The Influence of Shape-Variability on the Design and Aerodynamics of a Transonic Turbofan Rotor
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Beschreibung
Sustainability is becoming increasingly important in aircraft engine design. While the engine operates at high efficiencies during its design flight phase, lower efficiencies are provoked for the remaining flight mission. As the fan has become the main thrust generating component, improving its off-design efficiency is a promising approach to boost the sustainability of future air transport systems. To reduce flow separation and performance deficits at off-design flow conditions, this research investigates the benefits of a shape-variable fan rotor. With the goal to adjust the twist and cambering of the rotor, piezoelectric Macro-Fiber-Composite actuators are integrated into the metallic blading of the fan rotor. Depending on the actuators’ fiber orientation, a voltage supply induces an elastic deformation of the actuators, which leads to the morphing of the turbofan rotor. A design methodology is derived, to align the structurally feasible deformations with the aerodynamic off-design requirements. Here, special emphasis is given to fan operating points at throttled conditions. The design methodology allows to numerically quantify the desirable and achievable aerodynamic effects, induced by the shape-adaption. This includes a re-engineering routine for the morphed rotor geometries, as well as Quasi-3D and 3D CFD calculations to account for the blade-shock interaction and secondary flow phenomena. The structural morphing methodology is adapted to derive actuator configurations suited for the specified aerodynamic off-design scenarios. The effect of varying rotor geometries on the feasible angular deformations is also considered, including 3D design measures. The coupled aerostructural design methodology is initially applied to the well-researched NASA rotor 67. As the deformations of the transonic test case rotor become highest at the blade tip, the morphing effect exhibits a strong dependency on the blade-shock interaction. In the performance map, different morphing effects are therefore predicted, depending on the fraction of the blade span that exhibits a passage shock. By transferring the integral morphing effects to the performance map of the fan of the V2500-A1 engine, the impact of different actuator configurations on flight mission level is assessed. Here, beneficial effects on fuel consumption are already observed for angular deformations below 1°. The conclusions drawn are finally exploited to propose a scaled fan design for a test rig application. This results in a low hub-to-tip ratio fan design with a slender and forward swept blade, allowing for an improved twist and camber angle variability. With respect to the stationary working line of the fan stage, efficiency as well as thrust-to-power ratio improvements are achieved, especially for reduced rotational speeds and operating points close to the stability limit of the fan.
Autor*in
Marcel Seidler
Themen in »The Influence of Shape-Variability on the Design and Aerodynamics of a Transonic Turbofan Rotor«
turbofan design transonic shape-adaption aircraft engine