TY - JOUR A1 - Asli, Majid A1 - Mhgoub, Mosaab A1 - Klaus, Höschler T1 - Numerical investigation of a turbine working with a highly unsteady exhaust flow of a hydrogen-driven rotating detonation combustion JF - International Journal of Thermofluids N2 - 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. KW - Unsteady turbine KW - Entropy generation KW - Rotating detonation KW - Optimization KW - Computational fluid dynamic Y1 - 2025 U6 - https://doi.org/10.1016/j.ijft.2025.101356 SN - 2666-2027 VL - 29 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Konda, Karunakar Reddy A1 - Franzki, Jonas A1 - Sharma, Dikshant A1 - König, Paul A1 - Mathiazhagan, Akilan A1 - Henke, Markus A1 - Höschler, Klaus T1 - Quantitative assessment of cooling methods for electrical machines in aircraft drives JF - IEEE Access N2 - 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. KW - Cooling systems KW - Electric aircrafts KW - Motor drives KW - Sizing KW - Thermal management Y1 - 2024 U6 - https://doi.org/10.1109/ACCESS.2024.3517319 SN - 2169-3536 VL - 12 SP - 192768 EP - 192785 PB - IEEE CY - New York ER - TY - JOUR A1 - König, Paul A1 - Sharma, Dikshant A1 - Konda, Karunakar Reddy A1 - Xie, Tianxiao A1 - Höschler, Klaus T1 - Comprehensive review on cooling of permanent magnet synchronous motors and their qualitative assessment for aerospace applications T1 - Umfassender Überblick über die Kühlung von Permanentmagnet-Synchronmotoren und ihre qualitative Bewertung für Luft- und Raumfahrtanwendungen N2 - 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. N2 - Der Permanentmagnet-Synchronmotor (PMSM) ist ein geeigneter Kandidat für elektrifizierte Antriebe in der Luftfahrt. Trotz des sehr hohen Wirkungsgrades führt die Abwärme während des Betriebs zu Leistungseinschränkungen. Erhöhte Temperaturen in den elektrischen Isolierungen und den Permanentmagneten stellen ein potenzielles Sicherheitsrisiko dar, das durch gezielte Kühlung reduziert werden muss. Ein umfassender Überblick über die aktuellen Forschungsaktivitäten im Bereich der Kühlungsmethoden für PMSM wird vorgestellt. Die Kühlungsmethoden werden nach ihrem Wärmeübertragungsmechanismus beschrieben, gruppiert und den Komponenten innerhalb des Motors zugeordnet. Die wichtigsten Ergebnisse der gesichteten Literatur werden im Zusammenhang mit der PMSM-Kühlung beschrieben. Es werden Informationen über Kühlmedien und mögliche Kombinationen von Kühlmethoden in Komponenten gesammelt. Bewertungsparameter wie Sicherheit, Gewicht, Effektivität, Integrierbarkeit, Komplexität und Kosten werden definiert, um anschließend eine qualitative Analyse für sechs ausgewählte Kühlmethoden zu ermöglichen. Ein punktgewichteter Bewertungsansatz nach VDI 2225 wurde verwendet, um den vielversprechendsten Kühlungsansatz für eine erfolgreiche Umsetzung in der Luftfahrt zu identifizieren. KW - Electrical machines KW - Electric aviation KW - Motor cooling KW - PMSM KW - Thermal management KW - Elektrische Luftfahrt KW - Elektrische Maschinen KW - Motorkühlung KW - Wärmemanagement KW - Luftfahrt KW - Raumfahrt KW - Elektroantrieb KW - Dauermagneterregter Synchronmotor KW - Kühlung Y1 - 2023 U6 - https://doi.org/10.3390/en16227524 ER - TY - JOUR A1 - Mathiazhagan, Akilan A1 - Kim, Dongsuk A1 - Vegini, George A1 - Montemurro, Marco A1 - Baltag, Serghei A1 - Asli, Majid A1 - Höschler, Klaus T1 - Design strategies for enhancement of mechanical behaviour of hybrid cellular structures based on schwarz primitive geometry JF - Materials & Design N2 - Hybrid cellular structures are gaining attention for their multi-functionality in load-bearing, heat-transfer, and energy-absorption applications. Schwarz Primitive (SCP)-based geometries, a subclass of Triply Periodic Minimal Surfaces (TPMS), with their high surface area, tunable properties, and continuous topology, provide strong potential for such applications. To further enhance mechanical performance and stability, this work conducts a thorough investigation of hybrid designs that integrate SCP TPMS with Kelvin truss-based geometries, combining the high connectivity of TPMS with the reinforcement and directional stiffness benefits of struts. A theoretical strain-based homogenization framework was implemented over a design matrix that independently varies the relative densities of the SCP and the truss geometries, quantifying how each constituent proportion influences the overall mechanical response of the hybrid. These predictions were corroborated by finite element analyses in ANSYS 2023 and by mechanical testing of 3D-printed polylactic acid samples, providing independent validation of homogenization trends across orientations. The resulting formulation enables rapid property mapping, sensitivity analysis, and optimization of SCP-Kelvin hybrids, thereby reducing the prototyping effort while guiding application-based design selection and customization. KW - Lightweight design KW - Anisotropy control KW - Homogenization KW - Triply periodic minimal surfaces KW - Periodic open cellular structures Y1 - 2025 U6 - https://doi.org/10.1016/j.matdes.2025.115161 SN - 0264-1275 VL - 240 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Asli, Majid A1 - Kim, Dongsuk A1 - Höschler, Klaus T1 - On the potentials of the integration of pressure gain combustion with a hybrid electric propulsion system T1 - Über die Möglichkeiten der Integration der Druckverstärkungsverbrennung in ein hybrides elektrisches Antriebssystem N2 - 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. N2 - Da das Problem der Schadstoffemissionen von Flugantrieben eskaliert, gewinnt die Forschung an alternativen Antriebssträngen zunehmend an Dynamik. Zwei vielversprechende Technologien sind das Hybrid Electric Propulsion System (HEPS) und die Pressure Gain Combustion (PGC). Es wird erwartet, dass HEPS die Schadstoffemissionen durch einen geringeren Kraftstoffverbrauch reduziert, während PGC die Detonation in der Brennkammer nutzt, um den thermischen Wirkungsgrad von Motoren durch Erhöhung des Gesamtdrucks während der Verbrennung zu erhöhen. Diese Studie untersucht ausführlich die Integration dieser beiden neuen Technologien und bewertet gründlich die Vorteile, die sich aus ihrer Kombination ergeben. Zunächst wird das renommierte Turboprop-Triebwerk PW127 mithilfe der Gasturb-Software einem Benchmarking unterzogen und modelliert. Das Modell wird mit dem T-MATS-Tool in Simulink integriert, wobei HEPS- und Druckverstärkungskomponenten hinzugefügt werden, um die Thermodynamik verschiedener Konfigurationen unter verschiedenen Druckverstärkungswerten und HEPS-Parametern zu analysieren. Die Analyse, die bis zur Reiseflugphase des Basisflugzeugs durchgeführt wurde, zeigt, dass die Anwendung der Druckverstärkungsverbrennung durch Rotating Detonation Combustion (RDC) im Vergleich zu HEPS mit herkömmlichen Gasturbinen zu einer deutlicheren Effizienzsteigerung und Reduzierung des Treibstoffverbrauchs führt. HEPS trägt jedoch dazu bei, einen gleichmäßigeren Brennkammereinlasszustand aufrechtzuerhalten und reduziert die Turbineneinlasstemperatur (TIT) in der Startphase, wo sonst die höchste TIT auftritt. Die Ergebnisse legen nahe, dass die Integration von HEPS mit PGC dazu beitragen kann, optimale Brennkammerbedingungen aufrechtzuerhalten und die Verschlechterung der Turbineneffizienz abzumildern. KW - Pressure gain combustion KW - Hybrid electric propulsion KW - Rotating detonation combustion KW - Druckverstärkungsverbrennung KW - Rotierende Detonationsverbrennung KW - Hybrid-Elektroantrieb KW - Propeller-Turbinen-Luftstrahltriebwerk KW - Hybridantrieb KW - Verbrennung KW - Schadstoffemission KW - Emissionsverringerung Y1 - 2023 U6 - https://doi.org/10.3390/aerospace10080710 ER - TY - JOUR A1 - Kim, Dongsuk A1 - Gerstberger, Ulf A1 - Asli, Majid A1 - Höschler, Klaus T1 - U-Net Driven Semantic Segmentation for Detection and Quantification of Cracks on Gas Turbine Blade Tips JF - Results in Engineering N2 - 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. KW - Crack detection KW - Semantic segmentation KW - Gas turbine blade KW - U-Net KW - Deep learning KW - Convolutional neural network Y1 - 2025 U6 - https://doi.org/10.1016/j.rineng.2025.108864 SN - 2590-1230 VL - 29 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Sharma, Dikshant A1 - Radomsky, Lukas A1 - Mathiazhagan, Akilan A1 - Asli, Majid A1 - Höschler, Klaus A1 - Mallwitz, Regine T1 - Thermal analysis of metal foam integrated heatsink for electrified aircraft applications JF - International Journal of Thermofluids N2 - 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. KW - Electric propulsion KW - Electronics thermal management KW - Metal foam heatsink KW - Porous media KW - Forced convection Y1 - 2025 U6 - https://doi.org/10.1016/j.ijft.2025.101465 SN - 2666-2027 VL - 30 PB - Elsevier CY - Amsterdam ER -