Natural and Hybrid Laminar Flow Control for Aero-Engine Nacelles 952016
In the search for methods of reducing aircraft drag, much attention has been devoted to the problems of maintaining large areas of laminar flow on wings. However, the operational requirement of high subsonic cruising speeds implies the use of wing sweep. This complicates the design since wing flows are fully three-dimensional and additional mechanisms for boundary layer transition e.g. attachment line contamination and cross-flow instability are present. In this research programme, an alternative component, the engine nacelle, is considered as a candidate for the application of laminar flow.
The achievement of large areas of laminar flow over aircraft engine nacelles offers significant savings in aircraft fuel consumption. Based upon current configurations, net benefits of up to 1.5% sfc are predicted in the case of natural laminar flow (NLF) - applicable to small to medium range civil transport aircraft, whereas in the case of hybrid laminar flow (HLF) for medium to long haul civil transport aircraft, benefits of up to 2% sfc are possible. In addition the nacelle is ideally suited to the early introduction of laminar flow technology being a mostly self-contained item. This brings with it the possibility of application to existing airframes.