bluuebunny/crossref_metadata_2025_split huggingface dataset:
Experiment on Tuned Open-Test-Case Fan ECL5/CATANA: Structural Characterization Under Vacuum Conditions
Authors: Billon Kevin , Sanchez Lionel , Bouvard Gaëtan , Gibert Claude , Blanc Laurent , Thouverez Fabrice 
Published: August 2024

Abstract
The CATANA project aims to promote the development of the next generation of Ultra-High-Bypass-Ratio Turbofan engines by closing the knowledge gaps concerning multi-physical interactions which affect performance and limit the stability range. It involves a composite-material fan stage, called ECL5, representative of near future UHBR architectures. It has been designed at Ecole Centrale de Lyon to provide an open for the community benchmark configuration. This fan had been extensively tested previously at the aerodynamic Phare-2 test facility (rotating machinery platform for environmental risk control) in different running conditions at the LMFA laboratory (Ecole Centrale de Lyon fluid mechanics and acoustics laboratory) concerning synchronous and asynchronous responses (NSV).
It is tested here under vacuum, in rotating conditions in the Phare-1 facility in order to identify structural modal parameters, ie mainly the whole fan blade assembly structural damping. Each blade is equipped with piezoelectric actuators to excite structural modes. Blades’ vibratory responses are measured via embedded strain gauges. The instrumented fan blades are firstly individually tested on a specific test hub mounting. Piezoelectric actuators efficiency is demonstrated by reaching representative amplitudes. Also, individual blades frequencies dispersion is quantified and shows in particular that the added exciters have negligible influence on mistuning and dynamics. The fan response is measured using the same instrumentation as for aerodynamic experiments and at the same rotational speed. Influence of rotating speed and vibration level on modal damping is shown and quantified.
Machine Learning Regression Models for Turbofan Engines: A Comparative Study on Remaining Useful Life Prediction
Authors: Omer Zahi M. , Al Seiari Abdulla , Cen Zhaohui , Bilendo Francisco 
Published: August 2024

Abstract
This study conducts a systematic comparison of data-driven regression models for predicting the Remaining Useful Life (RUL) of turbofan engines in aviation Prognostics Health Management (PHM) field, utilizing the C-MAPSS dataset with advanced feature engineering, the paper evaluates models from simple linear to complex high-dimensional ensemble structures. Notably, the CatBoost model and other ensemble techniques demonstrated superior performance, with CatBoost achieving an R2 value of 99% and other ensembles averaging 92%, significantly outperforming other models with 65% to 77% values. This indicates the robustness of ensemble machine learning methods in precise RUL estimation.
Conventional Design to Design for Additive Manufacturing for Frame 5/1 Stage 1 Nozzle
Authors: Avaiya NIkunj , Cocchi Lorenzo , Soman Abhimanyu , Tripoli Girolamo , Colantoni Simone , Santhana Gopalakrishnan Babu , Del Turco Paolo 
Published: August 2024

Abstract
Baker Hughes has been providing industrial gas turbines globally since the 1950s. Baker Hughes’s Frame 5/1 machine is well-known for its long-running performance in the field. After service life of parts are over, these parts are replaced with new parts. New technologies like Additive Manufacturing (AM) can reduce lead time and provide freedom to design engineers to explore designs that were not possible with conventional manufacturing in the past. This paper discusses the journey from conventional design to design for additive manufacturing for stage 1 nozzle (S1N) of the Frame 5/1 Machine. Direct Metal Laser Melting (DMLM), an AM technology, is considered for manufacturing of this nozzle. Furthermore, the extensive experience accumulated over the years from numerous 5/1 machines operating in the field is leveraged to enhance the optimization of nozzle design. Considering an in-house developed equivalent material in DMLM, the nozzle is redesigned to be compatible with the operating conditions of the current machine and its supporting structure without affecting performance. The structural integrity of the newly developed AM design of the S1N is validated by part life assessment, using the thermo-mechanical finite element Analysis (FEA), and compared against the product requirements. Based on the results of the part life assessment, further improvements were made through multiple design changes and iterations, resulting in the final design. The redesign leads to a significant improvement in the temperature gradient and lowers the metal temperature in S1N in comparison with conventional design. The analysis results demonstrate a significant improvement in overall stresses, plastic strains, creep strains and crack initiation life when compared to the conventional nozzle. Moreover, the predicted amount of oxidation for the new design is much lower than that for the conventional design.
Development of Heat Exchanger Modelling Capability for a Finite Volume Aeroelasticity Solver
Authors: Mitchell Sam , Tartaruga Irene , Stapelfeldt Sina 
Published: August 2024

Abstract
Heat exchangers are frequently used in aero engines and are known to significantly affect the surrounding steady and unsteady flow. In certain applications, they may thereby also influence the aeroelastic stability of upstream or downstream components but there is limited research on this in the public domain. This paper aims to demonstrate the influence of heat exchangers on unsteady flows relevant to aeroelastic problems. This is achieved by developing heat exchanger modelling capability for an in-house finite volume aeroelasticity solver, for which heat exchanger is represented as a porous medium, as this is the established approach in existing aerodynamic studies using commercial CFD software. The governing equations for a Darcy-Forchheimer porous media model suitable for unsteady and compressible flows are presented, which are derived by the application of volume averaging theory to the Navier-Stokes equations. The implementation of this model within the time integration method used for the solver is then described and verified by comparison of results for steady flows against an established commercial CFD solver, where close agreement between both in-house and commercial solvers has been observed. Lastly a preliminary demonstration of the capability to model unsteady heat exchanger flows is presented by application to an aeroacoustic problem, where the interaction of the pressure waves and the heat exchanger is investigated.
The Role of the Working Fluid and Non-Ideal Thermodynamic Effects on Performance of Gas Lubricated Bearings
Authors: de Waart Wessel , Pini Matteo 
Published: August 2024

Abstract
Small-scale turbomachinery operating at high rotational speed is a key technology for increasing the power density of energy and propulsion systems. A notable example is the turbine of an organic Rankine cycle turbogenerator for thermal recuperation from prime engines and industrial processes. Such systems typically operate with organic compounds characterized by complex molecular structures, to allow the design of efficient fluid machinery and flexibility in matching the heat source and sink temperature profiles. Gas lubricated bearings are considered advantageous compared to traditional oil-lubricated rolling element bearings for supporting the turbine rotor, enabling greater machine compactness and reduced complexity, and to avoid contamination of the working fluid. In certain operating conditions, however, the lubricant of the gas bearing is in thermodynamic states near the saturated vapor line or in the vicinity of the fluid critical point whereby non-ideal effects are relevant and may affect bearing performance. This work investigates the physics of thin film flows in gas bearings operating with fluids made by complex molecules. The influence of non-ideal thermodynamic effects on gas bearing performance is discussed by analysis of the fluid bulk modulus. Reduced values of the non-dimensional bulk modulus near the critical point or saturated vapor line decrease bearing performance. The main parameter characterizing the influence of molecular complexity on bearing performance is shown to be the acentric factor. For complex fluids with large acentric factors, the impact of non-ideal thermodynamic effects on non-dimensional bearing load capacity and rotor-dynamic characteristics is less pronounced.
Experimental and Numerical Investigations of Flow Patterns at Low Volume Flow Rate Conditions in Low Pressure Steam Turbine
Authors: Tabata Soichiro , Segawa Kiyoshi , Takahashi Tadashi , Aoyagi Jin 
Published: August 2024

Abstract
This study investigates the flow patterns at the last stage exit of a low-pressure steam turbine under low volume flow conditions. The 0.33 scale 5-stage model steam turbine was used to measure turbine performance and flow patterns at the last stage exit. Numerical simulations were performed to verify the accuracy of flow pattern prediction under low volumetric flow conditions by using a mixing plane (MP), a multiple mixing plane (MMP), and a frozen rotor (Frozen). Equilibrium and nonequilibrium condensation analyses were also performed to investigate the effects of subcooling under low volume flow conditions. Numerical simulations showed good agreement with measured turbine efficiencies over a wide range of volume flow rates. A comparison of MP, MMP, and Frozen results under low volumetric flow conditions showed that the results were generally similar, but Frozen was the closest to the experimental results. Comparison of measured and equilibrium condensation analysis results for the flow pattern at the last stage exit under the low, middle, and high volumetric flow rates showed that the numerical results basically represent the experimental results well. However, the equilibrium condensation analysis results for the absolute swirl angle at middle and high volumetric flow conditions showed a discrepancy with the experimental results. The non-equilibrium condensation analysis confirmed that secondary nucleation occurred in the last stage rotating blade under middle and high volumetric flow conditions. On the other hand, no secondary nucleation was observed in the last stage rotating blade in the non-equilibrium condensation analysis for the low volume flow condition. The results show good agreement between the numerical predictions and the experimental data, highlighting the importance of considering non-equilibrium condensation effects under design conditions, but also emphasizing that such effects do not need to be considered under low volume flow conditions because of the presence of backflow at the last stage outlet.
High-Fidelity Predictions of Aerodynamic Losses Through a Supersonic Stator Vane
Authors: Matar Camille , Gloerfelt Xavier , Cinnella Paola 
Published: August 2024

Abstract
This study aims at providing evidence of the importance of using high-fidelity methods for accurate loss estimation during initial ORC turbine design. The case of a supersonic stator vane in both linear and annular cascades is used to exemplify the divergences in loss between flows where crucial features including the boundary layers, the wake and secondary flow are disparately modeled. Specifically, well known strategies, namely Reynolds-Averaged Navier-Stokes (RANS) modeling, Delayed Detached Eddy Simulation (DDES) and Large Eddy Simulation (LES), are used. In the linear cascade, the misprediction of the boundary layer properties leads to large deviations in trailing edge loss attributed to momentum deficit. On the other hand, resolving the unsteady wake dynamics provides substantial improvement of the base pressure estimation, which is the strongest contributor to overall trailing edge loss. In the annular cascade, fair agreement is found with experimental pressure measurements and numerical data from the literature. Stagnation pressure deficit through the wake is well reproduced by the DDES, while the RANS solution features a wider and slightly displaced wake. Overall, the present study shows that, although the computational cost varies over orders of magnitude, accurately resolving the complex flow phenomena that exist in a turbine vane is a crucial step for improved ORC turbine design.
Analysis of Liquid Fuel Effect on Swirl-Assisted Jet-Stabilized Combustor Performance
Authors: Izadi Saeed , Seliger-Ost Hannah , Zanger Jan , Kutne Peter , Aigner Manfred 
Published: August 2024

Abstract
Growing interest in reducing pollutant emissions from gas turbines is driving efforts to develop combustor system solutions with low NOx, CO and UHC emissions while maintaining a wide range of performance and fuel flexibility. The paper describes an investigation of the spray produced by flash boiling mechanism (superheated injection) and mechanical liquid bulk breakup (pressure-swirl atomization) in a lean premixed swirl-assisted jet-stabilized combustion system. Fuel vaporization prior to combustor inlet is greatly enhanced by the combustor design and elevated liquid fuel temperature. A comprehensive analysis of combustion behavior for a range of fuels in both liquid and superheated regimes has been performed. The fuel atomization is based on the mechanical and thermal breakup of the liquid fuel in a temperature range of 150–300°C. Variable thermophysical properties of four different liquid fuels from various origins are investigated under atmospheric conditions. OH* chemiluminescence and Mie scattering have been used as optical and laser diagnostic methods. These measurement techniques were used to analyze the combustion behavior and spray breakup mechanism. A mixing condensation particle counter (MCPC) was used to determine the particulate emissions of the various liquid fuels and spray generation techniques. Measurement of exhaust gas emission levels of NOx, CO and UHC are conducted simultaneously for each operating point. The underlying factor effects are presented and discussed. The results indicate that while NOx and CO emissions are not majorly affected by the fuel atomization technique, the thermophysical properties of the fuel, such as the saturation temperature, play an important role in the fuel atomization process and to a minor degree on the emitted NOx and CO emissions. Furthermore, it is shown that, except for differences in spray penetration length and evaporation quality, the combustion performance was similar in terms of flame operating range for all tested liquid fuels. The effect of different fuel atomization techniques on particulate emissions was minimal. However, due to their origins, the different fuels had large variations in the particulate matter measurements.
Assessment of the Wilshire-Cano-Stewart (WCS) Model Using Strain Energy Density Dissipation (SEDD)
Authors: Pellicotte Jacob , Hossain Md Abir , Cano Jaime , Stewart Calvin M. 
Published: August 2024

Abstract
In this study, Strain Energy Density Dissipation (SEDD) is employed as a creep damage parameter to calibrate the Wilshire-Cano-Stewart (WCS) Model. The WCS model is an adaptation of the Wilshire equations combined with continuum damage mechanics to enable predictions of creep deformation and damage. In WCS, the analytical calibration methods for the Wilshire equations remain unchanged and the additional damage parameters are found using numerical optimization. Though the WCS model can accurately predict progressive creep deformation, the damage remains phenomenological. Herein, damage is represented as SEDD. In SEDD, it is assumed that a material system has a finite amount of energy it can dissipate until reaching failure. Assuming that SEDD is caused by the accumulation of microstructural defects, the damage process is represented as a scalar value from zero (undamaged) to unity (rupture). By combining the WCS model with SEDD, damage evolution is pinned physically and can be measured experimentally. Stress-rupture, minimum-creep-strain-rate, and creep deformation data is gathered for alloy P91 at 600 °C and stresses from 100 to 200 MPa. The Wilshire constants are analytically determined and compared with the literature. The damage-trajectory constant is calibrated using SEDD measurements. The new calibration accurately predicts the material response across the range of stresses and temperatures. A comparison between numerical optimization and measured damage-trajectory constants is performed. Parametric simulations verify the interpolation and extrapolation capabilities of this new approach.
Generic Framework for an Accurate, and Efficient Flutter Analysis
Authors: Zori Laith , Patel Purvic , Patil Sunil , Orlando Stephen , Campregher Rubens 
Published: August 2024

Abstract
Accurate and efficient prediction of blade aerodynamic damping is critical for the design and durability of turbomachines such as gas and steam turbines. Several empirical and linearized methods have been developed and used with varied degrees of success over the past decade, especially for bladed components. This paper presents a generic framework to carry out flutter analysis which is equally applicable for bladed turbomachinery components as well as other complex components in the engines such as seals, and valves.
A streamlined workflow to carry modal analysis and then perform efficient CFD analysis using one or multiple modes to obtain accurate aerodamping is outlined. A recent implementation of phase-lag approach with traveling wave method in Ansys Fluent is described. This approach enables calculation of flutter for any nodal diameter with just a single sector of the turbomachinery. Furthermore, the implementation of Aerodynamic Influence Coefficient method for a very fast turnaround time to get aerodamping for a range of nodal diameters is discussed.
The framework presented is validated and presented for two cases. The first testcase is Rotor 1 from the 4.5 stage high-speed Hannover compressor, which represents standard bladed turbomachinery. A range of nodal diameters are investigated using both the travelling wave method and influence coefficient method. The accuracy of phase lag approach is compared with the reference full-wheel solution. The speedup provided by the phase lag approach and influence coefficient method is discussed in detail. The second testcase is a generic gas turbine seal representing a complex feature in modern turbomachinery. It is shown that the framework presented and validated for bladed geometry can be used without any further modifications for such a complex case.
Using Pseudotime Marching for the Solution of Harmonic Balance Problems
Authors: Frey Christian , Backhaus Jan , Ashcroft Graham , Geiser Georg , Winhart Benjamin , Stüer Heinrich 
Published: August 2024

Abstract
The aim of this paper is to study approaches to implement implicit pseudotime marching for the harmonic balance system in the frequency domain. We first give a motivation for using pseudotime marching as a solution technique. It turns out that, when the discretization errors of the pseudospectral time derivative and the pseudotime derivative are neglected, the harmonic balance solution converges to a stable periodic flow, provided that the initial solution is sufficiently close to a stable periodic solution. This motivates the choice of a robust pseudotime marching approach, e.g., an implicit solver based on backward Euler integration. This approach requires the Jacobian of the harmonic balance residual. As for the steady problem, the Jacobian can be approximated without changing the final solution as long as the solver converges. Therefore, a central question is which simplifications are appropriate in terms of the overall efficiency and robustness of the solver.
As has been shown in the literature, the spectral timederivative operator should be taken into account in the implicit system. On the other hand, the linearization of the flow residual can be simplified to a certain extent, especially if the system is solved in the frequency domain. In this paper, we show that, up to terms which scale with the amplitude of the disturbances, the linear system matrix is the sum of a scalar diagonal and a block diagonal matrix with identical blocks for each harmonic. The deviation from this structure is due to to the nonlinearity of the unsteady flow problem. We show that when the unsteadiness is small, the nonlinear coupling terms can be neglected in the implicit solver and the resulting special matrix structure can be exploited to massively speed up the solver. In contrast, when a strong disturbance is simulated, this simplification can lead to significant losses in robustness. To illustrate our findings we apply the implemented methods to predict the flow response to a disturbance prescribed at the inlet of a transonic compressor. When the disturbance amplitude is increased, a strong oscillation is induced, and the harmonic balance solver converges only when the nonlinear coupling between the harmonics is taken into account.
Combining Machine Learning, Embedded Sensor Networks and Additive Burner Design for Combustor Structural Health Monitoring
Authors: Giuliani Fabrice , Paulitsch Nina , Hofer Andrea , Petrovic-Filipovic Vojislav , Maier Benjamin , Bailer Werner , Winter Martin , Unterberger Roland , Schricker Alexander 
Published: August 2024

Abstract
The crystAIr project is a method of sensitising a burner for flame monitoring based on a discrete number of dynamic pressure sensors and a machine learning approach. The context is the development of better aircraft engines, and in particular the development of solutions for hydrogen-fuelled gas turbines. The combination of sensors and appropriate signal processing is designed to mimic a ‘feel’ for the state of the flame. The idea is to monitor the correct operation of the gas turbine in real-time and to anticipate impending problems such as flame blowout, combustion instability or flashback. Compared to conventional flame monitoring based on signal sampling, thresholding, bandpass analysis and time-lag measurement, this method should be less computationally intensive, more sensitive and more robust to artefacts. Not only should it be more responsive, but it should also anticipate problems based on a lessons-learned approach and outperform the conventional precursors. An unassisted machine learning method is used to achieve this. Acustom-built AM burner designed for this experiment provides multiple instrumentation options. A powerful data acquisition system is set up to collect data on multiple channels, over a long time duration and at high speed to collect the learning signal chunks. The focus is on the detection of flames and, more specifically, the moment of their ignition and extinction, the operating conditions that are prone to flashback and the stability of the combustion. Additional measurement techniques are used to refine the learning method. The paper covers all these points and presents the first results.