Investigations into the operational effectiveness of hybrid laminar flow control aircraft

摘要

Hybrid Laminar Flow Control (HLFC) is an active drag reduction technique thatpermits extended laminar flow on an aircraft surface at chord Reynolds numbersnormally associated with turbulent flow. The operational effectiveness of HLFCaircraft relates to the probability of a partial or complete loss of laminar flow. Fourfactors were considered: (1) Ice particles in cirrus clouds; (2) Insect contamination; (3)Mechanical failure; and (4) Damage to the suction surfaces.Two computer programs capable of determining the required fuel for a givenmission profile have been developed for aircraft in the classes of the B757-200 and theA330-200. The programs were validated against published payload-range data, andmodified to emulate the installation of a HLFC system, by incorporating changes to thedrag polar, Specific Fuel Consumption (SFC) and Operating Empty Weight (OEW).Sensitivity studies were conducted. The results permit estimates to be determined of thetrip fuel reduction of HLFC aircraft compared to equivalent turbulent aircraft.A conceptual design of a HLFC system has been developed for the referenceaircraft. A SFC penalty of 1.6% was determined for the B757-200 class aircraft (range:3272nm, payload: 19147kg) and 2.1% for the A330-200 class aircraft (range: 5980nm,payload: 24035kg) for a system capable of reducing the drag by approximately 14%.The installed system weight represents 2.0% and 1.6% of the OEW for the B757-200and A330-200 classes of aircraft respectively. The reduction in trip fuel, compared tothe turbulent baseline vehicles, was estimated to be 7.4% for these conditions. Toobtain the greatest benefit for a HLFC aircraft, the fuel planning must consider theprobable time-in-cloud that will result in a loss of laminar flow. An optimised fuelplanning approach, which requires a forecast of en route cirrus cloud, has beenestimated to further reduce the trip fuel for long-range missions by 2.5 - 3.8%.