bluuebunny/crossref_metadata_2025_split huggingface dataset:
On the Secondary Flow System of an Aggressive Inter Compressor Duct
Authors: Fritz Stefan , Dygutsch T. , Kasper A. , Hergt A. , Grund S. , Flamm J. , Lejon M. , Sahota Harsimar 
Published: September 2023

Abstract
In the last decades much effort has been spent in optimizing the performance of the rotating components of the compression system of civil aircraft engines. While these components are highly optimized, further improvements are limited. In this light, the interfaces between these components are coming into focus of research. Especially the inter compressor duct (ICD) is offering a high potential. Due to a more aggressive design, the length of the whole engine can be reduced. Shorter and thus lighter engines are leading to further fuel savings for the next engine generation. The design of current ICDs is very conservative because of high uncertainties in design space. An extensive test campaign on two very aggressive ICD designs has been conducted at an annular cascade at German Aerospace Center (DLR) Cologne to explore these limitations and a vast amount of test data has been gathered. The test section is comprised of LPC-OGVs, struts and HPC-IGVs. To simulate the influence of the last rotor of the LPC and to vary the incidence of the OGV, a move-able swirler is placed in front of the OGV. This simplification results in differences relative to a real rotor outlet flow. Through geometrical restriction, the ability to move the swirler can only be achieved by adding partial gaps in the rear part of the swirler at hub and shroud. These gaps have a huge impact on the secondary flow structure of the swirler outflow and therefore, the inflow of the ICD. In this paper, the secondary flow system of an aggressive ICD is analyzed in detail by the means of experimentally validated CFD simulations. Attention is given to the impact of the stationary swirler on the secondary flow system. Furthermore, a recommendation for future experimental setups with respect to the described effects is concluded.
Effects of Downstream Vortex Generators on Film Cooling a Flat Plate Fed by Crossflow
Authors: Straub Douglas , Weber Justin , Roy Arnab , Lee Chien-Shing , Shih Tom I-P. 
Published: September 2023

Abstract
Counter-rotating vortices, formed by the interaction of film cooling jets and the hot gas flow, adversely affect performance of conventional film cooling designs. In two previous papers (GT2020-14317 and GT2022-82675), downstream vortex generators consisting of rectangular plates arranged in a V-shaped pattern were shown to improve cooling effectiveness by mitigating effects of the counter-rotating vortices and by deflecting the cooling jet laterally. In this study, computational and experimental methods were used to examine how cylindrical film cooling holes (D = 3.2mm, L/D = 6, p/D = 3, α = 30°) with and without downstream vortex generators perform when the flow in the coolant supply channel is perpendicular to the direction of the hot gas. For this study, the hot gas had a temperature of 650K, and an average Mach number of 0.23. The hot-gas-to-coolant temperature ratio was 1.9, and two blowing ratios (0.75 and 1.0) were studied. Results from the CFD study show how crossflow affects the interaction between the film cooling jet and hot gas flow with and without downstream vortex generators. The experimental measurements were based on infrared thermography in a conjugate heat transfer environment. Results were obtained for film cooling performance in terms of overall effectiveness, film effectiveness, and local heat transfer coefficients. The downstream vortex generators can increase the laterally averaged effectiveness by a factor of 1.5 relative to cylindrical holes, but this higher performance is restricted to low crossflow velocities and higher blowing ratios.
Parametric Reduced Order Model of a Gas Bearings Supported Rotor
Authors: Goutaudier Dimitri , Schiffmann Jürg , Nobile Fabio 
Published: September 2023

Abstract
Gas bearings use pressurized gas as a lubricant to support and guide rotating machinery. These bearings have a number of advantages over traditional lubricated bearings, including higher efficiency in a variety of applications and reduced maintenance requirements. However, they are more complex to operate and exhibit nonlinear behaviors. This paper presents a parametric hyper Reduced Order Model (h-ROM) of a gas bearings supported rotor enabling to speed up the computations up to a factor 100 while preserving satisfactory accuracy. A Galerkin projection setting is employed to reduce the dimension of the governing equations and the nonlinear terms are efficiently tackled with a sparse sampling technique. The performances of the h-ROM are compared to a high fidelity model both in terms of accuracy and computation time, demonstrating the potential for future anomaly detection applications.
Experiments on Tuned UHBR Open-Test-Case Fan ECL5/CATANA: Stability Limit
Authors: Fiquet Anne-Lise , Schneider Alexandra P. , Paoletti Benoit , Ottavy Xavier , Brandstetter Christoph 
Published: September 2023

Abstract
Research of the past decades has shown that the operating range of modern fans and compressors is often limited by aeroelastic phenomena before the onset of pure aerodynamic instability. Prediction of these mechanisms is challenging for state-of-the-art numerical methods, particularly for configurations with flexible wide-chord blades. To provide a benchmark configuration for the community, the composite-material fan stage ECL5, representative of near future Ultra-High-Bypass Ratio architectures has been designed at Ecole Centrale de Lyon and recently shared as an open-test-case. In research program CATANA, different configurations with variable tuning and intake geometries are investigated experimentally, and here we present a comprehensive aeroelastic study of the tuned reference configuration. The study encompasses the investigation of the whole subsonic and transonic operating range using multi-physical instrumentation.
A characterization of structural properties under running conditions is analyzed in comparison to individual blade measurements and FEM-predictions. The stability limit is investigated at different speedlines. At transonic conditions, rotating stall occurred without aeroelastic precursors. Severe non-synchronous-vibrations were observed at subsonic speeds and limited the operating range before the onset of rotating stall. Through a detailed analysis of the aeroelastic coupling mechanism, a full characterization of interacting modes is presented. The challenging prediction of this coupled phenomenon and the discrepancy to aeroelastic simulations are discussed.
This paper is accompanied by a detailed aerodynamic study, and together a complete dataset including measurements of aerodynamic performance, radial flow profiles, blade-individual tip-clearance, stagger angle, vibration amplitudes and unsteady pressure fields at the rotor tip are provided. The results are a promising benchmark for future method development, particularly involving high-fidelity methods.
Spatially Resolved Modeling of the Nonlinear Dynamics of a Laminar Premixed Flame With a Multilayer Perceptron - Convolution Autoencoder Network
Authors: Rywik Marcin , Zimmermann Axel , Eder Alexander J. , Scoletta Edoardo , Polifke Wolfgang 
Published: September 2023

Abstract
This work presents a multilayer perceptron-convolutional autoencoder (MLP-CAE) neural network model, which accurately predicts the two-dimensional flame field dynamics of an acoustically excited premixed laminar flame. The obtained architecture maps the acoustic perturbation time series to a spatially distributed heat release rate field, capturing the flame lengths and shapes. This extends to previous neural network models, which predicted only the field-integrated value of the heat release rate. The MLP-CAE comprises two sub-models: a fully connected MLP and a CAE. The key idea behind the CAE network is to find a lower dimensional latent space representation of the heat release rate field. The MLP is responsible for modeling the flame dynamics by transforming the acoustic forcing signal into this latent space, enabling the decoder to produce the flow field distributions. To train the MLP-CAE, computational fluid dynamics (CFD) flame simulations with a broadband acoustic forcing were used. Its normalized amplitude was set to 0.5 and 1.0, resulting in a nonlinear flame response. The network was found to accurately predict the perturbed flame shapes — both under broadband and harmonic forcing. Additionally, it conserved the correct frequency response characteristics as verified by the global and local flame describing functions. The MLP-CAE provides a building block towards a potential shift away from a purely ‘0D’ analysis with the assumption of acoustic compactness of the flame. When combined with an acoustic network, the generated flame fields could provide more physical insight in the thermoacoustic dynamics of combustion chambers. Those capabilities do not come at an additional significant computational cost, as even the previous nonspatial flame models had to train on the CFD data, which readily included field distributions.
A Frequency-Time Partitioned Approach for Computing Fan Blade Flutter Induced Limit Cycle Oscillations With Nonlinear Friction on Contact Interfaces
Authors: Ombret Nicolas , Daon Renaud , Dugeai Alain , Thouverez Fabrice , Blanc Laurent 
Published: September 2023

Abstract
This paper aims at introducing a new methodology to analyse aeroelastic stability of transonic fans while nonlinear friction on contact interfaces is taken into account. This methodology consists in an iterative procedure where the nonlinear dynamics of the structure and aerodynamic forces are respectively computed while imposing each one to the other in a fixed point loop. Hence, both physics are resolved while taking into account the nonlinearities of the other one, leading to a description of the fully coupled fluid structure system nonlinear dynamics. To do so, a harmonic description of the structure dynamics is performed using nonlinear complex modes, while the fluid is evaluated in temporal domain solving Unsteady Reynolds Averaged Navier-Stokes (URANS) equations. Aeroelastic simulations are performed on the whole annulus, in Arbitrary Lagrangian Eulerian (ALE) formulation. An application of this methodology is performed on an industrial state of the art transonic fan to demonstrate its capability of predicting flutter induced Limit Cycle of Oscillations (LCO).
Low-Noise Design of Axial Fans Through Optimized Spanwise Application of Leading Edge Serrations
Authors: Felker Alexander , Biedermann Till M. , Kameier Frank 
Published: September 2023

Abstract
Recent studies have shown that leading edge serrations can effectively reduce broadband noise in axial fans and expand their operational range. However, additional aerodynamic losses have to be considered alongside the benefits of improved acoustic performance. The majority of studies focused on applying leading edge serrations along the entire span of the rotor blades regardless of local differences in radial inflow angles, deflection effects, and blade loading. In this regard, local and spanwise varying applications of leading edge serrations are considered crucial to reconciling maximum aeroacoustic and aerodynamic performance. In making these applications, a fan blade span is divided into five sub-segments. Each segment can then be equipped with either an acoustic or aerodynamic optimum as well as a baseline straight leading edge. Through testing at three different inflow turbulence levels along the full characteristic curve, an extensive statistical experimental design is executed. Ultimately, a simplified statistical model is derived. The model provides information on the optimum spanwise shape of a serration design. The results indicate significant effects of the local spanwise selection of varying serration designs. Discrepancies between aerodynamic and aeroacoustic optimum solutions can be satisfactorily resolved where, primarily, a significant extension of the working area is observed. Moreover, an extended potential in the delay of stall entry and the associated improvement of total pressure as well as a significant reduction of aeroacoustic signature is found. The underlying mechanisms are attributed to the compartmentalization effects of the serrations which restrict separation phenomena to local cells of finite spanwise extension. Furthermore, the spanwise geometrical parametrization of the serration segments correlates well with radial blade loading as well as respective flow conditions. By taking the radial distribution of aerodynamic quantities into account, an individual design of locally applied leading edge serrations can be integrated into the fan design process, enabling improved balancing between aeroacoustic benefits while maximizing aerodynamic performance.
Simulating Stall Inception in a High-Performance Fan
Authors: Bedke Andrew M. , Gorrell Steven E. 
Published: September 2023

Abstract
Aircraft engine performance and stability is limited by the onset of flow instabilities, such as rotating stall or surge. Although much research has been conducted on the subject, the mechanisms by which spike-type stall inception occurs in highspeed machines are still not well understood. This paper investigates the mechanisms of stall inception in a highly-loaded transonic fan rotor using full-annulus Unsteady Reynold’s-Averaged Navier-Stokes (URANS) simulations. Comparisons are made between the flow phenomena at the near-stall operating point and as stall inception occurs. The mechanisms of stall inception are shown to be interactions between the detached bow shock and the tip leakage vortex. These interactions result in two vortices within the blade passage near the rotor tips. The location and strength of these vortices affect leading edge spillage in the adjacent blade row. At the near-stall operating point, the vortices impact the pressure surface of the adjacent blade and then convect downstream. Stall inception occurs when the bow shock has moved far enough upstream to allow the resultant passage vortices from the shock/tip leakage vortex interaction to pass in front of the leading edge of the adjacent blade. After this, radial vortical structures are seen at the blade tips, much like what is observed in low-speed compressors. Understanding the mechanisms of stall inception in high-speed fans will allow for appropriate steps to be taken to delay stall inception and extend the stable operating range of the fan.
Hydrogen Co-Firing Demonstration at Georgia Power’s Plant McDonough: M501G Gas Turbine
Authors: Harper James , Cloyd Scott , Pigon Travis , Thomas Benjamin , Wilson Jeff , Johnson Eric , Noble David R. 
Published: September 2023

Abstract
As carbon reduction goals are being established worldwide with various target dates ranging from reductions by typical timeframes around 2030 to net-zero by 2050, the power industry is anticipated to lead the charge in reduction while having great demand placed from other industries. Many pathways to carbon-free power must be considered, as a portfolio will be necessary to keep energy costs low while keeping high reliability and widespread availability. As a subset, the gas turbine power industry is extremely interested in hydrogen as an alternative fuel to natural gas as a means of reducing, and eventually eliminating, CO2 emissions. Tests, up to full-scale demonstrations, are now being executed to further industry knowledge on co-firing natural gas with increasing levels of hydrogen. Challenges with blending high enough levels of hydrogen to make significant reductions of CO2 emissions will be numerous. This paper serves to provide information around the gas turbine performance, emissions, and emissions compliant load range effects of hydrogen on a Mitsubishi Power Advanced Class M501G gas turbine. The results of the testing are reviewed in the context of near-term needs such as operational flexibility with renewable penetration and the future energy transition considerations, particularly energy storage. The energy transition and the role of hydrogen in that transition has been mostly based on projections and small-scale testing. This paper provides additional practical information of the influence hydrogen has on gas turbine combustion and specifically the impact of hydrogen blending with natural gas on a large, modern high efficiency combined cycle power plant. Results of the testing provide needed and positive information on near-term and future energy transition needs. The results provide information valuable to the industry around operability and emissions expectations with hydrogen fuel usage.
Burst Speed Prediction of Impellers With Critical Strain Criteria
Authors: Sarıten Alper , Tabakçı Burak , Çopur Furkan , Kutmaral Alican , Akpınar İlkan Hasan 
Published: September 2023

Abstract
Accurate prediction of burst speed and critical location of a rotating disk is a great concern for turbomachinery designers and enables the reduction of test numbers required to show rotor integrity during turbo engine certification. Existing burst methodologies mainly focused on axial disks with well-defined bore, web, and rim regions and mostly depended on correction factors that require previous test data of rotors with similar sizes and features. Furthermore, variation of radial and hoop stresses in a radial disk is less predictable than in axial disks due to the asymmetric nature of impellers, which results in uneven distribution of centrifugal and bending loads. This paper aims to explain the experimental and numerical effort dedicated to building an accurate burst methodology for impellers. Elastoplastic finite element analyses are performed by incorporating geometric and material nonlinearities. Analysis results allowed the prediction of failure locations and observation of redistribution of stresses due to material plasticity as rotor speed increases. An extensive test campaign is carried out to validate the numerical analysis. Critical strain criteria, which corresponds to the plastic strain of true ultimate tensile strength (UTS), is used to determine burst speeds before tests. Experimental results are compared with Robinson’s Average Hoop Stress Criteria, Hallinan’s Criteria, and Critical Strain Criteria to show the strong and weak sides of these methodologies for an impeller application. The numerical burst speeds and crack initiation locations associated with critical strain criteria are found to be in good agreement with the spin test results.
Experimental Study on the Difference of Direct Damping Coefficients for Piston Ring End-Sealed Squeeze Film Damper With an Offset Groove
Authors: Zhang Guanghui , Huang Yanzhong , Sun Wenlong , Guo Yang , Gong Wenjie 
Published: September 2023

Abstract
The damping performance of squeeze film dampers (SFDs) is affected by feed hole distribution, feed pressure, and the number of feed holes. Common uncertainty differences exist between the direct force coefficients KXX and KYY, or CXX and CYY identified by the test. In this paper, the force coefficients identification test was carried out for a new piston ring end-sealed squeeze film damper with an offset groove. An original form of piston ring end seal, the double piston rings (DPRs), is tested and proven effective. The dimensionless direct damping coefficients CXX and CYY were identified using the instrument variable filter method (IVFM), and the absolute difference ΔC = abs (CXX – CYY) was calculated. Besides, the SFD damping performance was evaluated using the mean damping coefficient Cave = (CXX+CYY)/2. Last, the effects of feed hole distribution, feed pressure PH and the number of feed holes NH on the Cave and ΔC were investigated. The results show that the Cave and ΔC are affected by these factors. The Cave is larger (Cave &gt; 3.0 at NH = 1), and ΔC is smaller (ΔC &lt; 0.10 at NH = 1) when the feed holes are located upper than those located lower, and the more feed holes are located upper, the larger the Cave. In the low-pressure zone (PH &lt; ∼1.5 bar), the Cave decreases as the feed pressure increases and increases as the feed pressure in the medium and high-pressure zones (PH &gt; ∼1.5 bar). The Cave and ΔC can be slightly decreased by increasing the number of feed holes when the feed pressure is low, and yet the ΔC increases as the number of feed holes when the feed pressure is high. It is more effective to improve the damping coefficient by increasing the feed pressure than the number of feed holes, but the Cave will not increase significantly if the number of feed holes or feed pressure is increased continuously. The Cave and ΔC are related to the leakage and the evenly distributed form of internal oil, respectively. There may be a virtual threshold PNt that cannot be defined precisely for the feed pressure and the number of feed holes; the variation in feed pressure and the number of feed holes in the same direction results in a diametrically opposed pattern before and after this virtual threshold PNt, and the influence of the number of feed holes dominates the decrease of ΔC before the PNt. In contrast, the influence of the feed pressure dominates after the PNt. A sensitivity analysis reveals that the number of feed holes in the medium and high-pressure zones significantly influences the fluctuation of ΔC (ΔC fluctuates in the range of 0.17 to 1.45). Moreover, the factor of feed pressure at NH = 6 may lead to abnormal fluctuations of the ΔC.
Development of a Custom Mesh Generation Tool for Low Solidity Axial Flow Fans
Authors: Stephan Gideon A. , Van der Spuy Sybrand J. , Meyer Chris 
Published: September 2023

Abstract
This paper outlines a method used to generate a three dimensional, periodic, annular mesh for a large diameter, low solidity, axial flow fan. The meshing methodology generates a 2-D airfoil mesh at specified radial stations along the blade span. The 2-D airfoil meshes are stacked and wrapped to create the mesh of the axial flow fan. The 2-D airfoil meshing methodology inserts a blunt trailing edge to more closely match a physical fan blade where the trailing edge is not infinitely thin. The airfoil meshing algorithm uses airfoil characterisation, using Bezier spline regions, and extrusion to create a highly orthogonal near-wall mesh. A versatile spline relaxation method is developed to relax the mesh from the near-wall region to the far field geometry. The meshing tool is used to conduct an incompressible, steady state, Computational Fluid Dynamics (CFD) study of the B2a-fan using OpenFOAM. Correction factors are used to correct for the absence of the tip gap in the domain modelling. The corrected pressure characteristic was most accurate at the design point volume flow rate, attaining a deviation of 2.5% with a Grid Convergence Index (GCI) of 3.6%. The static efficiency was predicted with a deviation of 5% at the design point flow rate. The deviation in efficiency is caused by an increased static pressure rise due to domain simplifications leading to a lower blade torque. The blade swirl velocity showed good correlation with reference data with small deviations toward the blade tip.