bluuebunny/crossref_metadata_2025_split huggingface dataset:
Numerical Analysis of Multi-Stage Impingement Cooling Structure: Flow and Heat Transfer Characteristics
Authors: Wang Pengfei , Wang Pei , Liu Jun , Liu Jiajie , Du Qiang , Liu Haoyang , Wang Zhiguo , Wang Haohan 
Published: August 2024

Abstract
Impingement cooling is widely employed for thermal regulation of high-temperature components in gas turbine engines, owing to its high local convective heat transfer coefficients. However, the effectiveness of this method is compromised by the external crossflow caused by spent air from upstream jets, particularly in single-stage narrow channels with significant external crossflow. This study explores the flow and heat transfer characteristics of an innovative multi-stage impingement cooling structure. Our numerical analysis reveals that this multi-stage configuration significantly reduces the adverse effects of external crossflow, while also improving coolant utilization efficiency. Compared to the single-stage configuration, the multi-stage structure achieves higher Nusselt numbers on the target surface with only half the coolant consumption at an equivalent Reynolds number. The analysis indicates that single-stage configuration is inferior in terms of coolant mass flow rate and Nusselt number distribution, especially at minimal jet-to-target distances. In contrast, the multi-stage configuration effectively manages external crossflow, leading to a more uniform distribution of coolant and Nusselt number on the target surface. The superiority of the multi-stage configuration is further evidenced by its overall thermal efficiency, which considers both flow resistance and heat transfer. Moreover, a small transition chamber height in the second-stage can induce strong internal crossflow, potentially affecting optimal impingement cooling performance.
Vibration and Acoustic Emission Assessment of a SiCf/SiC Ceramic Matrix Composite With Damage
Authors: Jeffs Spencer P. , Stephen Jordan , Quiney Zak , García Luna Gonzalo 
Published: August 2024

Abstract
SiCf/SiC Ceramic Matrix Composites (CMCs) offer considerable advantages over existing metallic systems employed in hot section components in the gas turbine engine. However, due to their complex structure there are a number of damage modes that can occur under mechanical loading, such as matrix cracking, interfacial cracking and fibre failure. Therefore, there is a requirement for test methods, that are in-situ and ex-situ, to help understand these damage modes, in terms of how and when they take place and what they mean relative to material condition.
The article investigates the use of vibration testing as a means of condition assessment through analysing the vibration response of undamaged and damaged SiCf/SiC CMC material. Cantilever beam vibration experiments were conducted before and after a series of mechanical loading conditions. Resonant frequency values were extracted using the Fast Fourier Transform (FFT) and compared, revealing a correlation between changes in natural frequency relative to the undamaged material, and the mechanical loading level, thus a correlation with the level of damage in the CMC. In addition, acoustic emission (AE) testing was carried to support the understanding of the damage mechanisms taking place in the CMC. The results reveal that vibration testing could potentially offer an alternate nondestructive evaluation (NDE) technique to assess the condition of CMC material.
Predicting Gas Turbine NOx Emissions With Machine Learning
Authors: Eller Harrison , Singh Sanjana , Soni Sumit 
Published: August 2024

Abstract
Gas Turbine operations result in production of Nitrogen Oxides (NOx) and Carbon Monoxide (CO), both of which are pollutants that are to be strictly monitored and controlled. To control NOx within permissible limits, Combustion Emissions Monitoring System (CEMS) readings are to be continuously monitored and flagged for any anomaly in NOx emissions. This paper covers the method for developing a proof of concept of a Machine Learning (ML) model that predicts NOx from a selected pair of General Electric 7FA (7FA) and Siemens Westinghouse 501F (SW501F) gas turbines that are actively monitored in real time. The Keras library and the open-source machine learning framework TensorFlow are used for constructing, developing, testing, and tuning all respective models in Python. The authors show that working with quantitative, time-series data, a deep neural network (DNN) using a rectified linear unit activation function is deemed the most appropriate for the given issue at hand. Using this framework in conjunction with the domain knowledge from a monitoring and diagnostic team and gas turbine experts, a DNN for each frame type is successfully constructed. The 7FA test site and SW501F test site produced NOx predictions with a mean absolute error of 0.55 and 0.7 ppm respectively, hence demonstrating the capability of a machine learning model to accurately predict NOx emission for any typically trained scenario.
Numerical Study on Unsteady Flow of a Supersonic Partial Admission Impulse Turbine
Authors: Li Tongxi , Wang Jiakang , Wang Zhiheng , Xi Guang 
Published: August 2024

Abstract
Partial admission is an essential method to ensure the effective operation of turbines in various operating conditions. The transition section of partial admission turbines is pivotal in governing the unsteadiness and non-uniformity, yet its flow dynamics remain somewhat elusive. To enhance the comprehension of the flow characteristics within supersonic partial admission impulse (SPAI) turbines, this study employs a three-dimensional unsteady numerical simulation on a singlestage SPAI turbine equipped with four circular nozzles. The findings reveal that shock waves are produced at the leading edge of the admission area, and flow separation occurs twice on the suction surface. In the non-admission area, the fluid is in a turbulent state and predominantly static. Particularly in the transition section, processes of emptying and filling are evident. An intense shock wave forms at the entrance to the channel in the transition section leaving the admission area, as the high- and low-energy fluids mix in the subsequent channels, resulting in significant energy losses. During the rotor rotation, the blades experience fluctuating aerodynamic forces, which are pronounced in the admission area, while negligible in the non-admission area. These forces are mainly dominated by the intake passage frequency and other frequencies associated with nozzle spacing. Phenomena of under-shoot and over-shoot are observed as the blades enter or exit the admission area, potentially impeding turbine performance or providing additional torque.
Workflow for Fast and Efficient Forced Response Analysis of Turbomachinery
Authors: Patil Sunil , Sabatier Laurent , Madden Andrew , Bronson Jeff , Zori Laith 
Published: August 2024

Abstract
The advances in turbomachinery methods over the last decade have led to unsurpassed simulation fidelity. Computational Fluid Dynamics (CFD) methods for turbomachinery, including multistage blade rows, have become reliable and robust. Finite Element Methods (FEM) in the area of mistuning have become established throughout the industry.
However, current day-to-day aerodynamic methodology still relies heavily on simplifications, reduced methods, and low-fidelity analyses. One impediment is the workflow bottlenecks: taking data from one system, transforming it, and using it another.
This paper lays out a streamlined workflow for forced response of bladed turbomachinery components, linking CFD with FEM for tuned or mistuned forced response. At each stage, high fidelity solutions are used eliminating the need for simplifying assumptions and limiting methods. Additionally, manual steps are replaced with automated and verifiable steps. Both the CFD and FEM rely on making use of the cyclic symmetric nature of the solution fields, leading to fast and accurate solutions. Technologies such as phase lag approach on CFD side, and mode superposition on FEA side are explained to speed up overall time to solution significantly.
Lastly, the forced response workflow includes built-in utility to quickly extract the vibrational stresses and strains, especially equivalent (von Mises) and principal values, required for high-cycle fatigue and lifing calculations.
Forced response of the NASA Rotor 67 fan subjected to inlet distortion is used in this work to highlight the streamlined workflow.
Performance Comparison of Gas Turbine Layouts With Pressure Gain Combustion for Propulsion Applications
Authors: Purushothaman Sreenath , Sorce Alessandro , Traverso Alberto , Gaillard Thomas 
Published: August 2024

Abstract
Different pressure gain combustion methods such as Constant Volume Combustion (CVC), Pulse Detonation Combustion (PDC), Rotating Detonation Combustion (RDC) and Oblique Detonation Wave Combustion (ODWC) are being explored for aerospace propulsion applications in recent years. In order to fully utilize the benefits of pressure gain combustion, it is necessary to analyze the propulsion engine from a system level. This includes the study of integrating pressure gain combustor with other components such as compressors and turbines, investigating the effects of combustor and turbine cooling, as well as engine performance under different operating conditions. In this paper, the performance of different engine layouts employing pressure gain combustion is studied. An RDC chamber is chosen as reference combustor technology, interacting dynamically with compressors, turbines, ejectors, and other engine components. All layouts are designed to provide a maximum design thrust of 100 kN, which is typical of a high bypass commercial turbofan engine. The combustor dynamic model is based on theoretical pressure gain combustion maps with a wide operational envelope, while the compressors and turbines are based on actual engine data, scaled to match the combustor operation. The results show the benefits and limitations of using pressure gain combustion in propulsion system in the most promising engine layouts.
Energy and Cost Analysis of Concentrated Solar Thermal Plants Integrated With Latent Heat Thermal Energy Storage for the Decarbonization of Industrial Processes
Authors: Giampietro Davide , Stefanizzi Michele , Fornarelli Francesco , Dambrosio Lorenzo , Nicolini Daniele , Miliozzi Adio , Camporeale Sergio Mario 
Published: August 2024

Abstract
Industrial energy demand in the EU is driven by the thermal energy share, which accounts for the most part of the total energy demand. A large part, about one-third, is at medium temperatures, between 100 and 200 °C, and it is still produced by fossil fuels, mainly natural gas. This energy demand could be met by solar thermal energy by using Concentrated Solar Thermal (CST) technologies, suitably combined with thermal energy storage systems.
This paper presents a study of CST plant composed by Parabolic Trough Collectors (PTC) combined with Latent Heat Thermal Energy Storage (LHTES) system in shell-and-tubes configuration for the supply of heat for industrial processes. Firstly, the criteria adopted for the sizing and the quasi-static simulation of the system are described. Significant attention is given to evaluate the variation of the Solar Fraction (SF) with the typical parameters of thermal storage, such as the maximum capacity and exchange surface, given a specific location and the Solar Multiple (SM). The methodology has been applied to a dairy processing facility within the agri-food sector with a thermal load of 500 kWth. Then, an economic analysis has been carried out by evaluating the impact of the component’s costs, such as the linear parabolic collectors, thermal storage materials and landscape preparation. Finally, the Levelized Cost of Heat (LCOH) has been computed for different thermal storage sizes in order to find the best combination that minimizes it. As a result, despite the overall increase of the SF with the thermal storage capacity, the proposed work shows how the minimum value of the LCOH (7.24 c€/kWh) corresponds to low storage capacity (1 MWh).
Propelling Education: Introducing and Examining the “English-to-Engineering” Multi-Year Undergraduate Research Program
Authors: Martinez Soto Karen , Haldeman Charles , Teolis Samuel , Gray David , Lowe Todd 
Published: August 2024

Abstract
A student-led, industry-affiliated, extracurricular undergraduate program has been developed at Virginia Tech which is entering its third year. The program was developed with an umbrella theme of sustainability in aerospace propulsion under which the original students “auditioning” for the program proposed a range of research topics. The original program structure was focused on addressing some shortfalls observed both by academia and industry relative to traditional undergraduate engineering education over many years. Broadly speaking, these issues can be separated into topics related to encouraging earlier exposure to open ended problems and the ability to practice a wide range of teaming exercises earlier in the student’s career, both of which are of high value to industry. Discussion around these challenges has been ongoing, but often curriculum constraints have made incremental solutions hard to generate. The current incarnation of this program is as an extracurricular activity, focused on student-owned, multi-year projects. At the time of the program creation, it was not clear if such a program would be of interest to the students, or if industry and faculty could provide the required support. Three years into the program it is clear that this approach is widely accepted and valued by all parties, but most fully by the students. The program is addressing part of the needs outlined originally, but as the program enters its next phase, the ability to address the successes and challenges of the current system needs a more formal educational framework. This paper focuses on describing the current program, and some of the limitations that having a multi-year, student-owned project provides in frameworks such as Fink’s Taxonomy of Significant Learning. This is important as the lessons of this experience are considered by other academic institutions with a goal of fully leveraging the student experiences and capabilities provided by this approach. Academic and industry perspectives are critical as the next phase of the program need to generate greater and different industry involvement and fuller integration into the existing curriculum to provide maximum value to the students, faculty, and industry.
Steam Turbine Low Pressure 75in Last Stage Blade for Nuclear Half Speed Applications
Authors: Kostyuchenko Sergey , McBean Ivan , Masserey Pierre-Alain , Casu Christian , Noirot Vivian , Lemaire Julien , Berquier Christophe 
Published: August 2024

Abstract
The impact of global warming is driving the current trend in the power industry to transition away from employing fossil fuels for power production. Nuclear energy has been demonstrated to be a safe, reliable, and dispatchable way of generating either base load power or to balance fluctuations in renewable power. General Electric has further developed its Arabelle steam turbine platform to address the growing demand for nuclear power. This included the development of one of the longest low pressure steam turbine last stage blades, at 75 inches. Due to the sheer size of the turbine components, the development of this turbine posed several challenges, from both mechanical integrity and design perspectives. This paper documents the design development, validation, and manufacturing processes of the low-pressure turbine last stage blade.
Mechanical Behavior of Nozzle Guide Vane Bushing in Absence of Lubrication by Means of Novel Endurance Test Rig
Authors: Bucciarelli Federico , Tomasello Stella Grazia , Bellacci Michelangelo , Checcacci Damaso , Ghiara Antonio , Maestrale Francesco , Manconi Salvatore 
Published: August 2024

Abstract
Nowadays, Variable Guide Vanes such as Inlet Guide Vanes (IGVs) and Nozzle Guide Vane (NGVs) are key components in the design of axial expanders and gas turbines, which are now required to work with an ever-increasing flexibility due to the frequent shutdowns, start-ups and load changes to which they are subject. Such severe service conditions, due to the ever-increasing introduction of the renewable energies in the energy market, are particularly challenging for such components, which were already intrinsic complex in order to obtain higher availability performances. For this reason, a deeper understanding of the mechanical behavior of such components by means of experimental characterizations has become mandatory for the design process, especially when high loads are involved.
Under such premises, the present work, starting from the recently presented novel design of an experimental test rig, aims at showing the results of a testing campaign performed on standard and coated bushing. The test article manufacturing technology selected for the campaign will be presented. Then results of static testing, aimed at measuring friction coefficients of the whole kinematic assembly, will be summarized both at room and operating temperature both for new and worn geometries. Also, the outcomes from accelerated endurance tests, lasting 200h and performed with peak temperature of 525°C in absence of lubrication, will be reported giving insights on the design of these kinematic couples. Inspections of analyzed specimens are also included in the postprocessing. These results are a key element for the improvement of the life prediction of these components enabling progressively more challenging operating conditions for the next generation of expanders.
Impact of Different Equations of State in the Turboexpander Design for Allam Cycle
Authors: Alfarano Emanuela , Michelassi Vittorio , Fantozzi Francesco 
Published: August 2024

Abstract
Clean, affordable, and reliable power generation is at the very center of our present and future needs. While renewable power sources are increasing their penetration in the energy mix, natural gas with carbon capture will still play a key role. Oxyfuel combustion is a promising technology that combines power generation and carbon capture without the need for a dedicated carbon dioxide capture plant. In particular, the Allam cycle employs natural gas oxy-fuel combustion in a supercritical carbon dioxide environment with a turbine expansion. The design process of such a turbo-expander comes with significant challenges due the unique aero-thermal operating conditions. Moreover, the evolving fluid mixture properties are still largely unknown.
The present paper investigates the impact of uncertainties in supercritical carbon dioxide mixtures thermodynamic models on the design and performance of the turboexpander in an oxycombustion power cycle. After providing a review on the current equations of state available for supercritical carbon dioxide mixtures with steam, the paper quantifies the influence of equations of state differences in the turboexpander unit design and operation. The paper also addresses the importance of the equation of state on the Allam cycle thermodynamic model in view of its application to industry relevant sizes.
In-Situ and Ex-Situ Measurement of Stresses in Environmental Barrier Coatings
Authors: Hudyncia Hans , Shi Jun , Li Weizhou , Li Xiaodong 
Published: August 2024

Abstract
Ceramic Matrix Composites (CMCs) offer a step improvement in temperature capability over the current best high temperature super alloys for gas turbine applications. Silicon Carbide (SiC) based CMCs react with water vapor at temperature and therefore need an Environmental Barrier Coating (EBC) for protection against the water vapor attack. EBC is typically deposited on a CMC component through Air Plasma Spray (APS) process, which involves melting and fast quenching of molten ceramic powders (such as ytterbium disilicate and ytterbium monosilicate). The fast quenching and subsequent cool down to room temperature introduce residual stress in the EBC. In addition, EBC coated CMC components often go through a heat treatment process afterwards. For Yb-silicates, this both stabilizes/crystalizes the EBC and increases hermiticity by healing cracks and pores. This heat treatment at elevated temperature changes the coating residual stress state. It is important to be able to measure the coating stresses during deposition and heat treatment so that APS process improvement and EBC coating life assessment can be made. This paper describes novel methods to measure coating stresses continuously during APS and during heat treatment up to 1400°C, using an optical deformation and curvature-based approach.
Adaptation of Air Centrifugal Compressor Stages for Hydrogen-Based Economy: Impact on the Design Point and its Corresponding Flow Coefficient
Authors: Kienzle Norman , Al Arafa Mushfiq , di Mare Francesca , Budt Marcus 
Published: August 2024

Abstract
One approach to saving time and R&D capacity in providing a compressor stage portfolio for a hydrogen-based economy is to adapt established air centrifugal compressor stages for operation with hydrogen. However, this shift from air to hydrogen operation in air-ready centrifugal compressor stages results in notable changes in the design point and its corresponding flow coefficient. These alterations arise due to distinct gas properties, differences in pressure ratio, and outlet temperature.
The design point flow coefficients for the analyzed air-driven centrifugal compressor stages spanned from 0.04 to 0.1. To predict the hydrogen operation of these stages there is an urge to predict the flow coefficient range for the new gas. Therefore, this paper aims to comprehensively investigate the impact of shifting from air to hydrogen mode on the design point and its corresponding flow coefficient. The transition has been analyzed by developing a comprehensive methodology that integrates a prediction method, 1D mean line calculation, computational fluid dynamics (CFD) analysis, and a corrector method. The investigation has been conducted on five different centrifugal compressor stages at a wide range of flow coefficients. The maximum speed of the individual stages has not been exceeded to ensure that the machines remain structurally feasible.
The findings derived from the simulation results suggest that air-ready centrifugal compressor stages, when operated with hydrogen, experience a shift in the peak efficiency point flow coefficient. This mode shift leads to a reduction in the peak efficiency flow coefficient; hence the hydrogen design point flow coefficient of air-designed stages is in the range of 0.02–0.08. An investigation to analyze the flow coefficient dependency on gas molecular mass and other factors is carried out to explain the findings. Then, the hydrogen peak efficiency flow coefficient can be used for the 1D mean line calculation of air-ready centrifugal compressor stages for hydrogen mode.