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Content archived on 2024-06-11

Reduction of airframe and installation noise

Objective



Objectives and content: The airframe itself can strongly influence the noise radiation from aircraft. Not only can the airframe through diffraction, refraction and reflection modify the noise radiated by the engines but it also acts as a strong source of additional noise radiation either directly from its components (for example the undercarriage and wing with high lift devices deployed) or indirectly by modifying or coupling with certain engine flow features. To date such sources of noise whilst important have had limited impact on the overall optimisation of the aircraft. However, the trend towards very high by-pass ratio engines with their differing source breakdown coupled with the trend to aircraft of larger size offers the prospect that future new aircraft designs may well be limited in realising their full operational efficiency and hence competitiveness by such acoustic effects. Therefore, there is a clear industrial need to develop an improved design capability, which enables the effects of the airframe on the overall aircraft noise radiation to be addressed in the early stages of design. Such a capability is essential if airframe noise and installation effects are to feature in the aircraft optimisation process. On approach the noise radiated from the airframe itself will be comparable with that of the engines and will limit the potential benefit of future engine noise reductions. The noise contribution from each of the components of the airframe need to be accurately predicted.

As the nature and magnitude of airframe installation affects the noise radiation from the various engine sources in differing ways, the need is to accurately predict the installation effects for the main or dominant components - jet, fan turbine and combustion. The current proposal aims to make a major contribution towards establishing such a competitive design capability. Advanced analysis tools will be developed based on sound theoretical approach at component level. New improved model scale experimental noise databases will be established and used in the development and calibration of these new analysis tools. Full-scale flight test data will be used to establish scale effects and for confirmation of the overall prediction capability. In parallel to the development of the analysis tools practical approaches to noise reduction will be identified and evaluated to provide confidence that such analysis tools are capable of implementation within design optimisation studies. The project is expected to realise at component level reductions in noise of the order of 5 to 10 dB. Full impact will be realised when the new airframe related technology developed here is integrated with that of the engine on an overall aircraft noise level basis when this is expected to result to a net improvement of less than 5 EPNL dependent on the engine noise contribution. This proposal is submitted within the framework Technical Area 3A.4 (environmental technologies) of the Brite-Euram Programme. As such it is one of the X - projects that form a cluster to address community noise reduction.

It is believed that only a co-ordinated initiative at the European level, building on EC and National programs, expanding the scope of research topics to counter the US effort and providing the "demonstrator" capability that National programs cannot afford alone, will deliver the expected environmental and competitive benefit. The cost and scale of the project is further justified because of the number of tests required (wind tunnel occupation and the provision of a flight test aircraft costs are very significant) to obtain databases, so that the improved prediction tools of airframe noise and installation effects on engine (fan, jet and core) noise can be validated and design rules formulated. The noise reduction design will also be conducted and assessed (both in full scale and scaled model) in the wind tunnels. Together with the other noise cluster programs (RESOUND, RANNTAC) noise reduction achievement, the total noise reduction is expected to be 6 dB. The proposed work is very important as the airframe and installation noise is already affecting the existing aircraft, and need to be fully controlled in the design development of a new generation of aircraft (airframe noise may be a limiting factor in the development of the future large European aircraft) if community noise requirements are to be fully satisfied. It is believed that only a co-ordinated initiative at the European level, building on EC and National programs, expanding the scope of research topics to counter the US effort and providing the "demonstrator" capability that National programs cannot afford alone, will deliver the expected environmental and competitive benefit.

The cost and scale of the project is further justified because of the number of tests required (wind tunnel occupation and the provision of a flight test aircraft costs are very significant) to obtain databases, so that the improved prediction tools of airframe noise and installation effects on engine (fan, jet and core) noise can be validated and design rules formulated. The noise reduction design will also be conducted and assessed (both in full scale and scaled model) in the wind tunnels. Together with the other noise cluster programs (RESOUND, RANNTAC) noise reduction achievement, the total noise reduction is expected to be 6 dB. The proposed work is very important as the airframe and installation noise is already affecting the existing aircraft, and need to be fully controlled in the design development of a new generation of aircraft (airframe noise may be a limiting factor in the development of the future large European aircraft) if community noise requirements are to be fully satisfied. BE97-4035

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AIRBUS UK LIMITED
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New Filton House, Filton
BRISTOL
United Kingdom

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