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Experimental studies of ash film fractions based on measurement of cenospheres geometry in pulverized coal combustion

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Frontiers in Energy 2021年第1期15卷 91-98页

作者： Siqi LIU Yanqing NIU Liping WEN Yang LIANG Bokang YAN Denghui WANG Shi'en HUI State Key Laboratory of Multiphase Flow in Power Engineering Department of Thermal EngineeringSchool of Energy and Power EngineeringXi'an Jiaotong UniversityXi'an 710049China

In pulverized coal particle combustion, part of the ash forms the ash film and exerts an inhibitory influence on combustion by impeding the diffusion of oxygen to the encapsulated char core, while part of the ash diffuses toward the char core. Despite the considerable ash effects on combustion, the fraction of ash film still remains unclear. However, the research of the properties of cenospheres can be an appropriate choice for the fraction determination, being aware that the formation of cenospheres is based on the model of coal particles with the visco-plastic ash film and a solid core. The fraction of ash film X is the ratio of the measuring mass of ash film and the total ash in coal particle. In this paper, the Huangling bituminous coal with different sizes was burnt in a drop-tube furnace at 1273, 1473, and 1673 K with air as oxidizer. A scanning electron microscope (SEM) and cross-section analysis have been used to study the geometry of the collected cenospheres and the effects of combustion parameters on the fraction of ash film. The results show that the ash film fraction increases with increasing temperature and carbon conversion ratio but decreases with larger sizes of coal particles. The high fraction of ash film provides a reasonable explanation for the extinction event at the late burnout stage. The varied values of ash film fractions under different conditions during the dynamic combustion process are necessary for further development of kinetic models.

关键词： ash film fraction cenospheres coal combustion fly ash

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Multi-Dimensional Coupling Analysis of the Control Rod Withdraw Accident with Scam in the Typical Lfr

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SSRN 2023年

作者： Qiu, Hanrui Zhang, Jing Wang, Mingjun Tian, Wenxi Su, Guanghui State Key Laboratory of Multiphase Flow in Power Engineering School of Nuclear Science and Technology Xi’an Jiaotong University Xi’an710049 China

MYRRHA is the Gen IV liquid metal cooled fast reactor, which is a pool-type reactor system developed and designed by the Belgian Nuclear Research Center SCK·CEN. Regarding the safety assessment of the installation, the major challenge is to analyze the complex coolant flow field characteristics in the large open regions of the reactor vessel. In this paper, a coupled sub-channel/CFD multi-scale platform is developed through implementing the sub-channel code SACOS-PB to the CFD code FLUENT based on the domain decomposition and explicit numerical scheme. The flow field characteristics in the upper plenum of reactor emergency shutdown after a reactivity insertion accident (RIA) were investigated. Based on the RIA analysis, the thermal stratification effect has been observed in the upper plenum. The analysis results well demonstrated the 3D flow and local phenomenon of the fluid in the upper plenum, which is significant to reactor design and reactor safety analysis of LFRs. © 2023, The Authors. All rights reserved.

关键词： Control rods

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Recent progress on molecular catalysts integrated photoelectrochemical systems for water oxidation

Materials Today Catalysis

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Materials Today Catalysis 2024年 4卷

作者： Wan, Xiaokang Zhu, Guanghui Zhou, Zhifu Guan, Xiangjiu International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China School of Environment and Energy Engineering Anhui Jianzhu University Hefei230601 China

The major limitations of photoelectrochemical (PEC) water splitting lies in the currently unsatisfying efficiency and stability of the semiconductor materials-based water splitting systems. By addressing these limitations, the immobilization of the molecular catalysts on semiconductor photoanodes to establish a hybrid inorganic-organic PEC system has attracted an increasing research attention. It is crucial to choose a suitable molecular catalyst and effectively couple it into a hybrid photoelectrode system. In this review, focusing on the water oxidation process, molecular catalysts integrated photoelectrochemical water oxidation systems are highlighted from the perspective of the roles of molecular catalysts and the integration strategies in the hybrid system. The most recent advances are summarized with various case studies presented, based on which perspectives are proposed to provide guidance toward the rational design of an integrated system for future development. © 2024 The Authors

关键词： Hybrid systems

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Analysis of Gas-Cooled Micro Modular Reactor (MMR) Fuel

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SSRN 2024年

作者： Deng, Chaoqun Zhu, Siyang He, Yanan Wu, Yingwei He, Kai Zhang, Jing Su, Guanghui School of Nuclear Science and Technology Shaanxi Key Laboratory of Advanced Nuclear Energy and Technology State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi’an710049 China China Nuclear Power Engineering Co. Ltd. Beijing100840 China

The gas-cooled micro modular reactor (MMR) is a novel concept with compact fuel form consists of thousands of tri-isotropic fuel (TRISO) particles dispersed in silicon carbide matrix. The MMR fuel is high volume packing fraction and horizontally placed within graphite channels. Due to the complexity of the fuel structure and the challenges involved in simulation, a multi-scale and multi-physics coupled analyses method of MMR fuel was realized in this work by implementing physical models into the open-source finite element platform MOOSE. Though the simulation of the typical design MMR fuel during normal operation, the thermal-mechanical analysis and the failure analysis were conducted. The results show that the arrangement of MMR fuel horizontally within graphite channels resulted in non-uniform gap between the fuel and graphite brick, leading to an "off-center" temperature distribution within the fuel, the peak temperature is about 1314 K. Higher-temperature sub-zones exhibit greater internal pressure within TRISO and show greater tensile stress in the Chemical Vapor Deposited Silicon Carbide (CVD-SiC) layer. Regarding fuel failure analysis, this work found limited impact from Pd penetration and kernel migration. Pressure-induced particle failure, closely linked with stress in CVD-SiC, emerges as the primary failure criterion. The overall probability of fuel failure remains relatively low, with a maximum probability of 4.1×10-5. Statistical data reveals that a significant majority (71%) of TRISO particles exhibit a failure probability below 2×10-5, while only 8.8% reach 4×10-5 © 2024, The Authors. All rights reserved.

关键词： Graphite

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Dense fluid transport through nanoporous graphene membranes in the limit of steric exclusion

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Physical Review Fluids 2024年第4期9卷 044202-044202页

作者： Runfeng Zhou Mathew M. Swisher Akshay Deshmukh Chengzhen Sun John H. Lienhard Nicolas G. Hadjiconstantinou Department of Mechanical Engineering Massachusetts Institute of Technology Cambridge Massachusetts 02139 USA State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an Shaanxi 710049 China Center for Computational Science & Engineering Massachusetts Institute of Technology Cambridge Massachusetts 02139 USA

We investigate transport of dense fluid flow through nanoporous membranes in the limit of steric exclusion using molecular dynamics (MD) and finite element simulations. Simulation results suggest that, for simple fluids, deviations from Sampson flow are a consequence of the competition between slip and finite atomic size effects. The latter manifest themselves by introducing an effective pore size, as well as an effective membrane thickness. We propose an analytical model for the membrane permeance that accounts for all these factors. We also show how this model can be modified to describe transport of low molecular weight aromatic hydrocarbons across these membranes in the steric limit. Extensive validation of this model is conducted through MD simulations of Lennard-Jones fluids permeating single- and multilayer graphene membranes, as well as low molecular weight organic liquids permeating single-layer graphene membranes.

关键词： Nanofluidics Finite-element method Molecular dynamics

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Comprehensive Performance Analysis of Steam and Flue Gas Stepwise/Staged Heating Molten Salt Thermal Storage Systems Coupled with Coal-Fired power Plants

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SSRN 2024年

作者： Jing, Hao Wang, Dengliang Chen, Weixiong Zhao, Yongliang Wang, Chaoyang Zhang, Kezhen Yan, Junjie State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China Xi’an Thermal Power Research Institute Co. Ltd. Xi’an710054 China

The rapid development of renewable energy has put forward higher requirements for the flexibility and deep peak shaving ability of coal-fired power plants (CFPPs). Molten salt thermal energy storage (TES) is considered a potential solution. In this study, a CFPP coupled steam and flue gas stepwise/staged heating molten salt TES system is proposed. The proportion of steam thermal energy allocated to the molten salt and feed water is adjusted. The thermodynamic and economic performance of two configurations under different thermal load distribution ratios are compared and studied. The results show that with the increase of molten salt thermal load distribution ratio, the thermal storage capacity, denitrification efficiency, and charging exergy loss increase, while the equivalent round-trip efficiency, energy storage density, and discharging exergy loss decrease. When the molten salt thermal load distribution ratio is the same, the stepwise configuration has higher energy storage density and denitrification efficiency, lower charging exergy loss of TES, and better economic performance. The staged configuration has higher thermal storage capacity and lower exergy loss of CFPP. In general, the economic performance of the stepwise configuration is higher, while the staged configuration's thermodynamic performance is higher. © 2024, The Authors. All rights reserved.

关键词： Coal fired power plant

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Multi-Objective optimization of oil–gas cyclone separators considering liquid storage in the tank bottom

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Separation and Purification Technology 2025年 374卷

作者： Wang, Lingzi Du, Wei Liu, Ruiyi Feng, Jianmei Peng, Xueyuan Cao, Feng School of Energy and Power Engineering Xi'an Jiaotong University Shaanxi Xi'an710049 China The First Gas Plant of PetroChina Changqing Oilfield Company Shaanxi Jingbian718500 China State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China

As an efficient separation device, the gas–liquid cyclone separator has been widely used in oil injection compressor systems. It can effectively reduce the oil content in the high-pressure airflow, directly affecting the fuel consumption, operating efficiency, and exhaust quality parameters of compressors, making it crucial to enhance the separator's performance. Given the critical role of geometric configuration in determining cyclone separator efficiency, this study comprehensively considers several influencing factors including the structure parameters. Taguchi method and analysis of variance (ANOVA) were used to quantify the contribution of three factors to the performance percentage of the separator, and the dual-objective optimization of the efficiency and pressure drop of the separator was carried out with the grey correlation analysis method. In the simulation calculation, this paper employs the DPM-to-VOF method coupled with the Euler wall film (EWF) to simulate the oil droplet particle separation process, featuring model transformation capabilities under specified conditions. The investigation culminates in the development of a parametric-performance prediction model and establishes optimal operational parameters for cyclone separators: the inlet velocity (vin) should be set at 24.49 m/s, the height of the inner cylinder of the separator tank (Ht) should be 1.2 times the diameter, and the buffer height between the inner cylinder and the liquid surface (Hm) should be 0.9 times the diameter. © 2025

关键词： Cyclone separators

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Influence of light-dark cycles on hydrogen production from sugarcane bagasse by Rhodobacter sphaeroides

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International Journal of Hydrogen Energy 2025年 145卷 28-35页

作者： Wen Cao Xuan Wei Jiyan Lu Mengyao Li Jiali Feng State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 Shaanxi PR China College of Biology and Oceanography Weifang University Weifang 261061 Shandong PR China Weifang Municipal Key Laboratory of Agricultural Planting Quantization and Application Weifang 261061 Shandong PR China

Photo-fermentative hydrogen production from lignocellulosic biomass offers a clean, efficient, and eco-friendly alternative for energy generation. Large-scale photo-fermentative hydrogen production, ideally conducted under outdoor conditions is influenced by the daily light-dark cycle. This study examines the effect of a 12-h light-dark cycle (12L/12D) on hydrogen production by Rhodobacter sphaeroides HY01 using sugarcane bagasse (SCB), comparing it with continuous light (CL) conditions. The results show that bacterial growth was not significantly affected by the light-dark cycle. The optical density (OD 660 ) of the culture reached 3.25 under 12L/12D and 3.49 under CL. However, total hydrogen yield decreased substantially under the light-dark cycle, from 6020.11 ± 54.71 mL/L in CL to 4242.73 ± 182.03 mL/L in the 12L/12D condition. Additionally, the rate of hydrogen production was higher under CL (119.78 ± 4.82 mL/(L·h)) compared to 12L/12D (60.97 ± 7.27 mL/(L·h)), while the lag phase was shorter under CL, at 17.25 ± 1.04 h, versus 20.37 ± 3.98 h under 12L/12D. Gas chromatography-mass spectrometry (GC-MS) analysis identified lactic acid, butyric acid, and ethanol as the primary soluble metabolites, with ethanol yield under 12L/12D being approximately half of that under CL. Notably, light conversion efficiency (LCE) for hydrogen production was significantly enhanced under the light-dark cycle, showing a 1.36-fold increase compared to CL conditions. These findings not only contribute to the understanding of the influence of light cycles on biohydrogen production but also support the development of more efficient and cost-effective biohydrogen systems for sustainable energy production.

关键词： Light conversion efficiency Light-dark cycle Lignocellulosic biomass Photo fermentation hydrogen production Sugarcane bagasse

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Boosting photocatalytic water vapor splitting by the integration of porous g-C_(3)N_(4)and carbonized melamine foam

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Science China Materials 2024年第9期67卷 2957-2964页

作者： Shujian Wang Dongjie Liu Chunyang Zhang Jie Huang Shidong Zhao Kejian Lu Biao Wang Hao Peng Yitao Si Maochang Liu International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power EngineeringXi’an Jiaotong UniversityXi’an710049China School of Chemistry and Chemical Engineering Southeast UniversityNanjing211189China Suzhou Academy of Xi’an Jiaotong University Suzhou215123China Gree Altairnano New Energy Inc. Zhuhai519040China

We report a photothermally-induced liquid-solid/gas-solid-decoupling photocatalytic water-splitting system,where a carbonized melamine foam(CMF)and a porous g-C_(3)N_(4)(PCN)serve as the photothermal substrate and model photocatalyst,***,liquid water is transformed into the gaseous phase over the CMF due to the photothermal effect,and the generated vapor can be split into hydrogen by PCN via the *** unique biphasic photocatalytic system exhibits a high hydrogen production rate of 368.1µmol h^(-1),which is 2.4 and 25.6 times larger than those of the traditional triphasic PCN system(151.7µmol h^(-1))and g-C_(3)N_(4)(CN)system(14.4µmol h^(-1)),*** improved photocatalytic performance is mainly attributed to the optimized energy and mass transfer at the gas-liquid-solid reaction interface,where gas products are rapidly desorbed in the photocatalytic *** work provides a novel strategy to enhance the photocatalytic performance from the perspectives of energy and mass flow.

关键词： photocatalytic photothermal mass transfer g-C_(3)N_(4) gas-solid

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Evaporation of sub-millimeter flying dinitrogen tetroxide droplet under high temperature and pressure: Experimental measurement and theoretical modeling

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Chinese Journal of Aeronautics 2025年第5期 82-93页

作者： Lihan FEI Wu ZHU Yuyuan ZHANG Peng ZHANG Zuohua HUANG Chenglong TANG State Key Laboratory of Multiphase Flow and Power Engineering Xi'an Jiaotong University Department of Mechanical Engineering City University of Hong Kong

The evaporation behaviors are crucial for the flame location estimation in liquid rocketengines. This work, for the first time, experimentally reports the sub-millimeter droplet evaporationcharacteristics of the corrosive dinitrogen tetroxide（NTO, one prevailing hypergolic oxidizer） athigh ambient pressure up to 4.5 MPa. An in-house corrosion-resistant droplet generator is usedto generate isolated flying droplets of sub-millimeter size, which are then exposed in a gas environ-ment with temperatures between 1 010 K and 1 210 K and pressures in the range between 2.0 MPaand 4.5 MPa, provided by an optical rapid compression machine. Parallelly, a theoretical modelconsidering both the droplet ambient convection and the NTO dissociation is developed. Resultsindicate that firstly, the present theoretical model that considers the transient droplet-ambient con-vection as well as the temperature and pressure dependent rate of dissociation shows good agree-ment with the experimentally observed droplet lifetime. In addition, the flying droplets velocityregress gradually due to momentum exchange with the ambient, which is more prominent at higherpressure. The evaporation caused droplet size reduction is consistent with the classical D2-law pre-diction, in the present temperature and pressure range. Finally, higher temperature and pressureaccelerate the evaporation and an empirical correlation for the temperature and pressure dependentevaporation rate constant is proposed, which shows good agreement with experiment and simula-tion results.

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