@inproceedings{GrasseltHoeschler, author = {Grasselt, David and H{\"o}schler, Klaus}, title = {Vergleich von FSI Methoden kommerzieller integrativer Programme gegen{\"u}ber inkonsistenten L{\"o}sungen am Beispiel eines Schubumkehrers im Flug-Triebwerk}, series = {Deutscher Luft- und Raumfahrtkongress 2015, 22. -24. September 2015, Rostock}, booktitle = {Deutscher Luft- und Raumfahrtkongress 2015, 22. -24. September 2015, Rostock}, publisher = {Deutsche Gesellschaft f{\"u}r Luft- und Raumfahrt - Lilienthal-Oberth e.V.}, address = {Bonn}, url = {http://nbn-resolving.de/urn:nbn:de:101:1-201512113094}, pages = {7}, language = {de} } @inproceedings{SainHoeschlerMischke, author = {Sain, Chetan Kumar and H{\"o}schler, Klaus and Mischke, Marcel}, title = {Concept study of variable area fan nozzle for UHBPR turbofan engine}, series = {22nd International Symposium on Air Breathing Engines (ISABE-2015-20213), 25.-30. Oktober 2015, Phoenix (AZ, USA)}, booktitle = {22nd International Symposium on Air Breathing Engines (ISABE-2015-20213), 25.-30. Oktober 2015, Phoenix (AZ, USA)}, publisher = {ISABE}, pages = {8}, language = {en} } @inproceedings{SainHoeschler, author = {Sain, Chetan Kumar and H{\"o}schler, Klaus}, title = {Comparative Assessment between Variable Area Fan Nozzle Concepts at Inner and Outer By-Pass Duct Surfaces}, series = {ISABE-2017-21342, 03.-08. September 2017, Manchester (UK)}, booktitle = {ISABE-2017-21342, 03.-08. September 2017, Manchester (UK)}, publisher = {ISABE}, pages = {10}, abstract = {The next generation of civil turbofan engines target the by-pass ratios of up to 20:1, which are far beyond the current levels of 10:1 to 12:1. These jet engines require a significant step forward in low-pressure system technologies. The European Union supports within the 7th Framework the research activities for these new low-pressure systems through the program ENOVAL [1]. Such a new low-pressure technology can be achieved through an innovative fan design with a low fan pressure ratio and a radically increased fan diameter compared to the current conventional turbofan engines. The aerodynamic stability of such large fans is quite likely very sensitive against backpressure variations in the by-pass duct. For this reason, the back-pressure regulation of such a large fan, especially during the take-off operation, can be achieved through the introduction of a Variable Area Fan Nozzle (VAFN). On the given geometry, two potential design spaces were studied and the conceptual designs of two VAFN concepts were created. This paper presents a comparative study between both the concepts following the requirements of different attributes. These involve the performance assessment, structural design study, and a preliminary assessment of the design features for integration into the nacelle or in the core fairing structure. For the comparison, the clean nozzle, without any modulation of the BPD aero lines, was taken as the reference case. The VAFN assessments were carried out on two VAFN positions, over- and under-area, considering the maximum take-off and maximum climb flight conditions respectively. For the selected concepts, CFD trade studies were executed in order to compare the nozzle performance, in which three main governing design parameters i.e. discharge-, thrust performance coefficient, and drag, were examined. This research has received funding from the European Union's 7th Framework Program under grant agreement number 604999.}, language = {en} } @misc{SainHoeschler, author = {Sain, Chetan Kumar and H{\"o}schler, Klaus}, title = {Aerodynamic Assessment of Nozzle Area Variation by Core Fairing Modulation}, series = {CEAS Aeronautical Journal}, volume = {8}, journal = {CEAS Aeronautical Journal}, number = {3}, issn = {1869-5590}, doi = {10.1007/s13272-017-0253-4}, pages = {493 -- 504}, abstract = {Aerodynamic assessment of nozzle area variation by core fairing modulation on the way towards the goals of ACARE 2020 and Flightpath 2050 [1], a next potential step in flight engine technology is to develop engines with by-pass ratios (BPR) far beyond the current levels of 10 to 12. These new engine concepts can have BPRs of up to 20 and require a significant step forward in low pressure system technologies. The European Union supports within the 7th Framework the research activities for these new low pressure systems through the program ENOVAL [2]. Such a new low pressure technology can be achieved through an innovative fan design with a low fan pressure ratio and a radically increased fan diameter compared to the current conventional turbofan engine. The aerodynamic stability of such large fans is most likely very sensitive against backpressure variations. For this reason the backpressure regulation of such large fan, specially during take-off operation, can be achieved through the introduction of a Variable Area Fan Nozzle [VAFN]. This paper describes the aerodynamic study of a particular VAFN concept. This concept offers the variation in fan nozzle throat-area by the displacement of the inner fixed structure (IFS) (also known as core fairing structure). The aim of the assessment was to perform a comparative aerodynamic study at different design configurations. These configurations were derived by varying the design parameters such as the location of section plane (divides the IFS into front and rear block) and the position of the rotational axis. The range of the area change for different flight cases was defined by the engine owner under the ENOVAL program. For each design configuration, the geometries for all the flight cases with their required variation in the nozzle throat area were developed. For the initial study phase the aero assessment a 2D axis-symmetric flow was considered and the airflow from the vent nozzle and core nozzle were included. At this stage, the flight cases with the maximum variation in throat area (e.g. max take-off and top of climb) and the nominal cruise case without area change were studied. Three major performance parameters, the thrust coefficient, nozzle drag coefficient and the after-body drag were calculated. The effects of the gaps and steps (resulting from the overlapping between the IFS segments) on the performance parameters were examined. A comparative result was produced in which the different design parameters of the VAFN were ranked. With the help of few iterations, the best possible design configuration was accessed. At the final stage, the detailed aerodynamic studies on the selected design configuration were performed for the whole range of area variation, including the cruise case with different power loops and the maximum area changes with the variations in the day temperature. [1] Advisory Council for Aviation Research and Innovation in Europe (ACARE) with its targets for CO2 emission- and noise reduction by year 2020 for civil European aircraft industries to be more innovative, sustainable and highly competitive till year 2050 (Flightpath 2050) www.acare4europe.com/. [2] European 7th Framework Program ENOVAL(ENgine mOdule VALidators) http://www.enoval.eu/.}, language = {en} } @inproceedings{KazulaHoeschler, author = {Kazula, Stefan and H{\"o}schler, Klaus}, title = {A Systems Engineering Approach to Variable Intakes for Civil Aviation}, series = {7th European Conference for Aero Nautics and Space Sciences (EUCASS), Milan (Italien), 2017}, booktitle = {7th European Conference for Aero Nautics and Space Sciences (EUCASS), Milan (Italien), 2017}, doi = {10.13009/EUCASS2017-20}, pages = {11}, abstract = {A systems engineering approach to develop variable nacelle intakes for aero engines in civil aviation is presented. The goal of this methodical approach is to find solutions to design problems that can be successfully utilised in aviation without further effort during the certification. By using variable intakes, aircraft and aero engine manufacturers can fulfil their customers' needs for safe, efficient and fast travelling. Therefore, a system shall be installed which is able to modify the nacelle intake contour between two extrema. On the one hand, a sharp thin contour, which produces low drag and allows to fly faster or more efficiently, is optimal during cruise condition. On the other hand, a round thick intake lip is necessary to avoid flow separations with the potential to cause dangerous events during take-off and climb conditions. The utilised systems engineering approach is introduced. The executed steps and methods used for creating and evaluating concept variants for variable intakes are displayed particularly. Those contain the determination and evaluation of requirements and functions, as well as the generation and assessment of concepts. Finally yet importantly, following tasks are presented.}, language = {en} } @misc{GrasseltHoeschlerKazula, author = {Grasselt, David and H{\"o}schler, Klaus and Kazula, Stefan}, title = {A Design Approach for a Coupled Actuator System for Variable Nozzles and Thrust Reverser of Aero Engines}, series = {Proceedings of ISABE 2017, ISABE-2017-21450, Manchester, September 3.-8., 2017}, journal = {Proceedings of ISABE 2017, ISABE-2017-21450, Manchester, September 3.-8., 2017}, publisher = {ISABE}, pages = {11}, language = {en} } @inproceedings{GrasseltHoeschlerSain, author = {Grasselt, David and H{\"o}schler, Klaus and Sain, Chetan Kumar}, title = {Fluid-Structure Interaction With a Fully Integrated Multiphysics Environment}, series = {Proceedings of the ASME Fluids Engineering Division Summer Meeting - 2017, presented at the ASME 2017 Fluids Engineering Division Summer Meeting, July 30-August 3, 2017, Waikoloa, Hawaii, USA, Volume 1B}, booktitle = {Proceedings of the ASME Fluids Engineering Division Summer Meeting - 2017, presented at the ASME 2017 Fluids Engineering Division Summer Meeting, July 30-August 3, 2017, Waikoloa, Hawaii, USA, Volume 1B}, publisher = {ASME}, address = {New York, NY}, isbn = {978-0-7918-5805-9}, doi = {10.1115/FEDSM2017-69078}, pages = {8}, abstract = {The paper is focusing on Fluid-Structure Interaction (FSI) process modelling to look for the aero-elastic equilibrium with commercial software packages. The center of intention is to prove whether Ansys Workbench is capable to handle industrial size FSI applications on the one side and to identify possible excitation regions in the example case on the other. The three steps taken to come to a thermal-enhanced bidirectional fluid-structure approach within a fully integrated (monolithic) multiphysics environment are explained: aerodynamic assessment, thermo-structure mechanical setup and unidirectional coupling, as well as bidirectional coupling. Each subchapter describes the specific challenges, how they are solved and which results can be obtained or expected. The paper is focusing on the setup of a bidirectional process chain and does not set the thematic priority on detailed modelling and its results.}, language = {en} } @misc{KazulaGrasseltMischkeetal., author = {Kazula, Stefan and Grasselt, David and Mischke, Marcel and H{\"o}schler, Klaus}, title = {Preliminary safety assessment of circular variable nacelle inlet concepts for aero engines in civil aviation}, series = {Safety and Reliability - Safe Societies in a Changing World}, journal = {Safety and Reliability - Safe Societies in a Changing World}, publisher = {Taylor \& Francis Group}, address = {London}, isbn = {978-0-8153-8682-7}, pages = {2459 -- 2467}, abstract = {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.}, language = {en} } @inproceedings{KazulaGrasseltHoeschler, author = {Kazula, Stefan and Grasselt, David and H{\"o}schler, Klaus}, title = {Common cause analysis of circular variable nacelle inlet concepts for aero engines in civil aviation}, series = {Proceedings IRF2018: 6th International Conference Integrity-Reliability-Failure, Lisbon/Portugal, 22-26 July 2018}, booktitle = {Proceedings IRF2018: 6th International Conference Integrity-Reliability-Failure, Lisbon/Portugal, 22-26 July 2018}, editor = {Silva Gomes, J. F. and Meguid, Shaker A.}, publisher = {INEGI/FEUP}, address = {Lisbon}, isbn = {978-989-20-8313-1}, pages = {759 -- 770}, abstract = {This paper presents the application of a safe design process within a concept study for variable aero engine inlets. The safety assessment method Common Cause Analysis (CCA), consisting of a Zonal Safety Analysis (ZSA), a Particular Risk Analysis (PRA) and a Common Mode Analysis (CMA), is performed on variable inlet concepts. By the means of the CCA individual failure modes and external events, which can lead to failure conditions, are identified. Potential design adaptations to mitigate these failure conditions are presented.}, language = {en} } @misc{KazulaHoeschler, author = {Kazula, Stefan and H{\"o}schler, Klaus}, title = {Ice detection and protection systems for circular variable nacelle inlet concepts}, series = {Deutscher Luft- und Raumfahrtkongress 2018, Friedrichshafen, 4. bis 6. September 2018}, journal = {Deutscher Luft- und Raumfahrtkongress 2018, Friedrichshafen, 4. bis 6. September 2018}, pages = {1 -- 15}, abstract = {This paper presents the challenge of ice protection within a concept study for variable aero engine inlets in civil aviation. An overview of variable inlet concept groups, ice detection and protection mechanisms is given. These ice protection systems are assigned to the respective inlet concept groups and evaluated regarding economic, functional and safety requirements to determine the most suitable combinations.}, language = {en} } @misc{KazulaRichHoeschleretal., author = {Kazula, Stefan and Rich, Beatrice Monique and H{\"o}schler, Klaus and Woll, Ralf}, title = {Awakening the Interest of High School Pupils in Science, Technology, Engineering and Mathematics Studies and Careers through Scientific Projects}, series = {2018 International Conference on Teaching, Assessment, and Learning for Engineering (TALE), 4-7 December 2018, Wollongong, NSW, Australia}, journal = {2018 International Conference on Teaching, Assessment, and Learning for Engineering (TALE), 4-7 December 2018, Wollongong, NSW, Australia}, publisher = {IEEE}, address = {Piscataway, NJ}, isbn = {978-1-5386-6522-0}, doi = {10.1109/TALE.2018.8615418}, pages = {259 -- 265}, abstract = {This paper presents the application of a scientific project concerning variable aero engine inlets, which was conducted within the scope of a high school course over the period of two years. The motivation of developing variable aero engine inlets with a group of pupils is introduced. The approach that is utilised during that course and its implementation are described. The results and benefits of this project for pupils, supervisor, school and university are summarised, e.g. providing the pupils with necessary knowledge and assisting them with their career choices, potentially resulting in increased enrolment numbers and lower dropout rates in science, technology, engineering and mathematics study programmes. An overview of a follow-up project that enables a larger group of pupils and a yearly implementation of a similar course is given. Within the scope of that course, university students will supervise smaller scientific projects that are conducted by groups of pupils over the period of one semester, providing additional benefits for students' soft skills, e.g. communication and conflict management skills.}, language = {en} } @misc{MhadbiMischkeHoeschleretal., author = {Mhadbi, Beya and Mischke, Marcel and H{\"o}schler, Klaus and Huppertz, Andr{\´e}}, title = {Semi-automatische Erstellung parametrisch-assoziativer 3D CAD-Modelle am Beispiel eines Flug-Kerntriebwerks}, series = {Digitalisierung und Produktentwicklung - vernetzte Entwicklungsumgebungen, 16. Gemeinsames Kolloquium Konstruktionstechnik 2018, Bayreuth, Tagungsband}, journal = {Digitalisierung und Produktentwicklung - vernetzte Entwicklungsumgebungen, 16. Gemeinsames Kolloquium Konstruktionstechnik 2018, Bayreuth, Tagungsband}, publisher = {Universit{\"a}t Bayreuth, Lehrstuhl f{\"u}r Konstruktionslehre und CAD}, address = {Bayreuth}, isbn = {978-3-00-059609-4}, pages = {236 -- 243}, abstract = {Zuk{\"u}nftige Produktentwicklungen werden auf multidisziplin{\"a}re Optimierungen eines virtuellen Modells basieren, da nur sie die Interaktionen zwischen den beteiligten Disziplinen ber{\"u}cksichtigen. 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 f{\"u}r die o.g. Disziplinen relevant sind, zu parametrisieren, d.h. flexibel zu gestalten und eine potenzielle Ver{\"a}nderung der Morphologie bzw. der Abmessungen vorzusehen. Wie eine flexible, f{\"u}r 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 Durchf{\"u}hrung multidisziplin{\"a}rer Optimierung erm{\"o}glicht.}, language = {de} } @inproceedings{MischkeKazulaHoeschler, author = {Mischke, Marcel and Kazula, Stefan and H{\"o}schler, Klaus}, title = {A Comparative Concept Study and Evaluation for New Broadband Noise Absorbing Acoustic Liner Concepts for Civil Aviation}, series = {Proceedings of Global Power and Propulsion Society, Technical Conference 2019, Zurich}, booktitle = {Proceedings of Global Power and Propulsion Society, Technical Conference 2019, Zurich}, pages = {1 -- 9}, abstract = {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.}, language = {en} } @inproceedings{HoeschlerDenggSommerfeld, author = {H{\"o}schler, Klaus and Dengg, Hubert and Sommerfeld, Jonathan}, title = {Adaptive Preliminary-Design workflow for aero engine Secondary Air system cavities with an application case of windage and heat transfer in a roter-stator cavity with axial throughflow}, series = {ASME Turbo Expo 2018: Turbomachinery Technical Conference and Exposition}, booktitle = {ASME Turbo Expo 2018: Turbomachinery Technical Conference and Exposition}, publisher = {The American Society of Mechanical Engineers}, address = {New York, N.Y.}, isbn = {978-0-7918-5110-4}, doi = {10.1115/GT2018-76201}, pages = {12}, abstract = {At the preliminary design stage of theengine design process,the behaviourand efficiency of different engine designs are investigated and evaluated in order to find a best matching design for a set ofengine objectives and requirements.The prediction of critical part temperaturesas well as the reduction of the uncertainty of these predictions is decisive to bid a competitive technology in aerospace technology. Automated workflows and Design of Experiments (DOE) are widely used to investigate large number of designs and to find an optimized solution.Nowadays, technological progress in computational power as well as new strategies for data handling and management enables the implementation of large DOEs and multi-objective optimizations in less time, whichalso allows the consideration of more detailed investigations in early design stages. This paper describes an approach for apreliminary-design workflow that implementsadaptivemodelling and evaluation methodsfor cavities in the secondary air system (SAS). The starting point for the workflow is a parametric geometry model defining the rotating and static components. The flow network withintheSAS isautomatically recognizedand CFD and Thermal-FE modelsare automatically generatedusing a library of generic models. Adaptiveevaluation algorithms are developed and used to predict values for structural, air system and thermal behaviour. Furthermore, these models and evaluation techniques can be implemented in a DOE to investigate the impact of design parameters onthe predicted values. The findings from the automated studies can beused to enhance the boundary conditions of actual design models in later design stages. A designinvestigation on a rotor-stator cavity with axial through flow has been undertaken usingthe proposedworkflow to extract windage, flow field and heat transfer informationfrom adiabatic CFD calculations for use in thermal modelling. A DOE has been set up to conduct a sensitivity analysis of the flow field properties and to identify the impact of the design parameters. Additionally,impacts on the distribution of the flow field parametersalong the rotating surface are recognized, which offers a better prediction for local effects in the thermal FE model.}, language = {en} } @misc{KazulaHoeschler, author = {Kazula, Stefan and H{\"o}schler, Klaus}, title = {A systems engineering approach to variable intakes for civil aviation}, series = {Proceedings of the Institution of Mechanical Engineers. Part G, Journal of Aerospace Engineering}, volume = {234(2020)}, journal = {Proceedings of the Institution of Mechanical Engineers. Part G, Journal of Aerospace Engineering}, number = {10}, issn = {2041-3025}, doi = {10.1177/0954410019836903}, pages = {1721 -- 1729}, abstract = {A systems engineering approach to develop variable nacelle intakes for aero engines in civil aviation is presented. The goal of this methodical approach is to find solutions to design problems that can be successfully utilised in aviation without further effort during the certification. By using variable intakes, aircraft and aero engine manufacturers can fulfil their customers' needs for safe, efficient and fast travelling. Therefore, a system shall be installed which is able to modify the nacelle intake contour between two extrema. On the one hand, a sharp thin contour, which produces low drag and allows to fly faster or more efficiently, is optimal during cruise condition. On the other hand, a round thick intake lip is necessary to avoid flow separations with the potential to cause dangerous events during take-off and climb conditions. The utilised systems engineering approach is introduced. The executed steps and methods used for creating and evaluating concept variants for variable intakes are displayed particularly. Those contain the determination and evaluation of requirements and functions as well as the generation and assessment of concepts. Finally, yet importantly, following tasks are presented.}, language = {en} } @misc{KazulaHoeschler, author = {Kazula, Stefan and H{\"o}schler, Klaus}, title = {Ice detection and protection systems for circular variable nacelle inlet concepts}, series = {CEAS Aeronautical Journal}, volume = {11}, journal = {CEAS Aeronautical Journal}, number = {1}, issn = {1869-5590}, doi = {10.1007/s13272-019-00413-1}, pages = {229 -- 248}, abstract = {This paper presents the challenge of ice protection within a concept study for variable pitot inlets of aero engines in transonic and supersonic civil aviation. An overview of variable inlet concept groups that adjust the inlet geometry by rigid segment repositioning, elastic surface deformation, or boundary layer control is given. Ice detection mechanisms and various pneumatic, fluid, as well as electric ice protection systems are presented. These ice protection systems are assigned to the respective inlet concept groups and evaluated regarding economic, functional, and safety requirements by means of pairwise comparison and weighted point rating to determine the most suitable combinations.}, language = {en} } @misc{KazulaWoellnerGrasseltetal., author = {Kazula, Stefan and W{\"o}llner, Mark and Grasselt, David and H{\"o}schler, Klaus}, title = {Parametric Design Study on Aerodynamic Characteristics of Variable Pitot Inlets for Transonic and Supersonic Civil Aviation}, series = {MATEC Web of Conferences : Proceedings of the 9th EASN International Conference on Innovation in Aviation \& Space}, volume = {304}, journal = {MATEC Web of Conferences : Proceedings of the 9th EASN International Conference on Innovation in Aviation \& Space}, issn = {2261-236X}, doi = {10.1051/matecconf/201930402017}, pages = {8}, abstract = {This paper reveals the influence of selected geometric parameters on the aerodynamic performance of circular variable aero engine inlets in transonic and supersonic civil aviation. The trade-off in inlet design and aerodynamic evaluation parameters are presented. The approach to investigate the dependencies between the aerodynamic and geometric parameters at different flight conditions by means of a parametric design study is introduced. The dependencies of inlet drag and efficiency from geometric parameters at flight speeds of Mach 0.95 up to Mach 1.6 are identified. Although entailing additional weight, the inlet length represents the parameter with the highest potential for drag reduction by up to 50\% in the selected design space. Ideal geometries for variable pitot inlets are determined. After considering weight, their potential range benefit nearly disappears for subsonic applications, but remains above 20\% for supersonic flight at Mach 1.6.}, language = {en} } @misc{KazulaMischkeKoenigetal., author = {Kazula, Stefan and Mischke, Marcel and K{\"o}nig, Paul and H{\"o}schler, Klaus}, title = {Evaluation of Variable Pitot Inlet Concepts for Transonic and Supersonic Civil Aviation}, series = {MATEC Web of Conferences : Proceedings of the 9th EASN International Conference on Innovation in Aviation \& Space}, volume = {304}, journal = {MATEC Web of Conferences : Proceedings of the 9th EASN International Conference on Innovation in Aviation \& Space}, issn = {2261-236X}, doi = {10.1051/matecconf/201930402016}, pages = {8}, abstract = {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.}, language = {en} } @misc{KazulaWoellnerGrasseltetal., author = {Kazula, Stefan and W{\"o}llner, Mark and Grasselt, David and H{\"o}schler, Klaus}, title = {Parametric design and aerodynamic analysis of circular variable aero engine inlets for transonic and supersonic civil aviation}, series = {Proceedings of the 24th ISABE Conference : ISABE 2019-24018}, journal = {Proceedings of the 24th ISABE Conference : ISABE 2019-24018}, address = {Canberra}, pages = {39}, abstract = {This paper focusses on the challenge of determining the ideal inlet geometries within a concept study for variable pitot aero engine inlets in transonic and supersonic civil aviation. The trade-off in inlet design and the geometric parameters of inlets for different Mach numbers are introduced. The utilised process of the parametric design study and its implementation are presented. The dependencies of inlet drag and occurrence of flow separation from geometric parameters are examined. The ideal inlet geometries are identified to determine the potential aerodynamic benefit of using variable pitot inlets. The comparison of the identified geometries with the reference reveals a significant drag reduction at the investigated flight speeds of Mach 0.95, 1.3 and 1.6. While the drag reduction potentially leads to decreased fuel consumption and increased flight range, the application of variable inlet systems entails additional weight and complexity. By means of a simplified Breguet range equation, the benefit of using variable pitot inlets has been determined. For an additional weight of 500 kg per variable inlet, the range benefit nearly disappears for subsonic applications up to Mach 0.95, while a range benefit of over 20\% remains for supersonic applications at Mach 1.6.}, language = {en} } @misc{KoenigMischkePohletal., author = {K{\"o}nig, Paul and Mischke, Marcel and Pohl, Michael and Kazula, Stefan and H{\"o}schler, Klaus}, title = {Concept Development and Evaluation for a Broadband Noise Absorbing Acoustic Liner Concept for Aviation}, series = {24th International Society For Air Breathing Engines (ISABE-2019-24261), 22.-27. September 2019}, journal = {24th International Society For Air Breathing Engines (ISABE-2019-24261), 22.-27. September 2019}, abstract = {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.}, language = {en} } @misc{KazulaWoellnerGrasseltetal., author = {Kazula, Stefan and W{\"o}llner, Mark and Grasselt, David and H{\"o}schler, Klaus}, title = {Ideal Geometries and Potential Benefit of Variable Pitot Inlets for Subsonic and Supersonic Business Aviation}, series = {8TH EUROPEAN CONFERENCE FOR AERONAUTICS AND SPACE SCIENCES (EUCASS)}, journal = {8TH EUROPEAN CONFERENCE FOR AERONAUTICS AND SPACE SCIENCES (EUCASS)}, doi = {10.13009/EUCASS2019-314}, abstract = {The challenge of determining ideal inlet geometries for variable pitot aero engine inlets in transonic and supersonic civil aviation is presented. The trade-off in inlet design and the geometric inlet parameters are introduced. By means of a parametric design study, feasible inlet geometries for variable inlets are identified and the potential aerodynamic benefit of using variable pitot inlets for flight speeds from Mach 0.95, 1.3 up to 1.6 is examined. After considering the additional weight of variable inlets, for instance due to required actuators, a remaining range benefit of over 20\% at a flight speed of Mach 1.6 is determined.}, language = {en} } @misc{MischkeKazulaHoeschler, author = {Mischke, Marcel and Kazula, Stefan and H{\"o}schler, Klaus}, title = {Preliminary Safety Assessment on System Design Level for Broadband Acoustic Liner Concepts for Aviation}, series = {Proceedings of the 9th EASN International Conference on Innovation in Aviation \& Space}, journal = {Proceedings of the 9th EASN International Conference on Innovation in Aviation \& Space}, address = {Athen}, doi = {10.1051/matecconf/201930404010}, pages = {8}, abstract = {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.}, language = {en} } @misc{YagciHoeschlerPannieretal., author = {Yagci, Tolga and H{\"o}schler, Klaus and Pannier, Stephan and Ende, Sven von}, title = {A Structural Health Monitoring (SHM) approach using a multidisciplinary digital twin for high-pressure turbine discs in civil aviation}, series = {Proceedings IRF2020 : 7th International Conference Integrity-Reliability-Failur, Funchal/Portugal, 6-10 Sep 2020}, journal = {Proceedings IRF2020 : 7th International Conference Integrity-Reliability-Failur, Funchal/Portugal, 6-10 Sep 2020}, editor = {Silva Gomes, J. F. and Meguid, Shaker A.}, isbn = {978-989-54756-1-2}, pages = {491 -- 502}, abstract = {The health status of an aircraft rotating turbine component depends heavily on the flight profiles flown by the operator. In contrast of this dependency, the declared Low Cycle Fatigue (LCF) life is typically determined for a designed flight profile, which is representative for most fleet flight profiles. A significant improvement in component utilisation without compromising safety can be achieved by using Engine Health Monitoring (EHM) data in order to monitor the LCF life by means of a digital engine twin. This paper is focussed on the development of a digital twin for a Civil Small and Medium Engine (CSME) and the structural health monitoring (SHM) of LCF life. The digital twin combines analytical models from multiple disciplines such as system performance, thermals and structures and aims to connect operational data to the component's accumulated damage. This enables individual monitoring of the component's health status, and prediction of Remaining Useful Life (RUL).}, language = {en} } @misc{KazulaHoeschler, author = {Kazula, Stefan and H{\"o}schler, Klaus}, title = {Evaluation of variable pitot inlet concepts for transonic and supersonic civil aviation}, series = {Aircraft Engineering and Aerospace Technology}, volume = {92}, journal = {Aircraft Engineering and Aerospace Technology}, number = {6}, issn = {0002-2667}, doi = {10.1108/AEAT-11-2019-0225}, pages = {807 -- 815}, abstract = {Purpose - This paper aims to describe the selection of the ideal variable inlet concept group by using results of aerodynamic investigations, system safety analyses and integration studies. Design/methodology/approach - 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. Findings - By means of this evaluation, the concept group that adjusts the inlet geometry by rigid segment repositioning is identified as most suitable concept group. Originality/value - 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.}, language = {en} } @misc{KazulaWoellnerHoeschler, author = {Kazula, Stefan and W{\"o}llner, Mark and H{\"o}schler, Klaus}, title = {Identification of efficient geometries for variable pitot inlets for supersonic transport}, series = {Aircraft Engineering and Aerospace Technology}, volume = {92}, journal = {Aircraft Engineering and Aerospace Technology}, number = {7}, issn = {0002-2667}, doi = {10.1108/AEAT-11-2019-0228}, pages = {981 -- 992}, abstract = {Purpose - This paper aims to reveal the influence of selected geometric parameters on the aerodynamic performance of circular variable aero engine inlets in transonic and supersonic civil aviation. Design/methodology/approach - The trade-off in inlet design and aerodynamic evaluation parameters is presented. The approach to investigate the dependencies between the aerodynamic and geometric parameters at different flight conditions by means of a parametric design study is introduced. Findings - The dependencies of inlet drag and efficiency from geometric parameters at flight speeds of Mach 0.95 up to Mach 1.6 are identified. Although entailing additional weight, the inlet length represents the parameter with the highest potential for drag reduction by up to 50\% in the selected design space. Ideal geometries for variable pitot inlets are determined. After considering weight, their potential range benefit nearly disappears for subsonic applications, but remains above 20\% for supersonic flight at Mach 1.6. Originality/value - Hence, the technology of circular variable pitot inlets for supersonic transport aircraft could be a way to achieve the ambitious ecological, safety and economic goals for future civil aviation.}, language = {en} } @misc{KazulaHoeschler, author = {Kazula, Stefan and H{\"o}schler, Klaus}, title = {Review of Variable Leading Edge Patents for Aircraft Wings and Engine Inlets and Their Relevance for Variable Pitot Inlets in Future Supersonic Transport}, series = {Deutscher Luft- und Raumfahrtkongress 2020, Online, 1. bis 3. September 2020}, journal = {Deutscher Luft- und Raumfahrtkongress 2020, Online, 1. bis 3. September 2020}, abstract = {The motivation for designing variable pitot inlets for future supersonic transport (SST) is explained. A comprehensive overview of existing technological solutions for variable leading edges of aircraft wings and engines inlets is given. The advantages and limitations of over 80 solutions, as well as their relevance for application on variable pitot inlets for SST are analysed. These analyses emphasis challenges of existing solution options concerning design methodologies, level of detail and experience with a technology.}, language = {en} } @misc{KazulaHoeschler, author = {Kazula, Stefan and H{\"o}schler, Klaus}, title = {A Variable Pitot-Inlet Concept for Supersonic Aviation}, series = {Global Power \& Propulsion Society GPPS Chania20, Online, 7th - 9th September 2020}, journal = {Global Power \& Propulsion Society GPPS Chania20, Online, 7th - 9th September 2020}, issn = {2504-4400}, doi = {10.33737/gpps20-tc-49}, pages = {10}, abstract = {An overview of aero-engine inlets, the design process in aviation and a safe design approach for academic studies is provided. By means of a safe design approach, a variable inlet concept is developed up to technology readiness level (TRL) 3 and described. The application of safety and reliability methods, aerodynamic and structural analyses, as well as functional demonstrators proves the feasibility of the present variable inlet concept and highlights its potential for application in future supersonic transport (SST).}, language = {en} } @misc{MischkePohlHoeschleretal., author = {Mischke, Marcel and Pohl, Michael and H{\"o}schler, Klaus and Huppertz, Andr{\´e}}, title = {A Holistic Approach for the Generic Preliminary Design of Axial Compressor and Turbine Annulus Contours}, series = {Conference Paper of the DLRK 2020}, volume = {Deutscher Luft- und Raumfahrtkongress 2020}, journal = {Conference Paper of the DLRK 2020}, publisher = {Deutsche Gesellschaft f{\"u}r Luft- und Raumfahrt - Lilienthal-Oberth e.V.}, address = {Bonn}, doi = {https://doi.org/10.25967/530097}, url = {http://nbn-resolving.de/urn:nbn:de:101:1-2020121112463561159960}, pages = {12}, abstract = {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.}, language = {en} } @misc{MischkePohlHoeschleretal., author = {Mischke, Marcel and Pohl, Michael and H{\"o}schler, Klaus and Huppertz, Andr{\´e}}, title = {GAS PATH DESIGNER - zeiteffiziente Vorauslegung von Triebwerks-Ringr{\"a}umen und zus{\"a}tzlichen Strukturen}, series = {Conference Paper des Deutscher Luft- und Raumfahrtkongress 2020}, volume = {Deutscher Luft- und Raumfahrtkongress 2020}, journal = {Conference Paper des Deutscher Luft- und Raumfahrtkongress 2020}, publisher = {Deutsche Gesellschaft f{\"u}r Luft- und Raumfahrt - Lilienthal-Oberth e.V.}, address = {Bonn}, doi = {https://doi.org/10.25967/530098}, url = {http://nbn-resolving.de/urn:nbn:de:101:1-2020121112494640076557}, pages = {10}, abstract = {Der Beginn einer jeden Triebwerksentwicklung startet mit der Auslegung des Ringraumes des Prim{\"a}rgasstromes. Hier m{\"u}ssen einige vorl{\"a}ufige aber auch grundlegende Entscheidungen zu Entwurfsparametern wie Eintrittsquerschnitte, Subsysteml{\"a}ngen, axiale Stufenanzahl in Verdichter und Turbine, usw. definiert werden. F{\"u}r die Vorauslegung sollte die Palette an anf{\"a}nglichen Entwurfsparametern so gering wie m{\"o}glich gehalten werden, um die Menge an m{\"o}glichen Ringraumentw{\"u}rfen nicht fr{\"u}hzeitig einzuschr{\"a}nken. Dieses Paper pr{\"a}sentiert das Vorauslegungswerkzeug „Gas Path Designer" (GPD), welches in der Lage ist Ringraumentw{\"u}rfe f{\"u}r Turbotriebwerke {\"u}ber zeiteffiziente Berechnungsmethoden in k{\"u}rzester Zeit bereitzustellen. Das Interface bietet eine Auswahl an Einstellungen, um die genannten Variationsm{\"o}glichkeiten zu unterst{\"u}tzen. Der Aufbau ist {\"u}bersichtlich, um im Rahmen grundlegender konzeptorientierter Gespr{\"a}che mit dem Kunden eine schnelle und beidseitig nachvollziehbare Variation und Visualisierung des Konzeptentwurfes zu erm{\"o}glichen. Des Weiteren k{\"o}nnen die erhaltenen Ringraumstrukturen der Triebwerksentw{\"u}rfe als Leitstruktur f{\"u}r CAD-Programme sowie weiterf{\"u}hrende Optimierungsstrategien genutzt werden.}, language = {de} } @misc{NeubauerGensslerRadmannetal., author = {Neubauer, Moritz and Genßler, Julia and Radmann, Vincent and Kohlenberg, Fleming and Pohl, Michael and B{\"o}hme, Kurt and Knobloch, Karsten and Sarradj, Ennes and H{\"o}schler, Klaus and Modler, Niels and Enghardt, Lars}, title = {Experimental and Numerical Investigation of Novel Acoustic Liners and Their Design for Aero-Engine Applications}, series = {Aerospace}, volume = {10}, journal = {Aerospace}, number = {1}, issn = {2226-4310}, doi = {10.3390/aerospace10010005}, abstract = {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.}, language = {en} } @misc{NeubauerPohlKucheretal., author = {Neubauer, Moritz and Pohl, Michael and Kucher, Michael and B{\"o}hm, Robert and H{\"o}schler, Klaus and Modler, Niels}, title = {DMA of TPU Films and the Modelling of Their Viscoelastic Properties for Noise Reduction in Jet Engines}, series = {Polymers}, volume = {14}, journal = {Polymers}, number = {23}, issn = {2073-4360}, doi = {10.3390/polym14235285}, abstract = {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.}, language = {en} } @phdthesis{Kazula, author = {Kazula, Stefan}, title = {Variable Pitot-Triebwerkseinl{\"a}sse f{\"u}r kommerzielle {\"U}berschallflugzeuge - Konzeptstudie mittels eines Entwicklungsansatzes f{\"u}r sichere Produkte}, publisher = {Springer Vieweg}, address = {Wiesbaden}, isbn = {978-3-658-35455-8}, doi = {10.1007/978-3-658-35456-5}, pages = {XXX, 373}, language = {de} } @misc{KazulaRichHoeschleretal., author = {Kazula, Stefan and Rich, Beatrice Monique and H{\"o}schler, Klaus and Woll, Ralf}, title = {Interest High School Students in STEM Studies, while Preparing STEM Students for Leading Positions}, series = {2021 IEEE Global Engineering Education Conference}, volume = {2021}, journal = {2021 IEEE Global Engineering Education Conference}, isbn = {978-1-7281-8478-4}, doi = {10.1109/EDUCON46332.2021.9454011}, pages = {910 -- 914}, language = {en} } @misc{KazulaHoeschler, author = {Kazula, Stefan and H{\"o}schler, Klaus}, title = {Sustainable Supersonic Transport: a Case Study on Variable Pitot Inlets}, series = {9th European Conference for Aeronautics and Space Sciences (Eucass)}, journal = {9th European Conference for Aeronautics and Space Sciences (Eucass)}, doi = {10.13009/EUCASS2022-4600}, pages = {14}, language = {en} } @misc{VaratharajuluPurgunanAsliNaccietal., author = {Varatharajulu Purgunan, Gokkul Raj and Asli, Majid and Nacci, Teodosio and Misul, Daniela Anna and Salvadori, Simone and Stathopoulos, Panagiotis}, title = {Film Cooling Modeling in a Turbine Working under the Unsteady Exhaust Flow of Pulsed Detonation Combustion}, series = {Energies}, volume = {17}, journal = {Energies}, number = {6}, issn = {1996-1073}, doi = {10.3390/en17061312}, pages = {1 -- 20}, abstract = {Pressure gain combustors (PGCs) have demonstrated significant advantages over conventional combustors in gas turbine engines by increasing the thermal efficiency and reducing the pollution emission level. PGCs use shock waves to transfer energy which contributes to the increase in outlet total pressure. One of the major obstacles in the actual implementation of PGCs in the gas turbine cycle is the exploitation of the highly unsteady flow of the combustor outlet with the downstream turbine. Because of the higher outlet temperature from the PGCs, the turbine blade cooling becomes essential. Due to the highly fluctuating unsteady flow of PGCs, 3D CFD simulation of turbines becomes very expensive. In this work, an alternative approach of using a 1D unsteady Euler model for the turbine is proposed. One of the novel aspects of this paper is to implement the turbine blade cooling in the unsteady 1D Euler model. The main parameters required for the turbine blade cooling are the cooling air mass flow rate, temperature, and pressure. Due to the introduction of coolant flow, the blades are no longer adiabatic and the mass flow rate across the turbine is not constant. Comparing the 1D Euler results against zero-dimensional calculation and 3D CFD approach showed a very good match for both steady and unsteady simulations confirming the applicability of the 1D method.}, language = {en} } @misc{KondaSharmaMathiazhagan, author = {Konda, Karunakar Reddy and Sharma, Dikshant and Mathiazhagan, Akilan}, title = {Quantitative assessment of cooling methods for electrical machines in aircraft drives}, series = {IEEE Access}, volume = {12}, journal = {IEEE Access}, publisher = {IEEE}, address = {New York}, issn = {2169-3536}, doi = {10.1109/ACCESS.2024.3517319}, pages = {192768 -- 192785}, abstract = {Transformation of the aviation sector towards climate-neutral solutions such as electrification is urgent. Aviation electrification requires reasoned selection of suitable technologies which has to meet strict requirements and standards. Cooling of electrical components plays a vital role in the sizing and overall performance of the electrical drive system and must achieve high effectiveness and reliability at low weight. Three cooling methods - air cooling, direct slot cooling and cooling jacket - are sized for a 300 kW commuter aircraft (CS23) all-electric propulsion system. They are further evaluated quantitatively for weight, drag, reliability and effectiveness in a conservative assessment. A lumped parameter thermal network (LPTN) approach is utilized to assess and evaluate the thermal performance of the cooling systems. The LPTN model served as the basis to determine the temperature limits and capabilities of the cooling system which are then utilized to size the auxiliary components. Reliability is assessed via fault tree analysis, drag via scoop inlet characteristics and effectiveness via the heat load dissipated per weight of the system and the required cooling power per mechanical power. Cooling jacket achieves the highest effectiveness closely followed by slot cooling. Air cooling proves to be most reliable and lightest.}, language = {en} } @misc{PurgunanAsliKlopschetal., author = {Purgunan, Gokkul Raj Varatharajulu and Asli, Majid and Klopsch, Roman and Meister, Josh and Stathopoulos, Panagiotis}, title = {A Reduced order methodology for optimizing turbine expanders working with rotating detonation combustors}, series = {ASME Turbo Expo 2024: Turbomachinery Technical Conference and Exposition}, volume = {Cycle Innovations 2024}, journal = {ASME Turbo Expo 2024: Turbomachinery Technical Conference and Exposition}, publisher = {The American Society of Mechanical Engineers}, isbn = {978-0-7918-8797-4}, doi = {10.1115/GT2024-126249}, pages = {1 -- 13}, abstract = {Redesigning a gas turbine cycle with creative concepts is one of the most critical possibilities for achieving a significant increase in efficiency. Pressure Gain Combustion (PGC) can be used in place of conventional deflagration combustion since PGC contributes to a considerable gain in thermal efficiency while also emitting low NOx levels. One of the major challenges of PGC is the turbine integration to the outlet of the combustor due to the unsteady turbine inflow conditions. This unsteady exhaust flow causes turbomachinery components to operate under fluctuating off-design conditions which in turn, reduces their performance. In this work, the turbine integration to the Rotating Detonation Combustor (RDC) and an optimization methodology for the turbine are discussed. Due to the highly fluctuating unsteady flow of RDC, three-dimensional CFD simulation of turbine becomes very expensive, specifically if it is considered as the objective function evaluator in an optimization process. Thus, an alternative approach of using one-dimensional unsteady Euler model for the turbine is adopted. A two-stage axial turbine is optimized considering unsteady flow features of a hydrogen-air RDC to minimize the entropy generation. When compared to the baseline design, the optimized turbine shows a nearly 2.6\% reduction in entropy generation.}, language = {en} } @misc{KoenigMuellerHoeschler, author = {K{\"o}nig, Paul and M{\"u}ller, Phillip and H{\"o}schler, Klaus}, title = {Assessment of (hybrid)-electric drive-train architectures for future aircraft applications}, series = {Journal of Physics: Conference Series}, volume = {2526}, journal = {Journal of Physics: Conference Series}, issn = {1742-6596}, doi = {10.1088/1742-6596/2526/1/012023}, abstract = {Future regional aircraft and propulsion systems will have to address both a growing market and stricter environmental constraints. Besides the increase of component efficiencies, the technological transformation from conventional to (hybrid)-electric propulsion systems represents a paradigm shift with great potential for the aviation industry. In this context, economic, market-relevant as well as technological boundary conditions for the electrical and mechanical components are developed in this paper for a reference regional aircraft and are based on current research results from different institutions. The propulsion performance analysis of a conventional turboprop is compared and evaluated with a serial-hybrid and a fully-electric configuration (both battery-electric), status today as well as status ~2035, as an example, whereby the presented process can also be applied to other hybrid configurations too. An energy-optimised propulsion and operating concept is derived with regard to minimum resulting system weight. The results of this analysis help to define necessary boundary conditions for future subsystem investigations and identify key research items, especially in the field of the battery.}, language = {en} } @misc{SharmaMedinaMendezSchmidtetal., author = {Sharma, Dikshant and Medina M{\´e}ndez, Juan Ali and Schmidt, Heiko and Cremer, Tilman}, title = {Seasonal cold storage with borehole heat exchangers: an application study using numerical simulations}, series = {Tagungsband des Jahrestreffens der DECHEMA-Fachgruppen Computational Fluid Dynamics und W{\"a}rme- und Stoff{\"u}bertragung, 6.-8. M{\"a}rz 2023, Frankfurt am Main, Deutschland}, journal = {Tagungsband des Jahrestreffens der DECHEMA-Fachgruppen Computational Fluid Dynamics und W{\"a}rme- und Stoff{\"u}bertragung, 6.-8. M{\"a}rz 2023, Frankfurt am Main, Deutschland}, publisher = {DECHEMA e.V.}, address = {Frankfurt am Main}, pages = {18 -- 19}, language = {en} } @misc{KazulaHoeschler, author = {Kazula, Stefan and H{\"o}schler, Klaus}, title = {Review of variable leading-edge patents for aircraft wings and engine inlets and their relevance for variable pitot inlets in future supersonic transport}, series = {CEAS Aeronautical Journal}, volume = {12}, journal = {CEAS Aeronautical Journal}, number = {3}, issn = {1869-5582}, doi = {10.1007/s13272-021-00520-y}, pages = {685 -- 700}, abstract = {The motivation for designing variable pitot inlets for future supersonic transport (SST) is explained. A comprehensive overview of existing technological solutions for variable leading edges of aircraft wings and engine inlets is given. The advantages and limitations of over 80 solutions, as well as their relevance for application on variable pitot inlets for SST are described. The challenges of existing solution options concerning design methodologies, level of detail, and experience with a technology are identified.}, language = {en} } @misc{KoenigHoeschlerHaridasu, author = {K{\"o}nig, Paul and H{\"o}schler, Klaus and Haridasu, Venkata Brahma Teja}, title = {Surface Heat Exchanger Assessment for Battery Powered Aircrafts}, series = {AIAA AVIATION Forum, San Diego, 2023}, journal = {AIAA AVIATION Forum, San Diego, 2023}, publisher = {American Institute of Aeronautics and Astronautics}, doi = {10.2514/6.2023-4534}, pages = {1 -- 13}, abstract = {The thermal management system represents a major challenge for a sustainable transformation of aviation industry from conventional to (hybrid)-electric propulsion. Although component efficiencies of motors, generators, power electronics and batteries are much higher compared to conventional gas turbines, heat dissipation is a challenge if flight characteristics are not to be compromised by massive drag growth. One solution is provided by structural surface heat exchangers, which use the aircraft's wetted surface to reject heat to the environment. Using the temperature-sensitive battery, the potential for fuselage-integrated surface heat exchangers will be evaluated. For this purpose, different flight conditions: take-off, climb, cruise and descent; operational concepts: battery-assisted take-off, battery-assisted climb and recuperative descent, and normal and hot day flight cycles will be investigated using a battery-hybridized reference flight of a Saab 340. A method for calculating reversible and irreversible heat fluxes in the battery is presented and used as a quantitative measure. The theoretical suitability of surface heat exchangers for battery heat rejection can be demonstrated for various flight conditions. Critical design points are not only the take-off but also the battery-assisted climb as well as a too power demanding recuperation during descent. The findings obtained are suitable for use in optimizing operating concepts, identifying suitable charging currents, and for transferability to different aircraft sizes as a function of their take-off weight.}, language = {en} } @misc{KimAsliHoeschler, author = {Kim, Dogsuk and Asli, Majid and H{\"o}schler, Klaus}, title = {On the Potentials of the Integration of Pressure Gain Combustion with a Hybrid Electric Propulsion System}, series = {Aerospace}, volume = {10}, journal = {Aerospace}, number = {8}, issn = {2226-4310}, doi = {10.3390/aerospace10080710}, pages = {1 -- 17}, abstract = {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.}, language = {en} } @misc{KoenigSharmaKondaetal., author = {K{\"o}nig, Paul and Sharma, Dikshant and Konda, Karunakar Reddy and Xie, Tianxiao and H{\"o}schler, Klaus}, title = {Comprehensive Review on Cooling of Permanent Magnet Synchronous Motors and Their Qualitative Assessment for Aerospace Applications}, series = {Energies}, volume = {16}, journal = {Energies}, number = {22}, issn = {1996-1073}, doi = {10.3390/en16227524}, abstract = {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.}, language = {en} } @misc{AsliKoenigSharmaetal., author = {Asli, Majid and K{\"o}nig, Paul and Sharma, Dikshant and Pontika, Evangelia and Huete, Jon and Konda, Karunakar Reddy and Mathiazhagan, Akilan and Xie, Tianxiao and H{\"o}schler, Klaus and Laskaridis, Panagiotis}, title = {Thermal management challenges in hybrid-electric propulsion aircraft}, series = {Progress in Aerospace Sciences}, volume = {144}, journal = {Progress in Aerospace Sciences}, issn = {1873-1724}, doi = {10.1016/j.paerosci.2023.100967}, pages = {1 -- 29}, abstract = {The utilization of hybrid electric propulsion concept in aviation offers a viable solution to address the limitations posed by the relatively low energy density of batteries in fully electric aviation. These hybrid systems enable the aircraft to achieve a significant range while simultaneously minimizing carbon emissions. While the individual components of a Hybrid Electric Propulsion (HEP) system, such as electric motors and batteries, are designed with high efficiency, their integration presents a significant challenge in the realm of thermal management. Designing an efficient system for managing the substantial waste heat generated by heat sources and effectively transferring it to heat sinks during various flight phases is a complex task. This challenge becomes even more critical as the design must adhere to system weight limits and prioritize aviation safety considerations. In this review article, we performed a systematic review of the challenges related to the key elements in a thermal management system. These elements encompass every component or subsystem that contributes to the thermal management of a generic hybrid-electric propulsion system. This includes electric motors and generators, batteries, heat exchangers, power transmission systems, power distribution systems, storages, fuel cells, cooling fluids and pipes, control system, pumps and fans. Following the identification of the challenges, the paper provides a comprehensive summary of the existing solutions that have been offered and pursued by the community to address the challenges. Furthermore, the paper also discusses emerging technologies related to each element, highlighting their potential in overcoming these challenges.}, language = {en} } @misc{AsliPatkarHoeschler, author = {Asli, Majid and Patkar, Siddharth and H{\"o}schler, Klaus}, title = {Investigation on the effects of blade leading-edge protuberances on the aerodynamic performance of an axial transonic compressor}, series = {15th European Conference on Turbomachinery Fluid dynamics \& Thermodynamics}, journal = {15th European Conference on Turbomachinery Fluid dynamics \& Thermodynamics}, doi = {10.29008/ETC2023-229}, abstract = {Leading-edge protuberances inspired by humpback whales have been proven to be effective in delaying dynamic stall and post-stall regime of two-dimensional airfoils while causing a performance penalty in the pre-stall regime. Basically, this leading-edge modification acts as a vortex generator to split the separation region over the blade into multiple smaller regions. In this work, different sinusoidal wavy leading shapes are applied to a transonic compressor rotor blade row to evaluate the technique's effectiveness from a compressor performance point of view. The compressor characteristic maps have been compared to the baseline case, which shows how the compressor pressure ratio and efficiency are affected by the leading-edge modifications. The compressor stability margin has also been studied, and a detailed discussion of the flow over the compressor blades is provided.}, language = {en} } @misc{XieMathiazhaganBarkowskietal., author = {Xie, Tianxiao and Mathiazhagan, Akilan and Barkowski, Daniel and Starick, Tommy and Berg, Heinz Peter and H{\"o}schler, Klaus}, title = {Comparison of convective heat transfer in metal foam-filled channels of three different cross-sections}, series = {Numerical Heat Transfer, Part A: Applications}, volume = {85}, journal = {Numerical Heat Transfer, Part A: Applications}, number = {2}, issn = {1521-0634}, doi = {10.1080/10407782.2023.2181892}, pages = {222 -- 236}, abstract = {This work introduces a new approach of analyzing convective heat transfer in porous medium by considering the foam structure as a type of fin. It provides the resulting heat transfer characteristics for the design of a longitudinally flowed tube bundle reformer used for the Micro Gas Turbine Solid Oxide Fuel Cell (MGT-SOFC) hybrid process. Owing to a limited experimental database available in literature for the above-mentioned situation, a physical model is initially introduced for a channel flow configuration between two large flat plates using a commercial PDE solver. This model is then validated with experimental results available in literature. A comparison with theoretical solutions is also conducted. Later, this model is modified/adapted for a pipe flow configuration. The physical model for a channel with representative cross-section shape of a longitudinally flowed tube bundle is more complex and is therefore built in a commercial CFD-Solver. A comparative study of the heat transfer behavior in channels of different cross-sections is performed based on a new dimensionless correlation, whose physical coherence with fin efficiency is explained and mathematically proved. The applicability of the heat transfer correlation from one cross-sectional shape to the other are discussed. The proposed new treatment of the porous medium as a fin structure considerably simplifies the heat transfer analysis in porous medium by the clear physical meaning behind fin efficiency and Biot number. This relationship contributes to a better understanding of the heat heat transfer characteristics in porous media in contrast to the correlation between Nusselt number and Reynolds number. Furthermore, this correlation enables a direct comparison between foam structures of different parameters because the fin efficiency is always between 0 and 1. The strong physical background of new correlations also enhances the reliability and plausibility at characterizing and designing the metal foam for heat transfer enhancement.}, language = {en} } @misc{XieRachowRakhietal., author = {Xie, T. and Rachow, F. and Rakhi, undefined and Berg, H. P. and H{\"o}schler, K.}, title = {Heat transfer analysis of a tube-in-tube steam reformer for the application of MGT-SOFC hybrid process}, series = {Numerical Heat Transfer, Part A: Applications}, journal = {Numerical Heat Transfer, Part A: Applications}, publisher = {Taylor\&Francis}, issn = {1040-7782}, doi = {10.1080/10407782.2024.2323169}, pages = {1 -- 19}, abstract = {This work deals with the evaluation of a tube-in-tube reformer concept for the realization of the Micro Gas Turbine Solid Oxide Fuel Cell (MGT-SOFC) hybrid process using a semi-validated numerical model. Rigorous heat transfer analysis considering chemical reactions were performed for this concept. To validate the reforming kinetics and heat transfer mechanisms in a catalyst bed, experiments were conducted using a single reactor tube located in a temperature-controlled furnace. Different experimental conditions, such as furnace temperature and space velocity, were considered. A numerical model was replicated according to the single-tube reactor investigated and validated with the experimental results. The catalyst bed is considered as porous material with chemical reactions as internal source terms of species transport equations and energy transport equation. Since the heat transfer into the reformer tubes in the real operating environment is subject to different mechanisms (predominantly convection) than that in a furnace (predominantly thermal radiation), only the parameters on the side of the catalyst bed tuned by the single-tube experiment could be retained for the numerical model of the tube-in-tube concept, which leads to a semi-validated model. Based on this semi-validated model, the performance (such as temperature distribution, conversion rate of the products, etc.) and the applicability of a tube-in-tube reformer concept, considering the variation of boundary conditions, were investigated and evaluated.}, language = {en} } @misc{AsliMhgoubHoeschler, author = {Asli, Majid and Mhgoub, Mosaab and H{\"o}schler, Klaus}, title = {Numerical investigation of a turbine working with a highly unsteady exhaust flow of a hydrogen-driven rotating detonation combustion}, series = {International journal of thermofluids}, volume = {29}, journal = {International journal of thermofluids}, publisher = {Elsevier BV}, address = {Amsterdam}, issn = {2666-2027}, doi = {10.1016/j.ijft.2025.101356}, pages = {1 -- 9}, abstract = {Traditionally, turbomachines are designed for steady-state operations around which they achieve optimal performance and efficiency. However, in novel applications, a turbomachine may be exposed to unsteady flow forcing the machine to operate under fluctuating off design conditions. Pressure Gain Combustion (PGC) through detonation can be an extreme example of unsteady flow which affects the turbine performance adversely. The efficient way of energy extraction from PGCs is still an open question which needs extensive turbine design optimizations for such unsteady flow. Any flow field optimization problem in such applications needs a multitude of simulations, which can be too computationally expensive to be utilized as it is realized as an unsteady 3D-CFD problem. In this regard, the current study aims at proposing and evaluating an approach for optimizing a turbine working under highly unsteady exhaust flow of a Rotating Detonation Combustion (RDC). A two stage turbine is placed downstream an RDC and the turbine inlet condition is calculated by a 2D-Euler simulation tool. A turbine optimization problem is defined and three optimization processes with an objective of minimizing entropy are performed using steady-state 3D-CFD simulation as the objective function evaluator. The turbine inlet boundary conditions in the three optimization efforts include peak, mean and trough values of the RDC outlet pulsating flow condition. Finally, detailed unsteady simulations are carried out for the three new geometries and compared with the baseline turbine. The results showed that the steady-state Reynolds Averaged Navier Stocks (RANS) simulations can be utilized using either mean or trough values of the pulsating boundary condition in iterating a design optimization problem, instead of full unsteady RANS simulations applying time and circumferential location dependent boundary conditions. Given the specific RDC boundary condition and the turbine geometry in this study, the optimized turbine exhibited up to 7.71\% less entropy generation and up to 7\% higher output power compared to the baseline counterpart in unsteady operation. This approach enables a more efficient design optimization process while accounting for the complex dynamics of the RDC exhaust flow. Overall, the approach presented in this paper is practical for optimizing highly unsteady turbomachines specifically for the case of RDCs during any early design optimization procedure, addressing the computational challenges associated with simulating unsteady flows while ensuring the turbine's effectiveness under real operating conditions.}, language = {en} } @misc{SharmaRadomskyMathiazhaganetal., author = {Sharma, Dikshant and Radomsky, Lukas and Mathiazhagan, Akilan and Asli, Majid and H{\"o}schler, Klaus and Mallwitz, Regine}, title = {Thermal analysis of metal foam integrated heatsink for electrified aircraft applications}, series = {International journal of thermofluids}, volume = {30}, journal = {International journal of thermofluids}, publisher = {Elsevier BV}, address = {Amsterdam}, issn = {2666-2027}, doi = {https://doi.org/10.1016/j.ijft.2025.101465}, pages = {1 -- 21}, abstract = {Metal foams facilitate large heat dissipation in high-power dense systems such as power electronics for electrified propulsion application. This work addresses the cooling of a power semiconductor device with aluminium and copper metal foam integrated hybrid heatsink and its comparative analysis to a conventional finned heatsink using 0D and 3D modelling approach. Two equation foam model in Fluent is utilized and the numerical approach is validated against experimental dataset. Inlet air velocity is varied such that the Darcy to turbulent regimes of the open-cellular foams are covered. Foam porosities from ∼ 0.85-0.95 with 10-20 PPI are investigated and the thermal performance of the heatsink is found to be independent of the foam material. High porosity (> 0.9), 20 PPI foams are found to aid forced-convection by improving the thermal resistance by more than 10\% against the 10 PPI counterparts. The hybrid heatsink outperforms the foam-based and conventional heatsink by 40\% and 15\% respectively when considering the reduction in junction temperatures, while the hydraulic resistance increases 10 times when compared to the conventional one. The 0D thermal resistance model is robust in predicting the junction temperatures for metal foam heatsinks with only a 5\%-6\% discrepancy for both the 50 W and 100 W heat load scenarios. The key and novel contribution of this study is the integration of detailed 3D simulations of a power electronics cooling environment with the development of a corresponding 0D thermal model. This approach not only eases the physical representation of the system but also enables the model to be extended to diverse heat load conditions.}, language = {en} } @misc{SharmaRadomskyMathiazhaganetal., author = {Sharma, Dikshant and Radomsky, Lukas and Mathiazhagan, Akilan and Konda, Karunakar Reddy and Hammami, Ghaieth and Asli, Majid and H{\"o}schler, Klaus and Mallwitz, Regine}, title = {Strut-based porous media heatsinks for high-performance power electronics thermal management in electrified aircrafts}, series = {ASME Turbo Expo 2025 : Turbomachinery Technical Conference and Exposition : Volume 4: Controls, Diagnostics \& Instrumentation; Cycle Innovations; Education; Electric Power : June 16-20, 2025, Memphis, Tennessee, USA}, volume = {4}, journal = {ASME Turbo Expo 2025 : Turbomachinery Technical Conference and Exposition : Volume 4: Controls, Diagnostics \& Instrumentation; Cycle Innovations; Education; Electric Power : June 16-20, 2025, Memphis, Tennessee, USA}, number = {V004T06A011}, publisher = {The American Society of Mechanical Engineers}, address = {New York, NY}, isbn = {978-0-7918-8880-3}, doi = {10.1115/GT2025-152670}, pages = {1 -- 11}, abstract = {Multi-level inverters are one promising solution for high-power applications, enabling higher efficiency and improved power quality over conventional inverters. The emergence of these converter topologies with a larger number of topological switches makes reliable, forced and even natural convection air cooling a feasible option for aircraft power electronics. The need for high heat dissipation rate, robust design and lightweight heatsinks has led to the development of strut-based porous media structures for forced air cooling. The current work focuses on investigating Kelvin, Body-Centered Cubic (BCC) and Simple Cubic (SC) periodic open cellular structured (POCS) lattice heatsink with a fixed porosity and a fixed unit cell size. 3D printed Kelvin and SC heatsinks using AlSi10Mg material are tested in an air duct experimental setup along with a conventional LAM aluminium heatsink. The Computational Fluid Dynamics (CFD) simulation model is validated with the experimental results and a 0D thermal model is developed using the CFD results. The CFD thermal results are in close accordance with the experimental results for the POCS heatsink within an error band of ±2\%. The 0D results using the thermal data from CFD simulations also show a close comparison for the calculated semiconductor junction temperatures. The Kelvin heatsink performs the best thermally from the CFD analysis and has the least error when comparing the 0D and 3D-CFD results.}, language = {en} } @misc{KimGerstbergerAslietal., author = {Kim, Dongsuk and Gerstberger, Ulf and Asli, Majid and H{\"o}schler, Klaus}, title = {U-Net driven semantic segmentation for detection and quantification of cracks on gas turbine blade tips}, series = {Results in engineering}, volume = {29}, journal = {Results in engineering}, publisher = {Elsevier BV}, address = {Amsterdam}, issn = {2590-1230}, doi = {10.1016/j.rineng.2025.108864}, pages = {1 -- 9}, abstract = {Crack detection and quantification on gas turbine blades is crucial for component validation during the development phase and for operational efficiency in service, as unexpected cracks can compromise blade integrity and lead to early engine removals. Gas turbine blades operate under extreme thermal and mechanical stresses, making them particularly susceptible to crack formation. At the same time deterministic predictions of crack formation are subject to high uncertainty in material data and actual loading conditions. Accurate detection and quantification of cracks, therefore, is essential for the validation and calibration of life predictions in order to prevent in-service failures, to extend component lifespan, and to reduce maintenance costs. This study introduces a U-Net based semantic segmentation model designed to automate crack detection on turbine blade tips. The model was trained on a dataset of 210 surface images with and without evidence of cracks, each divided into 128  ×  128 pixel patches. Data augmentation techniques were applied to address the class imbalance between cracked and non-cracked pixels. The U-Net architecture, optimized with a Dice loss function, achieved a validation IoU of 0.7557, along with approximately 85\% recall and precision in identifying cracked pixels. The pixel-based accuracy of the model primarily affects the quantification of cracks rather than their identification. A sliding window pipeline was implemented to extend the model's applicability, enabling segmentation of entire blade tip images for comprehensive crack localization. While the model may occasionally miss low-contrast cracks, it holds potential as a supplementary tool for manual inspection as part of the life prediction validation. By providing automated crack localization and quantification, the model can assist in analyzing crack characteristics relative to engine operating conditions.}, language = {en} }