AcouStic integration for futuRe Aircraft propuLsion – ASTRAL
Acoustic Integration for Future Aircraft Propulsion
Development of innovative acoustic materials designed for the constraints of future aircraft engine architectures
Absorbing low-frequency noise with small acoustic treatments
The overall aim of this project is to the development of novel acoustic treatments that can be installed on future architectures of aircraft engines to support the reduction of aviation noise emissions. To this end it is necessary to tackle a number of scientific challenges such as the interactions between sound, liner and flow, the analysis and manufacturing of porous materials and metamaterials, and also experimental techniques for liner characterisation. The project sets out a work programme designed to achieve the following specific objectives:<br />1. Develop a number of breakthrough low-noise technologies including: 3d-printed porous materials and metamaterials able to operate in aircraft engines, active noise control systems, acoustic panels for noise and vibration.<br />2. Gain new insight into the interaction between an acoustic treatment and its environment, such as the grazing flow and the strong sound field. A particular focus is given on aerodynamic drag induced by the liner, but also on the effect of the boundary layer on the liner.<br />3. Develop advanced and integrated models able to describe the propagation of sound in complex environments including: curved lined ducts, with non-uniform, swirling flow and non-linear propagation. This is required to provide accurate predictions of the sound field in modern and future aircraft engines.<br />4. Develop advanced measurement techniques able to characterize the acoustic and aerodynamic behaviours of liners in the presence of flow and complex sound fields.<br />5. Maximize knowledge transfer between LAUM and SAFRAN, as well dissemination actions and training events geared towards the scientific and industrial communities.
The Industrial Chair is divided into a number of scientific and technological Work Packages:
1. Advanced modelling techniques will be developed to predict the propagation of sound in turbofan engines. This includes effects such as non-linear propagation, swirling flows and propagation in short ducts. Coupling these propagation models with noise source models will also be considered.
2. Novel experimental techniques will be designed to allow for detailed characterisation of acoustic treatments with flow, high sound pressure levels and complex sound fields. These conditions are representative of the environment found on aircraft engines.
3. A range of advanced passive materials will be developed to provide strong sound absorption at low frequency. This includes porous materials, meta-porous surfaces which involve periodic resonant inclusions, and metamaterials comprised of arrays of detuned resonators.
4. Novel active treatments will be further improved to operate on aircraft engines. A first approach will be micro-electromechanical transducers able to absorb sound at low frequencies. Another approach is the use of pneumatic noise sources to control the sound field.
5. A particular focus will be on the interaction between an acoustic treatment and its environment, in particular the effect of the flow over the liner. This will include the impact of grazing flow on porous liners. Another important topic will be the aerodynamic drag generated by the perforated liners.
6. WP6 is designed to explore a range of new directions by performing early-stage research on TRL1 concepts.
7. Dissemination and exploitation activities will be conducted to publicise the results of the project, and to maximise the uptake by industries of the technologies developed in the project.
The main scientific outcomes of the project will be:
* New insight into the underlying physics of sound absorption by various types of acoustic treatments (porous materials, metamaterials, active control), and on the interactions between flow, sound and liners.
* Advanced modelling tools for the propagation and absorption of sound in turbofan engines.
The main technological benefits will be in the form of novel liner concepts, for a range of liner technologies including porous material, meta-materials with resonators, and different active noise control technologies. Successive rounds of design and tests will bring these concepts to TRL2 and TRL3.
A strong emphasis will be put on the potential integration of these technologies on future UHBR architectures. In addition, the analyses and tests performed during the project will help develop the best engineering practices needed for the design and installation of these liners on future aircraft engines.
The main economic impact will be the increased competitiveness of the turbofan engines and nacelles designed by SAFRAN, which will be quantified by reductions in noise emissions and aerodynamic drag. These are crucial factors for the successful commercialisation of new products in this sector, such as the future CFM engines designed by SAFRAN in partnership with General Electrics.
The scientific results of the project will be published in international journals and conferences. The technical developments will be protected in the form of joint patents between the laboratory and the Safran group.
Noise emissions from commercial air transport is a crucial issue in relation to public health, economic competitiveness and technological developments. For instance, the Strategy Research and Innovation Agenda, recently released by the Advisory Council for Aeronautical Research in Europe, has defined the vision for the reduction of aviation noise in 2050 in Europe. This sets out a number of ambitious targets for the reduction of noise and air pollution, including a 65% reduction of perceived noise levels by 2050 compared to the year 2000. At the national level, the Conseil pour la Recherche Aéronautique Civile has defined similar targets.
The present project aims to develop novel acoustic treatments to significantly reduce noise emissions from aircraft. This is a collaborative effort between the SAFRAN Group and the Laboratoire d’Acoustique de l’Université du Mans (LAUM). Their combined expertise in fundamental research and technology innovation in acoustics will enable the development of novel acoustic treatments that can be efficiently integrated onto future engine architectures.
A number of research directions will be considered in this project.
* The interactions between the acoustic treatment, the sound field and the air flow. In particular the impact of a perforate liner on aerodynamic losses will be investigated.
* Novel experimental techniques will be developed to assess the performance of acoustic treatments with flow, high sound levels and complex sound fields.
* Models will be developed to predict the effects of non-linear sound propagation and swirling flows on liner performance.
* New liner technologies will be developed, including porous material, metamaterials and active noise control.
In addition to these research and development activities, the project will also contribute to technology transfer, training events and dissemination.
Project coordination
Gwénaël GABARD (LABORATOIRE D'ACOUSTIQUE DE L'UNIVERSITE DU MANS)
The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.
Partner
LAUM LABORATOIRE D'ACOUSTIQUE DE L'UNIVERSITE DU MANS
Help of the ANR 690,120 euros
Beginning and duration of the scientific project:
May 2021
- 48 Months
