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Evaluation of stability and catalytic activity of Ni catalysts for hydrogen production by biomass gasification in supercritical water

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Carbon Resources Conversion 2019年第1期2卷 95-101页

作者： Youjun Lu Hui Jin Rui Zhang State Key Laboratory of Multiphase Flow in Power Engineering(SKLMFPE) Xi’an Jiaotong UniversityXi’an 710049ShaanxiChina

Supercritical water gasification is a promising technology for wet biomass *** this paper,Ni and other metal catalysts were synthesized by wet *** stability and catalytic activities of Ni catalysts were ***,catalytic activities of Ni,Fe,Cu catalysts supported on MgO were tested using wheat straw as raw material in a batch reactor at 723 K and water density of 0.07 cm^(3)/*** results showed that the order of metal catalyst activity for hydrogen generation was Ni/MgO>Fe/MgO>Cu/***,the influence of different supports on Ni catalysts performance was *** results showed that the order of the Ni catalysts’activity with different supports was Ni/MgO>Ni/ZnO>Ni/Al_(2)O_(3)>Ni/ZrO_(2).Finally,the effects of Ni loading and the amount of Ni catalyst addition on hydrogen production,and the stability of Ni/MgO catalyst were *** was found that serious deactivation of Ni catalyst in the process of supercritical water gasification took *** if carbon deposited on the catalyst surface was removed by high temperature calcination and the catalyst was reduced with hydrogen,the activity of used catalyst was only partially restored.

关键词： Ni catalyst Deactivation Biomass gasification Supercritical water Hydrogen production

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Comparison of chemical composition and acidity of size-resolved inorganic aerosols at the top and foot of Mt. Hua, Northwest China: The role of the gas-particle distribution of ammonia

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Science of the Total Environment 2023年 905卷 166985页

作者： Feng, Qiao Liu, Haijiao Dai, Wenting Cao, Yue Shen, Minxia Liu, Yali Qi, Weining Chen, Yukun Guo, Xiao Zhang, Yifan Li, Lu Zhou, Bianhong Li, Jianjun State Key Laboratory of Loess and Quaternary Geology Key Lab of Aerosol Chemistry and Physics Institute of Earth Environment Chinese Academy of Sciences Xi'an710061 China College of Geography and Environment Baoji University of Arts and Sciences Shaanxi Key Laboratory of Disaster Monitoring and Mechanism Simulation Baoji721013 China Xi'an Institute for Innovative Earth Environment Research Xi'an710061 China National Observation and Research Station of Regional Ecological Environment Change and Comprehensive Management in the Guanzhong Plain Shaanxi China State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China

Aerosol pH is not only a diagnostic indicator of secondary aerosol formation, but also a key factor in the specific chemical reaction routes that produce sulfate and nitrate. To understand the characteristics of aerosol acidity in the Mt. Hua, the chemical fractions of water-soluble inorganic ions in the atmospheric PM2.5 and size-resolved particle at the top and foot of Mt. Hua in summer 2020 were studied. The results showed the mass concentrations of PM2.5 and water-soluble ions at the foot were 2.0–2.6 times higher than those at the top. The secondary inorganic ions, i.e., SO42−, NO3−, and NH4+ (SNA) were 56 %–61 % higher by day than by night. SO42− was mainly distributed in the fine particles (Dp 3− showed a unimodal size distribution (peaking at 0.7–1.1 μm) at the foot and a bimodal (0.7–1.1 μm and 4.7–5.8 μm) size distribution at the top. At the top site, the distribution of NO3− in coarse particles (> 2.1 μm) was mainly attributed to the gaseous HNO3 volatilized from fine particles reacting with cations in coarse particles to form non-volatile salts (such as Ca(NO3)2). The pH values of PM2.5 were 2.7 ± 1.3 and 3.3 ± 0.42 at the top and foot, respectively. NH4+/NH3(g) plays a decisive role in stabilizing aerosol acidity. In addition, the increase of the liquid water content (LWC) at the foot facilitates the gas-particle conversion of NH3, while the H+ concentration was diluted, resulting in a decrease in acidity at the foot. NH4+/NH3 had good linear correlations with SO42−, NO3−, and LWC during the daytime at both sites, indicating that SO42−, NO3−, and LWC together affect the gas-particle distribution of ammonia by day: however, the effect of LWC at night was not evident. © 2023

关键词： Ammonia

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A 3d Ptco Degradation Model for Long-Term Performance Prediction of a Scaled-Up Pemfc Under Constant Voltage Operation

SSRN

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SSRN 2023年

作者： Yang, Yunjie Bai, Minli Zhou, Zhifu Wu, Wei-Tao Zhao, Jian Wei, Lei Li, Yang Li, Yubai Song, Yongchen Key Laboratory of Ocean Energy Utilization and Energy Conservation of Ministry of Education Dalian University of Technology Dalian116024 China State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'An710049 China School of Mechanical Engineering Nanjing University of Science and Technology Nanjing210094 China Center for Advanced Vehicular Systems Mississippi State University Starkville39762 United States Department of Mechanical and Energy Engineering Southern University of Science and Technology Shenzhen518055 China

The non-uniform distribution of reactants, pressure, temperature, and reaction rate, in a scaled-up proton exchange membrane fuel cell (PEMFC) can lead to different catalyst degradation rate, impacting the long-term performance of PEMFCs. However, the local catalyst degradation behaviors in a PEMFC stack have not yet been fully understood due to the lack of experimental approaches and catalyst degradation model. In the present study, a numerical model is established for a 200 cm2 commercial-sized PEMFC stack with realistic anode and cathode flow fields. PtCo is employed as the cathode catalyst, and a 3D PtCo catalyst degradation model is developed to analyze the non-uniform evolution of the electrochemical active surface area (ECSA), current density, and Co2+ in the catalyst layers under the constant voltage conditions. The modeling results demonstrated that catalyst degradation is more severe downstream as well as under land of the cathode flow field, and the cathode catalyst layer (CCL) is the area most contaminated by the Co2+. The non-uniform catalyst degradation as well as Co2+ contamination increased the activation losses and local oxygen transport resistance. The catalyst degradation leads to a total power loss of 43.3% after 80,000 hours operation. The aging model provides a better understanding for large scale PEMFC stacks regarding its nonuniform PtCo degradation and can assist the future design of commercial PEMFCs with better lifetime. © 2023, The Authors. All rights reserved.

关键词： Proton exchange membrane fuel cells (PEMFC)

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Numerical Investigations for the Pcm and Liquid Immersion Cooling Effects on Lithium Ion Battery Thermal Runaway Mitigation

SSRN

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SSRN 2023年

作者： Liu, Xinyu Zhou, Zhifu Wu, Wei-Tao Wei, Lei Wu, Weixiong Li, Yang Gao, Linsong Li, Yubai Song, Yongchen Key Laboratory of Ocean Energy Utilization and Energy Conservation of Ministry of Education Dalian University of Technology Dalian116024 China State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi’an710049 China School of Mechanical Engineering Nanjing University of Science and Technology Nanjing210094 China Department of Mechanical and Energy Engineering Southern University of Science and Technology Shenzhen518055 China Energy and Electricity Research Center Jinan University Zhuhai519070 China

In this study, a three-dimensional (3D) thermal runaway (TR) model with conjugate heat transfer submodel is adopted. TR behaviors for a battery pack with 12 prismatic LIBs are then simulated. Three thermal safety measures of TR protection from internal shorting in Cell 1 to pack level configuration are compared and evaluated. Paraffin phase change material (PPCM) is firstly proposed to delay the TR propagation between LIBs with solid-liquid phase change as heat transfer mechanism. Different thicknesses of PPCMs are compared to verify the TR mitigation performance of the PPCM under thermal abuse condition. The TR time for the Cell 2 is delayed to be 64 s, 266 s and 414 corresponding to PPCM thickness of 1.8 mm, 3.6 mm and 5.4 mm. As the simulation results shows, this TR time can be further delayed to 798 s by a strategy with combing PPCM with insulation. In addition, this work proposes a novel thermal safety protection based on immersion cooling with pool boiling of fluorinated liquid as heat transfer mechanism. We observe that the average temperature of Cell 2 - Cell 12 tends to be within 34oC under immersive cooling condition, which indicates the possibility to prevent the TR. © 2023, The Authors. All rights reserved.

关键词： Lithium-ion batteries

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flow visualization study of two-phase flashing spray with iso-pentane 14

Flow visualization study of two-phase flashing spray with is...

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14th International Conference on Liquid Atomization and Spray Systems, ICLASS 2018

作者： Wang, J.F. Zhou, Z.F. Yang, T. Chen, B. Wang, G.X. Zhao, L. State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China Department of Mechanical Engineering University of Akron AkronOH44325-3903 United States

The explosive flashing spray commonly occurs during the accidental release of flammable and toxic pressure-liquefied gases in chemical or nuclear industry. This work conducts a small-scale flashing spray experiment in house to simulate the accidental release, aiming to investigate the macroscopic atomization characteristics, which is helpful for the risk assessments and therefore minimizing the impact of the release hazard. The iso-pentane was taken as the working medium, and a transparent straight-tube nozzle with inner diameter of 0.6 mm and length of 40 mm was employed to generate the flashing spray vertically. A high-speed camera was used to record the images of the flashing spray. The whole dynamic evolution was obtained. The effects of injection pressure (0.6 to 2.4 MPa) and initial temperature (40 to 60 oC) were fully explored, respectively. The experiment results indicate that the superheat and injection pressure have a coupled effect on flashing spray. The release of superheat results in phase change with the generation of bubble within liquid, which facilitates the break-up of liquid core and ligament liquid. Meanwhile, the increment of injection pressure can enhance the disturbance of the flow and the number of nucleation. © 2018 Solar Turbines Incorporated.

关键词： Atomization

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Startup transient thermal-hydraulic analysis of a lithium heat pipe cooled reactor Core

Startup transient thermal-hydraulic analysis of a lithium he...

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2020 International Topical Meeting on Advances in Thermal Hydraulics, ATH 2020

作者： Liu, Xiao Tian, Zhixing Wang, Chenglong Tian, Wenxi Qiu, Suizheng Su, Guanghui Shanxi Engineering Research Center of Advanced Nuclear Energy School of Nuclear Science and Technology Xi'an Jiaotong University State Key Laboratory of Multiphase Flow in Power Engineering Xi'an710049 China

ISBN: (纸本)9780894487774

Heat pipe cooled reactor has been proposed for applying in the space station and underwater exploration featured with high reliability, low noise level and compact structure. A typical design of a heat pipe cooled reactor system is HP-STMCs designed by the University of New Mexico. It is conceptually designed as a fast reactor, lithiumfilled heat pipes that transfer heat to potassium heat pipes radiator and thermoelectric generators. In this paper, a code is developed for studying the operating thermal-hydraulic characteristics of the reactor core, which consists of core thermal-hydraulic model, neutron kinetics model and heat pipe startup model. The highest temperatures of fuel and matrix in reactor core shows at the 2nd channel, which reach 1720K and 1545K from the results of steady-state. As for the startup transient, the code for heat pipe cooled reactor core successfully predicts key parameters during startup transient, such as each layer material temperature of reactor core, a single heat pipe's temperature response and heat rejection power. The code has initially predicted the transient response of the heat pipe cooled reactor under 800W/s and130W/s power increasing rates. It is discussed that the startup strategy of power increasing rates is based on heat pipe transition temperature (916K). This research provides valuable experience for designing and formulating control strategies of the heat pipe cooled reactor. © ATH 2020 - International Topical Meeting on Advances in Thermal *** rights reserved.

关键词： Heat pipes

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A systematic improvement of the high-quality temperature field reconstruction for acoustic pyrometry

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Case Studies in Thermal engineering 2025年 72卷

作者： Jingkao Tan Na Li Qulan Zhou Yanyuan Hu Lehang Chen Zhongquan Gao Jie Zhou State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China Xi'an Aerospace Propulsion Institute Xi'an 710100 China

Obtaining an accurate temperature distribution in furnaces for industrial combustion devices is critical. Acoustic pyrometry (AP) is a promising methodology for high-quality temperature field reconstruction, which is widely used in the monitoring of atmosphere, room, and furnace. However, due to the harsh working environment and the engineering limitations, the number of installed acoustic transducers is restricted, which in turn results in sparse valid data and an ill-posed AP problem. We used multiple means of improvement to improve the reconstruction performance of AP in a gradual and systematic manner. The fast finite-difference shooting method, the adaptive grid evolution strategy (AGES) and the radial basis function approximation with polynomial reproduction (RBFPR) were proposed and integrated into the sequential process optimization approach we concluded to systematically improve the reconstruction performance over the initial algorithm. In this approach, we optimized the parameters used for the reconstruction sequentially, analyzed the effectiveness of various means of improvement, finalized and validated an algorithm that takes into account universality and precision. Qualitative and quantitative analyses of the simulation and experimental results show the validity of the finalized algorithm and the sequential process optimization approach, demonstrating its significance for furnace temperature field measurement, combustion control, and environmental protection.

关键词： Inverse problem Acoustic pyrometry Acoustic tomography Acoustic refraction Algorithm improvement Domain discretization Temperature field reconstruction

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Numerical study on the mechanism of drag modulation by dispersed drops in two-phase Taylor-Couette turbulence

arXiv

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arXiv 2023年

作者： Su, Jinghong Yi, Lei Zhao, Bidan Wang, Cheng Xu, Fan Wang, Junwu Sun, Chao New Cornerstone Science Laboratory Center for Combustion Energy Key Laboratory for Thermal Science and Power Engineering of Ministry of Education Department of Energy and Power Engineering Tsinghua University Beijing100084 China State Key Laboratory of Multiphase Complex Systems Institute of Process Engineering Chinese Academy of Sciences P. O. Box 353 Beijing100190 China Department of Engineering Mechanics School of Aerospace Engineering Tsinghua University Beijing100084 China

The presence of a dispersed phase can significantly modulate the drag in turbulent systems. We derived a conserved quantity that characterizes the radial transport of azimuthal momentum in the fluid-fluid two-phase Taylor-Couette turbulence. This quantity consists of contributions from advection, diffusion, and two-phase interface, which are closely related to density, viscosity, and interfacial tension, respectively. We found from interface-resolved direct numerical simulations that the presence of the two-phase interface consistently produces a positive contribution to the momentum transport and leads to drag enhancement, while decreasing the density and viscosity ratios of the dispersed phase to the continuous phase reduces the contribution of local advection and diffusion terms to the momentum transport, respectively, resulting in drag reduction. Therefore, we concluded that the decreased density ratio and the decreased viscosity ratio work together to compete with the presence of two-phase interface for achieving drag modulation in fluid-fluid two-phase turbulence. Copyright © 2023, The Authors. All rights reserved.

关键词： Drag

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Frequency characteristics and slug velocities of severe slugging in pipeline-riser systems

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Ocean engineering 2025年 336卷

作者： Yuwen Li Qiang Xu Yeqi Cao Haiyang Yu Bo Huang Liejin Guo State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China College of Petroleum Engineering Xi'an Shiyou University Xi'an 710065 China

The frequency characteristics and slug velocities of severe slugging are crucial for assessing fatigue damage and ensuring flow safety in offshore pipeline-riser systems. The flow pattern distributions and flow characteristics of severe slugging were obtained for the small-scale ( L H = 20 m, L I = 3 m, H R = 2 m) and kilometer-scale long-distance ( L H = 1657 m, L I = 30 m, H R = 29 m) pipeline-riser systems. Due to the periodicity of severe slugging, the local flow pattern in the riser was a composite pattern of alternating slug flow, bubble flow, and liquid flow. The significant decrease of the differential pressure in the riser induced slug flow in the horizontal pipe. A quantitative correlation was established among structural parameters, dimensionless gas and liquid Froude numbers, and severe slugging frequency. The average percent absolute relative error of the prediction was reduced from 58.31 % to 28.42 %. The peak velocities of liquid slugs in the small-scale and kilometer-scale systems can reach 7.5 and 22.9 times the inlet mixture velocities, respectively. A mechanism prediction model for liquid slug peak velocity considering the average void fraction in the riser was proposed. Approximately 85 % of the predicted values were within the error range of ±20 %.

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Unique Z-Scheme TiO2 Homojunction Enabling Photocatalytic Water Splitting with Unit Quantum Efficiency

SSRN

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SSRN 2023年

作者： Lu, Kejian Guan, Xiangjiu Liu, Feng Fu, Yiwei Peng, Hao Hu, Anlan Huang, Jie Yu, Fangbo Zhang, Chunyang Xue, Fei Fu, Wenlong Liu, Maochang InternationalResearchCenter for Renewable Energy State Key Laboratory ofMultiphase Flow in Power Engineering Xi’an Jiaotong University Shaanxi710049 Xi’an China Suzhou Academy ofXi’an Jiaotong University Jiangsu Suzhou215123 China

TiO2 appears as the most widely investigated semiconductor photocatalyst for solar water splitting, yet with limited success approaching the upper limit of quantum efficiency. Promising performance could be expected from optimizing crystal and electronic structures via modulating Ti-O coordination, with respect to overcoming the obstacles from poor charge transfer behaviour and inferior surface reaction kinetics, while remaining as a significant challenge. Herein, we demonstrate a novel defect-rich Z-scheme TiO2 homojunction photocatalyst by precisely thermodynamically regulated one-step symbiotic phase transition. The Z-scheme TiO2 promises a remarkable H2 evolution rate (2.20 mmol h-1) with a quantum efficiency of 99.24% at 350 nm. Detailed analysis indicates the electronic interactions and redistribution induced by the modification of Ti-O coordination, which contributes to establishing a unique charge transfer via Z-scheme mode and an activated surface to break through the kinetic barrier of water oxidation for achieving overall water splitting. © 2023, The Authors. All rights reserved.

关键词： Titanium dioxide

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