A group of aerospace technology companies have formed "a collaborative consortium to develop hybrid-electric and water-enhanced turbofan technology for future aircraft propulsion systems" under the Clean Aviation project, a public-private partnership between the European Commission, the aerospace industry, and research institutes.
Members of the new consortium are MTU Aero Engines (MTU), the co-ordinator, as well as Pratt & Whitney, Collins Aerospace (Collins), GKN Aerospace and Airbus. The aim, they said, is "to demonstrate the potential of these technologies to improve fuel efficiency and reduce aircraft CO2 emissions by up to 25% compared to today's state-of-the-art propulsion systems for short- and medium-range aircraft".
The Sustainable Water-Injecting Turbofan Comprising Hybrid-Electrics (SWITCH) project is focused on developing a novel propulsion concept built from two synergetic technologies: Water-Enhanced Turbofan (WET) and hybrid-electric propulsion. By combining these technologies with Pratt & Whitney’s GTF engine architecture, the SWITCH concept aims to significantly enhance efficiency and substantially reduce emissions across the full operating envelope of an aircraft. Technologies developed as part of SWITCH are promised to be fully compatible with cleaner alternative fuels – such as Sustainable Aviation Fuel (SAF) — and the team notes "will be evaluated for future use with hydrogen".
“This highly impactful SWITCH consortium provides a unique opportunity to demonstrate the benefits of both WET and hybrid-electric propulsion technologies, not only independently but as parts of a system,” said Dr. Stefan Weber, senior vice president, engineering and technology at MTU.
The hybrid-electric GTF powertrain will enable even greater efficiency across all phases of flight by leveraging highly efficient megawatt class electric motor generators, power electronics, and batteries to optimise the performance of the fuel-burning gas turbine. The WET concept recovers water vapor from the engine exhaust and re-injects it into the combustion chamber to significantly improve fuel efficiency, reduce NOx emissions, and lessen contrail forming emissions. These revolutionary technologies are designed to work together to deliver a step change reduction in emissions and energy use across the full operating system, while maintaining world class reliability and operability.
“New propulsion technologies will play an important role in achieving aviation's net-zero goals, along with new aircraft designs and sustainable energy sources,” said Sabine Klauke, chief technology officer at Airbus.
Airbus will provide key expertise relating to the future integration of SWITCH technologies at the aircraft-level and will support the evaluation of performance benefits including aircraft design and integration of battery and energy management systems. Collins will provide megawatt-class electric motor generators and power electronics, high-voltage DC distribution and protection, thermal management components and nacelle architectures for the project. GKN Aerospace will develop various engine structures with all-new functionalities, such as integrated electric machines and heat exchangers.
Other participants include Aristotle University of Thessaloniki, Chalmers University of Technology in Sweden, the DLR German Aerospace Center and the University of Stuttgart.
Current funding for Phase 1 of SWITCH extends to 2025 and will include testing of a hybrid-electric GTF engine, WET technology and sub-system laboratory testing, and design activity around an integrated hybrid-electric and WET cycle propulsion system. Subject to successful testing of these key technologies and component designs, further phases of ground testing and flight tests are expected to follow.