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Simulation of gas-solid flow characteristics of the circulating fluidized bed boiler under pure-oxygen combustion conditions

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Chinese Journal of Chemical Engineering 2024年第6期70卷 9-19页

作者： Kaixuan Gao Xiwei Ke Bingjun Du Zhenchuan Wang Yan Jin Zhong Huang Yanhong Li Xuemin Liu Key Laboratory of Special equipment Safety and energy-Saving for State Market Regulation China Special Equipment Inspection&Research InstituteBeijing 100029China department of energy and Power Engineering Tsinghua UniversityBeijing 100084China School of Electrical and Power Engineering Taiyuan University of TechnologyTaiyuan 030024China

Under the pressure of carbon neutrality,many carbon capture,utilization and storage technologies have witnessed rapid development in the recent years,including oxy-fuel combustion(OFC)***,the conventional OFC technology usually depends on the flue gas recirculation system,which faces significant investment,high energy consumption,and potential low-temperature corrosion *** these deficiencies,the direct utilization of pure oxygen to achieve particle fluidization and fuel combustion may reduce the overall energy consumption and CO_(2)-capture *** this paper,the fundamental structure of a self-designed 130 t·h^(-1) pure-oxygen combustion circulating fluidized bed(CFB)boiler was provided,and the computational particle fluid dynamics method was used to analyze the gas-solid flow characteristics of this new-concept boiler under different working *** results indicate that through the careful selection of design or operational parameters,such as average bed-material size and fluidization velocity,the pure-oxygen combustion CFB system can maintain the ideal fluidization state,namely significant internal and external particle ***,the contraction section of the boiler leads to the particle backflow in the lower furnace,resulting in the particle suspension concentration near the wall region being higher than that in the center ***,the upper furnace still retains the classic core-annulus flow *** addition to increasing solid circulation rate by reducing the average bed-material size,altering primary gas ratio and bed inventory can also exert varying degrees of influence on the gas-solid flow characteristics of the pure-oxygen combustion CFB boiler.

关键词： Circulating fluidized bed Pure-oxygen combustion Gas-solid flow characteristics Simulation CO_(2)capture

Design Research of a Novel Aftercool-Humidifier Concept for Humid Air Turbine Cycle

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Journal of Thermal Science 2024年第3期33卷 951-969页

作者： ZHANG Junzheng XU Zhen School of energy and Power Engineering Shandong UniversityJi’nan250061China Shandong Engineering Laboratory for High-efficiency energy Conservation and energy Storage Technology&equipment Shandong UniversityJi’nan250061China

Humid air turbine cycle(HAT)has potential of electrical efficiencies comparable to combined cycle,with lower investment cost and NO_(x) *** typical heat exchanger network of HAT consists of intercooler(if there is),aftercooler,recuperator,economizer and humidifier,which brings higher efficiency but makes the system more *** simplify HAT layout,a novel humidifier concept is proposed by integrating the aftercooler into traditional counter-current *** on this concept,a one-dimensional model including pressure drop and exergy calculation is established to distinguish the thermodynamic and hydrodynamic characteristics,and then the structural parameters,such as the number of rows and columns,tube diameter,pitch and type for a micro HAT are *** results show that the aftercool-humidifier plays the same role as original aftercooler and humidifier,and can match the in-tube air,out-tube air and water stream well with lower *** the case of micro HAT cycle,the volume of heat and mass transfer area can be reduced by 47%compared with traditional *** major thermal resistance occurred in the convection heat transfer process inside the tube;however,using enhanced tube cannot effectively improve the compactness of device.

关键词： humid air turbine cycle humidifier thermodynamic analysis one-dimensional model

Numerical study on the cavity dynamics for vertical water entries of twin spheres

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Defence Technology（防务技术） 2024年第2期32卷 459-472页

作者： Xu Wang Xujian Lyu Ruisheng Sun Dongdong Tang School of energy and Power Engineering Nanjing University of Science and TechnologyNanjing210094China Shanghai Institute of Spacecraft equipment Shanghai200240China

In this study, a three dimensional(3D) numerical model of six-degrees-of-freedom(6DOF) is applied to simulate the water entries of twin spheres side-by-side at different lateral distances and time *** turbulence structure is described using the shear-stress transport k-ω(SST k-ω) model, and the volume of fluid(VOF) method is used to track the complex air-liquid interface. The motion of spheres during water entry is simulated using an independent overset grid. The numerical model is verified by comparing the cavity evolution results from simulations and experiments. Numerical results reveal that the time interval between the twin water entries evidently affects cavity expansion and contraction behaviors in the radial direction. However, this influence is significantly weakened by increasing the lateral distance between the two spheres. In synchronous water entries, pressure is reduced on the midline of two cavities during surface closure, which is directly related to the cavity volume. The evolution of vortexes inside the two cavities is analyzed using a velocity vector field, which is affected by the lateral distance and time interval of water entries.

关键词： Twin water entries Side-by-side Cavity Numerical simulation

Advancing electrochemical drilling process via coupling of flow field and electric field in pulsating state generated by a novel tube tool

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Chinese Journal of Aeronautics 2024年第4期37卷 542-555页

作者： Liang CHENG Xiaolei CHEN Zhisen YE Yongjun ZHANG State Key Laboratory of Precision Electronic Manufacturing Technology and equipment Guangdong University of TechnologyGuangzhou 510006China Guangdong Key Laboratory of Advanced Manufacturing Technology of Marine energy equipment Guangdong University of TechnologyGuangzhou 510006China Guangzhou Key Laboratory of Nontraditional Machining and equipment Guangdong University of TechnologyGuangzhou 510006China

This paper introduces an improvement to electrochemical drilling process by coupling flow field and electric field in pulsating state. A novel tube with half-wedged shape at the end(HW-tube) is prepared, with both sidewall and wedged part of the HW-tube insulated. Only the flat part is utilized to provide electric field for electrochemical drilling. By rotating the HW-tube, both flow field and electric field in pulsating state are generated, alternating in different positions within the inter-electrode gap(IEG). The pulsating flow field enhances the mass transfer process, while pulsating electric field disperses material dissolution process and distribution of electrolytic byproducts. Both pulsating fields are coupled at the same frequency, further enhancing the electrochemical drilling process. Simulation results indicate that both flow field and electric field in pulsating state are generated. Compared to the traditional tube, the HW-tube significantly reduces the number of residual particles in IEG, and this number is further reduced by increasing the rotation speed. Experimental results reveal that the surface quality and dimensional uniformity of small hole are improved with HW-tube. With feed rate of 2.22 mm/min, a small hole with diameter of 1.52± 0.017 mm is drilled, resulting in a surface roughness of 0.331 μm.

关键词： Small holes Electrochemical drilling Tools Pulsating flow field Pulsating electric field

Preparation and Tribological Properties of Onion-like Carbon/Waterborne Polyurethane Coatings

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China Petroleum Processing & Petrochemical Technology 2024年第2期26卷 108-120页

作者： Fei Xingpeng Jiang Wuhao Wen Maosheng Xu Yong Hu Kunhong Hu Enzhu department of energy Materials and Chemical Engineering Hefei UniversityHefei 230601China Anhui Province Key Laboratory of Critical Friction Pair for Advanced equipment Hefei 230088China

Rice husk powder was used as a carbon source in a high-temperature carbonization reaction for the production of rice husk ash(RHA).Under the catalysis of ferric nitrate,onion-like carbon(OLC)nanomaterial with a particle size of approximately 200 nm was successfully prepared and incorporated into waterborne polyurethane(WPU).The tribological properties of the coatings were determined using a controlled-atmosphere tribometer(WMT-2E)under dry-friction *** the friction test,the friction mechanism was investigated by characterizing the abrasive spot surfaces of the test samples using 3D laser microscopy and scanning electron microscopy/energy dispersive *** final results demonstrated that the thermal stability of WPU composite coatings containing various concentrations of OLC nanoparticles was significantly enhanced,binding forces between coatings and steel sheets increased,and hardness improved compared to pure WPU *** tests revealed a notable enhancement in the anti-wear properties of WPU coatings due to the presence of OLC ***,the wear rate of the 1.5%OLC/WPU coating was reduced by 45.3%.The coating’s anti-wear mechanism was attributed to the improvement in the mechanical properties of WPU due to OLC,as well as OLC’s participation in the formation of a transfer film under induced friction,which protected the matrix.

关键词： biomass carbon onion-like carbon waterborne polyurethane wear transfer films

Deactivation mechanism for water splitting:Recent advances

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Carbon energy 2024年第7期6卷 53-82页

作者： Yansong Jia Yang Li Qiong Zhang Sohail Yasin Xinyu Zheng Kai Ma Zhengli Hua Jianfeng Shi Chaohua Gu Yuhai Dou Shixue Dou Hydrogen energy Institute Zhejiang UniversityHangzhouChina Institute of Process equipment Zhejiang UniversityHangzhouChina Donghai Laboratory ZhoushanChina department of Mechanical Engineering Faculty of EngineeringUniversiti MalayaKuala LumpurMalaysia Institute of energy Materials Science University of Shanghai for Science and TechnologyShanghaiChina

Hydrogen(H2)has been regarded as a promising alternative to fossil-fuel *** H2 produced via water electrolysis(WE)powered by renewable energy could achieve a zero-carbon *** attention has been focused on developing highly active catalysts to facilitate the reaction kinetics and improve the energy efficiency of ***,the stability of the electrocatalysts hampers the commercial viability of *** studies have elucidated the origin of catalyst *** this review,we first discuss the WE mechanism,including anodic oxygen evolution reaction(OER)and cathodic hydrogen evolution reaction(HER).Then,we provide strategies used to enhance the stability of *** that,the deactivation mechanisms of the typical commercialized HER and OER catalysts,including Pt,Ni,RuO_(2),and IrO_(2),are ***,the influence of fluctuating energy on catalyst degradation is highlighted and in situ characterization methodologies for understanding the dynamic deactivation processes are described.

关键词： deactivation mechanism hydrogen evolution in situ characterization oxygen evolution water splitting

Defect Engineering in Earth-Abundant Cu2ZnSnSe4 Absorber Using Efficient Alkali Doping for Flexible and Tandem Solar Cell Applications

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energy & Environmental Materials 2024年第2期7卷 253-260页

作者： Muhammad Rehan Ara Cho Inyoung Jeong Kihwan Kim Asmat Ullah Jun-Sik Cho Joo Hyung Park Yunae Jo Sung Jun Hong Seung Kyu Ahn SeJin Ahn Jae Ho Yun Jihye Gwak Donghyeop Shin Photovoltaics Research department Korea Institute of Energy Research (KIER) department of Renewable energy Engineering University of Science and Technology (UST) Korea Institute of energy Technology (KENTECH)

To demonstrate flexible and tandem device applications, a low-temperature Cu2ZnSnSe4（CZTSe） deposition process, combined with efficient alkali doping, was developed. First, high-quality CZTSe films were grown at480 °C by a single co-evaporation, which is applicable to polyimide（PI）substrate. Because of the alkali-free substrate, Na and K alkali doping were systematically studied and optimized to precisely control the alkali distribution in CZTSe. The bulk defect density was significantly reduced by suppression of deep acceptor states after the（Na F + KF） PDTs. Through the low-temperature deposition with（Na F + KF） PDTs, the CZTSe device on glass yields the best efficiency of 8.1% with an improved VOCdeficit of646 m V. The developed deposition technologies have been applied to *** the first time, we report the highest efficiency of 6.92% for flexible CZTSe solar cells on PI. Additionally, CZTSe devices were utilized as bottom cells to fabricate four-terminal CZTSe/perovskite tandem cells because of a low bandgap of CZTSe（～1.0 e V） so that the tandem cell yielded an efficiency of 20%. The obtained results show that CZTSe solar cells prepared by a low-temperature process with in-situ alkali doping can be utilized for flexible thin-film solar cells as well as tandem device applications.

关键词： alkali doping Earth-abundant Cu2ZnSnSe4 flexible solar cells four-terminal tandem cells low-temperature process

Seasonal thermal energy storage using natural structures:GIS-based potential assessment for northern China

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Building Simulation 2024年第4期17卷 561-574页

作者： Yichi Zhang Jianjun Xia Midea HVAC Heating&Ventilation equipment Co. LtdFoshan528311China Building energy Research Center Tsinghua UniversityBeijing100084China

Seasonal thermal energy storage(STES)allows storing heat for long-term and thus promotes the shifting of waste heat resources from summer to winter to decarbonize the district heating(DH)*** being a promising solution for sustainable energy system,large-scale STES for urban regions is lacking due to the relatively high initial investment and extensive land *** close the gap,this study assesses the potentials of using two naturally available structures for STES,namely valley and ground pit *** on geographical information system(GIS)methods,the available locations are searched from digital elevation model and selected considering several criteria from land uses and construction *** costs of dams to impound the reservoir and the yielded storage capacities are then quantified to guide the choice of suitable *** assessment is conducted for the northern China where DH systems and significant seasonal differences of energy demand *** total,2,273 valley sites and 75 ground pit sites are finally identified with the energy storage capacity of 15.2 billion GJ,which is much larger than the existing DH demand in northern *** results also prove that 682 valley sites can be achieved with a dam cost lower than 20 CNY/m^(3).By conducting sensitivity analysis on the design dam wall height and elevations,the choices of available natural structures are expanded but practical issues about water pressures and constructions are also ***,the identified sites are geographically mapped with nearest urban regions to reveal their roles in the DH *** general,560 urban regions are found with potential STES units and most of them have STES storage capacities larger than their own DH *** novel planning methodology of this study and publicly available datasets create possibilities for the implementations of large-scale STES in urban DH systems.

关键词： seasonal thermal energy storage geographical information system district heating water reservoir

Improvement of maximum power point tracking in photovoltaic arrays in different environments using hybrid algorithms

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Optoelectronics Letters 2024年第1期20卷 28-34页

作者： ZHANG Jiuchao REN Guangjun XUE Yuming XIA Dan WANG Jiangchao HU Zhaoshuo Institute of New energy Intelligence equipment School of Integrated Circuit Science and EngineeringTianjin University of TechnologyTianjin 300384China

When the photovoltaic(PV)system is generating PV power,the partial shading(PS)condition will cause multiple peaks in the power-voltage curve,and changes in light intensity and ambient temperature will cause the curve to *** maximum power point tracking(MPPT)methods,such as the incremental conductance(INC)method,have the problem of being trapped in the local optimal *** optimization algorithms,such as particle swarm optimization(PSO),have problems with oscillation and low tracking efficiency near the global maximum power point(GMPP).As a result,a hybrid algorithm CS-INC based on the cuckoo search(CS)algorithm and the perturb and observe(P&O)approach is proposed in this *** light intensity remains constant,the light intensity changes in steps,and the partial shade scenario are *** results show that the MPPT improves accuracy,speed,and stability.

关键词： power maximum optimization