Environmental Impacts of Future Aviation Propulsion Systems
Aviation is an integral part of modern society and economy. A fundamental challenge facing the aviation sector in the coming decades is to enable the 3.8% projected growth in air traffic per year and the associated benefits while simultaneously reducing aviation’s impact on the environment in terms...
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| Format: | Thesis |
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Massachusetts Institute of Technology
2023
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| Online Access: | https://hdl.handle.net/1721.1/150129 https://orcid.org/0000-0002-2346-0697 |
| _version_ | 1811087367329546240 |
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| author | Prashanth, Prakash |
| author2 | Barrett, Steven R.H. |
| author_facet | Barrett, Steven R.H. Prashanth, Prakash |
| author_sort | Prashanth, Prakash |
| collection | MIT |
| description | Aviation is an integral part of modern society and economy. A fundamental challenge facing the aviation sector in the coming decades is to enable the 3.8% projected growth in air traffic per year and the associated benefits while simultaneously reducing aviation’s impact on the environment in terms of air quality and climate. This thesis improves the scientific understanding of the atmospheric impacts attributable to aviation gas turbine emissions and the means of mitigating them with a focus on the propulsion system. Specifically, this thesis addresses aspects of 1) aerosol formation from aviation-attributable NOx and SOx, 2) the technical extent to which the air quality and climate impacts of aviation can be minimized, and 3) how propulsion system design for supersonic commercial aircraft in the future would impact the environment.
I first address how emissions of aerosol precursors species – NOx and SOx from aircraft gas turbine engines – results in aerosol formation. I quantify the contribution of the different pathways to the formation of secondary inorganic aerosol and their associated impact on radiative forcing and population exposure to pollutants at the surface. A key finding is that 47% of the aviation NOx emissions-attributable aerosol RF is due to sulfate aerosol formed through the NOx-sulfate pathway where, aviation-attributable oxidants derived from aviation NOx emissions result in the oxidation of SOx emissions to sulfate aerosol. Moreover, 88% of this sulfate related RF through the NOx-sulfate pathway is due to the oxidation of non-aviation SOx, highlighting the coupling between aviation and non-aviation emissions. Furthermore, I show that aviation emissions of NOx are responsible for ~95% of aviation-attributable population exposure to particulate matter (PM2.5) and ozone.
I then undertake the notional design of an aircraft system to assess whether it is technically feasible to have an aircraft system with net-zero climate impact and >95% reduction in air quality impacts relative to the present. The identified system relies on (1) an aviation fuel with low lifecycle greenhouse gas (GHG) emissions; (2) an aircraft design which accommodates post-combustion emissions control devices to enable a 96% reduction in emissions of NOx; (3) operational strategies for contrail avoidance; and (4) atmospheric CO2 removal with geological storage at small scale (1% of geological storage potential) to address GHG emissions which are otherwise prohibitively expensive to avoid. The proposed system reduces the combined climate and air quality impacts by 99% for a 16-22% increase in direct operating costs (excluding invested capital costs of aircraft and required infrastructure).
I then consider the environmental impacts that may arise from the addition of new capability in the form of commercial supersonic transport (SST) to the current system. Prior development of propulsion systems for SSTs have relied on derivative engines. I quantify the impact that constraints imposed by such a derivative engine design have on its performance relative to a clean-sheet design. Accounting for technology improvements, the clean-sheet design results in a 4% lower SFC than the derivative engine, with the SFC improvements being most sensitive to the ability to design low-NOx combustors followed by turbomachinery efficiency. A fleet of 140 supersonic business jets using the derivative or clean-sheet engines result in ~13 mDU of column ozone depletion per billion available seat-kilometers in 2035. |
| first_indexed | 2024-09-23T13:44:58Z |
| format | Thesis |
| id | mit-1721.1/150129 |
| institution | Massachusetts Institute of Technology |
| last_indexed | 2024-09-23T13:44:58Z |
| publishDate | 2023 |
| publisher | Massachusetts Institute of Technology |
| record_format | dspace |
| spelling | mit-1721.1/1501292023-04-01T03:26:58Z Environmental Impacts of Future Aviation Propulsion Systems Prashanth, Prakash Barrett, Steven R.H. Massachusetts Institute of Technology. Department of Aeronautics and Astronautics Aviation is an integral part of modern society and economy. A fundamental challenge facing the aviation sector in the coming decades is to enable the 3.8% projected growth in air traffic per year and the associated benefits while simultaneously reducing aviation’s impact on the environment in terms of air quality and climate. This thesis improves the scientific understanding of the atmospheric impacts attributable to aviation gas turbine emissions and the means of mitigating them with a focus on the propulsion system. Specifically, this thesis addresses aspects of 1) aerosol formation from aviation-attributable NOx and SOx, 2) the technical extent to which the air quality and climate impacts of aviation can be minimized, and 3) how propulsion system design for supersonic commercial aircraft in the future would impact the environment. I first address how emissions of aerosol precursors species – NOx and SOx from aircraft gas turbine engines – results in aerosol formation. I quantify the contribution of the different pathways to the formation of secondary inorganic aerosol and their associated impact on radiative forcing and population exposure to pollutants at the surface. A key finding is that 47% of the aviation NOx emissions-attributable aerosol RF is due to sulfate aerosol formed through the NOx-sulfate pathway where, aviation-attributable oxidants derived from aviation NOx emissions result in the oxidation of SOx emissions to sulfate aerosol. Moreover, 88% of this sulfate related RF through the NOx-sulfate pathway is due to the oxidation of non-aviation SOx, highlighting the coupling between aviation and non-aviation emissions. Furthermore, I show that aviation emissions of NOx are responsible for ~95% of aviation-attributable population exposure to particulate matter (PM2.5) and ozone. I then undertake the notional design of an aircraft system to assess whether it is technically feasible to have an aircraft system with net-zero climate impact and >95% reduction in air quality impacts relative to the present. The identified system relies on (1) an aviation fuel with low lifecycle greenhouse gas (GHG) emissions; (2) an aircraft design which accommodates post-combustion emissions control devices to enable a 96% reduction in emissions of NOx; (3) operational strategies for contrail avoidance; and (4) atmospheric CO2 removal with geological storage at small scale (1% of geological storage potential) to address GHG emissions which are otherwise prohibitively expensive to avoid. The proposed system reduces the combined climate and air quality impacts by 99% for a 16-22% increase in direct operating costs (excluding invested capital costs of aircraft and required infrastructure). I then consider the environmental impacts that may arise from the addition of new capability in the form of commercial supersonic transport (SST) to the current system. Prior development of propulsion systems for SSTs have relied on derivative engines. I quantify the impact that constraints imposed by such a derivative engine design have on its performance relative to a clean-sheet design. Accounting for technology improvements, the clean-sheet design results in a 4% lower SFC than the derivative engine, with the SFC improvements being most sensitive to the ability to design low-NOx combustors followed by turbomachinery efficiency. A fleet of 140 supersonic business jets using the derivative or clean-sheet engines result in ~13 mDU of column ozone depletion per billion available seat-kilometers in 2035. Ph.D. 2023-03-31T14:34:29Z 2023-03-31T14:34:29Z 2023-02 2023-02-15T14:05:39.493Z Thesis https://hdl.handle.net/1721.1/150129 https://orcid.org/0000-0002-2346-0697 In Copyright - Educational Use Permitted Copyright MIT http://rightsstatements.org/page/InC-EDU/1.0/ application/pdf Massachusetts Institute of Technology |
| spellingShingle | Prashanth, Prakash Environmental Impacts of Future Aviation Propulsion Systems |
| title | Environmental Impacts of Future Aviation Propulsion Systems |
| title_full | Environmental Impacts of Future Aviation Propulsion Systems |
| title_fullStr | Environmental Impacts of Future Aviation Propulsion Systems |
| title_full_unstemmed | Environmental Impacts of Future Aviation Propulsion Systems |
| title_short | Environmental Impacts of Future Aviation Propulsion Systems |
| title_sort | environmental impacts of future aviation propulsion systems |
| url | https://hdl.handle.net/1721.1/150129 https://orcid.org/0000-0002-2346-0697 |
| work_keys_str_mv | AT prashanthprakash environmentalimpactsoffutureaviationpropulsionsystems |