bluuebunny/crossref_metadata_2025_split huggingface dataset:
Wear it like armor and it can never be used to hurt you: Reappropriation, identity change, and collective action
Authors: Uysal Mete Sefa , Acar Yasemin Gülsüm 
Published: August 2024

AbstractReappropriation has been discussed as an identity management strategy as a means to reevaluate oneself in a context that will not allow for large‐scale social change. There are, however, numerous examples of reappropriation of stigmatizing labels as connected to political movements. This research examines whether reappropriation of stigmatizing labels can function as a precursor to collective action. In Study 1, we conducted semi‐structured interviews on the reappropriation of çapulcu identity with 20 Gezi Park protesters in Turkey. Interviews focused on how they recall the reappropriation of the word to have started, how they gave subsequent meaning, and how çapulcu identity predicted their protest participation and their broader politicization during and after the protests. In Study 2, we conducted a cross‐sectional survey on the reappropriation of fat identity by collecting data from fat liberation and body positivity activists in North America (n = 479). Reflexive thematic analysis (Study 1) and structural equation modeling (Study 2) showed that reappropriation of stigmatizing labels among activists is associated with a greater willingness to participate in collective action through increased agency, empowerment, and identity change. Findings provide important insights on identity management strategies and social change, and open new avenues to discuss reappropriation as a possible political strategy that might mobilize oppressed groups.
Development of an Efficient Compressor and Turbine for a 2MW-Class Emergency Gas Turbine
Authors: Kohama Takao , Anzawa Shuichi , Seki Yutaro 
Published: August 2024

Abstract
Emergency gas turbine generators manufactured by IHI Power Systems can promptly deliver large amounts of electricity during power outages, thereby playing a vital role in supporting society. When introducing these power generation devices into buildings located in city centers where installation space is constrained, a reduction in size becomes essential. As such, we have outlined a plan to downsize the existing 2 MW engine from NGT3 type to NGT2 type. To accomplish this, it is necessary to increase the output from the NGT2 type 1.6 MW to 2 MW, which entails a redesign of the compressor and turbine. This paper provides a detailed account of our efforts and the resulting outcomes of this undertaking.
Who Won the Race to Fracture – Torque Tube or Air Separator?
Authors: Gowreesan Vamadevan , Greaves Wayne 
Published: August 2024

Abstract
A gas turbine failed catastrophically at a process plant during operation. The failure resulted in the torque tube and air separator breaking into multiple pieces. The bolts connecting the torque tube to the air separator, the bolts connecting the torque tube to the turbine discs and the bolts connecting the torque tube to the compressor section also failed.
A detailed metallurgical root cause failure analysis was performed to understand what happened. The analysis included reconstruction of the torque tube and air separator from the broken pieces, and evaluation of all fracture surfaces. Based on the patterns seen on the fracture surfaces, the fracture mechanisms and crack propagation paths were determined for the torque tube and the air separator. Mechanical properties were tested using specimens extracted from the broken pieces. Microstructural evaluation was also performed. Similar analyses were performed on the broken bolts. Based on the fracture surface evaluation of the bolts, the bolt fractures were believed to be collateral damage.
Multiple preexisting cracks and a material defect were found in the torque tube. Fracture had propagated from one of these preexisting cracks in the torque tube. The question was if the torque tube fractured first, or the air separator fractured first.
The Effect of O-Ring Compression Set on the Rotordynamic Behavior of Turbomachinery
Authors: Simpson Christopher , Shakil Ali 
Published: August 2024

Abstract
For some aerospace applications, radial load support for high-speed turbomachinery is provided by gas foil journal bearings mounted on elastomeric O-rings. O-ring mounting provides several benefits including energy dissipation, thermal growth compensation, and higher bore misalignment tolerance. O-ring material selection requires careful consideration of application-specific factors to properly manage the synchronous and sub-synchronous response of the rotor bearing system over the lifetime of the application. O-ring material stiffness, bearing stiffness, operating temperatures, and environmental exposure are all relevant factors. Long-term exposure to operating environments can result in evolution of O-ring properties over time, including changes in stiffness, damping, and permanent compression set.
The objective of this work was to empirically characterize O-ring compression set behavior for a range of materials at a subscale level and to evaluate the associated effects on rotordynamic behavior at the assembly level. Subscale characterization efforts identified two materials with unique characteristics which were selected for further evaluation via full-scale assembly level rotordynamic testing. O-ring material characterization and high-speed rotordynamic test results are quantitatively evaluated, compared, and discussed to assess the suitability for use in future applications. Additional opportunities for continued validation efforts are also discussed.
Effect of Flexible Rotor Bucket Design on Savonius Turbine Performance
Authors: Grönman Aki , Bashyal Srijit 
Published: August 2024

Abstract
Savonius wind turbines are simple and robust devices suitable for a variety of climate conditions. Due to their low noise emission, they can be used in urban areas close to end users. However, their biggest drawback is their relatively low aerodynamic performance. One solution to this challenge is to use flexible rotor buckets. Public literature has shown that a wing’s aerodynamic performance can be improved by introducing flexible material; however, this idea has not been widely studied in the case of a Savonius turbine. Therefore, this work presents an experimental and analytical study determining how turbine performance is affected by the flexibility of the rotor bucket. In particular, the effect of the leading edge design is examined. In total, three rotor designs are studied in a continuously operated wind tunnel to reveal the effects of rotor design on the rotational speed and rotor deformation at different flow velocities. In addition, a correlation is developed to predict the turbine power coefficient under the measured operating conditions. The results suggest that a flexible membrane bucket can improve the performance of a Savonius turbine compared to a conventional rigid design. It is also found that the amount of leading edge flexibility can affect the optimal operating range. High-speed camera studies provide further insights into the bucket deformations during the operation of different rotor designs.
High Resolution Probe Measurements in a Multi-Stage Turbine Rig
Authors: Weggler Philipp , Bachner Johannes , König Franz-Xaver , Stephan Robert , Gmelin Christoph 
Published: August 2024

Abstract
This paper introduces the Rotating Turbine Rig (RTR) and presents the results of its first measurement campaign. The turbine test facility, NG-Turb, situated at DLR Göttingen, is described and a detailed description of the RTR setup is given. The measurement equipment and its associated uncertainties are examined. The focus of the results presented is on the aerodynamic design point of the 2½ stage high-pressure turbine. A typical test day operation and its stability and repeatability of the operational points are presented. Additionally, the investigation delves into the homogeneity of inflow and outflow. The reproducibility of measurements across different test days is compared, thereby illustrating the consistency and reliability of the experimental data. Finally, inter-blade flow fields measured by pneumatic probes is presented. Specifically, the study of the flow structures associated with tip flow leakage, purge flows, and cooling flows, and their interactions with the main flow is described. The high-resolution data is used to foster the understanding of multi-stage turbine flow.
Novel Alloying Strategy to Improve Brazing Properties on Nickel Based Superalloys for Aircrafts Turbine Application
Authors: Reker Dirk Wilhelm , Sowa Roman , Schwalbe Caspar , Seidel Frank , Moehwald Kai , Nicolaus Martin , Wackenrohr Steffen , Tillmann Wolfgang 
Published: August 2024

Abstract
The continuous improvement of high potential repair technologies is an essential driver for cost-effective and sustainable aviation. To withstand extreme forces and temperatures the turbine section of aircraft engines is made from Nickel-based superalloys. This class of materials routinely develops cracks and geometrical deviations in service which require a brazing repair, thus making brazing an indispensable key technology. This study seeks to improve brazing properties on Nickel-based superalloys for aircraft applications. Facilitated by materials simulation, a novel alloying strategy is outlined to design the braze alloy chemistry. The design criteria are established on the optimization of major microstructural properties influencing the mechanical properties known for repair brazed joints. The proposed design criteria were applied to the development of two new braze alloys. The new alloy design approach is validated experimentally by using the developed alloys. Mechanical properties of brazed samples made from Nickel-based superalloys were investigated at a service equivalent temperature of 871 °C. Results indicate that the ultimate tensile strength at 871 °C is 20.5 % higher than that published for legacy braze alloys. This study provides a basis for the development of repair technologies applicable to further superalloys.
Analysis of Irreversible Thermochromic Paints for High Temperature Applications Using Specular Reflectance and Roughness Measurement
Authors: Kossakowski Robert , Gier Stefan , Endrulat Benjamin , Voigt Matthias , Mailach Ronald 
Published: August 2024

Abstract
During the development process of a jet engine, it is critical to validate the thermal- and secondary air system. The validation requires an adequate measurement of the temperature distribution on hot end components, as combustor parts, turbine blades and vanes. Rolls-Royce is using irreversible thermochromic paints for measuring the spatial temperature distribution. The paint is a sensitive coating which irreversibly changes its characteristics with temperature and time on condition. For the prior art analysis process, the visual appearance of the paint is assessed and compared to calibration references for temperature prediction. This process requires special trained personnel and a standardised working environment. Previous research investigated the automation of the analysis process using imaging techniques. It is vital to explore these methods to increase the accuracy and precision of the measurement and accelerate the analysis process. However, especially for high temperatures, the change in colour is difficult to distinguish.
To supplement the visual analysis process, it is proposed to measure the specular reflectance and roughness of the surface in addition to the colour change. This paper investigates the correlation of these surface characteristics to temperature. Three frequently used paint types for high temperature application have been coated onto Nimonic®75 reference material, which have subsequently been heat-treated in a calibration furnace to generate solid state test pieces. The specular reflectance and roughness of the test pieces was measured with non-intrusive optical measurement devices. For all three paints, a correlation between reflectance and temperature was found. For roughness, the measurement suggests a correlation with temperature in higher ranges between 900 to 1200 °C. For validation, test pieces with a gradual temperature profile have been investigated. To include the effect of curvature, turbine blade test pieces have been measured and evaluated. The results show that measurement of the surface characteristics, like reflectance and roughness, contribute and supplement the analysis process especially in the high temperature range of irreversible thermochromic paints and hence aid the robustness and accuracy of the assessment.
Cluster Analysis of Acoustic Emission Signals From SiC/SiC CMCs Including the Introduction of Waveguides and the Effect of Material Changes Under Thermal Exposure
Authors: Quiney Zak , Gale Louise , Pattison Steven , Garcia-Luna Gonzalo , Newton Christopher , Bache Martin , Jeffs Spencer 
Published: August 2024

Abstract
Ceramic matrix composites (CMCs) have received significant attention due to their advantageous material properties for engineering applications where temperatures approach or exceed the working limits of traditional metals and alloys. An understanding of the damage mechanisms that accumulate within the material under complex mechanical and thermal stress conditions is therefore essential. Acoustic emission (AE) is one form of non-destructive evaluation (NDE) that is routinely used for such assessment. This paper investigates the application of pattern recognition tools to AE data obtained from monotonic tensile testing of SiCf/BN/SiC CMCs under thermal exposure in a range between room temperature (RT) and 1100°C.
Unsupervised pattern recognition in the form of k-means clustering was subsequently applied to the AE datasets in efforts to link different AE signal characteristics with damage mechanisms anticipated at specific stresses within the CMC. Due to elevated temperatures, AE waveguides were used in all tests. At RT, commonly occurring clusters were attributed to damage modes such as matrix cracking and interfacial debonding/sliding. At increasing temperatures, cluster activity remained broadly consistent until the effects of oxidation and thermally induced degradation of the material occurred between the temperature steps of400° and 600°C. Further differences were observed at 1100°C.
Comparison of Vortex Detection Methods on the Numerical Simulation of Tip Leakage Flow of a Low-Speed Axial Fan
Authors: Balla Esztella , Kovács Kinga Andrea , Lendvai Bálint 
Published: August 2024

Abstract
The present paper investigates the capabilities of the Lagrangian-Averaged Vorticity Deviation (LAVD) vortex detection method for turbomachinery applications. The tip leakage vortex of a low-speed axial fan is identified with multiple vortex detection methods. The investigation is carried out on a numerical simulation of a ducted fan. The results from the LAVD method are compared with the outcomes of the following vortex detection techniques: Q criterion, VR helicity density, vortex core distance technique of Li and Carrica, and Banks’ vorticity predictor-pressure corrector vortex core identification method. The position and extension of the vortex region and the location of the vortex core line are considered during the comparison. The results show that the vortex region and core detected by the LAVD technique are in great accordance with the outcome of the other methods. Compared to other methods, the advantage of the LAVD technique is that its parameters can be objectively defined from geometrical features of the flow field, e.g., blade chord length. The LAVD is also able to detect the core and the perimeter of the vortex region.
Experimental Characterisation of Surge Cycles and Second Quadrant Operation for a Centrifugal Compressor
Authors: Pronk Ola Ilseth , Bakken Lars Eirik 
Published: August 2024

Abstract
Accurate characterisation of compressor responses is critical for simulation studies involving flow instabilities. The positive-slope and second quadrant characteristics of a compressor dictate the performance of the compression system as the machine operates in an unstable condition. Conventional process simulation tools do not fully describe system behaviour beyond the surge line, as the compressor unit models omit performance losses incurred by surge and stall phenomena. The simulated response of events featuring flow instabilities will deviate from the actual system response unless the model is altered accordingly.
A major challenge of dynamic simulations at off-design conditions is related to the establishment of performance characteristics beyond the surge line. It is not possible to extrapolate correct transient responses without such characteristics. Empirical data quantifying key features of characteristics obtained at different operating conditions and system geometries are needed to resolve this challenge.
In this work, the performance characteristics of a single-stage centrifugal compressor operating in the first and second quadrants of the compressor map are exposed through an experimental test campaign. The trajectories of the operating point in the second quadrant and the development of surge cycles as the machine approaches and recovers from zero flow are highlighted. The impact of different discharge volumes on the transient and semi-steady compressor characteristics is documented. The volume of the plenum is shown to affect the response of the system in terms of oscillation amplitudes, frequencies, and phase shifts. Notably, it has little impact on the time-averaged semi-steady characteristics of the machine but greatly impacts the emergence of surge cycles. The experimental results provide a solid empirical basis on which novel modelling routines can be developed.
Multi-Stage Cyclic Symmetry Analysis of an Industrial High Pressure Turbine Assembly – Comparing Structural, Modal, and Solve Statistics
Authors: Bronson Jeffrey 
Published: August 2024

Abstract
Structural analysis of rotating turbomachinery geometry typically can take advantage of cyclic symmetry reduction to facilitate faster solve times and reduced result file size requirements. Historically, these analyses have been limited to decomposing the geometry to a single cyclic sector that shares a common sector count. Concessions are often made in these analyses (eliminating features that do not share a common sector count, artificially changing airfoil counts to force sector counts that are factors of each other, or modelling multiple sector that share a common factor together in a large segment — i.e. model a 1/3 sector) because the savings in solve time and file size reduction are invaluable versus trying to solve a full 360° representation of the geometry.
Multi-stage cyclic symmetry is a theoretical technique to create and analyze geometric models that consist of multiple cyclically symmetric structures that have different sector counts. This technique has been demonstrated on many simpler academic cases and has been shown to provide accurate results for a properly setup analysis model. The aim of this paper is to use the multi-stage cyclic symmetry approach on a full two row high pressure turbine assembly (consisting of non-proprietary geometry representative of an industrial assembly) to analyze both a static structural analysis for stress, as well as a modal analysis for natural frequencies and mode shapes. The paper will compare the results from running the same geometry as a full 360° reference case to check the multi-stage analysis for accuracy. Solve times, memory usage, and result file sizes will also be compared to show the benefits of using the multi-stage cyclic symmetry technique.
Evaluating the Energy Recovery Potential in Industrial Gas Pipeline Networks: A Preliminary Analysis of Gas Expander Applications for Nitrogen, Oxygen and Hydrogen
Authors: Baiguini Mattia , Doninelli Michele , Di Marcoberardino Gioele , Iora Paolo Giulio , Invernizzi Costante Mario 
Published: August 2024

Abstract
The aim of this work is to analyse the potential electrical energy that can be produced from the installation of expanders in the gas pressure reducing stations of industrial gases networks (oxygen, nitrogen and hydrogen). This solution is well established in natural gas grid but not yet implemented in existing technical gases networks. In the first part, the theoretical energy recovery potential is investigated by calculating the isentropic expansion specific power under different expander inlet temperatures and pressure ratios. Then the evaluation of adopting radial or axial expander is considered according to typical operating conditions: in particular, the design of axial expander is carried out with an open-source code. Eventually the design and the impact of the gas expanders solution is evaluated in selected industrial processes for each investigated technical gas. A discussion on practical issues is proposed. Radial expander could reach an isentropic efficiency of 89% while efficiency of 94% is obtained with an axial configuration with compact machinery. The application of gas expander in possible scenarios leads to annual energy production up to 19 GWh (O2 expander in blast furnace) with an utilization factor of 90% and cost of production ranges from 16 to 37 $/MWh with an avoided emission up to 1062 tCO2,eq/y. Results show an interesting potential for the proposed solution: however, the application strongly depends on adequate gas flow rate and operating pressure with a niche market now.
Introduction of Axisymmetric Grooves As a Tip Seal Treatment for Small-Core Turbines
Authors: Wiese Connor J. , Berdanier Reid A. , Thole Karen A. 
Published: August 2024

Abstract
The aerodynamic penalties associated with the tip gap flow in axial turbines remains a challenging problem for turbine manufacturers. As modern gas turbines with small-core architectures are brought online, the influence of the tip gap continues to grow. While technologies to reduce the losses associated with the tip gap flow have been implemented into the blades themselves, little attention has been paid to the stationary tip seal, or casing, around the rotor wheel. In this study, an introduction to the use of axisymmetric groove enhancements for the casing of the rotor tip are examined computationally. These studies use the National Experimental Turbine (NExT) geometry, an engine-representative high-pressure turbine blade.
Steady, Reynolds-Averaged Navier-Stokes simulations are used to assess the basic characteristics of axisymmetric grooves, such as depth, location, and arrangement. The objective of this introductory study was to determine the feasibility of impacting the tip leakage vortex formation and the associated losses in rotor efficiency. Furthermore, analyses were done with different tip gap heights along with both flat- and squealer-tipped blades.
Tip seals with a single groove are demonstrated to improve rotor aerodynamic efficiency relative to ungrooved seals by up to 0.4 points when applied to flat-tipped rotor blades and up to 0.15 points with squealer tips. Alternating arrays of grooves show improvements for flat-tipped blade performance by up to 0.76 points, while having little additional aerodynamic effect on squealer tip compared to the best single-groove designs. Finally, grooved tip seals appear to exert greater influence on the aerodynamic performance of the turbine rotor when at larger tip gaps, indicating that grooved tip seals alter the sensitivity of rotor performance to the tip gap.