Air Transport World

Rolls-Royce explores ducted 'big turbofan.'

London--Rolls-Royce has been talking with major airframe manufacturers, notably Boeing and Airbus Industrie, about a ducted next-generation big turbofan based on some of the technology that will go into unducted propfans, and has found them "eager to pursue the idea," according to David Marshall, head of new projects.

Thinking behind Rolls' interest is that propfans will only be usable as a twin installation at the rear of small and medium airliners, while around 50% in value of the company's business has come in recent years from its RB211 family of big engines on the Boeing 747 and Lockheed L-1011. Propfans, its reasons, will never, for technical reasons, be hung beneath the wings of airliners. And so six months ago it started research into a big ducted turbofan that could fill this need and could power future versions of the 747 and the projected Airbus TA9/TA11 series, each of which would have new wings.

In Rolls' preliminary design (see diagram), the counter-rotating fan that Rolls is adopting for its propfan is placed inside a duct. This, said Marshall, appears to give good aerodynamic efficiency for the fan plus good fuel consumption. There is no longer any need to put a big shaft through the engine to carry the fan at the front, and there also are some advantages in the sizing of the core, he said.

Reduced fuel consumption

"Very broadly, we can see that if an engine such as this can be installed satsifactorily, it will give us a 20% reduction in fuel consumption relative to the best RB211-524 we have flying at the moment," said Marshall. "We are seeing the airframe manufacturers and asking them whether they would be interested in such an underwing installation, and seeing at what stage they are in thinking about a new generation of airplanes. …

Log in to your account to read this article – and millions more.