VITAL progress on aircraft noise and emissions

A £62m project to reduce aircraft noise and CO2 emissions involving all major European aircraft engine manufacturers was launched this week. The VITAL programme involves 52 partners including Rolls-Royce, Volvo and Airbus, and is backed by £35m in EC funding. The consortium aims to produce a 5–8dB noise reduction and an eight per cent reduction in CO2 emission as a result of the four-year project.

The key aim is to deliver noise and emission reduction technologies in the low pressure part of engines such as the fans. A parallel project, NEWAC, starting later this year, will focus on the high pressure areas.

In seven major sub-projects the partners will develop low-pressure engine parts such as lightened fans and turbines with fewer blades. The weight reduction will allow engine designs with very high bypass ratios, the relative amount of cold air entering the engine, which would reduce noise. French engine manufacturer Snecma, co-ordinating the VITAL programme, is testing a counter-rotating fan as a means of cutting noise.

‘A classic turbofan will have some parts above the speed of sound, some parts below,’ said Serge Eury, deputy vice-president of R&D at Snecma. ‘One solution is to reduce fan speed by having two work together in counter-rotation.’ Increasing the amount of bled air via a higher diameter fan would reduce noise too, but would lead to heavier engines and efficiency loss.

Snecma will also focus on the use of metallic composite material to offer higher strength and rigidity for the low pressure shaft in the engine, and so reduce its size.

The project follows on from previous research programmes such as EEFAE, in which Rolls-Royce led an effort to cut emissions, and the Snecma-led SILENCE, which sought to cut noise. By 2020 the EC aims to halve perceived noise and carbonic gases and reduce nitrogen oxides by 80 per cent.