An aeroengine with the electrical generator mounted directly on to the main shaft could be demonstrated in 2006 following Rolls-Royce-sponsored research at the UK's University of Manchester.
The advantage of an embedded electrical generator is that it can efficiently generate substantially more power, typically 125kW, for more-electric and all-electric aircraft systems. Under R-R's plans such engines could be available for use in airliners after 2010.
The technical challenges to developing a shaft-mounted brushless DC electrical generator include coping with operating temperatures in excess of 220°C (428°F).
"We've got to look at improved materials to operate at the higher temperatures," says R-R head of technology strategy Dr David Clarke, "and we have to have a system that can cope with a wide range of shaft speeds and wide voltage ranges, and an ability to meet the [aircraft's] changing electrical loads."
Silicon carbide-based electronics is one solution to the high temperature environment in which the generator's circuits would operate.
But keeping the generator cool enough is another requirement and that would see a mixture of techniques used - from air to oil to heat-sink materials. For high strength and low cost, the generator's magnets would likely be neo-dymium iron boron.
The engine technology development programme is a part of the European Commission funded Fifth Framework research project known as Power Optimised Aircraft. It began in 2002 and ends in 2006. More electric engines are to be a focus for a new R-R funded University Technolgy Centre at Manchester University, which was announced on 12 November.
Source: Flight International
