TY - CHAP A1 - Funke, Harald A1 - Beckmann, Nils A1 - Stefan, Lukas A1 - Keinz, Jan T1 - Hydrogen combustor integration study for a medium range aircraft engine using the dry-low NOx “Micromix” combustion principle T2 - Proceedings of the ASME Turbo Expo 2023: Turbomachinery Technical Conference and Exposition. Volume 1: Aircraft Engine. N2 - The feasibility study presents results of a hydrogen combustor integration for a Medium-Range aircraft engine using the Dry-Low-NOₓ Micromix combustion principle. Based on a simplified Airbus A320-type flight mission, a thermodynamic performance model of a kerosene and a hydrogen-powered V2530-A5 engine is used to derive the thermodynamic combustor boundary conditions. A new combustor design using the Dry-Low NOx Micromix principle is investigated by slice model CFD simulations of a single Micromix injector for design and off-design operation of the engine. Combustion characteristics show typical Micromix flame shapes and good combustion efficiencies for all flight mission operating points. Nitric oxide emissions are significant below ICAO CAEP/8 limits. For comparison of the Emission Index (EI) for NOₓ emissions between kerosene and hydrogen operation, an energy (kerosene) equivalent Emission Index is used. A full 15° sector model CFD simulation of the combustion chamber with multiple Micromix injectors including inflow homogenization and dilution and cooling air flows investigates the combustor integration effects, resulting NOₓ emission and radial temperature distributions at the combustor outlet. The results show that the integration of a Micromix hydrogen combustor in actual aircraft engines is feasible and offers, besides CO₂ free combustion, a significant reduction of NOₓ emissions compared to kerosene operation. KW - emission index KW - nitric oxides KW - aircraft engine KW - Micromix KW - combustion KW - hydrogen Y1 - 2023 SN - 978-0-7918-8693-9 U6 - https://doi.org/10.1115/GT2023-102370 N1 - Paper No. GT2023-102370, V001T01A022 N1 - ASME Turbo Expo 2023: Turbomachinery Technical Conference and Exposition June 26–30, 2023, Boston, Massachusetts, USA PB - ASME CY - New York ER - TY - JOUR A1 - Baader, Fabian A1 - Boxberg, Marc S. A1 - Chen, Qian A1 - Förstner, Roger A1 - Kowalski, Julia A1 - Dachwald, Bernd T1 - Field-test performance of an ice-melting probe in a terrestrial analogue environment JF - Icarus N2 - Melting probes are a proven tool for the exploration of thick ice layers and clean sampling of subglacial water on Earth. Their compact size and ease of operation also make them a key technology for the future exploration of icy moons in our Solar System, most prominently Europa and Enceladus. For both mission planning and hardware engineering, metrics such as efficiency and expected performance in terms of achievable speed, power requirements, and necessary heating power have to be known. Theoretical studies aim at describing thermal losses on the one hand, while laboratory experiments and field tests allow an empirical investigation of the true performance on the other hand. To investigate the practical value of a performance model for the operational performance in extraterrestrial environments, we first contrast measured data from terrestrial field tests on temperate and polythermal glaciers with results from basic heat loss models and a melt trajectory model. For this purpose, we propose conventions for the determination of two different efficiencies that can be applied to both measured data and models. One definition of efficiency is related to the melting head only, while the other definition considers the melting probe as a whole. We also present methods to combine several sources of heat loss for probes with a circular cross-section, and to translate the geometry of probes with a non-circular cross-section to analyse them in the same way. The models were selected in a way that minimizes the need to make assumptions about unknown parameters of the probe or the ice environment. The results indicate that currently used models do not yet reliably reproduce the performance of a probe under realistic conditions. Melting velocities and efficiencies are constantly overestimated by 15 to 50 % in the models, but qualitatively agree with the field test data. Hence, losses are observed, that are not yet covered and quantified by the available loss models. We find that the deviation increases with decreasing ice temperature. We suspect that this mismatch is mainly due to the too restrictive idealization of the probe model and the fact that the probe was not operated in an efficiency-optimized manner during the field tests. With respect to space mission engineering, we find that performance and efficiency models must be used with caution in unknown ice environments, as various ice parameters have a significant effect on the melting process. Some of these are difficult to estimate from afar. Y1 - 2023 U6 - https://doi.org/10.1016/j.icarus.2023.115852 N1 - Forschungsdaten hierzu: "Performance data of an ice-melting probe from field tests in two different ice environments" (https://opus.bibliothek.fh-aachen.de/opus4/frontdoor/index/index/docId/10890) IS - 409 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Mikucki, Jill Ann A1 - Schuler, C. G. A1 - Digel, Ilya A1 - Kowalski, Julia A1 - Tuttle, M. J. A1 - Chua, Michelle A1 - Davis, R. A1 - Purcell, Alicia A1 - Ghosh, D. A1 - Francke, G. A1 - Feldmann, M. A1 - Espe, C. A1 - Heinen, Dirk A1 - Dachwald, Bernd A1 - Clemens, Joachim A1 - Lyons, W. B. A1 - Tulaczyk, S. T1 - Field-Based planetary protection operations for melt probes: validation of clean access into the blood falls, antarctica, englacial ecosystem JF - Astrobiology N2 - Subglacial environments on Earth offer important analogs to Ocean World targets in our solar system. These unique microbial ecosystems remain understudied due to the challenges of access through thick glacial ice (tens to hundreds of meters). Additionally, sub-ice collections must be conducted in a clean manner to ensure sample integrity for downstream microbiological and geochemical analyses. We describe the field-based cleaning of a melt probe that was used to collect brine samples from within a glacier conduit at Blood Falls, Antarctica, for geomicrobiological studies. We used a thermoelectric melting probe called the IceMole that was designed to be minimally invasive in that the logistical requirements in support of drilling operations were small and the probe could be cleaned, even in a remote field setting, so as to minimize potential contamination. In our study, the exterior bioburden on the IceMole was reduced to levels measured in most clean rooms, and below that of the ice surrounding our sampling target. Potential microbial contaminants were identified during the cleaning process; however, very few were detected in the final englacial sample collected with the IceMole and were present in extremely low abundances (∼0.063% of 16S rRNA gene amplicon sequences). This cleaning protocol can help minimize contamination when working in remote field locations, support microbiological sampling of terrestrial subglacial environments using melting probes, and help inform planetary protection challenges for Ocean World analog mission concepts. Y1 - 2023 U6 - https://doi.org/10.1089/ast.2021.0102 SN - 1557-8070 (online) SN - 153-1074 (print) VL - 23 IS - 11 SP - 1165 EP - 1178 PB - Liebert CY - New York, NY ER - TY - JOUR A1 - Koch, Christopher A1 - Böhnisch, Nils A1 - Verdonck, Hendrik A1 - Hach, Oliver A1 - Braun, Carsten T1 - Comparison of unsteady low- and mid-fidelity propeller aerodynamic methods for whirl flutter applications JF - Applied Sciences N2 - Aircraft configurations with propellers have been drawing more attention in recent times, partly due to new propulsion concepts based on hydrogen fuel cells and electric motors. These configurations are prone to whirl flutter, which is an aeroelastic instability affecting airframes with elastically supported propellers. It commonly needs to be mitigated already during the design phase of such configurations, requiring, among other things, unsteady aerodynamic transfer functions for the propeller. However, no comprehensive assessment of unsteady propeller aerodynamics for aeroelastic analysis is available in the literature. This paper provides a detailed comparison of nine different low- to mid-fidelity aerodynamic methods, demonstrating their impact on linear, unsteady aerodynamics, as well as whirl flutter stability prediction. Quasi-steady and unsteady methods for blade lift with or without coupling to blade element momentum theory are evaluated and compared to mid-fidelity potential flow solvers (UPM and DUST) and classical, derivative-based methods. Time-domain identification of frequency-domain transfer functions for the unsteady propeller hub loads is used to compare the different methods. Predictions of the minimum required pylon stiffness for stability show good agreement among the mid-fidelity methods. The differences in the stability predictions for the low-fidelity methods are higher. Most methods studied yield a more unstable system than classical, derivative-based whirl flutter analysis, indicating that the use of more sophisticated aerodynamic modeling techniques might be required for accurate whirl flutter prediction. KW - Aeroelasticity KW - Flutter KW - Propeller whirl flutter KW - Unsteady aerodynamics KW - 1P hub loads Y1 - 2024 U6 - https://doi.org/10.3390/app14020850 SN - 2076-3417 VL - 14 IS - 2 SP - 1 EP - 28 PB - MDPI CY - Basel ER - TY - JOUR A1 - Böhnisch, Nils A1 - Braun, Carsten A1 - Muscarello, Vincenzo A1 - Marzocca, Pier T1 - About the wing and whirl flutter of a slender wing–propeller system JF - Journal of Aircraft N2 - Next-generation aircraft designs often incorporate multiple large propellers attached along the wingspan (distributed electric propulsion), leading to highly flexible dynamic systems that can exhibit aeroelastic instabilities. This paper introduces a validated methodology to investigate the aeroelastic instabilities of wing–propeller systems and to understand the dynamic mechanism leading to wing and whirl flutter and transition from one to the other. Factors such as nacelle positions along the wing span and chord and its propulsion system mounting stiffness are considered. Additionally, preliminary design guidelines are proposed for flutter-free wing–propeller systems applicable to novel aircraft designs. The study demonstrates how the critical speed of the wing–propeller systems is influenced by the mounting stiffness and propeller position. Weak mounting stiffnesses result in whirl flutter, while hard mounting stiffnesses lead to wing flutter. For the latter, the position of the propeller along the wing span may change the wing mode shapes and thus the flutter mechanism. Propeller positions closer to the wing tip enhance stability, but pusher configurations are more critical due to the mass distribution behind the elastic axis. Y1 - 2024 U6 - https://doi.org/10.2514/1.C037542 SN - 1533-3868 SP - 1 EP - 14 PB - AIAA CY - Reston, Va. ER - TY - JOUR A1 - Schopen, Oliver A1 - Narayan, Sriram A1 - Beckmann, Marvin A1 - Najmi, Aezid-Ul-Hassan A1 - Esch, Thomas A1 - Shabani, Bahman T1 - An EIS approach to quantify the effects of inlet air relative humidity on the performance of proton exchange membrane fuel cells: a pathway to developing a novel fault diagnostic method JF - International Journal of Hydrogen Energy N2 - In this work, the effect of low air relative humidity on the operation of a polymer electrolyte membrane fuel cell is investigated. An innovative method through performing in situ electrochemical impedance spectroscopy is utilised to quantify the effect of inlet air relative humidity at the cathode side on internal ionic resistances and output voltage of the fuel cell. In addition, algorithms are developed to analyse the electrochemical characteristics of the fuel cell. For the specific fuel cell stack used in this study, the membrane resistance drops by over 39 % and the cathode side charge transfer resistance decreases by 23 % after increasing the humidity from 30 % to 85 %, while the results of static operation also show an increase of ∼2.2 % in the voltage output after increasing the relative humidity from 30 % to 85 %. In dynamic operation, visible drying effects occur at < 50 % relative humidity, whereby the increase of the air side stoichiometry increases the drying effects. Furthermore, other parameters, such as hydrogen humidification, internal stack structure, and operating parameters like stoichiometry, pressure, and temperature affect the overall water balance. Therefore, the optimal humidification range must be determined by considering all these parameters to maximise the fuel cell performance and durability. The results of this study are used to develop a health management system to ensure sufficient humidification by continuously monitoring the fuel cell polarisation data and electrochemical impedance spectroscopy indicators. KW - PEM fuel cell KW - Electrochemical impedance spectroscopy KW - Relative air humidity KW - Active humidity control KW - Impedance analysis Y1 - 2024 SN - 0360-3199 (print) U6 - https://doi.org/10.1016/j.ijhydene.2024.01.218 SN - 1879-3487 (online) VL - 58 IS - 8 SP - 1302 EP - 1315 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Schopen, Oliver A1 - Shah, Neel A1 - Esch, Thomas A1 - Shabani, Bahman T1 - Critical quantitative evaluation of integrated health management methods for fuel cell applications JF - International Journal of Hydrogen Energy N2 - Online fault diagnostics is a crucial consideration for fuel cell systems, particularly in mobile applications, to limit downtime and degradation, and to increase lifetime. Guided by a critical literature review, in this paper an overview of Health management systems classified in a scheme is presented, introducing commonly utilised methods to diagnose FCs in various applications. In this novel scheme, various Health management system methods are summarised and structured to provide an overview of existing systems including their associated tools. These systems are classified into four categories mainly focused on model-based and non-model-based systems. The individual methods are critically discussed when used individually or combined aimed at further understanding their functionality and suitability in different applications. Additionally, a tool is introduced to evaluate methods from each category based on the scheme presented. This tool applies the technique of matrix evaluation utilising several key parameters to identify the most appropriate methods for a given application. Based on this evaluation, the most suitable methods for each specific application are combined to build an integrated Health management system. KW - Fuel cell KW - Health management system KW - Online diagnostic KW - Fault detection KW - Non-model-based Evaluation Y1 - 2024 U6 - https://doi.org/10.1016/j.ijhydene.2024.05.156 SN - 0360-3199 VL - 70 SP - 370 EP - 388 PB - Elsevier CY - Amsterdam ER - TY - INPR A1 - Schmülling, Max A1 - Gützlaff, Joel A1 - Czupalla, Markus T1 - A thermal simulation environment for moving objects on the lunar surface N2 - This paper presents a thermal simulation environment for moving objects on the lunar surface. The goal of the thermal simulation environment is to enable the reliable prediction of the temperature development of a given object on the lunar surface by providing the respective heat fluxes for a mission on a given travel path. The user can import any object geometry and freely define the path that the object should travel. Using the path of the object, the relevant lunar surface geometry is imported from a digital elevation model. The relevant parts of the lunar surface are determined based on distance to the defined path. A thermal model of these surface sections is generated, consisting of a porous layer on top and a denser layer below. The object is moved across the lunar surface, and its inclination is adapted depending on the slope of the terrain below it. Finally, a transient thermal analysis of the object and its environment is performed at several positions on its path and the results are visualized. The paper introduces details on the thermal modeling of the lunar surface, as well as its verification. Furthermore, the structure of the created software is presented. The robustness of the environment is verified with the help of sensitivity studies and possible improvements are presented. KW - Dynamic modeling KW - Thermal analysis KW - ESATAN-TMS KW - Lunar Surface KW - Thermal Model Y1 - 2024 U6 - https://doi.org/10.21203/rs.3.rs-3902363/v1 ER - TY - RPRT A1 - Barnat, Miriam A1 - Arntz, Kristian A1 - Bernecker, Andreas A1 - Fissabre, Anke A1 - Franken, Norbert A1 - Goldbach, Daniel A1 - Hüning, Felix A1 - Jörissen, Jörg A1 - Kirsch, Ansgar A1 - Pettrak, Jürgen A1 - Rexforth, Matthias A1 - Josef, Rosenkranz A1 - Terstegge, Andreas T1 - Strategische Gestaltung von Studiengängen für die Zukunft: Ein kollaborativ entwickeltes Self-Assessment BT - Diskussionspapier Nr. 33 T2 - Hochschulforum Digitalisierung - Diskussionspapier N2 - Das Diskussionspapier beschreibt einen Prozess an der FH Aachen zur Entwicklung und Implementierung eines Self-Assessment-Tools für Studiengänge. Dieser Prozess zielte darauf ab, die Relevanz der Themen Digitalisierung, Internationalisierung und Nachhaltigkeit in Studiengängen zu stärken. Durch Workshops und kollaborative Entwicklung mit Studiendekan:innen entstand ein Fragebogen, der zur Reflexion und strategischen Weiterentwicklung der Studiengänge dient. Y1 - 2024 SN - 2365-7081 PB - Stifterverband für die Deutsche Wissenschaft CY - Berlin ER -