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Realization of multilocal gradient-doping PCN by alkali metal ion sustained release capsules for enhanced photocatalytic water splitting

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APPLIED CATALYSIS B-ENVIRONMENT AND ENERGY 2023年第1期339卷

作者： Yan, Jiawei Fang, Wenjian Wei, Zhidong Chi, Jiasheng Chen, Mingxia Jiang, Zhi Jiang, Kun Shen, Shaohua Shangguan, Wenfeng Shanghai Jiao Tong Univ Res Ctr Combust & Environm Technol Shanghai 200240 Peoples R China Shanghai Jiao Tong Univ Coll Smart Energy Shanghai 200240 Peoples R China Yangzhou Univ Sch Elect & Energy Power Engn Yangzhou 225002 Peoples R China Shanghai Jiao Tong Univ Inst Fuel Cells Shanghai 200240 Peoples R China Xi An Jiao Tong Univ Int Res Ctr Renewable Energy State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China

The gradient-doping technique has been widely applied to induce an oriented built-in electric-field. However, it is still not efficient enough for charge mobility especially for particulate semiconductors, as the field is primarily in one direction from inner to surface. Here, we propose a multilocal gradient-doping technique that a nanocapsule is designed to store dopants and then release them into semiconductors nonuniformly. As an illustration, scattered pyrochlore-type K2Ta2O6 nanoparticles have been validated the capability of storing and releasing K+, which subsequently diffuse into the substrate PCN. Multi point-radiative gradient in K+ concentration, confined within the K2Ta2O6's vicinity, will construct several 3D potential wells which can not only accelerate the carrier separation but also offer more migration channels for both photo-induced electrons and holes to the surface. Consequently, the multilocal K+ gradient-doping PCN shows the longest carriers' lifetime and highest AQY (similar to 21.8% at 400 nm) compared with the other uniformly doping techniques.

关键词： Doping Photocatalysis Ion diffusion Potential well Charge transfer

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Experiment and Kinetics Studies on Ash Fusion Characteristics of Biomass/Coal Mixtures during Combustion

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ENERGY & FUELS 2019年第10期33卷 10317-10323页

作者： Lv, Yuan Niu, Yanqing Liang, Yang Liu, Siqi Wang, Denghui Hui, Shi'en Xi An Jiao Tong Univ Sch Energy & Power Engn Dept Thermal Engn State Key Lab Multiphase Flow Power Engn Xian 710049 Shaanxi Peoples R China

Cofiring of biomass and coal significantly reduces carbon emissions and alleviates ash-related problems of biomass. This study investigates the effect of the biomass/coal blending ratio on ash fusion characteristics through the ash fusion test, X-ray fluorescence, and X-ray diffractometry. Meanwhile, kinetic analysis of the ash fusion process was conducted to provide a new method and reading benchmark for obtaining precise and repeatable initial deformation temperature (IDT). Results showed that the IDT decreased with the increase of the biomass blending ratio because of the decrease of alumina content and the increase of potassium content. When the biomass blending ratio increased, the content of orthoclase and diopside at the low melting point increased, while the content of andalusite, quartz, and anhydrite at the high melting point decreased, resulting in the decline of IDT. Kinetic analysis indicated that with increasing biomass blending ratio, the activation energy of ash fusion reaction decreased, which is the essential reason for the decrease of IDT. Coal ash had an activation energy of 1144.67 ***(-1), while it decreased to 145.89 ***(-1) with an increased biomass blending ratio to 100%. Compared with the larger error (up to 60 degrees C) caused by visual reading on the morphological change of the triangle ash cone, kinetics calculation gave precise prediction with less error between 2 and 7 degrees C. As an optimal recommendation, the average shrinkage rate of height at 41% could be used as a reading benchmark for the determination of IDT in further study.

关键词： Potassium Activation energy Reaction products Biomass Coal

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Numerical study on thermal deformation behaviors of the single subassembly in sodium-cooled fast reactors based on Euler-Bernoulli beam theory

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NUCLEAR engineering AND DESIGN 2019年第Apr.期345卷 28-39页

作者： Ma, Zhenhui Ma, Zehua Wu, Yingwei Wang, Mingjun Su, G. H. Xi An Jiao Tong Univ Sch Nucl Sci & Technol State Key Lab Multiphase Flow Power Engn Xian 710049 Shaanxi Peoples R China

Due to the special geometry and compact arrangement of subassemblies in the sodium-cooled fast reactor, thermal deformation of the assemblies are easily triggered by uneven temperature distribution in the reactor core, which is negative for reactor safety. Therefore, it is necessary for researchers and engineers to conduct quantitative analysis towards thermal deformation behaviors of subassemblies, and furthermore, give reliable evaluation results on aftermath of the assembly thermal deformation. In the present study, thermal deformation analysis code FADAC, which was developed based on Euler-Bernoulli beam theory, was applied to make numerical investigation for thermal deformation behaviors of a single subassembly in sodium-cooled fast reactor. In order to preliminarily assess the capacity for thermal deformation, different temperature gradient conditions were considered and analyzed in detail for free bowing of the subassembly, furthermore, with the aid of numerical analysis for thermal axial forces and thermal bending moments, axial displacements and deflections were calculated finally. Besides, in order to predict the comprehensive results of the assembly deformation under both thermal load and mechanical load, restrained bowing were also analyzed for different temperature conditions. All of the simulation results were in good accordance with the experimental data. The present numerical research is of great significance to assembly deformation research in the sodium-cooled fast reactor, and will surely lay a solid foundation for deformation analysis towards multi-subassemblies.

关键词： Sodium-cooled fast reactor Thermal deformation Subassembly Deflection

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Gas-liquid flow seal in the smooth annulus during plunger lifting process in gas wells

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JOURNAL OF NATURAL GAS SCIENCE AND engineering 2021年 95卷 104195-104195页

作者： Zhao, Kunpeng Mu, Lijun Tian, Wei Bai, Bofeng Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China PetroChina Changqing Oilfield Branch Co Oil & Gas Technol Res Inst Xian 710018 Peoples R China

Liquid leakage and gas slippage through the annulus between an upward moving plunger and vertical tubing significantly reduce the uploading efficiency of the accumulated liquid during plunger lifting in gas wells. Understanding the characteristics of gas-liquid two-phase flow in the annulus during plunger lifting process is crucial to enhance the fluid seal and to improve the plunger lift technology, but investigations of this important issue in literature is extremely limited. In this paper, we employ VOF-CFD numerical approach to provide a computationally efficient flow model to account for interactions between loading liquid, producing gas and the lifting plunger in gas wells. Results from simulations are consistent with both the in-door experimental data and field observations, thus allowing us to reproduce detailed characteristics of gas-liquid flow in the annulus during plunger lifting process. The actual conditions in gas wells are simulated, in which the plunger upward velocity is ranged in 2 m/s < vp < 10 m/s and the gas density is ranged in 13.9 kg/m3 < rho g < 80.9 kg/m3. Numerical results indicate that with the plunger lifting velocity increasing, the liquid leakage flow rate increases, the gas slippage flow rate decreases, and the gas-liquid countercurrent annular flow in the annular space transforms to the cocurrent upward annular flow. Based on the interface instability analysis, we reveal the mechanism of gasliquid flow seal in the annulus which is promoted by the droplet entrainment and is weakened by the droplet deposition. A simple dimensionless coefficient is proposed to evaluate the uploading efficiency of the accumulated liquids by the plunger in gas wells, the bigger value of the coefficient represents the better performance of liquid sealing during plunger lifting process. The optimal diameter ratio between the plunger and tube (0.96), as well as the optimal diameter-length ratio of the plunger (0.13) are proposed to improve the plunger lift

关键词： Plunger lift Gas-liquid flow seal Smooth annulus Gas well deliquification

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Effects of FGR and Changeable Combustion Parameters and Coal/Char Properties on the Formation of Ultrafine PMs during Pulverized Coal Char Combustion under Various O2/N2 and O2/CO2 Atmospheres

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COMBUSTION SCIENCE AND TECHNOLOGY 2019年第10期191卷 1898-1915页

作者： Niu, Yanqing Liu, Siqi Gong, Yanhao Liang, Yang Zhang, Xiao Yan, Bokang Hui, Shi'en Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Sch Energy & Power Engn Dept Thermal Engn Xian 710049 Shaanxi Peoples R China

Aiming at the wide adoption of flue gas recirculation (FGR) in coal power plants for NOx removal and CO2 capture, and the imperfect removal of particulate matters (PMs), especially ultrafine PMs which constitute most of the particles discharged into atmosphere, consequently causing atmospheric haze and diseases, the effects of FGR and combustion parameters, and coal/char properties on PMs formation were therefore studied under different O-2/N-2 and O-2/CO2 atmospheres using a self-developed kinetic model. Modeling results showed that the inclusion vaporization rate and ratio had a dominant effect on PMs number density and size respectively. At the same level of oxygen content, smaller ultrafine PMs were generated under O-2/CO2 than those generated under O-2/N-2. Increasing oxygen content facilitated the formation of larger and fewer PMs. The PMs size in 27O(2)/73N(2) shows the biggest, followed by that in 36O(2)/64CO(2), 27O(2)/73CO(2), 21O(2)/79N(2), and 21O(2)/79CO(2) in turn. Compared to without FGR, FGR decreased the size of ultrafine PMs and increased the number, thus hindering PMs removal. With increasing FGR ratio, which had the most significant effect, the ultrafine PMs size decreased due to dilution effect. With increasing dust removal efficiency, the ultrafine PMs size decreased initially and then increased, peaking close to 100% of dust removal efficiency. The effect of recirculated particle size was negligible. Sensitivity analyses revealed that furnace gas temperature, inclusion size, and char density were the most influential factors on inclusion vaporization and PMs formation. The effects of CO/CO2 ratio, char load, coal ash content, and inclusion content were positive, while the effects of char density and ash content, inclusion size, and moisture were negative. High furnace temperature increased vaporization, but significantly decreased the PMs size. The number density of ultrafine PMs followed mass conservation. These results provide meaningful gui

关键词： Particulate matter flue gas recirculation char combustion oxy-fuel kinetics

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PREFACE: SPECIAL ISSUE FOR THE 2ND INTERNATIONAL SYMPOSIUM ON THERMAL-FLUID DYNAMICS (ISTFD2021)

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Heat Transfer Research 2022年第8期53卷 V-VI页

作者： Cheng, Lixin Bai, Bofeng Guo, Zhixiong School of Energy and Power Engineering Beijing University of Technology Beijing100124 China Department of Engineering and Mathematics Sheffield Hallam University SheffieldS1 1WB United Kingdom State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China Department of Mechanical and Aerospace Engineering Rutgers The State University of New Jersey PiscatawayNJ08854 United States

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Numerical study on the thermal stratification characteristics of AP1000 pressurizer surge line

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ANNALS OF NUCLEAR ENERGY 2019年第Aug.期130卷 8-19页

作者： Wang, Mingjun Feng, Tangtao Fang, Di Hou, Ting Tian, Wenxi Su, G. H. Qiu, Suizheng Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Dept Nucl Sci & Technol Xian 710049 Shaanxi Peoples R China

The surge line is implemented to connect the pressurizer with reactor cooling system in Pressurized Water Reactor (PWR). The integrity of surge line plays an important role for reactor safe operation. In the literatures, much work has been contributed to the thermal hydraulic characteristics and reliability research on traditional pressurizer surge line. For the advanced Generation-III PWR, the AP1000 adopts a new spiral-shaped pressurizer surge line concept. In this paper, the three-dimensional thermal hydraulic transient characteristics in AP1000 pressurizer surge line are studied and the formation mechanism of surge line thermal stratification phenomenon is investigated. The variation of maximum temperature difference with time in the whole surge line is achieved. Results show that the thermal stratification is becoming weaker along the flow direction and the most dangerous region is the entrance of horizontal position. The thermal stratification affected by the circumference effect is not significant during the surge line thermal fatigue analysis. In addition, through the comparison of temperature distribution in pressurizer surge line between the traditional PWR and AP1000, it can be seen that the AP1000 pressurizer surge line has smaller temperature difference at the corresponding position with shorter period. The new design concept of AP1000 surge line brings a great advantage to reduce the hazard causing by the thermal stratification. This work provides a valuable guideline for the AP1000 pressurizer surge line fatigue assessment. (C) 2019 Elsevier Ltd. All rights reserved.

关键词： Thermal stratification Pressurizer surge line AP1000 CFD

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Study on the synthesis of poly(pyrrole methane)s with the hydroxyl in different substituent position and their selective adsorption for Pb²⁺

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CHEMICAL engineering JOURNAL 2019年 361卷 528-537页

作者： Liu, Yunpeng Zhang, Wenlong Zhao, Chengcheng Wang, Hui Chen, Jie Yang, Liu Feng, Jiangtao Yan, Wei Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Dept Environm Sci & Engn Xian 710049 Shaanxi Peoples R China

Two poly(pyrrole methane)s (PPD2HBA and PPD3HBA) were successfully synthesized, with focusing on the effect of steric hindrance on the selective adsorption of heavy metal ions. The structure and morphology of PPD2HBA and PPD3HBA were characterized by FT-IR, UV-Vis, H-1 NMR, BET, SEM, XPS and Zeta potential. The influencing factors of the Pb2+-adsorption onto the two adsorbents were systematically studied, including various solution conditions and co-existing metal ions effect. These results demonstrated that the two adsorbents showed slightly different adsorption behaviors. The maximum adsorption capacities of Pb2+ onto PPD2HBA and PPD3HBA were 41.35 and 32.10 mg.g(-1) at pH= 6.0 and 318 K, respectively. The crucial steric hindrance verified by FT-IR and XPS before and after Pb2+ adsorption, showed better consistence in PPD2HBA with the size and shape of the hydrated Pb2+ than that in PPD3HBA, which can be further supported by the adsorption property of PPD4HBA. In addition, the effect of the co-existing metal ions of Pb2+ onto PPD2HBA and PPD3HBA could be testified by the HSBA theory. The proposed adsorption mechanism in this paper was of remarkable potential for the design of new adsorbent to selectively adsorb heavy metal ions from wastewater.

关键词： Poly(pyrrole methane) Steric hindrance HASB theory Selective adsorption Heavy metal ions

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An experimental investigation of composite phase change materials of ternary nitrate and expanded graphite for medium-temperature thermal energy storage

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SOLAR ENERGY 2020年 195卷 573-580页

作者： Lu, Wei Liu, Guizhi Xiong, Zhibo Wu, Zhigen Zhang, Guanhua Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai 200093 Peoples R China Shanghai Key Lab Multiphase Flow & Heat Transfer Shanghai 200093 Peoples R China Tongji Univ State Key Lab Pollut Control & Resource Reuse Shanghai 200092 Peoples R China Shanghai Inst Pollut Control & Ecol Secur Shanghai 200092 Peoples R China

Utilization of KNO3-LiNO3-Ca(NO3)(2)/expanded graphite (EG) as composite phase change materials (PCMs) for medium-temperature thermal energy storage was investigated in this paper. The thermo-physical properties of KNO3-LiNO3-Ca(NO3)(2) with different proportions were investigated. EG was employed as an additive to enhance thermal conductivity of PCMs as it has high thermal conductivity and excellent thermo-chemical stability. Thermo-physical parameters such as phase transition temperature, latent heat of fusion, thermal conductivity and decomposition temperature were measured experimentally. The results showed that the phase transition temperature of this ternary nitrate (60.2 wt% KNO3-29.9 wt% LiNO3-9.9 wt% Ca(NO3)(2)) is lower than that of Solar Salt and Hitec Salt. The composites with more EG have higher thermal conductivity. However, the addition of EG reduces their decomposition temperature. Furthermore, the corrosion experiments with six types of metal samples embedded in liquid ternary nitrate at 480 degrees C for 1500 h were delivered to investigate their chemical stability. Moreover, the PCMs have good long-term high temperature stability during the process. The results of this work confirmed the great potentials of KNO3-LiNO3-Ca(NO3)(2)/EG as composite PCMs that can be applied for industrial waste heat energy recovery applications, the solar power generation system and medium-temperature thermal energy storage.

关键词： Phase change materials Expanded graphite Thermo-physical property Thermal stability

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Effects of biomass particles size and shape on combustion process in the swirl-stabilized burner reactor: CFD and machine learning approach

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BIOMASS & BIOENERGY 2023年第1期174卷

作者： Milicevic, Aleksandar Belosevic, Srdan Zarkovic, Mileta Tomanovic, Ivan Crnomarkovic, Nenad Stojanovica, Andrijana Stuparc, Goran Deng, Lei Che, Defu Univ Belgrade VINCA Inst Nucl Sci Natl Inst Republ Serbia Dept Thermal Engn & Energy Mike Petrov Alasa 12-14POB 52211001 Vinca Belgrade 11351 Serbia Univ Belgrade Sch Elect Engn Bulevar Kralja Aleksandra 73 Belgrade 11020 Serbia Univ Belgrade Fac Mech Engn Kraljice Marije 16 Belgrade 35 Serbia Xi An Jiao Tong Univ Sch Energy & Power Engn State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China

When planning the development of the energy sector, significant attention is given to the energy from the renewable sources, amongst which the biomass has an important role. Computational fluid mechanics and machine learning models are the powerful and efficient tools which allow the analysis of various heat and mass transfer phenomena in energy facilities. In this study, the in-house developed CFD code and machine learning models (Random Forest, Gradient Boosting and Artificial Neural Network) for predicting the biomass trajectories, particle mass burnout and residence time in a swirl burner reactor are presented. Pulverized biomass combustion cases (fine straw, pinewood and switch grass) with various mean diameters (ranging between 60 and 650 mu m) and different shape factors (within the range 0-1) are considered. The results of numerical simulations revealed a noticeably nonlinear dependence between the input values (particle types, sizes and shapes) and the output values (particle trajectories, mass burnout and residence time), mostly due to the complex swirling flow in the reactor. For particles with the mean diameters within the ranges considered, the mass burnout of particles generally decreases as the biomass particle shape factor increases. The residence time of pulverized biomass in the reactor shows in most cases a decreasing trend as the particle shape factor increases. Artificial Neural Network showed the best predictions for both particle mass burnout (RMSE = 0.083 and R2 = 0.937) and particle residence time (RMSE = 1.145 s and R2 = 0.900), providing the reliable assessment of these important indicators in the combustion process.

关键词： Biomass combustion Particle size Shape factor CFD Artificial intelligence Swirl burner reactor

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