bluuebunny/crossref_metadata_2025_split huggingface dataset:
Real Time, Spatially Resolved Methodology for Flame Dynamics Investigation by Means of Fast Imaging and Image Processing
Authors: Ferrante Antonio 
Published: August 2024

Abstract
This paper presents an innovative tool for the study of flame instability phenomena based on high-speed imaging and image processing. The methodology underlying the system exploits the chemiluminescence radiation produced by the combustion reactions that occur in flames and which are detected by image sensors of high-speed cameras, speeds compatible with the oscillation frequencies of the phenomena we want to investigate. In general, for gas turbine burners the frequency range of interest varies from a few tens of Hz to a few hundred Hz. According to the author, the most innovative aspect of this methodology is that of providing the results of the analyzes in real time and not as a post-process activity. To achieve this result, most measurement analysis calculations are performed not on the CPU but on the GPU, drastically reducing calculation times and allowing the presentation of results in real time. Furthermore, the results presentation part provides a clear visualization of the oscillation modes of light intensity produced by the flame.
Study of the Total Temperature Redistribution in the Complex Swirling Flows
Authors: Karpenko Artem , Kukhtin Yurii 
Published: August 2024

Abstract
This paper reports the results of numerical investigation and analysis of the phenomenon of total temperature separation occurring in energetically isolated flows of compressible fluid. Numerical studies show that this phenomenon is also inherent in the flows of non-viscous ideal fluid in the presence of rotational motion of its particles. Based on the results of the analysis of the equations of motion of an ideal gas in a cylindrical coordinate system, using numerical results, conclusions are drawn about the causes leading to the redistribution of the total temperature in swirling flows of compressible fluid. Examples of flows with rotational motion of fluid particles, in which the studied phenomenon of total temperature redistribution is observed, are shown.
Investigation of Heat Transfer and Flow Characteristics in Rotating Combined Three-Pass Channels
Authors: Che Junxin , You Ruquan , Chen Wenbin , Li Haiwang 
Published: August 2024

Abstract
The combination cooling channels for the three-pass turbine blades are arranged based on the outer contour of the blades, with the flow area changing radially along the blades, and the channels arranged at certain angles to each other. In this study, the copper plate method was employed to investigate the heat transfer characteristics along the channels. The experimental fluid is air, and the maximum uncertainty of the Nusselt number is 7.99%. A detailed exploration of the flow and heat transfer patterns within the variable cross-section combined channels was conducted for Reynolds numbers ranging from 20,000 to 80,000 and rotation numbers ranging from 0 to 0.14. The research results indicate that as the flow area of the channel decreases, the flow accelerates, the disturbance effect of the ribs strengthens, and the heat transfer in the channel sharply increases. Rotation gradually increases the heat transfer difference between the leading side (LS) and trailing side (TS), but as the flow area decreases, the inertial effect strengthens, weakening the impact of rotation on heat transfer. Additionally, the numerical method was employed to study the coupling effects of each passage in the three-passage combined channels. The first passage and turning section enhance the turbulence of the flow but also introduce significant flow losses. Compared to split channels, the turning section leads to an increase in heat transfer in the second passage, but a decrease in heat transfer in the third passage.
Hybrid Electric Aircraft With Unlike Engine Degradation
Authors: Buescher Halle E. , Connolly Joseph W. 
Published: August 2024

Abstract
Control solutions are applied to uneven engine performance degradation on a conceptual twin-engine transport-class aircraft. Such degradation can lead to asymmetric thrust, which requires rudder trim to maintain desired aircraft heading. This will increase drag and fuel consumption. With the introduction of hybrid-electric aircraft powertrains, new solutions to unwanted asymmetric thrust can be derived. Four control strategies are demonstrated on the power and propulsion system of such an aircraft. Compared with existing strategies, the methodology proposed in this paper controls electromechanical actuators coupled to engine shafts and balances the thrust produced by both engines potentially leading to a decrease in fuel burn. The engine represented in this study is NASA’s conceptual dual-shaft Advanced Geared Turbofan 30,000 lbf thrust class engine. The conceptual engine is hybridized with electric machines attached to both shafts. Simulation results are presented with various levels of degradation. The control strategies are compared based on fuel burn, thrust symmetry, and estimated system weight.
Polynomial Chaos Expansion-Based Uncertainty Model for Fast Assessment of Gas Turbine Aero-Engines Thrust Regulation: A Sparse Regression Approach
Authors: Li Shijia , Wei Zhiyuan , Zhang Shuguang , Cen Zhaohui , Tsoutsanis Elias 
Published: August 2024

Abstract
Uncertainties in gas turbine aero-engines are unavoidable among which manufacturing tolerance is a typical manifestation. Uncertainties from manufacturing tolerance directly influence the thrust regulation performance, which may lead to the technical risks of newly produced aero-engines. Moreover, classic sample-based uncertainty quantification approaches are usually computationally intensive. In this paper, to consider the uncertainties in the control design phase in advance, a polynomial chaos expansion-based uncertainty model (PCEUM) using a sparse regression method is proposed to get the accurate probability distribution of thrust regulation performance and other concerned engine variables at a decreased computational burden. In PCEUM, engine variables are initially expressed as linear combinations of several orthogonal polynomials, whose weighting coefficients are solved by a sparse-regression-based method, i.e. orthogonal matching pursuit (OMP). A nominal aero-thermal model for a large turbofan engine, whose maximum errors for key engine parameters are within 2.25% against NPSS data, serves as the basis of PCEUM. Meanwhile, two classic sample-based uncertainty quantification approaches, (i.e. Monte-Carlo simulations (MCS), Latin hypercube sampling (LHS)) and a least angle regression (LARS) based PCE are set as benchmarks. Numerical simulations using publicly available manufacturing tolerance statistics are conducted at take-off states for the tested engine on a desktop computer. Results show that the proposed PCEUM costs only 47.06s at the expense of 200 samples to obtain stable probability distributions for interested engine parameters, e.g. thrust, whose errors of mean and standard deviation compared with MCS at 100,000 samples are within 0.01% and 1%, respectively. While the computational burden of MCS, LHS, and LARS are 854.63s at 9,000 samples, 250.13s at 3,000 samples, and 54.16s at 200 samples at the same precision level, respectively. It means that compared to the latter three methods, PCEUM can save 94.5%, 81.2%, and 13.1% of the simulation time, respectively. Hence, the proposed model is verified regarding both the accuracy and speed for uncertainty assessment, which provides a promising solution for both conventional gas turbine engines and future aero-propulsion systems.
Evaluation of Air Supply Conditioning Architectures for PEM Fuel Cell Systems in Aviation
Authors: Meyer Patrick , Lück Sebastian , Goeing Jan , Friedrichs Jens 
Published: August 2024

Abstract
This paper investigates the cathode air supply system of a medium-range fuel cell-powered aircraft. The main focus is on determining a suitable system architecture. Based on the literature, promising humidification and cooling strategies for cathode gas preconditioning are identified and evaluated. System configurations with membrane and spray humidification as well as intercooling between compressor stages and wet compression are calculated using a thermodynamic cycle calculation model. By analysing the design parameter spaces of the cathode air supply systems, the different configurations are compared in terms of their influence on key system parameters such as specific fuel and parasitic power consumption or heat exchanger size to find the most promising architecture. Further, the operating limits of the systems at different operating pressures and temperatures are determined. The second area of focus is the identification of a suitable system design point. It is discussed that the most critical operating points of the individual components are located at different flight conditions. Therefore, off-design performance is taken into account in order to design the entire system. A model based on the constant mass flow method is introduced to calculate steady state operating points for the system using membrane humidification. It can be seen that the turbo components have their design point at top of climb operating point, while the heat exchanger has to be designed for the maximum waste heat at take-off and the humidifier for the most critical operating point in terms of membrane water content at cruise.
Impact of High Freestream Turbulence on LPT Endwall Flow: Part I – Loss Development and Time-Averaged Flow Field
Authors: Donovan Molly H. , Marks Christopher R. , Fletcher Nathan , Rumpfkeil Markus P. 
Published: August 2024

Abstract
Realistic turbomachinery conditions include high levels of freestream turbulence; however, this aspect of the flow is typically overlooked in both low-pressure turbine (LPT) simulations and experiments. A better understanding of the impact of high freestream turbulence intensity (TI) on the endwall region of LPT blades is imperative. To fully assess the impact of elevated turbulence, three different incoming turbulence levels were examined at three different Reynolds numbers. Three planes of total pressure loss were measured downstream of the cascade mapping loss development. Surface pressure measurements were collected along the blade surface at midspan. Three planes of high-speed Stereoscopic Particle Image Velocimetry (SPIV) were acquired to investigate the impact varying incoming turbulence levels have on the endwall flow structures. Increasing the turbulence to the highest level was found to reduce the overall loss at the exit of the passage. The greatest impact of elevated freestream turbulence was observed at the lowest Reynolds number investigated. The time-averaged velocimetry measurements in the endwall region demonstrated that increasing the freestream turbulence intensity altered the locations of vortices throughout the endwall. Freestream turbulence levels must be increased, better matching real engine conditions, to get a more accurate prediction of pressure losses and flow topology when simulating the flow surrounding LPT blades.
Turbulent Burning Velocity of High Hydrogen Flames
Authors: Rajagopalan Hari Priya , Cole Renee , Wu David , Emerson Benjamin , Lieuwen Timothy 
Published: August 2024

Abstract
The turbulent burning velocity (ST) is one of the most important combustion properties controlling combustor operability limits, directly influencing blowoff, flashback, and combustion instabilities. Hydrogen has particularly significant influences on the turbulent flame speed. This paper presents new H2/CH4 data of high pressure, high hydrogen turbulent burning velocities. The data sets were designed to address fundamental questions as well as provide engineering/design relevant insights. This paper presents new scaling analysis of fuel composition, pressure, and preheat temperature effects on turbulent burning velocity. We also discuss the importance of considering what is being held constant (temperature, flame speed, Reynolds number, etc.) when one is analyzing these sensitivities. Data shows that hydrogen fraction and pressure causes an increase in turbulent flame speed; whether quantified as raw ST,GC, or normalized as ST,GC/SL,0 or ST,GC/SL,max, (where SL,0 and SL,max are the unstretched and stretched laminar flame speed respectively). We also propose that observed increases in ST,GC with pressure are due to increases in Reynolds number, and not a kinetics/stretch sensitivity effect. With increasing preheat temperature, ST,GC increases while its normalized value (ST,GC/SL,0 and ST,GC/SL,max) can either increase or decrease, depending upon fuel composition. We also show how these sensitivities vary, depending on whether these comparisons are made at constant raw turbulence intensity urms, or at constant normalized urms/SL,0 or urms/SL,max.
Unsteady Flow Mechanism of Non-Synchronized Disturbance During Gas Turbine Compressor Start-Up
Authors: Seki Ryosuke , Bonkohara Sho , Okui Hidetaka 
Published: August 2024

Abstract
In this paper, unstable unsteady flow phenomenon that occurs during startup in the compressor of a gas turbine for power generation are investigated in detail. After the rotating stall disappears during startup, a large-scale recirculating flow occurs very rarely at the tip of the 1st rotor over the entire circumferential direction. This stage mismatch causes a large-scale recirculating flow on the casing wall and thus, increases the gas temperature of the tip. This phenomenon ends as the rotational speed increases, and the condition stabilizes at the rated rotational speed, so basically it is not considered to be problematic. However, under certain IGV-VV schedule conditions, there is a rare risk of Non-Synchronized Disturbance (NSD) flow even at the rated speed. Based on these cases, the differences in aerodynamic unsteady flow mechanisms between large-scale recirculating flow and NSD flow were investigated using full annulus unsteady numerical simulations. Although it has been investigated in low-speed rig tests of axial and centrifugal compressors by researchers around the world, there are almost no reported cases in actual gas turbine compressors for power generation, and valuable knowledge about these phenomena was obtained in this paper.
In the case of the large-scale recirculating flow with a deeply closed IGV at 70% part-speed, the large recirculating flow occurs in the range over 75% span from hub (%Ht) to the tip from the leading edge to about 80% axial chord upstream.
On the other hand, if the IGV is half closed than the design opening angle at 100% speed, the reverse flow region occurs locally on the tip side near the leading edge of 95%Ht or higher in the 1st rotor tip. It was found that the rotation of the local reverse flow region in the circumferential direction causes NSD with a peak around 40%–60% of the 1st BPF. The NSD is caused by Kelvin-Helmholtz instability, which occurs when the shear layer between the leading-edge separation and the main flow oscillates.
The mechanism of the unsteady and unstable flow phenomenon which occurred at the start of the gas turbine compressor was clarified by the comparison analysis between the full annulus unsteady numerical simulation and the actual measurement. As a result, it is possible to clarify the direction of improvement measures and contribute to the gas turbine and turbomachinery communities.
Prediction of Steady and Unsteady Flow Quantities Using Multiscale Graph Neural Networks
Authors: Strönisch Sebastian , Sander Maximilian , Meyer Marcus , Knüpfer Andreas 
Published: August 2024

Abstract
Analysis, optimization and uncertainty quantification of the aerodynamic behaviour of turbomachinery components is a fundamental part of the current industrial design process and requires the extensive use of compute-intensive CFD simulations. In this paper we investigate whether graph neural networks can be useful as surrogate models to accelerate the design process, for example in a multi-fidelity framework. Graph neural networks promise to provide good estimates of flow quantities while maintaining the geometric accuracy at a fraction of the computational effort of classical CFD. An application to industrially relevant turbomachinery flows is performed to gain a good understanding of the capabilities and limitations of such methods. We therefore apply a state-of-the-art graph neural network to a turbomachinery setup of industry-relevant mesh size. In particular, a multiscale graph neural network is used to overcome the problems of large information distances when applying message-passing based graph-net blocks to large meshes. The database used to train the network consists of a space-filling DoE of 100 CFD solutions with different geometries. The first use case encompasses the prediction of the flow quantities of the complete fluid domain with 2.5e6 mesh points. The second use case focuses on predicting a single scalar (e.g. pressure or temperature) on surface meshes with up to 30e3 mesh points. In both cases, the networks are employed to predict time-averaged and unsteady flow fields on unstructured meshes of variable point sizes for new geometries not present in the training set. The results demonstrate the proficiency of the approach in predicting time-averaged and unsteady flow quantities on surfaces as well as for full fluid domains for new geometries.
A Dynamic Testing Approach for Particulate Erosion-Corrosion for Gas Turbine Coatings
Authors: Stokes Jamesa L. , Presby Michael J. 
Published: August 2024

Abstract
Particle interactions in gas turbine engines can be multicomponent, complex phenomena leading to the degradation of thermal (TBCs) and environmental barrier coatings (EBCs) meant to protect engine components. Ingestion of particles into the engine can lead to recession of coatings due to particle erosion. Similarly, these same particles can become molten, adhere to coatings and result in thermochemical corrosion of coating materials. Particle erosion testing is often carried out where the particles are injected into a gas stream, accelerated within a nozzle, and impinge on sample. Conversely, most molten particle corrosion testing is often done in static laboratory furnaces, which does not capture the dynamic nature of deposition in application. Nevertheless, these damage mechanisms are often tested separately and no single standard exists to test both erosive and corrosive particle interactions with coating materials under relevant operating conditions for gas turbine engines. Understanding the synergies of particle interactions in engines is crucial in determining operating lifetimes of potential coating materials. Such considerations emphasize the need for realistic approaches in standardizing particle interaction testing in combustion environments. The current study outlines initial efforts at NASA Glenn’s Erosion Burner Rig Facility in improving dynamic erosion/corrosion testing methods by assessing the durability of state-of-the-art (SOA) TBC material 7 wt.% yttria stabilized zirconia (7YSZ) as a function of particle deposition rate, burner temperature, and particle size. Calibration data to determine particle deposition rate will be presented, and mass and optical profilometry measurements were utilized to estimate mass/volume loss versus deposition per increment of particulate used over time. Electron microscopy analyses were then carried out to assess coating damage after testing.
Temperature Margin Calculation During Finite Element Creep Simulations
Authors: Day William , O’Nora Nathan , Gordon Ali P. 
Published: August 2024

Abstract
Creep deformation in turbomachinery applications is a highly non-linear phenomenon. Very small alterations in stress or temperature will substantially change the progression of creep. Common rules-of-thumb would suggest that a change in temperature of +/−10 to 15°C may halve or double the average rupture life respectively. Even in well-controlled laboratory conditions the stochastic nature of creep means that identical tests may differ by a factor of two. Even if an analyst has incorporated a very accurate creep model into an implicit finite element user creep subroutine, they may lack an appreciation of the uncertainty of their solution, or the design changes required to account for uncertainty in either the boundary conditions or the solution itself. Common practice would be to design with maximum strain limit, which may be inadequate given the sudden acceleration of tertiary creep rates. Alternatively, analysts might apply a time factor to their model, necessitating extending the simulation time by factors of two or more. This paper will present a methodology where two estimations of the progression of creep damage are made in parallel to the creep simulation at actual operating temperatures. These two estimations consider the predicted change in stress relaxation at higher or lower temperatures to provide the analyst with an estimate of what change in temperature would result in the model being at the onset of creep at any given node in the model, at any given time in the analysis. This margin calculation is then further expanded to consider the margin required to account for the uncertainty in analytical creep prediction. A time-based scatter factor is then incorporated into the temperature margin calculation to provide a minimum temperature margin including model uncertainty. The analyst is then free to also consider the uncertainty of the temperature prediction and boundary conditions to produce a robust creep prediction in a real-world simulation. The methodology is validated through FEA of example cases and has been applied to the analysis of a creep limited 2 stage industrial gas turbine blade.
Effects of CMAS Application on the Isothermal and Gradient Thermal Cycling Behavior of a Yb2Si2O7 EBC
Authors: Presby Michael J. , Stokes Jamesa L. , Harder Bryan J. , Setlock John A. , Hammel Jeffrey R. 
Published: August 2024

Abstract
Environmental barrier coatings (EBCs) are critical to the continued advancement of gas turbine hot section materials technology. EBCs are required to protect Si-based ceramics such as silicon carbide fiber-reinforced silicon carbide (SiC/SiC) ceramic matrix composites (CMCs) from oxidation and corrosion in the combustion environment. One of the current challenges concerning EBC lifetime is the thermochemical reactions between calcium-magnesium-aluminosilicate (CMAS) deposits and the EBC that leads to changes in both composition and stress state. These changes can severely reduce the integrity of the EBC leading to crack formation, delamination, and spallation. Current techniques for evaluating CMAS in the laboratory rely on the pre-application of CMAS. Two commonly used application methods to deposit CMAS on EBC materials are tape-cast and air spray. In both methods, the CMAS is applied to the EBC surface at ambient temperature, and then subjected to a heat treatment process for binder burnout. The purpose of this study is to compare the tape-cast and air spray methods on the CMAS corrosion of a ytterbium disilicate (Yb2Si2O7) EBC exposed to isothermal, and gradient thermal cycling. The results highlight if any differences exist in the CMAS infiltration kinetics between the two application methods.