| 1. |
- Capitao Patrao, Alexandre, 1988, et al.
(författare)
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Compact heat exchangers for hydrogen-fueled aero engine intercooling and recuperation
- 2024
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Ingår i: Applied Thermal Engineering. - 1359-4311. ; 243
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Tidskriftsartikel (refereegranskat)abstract
- This study investigates the application of compact heat exchangers for the purpose of intercooling and recuperation systems for short-to-medium range aircraft equipped with hydrogen-fueled turbofan engines. The primary objective is to assess the potential effects of engine-integrated compact heat exchangers on fuel consumption and emissions. The paper encompasses the conceptual design of integrated heat exchangers and associated ducts, followed by aerodynamic optimization studies to identify suitable designs that minimize air-side pressure losses and ensure flow uniformity at the inlet of the high-pressure compressor. Pressure drop correlations are then established for selected duct designs and incorporated into a system-level performance model, allowing for a comparison of their impact on specific fuel consumption, NOx emissions, and fuel burn against an uncooled baseline engine. The intercooled-recuperated engine resulted in the most significant improvement in take-off specific fuel consumption, with a reduction of up to 7.7% compared to the baseline uncooled engine, whereas the best intercooled engine resulted in an improvement of about 4%. Furthermore, the best configuration demonstrated a decrease in NOx emissions by up to 37% at take-off and a reduction in mission fuel burn by 5.5%. These enhancements were attributed to reduced compression work, pre-heating of the hydrogen fuel, and lower high-pressure compressor outlet temperatures.
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| 2. |
- 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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| 3. |
- Huang, Zhongjie, 1985, et al.
(författare)
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Aeroacoustic analysis of aerodynamically optimized joined-blade propeller for future electric aircraft at cruise and take-off
- 2020
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Ingår i: Aerospace Science and Technology. - : Elsevier BV. - 1270-9638. ; 107
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Tidskriftsartikel (refereegranskat)abstract
- A novel propeller with the blade tips joined in pairs, named Boxprop, is designed and optimized for a conceptual electric aircraft using an efficient optimization platform. According to the thrust requirement of the electric aircraft at cruise, the Boxprop with optimal efficiency is down-selected from the Pareto front of thrust coefficient and propeller efficiency. Furthermore, the blade pitch angle is adjusted to meet the thrust requirement at take-off. It is found that the Boxprop is capable of suppressing tip vortices and inducing a wider wake behind blade tip in comparison to a conventional propeller usually shedding a concentrated tip vortex, which could potentially improve the propulsive efficiency. Afterwards, the aeroacoustic analysis performed by the hybrid integral method of Reynolds-Averaged Navier Stokes equations (RANS) and convected Ffowcs Williams and Hawkings (FW-H) equation shows that the tonal noise from the Boxprop with three joined blades operating at cruise is similar to a conventional three-bladed propeller, though being stronger than a conventional six-bladed propeller. Although the tip vortices have been suppressed by the joined-blade tips of the Boxprop, the corresponding tonal noise reduction is not prominent. Next, the Boxprop noise at take-off is studied. Unsteady RANS is used to resolve varying flow structures that become dominant under the take-off condition. Angle of attack (AOA) is found as an important factor influencing the noise generation. The radiated noise upstream and downstream of the propeller significantly intensifies due to increasing AOA. The AOA effects of the Boxprop follow a similar trend to a conventional propeller. The findings for the Boxprop aeroacoustics have enhanced the understanding of tip-vortex suppression techniques in connection with the tonal noise generation, which will be greatly helpful to the aeroacoustic design of Boxprop applied to electric aircraft in the future.
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| 4. |
- Huang, Zhongjie, 1985, et al.
(författare)
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Low-Noise Propeller Design for Quiet Electric Aircraft
- 2020
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Ingår i: AIAA AVIATION 2020 FORUM. - Reston, Virginia : American Institute of Aeronautics and Astronautics.
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Konferensbidrag (refereegranskat)abstract
- Inspired by the tremendous success of electric cars, the electrification technology has recently attracted a great deal of attention in aviation industry. This leads to the advent of massive efforts on the development of electric aircraft. Electrification enables zero CO2 and NOx emissions for aircraft in the near future. However, the annoying noise radiated from electrified propulsion systems is still a great challenge. The major noise sources are propellers. In particular, short-haul electric aircraft are usually flying from small airports near communities, which would exaggerate the noise impacts on residents. This paper presents a study on the propeller noise for a hypothetical electric aircraft. First of all, the acoustic study focuses on the effects of blade number, blade diameter, and rotation speed for an isolated propeller. Then, an unique configuration of dual-rotating propeller is briefly investigated to explore its potential of low-noise generation. Lastly, multiple propellers installed on an aircraft with various distributive propulsion strategies are investigated. The overall noise emission of these distributive propulsion strategies are promising to reduce the total noise from electric aircraft. Nonetheless, the noise level is very sensitive to the installation location of every propeller. An interesting finding is that the acoustic-wave interaction among the propellers are limited to the near field, and is insignificant in the far field. The present results are expected to enhance the understanding of propeller noise generation mechanisms, which are beneficial to propose guidelines on the development of low-noise distributive propulsion systems for electric aircraft.
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| 5. |
- Jouannet, Christopher, et al.
(författare)
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SUSTAINABLE AVIATION FOR SWEDEN - TECHNOLOGY & CAPABILITY ASSESSMENT TARGETING 2045
- 2022
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Ingår i: 33rd CONGRESS OF THE INTERNATIONAL COUNCIL OF THE AERONAUTICAL SCIENCES. - 2958-4647.
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Konferensbidrag (refereegranskat)abstract
- The goal of this project is to analyse the possibilities offered by different technological solutions to achieve zero emission aviation, firstly in the Swedish/Nordic network context and secondly extend this to the European context. This project will investigate the potential and feasibility of new or upgraded aircraft types based on the different technologies mapped from both, various published roadmaps and national expertise from Swedish aerospace universities and companies. This involves developing aircraft conceptual designs studies and trade analysis with regards to different fuel types, propulsion technologies, structure, operations, network and fleet management, and all relevant technologies. The project will, on a common technology basis, analyse a range of zero carbon fuels and associated technologies through operational studies and optimization to accelerate the introduction of fossil free aircraft technology and choosing optimal paths for making aviation sustainable.
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| 6. |
- Sethi, V., et al.
(författare)
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Enabling Cryogenic Hydrogen-Based CO 2 -Free Air Transport: Meeting the demands of zero carbon aviation
- 2022
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Ingår i: IEEE Electrification Magazine. - 2325-5889 .- 2325-5897. ; 10:2, s. 69-81
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Flightpath 2050 from the European Union (EU) sets ambitious targets for reducing the emissions from civil aviation that contribute to climate change. Relative to aircraft in service in year 2000, new aircraft in 2050 are to reduce CO2 emissions by 75% and nitrogen oxide (NOx) emissions by 90% per passenger kilometer flown. While significant improvements in asset management and aircraft and propulsion-system efficiency and are foreseen, it is recognized that the Flightpath 2050 targets will not be met with conventional jet fuel. Furthermore, demands are growing for civil aviation to target zero carbon emissions in line with other transportation sectors rather than relying on offsetting to achieve 'net zero.' A more thorough and rapid greening of the industry is seen to be needed to avoid the potential economic and social damage that would follow from constraining air travel. This requires a paradigm shift in propulsion technologies. Two technologies with potential for radical decarbonization are hydrogen and electrification. Hydrogen in some form seems an inevitable solution for a fully sustainable aviation future. It may be used directly as a fuel or combined with carbon from direct air capture of CO2 or other renewable carbon sources, to synthesize drop-in replacement jet fuels for existing aircraft and engines. As a fuel, pure hydrogen can be provided as a compressed gas, but the weight of the storage bottles limits the practical aircraft ranges to just a few times that is achievable with battery power. For longer ranges, the fuel needs to be stored at lower pressures in much lighter tanks in the form of cryogenic liquid hydrogen (LH2).
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| 7. |
- Sjögren, Oliver, 1993, et al.
(författare)
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FAN STAGE DESIGN AND PERFORMANCE OPTIMIZATION FOR LOW SPECIFIC THRUST TURBOFANS
- 2023
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Ingår i: International Journal of Turbomachinery, Propulsion and Power. - 2504-186X. ; 8:4
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Tidskriftsartikel (refereegranskat)abstract
- In modern turbofan engines the bypass section of the fan stage alone provides the majority of the total thrust in cruise and the size of the fan has a considerable effect on overall engine weight and nacelle drag. Thrust requirements in different parts of the flight envelope must also be satisfied together with sufficient margins towards stall. An accurate description of the interdependencies of relevant performance and design attributes of the fan stage alone - such as efficiency, surge margin, fan-face Mach number, stage loading, flow coefficient and aspect ratio - are therefore necessary to estimate system level objectives such as mission fuel burn and direct operating cost with enough confidence during the conceptual design phase. The contribution of this study is to apply a parametric optimization approach to conceptual design of fan stages for low specific thrust turbofans based on the streamline curvature method. Trade-offs between fan stage attributes for Pareto-optimal solutions are modelled by training a Kriging surrogate model on the results from the parametric optimization. The trends predicted by the resulting surrogate model are analyzed both quantitatively and qualitatively. Most of the trends could be justified with some degree of physical reasoning or comparison with common guidelines from the literature. Trends of stage efficiency with Mach number and stage loading may indicate that shock losses have a larger impact on stage efficiency for designs with low stage loading compared to designs with high stage loading. Means to reduce the strength of the passage shock wave, such as blade sweep, may therefore be of more importance as stage loading is reduced.
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| 8. |
- Tavares Silva, Vinícius, 1991, et al.
(författare)
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Aerodynamic Installation Effects of Over the wing Mounted Ultra high bypass Engines
- 2022
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In order to increase propulsive efficiency and decrease specific thrust, future aeroengines for commercial airliners will have to operate with higher bypass ratios and lower fan pressure ratios. This results in a substantial increase of the fan diameter. One major issue with the conventional under-wing installation of ultrahigh-bypass engines is the limited space underneath the wings. Integrating larger engines under-the-wings could require prohibitive increase in landing gear height and weight to attain an adequate ground clearance. One potential solution is to mount the engines over-the-wings, which would eliminate the ground clearance problem and, in addition, reduce ground noise. Over-wing nacelle installation acquired a bad reputation in the past since the benefits of such configuration would be often outweighed by poor aerodynamic performance. Nonetheless, some recent studies indicate that over-wing mounted nacelles could be a feasible integration option. This paper provides an aerodynamic evaluation of an over-the-wing mounted nacelle configuration compared with an under-the-wing configuration for a mid-cruise condition. The nacelles and pylons are designed by using an in-house tool for engine aircraft aerodynamic integration. The flow field is computed by means of Reynolds-averaged Navier-Stokes equations. The effects of wing/nacelle/pylon interference are investigated, and the aerodynamic performance of each configuration is evaluated by means of thrust and drag bookkeeping. Results show that the over-the-wing nacelle installation has increased the overall drag by 19.7 drag counts, when compared to a conventional under-wing mount, which was caused mainly due to a higher wing wave drag and pylon/nacelle interference drag.
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| 9. |
- Tavares Silva, Vinícius, 1991, et al.
(författare)
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MULTIPOINT AERODYNAMIC DESIGN OF A NACELLE FOR AN ELECTRIC FAN
- 2022
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Ingår i: ICAS Proceedings. - 2958-4647.
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Konferensbidrag (refereegranskat)abstract
- Attention to aircraft electrification has been growing quickly since such technology carries the potential of drastically reducing the environmental impact of aviation. This paper describes the re-design of a nacelle for an electric fan, which is developed as part of the EleFanT (Electric Fan Thruster) project. A multipoint nacelle design approach was carried out. Initially the nacelle shapes were optimized for a cruise condition by employing an evolutionary genetic algorithm (GA). The flow field around the nacelles was calculated by conducting 2D axisymmetric computational fluid dynamics (CFD) simulations, and the objective functions were computed by means of thrust and drag bookkeeping. It was found that the optimizer favored two types of nacelle shapes that differed substantially in geometry. The designs were referred to as low spillage and high spillage types. The optimum low spillage and high spillage cases were selected and investigated further by the means of 3D CFD simulations at cruise and at an end of runway takeoff condition, where the nacelle is subjected to high angle of attack. Whilst the low spillage case provided a slightly better performance at cruise, it presented high levels of distortion and boundary layer separation at takeoff, requiring a substantial shape modification. The high spillage case performed well at takeoff; however, supersonic velocities could be observed at the cowling when it was subjected to incoming flow at an angle of attack. Nonetheless, such problem was easily corrected by drooping the inlet. Due to its superior performance at takeoff, the drooped high spillage design type was recommended.
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| 10. |
- Tavares Silva, Vinícius, 1991, et al.
(författare)
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Multipoint aerodynamic design of ultrashort nacelles for ultrahigh-bypass-ratio engines
- 2022
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Ingår i: Journal of Propulsion and Power. - 1533-3876 .- 0748-4658. ; 38:4, s. 541-558
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a newly developed methodology for multipoint aerodynamic design of ultrashort nacelles for ultrahigh-bypass-ratio turbofan engines. An integrated aerodynamic framework, based on parametric geometry generation and flowfield solution via three-dimensional Reynolds-averaged Navier-Stokes equations, was built and used for designing several ultrashort nacelle shapes and to evaluate their aerodynamic performance. An approach for modeling the inlet-fan coupling is presented and validated. A design strategy is introduced, and various test cases are evaluated under the following critical operating conditions: midcruise, low speed/high angle of attack, and pure crosswind. The major design parameters are highlighted and their influence in the flowfield is discussed in detail for all the chosen flight conditions. Performance was evaluated by assessing inlet flow distortion and by bookkeeping of thrust and drag. The framework has proven to be suitable for designing high-performance nacelles capable of operating under critical flight conditions, without flow separation or high levels of distortion. Drooping the inlet by 4 deg is shown to reduce the drag at cruise by 1.9%, which also has a large beneficial impact on internal lip separation at high-incidence conditions. Furthermore, crosswind was identified as the most severe of the conditions, requiring a drastic reshaping of the nacelle to avoid internal lip separation. Two final nacelle designs were compared: the first allowed inlet separation under a 90 deg crosswind condition, whereas the second was reshaped to be separation-free under all operating conditions. Reshaping to avoid separation has increased drag by 5.1% at cruise.
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| 11. |
- Tavares Silva, Vinícius, 1991, et al.
(författare)
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Over-wing integration of ultra-high bypass ratio engines: A coupled wing redesign and engine position study
- 2023
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Ingår i: Aerospace Science and Technology. - 1270-9638. ; 138
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Tidskriftsartikel (refereegranskat)abstract
- The integration of next-generation high-bypass turbofan engines poses a major challenge to the aeronautical industry due to the larger fans necessary to achieve more fuel-efficient engines. The limited space underneath the wings and the strict ground clearance constraints bring the necessity to investigate solutions other than the conventional under-wing mounted engines. Over-wing installed nacelles have the potential to solve the ground clearance issue and, in addition, might reduce ground noise due to acoustic shielding from the wing. Nevertheless, a strong and complex coupling between aerodynamics and propulsion is the result of such integration choice, and traditional design practices may result in configurations with prohibitively high drag penalties. This paper presents a novel wing redesign method, specifically developed for over-wing mounted engines. The wing is reshaped to recover the spanwise lift distribution of the clean airframe (wing-body) configuration, for a single aisle airliner at a cruise condition. The wing redesign is conducted along with an engine position sensitivity study, in which the wing is reshaped for different engine axial and vertical positions. The coupling between propulsion and aerodynamics is thoroughly investigated, as well as the interaction and interference effects between the wing, pylon, and nacelle. Moreover, the best over-wing solution is compared to a baseline under-wing mounted nacelle. Results show that, by applying the developed method, an overall drag reduction of 17.65 counts, or 6.4%, was obtained, compared to the initial over-wing configuration, comprising the original wing and baseline engine position. Nonetheless, the best over-wing nacelle design is still 5.58 counts, or 2%, higher in overall drag compared to the baseline under-wing mounted nacelle case.
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| 12. |
- Tavares Silva, Vinícius, 1991, et al.
(författare)
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Powered Low-speed Experimental Aerodynamic Investigation of an Over-wing Mounted Nacelle Configuration
- 2023
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Ingår i: AIAA Aviation and Aeronautics Forum and Exposition, AIAA AVIATION Forum 2023.
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Konferensbidrag (refereegranskat)abstract
- Over-wing integration of ultra-high bypass turbofan engines can be a solution for next- generation commercial transport aircraft, since it eliminates the ground clearance issue, and it has the potential to reduce ground noise due to acoustic shielding. Moreover, a unique characteristic of this installation type is the powered lift benefit at low-speed flight conditions. This paper aims to experimentally investigate the effect of the engine power setting on the low-speed aerodynamic performance of an over-wing mounted nacelle configuration comprising a conventional tube-and-wing layout. Thus, low-speed wind tunnel tests were performed for a half-span powered scale model of the aforementioned configuration. The effect of the engine power setting on the wing lift and spanwise pressure distributions was investigated. The experiments were carried out for angles-of-attack varying from 0º to 6º and inlet mass flow ratios up to 2.4. The results were used to validate computational fluid dynamics simulations conducted for the same wind tunnel conditions. It has been shown that a significant powered lift benefit can be achieved for the studied configuration, without a penalty in the net propulsive force, and that the lift increases linearly with the inlet mass flow ratio. Furthermore, it was observed that the engine power setting largely influences the pressure distributions along the wing, especially at the spanwise sections closer to the nacelle. The low momentum zone created upstream of the engine at high power settings reduces the pressure at the wing’s upper surface, which is the main factor responsible for the increased lift. By taking advantage of such behavior, drag can potentially be reduced at takeoff and climb due to a lower flap setting required for the same lift.
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| 13. |
- Xisto, Carlos, 1984, et al.
(författare)
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Design and performance of liquid hydrogen fueled aircraft for year 2050 EIS
- 2022
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Ingår i: 33rd Congress of the international council of the aeronautical sciences. ; 2, s. 1119-1131
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Konferensbidrag (refereegranskat)abstract
- The present paper reports on the investigation of long-range LH2 aircraft concepts for year 2050 entry into service. The paper attempts to identify the limitations set by the LH2 storage technology when targeting typical design payload-range missions. In particular, the paper aims at providing a reasonable estimate of the upper efficiency levels set by low-weight rigid cell foam insulated tank technology, when integrated in a conventionally shaped airframe. Additionally, a sensitivity study on the gravimetric efficiency of the tanks will be carried out, to identify the required roadmap for LH2 storage technology that is compliant with the typical long range mission requirements. Results for the different LH2 aircraft are compared with a year 2020 and year 2050 reference aircraft fueled with conventional jet-A.
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