bluuebunny/crossref_metadata_2025_split huggingface dataset:
Analysis on Nonlinear Vibrations of Mistuned Blades With Frictional Under-Platform Dampers Considering Asynchronous Excitation Force
Authors: Umehara Ryuichi , Akaki Tomohiro , Onozato Naoki , Kitada Hiroki 
Published: September 2023

Abstract
Turbine blades are used under increasingly severe conditions to increase the thermal efficiency of the gas turbines in operation. Friction dampers reduce vibration responses of the blades and improve the power plant reliability. One of the representative friction dampers is the under-platform damper designed to generate friction between two blade platforms and a damper pin. The under-platform damper has been widely adopted in gas turbines. It is important to predict the characteristics of vibration for turbine blades with the dampers analytically on design phase. Thus, a lot of analytical methods have been intensively proposed. However, it is very difficult to obtain analytical results showing high consistency with actual phenomena, which depend on mistuned blades with nonlinear friction dampers and on complicated excitation force included asynchronous random force. The authors indicated necessity of consideration of the two effects, i.e., synchronous harmonic excitation force and asynchronous random excitation force, in the past paper. Although some papers are specific to frictional vibration analysis on mistuned blades, there are no papers considering the effect of asynchronous excitation force. This paper presents the analytical method dealing with nonlinear vibrations of mistuned blades with under-platform dampers on actual condition considering asynchronous excitation force. The analytical results show good agreement with amplitude of vibration and variation of frequency response curves under the mistuned condition. It is suggested that analytical models should take into consideration of variation in the blade properties and asynchronous excitation force to obtain reproducible analytical results on the actual variation of each blade response.
Roughness Investigations on In-Service High-Pressure Compressor Blades – Part II: Roughness Parameterization and CFD-Based Modelling of its Impact on Turbulent Flows
Authors: Vasilopoulos Ilias , Adami Paolo , Voigt Matthias , Meyer Marcus , Mailach Ronald 
Published: September 2023

Abstract
The two-part publication deals with roughness investigations on in-service high-pressure compressor (HPC) blades, both in terms of measurements and simulations. In this paper (Part II), first, stripe measurements of surface roughness coming from the suction side of the blades are conducted, using a highly accurate Alicona measuring device (see Part I for details of the measurement approach). Then, these roughness distributions are used to construct the walls of zero-pressure-gradient, fully turbulent channel flow simulations. Body-fitted unstructured grids of up to 80M nodes are generated, on which wall-resolved LES as well as RANS simulations with the k-ω SST turbulence model are performed. The CFD setup is first validated on a smooth channel reference case against LES and DNS data from the relevant literature. In addition, the impact of Reynolds number on several rough channel flow simulations is explored, using two different setups at Reτ = 540 and Reτ = 880. Finally, after an identification of the most important roughness parameters (given the relatively limited database at hand), a new roughness function model is proposed, which would allow the prediction of the flow over a rough surface without the need of geometrically resolving the roughness scales.
Spatial Temperature and Water Molar Concentration Measurements Using Thermal and Electrostrictive LIGS During Operation of a Swirl Burner at Pressure
Authors: Weller Lee , Shah Priyav , Giles Anthony , De Domenico Francesca , Morris Steve , Williams Benjamin A. O. , Hochgreb Simone 
Published: September 2023

Abstract
Laser-Induced Grating Spectroscopy (LIGS) was applied in a high-pressure combustion facility. Instantaneous (sub-μs), spatially resolved (within 5 mm) measurements of temperature and molar fractions of water were obtained using thermal and electrostrictive LIGS signals. Temperatures up to 1800 K and water molar fractions between 0.01 and 0.12 were measured. A new analytic approach was developed to extract temperature from the frequencies of the measured signal within the flame brush region, where mixtures contain both burnt and unburnt gases. Mean product temperatures are shown to be 8% lower than the adiabatic temperatures for the nominal equivalence ratio, and 14% higher than measurements made with a thermocouple, uncorrected for radiation losses. This work represents the first application of LIGS to a high-pressure, turbulent swirling flame, opening up the potential for future uses in other real world applications. Challenges associated with the deployment of the technique are described, as are potential measures to overcome these difficulties.
Concurrent Design and Operation Optimization of a Multi-Generation Energy System by Using a SMO-MILP Hybrid Algorithm
Authors: Castorino Giulia Anna Maria , Losi Enzo , Manservigi Lucrezia , Pinelli Michele , Spina Pier Ruggero , Venturini Mauro 
Published: September 2023

Abstract
Multi-generation energy systems, which include both fossil fuel technologies and renewable energy systems, are recognized as key players towards more sustainable energy production. To this aim, this paper proposes a methodology for the concurrent design and operation optimization of a multi-generation energy system by considering both life cycle energy consumption and economic aspects. The multi-generation energy system considered in this paper comprises renewable energy systems (photovoltaic panels, solar thermal collectors), heat pumps, fossil fuel energy systems (combined heat and power systems, gas boilers, absorption and compression chillers), and thermal storage systems.
The design optimization problem is solved by means of a surrogate modeling approach, while the operation optimization problem is addressed by means of mixed-integer linear programming and by considering the minimization of fossil cumulative energy demand or total cost. A clustering approach is employed to simulate the yearly electrical, thermal and cooling energy demand by using selected representative days. The variability of natural gas and electricity price in year 2019 and 2022 is also investigated.
The validity of the suggested approach is demonstrated by using the Campus of the University of Parma (Italy) as the case study. The proposed methodology provides an effective and flexible framework for the optimal design and operation of multi-generation energy systems, with a reduced computational time thanks to the clustering approach which allows the identification of a low number of representative days that simulate actual energy demand. The energy saving that can be achieved by means of the methodology developed in this paper can be up to 53%.
Predicting Transitional and Turbulent Flow Around a Turbine Blade With a Physics-Informed Neural Network
Authors: Hanrahan Sean K. , Kozul Melissa , Sandberg Richard D. 
Published: September 2023

Abstract
Despite the demonstrated usefulness of RANS for many industrially-relevant problems, it can be challenging to accurately simulate certain flow features with the method. Due to the Reynolds-averaging process, the Reynolds-averaged Navier-Stokes equations require a turbulence model to close the equations, and the simple physical arguments and approximations used in many turbulence models can cause erroneous results when applied to flows featuring separation or strong pressure gradients. Physics-informed neural networks (PINNs) offer a way to model aerodynamic problems without explicitly requiring a closure. The network can use sparse training data and the unclosed RANS equations to reconstruct the flow without a turbulence model. In this work, PINNs are applied to two problems of relevance in the tubomachinery community, a variable area channel known as the periodic hills, and the T106C low-pressure turbine blade with two different levels of inlet turbulent intensity. These turbulent flows feature shear layers, separation bubbles, as well as favourable and adverse-pressure-gradients. We demonstrate that PINNs are capable of modelling wall-bounded quantities such as Cf and Cp in such complex flows, capturing sensitive features such as the change in separation length when the turbulent inlet conditions are altered. Excellent predictions of wake mixing are also achieved with sparse training data required. Based on these results, future potential work should focus on reconstructing the wake loss region of a linear cascade with sparse experimental data.
Wall Resolved Large-Eddy Simulations of High-Speed Low-Pressure Turbine Cascades
Authors: Tene Hedje Patrick , Bechane Yacine , Lavagnoli Sergio , Bricteux Laurent 
Published: September 2023

Abstract
The current energy challenges in the field of aircraft propulsion demands a better understanding of turbine flows. The complexity of the flows and the geometrical configurations at play limit the feasibility of experimental investigations in this field. Building predictive numerical methods to capture accurately the flow physics is thus important, even if it still constitutes a challenge.
This paper focuses on numerical simulations of high-speed low-pressure turbine blades (HS-LPT), a major component in the framework of high-efficiency geared turbofan engine designs. In this framework, Wall Resolved Large-Eddy Simulations (WRLES) of flows in HS-LPT transonic cascades are performed, using a high order Finite Volume Method (FVM). The Explicit Compressible Solver (ECS) of the massively parallel code “YALES2” is used here. The study focuses on two different cases of low-pressure turbine cascades. First, the well-known T106-C cascade benchmark is studied in order to assess the YALES2 solver for compressible turbomachinery flows. The predictions matches fairly well with those of other numerical codes in the literature and experiments. The second test case investigated is the “SPLEEN” cascade, a next-generation high-speed low-pressure turbine cascade developed by Safran aircraft engines and the von Karman institute for fluid dynamics as a part of a large scale collaborative project. The aim here is to assess the solver for transonic flows, in terms of prediction of the SS separation bubble, the separation-induced laminar-turbulent transition and the wake deficit, using a very detailed experimental database. The results are thus compared with high-fidelity experimental data. This paper shows that the method presented here is able to provide predictive results that can be further used to help in the design LPT blades.
The Effect of Methane-Ammonia and Methane-Hydrogen Blends on Ignition and Light-Around in an Annular Combustor
Authors: Kwah Yi Hao , Wiseman Samuel , Dawson James R. 
Published: September 2023

Abstract
The use of hydrogen and ammonia in gas turbines, either alone or blended with natural gas, poses various technical challenges for combustion systems, including ignition. Depending on the fuel composition, the laminar flame speed and the ratio of unburned to burned gas density (dilatation ratio) of hydrogen and ammonia flames can be well outside the range seen in natural gas flames. Previous studies in annular combustion chambers have provided evidence of the importance of these properties in determining the ignition dynamics including light around times. So far, these studies have mostly considered hydrocarbon fuels, have been limited to only a few runs, and have not yet systematically investigated variations in the dilatation ratio and the flame speed but rather have considered them as a lumped parameter. To investigate these effects in more detail, experiments characterizing the light around times were carried out on an atmospheric annular combustor in which the dilatation ratio and the laminar flame speed was independently varied. This was achieved by varying the equivalence ratio and employing a variety of different hydrocarbon fuels (ethylene, propane, methane) and fuel blends of methane-ammonia and methane-hydrogen. Light around times were evaluated from global chemiluminescence measurements obtained using an azimuthal array of photomultipliers placed round the combustor chamber as well as high speed imaging. To improve statistical certainty, more than 3000 ignition and light-around times were measured with 30 repetitions obtained for each operating condition. To provide some insight into the light around dynamics in specific cases, 900 of the 3000 sets included high-speed OH* chemiluminescence images. Light around times for premixed pure hydrocarbon flames showed a similar dependence on SL as reported in previous studies. For the range of ammonia fuel blends investigated, an increase in laminar flame speed leads to a predictable increase in the flame propagation speed, as in the case of hydrocarbon fuel. Furthermore, collapse of this dependence for all blends could be achieved when corrected for an effective Lewis number, noting that all Lewis numbers for these blends were above unity. However, for hydrogen fuel blends, a decrease in dilatation ratio was found to decrease the light-around time counter to existing experimental results on the ignition of hydrocarbon fuels for which we currently do not have an explanation.
Towards the Multifidelity Optimization of H2-Air Injector for Aircraft Propulsion
Authors: Farjon Philippe , Bertier Nicolas , Dubreuil Sylvain , Morio Jérôme 
Published: September 2023

Abstract
The use of hydrogen as a fuel is one of the most promising way to reduce the climate impact of civil aviation but it requires the development of wholly new injectors in the engine’s combustion chamber. Thanks to the increase in available computing power, new methodologies such as surrogate-based optimization, relying heavily on Computational Fluid Dynamics (CFD) along with automated optimization procedures, can be used to design these injectors. One important point is that 3D geometrical models and high-fidelity numerical approaches are often mandatory to capture key features of the multi-species, turbulent reactive flow through the combustion chamber. However, an optimization process only based on these approaches would be much too expensive. The multifidelity surrogate-based approach is a promising alternative and consists in using CFD simulations with various fidelities. However, its effectiveness depends on the correlation between the different levels of fidelity. The final, long run, goal of this work is the multifidelity optimization of H2-air injector for aircraft. In this paper, we focus on the very first steps of this work with the methodology presentation and a comparison of low (2D RANS) and intermediate (3D RANS) fidelities, which shows a fairly well agreement. Then, preliminary results of comparisons between intermediate and high (LES) fidelities, which highlight the need to improve modeling of RANS simulations, are discussed.
Computation of Isolated Periodic Solutions for Forced Response Blade-Tip/Casing Contact Problems
Authors: Vadcard Thibaut , Thouverez Fabrice , Batailly Alain 
Published: September 2023

Abstract
This article introduces a numerical procedure dedicated to the identification of isolated branches of solutions for nonlinear mechanical systems. It is here applied to a fan blade subject to rubbing interactions and harmonic forcing. Both contact, which is initiated by means of the harmonic forcing, and dry friction are accounted for. The presented procedure relies on the computation of the system’s nonlinear normal modes and their analysis through the application of an energy principle derived from the Melnikov function. The dynamic Lagrangian frequency-time strategy associated with the harmonic balance method (DLFT-HBM) is used to predict the blade’s dynamics response as well as to compute the autonomous nonlinear normal modes. The open industrial fan blade NASA rotor 67 is employed in order to avoid confidentiality issues and to promote the reproducibility of the presented results. Previous publications have underlined the complexity of NASA rotor 67’s dynamics response as it undergoes structural contacts, thus making it an ideal benchmark blade when searching for isolated solutions. The application of the presented procedure considering a varying amplitude of the harmonic forcing allows to predict isolated branches of solutions featuring nonlinear resonances. With the use of the Melnikov energy principle, nonlinear modal interactions are shown to be responsible for the separation of branches of solutions from the main response curve. In the end, the application of the presented procedure on an industrial blade model with contact interactions demonstrates it is both industry-ready and applicable to highly nonlinear mechanical systems.
Hydrogen Co-Firing Demonstration at New York Power Authority Brentwood Site: GE LM6000 Gas Turbine
Authors: Steele Robert C. , Martz Thomas D. , Ettlinger Alan , Zandes Timothy , Alexander Michael J. , Hockman Brian K. , Goldmeer Jeffrey 
Published: September 2023

Abstract
The New York Power Authority (NYPA), EPRI, and General Electric (GE) developed and executed a pilot project focused on hydrogen-fueled power generation. As part of the Low-Carbon Resources Initiative (LCRI), the companies jointly conducted a hydrogen blending project at NYPA’s Brentwood Power Station. This collaborative effort demonstrated the burning of a hydrogen-natural gas blend on an LM6000 gas turbine (GT) to identify the resulting impact on combustion emissions (CO2, NOx, CO) and GT operation. The GT was operated on hydrogen blends ranging from 5 to 44% by volume. The successful test represents the first utility-scale hydrogen blending project in the state of New York, which is mandating a zero-emission electricity sector by 2040 and calling for an orderly and just transition to clean energy for a economy-wide carbon neutrality through the Climate Leadership and Community Protection Act.
Exploring the Effects of Pin-Fins in a Gas Turbine Blade Internal Cooling Channel
Authors: Nourin Farah Nazifa , Amano Ryoichi S. 
Published: September 2023

Abstract
The narrow cooling passage of the internal section of the turbine blades is one of the complicated zones of the gas turbine system. It confronts a high temperature. Pin-fins are an excellent structure to insert in this section to ensure effective cooling. It accomplishes a higher heat transfer coefficient. Pin-fins are also implemented as a mechanical structure to bridge the thin metallic pressure surface and suction surface. However, the pressure drop is significantly higher in the case of pin-fin cooling, which can lower the thermal performance of the cooling channel. The optimization of pin-fin design is important to find the optimal pressure drop. The present study considers two different pin-fin designs, i.e., partial spherical and dome with different arrays of pin-fins. The experimental and computational investigation was conducted with rotation numbers ranging from Ro = 0 to Ro = 0.13. The experimental study was conducted with Reynolds (Re) numbers ranging from 9,000 to 50,000. A computational study was conducted with the Large Eddy Simulation (LES) technique. The final judgment was completed based on the cooling channel’s heat transfer coefficient, friction factor, and thermal performance. The cooling channel with dome-shaped pin-fins with an array of 14 × 2 pin-fins showed a better thermal performance than other cooling channels.
Development of a Hydrogen Micro Gas Turbine Combustor: Atmospheric Pressure Testing
Authors: Tanneberger Tom , Mundstock Johannes , Rex Christoph , Rösch Sebastian , Paschereit Christian Oliver 
Published: September 2023

Abstract
The vision of a carbon-neutral world, implies the shift from fossil to clean fuels for combustion-driven processes and machines like gas turbines. Green hydrogen is a promising alternative to substitute natural gas and other fossil fuels.
In the H2mGT project, funded by the German BMWK, a micro gas turbine (mGT) burner with 100% hydrogen firing is developed and validated. The project is a collaboration between TUB and the manufacturer Euro-K GmbH. The project consists of three phases: 1. Atmospheric pressure tests with a fused silica combustion chamber; 2. Atmospheric pressure tests with counterflow-cooled steel combustion chamber and secondary air injection; 3. Validation of the burner in the micro gas turbine at elevated pressure levels. This paper will present the results of Phase 1.
The hydrogen burner is based on a swirl-stabilized burner of TUB and was scaled to match the requirements of the mGT with its 130 kW thermal power. The burner design features multiple geometrical parameters to enable the optimization of the flame towards low NOx emissions. Therefore, a variable swirl intensity, additional axial momentum of air in the mixing tube, a movable center-body and different fuel injection locations are implemented. Phase 1 investigates the parameter space in terms of flame stability, operational range and parameter impact on flame shape and emissions. Therefore, temperature, pressure, and emission measurements as well as OH* imaging are carried out. It is found that the flame can be operated over a large range of equivalence ratios and preheating temperatures up to 500 °C for many parameter settings. However, at some geometries flashback into the mixing tube is triggered. As expected, the NOx emissions are mainly influenced by the equivalence ratio, the fuel distribution, and the swirl intensity. Single digit emissions are reached up to an equivalence ratio of 0.4 at atmospheric pressure conditions. Furthermore, at low air mass flow, the burner can be operated at 100 % natural gas or 100 % hydrogen without any geometry changes. The fuel switch, thereby, does not change the NOx emissions significantly if reasonable normalization is used.