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Liutex identification on hairpin vortex structures in a channel based on msfle and moving-PIV

Journal of Hydrodynamics 2021年第6期33卷 1119-1128页

作者： Xin-ran Tang Xiang-rui Dong Xiao-shu Cai Wu Zhou School of Energy and Power Engineering University of Shanghai for Science and TechnologyShanghai 200093China Key Laboratory of Multiphase Flow and Heat Transfer in Shanghai Power Engineering University of Shanghai for Science and TechnologyShanghai 200093China

The spatiotemporal evolution of hairpin vortex structures in a fully developed turbulent boundary layer is investigated qualitatively and quantitatively by using two image *** this paper,the moving single-frame and long-exposure(MSFLE)image method is used to intuitively track the evolution process of a hairpin vortex,while the moving particle image velocimetry(moving-PIV)method is applied for obtaining a moving velocity field for quantitative *** to the structural characteristics of the hairpin vortex,an inclined light sheet with an appropriate inclination of 53°is arranged to capture the complete hairpin vortex structure at Re_(θ)=97–*** addition,the core size and the rotational strength of a hairpin vortex are further defined and quantified by the Liutex vector *** evolution process of a complete hairpin vortex structure observed by MSFLE shows that the shear along the normal direction leads to an increasing strength of the hairpin vortex,accompanied by a lifting vortex head and a distance decrease between two vortex legs during the dissipation *** combining moving-PIV with the Liutex identification,the spatiotemporal evolution of four typical regions of a hairpin vortex projecting into a 53°cross-section is *** results show that the process from the generation to the dissipation of a single hairpin vortex can be well characterized and recorded by the Liutex based on the core size and rotational intensity,and the evolution process is consistent with the MSFLE *** to the statistics of vortex core size and rotation intensity along time,the evolution of the hairpin vortex necks and legs can be described as a process of enhancement followed by *** the vortex head,its evolution maintains longer attributed to its far-from-wall position,which consists of an absolute enhancement process(stage 1)with an increasing rotation strength and a constant core size,and an absolute dissipation(stage 2)with a dec

关键词： Turbulent boundary layer hairpin vortex moving single-frame and long-exposure moving particle image velocimetry(PIV) Liutex vortex identification method

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Experimental Investigation on Product and Temperature Distribution in a Continuous flow Packed-Bed Reactor for Dodecahydro-N-Ethylcarbazole Dehydrogenation

SSRN

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SSRN 2024年

作者： Xue, Jingwen Li, Pengzhao Yu, Pengfei Yi, Jinhao Ma, Tao Liu, Hu Che, Defu State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi'an Jiaotong University Xi'An710049 China

The dehydrogenation of dodecahydro-N-ethylcarbazole (H12-NEC) generates enormous gas accompanied by intense heat absorption, affecting heat and mass transfer in porous catalysts. A packed-bed reactor equipped with a temperature measurement device was designed to investigate the continuous flow dehydrogenation of H12-NEC. The effects of weight hourly space velocity (WHSV), reaction temperature, catalyst particle size, and pressure were evaluated. The results reveal that the volume flow rate of hydrogen will increase with the increase of WHSV. And the generation of hydrogen enhances heat transfer by strengthening the perturbation of flow. As the temperature rises, the hydrogen yield increases along with more by-products. The decrease of catalyst particle size improves the hydrogen yield and a more uniform temperature distribution can be created within the reactor due to the weakened wall effect. 456 K and 2 mm of catalyst particle size are determined to be the optimal reaction conditions in the study, achieving the hydrogen production rate of 9.61 [[EQUATION]]. With pressure increasing, the hydrogen yield gradually decreases, but the decreased evaporation of H12-NEC results in a smaller temperature difference between the reactor and heating wall. A comparison with the thermodynamic equilibrium model reveals that the effect of pressure on chemical equilibrium may be more significant than the temperature. © 2024, The Authors. All rights reserved.

关键词： Temperature distribution

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Modification of Anatase TiO2with Amorphous Cu Nanoparticles: An Efficient Photocatalyst for the Reduction of CO2to CO/CH4

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The Journal of Physical Chemistry C 2025年第22期129卷 10083-10093页

作者： Xiong Liu Qulan Zhou Xiaole Chen Shicheng Liu Na Li Zhong Huang Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi’an Jiaotong University Xi’an 710049 China Key Laboratory for Thermal Science and Power Engineering of Ministry of Education Department of Energy and Power Engineering Tsinghua University Beijing 100084 China

Titanium dioxide-based photocatalysts have garnered significant attention for CO2reduction reactions (CO2RR) toward fuel production, with noble metal incorporation markedly enhancing photocatalytic efficiency. However, the development of cost-effective alternatives to expensive metals (e.g., Au, Ag) remains a critical challenge. Herein, amorphous copper nanoparticles (a-Cu NPs) were successfully anchored onto anatase TiO2via a chemical reduction method using Cu(NO3)2·3H2O as the precursor. The optimized 4 wt % a-Cu/TiO2catalyst (4CT) demonstrated remarkable activity, achieving methane and CO production rates of 3.0 and 18.4 μmol·g–1·h–1, respectively, corresponding to 10.0-fold and 7.3-fold enhancements over pristine TiO2. CO2-TPD revealed that the high surface disorder of a-Cu NPs significantly strengthened CO2chemisorption. In situ Fourier transform infrared spectroscopy (FTIR) further indicated that a-Cu loading enabled preferential CO2adsorption over H2O on TiO2surfaces while accelerating the formation of the key intermediate *COOH. This work proposes a synergistic strategy integrating nonprecious metal modification with interfacial engineering, offering a cost-effective pathway to develop high-performance photocatalysts for sustainable CO2conversion.

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Experimental Study on Yield and Quality of Tar from Tar-Rich Coal Under the Simulated In-Situ Conditions

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SSRN 2024年

作者： Ning, Xing Huang, Xiaole Xue, Xiangyu Wang, Chang'an Deng, Lei Che, Defu State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi’an Jiaotong University Xi’an710049 China

Tar-rich coal is considered to have a great potential to extract a large body of liquid fuels through thermal treatment. In this study, an experimental system in which the in-situ conditions can be simulated was built to investigate the yield and the quality of the tar from tar-rich coal. The simulated conditions include in-situ stress, pyrolysis temperature, heating rate, and moisture content. The results indicate that the tar yield increases from 0.83 % to 10.13 % in the temperature range of 200-500 ℃, but a considerable drop of the yield occurs around 600 ℃ due to the cracking of the tar. The heating rate is decreased from 16 °C/min to 2 °C/min, the tar yield is increased from 4.63 % to 10.3 % during the simulated in-situ pyrolysis of tar-rich coal. At low heating rates, the tar yield can be boosted owing to the difference in coal size and underground environment, in contrast to the high heating rate required in traditional coal pyrolysis. Moreover, the ether bonds connected with the oxygenated compounds in the tar under in-situ stress are cleaved, increasing the light components. For other simulated conditions, the low ratio of chain hydrocarbons to aromatic hydrocarbons leads to a decrease in the heavy components. Component variation in the tar under pyrolysis condition promotes the formation of light oil while preventing the synthesis of heavy oil, improving the quality of the tar from the simulated in-situ pyrolysis of tar-rich coal. © 2024, The Authors. All rights reserved.

关键词： Pyrolysis

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Effects of Residual Carbon on Slag flow Characteristics of Zhundong High-Alkali Coal Under Oxy-Fuel Condition

SSRN

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SSRN 2024年

作者： Wang, Chang'an Chen, Yuanmao Luo, Maoyun Zhao, Lin Zhao, Pengbo Che, Defu State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi’an Jiaotong University Xi’an710049 China

The implementation of oxy-fuel combustion technology in slag-tapping cyclone furnace holds significant promise for addressing the challenges associated with the combustion of Zhundong high-alkali coal. However, the flow characteristics of the Zhundong high-alkali coal slag under oxy-fuel condition remain unclear, while the influences of residual carbon have yet to be fully understood. In the present study, a high-temperature flow experimental system was designed to investigate the effects of residual carbon content, degree of graphitization of residual carbon, and atmosphere on the high-temperature flow behaviors of the high-alkali coal slag. The scanning electron microscopy (SEM) with energy dispersive spectrometer (EDS) was utilized to further analyze the microscopic characteristics and elemental distribution within the slag samples. The results reveal that under oxy-fuel condition, the flow length of slag diminishes as the content of residual carbon increases. The slag samples blended with residual carbon exhibit rougher and looser surfaces, with numerous particles adhering to them. In addition, the higher the degree of graphitization in the residual carbon, the lesser its impact on the flowability of the slag. The slag samples in oxy-fuel atmosphere display relatively smooth surfaces with dense structures and extensive liquid-phase areas. On the contrary, slag samples under inert condition feature fewer smooth surfaces, with adherent particles visible along the edges of the structure. The present research provides valuable insights into the high-temperature flow behaviors of slag in oxy-fuel combustion for Zhundong high-alkali coal in slag-tapping boilers, which can contribute to clean and efficient energy production. © 2024, The Authors. All rights reserved.

关键词： Coal

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Graph neural network-driven prediction of high-performance CO_(2)reduction catalysts based on Cu-based high-entropy alloys

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Chinese Journal of Catalysis 2025年第4期71卷 197-207页

作者： Zihao Jiao Chengyi Zhang Ya Liu Liejin Guo Ziyun Wang International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power EngineeringXi’an Jiaotong UniversityShaanxi 710049China School of Chemical Sciences University of AucklandAuckland 1010New Zealand

High-entropy alloy(HEA)offer tunable composition and surface structures,enabling the creation of novel active sites that enhance catalytic performance in renewable energy ***,the inherent surface complexity and tendency for elemental segregation,which results in discrepancies between bulk and surface compositions,pose challenges for direct investigation via density functional *** address this,Monte Carlo simulations combined with molecular dynamics were employed to model surface segregation across a broad range of elements,including Cu,Ag,Au,Pt,Pd,and *** analysis revealed a trend in surface segregation propensity following the order Ag>Au>Al>Cu>Pd>*** capture the correlation between surface site characteristics and the free energy of multi-dentate CO_(2)reduction intermediates,a graph neural network was designed,where adsorbates were transformed into pseudo-atoms at their centers of *** model achieved mean absolute errors of 0.08–0.15 eV for the free energies of C_(2)intermediates,enabling precise site activity *** indicated that increasing the concentration of Cu,Ag,and Al significantly boosts activity for CO and C_(2)formation,whereas Au,Pd,and Pt exhibit negative *** screening stable composition space,promising HEA bulk compositions for CO,HCOOH,and C_(2)products were predicted,offering superior catalytic activity compared to pure Cu catalysts.

关键词： Density functional theory Machine learning CO_(2)reduction High entropy alloys Graph neural network

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Excellent Energy Storage Performance Achieved in Sr(Sc0.5Nb0.5)O3-Doped Bi0.5Na0.5TiO3-Based Lead-Free Relaxor Ferroelectric Ceramics

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ACS Applied Energy Materials 2024年第5期7卷 2030-2038页

作者： Liu, Jinnan Li, Da Zhao, Weichen Xu, Diming Shi, Zhongqi Liu, Wenfeng Su, Jinzhan Zhou, Tao Chen, Guohua Zhou, Di Electronic Materials Research Laboratory & Multifunctional Materials and Structures Key Laboratory of the Ministry of Education International Center for Dielectric Research School of Electronic Science and Engineering Xi’an Jiaotong University Shaanxi Xi’an710049 China State Key Laboratory for Mechanical Behaviour of Materials Xi’an Jiaotong University Xi’an710049 China State Key Laboratory of Electrical Insulation and Power Equipment Xi’an Jiaotong University Shaanxi Xi’an710049 China International Research Centre for Renewable Energy State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Shaanxi Xi’an710049 China School of Electronic and Information Engineering Hangzhou Dianzi University Hangzhou310018 China Electronical Information Materials Devices Engineering Research Center of Ministry of Education Guangxi Key Laboratory of Information Materials School of Material Science and Engineering Guilin University of Electronic Technology Guilin541004 China

Dielectric energy storage ceramics have received significant attention as the primary component for high-pulse power capacitors. Currently, their development is limited by poor energy storage performance, which affects the miniaturization and lightweighting of electronic devices. In this study, a comprehensive optimization approach was adopted to enhance the storage performance (recoverable energy density Wrec and conversion efficiency η) of 0.8Bi0.5Na0.5TiO3-0.2NaNbO3 (BNT-NN) through component optimization design and repeated rolling process (RRP). A series of Sr(Sc0.5Nb0.5)O3 (SSN) was introduced into BNT-NN to modulate the phase structure and improve the relaxation properties. The repeated rolling process was applied to refine the grain and enhance the dense property to boost the breakdown of the electric field. Following the mentioned strategy, we have succeeded in simultaneously obtaining ultrahigh Wrec (∼7.22 J·cm-3) and outstanding η (∼95.32%) under 515 kV·cm-1 for 0.8(BNT-NN)-0.2SSN (RRP) ceramic. More importantly, the ceramic sample possesses outstanding stability over a wide range of temperatures (25-60 °C) and frequencies (1-100 Hz). This study proposes a viable route to better performance of dielectric ceramics for energy storage, and the outstanding performance of the 0.8(BNT-NN)-0.2SSN (RRP) ceramic indicates its promising applicability in high- and high-pulse-power electronic devices. © 2024 American Chemical Society.

关键词： Energy storage

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Experimental study on combustion, ash fusibility and slagging propensity during co-combustion of organic solid waste and lignite

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Journal of the Energy Institute 2023年 106卷

作者： Liu, Hu Wang, Yancheng Xue, Jingwen Zhang, Yankang Yu, Pengfei Che, Defu State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi'an Jiaotong University Xi'an 710049 China

Rapidly growth of organic solid waste (OSW) has caused serious social and environmental problems. Incineration as one of the most good public acceptance and environmentally friendly method attains increasing attention. In this study, the co-combustion characteristics of OSW and lignite, including the ignition and burnout temperature, ash melting and slagging propensity were studied. The experimental results show that the ignition temperature almost remains stable while the burnout temperature of the blends decreases as the increase of the OSW blending ratio, since the heat release during volatile combustion is beneficial for the burnout of coal char, but the polymer may melt and block the pores of the coal char at high temperature when the OSW blending ratio is higher than 30%. Besides, the slagging propensity of blending fuel is severe when the OSW blending ratio is 30%, and special attention should be paid to avoid slagging during the combustion process. © 2022 Energy Institute

关键词： Lignite

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A volume of fluid simulation of the steady deformation and the drag of a single droplet in a flowing gas

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Journal of Hydrodynamics 2021年第2期33卷 334-346页

作者： Zhi-bin Wang Zhong-wei Yang Lie-jin Guo Ren-jie Zhao State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation Southwest Petroleum UniversityChendu 610500China State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong UniversityXi'an 710049China

A method is proposed to investigate the steady deformation and the drag of a single droplet in a flowing gas at a high Reynolds *** volume of fluid(VOF)method is used to model the droplet surface *** direct numerical simulation(DNS)method is used to model the gas flow *** order to avoid the effect of the droplet acceleration on the drag and reduce the computation cost,a body force is added to the droplet to make it fixed at a constant *** body force is determined by using the Newton iteration *** simulated droplet aspect ratio and the drag coefficient agree well with the published experimental ***,the sources of the drag are analyzed and the effect of the Reynolds number and the Weber numbers on the droplet deformation and the drag are *** drag mainly comes from the pressure difference between the droplet-leading zone and the trailing zone,and the turbulence wake would increase the drag.

关键词： Droplet deformation steady drag volume of fluid(VOF) turbulent flow drag force

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Analysis of Different Control Strategies Considering Individual Regulation of Heat User 3

Analysis of Different Control Strategies Considering Individ...

引用

3rd International Conference on Electrical engineering and Mechatronics Technology, ICEEMT 2023

作者： Xun, Zhiwei Wang, Huijie Wang, Liyuan Yang, Long Gao, Yunfang Liu, Ming Guoneng Jinjie Energy Co. Ltd Yulin China Xi'an Jiaotong University Xi'an China Xi'an Jiaotong University State Key Laboratory of Multiphase Flow in Power Engineering Xi'an China

ISBN: (纸本)9798350303698

In the process of outdoor temperature change, it is beneficial to improve the comfort of thermal users to formulate adjustment and control strategies according to the actual needs of each user. In this paper, different adjustment modes are established according to the thermal comfort of users, and the control strategies of rising and cooling within 0, 30 and 60 minutes are proposed, and the indoor temperature control effect and heating energy consumption of each adjustment mode under different control strategies are analyzed. The results show that: in different modes, when the rise and cooling time increase, compared with the design room temperature, the indoor temperature difference under the control mode is smaller, but the time needed to reach stability is longer. At the same time, the total heat load is unchanged, but the total pump work decreases. © 2023 IEEE.

关键词： Energy utilization

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