Aerodynamic Installation Effects of Over the wing Mounted Ultra high bypass Engines

• In order to increase propulsive efficiency and decrease specific thrust, future aeroengines for commercial airliners will have to operate with higher bypass ratios and lower fan pressure ratios. This results in a substantial increase of the fan diameter. One major issue with the conventional under-wing installation of ultrahigh-bypass engines is the limited space underneath the wings. Integrating larger engines under-the-wings could require prohibitive increase in landing gear height and weight to attain an adequate ground clearance. One potential solution is to mount the engines over-the-wings, which would eliminate the ground clearance problem and, in addition, reduce ground noise. Over-wing nacelle installation acquired a bad reputation in the past since the benefits of such configuration would be often outweighed by poor aerodynamic performance. Nonetheless, some recent studies indicate that over-wing mounted nacelles could be a feasible integration option. This paper provides an aerodynamic evaluation of an over-the-wing mounted nacelle configuration compared with an under-the-wing configuration for a mid-cruise condition. The nacelles and pylons are designed by using an in-house tool for engine aircraft aerodynamic integration. The flow field is computed by means of Reynolds-averaged Navier-Stokes equations. The effects of wing/nacelle/pylon interference are investigated, and the aerodynamic performance of each configuration is evaluated by means of thrust and drag bookkeeping. Results show that the over-the-wing nacelle installation has increased the overall drag by 19.7 drag counts, when compared to a conventional under-wing mount, which was caused mainly due to a higher wing wave drag and pylon/nacelle interference drag.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Maskinteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Mechanical Engineering (hsv//eng)

Nyckelord

propulsion integration

nacelle

aerodynamics

ultra-high bypass ratio

computational fluid dynamics

Over-the-wing nacelle installation

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