Gehen mit dem Wind: adaptive Turbofan-Einlässe

Turbofan-Triebwerksgondeln mit formangepassten Einlässen haben das Potenzial, die Startleistung bei Seitenwind zu verbessern und den Widerstand im Reiseflug zu verringern. Gondeln sind, wie fast alle anderen Flugzeugkomponenten, ein konstruktiver Kompromiss für eine Vielzahl von Betriebs- und Randbedingungen. Wie bei anderen aerodynamischen Strukturen bestimmen ihre Formen ihre Funktionen: Dicke, abgerundete Einlässe eignen sich am besten für den Start bei starkem Seitenwind und hohen Anstellwinkeln und leiten die Strömung möglichst gleichmäßig und ablösungs- und verzerrungsfrei in das Triebwerk, was für einen sicheren Triebwerksbetrieb von entscheidender Bedeutung ist. Schlanke, scharfe Einlässe eignen sich am besten für den Reiseflug, da sie den Luftwiderstand verringern. Adaptive Inlets können das Beste aus diesen beiden Welten bieten, indem sie sich je nach Strömungsanforderungen zwischen den geometrischen Zuständen anpassen. Während das Konzept der adaptiven Inlets nicht neu ist, da sie bereits seit Jahrzehnten in Überschalltriebwerken eingesetzt werden, entwickelt das DLR zusammen mit dem Industriepartner Rolls-Royce Deutschland im LuFo-Projekt ModeGo neue Verbundwerkstoffkombinationen und Simulationsmethoden

Experimental Results of a Fluid Actuated Morphing Winglet Trailing Edge

Designing active control surface technology into thin regions of aircraft wings is challenging due to small available volumes. To be able to do so is potentially beneficial to enable more efficient wing designs using morphing for e.g. load alleviation. This paper details a winglet trailing edge surface composed of fluid actuated morphing unit structures (FAMoUS) that enable control surface deflections under the corresponding aerodynamic hinge moments. These FAMoUS actuators are comprised of elastomer and metallic stiffeners, which under internal pressure from a fluid exert displacement and force and thus output work. Combining these unit structures in a bimorph setup a trailing edge control surface is build. This paper outlines the design, finite element analyses and manufacturing process of a demonstrator with 1 m span-width. These finite element analyses consist of detailed tuned material parameters obtained from testing on the individual unit structure tests as well as the inclusion of hydrostatic fluid elements to determine effective stiffnesses from the pressure-volume relationship between the housing structure and internal fluid. Manufacturing of the demonstrator is conducted using composite fabrication and machining techniques to ensure that the demanding tolerances and surface qualities are to be maintained. The structural part of the demonstrator is joint with an actuating system, where in combination wíth feedback sensors position control is achieved. The setup of the actuating system is introduced, elucidating the hydraulic system and the overall control design. Experimental results of tests are presented, starting with calibration of the feedback system with an external measurement, also clarifying deflection uniformity along the span of the demonstrator. Further results of deflection performance and deflection rate are presented and compared to the predictions derived from the finite element analyses. The findings are discussed and contextualized. A summary of the results is given and an outlook on the way forward is presented

Strukturkonzept eines vorgebogenen morphenden Spoilers zur adaptiven transsonischen Stoßkontrolle

Zur Erreichung globaler Reduktionsziele von Treibhausgasemissionen kann die transsonische Stoßkontrolle einen wichtigen Beitrag in der zukünftigen Luftfahrt liefern. Seit etwa 30 Jahren wird diese Form der Widerstandsreduktion an Tragflächen von Flugzeugflügeln erforscht. Dabei hat sich die sogenannte Stoßkontrollbeule (Shock Control Bump - SCB) als besonders effektive Methode erwiesen, den Wellenwiderstand von transsonischen Flugzeugflügeln zu reduzieren. Außerhalb des Auslegungsbereichs wird eine fest installierte SCB allerdings zu unerwünschten Effekten führen wie z. B. zu einer Erhöhung des Widerstands und somit des Treibstoffverbrauchs. Folglich sollten adaptive Konzepte verwendet werden, welche die SCB einfahren können, wenn sie nicht benötigt wird. In dieser Arbeit wird ein morphender Spoiler mit einer adaptiven SCB vorgestellt, welche in ihrer Höhe einstellbar ist sowie gänzlich eingefahren werden kann. Es wird das strukturelle Design des Spoilers erläutert, welches diese Formvariabilität ermöglicht. Das Finite-Elemente-Modell der Spoilerstruktur wird in ANSYS mit aerodynamischen Kräften für den Reiseflug beaufschlagt. Zudem wird eine Vorspannung für einen begrenzten Bereich der Spoilerstruktur implementiert. Durch diese resultierende Vorbiegung des hinteren (stromabwärtsliegenden) Spoilerbereichs kann dieses adaptive Konzept mit dem Spoileraktuator als einzigen Aktuator eine morphende SCB formen

Morphing Turbofan Engine Inlet at Take-off Cross-wind Conditions

Aeronautical engine inlets are designed as a compromise between low-drag configurations for cruise condition and high airflow incidence angle during take-off and landing. In order to fulfill all the requirements belonging to different operating points, adaptive or morphing structures could be a feasible solution, and they could potentially have a positive impact in terms of aerodynamic performance, therefore leading to a substantial reduction in fuel consumption. However, designing morphing inlets is challenging because of the coupling between aerodynamics and structural analysis which is crucial in order to consider both the feasibility of the adaptive structure and its effects on the aerodynamics of the nacelle. This paper outlines the structural design of an adaptive inlet which features hybrid elastomeric composite materials and a means of active actuation. Since the inlet geometry features both radial and circumferential axes, any change in one axis creates a change in the other resulting in the need of stretchable materials if unwanted steps and gaps are to be prevented for favorable laminar-turbulent transition. To evaluate the aerodynamic effects of such a morphing inlet, a computational fluid-dynamic analysis is coupled with the finite element analysis leading to a “one-way” fluid-structure interaction approach. The goal of the presented method is the definition of an automatic aero-structure coupling framework in order to ease the exploration of a variety of designs over the feasible design space. Results highlight pros and cons of three different design approaches with a particular focus on promising aerodynamic results despite some difficulties in the structural feasibilit

Review of Adaptive Shock Control Systems

Drag reduction plays a major role in future aircraft design in order to lower emissions in aviation. In transonic flight, the transonic shock induces wave drag and thus increases the overall aircraft drag and hence emissions. In the past decades, shock control has been investigated intensively from an aerodynamic point of view and has proven its efficacy in terms of reducing wave drag. Furthermore, a number of concepts for shock control bumps (SCBs) that can adapt their position and height have been introduced. The implementation of adaptive SCBs requires a trade-off between aerodynamic benefits, system complexity and overall robustness. The challenge is to find a system with low complexity which still generates sufficient aerodynamic improvement to attain an overall system benefit. The objectives of this paper are to summarize adaptive concepts for shock control, and to evaluate and compare them in terms of their advantages and challenges of their system integrity so as to offer a basis for robust comparisons. The investigated concepts include different actuation systems as conventional spoiler actuators, shape memory alloys (SMAs) or pressurized elements. Near-term applications are seen for spoiler actuator concepts while highest controllability is identified for concepts several with smaller actuators such as SMAs

3D Design of a Large-Displacement Droop-Nose Wing Device

The 3D structural design of a morphing droop-nose device for a new high-lift system is presented in this paper. This new type of high-lift system is anticipated to reduce airframe noise, takeoff and landing speeds and thus runway length, and be capable of actively producing a range of lift coefficients as per demand. A structural design process using optimization tools was further developed and applied to the case of large target deflections required for this high-lift system. The results of the 3D optimization of thickness distribution, stringer position, and force introduction points on a hybrid fiberglass-elastomeric composite skin showed close agreement to the target shapes under different aerodynamic load cases. The design of a kinematic system of linkages was also performed and upon input actuation the outer surface conformed to the target aerodynamic shapes. Required actuator torque in this design was shown to be high in the order of 3600 Nm thought actuators are available which meet the internal space requirements. Reported strains were within design limits in the order of 1.5%. The design is set to be refined in the near future with manufacturing and ground tests to follow.