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SSRN 2023年

作者： Dai, Xiaoyu Xu, Qiang Yang, Chenyu Su, Xiaobin Chang, Liang Guo, Liejin State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China Shanghai Institute of Satellite Engineering Shanghai201109 China

The mixed-flow multiphase pump may experience pressurization deterioration due to the high Gas Volume Fraction, resulting in pressurization failure and posing a threat to the pressurization unit's safety. In this paper, a three-stage mixed-flow multiphase pump with closed impeller structure is designed and developed. The hydraulic characteristics and pressurization deterioration mechanism of the multiphase pump were investigated at various rotational speeds and inlet conditions using the experiment and simulation. As the liquid flow rate rises, the multiphase pump experiences a 'three-stage' downward trend in pressurization. The first booster stage has a greater capacity for pressurizing the liquid phase. The gas-liquid pressurization exhibits a wave-shaped downward trend due to significant deterioration in stage-wise pressurization when the liquid flow rate is low. Once the Inlet Gas Volume Fraction reaches the initial critical Gas Volume Fraction, the gas aggregates on the impeller’s suction surface is removed at the impeller outlet, creating an annular air mass. When this mass of air meets the fluid behind it, it creates a chaotic vortex that absorbs the fluids' kinetic energy. As a result, the first booster stage experiences a significant reduction in its pressurization ability, causing an abrupt decrease in the pressurization curve. © 2023, The Authors. All rights reserved.

关键词： Computational fluid dynamics

Supercritical Co2 -Promoted Degradation of Polystyrene to Aromatic Oils with Nio@C Catalyst

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SSRN 2024年

作者： Liu, Yanbing Shi, Jinwen Zhuang, Zitong Kang, Xing Mao, Liuhao Li, Yi Jin, Hui Zhao, Qiuyang Guo, Liejin International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University 28 West Xianning Road Shaanxi Xi’an710049 China

Exploring new system for chemical recycling of plastic is an effective way to convert plastic waste into energy. Herein, the use of supercritical CO2 (Sc-CO2) to promote the catalytic degradation of polystyrene (PS) with high yield of aromatic oils was proposed. Sc-CO2 provided a homogeneous environment for the reaction, which not only facilitated the swelling of PS, but also inhibited the formation of coke, beneficial for the degradation of PS to aromatic oils. Importantly, CO2 was be consumed as an oxidant to generate new product and reduce greenhouse gas emission. The doped carbon material in NiO, which was stable in Sc-CO2 and had a simple preparation process, enriched the porous structure and increased the acidic sites, thus improving the catalytic activity. Under the co-action of Sc-CO2 and NiO@C, the yield of aromatic oils produced from PS was up to 89.3 ± 0.6 wt% at 300oC with a reaction time of 2 h and a catalyst loading amount of 10 wt%. Moreover, the NiO@C catalyst were used for three cycles without obvious change in the catalytic performance. The efficient catalytic degradation of PS to aromatic oils by Sc-CO2 promoted NiO@C catalysis provides a potential route for simultaneously recycling plastic and sequestering carbon. © 2024, The Authors. All rights reserved.

关键词： Carbon dioxide

Uncertainty Analysis of FLiNaK Thermophysical Properties on Convective Heat Transfer Characteristics in Circular Tube

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SSRN 2024年

作者： Li, Haoyang Ding, Ming Guo, Zehua Heilongjiang Provincial Key Laboratory of Nuclear Power System & Equipment Harbin Engineering University Harbin150001 China State Key Laboratory of Multiphase Flow in Power Engineering Shaanxi Key Laboratory of Advanced Nuclear Energy and Technology School of Nuclear Science and Technology Xi’an Jiaotong University Xi’an710049 China

Molten salts have attracted a spate of quantity of interest in energy and chemistry fields due to their large volumetric capacity, and thermodynamic stability at elevated temperatures. However, on account of immature technology and measurement methods, the physical properties of molten salts, such as dynamic viscosity, thermal conductivity, specific heat capacity and density, have large uncertainties, which will be transported with CFD simulation equations and experimental processes. While present investigations normally focus on thermal-hydraulic characteristics, disregarding the impact of uncertainty on reactor safety. Thus, this paper firstly performs a numerical simulation to investigate the thermal-hydraulic performance of FLiNaK (LiF-NaF-KF, 46.5–11.5–42 mol%) in a horizontal tube using a computational fluid dynamic (CFD) tool, STAR-CCM+, and validates the applicability of classic correlations for molten salt. Based on this, an uncertainty analysis methodology, polynomial chaos expansion (PCE) is carried out to analyze the uncertainty that contributes to the heat transfer characteristic. Three primary physical properties of molten salt are considered as the input parameter, tensor product quadrature nodes are employed in this work to calculate the representative sample points to alleviate the computational expense. The contributions of each parameter to heat transfer are also analyzed by the sobol composition method. Finally, deviations in the experimental post-processing (compared with classic correlations) caused by discrepancies in the selected properties from the actual properties due to uncertainty are also taken into account. The result shows the thermal-hydraulic performance can be nicely modeled and simulated results are in good agreement with widely used correlations. Meanwhile, the consequences of uncertainty analysis suggest that the polynomial chaos expansion methodology is robust and neoteric for molten salt analysis. © 2024, The Authors. All righ

关键词： Uncertainty analysis

Digital twin modeling and fault diagnosis on the feedwater pump system of thermal power plant

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Digital twin modeling and fault diagnosis on the feedwater p...

Digital Twins and Parallel Intelligence (DTPI), IEEE International Conference on

作者： Yugang Liu Chi Luo Chen Chen Zhu Wang Ming Liu Clean Combustion and Flue Gas Purification Key Laboratory of Sichuan Province Dongfang Boiler Co. Ltd Chengdu China State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an China

ISBN: (数字)9798350349252

ISBN: (纸本)9798350349269

The high penetration of renewable energy introduces increased volatility into the power system, presenting more challenging peak shaving and frequency modulation missions for thermal power plants that serve as schedulable power sources within the system. Frequent load cycling place higher demands on the operation stability of core power plant equipment and introduce additional safety risks. As the core system of the power cycle, the operational reliability and energy efficiency of the feedwater pump system (FPS) are crucial. Therefore, this paper focuses on the core equipment and parameters of the FPS, developing a digital twin model based on mechanism modeling method and neural network data-driven modeling method. By comparing the mean absolute error, root mean square error, and coefficient of determination of simulation parameters of different modeling methods, digital twin parameters with higher simulation accuracy were obtained. Utilizing these predicted parameters, an FPS fault diagnosis model (FFDM) for the FPS was developed. By calculating comprehensive deviation degree and the contribution of each parameter, fault early warning and source tracing were achieved, providing guidance for the closed-loop control.

关键词： Fault diagnosis Data-driven modeling Neural networks Predictive models power system stability Energy efficiency Digital twins Safety power system reliability power generation

Understanding the Reversal Dilution Effect of the Species Sampling in the Negative Temperature Coefficient Region

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SSRN 2023年

作者： Wu, Yingtao Mai, Zhaoming Rao, Boxuan Liu, Jie Tang, Chenglong Huang, Zuohua State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi'An710049 China Department of Power Mechanical Engineering Beijing Jiaotong University Beijing100044 China

Species sampling during fuel autoignition can provide valuable insights in studying the chemical kinetic mechanism. Various species sampling techniques have been developed for speciation quantification in different reactors. However, unavoidable dilution in the physical sampling brings uncertainty to the measurements, particularly in the negative temperature coefficient (NTC) region where the effect of dilution remains unclear. To address this issue and improve measurement accuracy, numerical species samplings during the autoignition of n-butane mixture were studied in a rapid compression machine reactor. Results show that greater fuel consumption and intermediate generation were observed in regions with lower temperatures instead of the hot core zone. Therefore, the dilution effect on the sampling results is reversed inside the NTC region. Furthermore, results from two typical sampling methods were compared with the target core profiles to determine their uncertainties. Lastly, the feasibility of applying dilution ratio calibration on the sampling results in the NTC region was tested, which indicates the necessity of considering the NTC effect, particularly for intermediates with low concentrations. Alternatively, increasing the sampling duration of the fast-sampling method effectively reduces the uncertainty of species concentration and enhances the robustness of mechanism validation regardless of the NTC behavior. © 2023, The Authors. All rights reserved.

关键词： Temperature

Study on the Three-Dimensional flow Control of Two-Phase flow Around a Cylinder by an Attached Cylinder

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SSRN 2023年

作者： Xia, Yizhan Hu, Yu Huang, Shengxian Wang, Ying Shanghai key laboratory of multiphase flow and heat transfer of power engineering School of Energy and Power Engineering University of Shanghai for Science and Technology Shanghai China

Enhancing the separation of flow, shedding of vortices, and sediment deposition around blunt bodies, particularly in cylindrical flows within the realm of ocean engineering, emerges as a pivotal safety factor. This study delves into the control of two-phase flow encircling a cylinder using an affixed cylinder under three-dimensional real ocean conditions. Employing the SST turbulence model, a two-dimensional incompressible RANS numerical simulation is performed. Initially, the influence of varying gap ratios between the auxiliary small cylinder and the main cylinder is scrutinized. Subsequently, the impact of attached small cylinders on the flow field surrounding the main cylinder is examined under different particle characteristics. Lastly, employing the UDF function, four small cylinders exhibiting distinct vibration modes are defined, and the numerical simulation investigates the effects of Grain flow on particle flow and distribution in the wake region of the main cylinder. © 2023, The Authors. All rights reserved.

关键词： Cylinders (shapes)

Room-temperature photodeposition of conformal transition metal based cocatalysts on BiVO4 for enhanced photoelectrochemical water splitting

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Nano Research 2020年第1期13卷 231-237页

作者： Lu Wang Tao Zhang Jinzhan Su Liejin Guo International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power EngineeringSchool of Energy&Power EngineeringXi’an Jiaotong UniversityXi’an710049China

Photoelectrochemical(PEC)water splitting using semiconductors offers a promising way to convert renewable solar energy to clean hydrogen ***,due to the sluggish reaction kinetics of water oxidation,significant charge recombination occurred at the photoanode/electrolyte interface and cause decrease of its PEC *** reduce the surface recombination,we deposit different transition metal complexes on BiVO4 nanocone arrays by a versatile light driven in-situ two electrode photodeposition approach without applied *** cobalt phosphate“Co-Pi”,nickel borate“Ni-Bi”and manganese phosphate“Mn-Pi”complexes were deposited on BiVO4 nanocone arrays to form core-shell structure photoanode,all of which lead to enhanced photoelectrochemical *** photocurrent of the Co-Pi/BiVO4 photoanode under front-side illumination for 5 min is increased by 4 folds comparing to that of bare BiVO4 photoanode at 0.6 V ***,reaching a hole transfer efficiency as high as 94.5%at 1.23 V *** proposed photodeposition strategy is simple and efficient,and can be extended to deposite cocatalyst on other semiconductors with a valence band edge located at a potential more positive than the oxidation potential of transition metal ion in the cocatalyst.

关键词： bismuth vanadate photoelectrochemcial water splitting conformal photodeposition cocatalyst

Electron-Deficient Zn-N_(6) Configuration Enabling Polymeric Carbon Nitride for Visible-Light Photocatalytic Overall Water Splitting

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Nano-Micro Letters 2022年第12期14卷 602-616页

作者： Daming Zhao Yiqing Wang Chung-Li Dong Fanqi Meng Yu-Cheng Huang Qinghua Zhang Lin Gu Lan Liu Shaohua Shen International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power EngineeringXi’an Jiaotong UniversityXi’an 710049People’s Republic of China State Key Laboratory of Rare Earth Resource Utilization Changchun Institute of Applied ChemistryChinese Academy of SciencesChangchun 130022People’s Republic of China Department of Physics Tamkang UniversityNew Taipei City 25137TaiwanPeople’s Republic of China Beijing National Laboratory for Condensed Matter Physics Institute of PhysicsChinese Academy of SciencesBeijing 100190People’s Republic of China

Despite of suitable band structures for harvesting solar light and driving water redox reactions,polymeric carbon nitride(PCN)has suffered from poor charge transfer ability and sluggish surface reaction kinetics,which limit its photocatalytic activity for water ***,atomically dispersed Zn-coordinated three-dimensional(3D)sponge-like PCN(Zn-PCN)is synthesized through a novel intermediate coordination *** characterizations and theoretical calculations well evidence that Zn single atoms are coordinated and stabilized on PCN in the form of Zn-N_(6) configura-tion featured with an electron-deficient *** an electronic configuration has been demonstrated contributive to promoted electron excitation,accelerated charge separation and transfer as well as reduced water redox *** benefited from the abundant surface active sites derived from the 3D porous structure,Zn-PCN realizes visible-light photocatalysis for overall water splitting with H_(2) and O_(2) simultaneously evolved at a stoichiometric ratio of 2:*** work brings new insights into the design of novel single-atom photocatalysts by deepening the understanding of electronic configurations and reactive sites favorable to excellent photocatalysis for water splitting and related solar energy conversion reactions.

关键词： Zn single atoms Polymeric carbon nitride Overall water splitting Photocatalysis

Thermodynamic optimization of closed air Brayton cycle and air-ORC combined cycle

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Thermodynamic optimization of closed air Brayton cycle and a...

International Conference on power engineering 2021, ICOPE 2021

作者： Qian, Yiran Zhang, Zhuohua Yi, Jingwei Chen, Weixiong Liu, Ming Yan, Junjie State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China Nuclear Power Institute of China Chengdu610213 China

In order to improve the flexibility and adaptability of small mobile nuclear power systems, air is considered as an optional working fluid of nuclear Brayton cycle system. It can avoid the shortage of working fluid under extreme conditions, and ensure the system operation with tight working fluid supply. In this study, simple regenerative cycle (SRC), intercooling regenerative cycle (IRC) and corresponding air-ORC combined cycle (SRCC and IRCC) are proposed and modeled. Thermodynamic analysis of key parameters is conducted. Genetic algorithm (GA) is applied for multi-parameter optimization to achieve the maximum cycle efficiency. With the increase of pressure ratio (PR), the efficiency of SRC increases firstly and then decreases. Pressure ratio corresponding to the maximum cycle efficiency increases gradually with turbine inlet temperature. The efficiency of IRC is slightly lower than that of SRC in low pressure ratio region, but IRC maintains a higher efficiency in high pressure ratio region. For SRCC, isobutane has the best performance among three selected organic working fluids. The multi-parameter optimization result indicates that the IRCC has lower cycle efficiency comparing with SRCC, and SRCC shows the optimal performance among the four configurations. © 2021 The Japan Society of Mechanical Engineers.

关键词： Efficiency

Computational homogenization of thermomechanical properties for Fully Ceramic Microencapsulated fuel with 3D printed SiC matrix

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Annals of Nuclear Energy 2025年 222卷

作者： Chen, Yiwen Lu, Qi Liu, Changwen Li, Wei Zhang, Dalin Su, G.H. State Key Laboratory of Multiphase Flow in Power Engineering Shaanxi Key Laboratory of Advanced Nuclear Energy and Technology School of Nuclear Science and Technology Xi'an Jiaotong University Xi'an710049 China Science and Technology on Reactor System Design Technology Laboratory Nuclear Power Institute of China Chengdu61213 China State Key Laboratory for Strength and Vibration of Mechanical Structures Xi'an Jiaotong University Xi'an710049 China

Fully Ceramic Microencapsulated (FCM) fuel, fabricated using 3D printing technology, incorporates traditional Tristructural-Isotropic (TRISO) fuel particles embedded within a 3D-printed SiC matrix. This fuel type shows great potential for compact, high-temperature nuclear reactors. However, comprehensive performance analysis remains challenging due to the multilayered structure, complex material properties, and the irradiation behavior of numerous TRISO particles within the matrix. To address these challenges, this study aims to apply finite element (FE)-based computational homogenization to evaluate the fuel's thermomechanical properties. First, a detailed finite element analysis (FEA) of a single TRISO particle's performance was conducted, focusing primarily on the Buffer-IPyC gap size change during irradiation, a critical factor influencing the fuel's thermal performance. Second, the homogenization of a single TRISO particle was performed using FEA, accounting for the changes in the Buffer-IPyC gap size. Finally, homogenized TRISO particles were randomly distributed and perfectly bonded within a 3D-printed SiC matrix to form a Representative Volume Element (RVE). The FE homogenization of the RVE was then conducted to derive the effective thermomechanical properties of the FCM fuel. The packing fraction of TRISO particles in the matrix ranged from 10 % to 50 %, with temperature and burnup conditions spanning 800–1600 K and 0–16 % FIMA, respectively. Results show that irradiation significantly affects the effective properties of the fuel, though this impact diminishes as burnup increases. Additionally, the effective thermal conductivity of the FCM fuel decreases with increasing TRISO packing fraction, assuming the thermal conductivity of the SiC matrix exceeds that of TRISO particles. This study provides a valuable reference for the design and optimization of FCM fuel for future nuclear applications. © 2025 Elsevier Ltd

关键词： Thermal conductivity of solids