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Large contributions of emission reductions and meteorological conditions to the abatement of PM_(2.5)in Beijing during the 24th Winter Olympic Games in 2022

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Journal of Environmental Sciences 2024年第2期136卷 172-188页

作者： Yaping Jiang Shaocai Yu Xue Chen Yibo Zhang Mengying Li Zhen Li Zhe Song Pengfei Li Xiaoye Zhang Eric Lichtfouse Daniel Rosenfeld Key Laboratory of Environmental Remediation and Ecological Health Ministry of EducationResearch Center for Air Pollution and HealthCollege of Environmental and Resource SciencesZhejiang UniversityHangzhou 310058China College of Science and Technology Hebei Agricultural UniversityBaoding 071000China Chinese Academy of Meteorological Sciences China Meteorological AdministrationBeijing 100081China Aix-Marseille Univ CNRSColl FranceCNRSIRDINRAEEuropole Mediterraneen de l’ArboisAvenue Louis Philibert13100 Aix en ProvenceFrance Xi’an Jiaotong University State Key Laboratory of Multiphase Flow in Power EngineeringXi’an 710049China Institute of Earth Sciences The Hebrew University of JerusalemJerusalemIsrael

To guarantee the blue skies for the 2022 Winter Olympics held in Beijing and Zhangjiakou from February 4 to 20,Beijing and its surrounding areas adopted a series of emission control *** provides an opportunity to determine the impacts of large-scale temporary control measures on the air quality in Beijing during this special ***,we applied the WRF-CMAQ model to quantify the contributions of emission reduction measures and meteorological *** show that meteorological conditions in 2022 decreased PM_(2.5)in Beijing by 6.9 and 11.8μg/m^(3)relative to 2021 under the scenarios with and without emission reductions,*** emission reduction measures implemented in Beijing and seven neighboring provinces resulted in an average decrease of 13.0μg/m^(3)(-41.2%)in PM_(2.5)in *** the entire period,local emission reductions contributed more to good air quality in Beijing than nonlocal emission *** the emission reduction scenario,local,controlled regions,other regions,and boundary conditions contributed 47.7%,42.0%,5.3%,and 5.0%to the PM_(2.5)concentrations in Beijing,*** results indicate that during the cleaning period with the air masses from the northwest,the abatements of PM_(2.5)were mainly caused by local emission ***,during the potential pollution period with the air masses from the east-northeast and west-southwest,the abatements of PM_(2.5)were caused by both local and nonlocal emission reductions almost *** implies that regional coordinated prevention and control strategies need to be arranged scientifically and rationally when heavy pollution events are forecasted.

关键词： PM_(2.5) WRF-CMAQ Meteorological conditions Emission reductions Winter Olympic games

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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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Sub- and Supercritical Water Flooding for Enhanced Oil Recovery in High Water Cut Heavy Oil Reservoirs: An Experimental Study

SSRN

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SSRN 2024年

作者： Miao, Yan Zhao, Qiuyang Huang, Zujie Zhao, keyu Zhao, Hao Guo, Liejin Wang, Yechun State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China Xinjin Weihua Institute of Clean Energy Research Foshan528216 China

High water cut poses a formidable challenge for heavy oil reservoirs, necessitating a strategy to enhance oil recovery. This study introduces a green-efficient approach - Supercritical Water Flooding (SCWF), suitable for sandstone heavy oil reservoirs with high water cut, compared to conventional subcritical water flooding and steam flooding. A novel experimental system (450°C,30MPa) was established to conduct SCWF experiments for heavy oil from Shengli Oilfield. The results showed that SCWF at 400°C and 25MPa had the recovery factor of 96.27% and the viscosity reduction rate of 61.6% for GD heavy oil. The dynamic process of SCWF is divided into three stages: pressure rising drainage stage, heating and depressurization stage, and miscible flooding stage. Analysis indicates that the high diffusivity, solubility and reactivity of supercritical water make thermal fluid breakthrough, miscible flooding and aquathermolysis reactions become the key mechanisms for high oil recovery and in situ upgrading of SCWF for high water cut heavy oil reservoirs. © 2024, The Authors. All rights reserved.

关键词： Crude oil

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Numerical Investigation on Isolated Moving Charged Droplet Evaporation in Electrostatic Field with Highly Volatile R134a 15

Numerical Investigation on Isolated Moving Charged Droplet E...

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15th Triennial International Conference on Liquid Atomization and Spray Systems, ICLASS 2021

作者： Tian, Jiameng Wang, Junfeng Chen, Bin School of Energy and Power Engineering Jiangsu University Zhenjiang China State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an China

Fundamental investigations of the charged droplet evaporation are helpful in enhancing the cooling capability and advancing the electrostatic spray model, whereas the corresponding data with the highly volatile R134a under electric field is very scarce. In this work, an improved evaporation model accounting for the effects of the corona wind, Coulombic fission and electric force under the electric field was developed and validated to evaluate the importance of the electric field on the moving charged R134a droplet evaporation for the first time. Results demonstrated that the electrostatic field can improve the charged droplet evaporation by means of the heat and mass transfer enhancement by the corona wind and counteracting the drag force from air. The droplet lifetime was shortened by 20.8% (from 105.6 ms to 83.6 ms) when the applied voltage increased from 0 kV to 10 kV. Exponential decay in the charged droplet lifetime when the applied voltage increased was observed. © 2021 ICLASS 2021 - 15th Triennial International Conference on Liquid Atomization and Spray Systems. All Rights Reserved.

关键词： Drops

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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

SSRN

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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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Operational Flexibility Analysis of 1100 MW Supercritical Coal-Fired power Plants during Load Cycling Transient Processes

Operational Flexibility Analysis of 1100 MW Supercritical Co...

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IEEE Asia power and Energy engineering Conference (APEEC)

作者： Lu Chen Dengliang Wang Jie Ma Yongliang Zhao Weixiong Chen State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University China Energy Engineering Group Northwest China Electric Power Test Research Institute Co. LTD Xi’an China State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an China Ulatt Power Plant of Northern United Power Co. Ltd Bayannur

Operational flexibility of the coal-fired power plants must be improved so as to deal with the unpredictability of renewable energy in the future. In this study, a 1100 MW supercritical coal-fired power plant was selected, and dynamic simulation model of the unit was established via GSE software. Moreover, control model was added. Dynamic response characteristics of key thermal parameters under different power ramp rates in the region of 30%-100% THA was obtained. The cumulative standard coal consumption rate and integral absolute error were selected as the economic evaluation index of the thermal system. The results show that the maximum power ramp rate of the unit in each region during loading up is smaller than that during loading down. In the loading down process, the standard coal consumption rate of the unit firstly decreases with the reduction of output power. When the load of the unit drops to the target load, the standard coal consumption rate rises to a stabler stage. The process of loading up is the contrary. The cumulative standard coal consumption rate of coal-fired power plant is the lowest, only 275 g•(kW•h) -1 during the loading down process of 100%-75% THA. However, the cumulative standard coal consumption rate is the highest, reaching 311 g(•kW•h) -1 during the loading up process of 30%-50% THA. Due to the output power of the unit fluctuating greatly, the integral absolute error of the unit is much higher than that of other load cycling transient processes during the loading up process of 50%-75% THA and 30%-50% THA. It can be concluded that the loading up process of the unit is more difficult to control stably. This study can provide sufficient theoretical and data guidance for improving the operational flexibility of the coal-fired power plants.

关键词： Economics Fluctuations Loading Process control Coal Software Transient analysis

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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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Alkaline Pulping Catalyzed Ordered Conversion of Bark in Supercritical Water

SSRN

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SSRN 2023年

作者： Ge, Hui Huang, Yong Liu, Zhaozheng Liu, Fan Chen, Yu-Nan Guo, Liejin State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University No.28 Xianning West Road Xi’an710049 China

The hydrophilicity of lignocellulosic biomass hinders the application of a high concentration slurry for supercritical water gasification, thereby reducing the efficiency of gasification and energy self-sufficiency. A pretreatment method of alkaline pulping with KOH and NaOH was proposed considering initial pressure to prepare high concentration slurry. In this study, bark as lignocellulosic biomass specimen, whose 30wt% and 40wt% slurries, with favorable rheology and stability, was prepared via alkaline pulping successfully. The most economical conditions were 180 °C and 24% KOH addition. The bark macromolecules were restructured due to the hydrolysis of cellulose and lignin by breaking down the hydrogen bond and ether bond with trivial hydrocarbon matrix loss. The scattered crystal growth being created and a reduction of hydrophilic groups facilitated the uniform premixing of bark and water, which is improved by a stable charge system furtherly. Additionally, metal ions could be deposited onto the bark surface during alkaline pulping. The chemical modification leading by alkaline pulping achieved the premixing of feedstock and water to form bark slurry. The conversion barrier was decreased to fulfill the ordered conversion. Consequently, the commendable catalytic effect of 95.66% gasification efficiency was displayed for 40wt% bark slurry with trivial coke yield. The functional groups of organic matter in the slurry were significantly converted into the gas phase, and lattice oxygen was produced in the solid product. The maximum alkali recovery of 80% was achieved at 580 °C. The successful completion of this research affirms the dominance of the pulping-alkali recovery-gasification method for expanding the application of SCWG of lignocellulosic biomass in large engineering projects. © 2023, The Authors. All rights reserved.

关键词： Chemical modification

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Simulation Study on the Dynamic Characteristics of Natural Circulation Coupled Phase Change Material for Equal Height Difference Passive Containment Cooling System

SSRN

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SSRN 2024年

作者： Chen, Weixiong Huang, Yufan Wang, Han Yang, Xiaohu Li, Shaodan Zhao, Quanbin Chong, Daotong State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China Wuhan Second Ship Design and Research Institute Wuhan430205 China

The passive containment cooling system (PCCS) plays a significant role in ensuring the safety of nuclear power plants. To further reduce peak pressure in the containment during a loss of coolant accident (LOCA), phase change materials (PCMs) are utilized to improve the system’s cooling effectiveness. The dynamic simulation model of PCCS has been developed using Apros software. This article focuses on examining the system’s dynamic characteristics related to various tube startup methods and comparatively analyzing the impact of different PCM thicknesses on heat transfer capacity. The results indicate that post-accident, PCM significantly suppresses peak pressure in the containment. Under the full tube startup method with 4 mm PCM, the peak pressure decreases to 1.75 MPa, whereas under the empty tube startup method, it is reduced to 1.69 MPa. With natural circulation empty tube startup method, PCM can reduce pressure change intensity in the containment but negatively affects natural circulation heat transfer. Although the full tube startup method underperforms the empty tube startup method on suppressing peak pressure, PCM can positively affect natural circulation heat transfer in the early stages of the accident. Empty tube startup offers the advantages of higher heat transfer capacity and lighter weight, making it the optimal choice for ocean nuclear platforms. Additionally, the higher peak power of PCM heat transfer under the empty tube startup method indicates that system can withstand larger thermal shocks. © 2024, The Authors. All rights reserved.

关键词： Thermoelectric equipment

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Improved filtered mesoscale interphase heat transfer model

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Particuology 2021年第4期19卷 176-186页

作者： Yu Li Yaxiong Yu Chi Zhang Zheqing Huang Qiang Zhou School of Chemical Engineering and Technology Xi’an Jiao Tong UniversityXi’an 710049China AVIC Xi’an Flight Automatic Control Research Institute Xi’an 710049China State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiao Tong UniversityXi’an 710049China

Mesoscale structures that form in gas-solid flows considerably affect interphase heat transfer.A filtered interphase heat transfer model accounts for the effects of unresolved mesoscale structures is required in coarse-grid *** the literature,researchers obtain the filtered interphase heat transfer coefficient using a correction(Q)to the microscopic interphase heat transfer *** models are based on filtered data in the range 01 is *** percentage can reach approximately 20%when the dimensionless filter size is smaller than 1.028(66.7×the particle diameter).We proposed an improved filtered interphase heat transfer model by considering the data in the range Q<0 and Q>*** evaluated the predictive power of our model in an a priori *** model has much better performance than other models when the dimensionless filter size△<8.222.

关键词： Gas-solid flows Two-fluid model Interphase heat transfer Filtered model Mesoscale

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