bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stress Analysis and Life Assessment of the Steam Turbine Rotor During Peak Shaving Transient Processes
Authors: Fan Mengyang , Zhao Yongliang , Liu Ming , Wang Chaoyang , Wang Zhu , Yan Junjie 
Published: October 2024

Abstract
To achieve the net-zero emissions targets, the global share of renewable energy is rapidly increasing. The high penetration of intermittent and variable renewable power necessitates that coal-fired power plants enhance their operational flexibility for peak shaving and frequency regulation. Frequent and rapid start-ups, shutdowns, and peak shaving processes pose significant safety challenges to the steam turbine rotors. This paper investigates the impact of flexible operation on rotor stress. Firstly, an online monitoring model was developed and verified using a finite element model of a steam turbine high-medium pressure rotor. Secondly, the online calculation model was integrated with a dynamic coal-fired unit model developed using the JTopmeret software on the GSE platform, a well-established dynamic simulation tool for nuclear and fossil fuel power plants. Finally, a rotor low-cycle fatigue life assessment model was developed, and the von Mises stress and fatigue life loss under various load variation rates and ranges were determined. As the load variation rate increases, the life loss increases significantly, with maximum von Mises stress amplitudes of 5.2, 6.5 and 7.8 MPa at 1%, 2% and 3% Pe min−1 load variation rates, respectively. Conversely, as the load variation range increases, the life loss decreases substantially, with maximum von Mises stress amplitudes of 9.2 and 5.0 MPa during load variation processes of 50%–75% and 75%–100% THA, respectively. This study provides detailed guidance for optimizing the safe operation and control strategies of coal-fired power plants.
Enhanced Thermal Performance in Evacuated Tube Solar Collectors Using Titanium Oxide Nanoparticle: a Computational Fluid Dynamics (CFD) Investigation
Authors: Al Nawafah Qais , Al Nawafah Hamza , Amano Ryoichi S. , Abousabae Mohamed 
Published: October 2024

Abstract
This study focuses on improving thermal performance in evacuated tube solar collectors (ETSCs) by incorporating titanium oxide (TiO2) nanoparticles into the working fluid. Our work, which aims to improve the efficiency of solar thermal systems, uses Computational Fluid Dynamics (CFD) modeling to predict the heat transfer characteristics and fluid dynamics in ETSCs. The effect of incorporating TiO2 nanoparticles into the base fluid on improving the system’s thermal conductivity and overall heat transfer efficiency is investigated. The report introduces a thorough simulation framework that replicates real-world settings and examines the effect of nanoparticle concentration on the thermal characteristics of the working fluid. The core objective is to investigate how TiO2 nanoparticles can enhance the thermal conductivity of the working fluid, thereby improving the overall efficiency of solar thermal systems. The CFD model results are notable, revealing a substantial enhancement in the performance of solar collectors. The efficiency of ETSCs is observed to increase by 12.5%, primarily due to the improved thermal conductivity achieved with the incorporation of TiO2 nanoparticles while maintaining a negligible impact on the fluid’s viscosity. Future work will implement a prototype of the proposed system to study its performance experimentally and compare it with the simulated results.
Operational Flexibility and Thermodynamic Performances of a Combined Heat and Power Plant Integrated With Carbon Capture System
Authors: Liu Xingyan , Fu Yue , Liu Ming , Wang Zhu , Yan Junjie 
Published: October 2024

Abstract
The global energy mix is evolving to sustainable and low carbon, so carbon capture should be developed and applied for the decarbonization of coal-fired power plants. Many coal-fired power plants have been reformed to combined heat and power, which can bring significant energy saving and economic benefits. When the combined heat and power plant is integrated with post-combustion carbon capture system, the carbon capture system will consume much steam extracted from steam turbines, and the heat and power outputs of the power plant will be influenced. Therefore, operational flexibility and thermodynamic performances of a combined heat and power plant integrated with carbon capture system will be evaluated in this study. A 660MW subcritical power plant is analyzed as the reference case, and a large-scale carbon capture system is integrated. The carbon capture system is driven by the exhaust steam of the intermediate pressure cylinder. The off-design simulation model of the coal-fired power plant is developed and validated, and the Aspen Plus software is used to develop the model of the carbon capture system. The integrated system is optimized to decrease the energy consumption of the carbon capture system, Then, operational flexibility and thermodynamic performances of the integrated system is evaluated. Results show that the adjustable ranges of heat and power loads decrease due to the integration of CCS. The energy efficiency within the operation domain in dominated by the heat load, but power load has higher influence on the exergy efficiency than the heat load. The coal consumption rate for carbon capture system is about 0.09kg/kg.
Advanced Digital Techniques for Monitoring Dynamic Compressor Instabilities Through Non-Intrusive Approaches
Authors: Ratto Maurizio , Silvestri Paolo , Reggio Federico , Traverso Alberto , Pascenti Matteo , Cousins William T. 
Published: October 2024

Abstract
Nowadays, electrification of thermal users is strategic for energy transition. In such a context, centrifugal compressors in heat pump systems are experiencing an increasing relevance. Furthermore, thermal demand fluctuations require highly flexible compressors and efficient off-design operations, which may increase the risk of centrifugal compressor instable behavior. This paper presents an innovative approach to monitor electrically-driven compressors, validated through established vibro-acoustic signal processing, applied to a prototype heat pump rig operated at University of Genoa laboratory, equipped with a 7kW variable speed centrifugal compressor, driven by an inverter. First, the system signature characterization is performed in stable operation. Afterwards, compressor instability and surge transients are initiated and maintained by progressively closing the expansion valve in the plant, acquiring the signals before and after instability onset. In this way, suitable surge precursors can be identified and monitored, until full surge cycles establish. The frequency analysis of system dynamic responses is performed in both the sub-synchronous and the high frequency ranges. An early surge detection is demonstrated to be possible basing on electrical motor signals. Thanks to the use of such non-intrusive probes, it is shown that effective diagnostic indicators can be obtained without interacting directly with the working fluid, therefore preserving system integrity and reliability and allowing also retro-fit applications. This paper proves for the first time the effectiveness of radial compressor surge monitoring through electrical signals in a closed loop refrigeration system. The experiments are conducted both during “dry” compressor operation as well as “wet” compression operation, i.e. through refrigerant droplet injection at compressor inlet.
Investigation of NOx Generation and Ammonia Fuel Utilization in a Solid Oxide Fuel Cell
Authors: Wilhelm Cole , Willsey Aliza , Ahn Jeongmin 
Published: October 2024

Abstract
Decreasing the generation of CO2 from energy production is a key area in energy research and environmental sustainability. Fuel cells represent a solution to reducing CO2 generation through the use of hydrogen fuel to generate electricity. However, the widespread use of hydrogen fueled fuel cells is generally limited by difficulty of hydrogen storage, transportation, and synthesis. The primary issue with hydrogen storage is that gaseous hydrogen contains low volumetric energy density. One promising option to address these difficulties is the use of ammonia (NH3) in solid oxide fuel cells (SOFCs), which allows for storage of a liquid fuel source, rather than the highly compressed gaseous fuel. Previous work has shown that a SOFC using ammonia fuel is highly capable of generating electricity at levels comparable to that of pure hydrogen fuel. The nickel within the SOFC, along with the high operating temperatures, assists in the thermal cracking of ammonia. However, one missing piece from our previous work is an investigation of ammonia utilization. As such, this work will seek to evaluate the utilization though an exhaust gas analysis using mass spectroscopy and gas chromatography. Additionally, the exhaust gas composition is monitored for the presence of NOx group gases. With the use of ammonia as the fuel source, there is a possibility that we see nitrogen bonding to oxygen ions at the triple-phase boundary (TPB), leading to NOx formation. Given the danger presented by these gases, we must be certain that the concentrations are negligible, or that there will be sufficient NOx reduction strategies in the exhaust stream. SOFC performance results will be briefly discussed, along with an analysis of exhaust composition using gas chromatography and mass spectroscopy to demonstrate utilization of ammonia and evaluate NOx generation relative to fuel cell electrical performance at various operating temperature.
Experimental Study of Instabilities in Hydrogen-Air Fueled Rotating Detonation Combustion
Authors: Weber Justin M. , Johnson May Kristyn B. , Ferguson Don H. , Bedick Clint R. , Strakey Peter A. , Sidwell Todd G. 
Published: October 2024

Abstract
Conventional gas turbine engines rely on an idealized constant pressure combustion process that in reality produces a pressure decrease as a result of viscous and other non-reversible losses. An alternative approach is rotating detonation combustion (RDC) which is a form of pressure gain combustion in which one or more detonation waves propagate an annular channel resulting in an increase in pressure across, subsequently providing greater work availability compared to deflagration ultimately leading to opportunities for greater thermodynamic efficiency when used in gas turbine engines that conventionally relies on constant. Modern gas turbine engines often rely on pre-mixed reactants to limit NOx emissions, although this may result in greater susceptibility to instabilities such as flashback and thermoacoustic oscillation, particularly for applications that utilize hydrogen as the fuel. Research in RDC has focused on non-premixed reactants thus limiting the occurrence of flashback, and high frequency detonation wave propagation (kHz) may interfere with the occurrence of thermoacoustic oscillations. Thermal NOx emissions are controlled through rapid combustion and sudden expansion of the working fluid. Although RDC may not be susceptible to instabilities encountered in conventional state of the art gas turbine engine combustion, there may be other mechanisms occurring that support instabilities that could be detrimental to performance.
The design of systems utilizing RDC often incorporates a choked inlet and exit boundary conditions, but since the RDC is an inherently unsteady process it is unlikely these boundaries remain choked over the course of a complete cycle (complete rotation of a detonation wave). The presence of multiple waves could further exacerbate changes in choked conditions at inlet and exit boundaries. As a result of restrictive and changing conditions at the boundaries, reflected shock waves may occur traveling upstream from the exit or downstream from the inlet that interfere with the reactant inlet flow, mixing, and subsequent formation of a detonation wave (for example, variable wave height). The objective of this study is to utilize experimental data from multiple dynamic pressure transducers located along the length of an RDC combustor, supplemented with ion probe (chemical ionization) and OH* chemiluminescence acquired within the detonation region, to identify occurrences of instabilities during 20–30 second tests. The length of the test provides an adequate time for the combustor to reach a thermally stable condition. The axial distribution of dynamic pressure transducers provides a means of tracking reflected shock waves within the combustion channel. Experimental data are compared to a limited number of computational results that include both stable and unstable conditions with the detonation channel.
Modeling of a Novel Elastohydrodynamic Seal for sCO2 Power Cycles With Experimental Verification
Authors: Hayne Cole , Topu Ali Akbor , Hassan Mohammad Fuad , Sercer George , Xu Hanping , Cesmeci Sevki 
Published: October 2024

Abstract
Effective sealing remains to be one of the technological challenges at the subcomponent level for supercritical carbon dioxide (sCO2) power generation to be practical. Leakages from sCO2 power cycles can lower cycle efficiencies by up to 0.65%. Therefore, to fully harness the benefits of sCO2 power generation; this leakage must be addressed through engineering of efficient sealing technology. To this end, we propose an elastohydrodynamic (EHD) seal as a potentially effective solution that can operate at sCO2 conditions with minimal leakage and wear. In this study, an FEA/CFD based fluid-solid coupling modeling approach was presented with experimental verification. For proof-of-concept purposes, the tests were performed on a 2” static shaft seal and with pressures up to 1.2 MPa using PTFE as the seal material. Both the test and simulation results exhibited a quadratic leakage trend. The leakage rate first increased with increasing pressures, then made its peak of about 6 g/s in mid-pressure range, then started to drop to lower values of about 1.5 g/s as the pressure reached the maximum operating pressure. The proposed model was demonstrated to be a quick and handy tool to determine the design space of the EHD seals with minimal computational time. The simulation was converged in only 2 s. Yet, the proposed model could provide data regarding the leakage rate, seal deformation, pressure in the clearance, and stress on the seal, and thus, could serve as a design guide for the EHD seals.
Efficient Low-Fidelity Design Tool for Turbine-Integrated Wave Rotor Combustor
Authors: Jamshidnejad Mohammadhossein , Nalim M. Razi 
Published: October 2024

Abstract
Pressure-gain combustion (PGC) has attracted attention for its potential for jet propulsion without turbomachinery. However, the wave rotor combustor is a type of PGC device that may be particularly suited to achieve lower specific fuel consumption and higher specific power in gas turbines. Furthermore, instabilities inherent in conventional gas turbine combustion chambers may be avoided, especially with hydrogen fuel. Wave phenomena and non-steady flow play a key role in most PGC devices, including the wave rotor combustor. The computation of wave effects can be an obstacle to preliminary design of engine-integrated prototypes. In this article, a preliminary model has been put forth to allow low-cost, fast-response design algorithms for the wave rotor combustor integrated with a turbocharger to create a small gas turbine engine. Applications would include emergency power generators or integration in hybrid vehicles. A thermodynamic model of the combustor is used in an algorithm to match the characteristics of an available turbocharger. Simplified sizing relations are presented to assess compatibility and feasibility. It is found that when integrated with a turbocharger at a compressor pressure ratio of 2.2, a pressure gain of 1.6 is possible across the combustor, resulting in a cycle efficiency of 18.8 percent.
Effect of Non-Isothermal Conditions on Wind Patterns Near Isolated High-Rise Buildings
Authors: Najian Maede , Sharma Shivesh , Goudarzi Navid 
Published: October 2024

Abstract
Variations in temperature stratification conditions can change the pattern of airflow and the distribution of pollutants in urban environments. The present study explores the intricate dynamics of wind patterns within urban settings, focusing on their crucial role in evaluating wind power potential, managing air pollution, reducing urban heat island effects, ensuring urban air mobility safety, and improving pedestrian thermal comfort. It addresses the gap in understanding airflow, thermal conditions, and turbulence around buildings, emphasizing the impact of urban designs on wind behavior and temperature layers. Extending our previous research on airflow around high-rise structures, this work explores non-isothermal conditions using data and geometry from Tokyo Polytechnic University’s (TPU) wind tunnel facility. Utilizing advanced computational fluid dynamics (CFD) models, such as Unsteady Reynolds-averaged Navier-Stokes (URANS) in OpenFoam, this study predicts wind velocity, turbulence, and temperature distribution around a single isolated building. It further analyzes the effects of thermal stratification through spectral and proper orthogonal decomposition (POD), uncovering the significant influence of thermal state changes on turbulence kinetic energy. The findings indicate the complex interactions between thermal layers, urban airflow, and architectural configurations, providing valuable insights for urban planning and design. This knowledge is essential for better understanding air pollution distribution, enhancing distributed energy systems’ efficiency, and building energy performance in densely populated areas, offering a pathway to optimize microclimatic control and contribute to sustainable urban development.
Integrated CFD-VR Visualization of Indoor Displacement Ventilation
Authors: Alfred Ashish , Goudarzi Navid , Gulley Elijah , Kalatzis Apostolos 
Published: October 2024

Abstract
The utilization of modeling and simulation techniques is increasingly prevalent in engineering and research fields, particularly in energy efficiency and modeling. These tools offer cost-effective and flexible means of exploring diverse scenarios, including improvement in indoor thermal comfort and advancements in internal energy efficiency through the integration of advanced insulation or smart windows. However, significant challenges persist with current modeling and simulation tools, such as the requirement for specialized expertise, reliance on a wide array of complex software tools, lack of clarity for end-users, and issues related to software interoperability. This paper focuses on the integration of building information modeling with computational fluid dynamics (CFD) and virtual reality to enhance visualization in engineering applications. The project involves the construction of geometry using Autodesk Revit, setting up CFD simulation using Ansys Fluent, and exporting the simulation results for visualization in Unity. Challenges addressed such as software integration and extracting data for complicated post processing methods for visualization are mentioned. The outcomes reveal that integration of CFD with VR can help end-users to understand complex concepts of indoor airflow.
Simulation and Analysis of the Semi-Closed Solid Oxide CO2 Cycle (SOSCO2) for High Efficiency Ultra Low Carbon Power Generation
Authors: Martinelli Matteo , Campanari Stefano , Montinaro Dario , Martelli Emanuele 
Published: October 2024

Abstract
This work presents the simulation and techno-economic evaluation of the SOS-CO2 cycle, a novel hybrid cycle combining a pressurized solid oxide fuel cells with an oxy-turbine cycle. The cycle and its components are modelled and sized with the aim of assessing its performance and cost of electricity. A fuel cell design with high single-pass fuel utilization factor is considered. Sensitivity analyses on the fuel cell operating voltage and costs are performed to quantify their effects on the overall cycle performance. The results show that the cycle is expected to achieve outstanding net electric efficiency values, in the range 65.7%–69.3%, while capturing 95% of the generated CO2. The resulting specific CO2 emissions are as low as 15.9 gCO2/kWh. The cost of electricity is expected to be in the range 133 vs. 128.4 €/MWh (depending on the fuel cell voltage), a value competitive with the best available technologies for CO2 capture and storage.
Estimating the Reduction of Socioeconomic Inequalities for a More Physically Active Society: A Cross-Sectional Study of the European Union Country Members
Authors: Moreno-Llamas Antonio , De la Cruz-Sánchez Ernesto , García-Mayor Jesús 
Published: October 2024

Background: Socioeconomic inequalities significantly impact the accessibility of resources necessary for physical activity, thereby influencing overall physical activity levels and contributing to broader health disparities. Nevertheless, evidence is lacking on quantifying the increase of people who would be physically active through reducing inequalities by a higher socioeconomic position. Methods: We conducted secondary data analysis on the 2017 cross-sectional survey of the European Union’s population aged ≥18 years (n = 27,538). By estimating socioeconomic status percentages and odds ratios between socioeconomic status (education, occupational social class, and economic issues) and physical activity, we calculated age-standardized Prevented Fraction for Population and the total number of individuals that would meet physical activity guidelines by a higher socioeconomic status (eg, from low to middle or high socioeconomic status), along with scenarios of reduced socioeconomic disparities, controlling for age, gender, place of residence, and marital status. Results: A higher socioeconomic status could promote physical activity for a total of 93.0 (84.5–101.8) million people through university education, 28.5 million via high-ranked occupations (24.6–32.8), and 137.9 (129.5–146.2) million by less economic issues (compared with primary education, low-manual occupations, and having economic issues most of the time, respectively)—equivalent to 35.46%, 14.49%, and 55.42% of the Prevented Fraction for Population. Reducing socioeconomic inequalities by 50% could raise these estimations to 148.1 million (134.0–162.8) through education, 43.5 million (37.5–50.3) through occupation, and 223.6 million (209.3–237.8) through less economic issues. Conclusions: Enhancing access to university education, high-ranked occupations, and income impacts physical activity population levels in the European Union.
Acute and Transient Match-Related Fatigue in University Female Footballers
Authors: Hearn Andrew N. , Parker John K. , Hicks Kirsty M. , Fernandes John F.T. 
Published: October 2024

This study aimed to examine the acute fatigue response experienced by female footballers during and after match-play. Twenty university footballers completed three trials of a countermovement jump on a force platform pre- and post-match-play (35 observations). External and internal loads were recorded during match-play via global positioning systems (GPS) and heart rate (HR), respectively. Match-play loads were split into thirds and analyzed via linear mixed model. Pre- and postjump metrics (n = 16) were analyzed using a paired samples t test. Significant decrements were observed between the first and final third for all external load metrics apart from sprint distance and accelerations (p > .05). Relative concentric peak force (p = .035) was significantly increased postmatch, while a reduction was observed for relative concentric mean power (p = .034). The remaining 14 metrics did not display any significant changes (p > .05). The stability of countermovement jump (CMJ) performance pre- to postmatch alongside the reductions within match support the notion of transient fatigue. Moreover, coaches can use this data (i.e., transient fatigue) to inform tactics in female football (i.e., substitutions) and conditioning regimes.