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- FG Flug-Triebwerksdesign (5) (remove)
The permanent magnet synchronous motor (PMSM) can be a suitable candidate for electrified propulsion in aviation. Despite the very high efficiency, heat dissipation during operation leads to performance limitations. Elevated temperatures in the electrical insulations and the magnets pose a potential safety risk that must be reduced by selective cooling. A comprehensive review is conducted to capture current research interests in cooling methods in PMSM. Cooling methods are described according to their heat transfer mechanism, grouped, and assigned to the components within the motor. Key findings of the literature reviewed are described in the context of PMSM cooling. Information on cooling media and potential combinations of cooling methods in components is gathered. Assessment parameters such as safety, weight, effectiveness, integrability, complexity and cost are defined to enable a subsequent qualitative analysis for six selected cooling methods. A point-weighted evaluation approach, according to VDI 2225, was applied to identify the most promising cooling approach for successful implementation in aviation.
The next generation of civil turbofan engines targets the by-pass ratios of up to 20:1, requiring an innovative fan design with a low fan pressure ratio, low specific thrust and a radically increased fan diameter. The aerodynamic stability of such a large slow rotating fan is very sensitive against the back-pressure variations in the by-pass duct, especially during the take-off operations. The back-pressure regulation can be achieved significantly through a Variable Area Fan Nozzle (VAFN). This work deals with the design development of VAFN concepts for ultra-high by-pass ratio engines which was researched in EU funded program ENOVAL and received funding under grant agreement number 604999.
A system engineering approach was implemented for the VAFN development by following the requirements in conceptual, preliminary and detailed design phases. The design domains in the rear nacelle and under the core fairing were selected for the concept generation. Several qualitative and quantitative trade studies were conducted to down-select the best-fit solution during each design phase. These included the kinematic simulations of various types of VAFN modulations; analytical calculations to understand the thermodynamics of the selected VAFN kinematics; aerodynamic performance predictions using CFD simulations on a large number of preliminary designs; 3D CFD simulations for detailed performance assessments including the design optimization of individual features and distortions due to failed modulations; and FEM calculations for the topology generation and optimization of structural components. The overall weighted effect was determined for each output parameter and the results were presented in percentile changes relative to that with a fixed nozzle reference geometry.
Two VAFN concepts were selected for the final detailed design phase, Flaps in rear nacelle domain and Variable Inner Fairing Structure (VIFS). Both concepts showed better outputs in terms of specific fuel consumption, noise emission and fan’s safety margin during the take-off, with an over-area exhaust position than those with a fixed nozzle operation. During the climb phase, with an under-area VAFN position, both concepts resulted in drawbacks due to higher aerodynamic losses relative to the fixed nozzle. During MCR, both the VAFN concepts with stowed positions caused losses mainly due to leakages and higher structural weights relative to the fixed nozzle configuration. For each VAFN concept, a detailed system definition was developed and the function trees for each operation were explained. A discrete modulation type with two positions was described and recommended for both concepts. This included an over-area deployed position for the take-off phase and a stowed position for the rest of the flight, based on the beneficial performance of the VAFN concepts over the fixed clean nozzle configuration.
The creation of adequate simulation models for complex assemblies is an extensive process that requires a lot of experience, and on the other hand involves a multitude of manual, tedious tasks. These are significant obstacles for improving the process performance and capabilities. The objective of this research is to develop methods which digitally imitate the way of thoughts of the engineer in the design process towards a digital system understanding and which support the automation of the involved manual workflow.
This thesis presents a strategy to translate engineering reasoning and actions to an equivalent in the computer domain. A cardinal step is to gain understanding of system arrangements, boundary conditions and its components. Based on this evaluation, the identification of assembly parts is forming the foundation for optimized process chains for the transfer to the analysis environment. Model complexity relates to computational effort, which in turn affects model capabilities and manageability. To achieve a satisfactory compromise of model quality and complexity, this transfer process is strongly dependent on the visual analysis, reasoning and manual implementation of skilled engineers.
The principle of translating engineering logics is pursued from the assembly system to its smallest parts. Component segmentation methods allow subdividing regions of interest into substructures which are assigned with a feature vector. This vector comprises metrics describing the substructures with regard to specific aspects and is the key decision point for subsequent steps as idealization, suitable Finite-Element modeling and ultimately building an analysis model. The created system database is continuously maintained and supports these process chains as well as the final setup of the assembly simulation model.
An automated workflow like this implies advantages for efficiency, but also creates opportunities for further use cases. This workflow has been exploited for generating a training data set from the different simulation variants as a basis to a knowledge representation imitating engineering experience. An algorithm from the graph neural network field is applied to this data set as a conceptual approach. The intention pursued in this concept is to model the learning progress about estimating the influence of modelling decisions on simulation results and quality.
This research proposes a holistic strategy and describes methods to achieve the objectives of decreasing manual effort, introducing an automated and geometry-based process and digitally replicating engineering experience by introducing a knowledge database.
As the issue of pollutant emissions from aviation propulsion escalates, research into alternative powertrains is gaining momentum. Two promising technologies are the Hybrid Electric Propulsion System (HEPS) and Pressure Gain Combustion (PGC). HEPS is expected to reduce pollutant emissions by decreasing fuel consumption, whereas PGC uses detonation in the combustor to increase the thermal efficiency of engines by elevating the total pressure during combustion. This study extensively explores the integration of these two emerging technologies, thoroughly assessing the advantages that arise from their combination. First, the renowned turboprop engine PW127 is benchmarked and modeled using Gasturb software. The model is integrated into Simulink using the T-MATS tool, with HEPS and pressure gain components added to analyze the thermodynamics of various configurations under different pressure gain values and HEPS parameters. The analysis, conducted up to the cruise phase of the baseline aircraft, reveals that applying pressure gain combustion through Rotating Detonation Combustion (RDC) results in a more significant increase in efficiency and decrease in fuel consumption compared to HEPS with conventional gas turbines. However, HEPS helps maintain a more uniform combustor inlet condition and reduces the Turbine Inlet Temperature (TIT) at the takeoff phase, where the highest TIT otherwise occurs. The results suggest that integrating HEPS with PGC can be beneficial in maintaining optimal combustor conditions and mitigating turbine efficiency degradation.
Kernziel der Arbeit ist es, einen Beitrag zur Konzeptfindung und zur strukturmechanischen Optimierung von Anbindungsstrukturen für Planetengetriebe in Flugtriebwerken zu leisten. Hierzu wurde ein auf CAD-Geometrien basierender Optimierungsprozess geschaffen und auf verschiedene Problemstellungen angewendet. Die Arbeit gliedert sich in sechs Kapitel, in denen ein Verständnis für die Notwendigkeit und die Problemstellung vermittelt werden soll.
Die Einleitung beschreibt Entwicklungstendenzen für Triebwerke in der zivilen Luftfahrt und die Gründe für den Einsatz von Planetengetrieben. Da die hier entwickelten Methoden die Konzeptfindung und somit die Produktentwicklung unterstützen sollen, wird skizziert, an welcher Stelle des Produktentwicklungsprozesses die Methoden am besten einzusetzen sind.
Das zweite und dritte Kapitel sind der Strukturoptimierung gewidmet. Zunächst werden die Grundlagen Optimierung und wichtige Ansätze erläutert. Anschließend werden die üblichen Verfahren zur Strukturoptimierung mithilfe von finiten Elemente-Netzen vorgestellt. Folgend werden zwei Sonderfälle betrachtet, die Optimierung von flexiblen Bauteilen und von mehreren Bauteilen im Verbund. Beides stellt eine besondere Herausforderung dar und wird in den späteren Fallstudien aufgegriffen. Im dritten Kapitel wird der alternative, auf CAD-Geometrien basierende Ansatz zur Strukturoptimierung vorgestellt. Abschließend werden die Methoden anhand von akademischen Beispielen validiert.
Das vierte Kapitel befasst sich mit Antwortflächenverfahren. Sie sind ein gängiges Mittel, um Optimierungsprozesse zu beschleunigen. Hierzu werden zunächst die wichtigsten Grundlagen zur nötigen Versuchsplanung erläutert und die drei gängigsten Ansätze diskutiert. Auf der Grundlage eines Vergleichs dieser Verfahren wird ein geeigneter Ansatz ausgewählt.
Im fünften Kapitel werden fünf Fallstudien aufgeführt. Jede davon greift eine praxisnahe Problemstellung auf und demonstriert die Herangehensweise und die Möglichkeiten und Grenzen eines auf CAD-Geometrien basierten Ansatzes zur Strukturoptimierung. Das erste, zweite und fünfte Fallbeispiel beziehen sich auf die im zweiten Kapitel genannten Sonderfälle. Im dritten Fallbeispiel wird eine Optimierung der Systemeigenfrequenz durchgeführt, die es nötig macht, eine Brücke von der Einzelkomponente zu einem aus reduzierten Matrizen bestehenden Systemmodell zu schlagen. Im vierten Fallbeispiel werden die im vierten Kapitel beschriebenen Antwortflächenverfahren eingesetzt, um die reduzierte Matrix einer Einzelkomponente für ein Systemmodell auf der Basis der Geometrieparameter vorherzusagen.
Abschließend fasst das sechste Kapitel die Ergebnisse zusammen. Die gezeigten Ansätze sind sehr gut geeignet, um flexible Strukturen zu finden. Die Systemoptimierung und Prozessbeschleunigung konnten erfolgreich durchgeführt werden und haben zu signifikanten Verbesserungen geführt. Abschließend wird das Vorgehen im Vergleich zu anderen Lösungsmöglichkeiten bewertet.