A consortium of European aerospace companies is preparing to begin full-scale windtunnel testing of what it claims is the world's first complete laminar-flow engine-nacelle system, aimed at reducing dramatically the amount of drag produced by wing-mounted engine installations.
The team hopes the ground-based trials will lead to further European Union funding, to allow flight-testing to begin by 1999.
Engine nacelles are seen as a leading application for laminar-flow technology, because the airflow through and around them is relatively simple to analyse, and modified nacelles are easy to retrofit to existing aircraft.
In addition, engine manufacturers believe that it is cheaper to reduce the drag produced by the engine installation as a way of effectively increasing thrust, rather than modifying the core of the engine. Reductions in nacelle drag of up to 30% are expected to lead to overall fuel savings of 1-3%.
According to Professor Ian Poll of the Cranfield College of Aeronautics, where the windtunnel tests will be conducted, the Hybrid Laminar Flow on Aircraft Demonstrator project will test the dynamically controlled laminar-flow system, and mechanisms to de-ice and clean the microscopic suction holes which smooth the airflow.
Poll says that the tests are also designed to demonstrate that laminar-flow engine nacelles are "aerodynamically straightforward", and offer "-big enough potential benefits to be worthy of the investment".
He adds that the engine nacelle is a good target for introducing laminar-flow technology in aircraft.
According to Poll, the intakes used on existing engines encourage turbulent airflow around the nacelle. "The drag has always been accepted as a consequence of the engine getting the air it needs," he says. "We can maintain the performance of the nacelle -and, by using surface suction, maintain the laminar flow hitherto sacrificed for engine performance," he adds.
Other participants in the project include GEC, Hispano Suiza, Hurel Dubois, Rolls-Royce, Shorts and Snecma.
Source: Flight International
