Airbus is developing a noise-dampening engine nacelle intake that could become a feature of the new A350 XWB widebody twinjet.
The next-generation reduced acoustic mode scattering engine duct system (RAMSES) is a development of Airbus's "zero splice" intake liner developed for the A380, which is undergoing flight testing on the ultra-large aircraft.
The zero splice liner has a continuous surface and lacks the distinct joins that exist on conventional liners, which are constructed from two or three pieces. In 1997 Airbus started a study using acoustic finite element model simulations that
|The zero-splice intake (left) concentrates sound energy close to walls|
The zero splice intake was tested on a Rolls-Royce scale-model fan rig, and the results showed a significant reduction in noise, with a drop of more than 3EPN decibels for forward fan noise.
To achieve this, however, liner design and manufacturing problems had to be overcome. A one-piece composite liner's geometry is complex and it could not easily be removed from its mould, so a retractable mould was developed to solve the problem. "Developing the retractable tool was really a challenge, which was successfully overcome by Airbus mechanical design and manufacturing specialists from Toulouse and Nantes," says Airbus head of nacelle acoustics Hervé Batard.
Research under the European Union's Fifth Framework programme's Significantly Lower Community Exposure to Aircraft Noise project also contributed to the liner's development.