Core noIse Reduction foR Uhbr engineS

Project Information

CIRRUS

Grant agreement ID: 886554

DOI

10.3030/886554

Project closed

EC signature date 30 April 2020

Start date 1 July 2020

End date 31 December 2023

Funded under

• SOCIETAL CHALLENGES - Smart, Green And Integrated Transport

Total cost

€ 3 627 325,00

EU contribution

€ 2 731 877,50

Coordinated by

VIBRATEC
France

Periodic Reporting for period 3 - CIRRUS (Core noIse Reduction foR Uhbr engineS)

Reporting period: 2023-07-01 to 2023-12-31

Summary of the context and overall objectives of the project

The propulsion of the majority of commercial aircraft relies on turbofan engines. A gas turbine is used to drive the fan, which produces a significant part of the thrust. Modern turbofan designs rely on high bypass-ratios, meaning that most of the air flow goes through the bypass duct instead of entering the gas turbine. The current trend for future turbofan engines is towards even higher bypass ratios. These Ultra-High Bypass Ratio (UHBR) engines have large fans rotating at relatively low speeds. As a consequence of the lower fan speed, the fuel consumption can be reduced. Another consequence is that the engine noise signature is modified. The jet exhaust velocity is reduced and the jet noise is significantly decreased. Another benefit is that the low fan speed helps reduce the noise sources due to the fan. It is becoming urgent to tackle other noise sources on UHBR engines, specifically, the core noise generated by the combustion chambers and the turbine require particular attention since it is expected to become significant at certain operating conditions and strongly increased with the next UHBR 2030+ configuration where new clean combustor design and reduced LP turbine stages will be implemented.
The CIRRUS project aims to validate advanced low noise concepts, by developing both advanced numerical and experimental tools, to enable the reduction of the core noise in future UHBR 2030+ turbofan engines. The CIRRUS consortium is made of 5 partners covering a wide range of test and numerical expertise. The overall goals of CIRRUS are to:
• Improve numerical methods to predict the noise source mechanisms and the acoustic core noise radiation up to the far field.
• Improve experimental methods, including new pressure and thermal sensors, to measure the contribution of core noise on real engines.
• Develop, test and integration of new generations of noise reduction acoustic liners made of Ceramic Matrix Composites (CMC).
• Investigate, by comparing various turbine configurations of future UHBR 2030+ architectures, the influence on the core noise sources that reducing the number of stages achieves.

As main conclusions, the following observations can be highlighted:
• 3D simulation is a requirement to address core noise analysis,
• Acoustic efficiency of CMC technology for core liner is demonstrated by test and specified for a future application on UHBR architecture,
• Direct and indirect core noise source mechanisms have been experimentally identified and analysed; composition noise is found to be negligible.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

Over Period 1, the development of three main technologies has been started with first promising results :
• Core noise modelling : improvement of the physics, extension of the acoustic radiationn, resolution of the acoustic treatments
• Low noise solutions : technology screening and specifcation of Ceramix Matrix Composite acoustic liners and associated test campaigns
• Core noise measurements : first evaluation on synthetic data and identification of new methods, specification of test configuration

Over Period 2, all the technology developments have been achieved and qualified on various demonstrators:
• Core noise modelling : development of a new 3D workflow for core noise
o Application and validation of the modelling workflow on one engine configuration and comparison with measurements
o Development of 3D acoustic propagation simulation tool, to assess the impact of rotating parts on acoustic scattering.
o Validation of time domain acoustic liners model by comparing with experimental results.

• Low noise solutions :
o Development of an optimisation tool based on the mode-matching method
o Evaluation by test and manufacturing of a new generation of CMC liner for core noise reduction

• Core noise measurements :
o Development of advanced test method to measure direct and indirect core noise contribution
o A first Ground Test Engine demonstration has been conducted with the acquisition of near field and far field core noise measurements.

Over Period 3, the exploitation of the new technologies has been performed on 3D realistic turbofan engines:
• Design and optimisation of an acoustic liner on a 3D realistic turbofan engine core exhaust
• Core acoustic liner assessment at full scale based on a 3D exhaust acoustic modelling
• Core acoustic liner test data base of large CMC samples
• A new core noise data base has been acquired with a complete instrumentation of a combustion chamber and of the turbine.
• A full 3D core noise modelling of a representative UHBR configuration has been conducted to qualify the new CONOCHAIN approach.
• Demonstration of acoustic propagation on realistic UHBR configuration.

Main results of the project have been widely disseminated through publications and are ready for exploitation:
• Development and qualification with test of a new set of solvers to address combustion noise; results have been disseminated and communicated through scientific publications. The solvers are available for exploitation under commercial licensing.
• CMC liners for core noise reduction have been manufactured and tested with success in cold environment; The concepts are available for further demonstration including hot test qualification. results have been disseminated and communicated through scientific publications.
• A new empirical liner model for liner optimization has been developed and validated with test; results have been disseminated and communicated through scientific publications.
• The development of new advanced acoustic methods suited for core noise and associated core noise instrumentation has been developed and qualified on ground test demonstrator; results have been disseminated and communicated through scientific publications.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

Progress beyond the state of the art:
1. New physics in the evaluation of the combustion process and the radiation of acoustic waves
2. Implementation of advanced test methods to address core noise measurements
3. Identification of a new generation of core liners
4. Acoustic propagation modeling in rotating components

Main outcomes
• A new design suite for core noise prediction
• A new set of test methods for core noise measurements
• The acquisition of experimental core noise data base on full scale engine architecture
• The evaluation at full scale of the integration of a new generation of low noise solution

Main impacts of the project :
• To the industry : access to a new and unique 3D industrial modelling workflow to address combustion noise and acoustic design features to develop low noise solution
• To the scientific community, collection of new core noise data base for understanding of the physics
• To the society : Reduction of the noise footprint in the surrounding of airport area

CIRRUS project Overview