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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 . 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  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).  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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