bluuebunny/crossref_metadata_2025 huggingface dataset:
Radical internalism
Authors: Johnson King Zoë
Published: October 2022

In her paper “Radical Externalism”, Amia Srinivasan argues that externalism about epistemic justification should be preferred to internalism by those who hold a “radical” worldview (according to which pernicious ideology distorts our evidence and belief‐forming processes). I share Srinivasan's radical worldview, but do not agree that externalism is the preferable approach in light of the worldview we share. Here I argue that cases informed by this worldview can intuitively support precisely the internalist view that Srinivasan challenges, offer two such cases, and explain away the externalist‐friendly intuitions that Srinivasan's cases solicit. I then articulate and defend a “radical” internalism, arguing that internalists’ aversion to epistemic hubris and emphasis on subjecting one's beliefs to critical scrutiny are especially attractive in realistic cases involving multiple intersecting axes of oppression—that is, precisely the sort of case that permeates our social world. I also argue that externalism's lack of interest in action‐guiding principles leaves it with little to offer us in the fight against epistemic oppression.
Exposed Body Surface Area—A Determinate for UV Radiant Energy in Human UV Exposure Studies
Authors: Schmalwieser Alois W. , Schmalwieser Susanne S.
Published: October 2022

Solar ultraviolet (UV) exposure of people and related health risk is mainly examined by estimating the received UV radiant exposure. However, for several effects such as DNA damage, vitamin D photosynthesis or the probability of developing skin cancer, UV radiant energy is important and with that the size of exposed skin area. There is also a complex interaction between body shape and behavior like sun exposure habits, so that careful analysis is necessary when estimating health effects from UV exposure. In this paper, knowledge on body shape and methods of calculating the total body surface area (BSA) are summarized. BSA depends mainly on the height and weight of a person as well as on gender, ethnicity and body shape. BSA and body shape differ significantly between different populations and both change during life. This paper proposes formulas for BSA that consider height, weight, gender, ethnicity and body shape. As the exposed BSA depends on clothing, finally an approach is presented which aims to calculate the size of body parts released by real garments. In summary, this paper will enable future researchers to quantify the exposed BSA by best matching their study population and consequently investigate risks caused by solar UV exposure.
Policy dimension: A new concept to distinguish substance from process in the Narrative Policy Framework
Authors: Kuenzler Johanna , Stauffer Bettina
Published: October 2022

This article introduces the distinction between substance (questions of policy design) and process (questions of power in the policy process) to the Narrative Policy Framework (NPF). While both occur in existing NPF research, so far, they are not separated analytically. We conceptualize them as categories of the “policy dimension,” a new aspect of narrative content. Applying this dimension to an exploratory case, we show that such an analysis leads to useful insights for NPF scholars.Substancepolicy narrative elements show a debate about a policy's implementation model, whereasprocesspolicy narrative elements reveal that this debate is permeated by power conflicts. Furthermore, we find that the two categories' occurrence in narratives is influenced by the debate venue, whereas political parties as narrators do not seem to be relevant. The policy dimension allows for new research avenues and provides practitioners with a new tool to understand and intervene in policy debates.
Inequity after death: Exploring the equitable utilization of FEMA's COVID‐19 funeral assistance funds
Authors: Entress Rebecca M. , Tyler Jenna , Sadiq Abdul‐Akeem
Published: October 2022

As of March 2021, the United States had nearly 1 million COVID‐19 deaths. To aid families, the Federal Emergency Management Agency (FEMA) established the Funeral Assistance Program. Using publicly available data, we examine the equitable utilization of FEMA's COVID‐19 Funeral Assistance Program funding. Results show a significant relationship between FEMA COVID‐19 Funeral Assistance Program funding and some, but not all, social vulnerability components. Specifically, counties with higher percentages of the population with disabilities and higher percentages of minorities receive lower amounts of funding per 100,000 residents. These findings suggest that FEMA's equity efforts are not fully materializing regarding the utilization of the FEMA COVID‐19 Funeral Assistance Program funding among socially vulnerable groups. FEMA should broaden its social equity outreach and priorities for those not traditionally considered in social equity discussions, such as people with disabilities while continuing efforts toward traditional social equity.
The tapetal tissue is essential for the maintenance of redox homeostasis during microgametogenesis in tomato
Authors: Salazar‐Sarasua Blanca , López‐Martín María Jesús , Roque Edelín , Hamza Rim , Cañas Luis Antonio , Beltrán José Pío , Gómez‐Mena Concepción
Published: October 2022

The tapetum is a specialized layer of cells within the anther, adjacent to the sporogenous tissue. During its short life, it provides nutrients, molecules and materials to the pollen mother cells and microsporocytes, being essential during callose degradation and pollen wall formation. The interaction between the tapetum and sporogenous cells in Solanum lycopersicum (tomato) plants, despite its importance for breeding purposes, is poorly understood. To investigate this process, gene editing was used to generate loss‐of‐function mutants that showed the complete and specific absence of tapetal cells. These plants were obtained targeting the previously uncharacterized Solyc03g097530 (SlTPD1) gene, essential for tapetum specification in tomato plants. In the absence of tapetum, sporogenous cells developed and callose deposition was observed. However, sporocytes failed to undergo the process of meiosis and finally degenerated, leading to male sterility. Transcriptomic analysis conducted in mutant anthers lacking tapetum revealed the downregulation of a set of genes related to redox homeostasis. Indeed, mutant anthers showed a reduction in the accumulation of reactive oxygen species (ROS) at early stages and altered activity of ROS‐scavenging enzymes. The results obtained highlight the importance of the tapetal tissue in maintaining redox homeostasis during male gametogenesis in tomato plants.
D27‐LIKE1 isomerase has a preference towards trans/cis and cis/cis conversions of carotenoids in Arabidopsis
Authors: Gulyás Zsolt , Moncsek Blanka , Hamow Kamirán Áron , Stráner Pál , Tolnai Zoltán , Badics Eszter , Incze Norbert , Darkó Éva , Nagy Valéria , Perczel András , Kovács László , Soós Vilmos
Published: October 2022

Carotenoids contribute to a variety of physiological processes in plants, functioning also as biosynthesis precursors of ABA and strigolactones (SLs). SL biosynthesis starts with the enzymatic conversion of all‐trans‐β‐carotene to 9‐cis‐β‐carotene by the DWARF27 (D27) isomerase. In Arabidopsis, D27 has two closely related paralogs, D27‐LIKE1 and D27‐LIKE2, which were predicted to be β‐carotene‐isomerases. In the present study, we characterised D27‐LIKE1 and identified some key aspects of its physiological and enzymatic functions in Arabidopsis. d27‐like1‐1 mutant does not display any strigolactone‐deficient traits and exhibits a substantially higher 9‐cis‐violaxanthin content, which is accompanied by a slightly higher ABA level. In vitro feeding assays with recombinant D27‐LIKE1 revealed that the protein exhibits affinity to all β‐carotene isoforms but with an exclusive preference towards trans/cis conversions and the interconversion between 9‐cis, 13‐cis and 15‐cis‐β‐carotene forms, and accepts zeaxanthin and violaxanthin as substrates. Finally, we present evidence showing that D27‐LIKE1 mRNA is phloem mobile and D27‐LIKE1 is an ancient isomerase with a long evolutionary history. In summary, we demonstrate that D27‐LIKE1 is a carotenoid isomerase with multi‐substrate specificity and has a characteristic preference towards the catalysation of cis/cis interconversion of carotenoids. Therefore, D27‐LIKE1 is a potential regulator of carotenoid cis pools and, eventually, SL and ABA biosynthesis pathways.
A stripe rust fungal effector PstSIE1 targets TaSGT1 to facilitate pathogen infection
Authors: Wang Yunqian , Liu Cong , Du Yuanyuan , Cai Kunyan , Wang Yanfeng , Guo Jia , Bai Xingxuan , Kang Zhensheng , Guo Jun
Published: October 2022

Puccinia striiformis f. sp. tritici (Pst), the causal agent of stripe rust, is a destructive pathogen of Triticum aestivum (wheat), threatening wheat production worldwide. Pst delivers hundreds of effectors to manipulate processes in its hosts during infection. The SGT1 (suppressor of the G2 allele of skp1), RAR1 (required for Mla12 resistance) and HSP90 (heat‐shock protein 90) proteins form a chaperone complex that acts as a core modulator in plant immunity. However, little is known about how Pst effectors target this immune component to suppress plant immunity. Here, we identified a Pst effector PstSIE1 that interacts with TaSGT1 in wheat and is upregulated during the early infection stage. Transient expression of PstSIE1 suppressed cell death in Nicotiana benthamiana induced by VmE02 and PcNLP2. Transgenic expression of PstSIE1‐RNAi constructs in wheat significantly reduced the virulence of Pst. Overexpression of PstSIE1 in wheat increased the number of rust pustules and reduced the accumulation of reactive oxygen species (ROS), indicating that PstSIE1 functions as an important pathogenicity factor in Pst. PstSIE1 was found to compete with TaRAR1 to bind TaSGT1, thus disrupting the formation of the TaRAR1–TaSGT1 subcomplex. Taken together, PstSIE1 is an important Pst effector targeting the immune component TaSGT1 and involved in suppressing wheat defense.
Evaluating the relevance of surgical margins. Part one: The problems with current methodology
Authors: Bray Jonathan , Eward Will , Breen Matthew
Published: October 2022

The goal of cancer surgery is to achieve a “clean” microscopic resection, with no residual tumour remaining in the wound. To achieve that goal, the surgeon typically incorporates a measured buffer of grossly normal tissue about the entire circumference of the tumour. Microscopic analysis of the resection boundaries is then performed to determine if all traces of the tumour have been completely removed. This analysis is thought to provide a surrogate indication as to the likelihood for that tumour to recur after surgery. However, it is recognised that tumour recurrence may not occur even when microscopic evidence of tumour has been identified at the resection margins, and recurrence can also occur when conventional histology has considered the tumour to have been completely removed. The explanations for this dichotomy are numerous and include technical and practical limitations of the processing methodology, and also several surgeon‐related and tumour‐related reasons. Ultimately, the inability to confidently determine when a tumour has been removed sufficiently to prevent recurrence can impact on the ability to provide owners with confident treatment advice. In this article, the authors describe the challenges with defining the true extent of the tumour margin from the perspective of the surgeon, the pathologist and the tumour. The authors also provide an analysis of why our current efforts to ensure that all traces of the local tumour have been successfully removed may provide an imperfect assessment of the risk of recurrence.
Low Reduced Frequency Theory of Airfoils Vibrating in Complex Modes
Authors: Corral Roque , Blando Yago , Pitarch Aitor
Published: October 2022

This paper extends a previous study on the unsteady aerodynamics of vibrating airfoils in the low reduced frequency regime to the case of complex modes, where the phase of the different points of the same airfoil is not constant. A complex mode-shape can be expressed as the combination of two rigid body modes shifted 90 deg. Therefore, the stability of such modes is more complex to predict than that of the so-called real modes. The aerodynamic work-per-cycle has been deconstructed into its fundamental components, and its dependence on the reduced frequency described. The three distinct contributions to the work-per-cycle of a complex mode have been analyzed theoretically and numerically. First, the mean pressure yields a constant contribution to the work-per-cycle that is independent of the interblade phase angle (IBPA) and the reduced frequency. This term scales with the aerodynamic loading of the airfoil and is null for nonlifting airfoils. Second, the contribution of the two fundamental modes, whose mean value is proportional to the reduced frequency. Finally, the cross works of a fundamental mode over the displacements of the other. The low reduced frequency theory predicts that this term is independent of the frequency and symmetric with the interblade phase angle. The latter has been confirmed using linearized Navier–Stokes simulations, but the former has a constant term, as predicted by the theory, plus a small variation with the frequency that has been associated with acoustic resonances.
The Effects of High Centrifugal Acceleration on Bluff-Body Stabilized Premixed Flames
Authors: Erdmann Timothy , Gutmark Ephraim , Caswell Andrew
Published: October 2022

An experimental study is conducted on bluff-body stabilized premixed flames in a curved, square cross-section duct. High flow velocities coupled with a small radius of curvature of the duct induce high centrifugal acceleration normal to the flame sheet. A cylindrical flame holder spans the width of the square cross-section and is positioned at the channel mid-height. Flame shear layers are stabilized on the radially inward (upper) and outward (lower) edges of the flame holder. Side-view high-speed Schlieren images and high-speed pressure measurements are captured. Static stability, overall pressure loss, and statistics and velocimetry results from the Schlieren images are reported, and results are compared to a straight configuration with no centrifugal acceleration. Two bluff-body diameters are studied to show the effect of flame holder diameter on static stability. For the curved configuration, blowout velocities are higher for the smaller bluff-body diameter, likely due to flow acceleration effects. Blowout velocities are lower for the curved configuration compared to the straight configuration which may be due to the destabilizing Rayleigh-Taylor (RT) effect on the upper flame layer. Overall pressure loss is slightly higher for the curved configuration than the straight configuration. High-speed Schlieren results show centrifugal acceleration causes significant structural and velocimetric asymmetry in the bluff-body wake. In the curved configuration, the upper flame layer displays destabilizing RT instabilities, and the lower flame layer displays stabilizing RT effects. The upper flame shows vigorous RT instabilities which broaden the flame brush and sustain a flame leading edge independent of inlet Reynolds number or velocity. Conversely, the lower flame exhibits suppression of Kelvin-Helmholtz and flame-generated instabilities in the wake, which confines the flame brush and significantly reduces transverse flame velocities. The lower flame edge profile moves toward the channel centerline with increasing inlet Reynolds number. The upper flame in the curved configuration shows higher flame edge velocities than the straight configuration while the lower flame shows velocities closer to zero. The empirical constant to the power law relation for upper flame edge velocities agrees with RT-dominated flame growth theory for this experimental scale and agrees with other RT-dominated flame studies.
UHBR Open-Test-Case Fan ECL5/CATANA: Numerical Investigation Near the Stability Limit Including Aerodynamic Mistuning
Authors: Fiquet Anne-Lise , Ottavy Xavier , Brandstetter Christoph
Published: October 2022

Non-synchronous blade vibration (NSV) has received enormous attention in turbomachinery research, since it can be safety critical and its occurrence is less predictable than typical aeroelastic instabilities such as flutter. Typical for front stages of core compressors, NSV arises due to the propagation of one or multiple aerodynamic disturbances, traveling around the circumference and locking-in with structural blade vibration modes. Recent studies have shown, that modern low-speed fan architectures are also susceptible for this type of instability. With a specific focus on such aeroelastic instabilities, the open-test-case fan stage ECL5 has been designed by Ecole Centrale de Lyon. It is representative of near-future UHBR fan concepts with carbon-fibre composite blades. To prepare the experiments planned for 2022, unsteady full-annulus simulations have been carried out. Depending on rotation speed, the emergence of aerodynamic disturbances traveling around the circumference at a typical convective speed is observed, such as reported in studies on NSV on different configurations. These aerodynamic disturbances are identified as a possible source for non-synchronous vibration. At design conditions, an unstable aerodynamic behavior is observed, with part-span stall cells developing within the operating range predicted by RANS simulations. A study of intentional aerodynamic mistuning, in form of an alternating leading edge pattern is presented. At design speed, influence on steady performance and the onset of part-span stall is observed. At part-speed, the evolution of small-scale vortical disturbances, which can be responsible for the onset of NSV is affected significantly, providing a possible method to suppress NSV.
Predictions of Falling Wavy Films Based on the Depth Averaged Thin Film Model and Its Application to Aeroengine Bearing Chamber
Authors: Singh K. , Nicoli A. , Jefferson-Loveday R. , Ambrose S. , Paleo Cageao P. , Johnson K. , Mouvanal S. , Cao J. , Jacobs A.
Published: October 2022

In the present study, the evolution of a falling wavy film with upstream forced excitation is investigated using the depth averaged thin film model, known as Eulerian Thin Film Model (ETFM). Because of the depth averaging of the governing equations, coarse grids can be used in the wall normal direction. Consequently, this model is computationally efficient when compared to fully resolving thin films and hence highly advantageous for industrial simulations. In the case of a falling wavy film, film thickness and film velocity are closely coupled. A coupled solver that solves the depth averaged continuity and momentum equations simultaneously has been implemented with the provision to apply smoothing to the curvature of surface tension term to improve the accuracy and robustness of the model. The implemented model provides a stable solution for explicit as well as implicit temporal formulations. The performance of the newly implemented ETFM model is evaluated by comparing numerical results with experimental measurements and high-fidelity VOF simulations. The newly implemented model is found to be reliable in predicting free surface film profiles. It is 150 to 415 times computationally cheaper when compared to high-fidelity VOF simulations. The implemented and validated model is successfully used to predict a wavy film on the inlet of a representative aeroengine bearing chamber. The model is able to capture key flow physics on the front face of a static insert, which forms part of the bearing chamber inlet, and agrees well with experimental visualization of oil flow on the insert.
Impact of Upstream and Downstream Excitation and Multi-Row Interaction on the Mistuned Forced Response Behavior of an Embedded Compressor Rotor: Higher-Order Mode Aeromechanics
Authors: Hegde Shreyas , Zori Laith , Campregher Rubens , Kielb Robert
Published: October 2022

The current papers discuss the impact of separating the upstream and downstream forcing function contributions in an embedded compressor rotor. Previously, the authors have discussed separating the influence at a torsional mode crossing, and this paper expands this study to a higher-order mode crossing. This crossing occurs at a slower speed, and higher-order crossings are difficult to predict due to their low response for this configuration. The paper focuses on the multi-row interaction at multiple operating points and the mistuned blade response prediction. The computational model for this analysis uses the time transformation method within the commercial code CFX to help simplify the computational domain. The configuration chosen for this study is that the number of rotor blades and downstream stator blades have a common multiple, which allows the usage of a small number of passages in these rows. However, the upstream stator count does not satisfy this criterion. Hence, the time tilting method helps account for this difference in pitch and simplifies the computational domain. Both the upstream and the downstream rows excite the embedded rotor at different crossings. Additionally, the effect of wave reflection from a downstream or upstream row is considered. The responses are characterized at multiple operating points, i.e., nominal loading and high loading.

The second section of this paper describes the details of the in-house mistuning code utilized to predict the blade responses of the individual rotor blades in the system. One of the inputs to this code is the modal force obtained using unsteady CFD. The in-house code is based on the FMM, which couples both aerodynamic and structural dynamics to predict the blade responses. The key conclusions from this study were: 1) Physical wave reflections from the downstream stator were constructive at both the operating points. 2) The analysis at the 88EO crossing helped quantify the impact of physical wave reflections from a downstream rotating row. The influence was found to be destructive at both operating points, 3) The 3-row case with the downstream rotor in the computational model yielded the most accurate prediction of the blade response supporting earlier conclusions by the same authors that a downstream row was essential to predict the forcing function accurately.
Influence of Purge Flow Injection on the Performance of an Axial Turbine With Three-Dimensional Airfoils and Non-Axisymmetric Endwall Contouring
Authors: Schäflein Lukas , Janssen Johannes , Brandies Henri , Jeschke Peter , Behre Stephan
Published: October 2022

In this paper, we present the evaluation of the aerodynamic robustness to rim seal purge flow of an optimized 1.5-stage axial turbine configuration with a bowed stator profile and endwall contouring. Performance maps obtained by experiments and numerical simulations show that the efficiency benefit gained by this optimized configuration is partially reduced, but not eliminated, by the injection of purge flow through the cavity downstream of the first stator. Measurements with five-hole probes and hot-wire probes, as well as unsteady RANS simulations, give detailed insights into the physical effects of the purge flow inside the rotor passage. There, when no purge flow is injected, the optimized configuration diminishes the formation of loss-inducing secondary flow structures near the hub and the casing. When purge flow is injected, however, new strong secondary flow structures are induced near the hub. These vortices generate additional losses and thereby partially negate the efficiency benefits gained by the optimization. From the data, we found that this influence of the purge flow is limited to the lower half of the channel height. The data also shows that the optimized configuration is able to reduce the vorticity near the casing regardless of the purge flow injection, which in turn leads to an efficiency increase in this area. Together, these effects lead to a reduction of the previously gained efficiency benefit by the optimized configuration when it is subjected to purge flow injection. However, compared to a baseline configuration with cylindrical endwalls also subject to purge flow injection, the overall efficiency is still increased by 0.38%.
Hydrogen Thermal-Powered Aircraft Combustion and Propulsion System
Authors: Palies Paul P.
Published: October 2022

This article presents an assessment study of the propulsion system, the fuel distribution system, and the injector/combustor technologies enabling to eliminate CO2 emissions in aviation. In addition, the discussion is on NOx reduction methods and mitigation technologies, and a concept to fully eliminate NOx is proposed. To design and deploy an advanced thermal-powered aircraft based on liquid hydrogen fuel in future, it is important to provide key estimates that support feasibility of the methods and technologies developed and explored in this paper. This is conducted here for a typical narrow-body aircraft that will be retrofitted and considered. Once the design space and performance requirements are introduced, a compact low emission combustor including all components is discussed to operate with hydrogen swirled combustion to equip the turbofan engines of this conceptualized aircraft. The fuel tank is not only discussed with respect to the difference in power per unit volume and per unit mass between Sustainable Aviation Fuel (SAF) and H2 but also taking into account the Breguet range. This demonstrates that the volume of the tanks does not need to be four times more voluminous between H2 and SAF. The paper also presents a thermodynamics performance analysis for SAF fuel that is used to retrofit the engine with hydrogen fuel keeping inlet and outlet combustor stagnation temperatures equivalent. A method to derive the required flow split for future premixed combustor is described and conserve identical thermal power between SAF and H2 fuels. Flame stabilization critical challenges are also introduced.
Prediction of Thermoacoustic Instability and Fluid-Structure Interactions for Gas Turbine Combustor
Authors: Xia Yu , Sharkey Patrick , Verma Ishan , Khaware Alok , Cokljat Davor
Published: October 2022

This work simulates a laboratory-scale 3D methane/air burner, which features a bluff body stabilized, lean partially premixed flame experiencing strong limit cycle oscillations. A thin steel liner is installed around the combustion chamber, which heavily interacts with the flow field and produces large amplitude structural deformation via Fluid-Structure Interactions (FSI). An unsteady RANS approach uses the Shear Stress Transport turbulence model and a Flamelet Generated Manifold combustion model to predict the thermoacoustic oscillations in the turbulent reacting flow. The solver also has a built-in finite element Structure Model, which solves the structural governing equations simultaneously with the CFD-computed, finite volume flow equations. This way, a fully coupled, two-way FSI simulation can be performed to predict the thermoacoustic instabilities and the associated solid deformations in the burner. Overall, the predicted strongest pressure oscillation and wall displacement modes (frequency and amplitude) are all in good agreement with the experimental data across different operating conditions. The established workflow may support realistic gas turbine combustor design and prognosis.
Unsteady Structure of Compressor Tip Leakage Flows
Authors: Maynard Joshua M. , Wheeler Andrew P. S. , Taylor James V. , Wells Roger
Published: October 2022

Direct numerical simulations (DNS) are performed of a cantilevered stator blade to identify the unsteady and turbulent flow structure within compressor tip flows. The simulations were performed with clearances of 1.6 and 3.2 percent of chord. The results show that the flow both within the gap and at the exit on the suction side are highly unsteady phenomena controlled by fine-scale turbulent structures. The signature of the classical tip leakage vortex is a consequence of time-averaging and does not exist in the true unsteady flow. Despite the complexity, we are able to replicate the flow within the tip-gap using a validated quasi-three-dimensional model. This enables a wide range of quasi-3D DNS simulations to study the effects of blade tip corner radius and Reynolds number. Tip corner radius is found to radically alter the unsteady flow in the tip; it affects both separation bubble size and shape, as well as transition mechanisms in the tip flow. These effects can lead to variations in tip mass flow of up to10 percent and a factor of2 variation in dissipation within the tip gap.
Heat Transfer and Pressure Loss Correlations for Leading Edge, Jet Impingement Using Racetrack-Shaped Jets With Filleted Edges
Authors: Kulkarni Ritwik V. , Wright Lesley M.
Published: October 2022

This paper presents an experimental investigation of heat transfer and pressure loss for leading edge jet impingement using racetrack shaped jets. The majority of literature considers jet impingement using square, or sharp edged orifices, to create the jets. However, for gas turbine cooling applications, the edge of the jet orifices generally has some degree of filleting (or rounding) along the edges. The rounding may be a result of casting the airfoils or material wear due to long-term operation. In addition, within the engine, it is likely the jet orifice is not perfectly round. Engineers need data under realistic engine configurations to improve the utilization of coolant while adequately protecting the airfoil. The current experimental study is a parametric investigation of heat transfer and pressure loss for leading edge jet impingement. In this investigation, the effects of jet Reynolds number (Re = 10,000–100,000), jet-to-jet spacing (s/d = 2–8), jet-to-target surface spacing (z/d = 2–4), surface curvature (D/d = 2.67–5.33), and jet fillet-to-jet plate thickness (r/l = 0.16–0.5) are each considered. The inclusion of the fillet at both the inlet and outlet of the jet plate yields reduced heat transfer compared to the square edged jets. However, the fillets significantly improve the discharge coefficients associated with the racetrack shaped orifices. With the extensive testing completed in this study, design correlations have been developed to predict the surface Nusselt number and discharge coefficients including the geometrical parameters investigated in this study. The newly developed correlations accurately capture the geometrical effects and their deviations from the current experimental results are 10% and 19% for the Nusselt numbers and discharge coefficients, respectively. Engine designers can predict the level of heat transfer and pressure loss for leading edge jet impingement using these correlations.
Droplet Impact on a Curved Moving Liquid Film
Authors: Sinha Avick , Ramakrishnan Vaibhav , Johnson Kathy
Published: October 2022

The European Commission has set targets to reduce the emissions of CO2 and NOx by 75% and 90% respectively, per passenger kilometre, by 2050. Computational modelling of elements within the aero-engine will play a key role in achieving this goal. Currently, the computational models used to characterise impact outcomes from droplets splashing on wall films in bearing chambers are based on correlations obtained for droplet impacts on plane films. The present study bridges that gap, being the first experimental study investigating droplet impact on a film moving on a curved surface.

Experiments were conducted on a curved channel where the variation in the channel curvature provided the opportunity to investigate droplet impact at three different curvatures with three corresponding impact angles. Two droplet diameters of 2.34 mm and 1.90 mm were obtained using two different needle sizes attached to a syringe. The height of the syringe from the liquid film was varied to investigate the effect of droplet impact velocity. Five flow rates were considered to investigate the effect of film thickness on droplet impact. To investigate the dynamics of the droplet impact a high-speed imaging technique was used.

Qualitatively, two different impingement outcomes were observed, namely, crown formation and crown splashing. The key difference between the two outcomes is in the production of secondary droplets from the crown in crown splashing. Quantitatively, it was observed that at lower angles of impingement (less oblique), the transition from crown formation to crown splashing agrees strongly with previous literature for impact on static films and films on an angled plane where the transition value of the splashing parameter is 2100 based on the absolute velocity of the droplet. At the higher angles of impingement (more oblique), the critical splashing parameter (K) value was found to increase, as with droplet impact on an inclined surface or liquid film, but to a significantly higher value (2800 at 38°) than was typically obtained for an inclined plane (2400 at comparable angle). This indicates that the transition from crown formation to splashing at the highest radius of curvature is different to that of inclined planes at higher angles.

Investigating impact event duration, the present study suggests that with the increase in the impact energy, the time required for the film to come back to its original state increases.
The Modelling of Roughness Effect on the Performance of a Controlled Diffusion Airfoil
Authors: Delvaux Grégory , Toracchio Riccardo , Boufidi Elissavet , Croner Emma , Fontaneto Fabrizio
Published: October 2022

The manufacturing and operational roughness of aerodynamic profiles impacts both the laminar and the turbulent boundary layers state, directly affecting the aerodynamic and thermal performance of typical turbomachinery components. By better understanding the underlying physical mechanisms, the present work aims at building a more refined and comprehensive model to take the effects of surface finish into account. The model is implemented into the MIT Multiple blade Interacting Streamtube Euler Solver (MISES) and is validated against experimental results for different roughness levels, Reynolds number and Mach number regimes. In the proposed model, the roughness effects on the turbulent boundary layer (BL) state are included through the modification of the turbulent skin friction law, while the roughness level is implemented through a new definition of ks that accounts for the influence of the roughness skewness. Particular emphasis is placed on the modelling of the transitionally rough regime. Finally, roughness effects on transition are modelled by implementing the Mayle rough-induced onset transition criterion. Results are validated in terms of the total pressure loss coefficient and the outlet flow angle, leading to a marked improvement in terms of agreement with the experimental data.
Effects of Novel Roughened Wall of Swirl Cooling in Gas Turbine on Heat Transfer Characteristics and Pressure Drop
Authors: Elwekeel Fifi , Abdala Antar , Zheng Qun
Published: October 2022

In the present study the effects of ribbed and grooved walls of swirl cooling chamber on heat transfer and fluid flow characteristics are investigated. This study presents ten roughened wall shapes that are compared with a smooth wall in a swirl cooling chamber. The roughened wall shapes are circumferential and longitudinal with and without cut. The circumferential cases consist of four cases. The first case is called (CG) which has eight grooves along chamber surface. The second case is called (CGC) which has eight cut grooves along chamber surface. The third case (CR) and the fourth case (CRC) have eight ribs without and with cut along chamber surface. While the longitudinal cases, consist of six cases. The first four cases (LG, LGC, LR and LRC) have six longitudinal grooves and ribs without and with cut. The last two longitudinal cases (LRG and LRGC) have hybrid grooves and ribs without and with cut along chamber surface. The comparison is conducted by CFX software and the study parameters are bulk temperature, averaged circumferential heat transfer ratio, friction factor, global thermal performance factor and turbulence kinetic energy. The results show that heat transfer of cases LG, CG and CGC are enhanced by about 2.7, 2.6 and 2.5 higher than smooth case; respectively. The global thermal performance factor is increased by using rough walls in swirl cooling chamber, the global thermal performance factor of LG case reaches 2.8 times higher than that for smooth case. The maximum heat transfer characteristics can be achieved by a grooved wall of case LG compared with the other internal cooling techniques.
Comparison of Cast, Wrought and LPBF Processed IN718 Concerning Crack Growth Threshold and Fatigue Crack Growth Behavior
Authors: Brune Timo , Kraemer Karl Michael , Kontermann Christian , Oechsner Matthias
Published: October 2022

This study focuses on the influence of microstructure and ductility on the short crack behavior and the FCG threshold. For this, an additively manufactured batch of the nickel-based alloy IN718, made via Laser Powder Bed Fusion (LPBF) process, is compared to both conventionally wrought and cast IN718 material.

An initial characterization revealed significant differences in grain structure, from regular fine grained wrought material to large grains of several millimeters in diameter in the cast variant and a chessboard-like grain structure typical for LPBF. The ductility parameters of IN718-LPBF and wrought IN718 are comparable at room temperature, but at 650 °C the LPBF-variant shows macroscopic brittle fracture.

The fatigue crack behavior both in the short and long crack regime is investigated in air at 650 °C. To produce minimal crack growth increments of about 1 μm, a compressive pre-cracking and subsequent threshold test procedure with step-wise load increase has been adapted for high temperature testing.

To assess the short crack behavior, cyclic R-curves have been generated taking the influence of three different stress ratios (Rσ = −1, 0 and 0.5) into account. As expected, increasing crack closure mechanisms at higher stress ratios lead to higher stress intensity amplitudes ΔKI necessary to initiate crack growth. The crack growth resistance of the LPBF processed variant is higher compared to wrought IN718.

In the long crack regime, the wrought alloy yields higher crack growth rates compared to LPBF and cast IN718. An expected R-ratio dependency is observed for all material states.
Investigation of Water Films Shed From an Airfoil in a High-Speed Flow
Authors: Rodriguez Brandon Esquvias , Hickey Brendan , McDonell Vincent , Tabata Soichiro , Senoo Shigeki
Published: October 2022

The breakup of liquid films in high-speed flows are found in many applications. These include pre-filming air blast atomization found in fuel injectors and shedding of droplet off of airfoils. In this work, a test rig has been developed and applied to study the breakup of water films from the trailing edge of an NACA 0012 airfoil placed in a high-speed air flow. The results provided reflect a new detailed data set focus on air velocities above 75 m/s. Computational fluid dynamic (CFD) simulations were used to guide the development of the rig and the associated boundary and inlet conditions. In the present work, air velocities up to 175 m/s were used with water films between 0.4 and 3.6 cm2/s. The water film was introduced onto one surface through a series of 0.5 mm holes separated by 1mm at a location 35 mm downstream of the leading edge of the vane. High speed video was used to document the sheet breakup behavior from the edge of the airfoil. Image analysis was used to identify the breakup length of ligaments formed. Laser diffraction was used 50 mm downstream of the trailing edge of the vane to determine the droplet size distribution and associated representative average diameters generated. A series of test conditions were run between 50 and 175 m/s using multilevel factorial designed experiments. The results obtained were subject to analysis of variance to generate correlations for breakup length and droplet representative diameters as a function of the conditions studied. The analysis was conducted on dimensionless versions of the variables studied to help connect the results to the physics of the situation. For example, rather than using air velocity to correlate the behavior, the Weber number (based on gas phase density and velocity) was used owing to its historical ability to describe liquid breakup processes. The results obtained are compared with other studies in the literature, and good agreement was found for the conditions at which a comparison could be made. It is observed that, for the conditions studied, liquid film thickness has little effect on the resulting droplet sizes — especially for the higher air velocity cases studied. The results also illustrate the sensitivity to choice of characteristic length, which has generally consisted of trailing edge geometry or boundary layer thickness. In contrast, liquid film does influence the ligament breakup length, although the time to break up is less affected. Overall, the correlations developed provide engineering tools to help estimate ligament and drop size behavior for water films shed from airfoils in a high-speed flow.
Ensemble Learning Approach to the Prediction of Gas Turbine Trip
Authors: Losi Enzo , Venturini Mauro , Manservigi Lucrezia , Bechini Giovanni
Published: October 2022

In the field of gas turbine (GT) monitoring and diagnostics, GT trip is of great concern for manufactures and users. In fact, due to the number of issues that may cause a trip, its occurrence is not infrequent, and its prediction is a quite unexplored field of research. This is demonstrated by the fact that, despite its relevance, a comprehensive study on the reliability of predicting GT trip has not been proposed yet.

To fill this gap, this paper investigates the fusion of five data-driven base models by means of voting and stacking, in order to increase base model accuracy and improve prediction robustness. The five benchmark supervised Machine Learning and Deep Learning classifiers are k-Nearest Neighbors, Support Vector Machine, Naïve Bayes, Decision Trees, and Long Short-Term Memory neural networks. While voting just averages the predictions of base models, without providing additional pieces of information, stacking is a technique used to aggregate heterogeneous models by training an additional machine learning model (namely, stacked ensemble model) on the predictions of the base models.

The analyses carried out in this paper employ filed observations of both safe operation and trip events, derived from a large fleet of industrial Siemens GTs in operation.

The results demonstrate that the stacked model provides higher accuracy than base models and also outperforms voting by proving more effective, especially when the reliability of the prediction of base models is poor.
Experimentally Validated Design of an Anode Recirculation Blower for PEM Fuel Cells Under Variable Fluid Composition
Authors: Nachtigal Philipp , Kentschke Thorge , Seume Joerg R.
Published: October 2022

This paper focuses on the design, construction and the experimental testing of an anode recirculation blower (ARB) based on a turbo-compressor for PEM-FCs. The blower presented consists of a high-speed centrifugal compressor, driven by a so-called media-gap motor. Additionally it includes a droplet separator to eliminate liquid water from the anode loop. The aerodynamic design is based on 1D-correlations and 3D-numerical CFD simulations. Different gas compositions of hydrogen, nitrogen and water vapor are considered in the design, depending on the operating points of a PEM-FC. The gas composition has a significant influence on the achievable pressure ratio at constant compressor speeds, depending mainly on the specific heat capacity of the gas. Performance maps for different gas compositions are calculated using CFD for the designed ARB. A prototype is built and tested. The results validate the CFD predictions and show that the operating range of a PEM fuel cell can be covered with the present blower. In addition, it could be shown that an enthalpy-based approach using common characteristic numbers of turbomachines, allows converting performance maps — acquired with different gas compositions — into one another. This allows the performance map prediction for different gas compositions based on existing performance maps. This approach is illustrated by numerical and experimental results.
Comparison of Flame Describing Functions Measured in Single and Multiple Injector Configurations
Authors: Rajendram Soundararajan Preethi , Durox Daniel , Vignat Guillaume , Renaud Antoine , Beaunier Jérôme , Candel Sébastien
Published: October 2022

Recent investigations of combustion instabilities in annular systems indicate that considerable insight may be gained by using information gathered in single-sector experiments. Such experiments are, for example, employed to measure flame describing functions (FDFs), which represent the flame response to incident perturbations. These data may be used in combination with low-order models to interpret instabilities in multiple injector annular systems. It is known, however, that the structure and dynamical behavior of an isolated flame do not necessarily coincide with those of a flame placed in an annular environment with neighboring side flames. It is then worth analyzing effects that may be induced by the difference in lateral boundary conditions and specifically examining the extent to which the FDF data from single-segment experiments portrays the dynamical response of the flame in the annular environment. These issues are investigated with a new setup, named TICCA-Spray, that comprises a linear arrangement of three injectors. The central flame is surrounded by two identical side flames in a rectangular geometry with key dimensions, side-wall separation, and spacing between injectors identical to those of the annular system MICCA-Spray. The describing function of the central flame is determined with techniques recently developed in single sector experiments (SICCA-Spray). The FDFs obtained in the two configurations are compared for two swirler types having different swirl numbers and pressure drops. The effect of the swirl direction of the neighboring injectors is also explored by operating with co- and counter-swirl combinations. Differences between FDFs determined in the two test facilities, sometimes modest and in other cases less negligible, are found to depend on the flames’ spatial extension and interactions. The general inference is that the FDFs measured in a single-injector combustor are better suited if the flame-wall interaction is weak, and provided that the area is equivalent to that of a single sector of an annular combustor. Nonetheless, using a multi-injector system would be more appropriate for a more precise FDF determination.