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A safe design process and its application are introduced to a concept study for circular variable aero engine inlets. The paper highlights the tasks of inlets, the compromise in designing them and how using variable inlets could solve this compromise and allow for faster and more efficient commercial aircraft. However, high safety and reliability requirements bring up disadvantages. Tackling these disadvantages, a systems engineering approach is complemented by a safety assessment process, according to Aerospace Recommended Practice ARP 4754A. Safety methods that are applicable during early phases of the product development process are presented and applied to develop feasible variable inlet concepts. Hence, safety requirements, potential failure events and resulting failure modes are systematically identified, assessed and mitigated. The mitigation of a failure condition by the means of redundancy within the adjustment control system is presented.
Zukünftige Produktentwicklungen werden auf multidisziplinäre Optimierungen eines virtuellen Modells basieren, da nur sie die Interaktionen zwischen den beteiligten Disziplinen berücksichtigen. Beabsichtigt man beispielsweise ein Produkt hinsichtlich seiner aerodynamischen, thermodynami-schen und statisch-dynamischen Eigenschaften zu optimieren, ist es erforderlich, die Generierung der virtuellen Produktgeometrie zu automatisieren und die interessierenden Dimensionen, welche für die o.g. Disziplinen relevant sind, zu parametrisieren, d.h. flexibel zu gestalten und eine potenzielle Veränderung der Morphologie bzw. der Abmessungen vorzusehen. Wie eine flexible, für die Optimierung angemessene Geometrie zu erstellen ist, ist Gegenstand des vorliegenden Artikels. Dabei wird gezeigt, wie ein 3D CAD-Modell ausgehend von einer einfachen 2D Referenzgeometrie, welche aus Grundgeometrien besteht, und von generisch, parametrisch-assoziativen Benutzerformelementen (User-Defined Features, UDFs) zu generieren ist. Der methodische Ansatz wird am Beispiel eines Kerntriebwerks konkretisiert. Der vorgestellte Prozess ist ein Schritt in Richtung einer flexiblen Geometrieerstellung, die die Durchführung multidisziplinärer Optimierung ermöglicht.
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.
This paper describes the selection of the ideal variable inlet concept group by utilising results of aerodynamic investigations, system safety analyses and integration studies. Aerodynamic and functional inlet requirements are explained and variable inlet concept groups are introduced. The concept evaluation by means of a weighted point rating is presented. The respective concept groups are analysed and evaluated regarding economic, functional and safety requirements. By means of this evaluation, the concept group that adjusts the inlet geometry by rigid segment repositioning is identified as most suitable concept group. The early selection of the most suitable concept group enables more detailed subsequent concept investigations, potentially enabling the technology of variable inlets for future commercial aircraft.
This paper presents an approach to product rating and evaluation of different product solutions for broadband attenuation acoustic liner concepts for aerospace application. In the process, corresponding requirements have been defined for the considered system and evaluation criteria have been derived. Three “Main Evaluation Categories” (Acoustics, System Safety and Integration, Structure and Material) have been introduced to not falsify the assessment results by subject-specific exclusion criteria. A ranked space method has been selected for weighting the evaluation criteria to ensure an objective and knowledge-based rating. The rating has been carried out by a weighted point rating. Concise operational requirements and previously not considered system functions have been identified and linked to the rating and evaluation process. Building on this, further steps for the optimisation and development of the acoustic liner concepts have been presented and explained.
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.
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.
Selected methods of the aviation safety assessment process according to ARP 4761 are introduced and conducted within the scope of a concept study for future broadband acoustic liners. While having similar primary functions and basic design, the acoustic liner concepts diverge concerning subfunctions and potential malfunctions. With the ARP 4761 safety assessment methods, significant differences in sub functions and possible malfunctions of the concepts can be identified. The results of the safety assessment are discussed, and the concepts are evaluated in terms of feasibility and safety.