bluuebunny/crossref_metadata_2025 huggingface dataset:
A Modified Fixation Method for Talonavicular Arthrodesis in the Treatment of Müller‐Weiss Disease: The Use of the Shape‐Memory Alloy Staple as an Adjunct
Authors: Lv Zhao‐Ying , Tong Yuan‐Hao , Wu Bai‐Hui , Zheng Yu‐Zhong , Lin Xiao‐Yong , Lin Yi‐Qiu , Zheng Chen Xiao
Published: August 2024

Objective

Arthrodesis, usage of metallic implants for internal fixation, is commonly employed as the primary treatment modality for Müller‐Weiss disease (MWD). Nevertheless, the efficacy of the current methods of fixation leaves room for improvement. Inadequate fixation strength and the risk of fixation failure are both critical concerns requiring attention. This study explored the clinical effects of implementing a modified fixation technique in talonavicular arthrodesis for the treatment of MWD.

Methods

A total of 14 cases diagnosed with MWD undergoing talonavicular (TN) arthrodesis from January 2021 toMarch 2023 were included in the retrospective study. The fixation method for fusion involved the use of screws, with additional support from the shape‐memory alloy (SMA) staple. Relevant clinical outcomes and complications were evaluated preoperatively and postoperatively. Paired‐samples t‐test was used for all data comparisons.

Results

Radiographic evidence confirmed solid fusion, and follow‐up evaluations showed satisfactory results in all cases. The American Orthopedic Foot and Ankle Society (AOFAS) scores were elevated from 32.21 ± 4.0 (range: 22–38) preoperatively to 86.5 ± 2.7 (range: 81–90) postoperatively (p < 0.001). The visual analog scale (VAS) scores declined from 7.40 ± 0.8 (range: 6–8.5) preoperatively to 1.21 ± 1.1 (range: 0–3) postoperatively (p < 0.001). The lateral Meary's angle changed from 13.50 ± 5.2 (range: 8–24) preoperatively to 4.14 ± 2.9 (range: 1–11) degrees postoperatively (p < 0.001). The calcaneal pitch angle increased from 10.07 ± 4.0 (range: 5–19) preoperatively to 14.35 ± 4.0 (range: 8–21) degrees postoperatively (p < 0.001). The talar‐first metatarsal angle decreased from 11.71 ± 3.8 (range: 8–18) preoperatively to 4.28 ± 3.1 (range: 0–9) degrees postoperatively (p < 0.001). One patient was observed to experience delayed wound healing and wound infection. No nerve damage, malunion, pseudoarthrosis, or fixation failure were observed.

Conclusion

The results indicated that the fusion of the TN joint using a combination of screws and shape memory alloy staples, could lead to favorable clinical outcomes and significantly enhance the quality of life for patients with MWD. This technique is not only safe and effective but also straightforward to perform.
Homogenization of word relationships in schizophrenia: Topological analysis of cortical semantic representations
Authors: Hayashi Ryusuke , Kaji Shizuo , Matsumoto Yukiko , Nishida Satoshi , Nishimoto Shinji , Takahashi Hidehiko
Published: August 2024

Aim

Patients with schizophrenia typically exhibit symptoms of disorganized thought and display concreteness and over‐inclusion in verbal reports, depending on the level of abstraction. While concreteness and over‐inclusion may appear contradictory, the underlying psychopathology that explains these symptoms remains unclear. In the current study, we used functional magnetic resonance imaging with an encoding modeling approach to examine how concepts of various words, represented as brain activity, are anomalously connected at different levels of abstraction in patients with schizophrenia.

Methods

Fourteen individuals diagnosed with schizophrenia and 17 healthy controls underwent functional magnetic resonance imaging to measure brain activity representing concepts of various words. We used a persistent homology (PH) method to analyze the topological structures of word representations in schizophrenia patients, healthy controls, and random data, across different levels of abstraction by varying dissimilarity scales in the representation space.

Results

The results revealed that patients with schizophrenia exhibited more homogeneous word relationships across different levels of abstraction compared with healthy controls. Additionally, topological structures exhibited a shift toward a random network structure in patients with schizophrenia compared with controls. The PH method successfully distinguished semantic representations of patients with schizophrenia from those of controls.

Conclusions

The current results provide an explanation for the mechanisms underlying the deficits in abstraction ability observed in schizophrenia. The isotopic connection of individual concepts reflects both the reduction of contextual connections at a semantically fine‐grained scale and the absence of clear boundaries between related concepts at a coarse scale, which lead to concreteness and over‐inclusion, respectively.
Planar Schrödinger–Poisson system with exponential critical growth: Local well‐posedness and standing waves with prescribed mass
Authors: Sun Juntao , Yao Shuai , Zhang Jian
Published: August 2024

This paper investigates a class of planar Schrödinger–Poisson systems with critical exponential growth. The conditions for the local well‐posedness of the Cauchy problem in the energy space are defined. By introducing innovative ideas and relaxing some of the classical growth assumptions on nonlinearity, this study shows that such a system has at least two standing waves with a prescribed mass. One wave is a ground‐state standing wave with positive energy, and another one is a high‐energy standing wave with positive energy. In addition, with the help of the local well‐posedness, it is shown that the set of ground‐state standing waves is orbitally stable.
The reciprocal relationship between political participation and mental health in Germany: A random‐intercept cross‐lagged panel analysis
Authors: Prati Gabriele
Published: August 2024

Purpose

Political participation has been identified as a predictor of mental health. Previous research studies have reported mixed results concerning the relationship between political participation and mental health. Moreover, findings have generally been confined to the between‐individual level. The few studies that investigated within‐person associations have not examined bidirectionality. In the current study, the bidirectional relationship between political participation and mental health was investigated.

Methods

Data from the GESIS Panel study were used to assess the bidirectional association between political participation and mental health. The GESIS Panel study is a probability‐based panel representative of the German‐speaking population residing in Germany and aged between 18 and 70 years (M = 44.52; SD = 14.67; 52 percent female participants). Mental health was assessed using measures of depression symptoms and subjective well‐being.

Results

Using up to nine waves of longitudinal survey data, a random‐intercept cross‐lagged panel model indicated little evidence for cross‐lagged effects from political participation to mental health or vice versa. Notwithstanding, few significant cross‐lagged paths were observed.

Conclusions

Overall, the findings were not consistent with the theorized effect of political participation on mental health. Moreover, there is little evidence that mental health affects political participation.
Identification of the novel HLA‐A*02:01:189 allele
Authors: Troiano Maria , Bianculli Antonio Giuseppe , Di Luzio Andrea , Pinto Rita Maria , Andreani Marco
Published: August 2024

HLA‐A*02:01:189 differs from HLA‐A*02:01:01:01 by one nucleotide substitution in Exon 3, codon 101 TGC > TGT.
Variation of Seismocardiogram-Derived Cardiac Time Intervals and Heart Rate Variability Metrics Across the Sternum
Authors: Mann Aysha , Rahman Mohammad Muntasir , Vanga Vineeth , Gamage Peshala Thibbotuwawa , Taebi Amirtahà
Published: August 2024

Cardiac time intervals (CTIs) are vital indicators of cardiac health and can be noninvasively assessed using a combination of electrocardiography (ECG) and seismocardiography (SCG), a method of capturing cardiac-induced chest vibrations via accelerometers. SCG signals can be measured from different chest locations. However, more investigations are needed to evaluate the impact of sensor placement on SCG-derived cardiac parameters. This study investigates the effect of accelerometer placement along the sternum on SCG-derived CTI estimations and heart rate variability (HRV) parameters. A semi-automated algorithm was developed to detect SCG fiducial points and seven CTIs from thirteen healthy individuals. Comparative analysis with manually selected peaks and gold-standard ECG was conducted to assess fiducial point detection accuracy. Results indicate the highest recall and precision in aortic valve opening (0.84–1.00 and 0.96–1.00, respectively) and mitral valve closure (0.77–1.00 and 0.93–1.00, respectively) detection. Aortic valve closure (0.43–1.00 and 0.61–1.00, respectively) and mitral valve opening (0.64–1.00 and 0.91–1.00, respectively) detection, although slightly less accurate due to signal intensity variations, demonstrated overall effectiveness compared to manually selected peaks. Furthermore, SCG-derived heart rates showed a high correlation coefficient (r > 0.9) with the gold-standard ECG heart rates. Single-factor ANOVA revealed significant differences (p < 0.05) in SCG-derived CTI estimations based on sensor locations on the sternum, highlighting the importance of sensor placement for accurate assessments.
Axial Flow Fan Performance in a Forced Draught Air-Cooled Heat Exchanger for a sCO2 Brayton Cycle
Authors: Boshoff Francois D. , van der Spuy Sybrand J. , Pretorius Johannes P.
Published: August 2024

An axial flow cooling fan has been designed for use in a concentrated solar power plant. The plant is based on a supercritical carbon dioxide (sCO2) Brayton cycle, and uses a forced draft air-cooled heat exchanger (ACHE) for cooling. The fan performance has been investigated using both computational fluid dynamics (CFD) and scaled fan tests.

This paper presents a CFD model that integrates the fan with the heat exchanger. The objective is to establish a foundation for similar models and to contribute to the development of efficient ACHE units designed for sCO2 power cycles. The finned-tube bundle is simplified, with a Porous Media Model representing the pressure drop through the bundle. Pressure inlet and -outlet boundary conditions are used, meaning the air flow rate is solved based on the fan and tube bundle interaction.

The flow rate predicted by the CFD model is 0.5% higher than the analytical prediction, and 3.6% lower than the design value, demonstrating that the assumptions used in the design procedure are reasonable. The plenum height is also found to affect the flow rate, with shorter plenums resulting in higher flow rates and fan efficiencies, and longer plenums resulting in more uniform cooling air flow.
Partially Cracked Ammonia Mixture Combustion in Gas Turbine Combustors
Authors: Gupta Sreenath , Weathers Timothy , Shahin Tristan , Gejji Rohan , Aithal Shashikant , Hosangadi Ashvin
Published: August 2024

Ammonia is gaining popularity for single fuel use in existing gas turbines, as it is carbonless, has higher hydrogen content per unit volume than liquid hydrogen, and facilitates easy storage and handling. However, the low flame speed of ammonia makes it prone to flame blow off and remains the chief concern for its use in power generation. Following previous studies that have shown improved combustion performance by partially cracking the fuel, in this computational study, efficacy of partially cracked ammonia as a replacement fuel for natural gas is evaluated.

A high-pressure optically accessible combustor operated at ∼10 bar pressure with non-vitiated heated air was used as the test platform. This combustor was equipped with a novel multi-fuel multi-tube micromixing injector (M3 injector). High resolution simulations of the flow fields both in the injector as well as the combustor were performed to understand the fuel mixing in the injector and in the inlet region of the combustor. These modeling results showed that the injector was highly effective for achieving mixture homogeneity at the entrance of the combustor for ammonia and natural gas injection, whereas, for hydrogen an earlier injection facilitating longer residence time would be beneficial. Also, these simulations show that while harnessing waste heat the ideal fuel dissociation fraction is between 0.4 and 0.55 for optimal operation.
Improving a Two-Equation Eddy-Viscosity Turbulence Model for High-Rayleigh-Number Natural-Convection Flows Using Machine Learning
Authors: Haghiri Ali , Xu Xiaowei , Sandberg Richard D. , Tanimoto Koichi , Oda Takuo
Published: August 2024

This study presents data-driven modelling of the Reynolds stress tensor and turbulent heat flux vector for improving unsteady RANS (Reynolds-averaged Navier Stokes) predictions of natural convection problems. While RANS-based calculations are cost-effective, conventional models fail to deliver the requisite predictive precision for high-Rayleigh-number practical engineering flows. To rectify this limitation, a gene-expression programming (GEP)-based machine-learning technique was employed to train novel models using a high-fidelity dataset from a vertical cylinder case with Ra = O(1013), which was generated using LES and validated against experimental data from Mitsubishi Heavy Industries (MHI). The newly developed data-driven closures for Reynolds stress and turbulent heat flux were then used to extend the realisable k-epsilon (RKE) turbulence model. The efficacy of these models was rigorously tested through a full a posteriori approach, involving URANS calculations with the newly constructed closures for the training case and two different testing cases. The results show that for cases with high Ra number (≥ 1011), the Nusselt number, temperature profiles, and velocity profiles exhibit significant enhancements due to the application of the GEP-based closures, initially developed using the Ra = O(1013) training case. However, for cases featuring lower Ra numbers, where standard RANS models already perform relatively well, the utilisation of the current data-driven closures becomes unnecessary, potentially even leading to reduced simulation accuracy. This investigation carries implications for cost reduction in the design process of thermal engineering applications involving high-Rayleigh-number natural convection flows.
A Practical Failure Approach of Burst Assessment of Aero Engine Disc
Authors: Yılmaz Okan Deniz , Savaş Cihan , Baldan Emre
Published: August 2024

The design of aero-engine disc is subjected to stringent regulations owing to their operation under high mechanical and thermal stresses. These structures must be designed as a fail-safe component with the aim of preventing incident. Regulatory authorities compel engine manufacturers to undergo spin-tests or coupon-tests on identical or similar discs to fulfill qualification and certification requirements. Spin-testing of aero-engine discs performs at increasing rotating speed, constant temperature and under vacuum conditions. However, these experiments are both costly and time-consuming.

The purpose of this paper is to present a practical failure approach aimed at replacing physical test facilities with simulations based on both implicit and explicit finite element analysis methods. Typically, burst calculations rely on the average hoop stress in axisymmetric regions. However, stress components in the axial and radial directions may exist in three-dimensional features. The model is employed to predict the burst speed, identify burst locations and role of stress concentration on the disc under varied operation conditions. In order to initiate damage accurately, considerations are given to factors such as crack driving force, plastic deformation, and stress triaxiality. Results obtained from both ANSYS and LS-DYNA solvers are utilized to ensure precise calculations of burst speed, location, and stress concentration factors. The findings of the structural integrity assessment of an aero-engine disc exhibit consistent agreement between each solver in term of crack propagation and the determination of critical speed.
A New Experimental Capability for Electric and Hybrid-Electric Propulsion and Thermal Management Research: The Surrey Aerothermal Test Facility (SATF)
Authors: Hussain Alishaan , Doherty John J. , Pekris Michael J. , Chew John W. , Hayden Paul
Published: August 2024

To support development of electric and hybrid-electric propulsion, the Surrey Aerothermal Test Facility (SATF) has been developed in recent years. The facility allows a powered model to be tested over an operating cycle, with measurement of steady state and transient effects. LabVIEW is used for facility and model control over extended test sequences and for synchronised data acquisition from multiple streams of data from different instrumentation. Novel measurement approaches have also been developed using the facility. These include use of embedded microphones to directly measure fan RPM, as subsequently used in the QinetiQ/Boeing/Surrey EMPAS project. Thrust performance has been investigated based on both direct force measurement and from integration of velocity measurements. IR sensors have been used to measure surface temperature variations on an electric motor, providing evidence of thermal soak-back. Heat flux sensors allow for the monitoring of thermal components and derivation of local heat transfer coefficients.

Use of the facility is highlighted through results presented from a series of Electric Ducted Fan (EDF) studies. An example modular EDF rig is described, which incorporates rotor and stator blade geometries designed using the MULTALL-OPEN turbomachinery design software and manufactured using low-cost 3D-print options.
Application of Interface Reduction Methods to Rotordynamic Casing Models
Authors: Paehr Martin , Panning-von Scheidt Lars
Published: August 2024

As the use of digital twins for the purpose of structural health monitoring increases, so does the demand for high-quality models. In the area of rotating machines, this means that the casing must also be taken into account. These are often geometrically complex assemblies that require the use of finite element models. The models are then reduced in size by established reduction methods like the Craig-Bampton reduction in order to keep the solution time, e.g. for a forced response analysis as low as possible. In case of nonlinear contact forces, e.g. friction in bolted joints, a secondary reduction step has to be applied. Here, three different interface reduction methods are investigated and used for a rotor-casing assembly including frictional damping. The necessary basics and terms are presented. The performance of the methods is evaluated for a linear model on substructure and assembly level and for a nonlinear model on the assembly level. The implementation of the interface reduction within the Harmonic Balance Method is presented and tested for different unbalance excitation cases.
A Rapid Test Facility for Transonic Compressors and Fans
Authors: Wang Tianhou , Taylor James V. , Miller Robert J.
Published: August 2024

This paper provides design recommendations for a rapid test facility for transonic compressors and fans, which aims to enable the testing of new geometries in two weeks at a cost of less than $10k. This compares to current industrial test facilities which typically take years and cost around $10M. The approach is important for its potential to unlock creativity allowing designers to ‘play’ at engine-representative conditions.

This paper is in two parts. The first part aims to physically enable rapid high-speed testing while preserving the key fluid dynamic mechanisms being studied. The complexity of a facility scales with its power input, driven by safety requirements and complex operations. A turboexpander-type subscale facility is designed to reduce the power by a factor of nine while achieving the full Mach number and a half of the full Reynolds number.

The second part aims to shorten the testing cycle time to under two weeks. It analyses the current testing process to identify the time-consuming parts and makes design changes to either eliminate or optimise each process.

The final test facility was demonstrated in a trial where an example rotor geometry with a tip Mach number of 1.2 was manufactured, built, and tested. The new geometry was tested in 2 weeks, incurring a marginal cost of less than $7k.
Accurate Modeling of the Flow Structures in the Gap Between Corotating Disks of a Tesla Turbine
Authors: Pahlavanzadeh Mohammadsadegh , Rusin Krzysztof , Wróblewski Włodzimierz
Published: August 2024

Momentum diffusion and kinetic energy transfer in turbomachinery have always been significant issues. These phenomena have a considerable effect on the performance of the bladeless Tesla turbine. Analyzing the flow inside the gap between the co-rotating disks of the Tesla turbine poses a challenge due to numerous factors, including sub-millimeter length scale, variation of flow cross-section, interactions of body forces arising from the rotation with the turbulence, interactions between the turbine’s inlet nozzles and rotor, and moving walls. Due to the mentioned reasons, the majority of the numerical research devoted to this problem diverges from the experimental data due to the limited accuracy of the implemented models. This research aims to study the flow in the domain that consists of one inlet nozzle and a part of one gap between the disks to reveal the complexity of the flow structures and their impact on the Tesla turbine performance. Large Eddy Simulation (LES) with the Smagorinsky subgrid scale model and k-ω SST turbulence model were employed to simulate the flow. The research compares the flow structure, flow parameters, and its impact on the performance of the system. The mesh strategy is also described since the LES requirements make this simulation computationally expensive and time-consuming. The overall benefit of this method is discussed.
Tribological Evaluation of Coatings for Air Foil Bearing Applications
Authors: Iakovakis Eleftherios , Aliasghari Sepideh , Bonello Philip , Matthews Allan , Burkinshaw Michael , Moore Simon
Published: August 2024

In the pursuit of environmentally friendly and sustainable transportation strategies, proton-exchange membrane fuel cells (PEM-FC) have emerged as a promising technology to decarbonise powertrains especially in heavy-duty vehicles. Oil-free bearings, the so-called Air Foil Bearings (AFBs), are crucial to the robust operation of the PEM-FC by preventing the contamination of the hydrogen fuel cell stack. However, during start-up and coast down of the PEM-FC, there is contact between the top foil of the AFB and the journal, which leads to high friction forces and durability concerns for the AFBs. The objective of this work is to identify the coating system that minimizes the friction forces for AFB applications. With this aim, tribological pin-on-disc tests were performed using coated Inconel discs and coated tool steel pins under room temperature conditions and at 150°C. Additionally, the development of a test rig to measure the tribological performance of coated AFBs under real life applications is discussed. In the pin-on-disc tests, the coated disc represented the top foil of the AFB while the coated pin represented the journal. Four solid lubricants were investigated for the discs, while two types of DLC coatings (monolithic and multilayer) were used for the pins. The worn surfaces have been investigated via microscopy and elemental analysis. The adhesion strength of the coatings was evaluated through indentation (VDI 3198) and scratch tests. The tribosystem of multilayer DLC against sulfur/molybdenum based solid lubricant coating afforded the lowest frictional response and friction stability compared to the other coating systems under evaluation.
Neural Network Application to Rotordynamic Predictions of an Overhung Flexible Rotor
Authors: Deiana Giulio , Vannini Giuseppe , Meazzini Giulia , Cangioli Francesco , Meli Enrico
Published: August 2024

This study focuses on pioneering regressive neural network models to predict lateral dynamics in a centrifugal compressor stage validation test bench. This tool is positioned as a critical resource to be used during the design of the centrifugal stage test, enabling test bench personnel to understand the rotordynamic behavior in terms of critical speeds and vibration amplitudes within the desired operating range. Addressing the demand for swift and manageable solutions for repeatable configurations within defined design parameters motivates this work. While Finite Element Method (FEM) analysis remains valuable, its time-intensive nature, particularly in model definition, drives the search for more time-efficient methods. Machine learning stands as an innovative, streamlined alternative for predicting lateral dynamics, differing from traditional approaches. The adoption of machine learning-based regressive neural networks marks a significant leap in analyzing centrifugal compressor lateral dynamics. This innovation not only boosts operational efficiency but also enhances accessibility and cost-effectiveness in the process.
Surge Detection of Centrifugal Compressor Using CFD Results
Authors: Shahriar Al , Wang Yintao , Yan Jin
Published: August 2024

In this study, a method has been proposed to generate surge lines based on the high-fidelity numerical simulation conducted for a refrigerant centrifugal compressor and later the results are compared against the experimental results. Surge, a violent flow instability at low mass flow rates, is often accompanied by severe detrimental effects including reduced efficiency, safety concerns, noise, and vibration on both the compressor itself and the overall system in which it operates. Conducting experiments for mapping a surge line often requires an extensive amount of time. In this paper, a surge line is mapped for a centrifugal compressor for a wide range of rotational speeds. The behavior of aerodynamically induced radial force and torque are used as the primary criteria for predicting the surge of the compressor. In this study, the pressure ratio and isentropic efficiency of the simulation results closely align with experimental results. Later, the radial displacement of the rotating shaft, a key indicator to identify surge, is obtained in the experiments for an oil-free magnetic bearing compressor. Finally, the surge line based on test data is used for evaluating the accuracy of the proposed method based on simulation results.
Application of Nonlinear Frequency Response Analysis for Windmilling
Authors: Kumar Devesh , Powell Don , Carlson David , Kumar J. S. , Cao Jianming
Published: August 2024

The current best practice across the aero industry is to model the windmilling event in a time-domain analysis. The alternative to time-domain methods is to use frequency response analysis which provides a great deal of information about the system response over the entire range of operation. However, the presence of non-linearities in the system makes it difficult to employ standard frequency response analysis techniques which are linear in nature. If the system contains mild-nonlinearities and the response of the system can be assumed to be periodic (which is usually the case for rotating systems), it is possible to obtain nonlinear frequency response of the system using harmonic balance techniques. Nonlinear harmonic response uses an iterative procedure to find the coefficients for the combination of sinusoids that form the steady-state response. Newton’s method of iteration is employed to solve a system of nonlinear algebraic equations. In addition to the harmonic balance technique, the continuation procedure method is required in the frequency response solver to capture the complete solution that consists of stable and unstable branches. This paper describes the improvements made in MSC Nastran for solving nonlinear windmilling problems and improve its robustness. The enhancements added to the software has made it possible to solve large scale production problems which was not feasible earlier.
Influence of Carbon on Structure and Stress-Rupture Properties of LW4280W and LW4280LCT High Gamma Prime Nickel Based Superalloys for a Tip Repair of Turbine Blades
Authors: Gontcharov Alexandre B. , Lowden Paul , Jena Ashutosh , Brochu Mathieu
Published: August 2024

The influence of carbides on microstructure and stress-rupture properties of high carbon LW4280W and low carbon LW4280LCT welds produced at ambient temperature GTAW at 649°C (1200°F), 872°C (1600), and 927°C (1700°F) are discussed in the current study. The study was powered by the need of using carbon for enhancing of creep strength of welds despite the well-known negative effect of carbides on high gamma prime superalloys weldability. In that context, a maximum carbon content of 0.12 wt.% has been maintained in many commercially available conditionally weldable superalloys. The current study demonstrates that the recently developed LW4280W superalloy with 0.17 wt.% C capable of producing 58–59 vol.% of gamma prime phase upon aging and the low carbon LW4280LCT comprising < 0.1 wt.% C and forming 54–55 vol.% of gamma prime phase during post weld heat treatment (PWHT) have excellent weldability. The high carbon LW4280W welds demonstrated superior creep strength to LW4280LCT welds despite the interdendritic precipitation of complex plate-like TaHf-based carbides during solidification of a welding pool. Our results show that PWHT resulted in a partial fragmentation of plate-like TaHf-based carbides, believed to enhance creep resistance. Despite having similar tensile properties, the time to rupture of test samples manufactured from LW4280W welds at 927°C (1700°F) under stress of 151.7 MPa (22 KSI) exceeded 156 hours while the LW4280LCT welds fractured in 112 hours. Our study also shows that exposure of heat-treated welds to a potential overheating to 1080°C (1975°F) during takeoff of aircrafts for total of 500 hours had little or no effect on the structure and tensile strength of both superalloys. The example of tip repair of turbine blade manufactured from the single crystal material and recommendations for using of LW4280W and LW4280LCT superalloys are provided.
A Numerical Investigation of Active Flow Control Strategies for the Suppression of Aerodynamic Flow Separations in a Very Aggressive Intermediate Compressor Duct
Authors: Kaliyaperumal Ananthakrishnan , Glodic Nenad , Gutierrez Salas Mauricio , Bergh Jonathan , Fritz Stefan , Hergt Alexander
Published: August 2024

Due to Intermediate Compressor Ducts (ICDs) potential to reduce overall engine weight and therefore specific fuel consumption, many aerospace industry participants have embarked on programs to develop shorter and more aerodynamically “aggressive” ICD. Unfortunately, most “aggressive” designs have tended to either separate or closely approach their separation limit. As a result, in this paper, the ability of active flow control techniques (boundary layer (BL) blowing and suction) were investigated and novel schemes were designed to suppress the flow separations and thus increase the aerodynamic robustness of such ducts. The test case used in this study is a state-of-the-art, highly aggressive, ICD developed by the Institute of Propulsion Technology, German Aerospace Center (DLR), located aerodynamically close to its separation limit operating at its nominal operating point. Numerical simulations were used to characterize the aerodynamic baseline of the duct as well as the modified design. Analysis of the baseline design results confirmed the strong tendency of the flow to separate at the hub-strut corner (corner separation), mid-strut (passage separation) and in the shroud (near duct exit) regions. Boundary layer energization schemes were then explored at different streamwise locations, to identify its optimum location. The results showed that the application of a BL energization scheme (BL blowing) on the hub resulted in a positive reduction in the passage and hub-strut corner separation while the application of BL suction (at the shroud) assisted in reducing the aerodynamic separations. Finally, when both schemes were employed simultaneously, an aggregated reduction of approximately 21% in the mass-averaged total pressure loss coefficient (compared to the baseline case) was predicted.
A Comprehensive Educational App for Propulsion Systems
Authors: Tsentis Spyros , Gaitanis Aggelos , Gkoutzamanis Vasilis , Kalfas Anestis
Published: August 2024

This paper presents the development of a multi-platform application for rapid aeroengine performance simulation which aims to reshape conventional educational processes in aerospace propulsion taught courses. This is facilitated by enhancing students’ interaction with a broad spectrum of propulsion concepts, ranging from subsonic to hypersonic regimes. The motivation of this app draws upon the ever-increasing use of smartphone apps among the student community. It is envisaged that this phenomenon could be beneficial to widen students’ knowledge. The user of the app can rapidly extract the thermodynamic and performance parameters at different operating conditions for several propulsion concepts, including conventional turbojets and turbofans, as well as ramjets, turboramjets and advanced, pre-cooled, combined cycle engines. The development process of the application as well as the built-in models are described in detail herein. The app is employed in an aeroengine technology course in Greece and used by the students to investigate the fundamental operating principles of advanced propulsion systems. These include a turboramjet, a hydrogen-powered ramjet as well as a hybrid, pre-cooled, air-breathing rocket-cycle concept. This is facilitated through the use of the app for the performance modeling of each one of the propulsive architectures. Results show that the impact of the app on the educational process is beneficial, with the vast majority of the students providing positive feedback. It is found that the app has far increased their interest and level of knowledge related to propulsion systems, in comparison to traditional teaching techniques. This would have been impossible in the time frame of an academic semester without the implementation of the app.
Rich Ammonia Flame Shapes and No Relaxation: Facility Development and Characterization
Authors: Cole Renee , Gubbi Srujan , Wu David , Emerson Benjamin , Noble David R. , Steele Robert , Sun Wenting , Lieuwen Tim
Published: August 2024

Ammonia (NH3) is a carbon-free fuel and hydrogen carrier; however, the presence of fuel-bound nitrogen has the potential to produce substantial nitrous oxide (NOx) emissions. Staged combustion, starting with a rich fuel reaction/decomposition zone, has the potential for low NO levels but can also lead to very significant NO levels if not designed correctly. This staged strategy takes advantage of the fact that equilibrium NO emissions from rich NH3 combustion are quite low. However, significant NO levels are still produced in rich flames and require a specific relaxation time, which can be quite long, to drop down to equilibrium levels. Thus, a key design attribute for ammonia combustors is sufficient residence time for NO relaxation. Given an overall combustor length, the NO relaxation zone is a direct function of the rich flame length, which can be quite long. Moreover, the flame length is a strong function of the flame stabilization location, e.g., the flame length in an annular swirling flow can easily vary by a factor of two depending upon the flame stabilization location. Moreover, swirl flames exhibit very long “tornado” configurations in certain conditions. For these reasons, even under conditions where the flame is stabilized, its configuration will dramatically influence the amount of time for the NO relaxation process. This paper introduces a test rig to explore flame configurations and post-flame NO relaxation for ammonia combustion. The rig features a modular swirler, a long primary stage, and a traversing emissions probe. The paper presents images of flame configurations over a range of conditions and maps different bifurcations in flame configuration.
Heat Transfer Evaluation on Turbine Vane With Corrugated Wall Impingement Structure Using Infrared Camera
Authors: Okamine Ryunosuke , Ito Ryuta , Mizukami Satoshi , Sakata Atsuya , Hada Satoshi
Published: August 2024

Impingement cooling is an effective technique used to cool hot gas path parts, minimizing the amount of cooling air required, and thereby improving the performance of gas turbines. However, crossflow from spent air of upstream impingement jets disrupts downstream impingement jets resulting in decreased heat transfer performance. To reduce the influence of crossflow, prior investigators have proposed using a corrugated wall type impingement structure.

Although fundamental tests of simplified corrugated wall impingement structures have been conducted in the past to confirm the basic cooling performance, it is desirable to verify the metal temperature distribution on an actual turbine vane cooled by a corrugated wall impingement structure. This study presents results from a turbine cascade test where pressure and suction side surface temperatures of an actual vane are measured using an infrared camera. Thermocouples mounted at different locations around the vane are used to correct the IR thermal image data. Based on these measurements, it was concluded that the corrugated wall impingement structure can achieve the target cooling effectiveness for both pressure side and suction side airfoil surfaces.
Forced Response of Bladed Disks With Excitation Variability
Authors: Xiao Yue , Panning-von Scheidt Lars
Published: August 2024

The prediction of forced vibration of mistuned bladed disks remains an important topic in turbomachinery design. The investigation of mistuning usually focuses on the blades in terms of their different structural properties. The excitation mechanism is considered to be mainly caused e.g. by the wakes from an upstream and the potential field from a downstream blade row. In recent years, it has been demonstrated that the Tyler-Sofrin modes (scattered or spinning modes) may affect blade forcing significantly and cause variable forcing amplitudes on individual blades in multistage turbomachinery. As a result, the vibration is localized at some of the blades forced by greater amplitudes, which leads to a higher risk damage for those blades. In this paper, the generation mechanism of TSMs is demonstrated and the effect of TSMs on blade forced responses is studied. Depending on the configuration of turbomachinery, excitation arising from Tyler-Sofrin modes may consist of different frequency components, which requires multiharmonic balance method (MHBM) to find the periodic solutions in presence of nonlinear blade couplings1. The methodologies for calculating linear and nonlinear FRFs are presented here on an academic bladed disk with shroud coupling, while TSMs is taken as part of the blade excitation.
Optimization of a Steam Turbine for Mechanical Drive Applications
Authors: Neil Adam , Rao Nikhil , Smith Paul
Published: August 2024

Axial flow steam turbines find wide application in several industries, such as oil & gas, petrochemicals, etc. The applications are primarily as mechanical drive turbines, to drive the process compressors. Because it is not feasible to design and optimize new hardware for each specific application, mechanical drive steam turbines are rarely clean sheet designs. These designs are developed from the available hardware inventory, which imposes certain geometric restrictions on the aerodynamic design and optimization of the flow path. Ensuring the mechanical reliability of the design is also critical to the functioning of the turbine. The modifications made to improve the reliability need to be executed with minimal impact to the performance. This paper will outline several concepts that form the basis of the aero-thermodynamic and mechanical design and optimization of mechanical drive axial flow turbines.
Geometric and Flow Characterization of Additively Manufactured Turbine Blades With Drilled Film Cooling Holes
Authors: McCormack Kelsey E. , Rozman Maria , Berdanier Reid A. , Thole Karen A.
Published: August 2024

As designers investigate new cooling technologies to advance future gas turbine engines, manufacturing methods that are fast and accurate are needed. Additive manufacturing facilitates the rapid prototyping of parts at a cost lower than conventional casting, but is challenged in accurately reproducing small features such as turbulators, pin fins and film cooling holes. This study explores the potential application of additive manufacturing and advanced hole drill methods as tools to investigate cooling technologies for future turbine blade designs. Data from computed tomography scans are used to non-destructively evaluate each of the cooling features in the blade. The resulting flow performance of these parts is further related to the manufacturing through benchtop flow testing. Results show that while total blade flow is consistent for all additively manufactured cooled blades, flow through smaller regions of the blades shows variations. Shaped film cooling holes manufactured using a high-speed electrical discharge machining method are within tolerance in the metering section but do not expand at the specified angle in the diffuser even though design tolerances are met. In contrast to high-speed EDM, conventional EDM holes are undersized throughout the length of the hole. Due to the additive manufacturing process, the surface roughness was higher on the additively manufactured parts in the current study than has been previously reported for surface roughness of commonly used cast components. The roughness results show high levels on thin walls, particularly at the trailing edge as well as on downskin surfaces. Internal surface roughness is higher than external roughness at most locations on the blade. The results of this study confirm that additive manufacturing along with advanced hole drilling techniques offer faster development of blade cooling designs.
On the Performance of Variable-Geometry Ducted E-Fans
Authors: Kavvalos Mavroudis D. , Schnell Rainer , Mennicken Maximilian , Trost Marco , Kyprianidis Konstantinos G.
Published: August 2024

Electrically-driven ducted fans (e-fans), either underwing-mounted or located at the aft-fuselage, can potentially improve the system overall efficiency in hybrid-electric propulsion architectures by increasing their thrust share over the thrust generated by the main engines. However, the low design pressure ratio of such e-fans make them prone to operability issues at off-design conditions, i.e. take-off, where nozzle pressure ratio is close or below the critical value. This paper investigates the operational limitations of such e-fans, proving the necessity of variable geometry. A component zooming approach is deployed by integrating a streamline curvature method within an aero-engine performance tool to investigate the e-fan installed performance and operability. The concepts of variable pitch fan (VPF) and variable area nozzle (VAN) are systematically explored to quantify any performance benefits, while the unavoidable added-weight challenges due to variable geometry are taken into account. Although e-fans with low design pressure ratio (PR) are more susceptible to operability issues compared to higher PR e-fans, the former show improved overall efficiency levels, mainly dominated by propulsive efficiency. It is found that variable geometry not only tackles operability but it can improve the off-design overall efficiency of e-fans even more. VPF mostly affects the component efficiency by reshaping the e-fan performance maps, while VAN has a greater impact on propulsive efficiency by moving the operating points.
Impact of Various Intake Configurations on the Flight Mission Performance of an Unmanned Aircraft
Authors: Remiger Jonas , Grois Andreas , Stößel Marcel , Kožulović Dragan , Krummenauer Michael
Published: August 2024

Well-defined intake-engine interfaces are of great importance in the aircraft design process. The focus of this paper is on various coefficients for data transfer at the aerodynamic interface plane (AIP) as a critical interface between the engine and the aircraft. To evaluate these coefficients, different intake geometries are modeled and simulated. The objective of the study is to provide a holistic view of the interactions between flight conditions, aircraft, intake systems and their effects on engine performance using previously generated computational fluid dynamics (CFD) results which are further used in the engine mission simulation system (EMSS). The effects of intake distortion on compressor behavior and engine performance are investigated using the parallel compressor model. All results of the investigation are obtained via the time-resolved simulation of an exemplary flight mission. The results first discuss the influence of flight conditions on the total pressure loss of each inlet and the corresponding behavior of the investigated distortion parameters. It is shown that not only the inlet geometry but also the coefficient used to represent the distortions in the performance calculation has an influence on the mission performance. Finally, it is shown that depending on the coefficient used to map the inlet distortion, there is a clear difference in the operating behavior of the compressor. The proposed γ coefficient predicts a critical approach to the surge margin. The DC60 would still suggest a safe operation of the compressor.
Large Eddy Simulation of an Open Fan Blade at Full-Scale Reynolds Number
Authors: Priebe Stephan , Jourdan Eduardo , Mousavi Arash , Karve Ravish , Chakrabarti Suryapratim , D’Aquila Luke , Yi Junsok , Alhawwary Mohammad , Bharadwaj Ananthan Varun , Ramakrishnan Kishore , Wood Trevor
Published: August 2024

Large-scale commercial turbofan designs are typically evaluated early in the technology maturation phase through subscale rig tests, while evaluations at full scale can only feasibly occur much later in a given engine development program. Therefore, how Reynolds number (Re) affects the aerodynamic and acoustic performance is of key interest while multiple candidate fan designs are still being evaluated and refined early in the program, and often tested scaled down to lower Re relative to the end application. To confidently evaluate full-scale Re performance however, large-scale physical testing is traditionally required because the high-fidelity simulations needed to capture the complex physics associated with high Re turbulent flows, such as wall-resolved Large Eddy Simulations (LES), are challenging due to the extremely high computational cost. In this paper, we present wall-resolved LES of an open fan blade at full scale for a highly loaded design operating at a condition representative of takeoff for acoustic considerations. The simulations are at high order (up to sixth) and have been performed using the unstructured LES solver, GENESIS. These simulations extend prior research to allow for a study of practically relevant flight scale Re, for which wall-resolved LES is now possible with computing capability available at the Oak Ridge Leadership Computing Facility (OLCF) exascale supercomputer, Frontier. The observed effects at flight scale Reynolds number of the flow physics on the blade and into the wake are presented in specific regions of interest that can affect the overall blade aeroacoustic design.