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									                 Numerical Simulation of Engine/Airframe
                   Integration for High-Bypass Engines
                                   R. Rudnik, C.-C. Rossow

                                         C. Rossow
                                            DLR
                                German Aerospace Center
                             Institute of Design Aerodynamics
                                   D-38108 Braunschweig
                      Tel: +49-531-2952410, Fax: +49-531-2952320
                             Web page: http://www.dlr.de/EA/


Due to a trend towards very high-bypass ratio engines and a corresponding close
coupling of engine and airframe, the minimization of adverse interference effects is an
important aspect in aircraft design. The objective is to retain the benefits of the
increased propulsion efficiency of isolated engines when mounted on the aircraft.
Investigations of engine/airframe integration have been carried out within a long-term
collaborative European research initiative, starting in 1990 in the BRITE/EURAM
program DUPRIN I (Ducted Propfan Investigations), followed by the programs DUPRIN
II to the current ENIFAIR (ENgine Integration on Future Transport AIRcraft) and
AIRDATA (AIRcraft Drag And Thrust Analysis) projects [1].
Based on some selected results the contribution highlights major outcomes of the
numerical activities accompanying the experimental studies in the aforementioned
programs. After a brief introduction to the basic aerodynamic phenomena of
engine/airframe interference the numerical methods as used for this task are presented,
featuring Euler, Euler including boundary layer displacement, and Navier-Stokes
methods.
The capabilities of the theoretical approach are demonstrated for three aspects: The
influence of increasing engine size on the aerodynamic interference is outlined by
simulating the interference for turbine powered engine simulators (TPS) of different
bypass ratio (BPR), incorporating a conventional turbofan simulator (BRP~5), a VHBR
simulator (BRP~10), and a UHBR simulator (BPR~15) mounted on the ALVAST narrow
body wing/fuselage model. Second, the influence of position variations is demonstrated
for the different engine concepts, representing the major design parameter for
influencing engine/airframe interference. Finally, the jet influence is stressed by
comparing numerical results for the thrust conditions “through-flow-nacelle” and “start-
of-cruise” for a turbofan engine.
The investigations show, that the lift loss, caused by the mounting of engines, is
proportional to the engine size. An upstream movement of the engine position alleviates
the lift loss, whereas a downstream movement doesn’t have a significant influence.
Especially for the VHBR and UHBR concepts the incorporation of the engine jet is
essential to assess the aerodynamic interference. In general validated numerical
methods are capable to simulate qualitatively the dominant features of engine/airframe
integration.

                                          References
[1]    W. Burgsmüller, C. Rollin, C.-C. Rossow, “Engine Integration on Future Transport Aircraft – The
       European Research Programs DUPRIN/ENIFAIR”, ICAS paper 98-5.6.2 (1998).

[2]    C.-C. Rossow, H. Hoheisel, “Numerical Studies of Interference Effects of Wing Mounted Advenced
       Engine Concepts”, ICAS paper 94-6.4.1 (1994).

								
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