandinavian prosperity are found in close connection to Scandinavian Lutheranism.
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| 9. |
- Lejon, Marcus, 1986
(författare)
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Aerodynamic design framework for low-pressure compression systems
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Aircraft engine manufacturers strive to improve current state of the art designs through continuous development efforts. By improving existing designs and exploring new alternatives, the goal is to reduce the fuel consumption - a topic of high relevance due to the remarkable growth rate of air traffc. To achieve a low fuel consumption, turbofan engines should operate at a high overall pressure ratio which is commonly achieved by an axial compressor. An axial compressor consists of a set of consecutive stages, each consisting of a rotating and stationary blade row. While a compressor should operate with a high pressure ratio, it should not operate too close to its stability limit where surge can occur. If surge occur in the compressor, the compressor blades will be subject to large transient forces and the ow may even reverse direction. The main focus of this thesis is the further development of an aerodynamic design framework for low-pressure systems, where an appropriate level of modeling is selected and compressor stages are optimized with respect to effciency and stability. Different approaches are used to evaluate stability of a compressor stage and it is concluded that the static pressure rise capability of the stage is an appropriate measure to use for ranking designs in an optimization. As a part of this thesis, all three stages of a three-stage compressor are optimized using steady state RANS calculations, and the performance of the three-stage compressor is evaluated as an assembly. The possibility of replacing blade geometries to improve part- or design speed stability of the three-stage compressor is shown. Other aspects which may penalize efficiency are investigated, namely the in uence of surface roughness and manufacturing variations on performance. The in uence of surface roughness on optimal stage designs is assessed by optimizing compressor blades with and without taking surface roughness into account. The impact of manufacturing variations on performance at a design point is investigated by utilizing measurements of a manufactured compressor blisk.
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| 10. |
- Lejon, Marcus, 1986, et al.
(författare)
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CFD Optimization of a Transonic Compressor Stage with a Large Tip Gap
- 2015
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Ingår i: ISABE International Society for Air Breathing Engines. ; , s. 1-11
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Large tip gaps can be found in the rear stages of transonic compressors. If the size of the tip gap is large in relation to the blade height it will likely affect the flow in the rotor passage significantly. Therefore, including a large tip gap in the optimization process of a compressor stage can already be of importance in the early design phase.In the present study, a transonic compressor stage is optimized with and without a large tip gap (2.5% of the rotor leading edge span) with respect to part speed stability and polytropic efficiency at a design point. The performance is evaluated using 3D CFD calculations. The two approaches are compared to determine the importance of including the tip gap in the optimization.It is shown that, when the compressor stage is optimized with a tip gap, redistribution of mass flow in the rotor passage affects the design at mid span and near the hub. A lower stagger angle is preferred away from the tip region to allow for a higher mass flow at lower spanwise positions.The k-epsilon turbulence model with wall functions is used to evaluate the performance of the stages during optimization. To support the use of wall functions, Chien’s low-Reynolds model with a more dense mesh is used to evaluate the polytropic efficiency of a number of stages with a tip gap. The results show that the ranking of designs using a low-Reynolds model show the same trend as using wall functions.
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