bluuebunny/crossref_metadata_2025_split huggingface dataset:
Applying Rapid Qualification to Fatigue Assessment of a Binder Jet Superalloy
Authors: Scott-Emuakpor Onome , Johnson Philip , Forgiarini Mattia , Noronha Tim 
Published: August 2024

Abstract
A rapid fatigue testing capability is demonstrated as a viable qualification approach to expedite the development of materials and Additive Manufacturing (AM) processes. Specifically, this work explores accelerated vibration fatigue testing results of Binder Jet Mar M 247 specimens for short lead time decision-making associated with changes to a postprocessing step. Using a vibration bending fatigue test method, this study reached a conclusion on the effects of Tantalum getter contamination on fatigue performance in 34% of the time while covering a 5X greater cycles to failure range than standard axial test methods. Furthermore, comparisons show that the differences in the fatigue performances of the accelerated test method and standard tests can be quantified with a scalar factor. The results in this work and future development of low-cost accelerated testing products are promising for achieving rapid qualification of AM processes that benefits the advancement of gas turbine engine systems.
The Effect of Heterogeneous Natural Gas-Hydrogen Input Into F-Class Gas Turbine Combustor As a Combustion Optimization Method
Authors: Park Jungkeuk , Shin Jugon , Park Seik , Lee Sanghyup , Choi Nakjeong 
Published: August 2024

Abstract
The global push to combat climate change by transitioning to clean power generation is accelerating. One promising avenue involves utilizing low-carbon fuels like hydrogen and ammonia in place of conventional fossil fuels such as coal and natural gas, particularly in gas turbine-based combined cycle power plants. While hydrogen co-firing technology shows potential, its widespread adoption faces challenges like infrastructure readiness and cost. To address this, optimizing existing gas turbine engines for hydrogen compatibility becomes crucial. In our study, we propose a novel approach: varying hydrogen content between different nozzle groups in gas turbine combustors. Through experiments using the full-scale combustor of a commercialized F-class gas turbine model, we investigated the impact of heterogeneity or variations in hydrogen concentrations at the center and outer nozzles on combustion dynamics and emissions, comparing with the cases of the homogeneous natural gas only fuel and natural gas-hydrogen mixtures. Hydrogen co-firing increased NOx emission while decreasing CO2 emissions. The peak amplitudes of combustion dynamic pressure, especially in the frequency domain of 125∼245Hz, were linearly proportional to the co-firing ratio, with 41.2% increase observed for 30% co-firing ratio. To ensure stable gas turbine operation, the co-firing ratio should be limited. Our findings revealed a significant correlation between NOx emissions and combustion stability, and varying levels of heterogeneity. Moreover, under higher heterogeneity conditions with intensive hydrogen input into the center nozzle, improved hydrogen co-firing performance was observed, reducing the peak amplitude of the frequency domain limiting co-firing by 22% for 25% co-firing ratio. This potentially extended the critical hydrogen co-firing ratio. Thus, implementing heterogeneous natural gas-hydrogen inputs emerges as a promising method to enhance combustion stability and enable effective hydrogen co-firing, offering a pathway towards cleaner energy generation.
Potential of Pressure Slip Casted All-Oxide CMC Elements for Use in Gas Turbine Systems
Authors: Jung Fabian , Götte Johannes , Liu Yiou , Markus Timo , Gries Thomas 
Published: August 2024

Abstract
The progression of high-temperature materials for turbines is crucial for the more efficient combustion of conventional and synthetic fuels in modern gas turbines, which is key to enhancing plant efficiency and reducing exhaust gas emissions. In this context, all-oxide ceramic matrix composites stand out due to their superior oxidation stability and temperature resistance, essential for withstanding the demanding conditions in the hot gas sections of modern turbine systems. These materials offer advantages over their metallic counterparts, including reduced cooling requirements and extended operational lifetimes. However, adapting these ceramic composites for turbine applications requires the incorporation of complex continuous fiber reinforcements, significantly increasing the ceramic’s damage tolerance. The reinforcement architecture employed presents substantial manufacturing challenges, particularly in colloidal production processes. To address this, a novel 3D-braided reinforcement architecture has been developed, enabling a near-net-shape production of continuous fiber reinforced ceramics (CFCC) through pressure slip casting technology. This approach represents a diversion from conventional CFCC manufacturing, which typically involves single-piece productions, by integrating pressure slip casting with 3D braiding for improved scalability and flexibility.
To evaluate the potential influence of pressure slip casted ceramic composites, comprised by an Al2O3-YSZ-RBAO matrix system and reinforcement by 3M Nextel 610 alumina fibers, on gas turbine systems, a thermomechanical model has been developed. This model is instrumental in calculating the material’s performance when applied to vital components of the gas turbine’s hot gas section. Therefore, it enables the prediction of the composite structure’s equivalent properties.
Reduced Order Model for Cavity-Based Combustors Describing Various Bifurcations As Cavity Size Is Varied
Authors: Singh Ashutosh , Nair Vineeth 
Published: August 2024

Abstract
In trapped vortex combustor (TVCs), where a cavity is used for flame stabilisation, large-amplitude periodic pressure fluctuations can occur at certain operating conditions due to flow-acoustics lock-in. In the present study, experiments were carried out in a laboratory-scale trapped vortex combustor by varying cavity sizes (L/D = 0.75–2.65). Unsteady pressure measurements reveal a bifurcation route of limit cycle → steeper limit cycle (with higher harmonics) → quasi-periodic → strange non-chaotic attractors (SNAs) → chaos as cavity size is increased (L/D). This overall transition leads to a 70% reduction in pressure amplitude and as such can be treated as a passive control strategy to mitigate unwanted oscillations. We employ a reduced-order model that incorporates this flow-acoustic lock-in. This model includes a feedback mechanism that accounts for the influence of acoustic modes on the vortex-shedding event. This feedback mechanism induces changes in the timescale of vortex impingement as cavity size varies, leading the system through the experimentally observed non-linear regimes. We validate our model by comparing its predictions with experimental results, highlighting its ability to capture the intricate dynamics observed in cavity-based combustors.
Experimental Investigation of Discharge Coefficients of Double Wall Cooling Systems
Authors: Xu Guangyao , Du Qiang , Xu Qingzong , Wang Pengfei , Li Hongye , Liu Haoyang 
Published: August 2024

Abstract
Double wall cooling technology is considered to be the most promising solution for next-generation gas turbine blade cooling, featuring enhanced cooling performance, reduced coolant air consumption, and a more uniform distribution of thermal stress. However, interactions in a double wall cooling system exist among the flow disturbance elements such as impinging jet, film cooling, and pin fins. Meanwhile, the arrangement and geometric parameters of the impingement/film in the double wall are different from those of traditional cooling. As a result, the flow resistance characteristics of each component are not independent of each other. Therefore, to accurately predict coolant air consumption within a double wall cooling system, this study focuses on the influence of geometric and flow parameters on the flow resistance of double wall effusion cooling system through experimental methods. The findings showed that the hole spacing, film hole inclination angle, and the number of pin fins have a significant impact on the discharge coefficient in double wall cooling. Furthermore, the internal crossflow severely affects the flow through the film cooling holes, resulting in a noticeable decrease in the overall discharge coefficient of the double wall system.
Thermodynamic Analysis and Optimization of an Innovative Closed Loop Brayton Cycle Fueled With Hydrogen
Authors: Ancona Maria Alessandra , Bianchi Michele , Cavuoti Bruno , De Pascale Andrea , Melino Francesco , Peretto Antonio 
Published: August 2024

Abstract
The growing attention to the reduction of fossil fuels dependency in the energy sector has led to an increase in the efforts to improve the renewable energy sources exploitation. Wind and solar generation is constantly growing worldwide but their fully exploitation is strictly dependent on the availability of efficient electrical storage systems.
In this context, hydrogen production, by the means of electrolysis processes powered by renewable generators, is an important option which is gaining increasing attention both from academia and industrial side. The conversion of hydrogen into electricity can be realized using fuel cells. However, these systems are not suitable for fast load changes. This aspect limits fuel cells’ ability to smooth out overgeneration issues.
In this paper, an innovative closed-loop Brayton cycle integrated with an electrolyser is presented and described. The whole system is conceived as an electrical storage device in which the closed-loop Brayton cycle represents the discharging phase of the electrical energy converted and stored into hydrogen. The paper analyses this novel cycle under the thermodynamic point of view performing the optimization of the main parameters and evaluating its efficiency and performance in comparison with others electrical storage devices. The innovative contribution of the paper, compared to available literature, lies in the valorisation of the oxygen stream (usually discharged into the ambient) from the electrolyser in the Brayton cycle and in the recovery of the water vapour from the gas turbine.
On Hysteresis in a Variable Pitch Fan Transitioning to Reverse Thrust Mode and Back
Authors: Vitlaris Dimitrios , Rajendran David John , Tunstall Richard , Whurr John , Pachidis Vassilios 
Published: August 2024

Abstract
A novel hysteresis phenomenon during the transition to and back from the reverse thrust mode in a Variable Pitch Fan (VPF) is identified and characterised in this work. This is done by using a three-dimensional (3D) fully transient Unsteady Reynolds-averaged Navier-Stokes (URANS) with the transitioning fan blade aerofoils simulated by an adaptation of the mesh displacement method. A “real-time” simulation of the complete VPF hysteresis loop is achieved by specifying a blade wall motion through an Eulerian rotation matrix in differential, gradual steps, that is combined with a mesh probe-and-update routine for improved numerical accuracy and stability. The VPF is modelled to be transitioning in a modern 40000 lbf geared high bypass ratio turbofan engine architecture at “Approach Idle” engine power setting in a typical twin-engine airframe with the flaps, slats, and spoilers set for an aircraft touchdown airspeed of 140 knots.
The transition to reverse thrust mode involves flow starvation into the engine, formation of recirculation zones in the bypass duct and the establishment of the reverse stream, all of which occurs in the opposing presence of the free stream flow at aircraft touchdown velocity. The transition back to forward flow mode involves the gradual re-establishment of the free stream which is opposed by the presence of the reverse stream within the engine. It is quantified that in the transition to reverse thrust, the blockage develops with a larger time delay than the disappearance of the blockage during the transition back due to the interplay of the temporal dynamics of fan blade motion and flow field response. The details of the changes in the flow field behaviour, the effect of engine power setting and aircraft touch down velocity on the hysteresis behaviour are explained in detail in the paper. Additional manifestations of the hysteresis phenomena at reverse thrust involving engine spool-up and down, and aircraft acceleration-deceleration manoeuvres are also explored. The hysteresis phenomena described in this work are critical in properly developing control schedules to adapt for potential bi-stable flow field development during the landing run. The study addresses another part of the puzzle in exploring the feasibility of reverse thrust capable VPF engines for future sustainable aircraft to reach aviation climate neutrality.
On Leakage Flows in a Liquid Hydrogen Multi-Stage Pump for Aircraft Engine Applications
Authors: Lamprakis Dimitrios , Rajendran David John , Santhanakrishnan Mani , Coskun Seyfettin , Roumeliotis Ioannis , Pachidis Vassilios , Yates Martin 
Published: August 2024

Abstract
A comprehensive operational characterisation of a representative, Liquid Hydrogen (LH2) aircraft engine pump, a key enabler for future hydrogen aviation, is presented in this work. The implications of leakage flows are investigated in a 2-stage, high-pressure pump for a wide range of flow rates and rotational speeds, through 3D (U)RANS simulations. The study compares two configurations: a baseline model comprising the primary flow path components — inducers, impellers and volutes and a realisable pump hardware that includes hub, shroud and power unit cavities. Performance metrics, including head changes and efficiencies, are extracted both at a component and system level. Leakage flow rates of 27.6% and up to 92.9% of the overall pump flow rate are recorded at design and lowest flow points respectively. The head loss in the mid to low flow rates does not exceed 4.5%, but the efficiency diminishes by up to 13.5% at off-design operation. The component analysis indicates significant penalties in impeller efficiency. At high flow rates, the presence of leakage flows improves the overall pump performance by 43% and 27% in head rise and efficiency, due to reduced losses in volutes and connecting ducts. The detailed characterisation of pump behaviour described in this work is of importance in development of safe, reliable and predictable design of aircraft LH2 pumps. These aircraft pumps are different from LH2 pumps utilized in rocketry and for cooling in nuclear industry due to the requirement to operate with wider turn-down ratios and often at low specific speeds. Therefore, this study addresses design considerations in this enabling technology that ensures the delivery of pre-conditioned fuel according to the aircraft operating conditions.
Creep Properties of Nickel Alloys - Comparison Between Conventional and Laser Powder Bed Fusion Manufacturing Routes
Authors: Megahed Sandra , Okabe Erina , Kraemer Karl Michael , Kontermann Christian , Heinze Christoph , Oechsner Matthias 
Published: August 2024

Abstract
PBF-LB/M (Metal Laser Powder Bed Fusion) is a commonly used additive manufacturing process for gas turbine parts. This manufacturing method allows for small quantity batches with complex part designs. The mechanical behavior of PBF-LB/M components is strongly influenced by manufacturing process parameters, such as component geometry, build orientation and post-processing steps. However, these complex correlations are not completely understood — especially not for high temperature applications. The number of publicly available publications on creep properties of nickel-based alloys is limited. This knowledge gap affects the design and qualification effort of PBF-LB/M gas turbine components.
This study compares the creep properties of conventionally and additively manufactured IN738LC and IN718. The assessment of PBF-LB/M additively manufactured samples includes experimental data from two types of specimens (witness and extracted samples) in three build orientations. Extracted samples out of additively manufactured components allow the investigation of application relevant mechanical properties. Build directions studied are 0° (perpendicular to build direction), 45° (diagonal) and 90° (parallel to build direction).
The results show that the creep properties of PBF-LB/M manufactured IN738LC at 850 °C are affected by build orientation. Samples oriented parallel to the build direction show favorable creep properties, especially 45° build orientations have reduced creep life properties.
In comparison, the influence of build orientation is not as critical in IN718 and creep life properties at 650 °C are slightly superior to conventionally manufactured samples.
Acoustic Evaluation of Forward and Backward Swept Axial Fan Design for Automotive Applications With Identical Aerodynamic Performance
Authors: Sivaramakrishnan Anand , Bleiziffer Mihai , Girmscheid Felix 
Published: August 2024

Abstract
This paper introduces a pioneering approach to address a notable research gap in the realm of axial fan design for automotive application. Through a collaborative effort between Hanon Systems and Advanced Design Technology (ADT), advanced design techniques employing inverse design methodology were harnessed to develop axial fans with identical aerodynamic performance while minimizing acoustic emissions. The primary focus was on a comprehensive exploration and comparison of the acoustic behavior exhibited by forward and backward swept blade designs, set within a distinctive context.
The methodology encompassed the application of advanced turbomachinery design methods and inverse design principles. This innovative approach aimed to create fans that not only achieved identical airflow performance but also exhibited superior acoustic characteristics, all within the constraints of identical blade dimensions. The initial step involved a meticulous identification of key factors influencing fan performance and acoustics. A detailed design specification was then established, and advanced design optimization techniques were deployed to precisely adjust the blade geometry. This precision engineering ensured that the fans met desired specifications while maintaining similar aerodynamic performance.
Subsequent to the design phase, comprehensive simulations and experimental testing were executed to validate the designs. The focus was on comparing the aerodynamic and acoustic performance of forward and backward swept cooling fans, both designed to achieve identical aerodynamic performance. The results from these tests provided valuable insights into the acoustic aspects of axial fans, particularly in the context of automotive applications.
This research project stands as a substantial contribution to the field of acoustics in the automotive industry. It not only showcases the feasibility of designing axial fans with identical aerodynamic performance characteristics irrespective of blade sweep but also underscores the efficacy of advanced turbo design and inverse design techniques in achieving this outcome.
Numerical Analysis of the Boundary Layer Behavior of Low-Speed Linear Cascade Compressor Airfoils With Single and Tandem Configurations
Authors: Reisinger Lukas , Bieli Philippe , Gümmer Volker 
Published: August 2024

Abstract
A numerical design space study investigates the boundary layer behavior of highly loaded compressor airfoils featuring single and tandem configurations in a low-speed linear cascade with contracting endwalls. The study considers various Reynolds numbers, turbulence intensities, and blade loads. DLR’s CFD solver TRACE is used for the numerical simulations with a rotation-corrected k-ω turbulence model, Low-Mach preconditioning, and the γReΘ transition model. A robust method for evaluating boundary layer parameters is introduced, based on which representative reference airfoils are designed. Laminar flow dominates around the blade for small Reynolds numbers, turbulence intensities, and low boundary layer loading. As Reynolds numbers increase and turbulence levels rise, the transition progresses into the accelerated front portion of the blade’s suction side. The transition behavior and boundary layer development of the rear vane in a tandem configuration depends on the front vane’s boundary layer behavior. Lower Reynolds numbers correspond to increased boundary layer loading, and the presence of a maximum shape factor at the trailing edge varies with turbulence intensity and transition onset, influenced by the blade design. High turbulence intensities and small Reynolds numbers increase boundary layer thickness, affecting the interaction between front and rear vanes in tandem configurations. The entropy production per chord length in the boundary layer rises with decreasing Reynolds numbers and increasing turbulence intensity. The findings emphasize the need for distinct design guidelines for single and tandem configurations, considering the varying Reynolds numbers and boundary layer behaviors.
An Experimental Case Study in Combining Topology Optimization and Additive Manufacturing Techniques to Generate Novel and High-Performance Compact Heat Exchanger Designs
Authors: Rees Thomas W. , Azam Abdullah , Casari Nicola , Banks Polly , Jiranek Lukas , Furino Stefano , Muley Arun 
Published: August 2024

Abstract
The recent industrialization of additive manufacturing processes has led to research interest in alternative, more complex two-fluid heat exchanger designs, such as those constructed from repeating triply periodic unit cell geometries like gyroids, Schwarz minimal surfaces or other complex geometries. These types of designs are particularly convenient because their performance can be scaled up or down by including more or fewer periodic unit cells in the final heat exchanger lattice. Despite their complexity, repeating periodic unit cell-based heat exchanger designs have not been shown to have performance advantages over more traditional designs and therefore have yet to find widespread industrial application. This failure is partially due to the fact that the periodic unit cells used to build these heat exchangers are not optimized for thermo-fluid efficiency, as well as the fact that accurate simulation of a heat exchanger containing thousands of complex unit cells is extremely challenging, making the design of the overall heat exchanger difficult.
This paper presents the results of a project to develop a heat exchanger design method which can overcome these deficiencies. In particular, we design, build, and test a crossflow two-fluid heat exchanger based on a periodic unit cell designed using a proprietary topology optimization algorithm. The heat exchanger is manufactured using additive manufacturing. Analysis of the unit cell design showed that it generated secondary flows to increase the effectiveness of the heat transfer while also minimizing unnecessary loss-generating flow structures. The performance of the entire heat exchanger was simulated computationally using RANS-based CFD simulations on a single unit cell. The results of this simulation were used to build a reduced-order model to predict the heat transfer and pressure drop across the entire heat exchanger at two representative operating conditions.
After numerical simulation, the final design was manufactured from stainless steel using a Renishaw 500Q machine and its performance was measured experimentally. The experimental results are favorably compared against the numerical predictions to validate both the CFD simulations on the periodic unit cell as well as the reduced order model of the entire heat exchanger. This indicates that the topology optimization design process can be confidently applied to design scalable heat exchangers.