Periodic Reporting for period 2 - MINIMAL (Minimum environmental impact ultra-efficient cores for aircraft propulsion.)
Período documentado: 2024-03-01 hasta 2025-08-31
MINIMAL aims at providing aircraft propulsion systems that can support the transition to climate-neutrality by year 2050. This is achieved by combining the expertise of propulsion engineers and climate scientists in a holistic framework that investigates technology with the potential to attack the major sources of CO2 and non-CO2 emissions in aeroengines. The targets set in MINIMAL are (in relation to 2020 technology):
• to reduce emissions from contrail cirrus by 80%,
• to reduce net-NOx by 52%,
• to improve energy efficiency by 36%.
New propulsion systems fueled by hydrogen or sustainable aviation fuel (SAF), and using composite cycle engine (CCE) technology, will offer unparalleled thermal efficiency and performance flexibility for climate-friendly operations. The end goal is to identify the engine design options giving minimal climate impact. Three competing engine concepts are currently being investigated:
• Turbofan with an intercooled crankshaft topping core,
• Turbofan with an intercooled opposed free piston topping core,
• Turbofan with an intercooled dual free piston topping core.
MINIMAL also targets the experimental (TRL3) proof of concept of cutting-edge technologies enabled by liquid hydrogen fuel:
• opposed-piston low-NOx hydrogen combustion,
• heat-management systems that exploit the cooling potential of hydrogen.
• to reduce emissions from contrail cirrus by 80%,
• to reduce net-NOx by 52%,
• to improve energy efficiency by 36%.
New propulsion systems fueled by hydrogen or sustainable aviation fuel (SAF), and using composite cycle engine (CCE) technology, will offer unparalleled thermal efficiency and performance flexibility for climate-friendly operations. The end goal is to identify the engine design options giving minimal climate impact. Three competing engine concepts are currently being investigated:
• Turbofan with an intercooled crankshaft topping core,
• Turbofan with an intercooled opposed free piston topping core,
• Turbofan with an intercooled dual free piston topping core.
MINIMAL also targets the experimental (TRL3) proof of concept of cutting-edge technologies enabled by liquid hydrogen fuel:
• opposed-piston low-NOx hydrogen combustion,
• heat-management systems that exploit the cooling potential of hydrogen.
The work started with the definition of the technological assumptions for year 2035, followed by the definition of the reference 2020 and baseline 2035 TRL6 engines. The baseline engines were developed for short-, medium-, and long-range applications and are based on geared turbofan architectures featuring low-NOx combustion systems. Additionally, the short-range engine is based on a hydrogen recuperative cycle. In parallel, aircraft models for entry into service at year 2040 were developed for each one of the aforementioned engines. For a comprehensive evaluation of the global fuel consumption impact of MINIMAL technology, aircraft fleet models were developed for a number of techno-economic and social scenarios up to year 2050. This supported the creation of reference year 2019 and baseline year 2050 emission inventories that were used to estimate the climate impact from aviation using baseline (conventional) technology. Finally, the inventories were used to create climate response functions that estimate global temperature variations as a function of emission species at the engine exhaust. These can be directly employed into the engine design optimisation loops, allowing to optimise each one of the CCE configurations for minimum climate impact.
The maturation of intercooled CCE technologies to TRL2 is progressing well. Models have been created at the component and system level, to predict the performance of all three topping cycles (crankshaft-based, free-dual, opposed), including hydrogen combustion models, and heat-transfer performance. Emission models for NOx have been integrated into the design loops allowing to investigate efficiency vs emission trades for varying design parameters. Additionally, NOx mitigation strategies such as exhaust gas recirculation (EGR), and steam injection, have been investigated showing promising NOx reduction potential. This work is supported by parallel studies ranging from 0D/1D to CFD modelling of thermal loads, secondary cooling flows, intake and exhaust manifold flows, as well as thermochemistry performance in combustion chambers. With the aim of developing the most effective cooling strategies for CCE concepts.
The down-selection of the novel hydrogen intercooler design is following the established plan and several TRL2 activities are ongoing, leading to the initial preliminary system design. Several piston cooling strategies are also currently being evaluated at TRL2. This work is supported by the creation of new or tailored heat-exchanger design tools. Regarding the low-NOx combustion rig, the activities were focused on the design and work towards the commission of the oppose-piston test facility. The project acquired a fully operational opposed piston assembly from Libertine, which has been instrumented for NOx and performance studies at Cranfield University. The rig will be located in a new combustion test facility that was design for usage during project MINIMAL. The new facility will be tailored for hydrogen combustion (PCCI and potentially HCCI) and aims at demonstrating low-NOx operation. To support the upcoming experimental activities different models with increased fidelity were developed. The models range from simple spreadsheet models to high-fidelity CFD and aim at predicting NOx formation at different operating modes. The models were further used to map out the anticipated performance of hydrogen powered operation to predict piston loads and develop motion control strategies.
The maturation of intercooled CCE technologies to TRL2 is progressing well. Models have been created at the component and system level, to predict the performance of all three topping cycles (crankshaft-based, free-dual, opposed), including hydrogen combustion models, and heat-transfer performance. Emission models for NOx have been integrated into the design loops allowing to investigate efficiency vs emission trades for varying design parameters. Additionally, NOx mitigation strategies such as exhaust gas recirculation (EGR), and steam injection, have been investigated showing promising NOx reduction potential. This work is supported by parallel studies ranging from 0D/1D to CFD modelling of thermal loads, secondary cooling flows, intake and exhaust manifold flows, as well as thermochemistry performance in combustion chambers. With the aim of developing the most effective cooling strategies for CCE concepts.
The down-selection of the novel hydrogen intercooler design is following the established plan and several TRL2 activities are ongoing, leading to the initial preliminary system design. Several piston cooling strategies are also currently being evaluated at TRL2. This work is supported by the creation of new or tailored heat-exchanger design tools. Regarding the low-NOx combustion rig, the activities were focused on the design and work towards the commission of the oppose-piston test facility. The project acquired a fully operational opposed piston assembly from Libertine, which has been instrumented for NOx and performance studies at Cranfield University. The rig will be located in a new combustion test facility that was design for usage during project MINIMAL. The new facility will be tailored for hydrogen combustion (PCCI and potentially HCCI) and aims at demonstrating low-NOx operation. To support the upcoming experimental activities different models with increased fidelity were developed. The models range from simple spreadsheet models to high-fidelity CFD and aim at predicting NOx formation at different operating modes. The models were further used to map out the anticipated performance of hydrogen powered operation to predict piston loads and develop motion control strategies.
The core work in MINIMAL revolves around two main research questions:
• “How can MINIMAL’s CCE technology contribute to a reduction in climate impact from aviation?”
• “Will that reduction be sufficient to address the climate goals set by the Paris Agreement?”
• “What are subsequent roadmaping steps for the realization of CCE technology?”
Hence the project focus has been on the development of new or tailored existing models to predict the system performance from a component level to an entire fleet of aircraft. The work led to the definition of reference and baseline technology scenarios as well as their global emission impact. This allowed for the establishment of different climate impact scenarios and the creation of climate response functions to be employed in the engine design optimization loops. Performance and emission results for the candidate technologies are underway and underline the importance of addressing both CO2 and non-CO2 emissions, in particular NOx, which is expected to increase with CCE engines if additional mitigation measures are not taken.
MINIMAL industrial partners have been instrumental in developing technology roadmaps to TRL6, where all MINIMAL technology development work is being reviewed in an attempt to identify system concepts and supporting component technologies. The activity will list development risks for integration of components with the engine and for the propulsion system with the aircraft.
Since start of the project, MINIMAL contributed with 25 conference presentations, 8 journal articles, 8 conference proceedings publications. MINIMAL also contributed to the recruitment of PhD, MSc students and young researchers, and ensure their visibility within European aviation stakeholders, their participation and active contribution to general assemblies, meetings, workshops and conferences.
• “How can MINIMAL’s CCE technology contribute to a reduction in climate impact from aviation?”
• “Will that reduction be sufficient to address the climate goals set by the Paris Agreement?”
• “What are subsequent roadmaping steps for the realization of CCE technology?”
Hence the project focus has been on the development of new or tailored existing models to predict the system performance from a component level to an entire fleet of aircraft. The work led to the definition of reference and baseline technology scenarios as well as their global emission impact. This allowed for the establishment of different climate impact scenarios and the creation of climate response functions to be employed in the engine design optimization loops. Performance and emission results for the candidate technologies are underway and underline the importance of addressing both CO2 and non-CO2 emissions, in particular NOx, which is expected to increase with CCE engines if additional mitigation measures are not taken.
MINIMAL industrial partners have been instrumental in developing technology roadmaps to TRL6, where all MINIMAL technology development work is being reviewed in an attempt to identify system concepts and supporting component technologies. The activity will list development risks for integration of components with the engine and for the propulsion system with the aircraft.
Since start of the project, MINIMAL contributed with 25 conference presentations, 8 journal articles, 8 conference proceedings publications. MINIMAL also contributed to the recruitment of PhD, MSc students and young researchers, and ensure their visibility within European aviation stakeholders, their participation and active contribution to general assemblies, meetings, workshops and conferences.