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- FG Flug-Triebwerksdesign (5) (remove)
This paper presents design adaptations during the further development of innovative broadband acoustic liner concepts (Foil Helmholtz Resonator Liner; FHR-Liners) which utilise flexible foils within a honeycomb structure to attenuate engine and aircraft noise. The requirements for acoustic liners in aviation are described and utilised to derive evaluation criteria. Modifications of the FHR-Liner concept are introduced. A suitable concept evaluation method based on VDI 2225 is applied to evaluate the modified liner concepts concerning the main evaluation criteria.
An essential aspect in the whole engine modelling of modern aircraft engines is the preliminary design of the meridional gas path definition. Especially the annulus dimensioning and topological characterisation of engine core subsystems are usually time-consuming. This paper presents a holistic and parametric approach to predesign the geometric 2D annulus contours of compressor and turbine subsystems without complex thermodynamic calculations. It is based on distribution functions of the axial and radial dimensions, as well as the variations of compressor and turbine stages and realises a time-efficient re-dimensioning and topological variation of the complex annulus geometry. Parametric methods for an optimised arrangement of the blade stages in a turbomachinery subsystem configuration are shown and integrated into a mathematical model.
Due to current developments in jet engine design, the acoustic performance of conventional acoustic liners needs to be improved with respect to lower frequency spectrums and broadband absorption. In this context, the present study aimed to determine the viscoelastic material properties of a thermoplastic polyurethane (TPU) film for targeted application in novel acoustic liners with integrated film material for enhanced noise reduction. Therefore, a dynamic mechanical analysis (DMA) was performed to determine these viscoelastic material properties. Based on the acquired data, the time-temperature shift (TTS) was applied to obtain the material’s temperature- and frequency-dependent mechanical properties. In this regard, the William-Landel-Ferry (WLF) method and an alternative polynomial approach determining the shift factors were investigated and compared. Furthermore, a generalized Maxwell model—so-called Prony-series—with and without pre-smoothing utilizing of a fractional rheological model was applied to approximate the measured storage and loss modulus and to provide a material model that can be used in finite element analyses. Finally, the results were discussed concerning the application of the films in acoustic liners under the conditions of a standard flight cycle and the applied loads. The present investigations thus provide a method for characterizing polymer materials, approximating their mechanical behavior for vibration applications at different ambient temperatures and enabling the identification of their operational limits during the application in acoustic liners.
This paper presents a combined experimental and numerical investigation on a novel liner concept for enhanced low-frequency and broadband acoustic attenuation. In particular, two different realizations, derived from conventional Helmholtz resonators (HR) and plate resonators (PR) are investigated, which both deploy flexible materials with material inherent damping. In this context, a comprehensive experimental investigation was carried out focusing the identification and evaluation of various geometric parameters and material properties on the acoustics dissipation and related properties of various materials in a simplified setup of a single Helmholtz resonator with flexible walls (FHR concept). Furthermore, a parameter study based on analytical models was performed for both liner concepts, taking into account material as well as geometric parameters and their effects on transmission loss. In addition, design concepts that enable cylindrical or otherwise curved liner structures and the corresponding manufacturing technologies are presented, while considering essential structural features such as drainage. With respect to the potential application in jet engines, a structural–mechanical analysis considering the relevant load cases to compare and discuss the mechanical performance of a classical HR and the FHR concept liner is presented. Finally, both concepts are evaluated and possible challenges and potentials for further implementation are described.
Der Beginn einer jeden Triebwerksentwicklung startet mit der Auslegung des Ringraumes des Primärgasstromes. Hier müssen einige vorläufige aber auch grundlegende Entscheidungen zu Entwurfsparametern wie Eintrittsquerschnitte, Subsystemlängen, axiale Stufenanzahl in Verdichter und Turbine, usw. definiert werden. Für die Vorauslegung sollte die Palette an anfänglichen Entwurfsparametern so gering wie möglich gehalten werden, um die Menge an möglichen Ringraumentwürfen nicht frühzeitig einzuschränken. Dieses Paper präsentiert das Vorauslegungswerkzeug „Gas Path Designer“ (GPD), welches in der Lage ist Ringraumentwürfe für Turbotriebwerke über zeiteffiziente Berechnungsmethoden in kürzester Zeit bereitzustellen. Das Interface bietet eine Auswahl an Einstellungen, um die genannten Variationsmöglichkeiten zu unterstützen. Der Aufbau ist übersichtlich, um im Rahmen grundlegender konzeptorientierter Gespräche mit dem Kunden eine schnelle und beidseitig nachvollziehbare Variation und Visualisierung des Konzeptentwurfes zu ermöglichen. Des Weiteren können die erhaltenen Ringraumstrukturen der Triebwerksentwürfe als Leitstruktur für CAD-Programme sowie weiterführende Optimierungsstrategien genutzt werden.
