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Shape Adaptive Blades for Rotorcraft Efficiency

Periodic Reporting for period 3 - SABRE (Shape Adaptive Blades for Rotorcraft Efficiency)

Reporting period: 2020-06-01 to 2021-05-31

Shape Adaptive Blades for Rotorcraft Efficiency (SABRE) is an H2020 funded research project which aims to develop ground-breaking new helicopter blade morphing technologies that will reduce helicopter fuel burn, CO2 and NOx emissions by a projected 5-10%, while also reducing noise emissions. As the aviation sector continues to grow and helicopters are increasingly used to perform a wide range of vital missions in our society, it is important that their environmental impact be minimised. This goal is particularly important in light of the Europe-wide push towards a more environmentally conscious society. The morphing blade technologies developed within SABRE will help Europe to achieve its ambitious aviation emissions goals while also sharpening its competitive edge in the rapidly growing helicopter market. It has support from leading industry figures, Airbus Helicopters and Leonardo Helicopters.

The two primary objectives of the SABRE research program are to develop a range of different morphing concepts which all have significant promise for emissions reductions while also quantifying the potential helicopter emissions reductions achievable through their use. These dual research streams are tightly cross-linked, with the morphing technology development directly informing the rotor level analysis of what the performance achievable, while the rotor level analysis also feeds back where and how to best use the morphing devices to maximise the emissions reductions. Only in this way can the tightly coupled questions of "what is the best way to use morphing rotors?" and "what can the morphing technologies achieve?" be answered. Our consortium brings together world leading experts in both rotorcraft analysis and morphing technology development and SABRE has been carefully structured to allow for genuinely collaborative research between them to answer these questions.
Over the duration of the SABRE project, major progress was made towards achieving the objectives of this program. The partners employed sophisticated analysis tools, which were further enhanced in this project with significant improvements to their coding and accuracy, to fully explore the design space of morphing rotors. Comprehensive analysis runs on the refined surrogate models of the different morphing concepts have shown that including detailed analysis results of the morphing concept performance into system level analysis of the power requirements and emissions of the full helicopter gives the most complete picture to date of what is achievable. Happily, our initial lower fidelity estimates which showed reductions in CO2 and NOx on the order of 5-10% have been born out by our more detailed analysis, which is currently showing 5-11% reductions, depending on the flight mode and the combination of morphing concepts used. What’s more, the depth of the technical considerations expanded significantly in the final stages of the project, with important aspects of rotor vibrations and acoustic emissions now being included. These additional analyses are important for considering the real world implications of morphing rotors, and are a key consideration before any of these technologies can be commercialised. Crucially, no show-stoppers have been identified in the acoustic and vibration analysis done to date. In fact, we have found that careful usage of the morphing devices can lead to reductions in both acoustic emissions and helicopter vibration levels.

The progress made throughout the SABRE program has also gone a long way towards advancing the maturity of the morphing technologies, supporting our second program objective. While progress on the design and experimental aspects of Work Package 2 was affected by the global pandemic, an adaptive research strategy was employed which allowed us to focus on realising the key experimental wind tunnel and whirl tower tests, while supporting this work with benchtop testing of subsystems and components along with enhanced numerical simulations. These tests showed the morphing concepts can withstand aerodynamic and centrifugal loading, with the desired levels of direct control of lift being validated in the wind tunnel.

While morphing rotor blade technologies still need further development before they are ready for industrial adoption, our work in SABRE has shown, in the most comprehensive and integrated way, that they are indeed worth pursuing, with achievable reductions in emissions that are far beyond what is achievable with traditional rotor design.
This project has lead to significant advancements in the state-of-the-art of morphing and adaptive helicopter rotors. The technology development work is significantly beyond the state of the art, and significant improvements have also been made in the automation, fidelity, and sophistication of the rotorcraft analysis tools available to and developed by the partners. This project has a unique focus on rotorcraft emissions (as opposed to vibration, or performance), and models have been created which will allow for other researchers to adopt a similar focus for their work. The technologies developed are showing good promise in terms of efficacy, and while there are still technological challenges to come, no major show stoppers have been identified. This project has also forged a strong collaborative relationship between the partner institutions, with clear leadership and a focused approach to achieving our goals. The methods, tools, and technologies developed will be available to advance the vision of greener aviation, and to improve the economy, environment, and research atmosphere of the European community.
SABRE poster 1
SABRE leaflet 1, front page
SABRE logo and background image