| 1. |
- Dahal, Karna, 1984, et al.
(författare)
-
Techno-economic review of alternative fuels and propulsion systems for the aviation sector
- 2021
-
Ingår i: Renewable and Sustainable Energy Reviews. - : Elsevier BV. - 1879-0690 .- 1364-0321. ; 151
-
Forskningsöversikt (refereegranskat)abstract
- Substitution of conventional jet fuel with low-to zero-carbon-emitting alternative aviation fuels is vital for meeting the climate targets for aviation. It is important to understand the technical, environmental, and economic performance of alternative aviation fuels and prospective engine and propulsion technologies for future aircraft. This study reviews alternative fuels and propulsion systems, focusing on costs and technical maturity, and presents conceptual aircraft designs for different aviation fuels. The cost review includes minimum jet fuel selling price (MJFSP) for alternative aviation fuels. Direct operating cost (DOC) is estimated based on the conceptual aircraft designs and the reviewed MJFSP. The DOCs for bio-jet fuel (5.0–9.2 US cent per passenger-kilometer (¢/PAX/km)), fossil and renewable liquefied hydrogen (5.9–10.1 and 8.1–23.9 ¢/PAX/km, respectively), and electro-methane and electro-jet fuel (5.6–16.7 and 9.2–23.7 ¢/PAX/km, respectively) are higher than for conventional jet fuel (3.9–4.8 ¢/PAX/km) and liquefied natural gas (4.2–5.2 ¢/PAX/km). Overall, DOC of renewable aviation fuels is 15–500 % higher than conventional jet fuels. Among the bio-jet fuels, hydroprocessed esters and fatty acids (23–310 $/GJ) and alcohol-to-jet (4–215 $/GJ) pathways offer the lowest MJFSPs. The implementation of alternative fuels in existing aircraft engines and the design and development of appropriate propulsion systems and aircraft are challenging. The overall cost is a key factor for future implementation. Bio-jet fuel is most promising in the near term while hydrogen and electrofuels in the long term. The level of carbon tax on fossil jet fuels needed for the latter options to be competitive depend on the hydrogen production cost.
|
|
| 2. |
- Abedi, Hamidreza, 1979, et al.
(författare)
-
Preliminary Analysis of Compression System Integrated Heat Management Concepts Using LH 2 -Based Parametric Gas Turbine Model
- 2022
-
Ingår i: Aerospace. - : MDPI AG. - 2226-4310. ; 9:4
-
Tidskriftsartikel (refereegranskat)abstract
- The investigation of the various heat management concepts using LH2 requires the development of a modeling environment coupling the cryogenic hydrogen fuel system with turbofan performance. This paper presents a numerical framework to model hydrogen-fueled gas turbine engines with a dedicated heat-management system, complemented by an introductory analysis of the impact of using LH2 to precool and intercool in the compression system. The propulsion installations comprise Brayton cycle-based turbofans and first assessments are made on how to use the hydrogen as a heat sink integrated into the compression system. Conceptual tubular compact heat exchanger designs are explored to either precool or intercool the compression system and preheat the fuel to improve the installed performance of the propulsion cycles. The precooler and the intercooler show up to 0.3% improved specific fuel consumption for heat exchanger effectiveness in the range 0.5–0.6, but higher effectiveness designs incur disproportionately higher pressure losses that cancel-out the benefits.
|
|
| 3. |
- Capitao Patrao, Alexandre, 1988, et al.
(författare)
-
Compact heat exchangers for hydrogen-fueled aero engine intercooling and recuperation
- 2024
-
Ingår i: Applied Thermal Engineering. - 1359-4311. ; 243
-
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.
|
|
| 4. |
- Capitao Patrao, Alexandre, 1988, et al.
(författare)
-
Compact Heat Exchangers With Curved Fins for Hydrogen Turbofan Intercooling
- 2024
-
Ingår i: Journal of Engineering for Gas Turbines and Power. - 1528-8919 .- 0742-4795. ; 146:11
-
Tidskriftsartikel (refereegranskat)abstract
- Hydrogen is being considered as a possible path toward carbon-neutral aviation. There are additional advantages besides its main benefit ofCO2-free combustion. One application is to use it for aero engine heat management due to its cryogenic temperature and high heat capacity, including intercooling and exhaust heat recuperation. The focus of this paper is on the design of a compact heat exchanger (HEX) integrated into an intermediate compressor duct (ICD), which could decrease compression work and specific fuel consumption (SFC). This compact heat exchanger features curved fins to promote flow turning and decrease pressure losses compared to more conventional straight fin heat exchangers. Conceptual design and duct shape optimization has been carried out which produced integrated ICD heat exchanger designs with significantly lower air-side total pressure losses compared to their conventional straight fin counterparts, which could improve system level integration and engine performance. A direct outcome of this study is a pressure loss correlation, which can be used in future engine system-level trade studies.
|
|
| 5. |
- Capitao Patrao, Alexandre, 1988, et al.
(författare)
-
Numerical modeling of laminar-turbulent transition in an interconnecting compressor duct
- 2022
-
Ingår i: 33rd Congress of the International Council of the Aeronautical Sciences, ICAS 2022. ; 2022:3, s. 2033-2044
-
Konferensbidrag (refereegranskat)abstract
- Cryogenic hydrogen is being considered as a future aviation fuel since it eliminates CO2, CO, soot, sulphur, and unburnt hydrocarbons emissions. The storage temperature and high cooling capacity of cryogenic hydrogen also makes it a suitable coolant. In this paper a integrated heat exchanger in an interconnecting compressor duct (ICD) is analyzed with respect to heat transfer and transition.
|
|
| 6. |
- Capitao Patrao, Alexandre, 1988, et al.
(författare)
-
The heat transfer potential of compressor vanes on a hydrogen fueled turbofan engine
- 2024
-
Ingår i: Applied Thermal Engineering. - 1359-4311. ; 236
-
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.
|
|
| 7. |
- Dias, Filipe, et al.
(författare)
-
Analysis and Comparison of Different Chemistry Models for the Computation of Reacting Flows on Re-entry and Hypersonic Vehicles
- 2019
-
Ingår i: AIAA Propulsion and Energy Forum and Exposition, 2019. - Reston, Virginia : American Institute of Aeronautics and Astronautics. - 9781624105906 ; 2019
-
Konferensbidrag (refereegranskat)abstract
- An aircraft in hypersonic flight regime is enveloped in a plasma layer due to the high temperatures involved. This electronic plasma layer will be responsible for cutting-off communications to and from the aircraft, in a phenomenon known as radio blackout. Several methods have been proposed to mitigate radio blackout, amongst which is the "magnetic window". In the magnetic window method a magnetic field is imposed near the antenna, opening a spectral window, allowing the passage of electromagnetic waves without distortion. Experimental replication of hypersonic flight is extremely costly, generating a keen interest in the development of numerical codes capable of simulating weakly ionized flow around a hypersonic vehicle. This is specially relevant for investigating blackout mitigation methods, since a validated numerical code will allow the preliminary design and optimization of new concepts, in a much faster and cheaper way. A numerical code that is used to simulate a plasma layer around an aircraft needs to accurately predict the electron density and associated plasma properties. Several distinct chemistry models have been proposed. In this paper, four chemistry models will be studied, each accounting for 11 species commonly found in an atmospheric plasma layer: N2; O2; NO; N; O; N2+ ; O2+ ; NO+; N+; O+ and e−. The electron number density calculated with each model is compared with the electron number density calculated in the RAM-C II experimental flight. The models will be compared in terms of simulation runtime as well, in an attempt to assess which requires less processing power.
|
|
| 8. |
- Dias, F., et al.
(författare)
-
Numerical analysis of a multi-species MHD model for plasma layer control of re-entry vehicles
- 2018
-
Ingår i: ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE). - 9780791852002 ; 1
-
Konferensbidrag (refereegranskat)abstract
- Several critical aspects control the successful reentry of vehicles on the earth’s atmosphere: continuous communication, GPS signal reception and real-time telemetry. However, there are some common issues that can interfere with the instruments operation, the most typical being the radio blackout, in which the plasma layer frequency modifies the electromagnetic waves in a way that makes communications to and from the spacecraft impossible. So far, there have been several proposed techniques to mitigate radio blackout, one of which is the usage of electromagnetic fields. Previous studies have proven the effectiveness of the usage of an electric and/or magnetic fields to manipulate plasma layers. Experiments on plasma layer manipulation during hypersonic flight regime are extremely costly. Therefore, there has been a continuous interest in the development of cheaper solutions, that can guarantee a reliable degree of accuracy, such as the development of complex multiphysics computational models. These models are becoming increasingly realistic and accurate, as more and more physical aspects can be considered, greatly increasing the accuracy and range of models. However, those models need to be validated with recourse to experimental data. In this paper we propose a model that uses a Low Magnetic Reynolds number, and accounts for five common neutral species: N2, O2, NO, N and O, along with several of their respective reactions: dissociation of molecular nitrogen and oxygen, and exchange. The model chemistry is then validated based on experimental data gathered by several authors.
|
|
| 9. |
- Dias, F., et al.
(författare)
-
Numerical Computations of MHD Flow on Hypersonic and Re-Entry Vehicles
- 2016
-
Ingår i: Proceedings of the ASME International Mechanical Engineering Congress and Exposition (IMECE2016). ; 1, s. Paper No. IMECE2016-65676
-
Konferensbidrag (refereegranskat)abstract
- In hypersonic flight of reentry vehicles the radio blackout is a typical problem, in particular because it arises during a critical mission operation point. To mitigate this radio blackout the magnetic window concept is proposed. In this work a numerical model is presented to accurately simulate the effect of a magnetic field interacting with ionized plasma surrounding the vehicle. The numerical model is based on the MHD flow equations. Initially, the code is validated for pure hypersonic gas dynamics. Diverse high resolution spatial discretisation schemes, within a Finite Volume framework, are analyzed for robustness. Afterwards, the numerical code is further validated for MHD flows using the well-known Hartmann case. A very good comparison between numerical and analytical results is verified. This allows a proper validation of the method in terms of Lorentz force, in particular under low-magnetic Reynolds number conditions. A very tough test-case is finally computed, being typical of a reentry capsule geometry. The accuracy of the model is then verified for different applied magnetic fields.
|
|
| 10. |
- Grewe, V., et al.
(författare)
-
Evaluating the climate impact of aviation emission scenarios towards the Paris agreement including COVID-19 effects
- 2021
-
Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723 .- 2041-1723. ; 12:1
-
Tidskriftsartikel (refereegranskat)abstract
- Aviation is an important contributor to the global economy, satisfying society’s mobility needs. It contributes to climate change through CO2 and non-CO2 effects, including contrail-cirrus and ozone formation. There is currently significant interest in policies, regulations and research aiming to reduce aviation’s climate impact. Here we model the effect of these measures on global warming and perform a bottom-up analysis of potential technical improvements, challenging the assumptions of the targets for the sector with a number of scenarios up to 2100. We show that although the emissions targets for aviation are in line with the overall goals of the Paris Agreement, there is a high likelihood that the climate impact of aviation will not meet these goals. Our assessment includes feasible technological advancements and the availability of sustainable aviation fuels. This conclusion is robust for several COVID-19 recovery scenarios, including changes in travel behaviour.
|
|
