The installation of a gas turbine engine onto an aircraft often necessitates the use of complicated ducting for the inlet and exhaust from the engine nacelle. These ducts may involve shape transitions as well as significant redirection of the flow. The optimization of these ducts may reduce the performance losses typically incurred with inlet and exhaust ducting. This study examines the aerodynamic and performance characteristics of a specific duct geometry that is a combination of a transition duct and an s-shaped duct. The study is motivated by aircraft gas turbine exhaust design considerations including lower engine back pressure, reduced wing sooting, and the reduction of thermal fatigue issues with aircraft structures. Experimental and computational (CFD) techniques were used to investigate the internal flow structure and distortion losses. Swirl was introduced to determine the sensitivity of the duct to the rotating flow typical of a gas turbine. Cold flow testing was performed for a scale model of the duct and compared with results from a commercial 3D CFD code. Velocity profiles were well predicated but loses were underpredicted by the RNG-kε turbulence model. The study has shown the value of CFD for the prediction of general performance trends in the design of a practical engineering device.

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