Special Issue "Climate Impact of Aviation"

A special issue of Applied Sciences (ISSN 2076-3417). This special issue belongs to the section "Aerospace Science and Engineering".

Deadline for manuscript submissions: 20 May 2023 | Viewed by 4461

Special Issue Editor

Dr. Florian Linke
E-Mail Website
Guest Editor
German Aerospace Center, Air Transportation Systems, 21079 Hamburg, Germany
Interests: climate impact of aviation; environmental assessment; air transport concepts; operational mitigation measures; non-CO2 effects; emission inventories

Special Issue Information

Dear Colleagues,

This Special Issue is devoted to research on the climate impact of aviation. It provides a publication framework for applied studies combining various disciplines to investigate how the future climate is affected by developments in air transportation. Such developments could, for example, be based on forecasts on the growth in air travel demand and flight movements including projected route network changes in the future as well as technology improvement scenarios. Detailed impact assessment of new overall aircraft designs and technologies including aircraft subsystems as well as new propulsion concepts and alternative energy carriers also perfectly fit within the scope of this Special Issue. Similarly, studies on new operational measures and policy-driven approaches or market-based measures are welcome. Papers in this Special Issue should include quantitative climate impact assessments including the non-CO2 effects of aviation (e.g. caused by emissions of nitrogen oxides or the formation of contrail cirrus). Submitted papers should be interdisciplinary and include elements from atmospheric physics/chemistry on the one hand and aviation-related subjects from, for example, aeronautical engineering, aviation management or operations research on the other. While the focus should be on the application of established methods, particular enhancements of existing methodologies or new methods tailored to enable the assessment of aviation’s climate impact could also be addressed in papers in this Special Issue.

In this Special Issue, we invite submissions exploring cutting-edge research and recent advances in our understanding of the Climate Impact of Aviation. Both theoretical and experimental studies are welcome, as well as comprehensive review and survey papers.

Dr. Florian Linke
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Applied Sciences is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2300 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • climate impact
  • aviation
  • impact assessment
  • gaseous emissions
  • mitigation measures
  • non-CO2 effects
  • contrail cirrus
  • aircraft technology
  • sustainable aviation fuel
  • flight operations

Published Papers (6 papers)

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Research

Article
Climate-Optimised Intermediate Stop Operations: Mitigation Potential and Differences from Fuel-Optimised Configuration
Appl. Sci. 2022, 12(23), 12499; https://doi.org/10.3390/app122312499 - 06 Dec 2022
Viewed by 183
Abstract
Saving fuel by splitting a flight mission with an intermediate stop for refuelling is described by the concept of intermediate stop operations. This can also be beneficial to the climate impact of aviation, if the flight level and intermediate stop airport are selected [...] Read more.
Saving fuel by splitting a flight mission with an intermediate stop for refuelling is described by the concept of intermediate stop operations. This can also be beneficial to the climate impact of aviation, if the flight level and intermediate stop airport are selected accordingly. This study aims to estimate the mitigation potential of an implementation of climate-optimised intermediate stop operations for European long-haul flights and compare it to fuel-optimal operations. For this purpose, fuel consumption and emissions are simulated along four-dimensional trajectories for the selected annual flight plan, and their average temperature response is calculated. A comparison between the reference case and climate-optimised as well as fuel-optimised scenarios shows a significant climate mitigation potential and reveals a shift of trajectories to lower latitudes and altitudes. However, increased flight times and fuel consumption limit implementation from stakeholders’ perspectives. Full article
(This article belongs to the Special Issue Climate Impact of Aviation)
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Article
The Water-Enhanced Turbofan as Enabler for Climate-Neutral Aviation
Appl. Sci. 2022, 12(23), 12431; https://doi.org/10.3390/app122312431 - 05 Dec 2022
Viewed by 475
Abstract
A significant part of the current aviation climate impact is caused by non-carbon-dioxide emissions, mainly nitrogen oxides (NOx) and contrails. It is, therefore, important to have a holistic view on climate metrics. Today’s conventional, but already well-developed, aero-engines are based on [...] Read more.
A significant part of the current aviation climate impact is caused by non-carbon-dioxide emissions, mainly nitrogen oxides (NOx) and contrails. It is, therefore, important to have a holistic view on climate metrics. Today’s conventional, but already well-developed, aero-engines are based on the Joule–Brayton cycle, and leave only limited room for improvement in climate impact. The revolutionary Water-Enhanced Turbofan (WET) concept represents a technical step change addressing all relevant emissions by implementing the Cheng cycle, which combines the gas turbine cycle with a Clausius–Rankine steam cycle. This paper builds upon previous publications regarding the WET concept, and outlines the evolution since then. Promising WET configurations are evaluated according to their ability to reduce global warming potential compared to an evolutionarily advanced turbofan engine. A quantitative approach to estimate reduction of NOx emissions through steam injection is presented. The impact on the creation of contrails is considered using the Schmidt-Appleman criterion. In conclusion, all three climate-relevant emissions can be reduced with the WET concept compared to a technologically similar turbofan in terms of CO2 (up to 10%), NOx (more than 90%), and contrails (more than 50%). The resulting in-flight climate impact can be reduced by more than 40% when using fossil kerosene, paving the way to climate-neutral aviation. Full article
(This article belongs to the Special Issue Climate Impact of Aviation)
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Article
CORSIA—A Feasible Second Best Solution?
Appl. Sci. 2022, 12(14), 7054; https://doi.org/10.3390/app12147054 - 13 Jul 2022
Cited by 1 | Viewed by 716
Abstract
This paper studies the feasibility of CORSIA’s carbon neutral growth goal based on verified carbon offsetting. It is motivated by an ongoing general debate about the climate and regulatory integrity of carbon offsetting, thus systematically identifying critical carbon offset characteristics. Using registry data [...] Read more.
This paper studies the feasibility of CORSIA’s carbon neutral growth goal based on verified carbon offsetting. It is motivated by an ongoing general debate about the climate and regulatory integrity of carbon offsetting, thus systematically identifying critical carbon offset characteristics. Using registry data from the largest carbon offset verifiers eligible under CORSIA, we show that the majority of carbon offsets have minor climate integrity. This challenges CORSIA’s neutral growth objective. However, unconditional offset price differentials are only weak signals for climate integrity. To increase environmental effectiveness, a narrower scope of eligibility rules is necessary in order to ensure maximum compliance of projects and strengthen the necessary price effect of carbon offsets. However, it is highly questionable whether there is enough potential supply of offsets to ensure such high integrity, indicating that carbon offsetting should be considered as a transitory measure only. Full article
(This article belongs to the Special Issue Climate Impact of Aviation)
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Article
A Parametric Approach for Conceptual Integration and Performance Studies of Liquid Hydrogen Short–Medium Range Aircraft
Appl. Sci. 2022, 12(14), 6857; https://doi.org/10.3390/app12146857 - 06 Jul 2022
Viewed by 644
Abstract
The present paper deals with the investigation, at conceptual level, of the performance of short–medium-range aircraft with hydrogen propulsion. The attention is focused on the relationship between figures of merit related to transport capability, such as passenger capacity and flight range, and the [...] Read more.
The present paper deals with the investigation, at conceptual level, of the performance of short–medium-range aircraft with hydrogen propulsion. The attention is focused on the relationship between figures of merit related to transport capability, such as passenger capacity and flight range, and the parameters which drive the design of liquid hydrogen tanks and their integration with a given aircraft geometry. The reference aircraft chosen for such purpose is a box-wing short–medium-range airplane, the object of study within a previous European research project called PARSIFAL, capable of cutting the fuel consumption per passenger-kilometre up to 22%. By adopting a retrofitting approach, non-integral pressure vessels are sized to fit into the fuselage of the reference aircraft, under the assumption that the main aerodynamic, flight mechanic, and structural characteristics are not affected. A parametric model is introduced to generate a wide variety of fuselage-tank cross-section layouts, from a single tank with the maximum diameter compatible with a catwalk corridor to multiple tanks located in the cargo deck, and an assessment workflow is implemented to perform the structural sizing of the tanks and analyse their thermodynamic behaviour during the mission. This latter is simulated with a time-marching approach that couples the fuel request from engines with the thermodynamics of the hydrogen in the tanks, which is constantly subject to evaporation and, depending on the internal pressure, vented-out in gas form. Each model is presented in detail in the paper and results are provided through sensitivity analyses to both the technologic parameters of the tanks and the geometric parameters influencing their integration. The guidelines resulting from the analyses indicate that light materials, such as the aluminium alloy AA2219 for tanks’ structures and polystyrene foam for the insulation, should be selected. Preferred values are also indicted for the aspect ratios of the vessel components, i.e., central tube and endcaps, as well as suggestions for the integration layout to be adopted depending on the desired trade-off between passenger capacity, as for the case of multiple tanks in the cargo deck, and achievable flight ranges, as for the single tank in the section. Full article
(This article belongs to the Special Issue Climate Impact of Aviation)
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Article
Climate Impact Reduction Potentials of Synthetic Kerosene and Green Hydrogen Powered Mid-Range Aircraft Concepts
Appl. Sci. 2022, 12(12), 5950; https://doi.org/10.3390/app12125950 - 11 Jun 2022
Viewed by 835
Abstract
One of aviation’s major challenges for the upcoming decades is the reduction in its climate impact. As synthetic kerosene and green hydrogen are two promising candidates, their potentials in decreasing the climate impact is investigated for the mid-range segment. Evolutionary advancements for 2040 [...] Read more.
One of aviation’s major challenges for the upcoming decades is the reduction in its climate impact. As synthetic kerosene and green hydrogen are two promising candidates, their potentials in decreasing the climate impact is investigated for the mid-range segment. Evolutionary advancements for 2040 are applied, first with an conventional and second with an advanced low-NOx and low-soot combustion chamber. Experts and methods from all relevant disciplines are involved, starting from combustion, turbofan engine, overall aircraft design, fleet level, and climate impact assessment, allowing a sophisticated and holistic evaluation. The main takeaway is that both energy carriers have the potential to strongly reduce the fleet level climate impact by more than 75% compared with the reference. Applying a flight-level constraint of 290 and a cruise Mach number of 0.75, causing 5% higher average Direct Operating Costs (DOC), the reduction is even more than 85%. The main levers to achieve this are the advanced combustion chamber, an efficient contrail avoidance strategy, in this case a pure flight-level constraint, and the use of CO2 neutral energy carrier, in a descending priority order. Although vehicle efficiency gains only lead to rather low impact reduction, they are very important to compensate the increased costs of synthetic fuels or green hydrogen. Full article
(This article belongs to the Special Issue Climate Impact of Aviation)
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Article
Meteorological Conditions That Promote Persistent Contrails
Appl. Sci. 2022, 12(9), 4450; https://doi.org/10.3390/app12094450 - 28 Apr 2022
Cited by 1 | Viewed by 875
Abstract
Climate-impacting contrails need ice (super-)saturation to persist longer than a few minutes. However, this simple criterion cannot be easily applied for the prediction of persistent contrails. The current weather forecast models, which lack humidity data for assimilation in the upper troposphere, have difficulties [...] Read more.
Climate-impacting contrails need ice (super-)saturation to persist longer than a few minutes. However, this simple criterion cannot be easily applied for the prediction of persistent contrails. The current weather forecast models, which lack humidity data for assimilation in the upper troposphere, have difficulties coping with the enormous variability and sharp gradients in the relative humidity field. Thus, ice supersaturation, which is an extremal state of relative humidity, is hard to forecast at a precise location and time to allow contrail-avoiding flight routing. In this paper, we investigate the possibility of using dynamical proxy variables for improved contrail prediction. This idea is guided by the fact that the probability of ice supersaturation differs in different dynamical regimes. Therefore, we determine probability distributions of temperature, water vapour concentration, vertical velocity, divergence, relative and potential vorticity, geopotential height, and lapse rate conditioned on three situations: (a) contrail persistence not possible; (b) contrail persistence possible; and (c) strongly warming persistent contrails possible. While the atmospheric variables are taken from reanalysis data, the conditions (a–c) are based on airborne measurement data and radiation quantities from the reanalysis. It turns out that the vorticity variables, and in particular geopotential and lapse rate, show quite distinct conditional probabilities, suggesting a possibility to base an improved forecast of persistent contrails not only on the traditional quantities of temperature and relative humidity, but on these dynamical proxies as well. Furthermore, we show the existence of long flight tracks with the formation of strongly warming contrails, which are probably embedded in larger ice-supersaturated regions with conditions that foster such contrails. For forecasting purposes, this is a beneficial property since the humidity forecast is easier on large, rather than small, spatial scales. Full article
(This article belongs to the Special Issue Climate Impact of Aviation)
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Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

Title: The Water-Enhanced Turbofan as Enabler for a Climate-Friendly Aviation
Authors: Sascha Kaiser; Oliver Schmitz; Paul Ziegler; Hermann Klingels
Affiliation: MTU Aero Engines AG, Dachauer Str. 665, 80995 Munich, Germany
Abstract: A significant part of the current aviation climate impact is caused by non-carbon-dioxide emis-sions, mainly nitrogen oxides (NOx) and contrails. It is therefore important to have a holistic view on climate metrics. Today’s conventional but already well-developed aero-engines based on the Joule-/Brayton cycle leave only little room for improvement in climate impact. The revolutionary Water-Enhanced Turbofan (WET) concept represents a technical step change addressing all rele-vant emissions by implementing the Cheng cycle, which combines the gas turbine cycle with a Clausius-Rankine steam cycle. This paper builds upon previous publications about the WET con-cept and outlines the evolution since then. Promising WET configurations are evaluated regarding their ability to reduce global warming potential compared to an evolutionarily advanced turbofan engine. A quantitative approach to estimate reduction of NOx emissions through steam injection is presented. Ongoing scientific activities including experiments are presented and an outlook on upcoming steps is given.

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