bluuebunny/crossref_metadata_2025_split huggingface dataset:
Innovative Air Bypass System for Low-Emission Multi Can Combustors
Authors: Ćosić Bernhard , Wassmer Dominik , Reiß Frank , Kluß David , Pähr Judith , Reumschüssel Johann Moritz , Beuth Jan Paul , Szeponik Martin , Reichel Thoralf , Paschereit Christian Oliver 
Published: September 2023

Abstract
Gas turbines that are used as compressor drives are often operated in the part load regime because compressor stations are usually designed for operation with full power at extreme weather conditions. Consequently, these gas turbines must comply with strict emission regulations at unfavorably low turbine inlet temperatures. To extend the low emissions operation range of the premixed combustion systems, many gas turbines bypass a part of the compressed air upstream of the combustor and either blow it off into the exhaust stack or reinject it into the secondary combustion zone. The first approach is the more common one but has the disadvantage of increasing the gas turbine fuel consumption and thus the CO2 emissions. The second approach avoids this disadvantage but is very challenging in terms of actual mechanical integration into the gas turbine. This paper presents a new approach that overcomes shortcomings by injecting the compressed air in the burner head in the vicinity of the primary combustion zone. This is particularly attractive for multi can combustors like these employed for the MAN industrial gas turbine family.
Atmospheric combustion tests are conducted for two different air injection designs. The first design features lower air injection velocity and the second features higher injection velocities. Both injection strategies are tested with the industrial MGT gas turbine can combustor. It features 4 MW of thermal power at full pressure and full load conditions. It is an ultra-low emission premixed swirl combustor with a radial swirler design. The full size burner is tested at atmospheric conditions in a burner test rig with a quartz flame tube and natural gas as fuel. The performance of the air bypass system is assessed by means of CO and NOx emission measurements for different air bypass ratios and is compared with high-pressure measurements without an air bypass system. Additionally, OH* chemiluminescence camera pictures are presented and compared to CFD calculations. It is found that the air injection in the annular vicinity of the swirl flame does not cause increased CO emissions by quenching or other effects. For the investigated setup, it is more favorable to inject the air at low velocities because this strategy causes less interaction between bypass air and premixed flame.
Numerical Analysis of High Frequency Transverse Instabilities in a Can-Type Combustor
Authors: Jella Sandeep , Füri Marc , Katsapis Vasilis 
Published: September 2023

Abstract
Dry Low Emissions (DLE) systems are well-known to be susceptible to thermoacoustic instabilities. In particular, transverse, spinning modes of high frequency can lead to severe hardware damage in a matter of seconds. The thermoacoustic response of an engine is specific to the combustor geometry, operating conditions and difficult to reproduce at the lab-scale. In this work, details of high frequency dynamics observed during the early development phase of a new DLE system are provided, where a multi-peaked spectrum was noticed during rig-testing. Beginning with an analysis of the measured pressure spectra and the natural resonance frequencies of three different concepts, an analytical model of the clockwise and anti-clockwise transverse waves was fitted to the experimental data using a non-linear curve fitting approach to produce a simple yet useful understanding of the phenomena. A flamelet-based Large Eddy Simulation (LES) of the entire system was used to complement this analysis and confirm the mode shapes using dynamic mode decomposition (DMD). Both approaches independently identified a spinning second order mode as the dominant one in the high frequency regime. The LES indicated that precessing vortex core dynamics tend to impose a deformation (in the circumferential direction) on the outer shear layer vorticity magnitudes. Flame anchoring in this shear layer is suggested as a possible cause for the onset of instability. With regard to modeling sensitivities, it is shown that sub-grid scale combustion modeling has a strong impact on predicted amplitudes. Ultimately, a thickened-flame model with a modified efficiency function provided consistent results.
Collision Mechanism and Dynamic Response of Rotor System With Pedestal Looseness
Authors: Dai Qiyao , Sun Bo , Chen Xueqi , Ma Yanhong 
Published: September 2023

Abstract
In the structural design of aeroengine multi fulcrum flexible rotor, due to the limitation of assembly conditions and working load environment, there is a certain fit clearance between the bearing outer ring and the bearing pedestal, which is called pedestal looseness. When the response amplitude is high, the outer ring and pedestal collide, which affects the dynamic characteristics of the rotor system. Previous research often characterize the collision caused by pedestal looseness on the rotor as a nonlinear stiffness term in the rotor dynamics model, which can not directly reflect the real collision mechanism of the rotor. In this paper, the mechanical model of flexible rotor system with pedestal looseness was established. The motion variation process of rotor when collision occurred and subjected to radial impact was analyzed, which is characterized as the collision force of rotor, and the dynamic response is obtained. The results showed that when the response amplitude is large, rotor and bearing pedestal collided periodically, and various combination frequencies of rotation frequency and collision characteristic frequencies appeared in dynamic response; the combination frequencies may be equal to the modal frequency of the rotor system at the non critical speed point, so that the rotor may still have a large response amplitude when the speed is far from the critical speed.
Experimental Analysis of the Hydrogen Capability of a Fuel Flexible Jet Stabilized Syngas Micro Gas Turbine Combustor Under Atmospheric Conditions
Authors: Hohloch Martina , Lingstädt Timo , Kutne Peter 
Published: September 2023

Abstract
In this study the hydrogen capability of a jet-stabilized combustion system, initially designed/or syntheses-gas from biomass and natural gas mixtures, was investigated at atmospheric conditions. Therefore it was operated with mixtures of natural gas with hydrogen, from pure natural gas to pure hydrogen. In addition, different operational concepts for the pilot stage and their influence on the stability of the combustion and emissions were tested. The investigations were performed in an atmospheric test rig. The test rig offers optical access to the combustion zone by a cylindric quartz glass tube. It is equipped with thermocouples, pressure probes and mass flow meters. The incoming air was preheated up to 600 °C. During the investigations the parameters burner air number and thermal power were varied. The analysis of the flame was done using OH*-chemiluminescence measurement. The emissions were quantified using gas analyzer systems to detect CO, CO2, NOx, O2 and UHC concentration. The position of the flame and the emissions are discussed. The results show that the combustor is able to deal with all tested mixtures of natural gas and hydrogen up to 100% of hydrogen. The results of the measurement campaign were used to validate CFD simulations. In this publication both experimental results and corresponding simulations are shown and assessed.
Transient Tip Clearance Prediction Model Considering Transient Radial Temperature Distribution of Discs in a Gas Turbine Engine
Authors: Wei Jie , Yang Heli , Zheng Pengbo , Wang Baotong , Zheng Xinqian 
Published: September 2023

Abstract
The tip clearance of turbomachinery components, such as compressor and turbine, significantly impacts gas turbine engine performance, including the thrust and fuel consumption. Therefore, an appropriate prediction of turbomachinery tip clearance and active clearance control is indispensable in improving engine performance. The traditional 1D transient tip clearance prediction model does not consider the radial temperature distribution of the disk (also called disc). However, as the engine performance keeps improving, the disk’s radial temperature gradient also increases. In order to maintain the prediction accuracy within an acceptable range, a generic transient tip clearance prediction model is developed in this paper. Based on the special treatment of the complex axial and radial convective heat transfer boundary regions of the disk, a 2D transient heat transfer model is established, and the radial temperature of the disk is predicted. At the same time, to further improve the prediction accuracy, the thermal expansion interaction between the two different layers of the shroud is studied. In addition, the centrifugal deformation of the blade and disk with variable thickness characteristics are considered in the new transient model. Compared with the traditional 1D transient prediction model, the model developed in this paper further improves the predicting accuracy of the transient tip clearance, which is verified by the high-fidelity fluid-solid-thermal coupling method. The prediction model provides a useful tool for evaluating transient tip clearance. It may also benefit the future design strategy of active clearance control.
Wind Tunnel and OpenFOAM Flow Analysis of a High Solidity Vertical-Axis Wind Turbine
Authors: Yosry Ahmed G. , Álvarez Álvarez Eduardo , Espina Valdés Rodolfo , Fernández Francos Joaquín , Blanco Marigorta Eduardo 
Published: September 2023

Abstract
In the present study, a combination of experimental and numerical investigation has been carried out to ascertain the aerodynamics and the performance characteristics of a small-scale vertical axis turbine model, with a high solidity value. Experimentally, the turbine model has been designed and fabricated using Fused Deposition Modeling (FDM). Tests have been performed in an open-circuit wind tunnel for a velocity range from 7.0 m/s to 10.0 m/s. The non-dimensional tip speed ratio and power coefficient characteristic curves show that the turbine rotor works smoothly under open-field conditions. Computationally, three-dimensional unsteady simulations have been developed using the open-source software OpenFOAM to obtain a comprehensive insight into the aerodynamics and the flow field around the high solidity rotor. The pimpleFOAM solver has been selected for the current code. A good match between the experimental and the OpenFOAM code results has been found, validating the description of the flow physics around the turbine rotor. Also, the vortex street generated by the turbine blades and the ending plates has been visualized.
Effects of Riblet Dimensions on the Transitional Boundary Layers Over High-Lift Turbine Blades
Authors: Ananth S. M. , Nardini Massimiliano , Vaid Aditya , Kozul Melissa , Vadlamani Nagabhushana Rao , Sandberg Richard D. 
Published: September 2023

Abstract
Substantial research exists in the literature on reducing the profile loss of transitional boundary layers over low-pressure turbine (LPT) blades via different mechanisms such as free-stream turbulence, upstream wakes, and surface roughness. These mechanisms have proven to be beneficial in mitigating the separation bubble-related losses in ultra-high lift blade designs, despite an increase in the loss due to increased turbulent wetted area (TWA). In this work, we adopt a strategy of employing surface roughness in the transitional regime to minimize the separation bubble-related losses and flush mounted riblets downstream to further mitigate the skin-friction drag and boundary layer losses due to an increase in the TWA. Several high-fidelity scale resolving simulations are performed on this ‘rough-ribbed blade surface’ to discern the effect of varying the riblet spacing (s+) and height (h+). The streamwise evolution of skin-friction coefficient, boundary layer integral parameters and shape factor are compared and contrasted among riblets of different dimensions. The instantaneous flow features and second order statistics such as the Reynolds stress, turbulent kinetic energy and its production are analyzed for different test cases to determine the impact of riblets on these quantities. When compared to the roughness alone configuration, the scalloped shape riblets with s+ = 17 and h+ = 22 reduced the net skin-friction drag by 7.3% and the trailing edge momentum thickness by 14.5% thereby demonstrating the efficacy of riblets in reducing the mixing losses under adverse pressure gradients. Through an analysis of flow blockage introduced by the application of riblets, the deleterious effects of increasing the riblet height along with the necessity of optimizing the riblet ramp are highlighted.
Life Cycle Analysis of SiC Samples in a Stagnation-Point Reacting Flow
Authors: Nair Chinmay , Cooper John , Cha Chong M. , Chelliah Harsha K. 
Published: September 2023

Abstract
A laboratory scale high-pressure flow reactor has been developed to study the interaction of a steam jet with various advanced ceramic and environmental barrier coating materials. Previous research studies were conducted at close to atmospheric pressure and have proposed an empirical relation for material surface recession. But none of them have been able to extract a pressure dependence factor with high fidelity. To address this deficiency, in the present study test conditions of steam at 1400 Celsius, pressures up to 5 atm, and velocities exceeding 200 m/s (positioned at 1 mm from the surface and at variable impinging angles) have been considered. These conditions mimic the local water molecule number density and velocity in actual gas turbine engine components, with test duration exceeding 24 hours. The initial life cycle data of Chemical Vapour Deposited Silicon Carbide (CVD SiC) interactions with water vapour show very interesting physical and chemical mechanisms controlling the recession rates. Complementary well-resolved computational fluid dynamic simulations have been performed to support the experimental setup and results, shedding new insight into the role of stagnation regions in the flow field where the flow residence times are the highest.
Development and Experimental Validation of a Model-Based Balancing Prediction Method for Bowed Rotor
Authors: Checcacci Damaso , Ferraro Riccardo , Girezzi Gabriele , Mitaritonna Nicola , Orazi Claudio 
Published: September 2023

Abstract
Rotor balancing is one of the most discussed topics in the field of rotor-dynamics. It is very important in the industrial practice and sometimes there are very particular cases that cannot be addressed and solved by traditional methods.
The rotor model addressed in this paper has been initially presented in a previous work [1], with the aim to introduce a procedure for “predicting the effects of balancing” at rotational speeds that are higher than those possible on balancing machines.
In this work, the balancing of the same rotor model is addressed by a maintenance standpoint, considering the case of a rotor showing bending at its neutral axis. This situation may be present, for several reasons, in rotors sent to the Original Equipment Manufacturers (OEMs) for repair/refurbishment after several years of operation, or as consequence of emergency events that may cause local deformation and/or require significant re-machining. To some extent, this situation can still allow for High-Speed Balancing (HSB) of such shafts. Nonetheless the availability of prediction models able to evaluate in a relatively short time the feasibility of HSB, in advance of starting any hardware activity, is of paramount importance to avoid costs and time impacts.
In this paper, a procedure to address the feasibility of balancing of an industrial steam turbine rotor, starting from runout measurement of its bowed shape, is presented. Hence, results of several approaches are discussed for identification of their limits of applicability. Eventually the result of an analytical model including the deflected shape of the shaft is compared with HSB runs.
Methodical Evaluation of Process Chains for the Manufacturing Of Rotating Engine Components – Blisk | IBR
Authors: Seimann Martin , Heinen Daniel , Cassel Leonard , Bergs Thomas 
Published: September 2023

Abstract
In future, component requirements of blade integrated disks (Blisk) / integrally bladed rotors (IBR) as well as turbine and compressor discs will become more challenging as today exhibiting more complex and downsized geometries, tighter tolerances and are made of more difficult to machine materials (e.g. advanced Ni- and Ti-alloys). This means that the process portfolio is getting significantly broader as components will not be manufacturable as of today mainly using conventional technologies. Adaptive process chains are required, specifically developed for each component.
To decide which process chains are feasible and which are most suitable the paper describes the approach of developing a modular evaluation methodology. The methodology considers process capabilities of the manufacturing technology as well as economic boundary conditions. Within the described systematic methodology, process capabilities are evaluated against different component properties (geometrical variation, workpiece material, etc.) and provide an overview on available technologies for certain designs. The process know-how was gained by shop-floor investigations identifying the process limits (e.g. accessibility). The methodology is explained in the following by means of Blisk/ IBR components.
A Framework for Evaluation of Cyber Security Risks Using Monitoring Data
Authors: Lieuwen Timothy , Perullo Christopher , Kee Jared 
Published: September 2023

Abstract
This paper outlines a process for proactive mitigation measures for detecting and preventing threats through detection of exploited vulnerabilities in power generation assets. In many cases, these vulnerabilities are only known to deep domain experts who are familiar with the intricacies of how these systems work, and not to cybersecurity experts. While a focus on IT security. represents the first line of defense, successful attacks on the OT systems can go beyond disruption to business operations or service and can lead to catastrophic equipment failure. Recent advancements in monitoring and diagnostics technology have been used to protect OT equipment from normal wear and tear but have not been fully operationalized to assist in detecting intrusions.
Monitoring and Diagnostic (M&D) centers typically collect significant sensor data with the aim of detecting faults and failures in operating equipment; however, collection and analysis of additional data including control system settings, verification of sensor signals, and verification of proper actuator function is typically not analyzed. These functions are almost certainly not analyzed from the specific perspective of cybersecurity OT attacks. To help aid in discussions between plant engineers, M&D, and IT/OT, a process and examples are presented for identifying potential attack vectors in the cyber-physical OT systems. This includes a systematic identification of potential systems, categorical attack mechanisms, and cataloguing of the resulting impact.
Analysis of Unsteady Loss Sensitivity to Incidence Angle Variation in Low Pressure Turbine
Authors: Dellacasagrande Matteo , Lengani Davide , Simoni Daniele , Ubaldi Marina , Granata Angelo Alberto , Giovannini Matteo , Rubechini Filippo , Bertini Francesco 
Published: September 2023

Abstract
In the present work, Large Eddy Simulations (LES) of a low pressure turbine cascade have been carried out to understand the different sensitivity to incidence angle variation observed under steady and unsteady inflow conditions. Indeed, experimental evidence shows poor sensitivity to incidence angle variation for the steady case in a range of −9° ≤ i ≤ +9°, while losses grow rapidly in the unsteady flow environment. It will be shown that this is due to wake migration into the core flow region, producing an additional source of losses for the unsteady flow case. Both steady and unsteady simulations have been carried out at nominal and two positive and negative incidence angles.
The LES data have been inspected to identify the physical reasons behind the different loss trends, after being validated by means of blade loading and loss coefficient distributions. To this end, Proper Orthogonal Decomposition (POD) has been applied to each dataset. POD modes clearly identify the different structures responsible for loss production in the steady and the unsteady operation of the cascade. The structures carried by upstream wakes have been isolated and identified both in the boundary layer and in the core flow. The process of bowing, tilting and reorientation of the wake filaments and related structures is shown to be the dominant mechanism responsible for the strong loss sensitivity to the incidence angle variation observed under unsteady inflow. Otherwise, structures responsible for the transition of the blade boundary layer do not exhibit significant variation for both the steady and the unsteady flow cases, thus further strengthening that the sensitivity to incidence variation is mainly due to wake migration into the core flow region. This loss source is not classically considered in literature correlations and actual design processes.
Adapting Artificial Neural Networks Training Algorithms to Adjoint-Based Aerodynamic Shape Optimization
Authors: Gisbert Fernando , Cadrecha David , Quintanal Jaime , Sotillo Adrián , Pueblas Jesús , Serrano Aida , Puente Ricardo , Corral Roque 
Published: September 2023

Abstract
Gradient-based algorithms are one of the pillars of automatic aerodynamic design in the turbomachinery field. Their use is largely extended due to their low computational demand when dealing with hundreds of design variables, especially if gradient computation is performed by means of an adjoint code. Difficulties arise when facing 3D aerodynamic inverse design, trying to obtain automatically a 3D blade geometry that produces a prescribed pressure distribution while fulfilling certain other aerodynamic constraints. Fine-tuning this target pressure distribution along the blade span — with varying fluid conditions along it — generally involves a high number of iterations, making overall automatic design process expensive from a computational point of view.
Many numerical methods have been employed in order to cope with the bad convergence exhibited by basic gradient descent method for ill-conditioned problems: quasi-Newton methods, conjugate gradients, sequential quadratic programming algorithms, among others. However, bad convergence of basic gradient descent method on ill-conditioned problems is not exclusive to 3D aerodynamic inverse design. In the field of artificial intelligence and machine learning, this problem is common when training neural networks.
In order to accelerate the convergence exhibited by gradient descent method on the aforementioned case, this paper makes use of one of the most common adaptive gradient-based methods in the field of neural networks training: Nadam optimizer. Firstly, the principles that allow this method to overcome ill conditioning are explained through Brachistochrone problem example. Secondly, the architecture of this aerodynamic automatic design module is detailed, paying special attention to gradient computation, mesh generation and objective function construction.
Finally, an automatic 3D inverse design of a low-pressure turbine blade, driven by this adaptive step-size algorithm, is performed. The automatic design optimization presented here is carried out in a realistic industrial manner, taking into account different operation conditions in order to mimic human performed design.