TY - GEN A1 - Varatharajulu Purgunan, Gokkul Raj A1 - Asli, Majid A1 - Nacci, Teodosio A1 - Misul, Daniela Anna A1 - Salvadori, Simone A1 - Stathopoulos, Panagiotis T1 - Film Cooling Modeling in a Turbine Working under the Unsteady Exhaust Flow of Pulsed Detonation Combustion T2 - Energies N2 - 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. KW - Pressure gain combustion KW - Turbomachinery KW - Cooling Y1 - 2024 UR - https://www.mdpi.com/1996-1073/17/6/1312 U6 - https://doi.org/10.3390/en17061312 SN - 1996-1073 VL - 17 IS - 6 SP - 1 EP - 20 ER - TY - GEN A1 - Kim, Dogsuk A1 - Asli, Majid A1 - Höschler, Klaus T1 - On the Potentials of the Integration of Pressure Gain Combustion with a Hybrid Electric Propulsion System T2 - Aerospace 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. KW - Pressure gain combustion KW - Hybrid Electric Propulsion KW - Rotating detonation combustion Y1 - 2023 UR - https://www.mdpi.com/2226-4310/10/8/710 U6 - https://doi.org/10.3390/aerospace10080710 SN - 2226-4310 VL - 10 IS - 8 SP - 1 EP - 17 ER - TY - GEN A1 - Asli, Majid A1 - König, Paul A1 - Sharma, Dikshant A1 - Pontika, Evangelia A1 - Huete, Jon A1 - Konda, Karunakar Reddy A1 - Mathiazhagan, Akilan A1 - Xie, Tianxiao A1 - Höschler, Klaus A1 - Laskaridis, Panagiotis T1 - Thermal management challenges in hybrid-electric propulsion aircraft T2 - Progress in Aerospace Sciences N2 - 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. KW - thermal management KW - Hybrid electric propulsion Y1 - 2024 UR - https://www.sciencedirect.com/science/article/pii/S0376042123000830 U6 - https://doi.org/10.1016/j.paerosci.2023.100967 SN - 1873-1724 VL - 144 SP - 1 EP - 29 ER - TY - GEN A1 - Asli, Majid A1 - Mhgoub, Mosaab A1 - Höschler, Klaus T1 - Numerical investigation of a turbine working with a highly unsteady exhaust flow of a hydrogen-driven rotating detonation combustion T2 - 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 - Turbine KW - Unsteady KW - Numerical simulation Y1 - 2025 UR - https://www.sciencedirect.com/science/article/pii/S2666202725003027 U6 - https://doi.org/10.1016/j.ijft.2025.101356 SN - 2666-2027 VL - 29 SP - 1 EP - 9 PB - Elsevier BV CY - Amsterdam ER - TY - GEN 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 T2 - 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 KW - Conjugate heat transfer Y1 - 2025 U6 - https://doi.org/https://doi.org/10.1016/j.ijft.2025.101465 SN - 2666-2027 VL - 30 SP - 1 EP - 21 PB - Elsevier BV CY - Amsterdam ER - TY - GEN 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 T2 - 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 - 2026 U6 - https://doi.org/10.1016/j.rineng.2025.108864 SN - 2590-1230 VL - 29 SP - 1 EP - 9 PB - Elsevier BV CY - Amsterdam ER -