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Effect of Intake Conditions and Nozzle Geometry on Spray Characteristics of Group-Hole Nozzle

energy engineering 2023年第7期120卷 1541-1562页

作者： Jianfeng Pan Jinpeng Hua Jiaqi Yao Abiodun Oluwaleke Ojo School of Energy and Power Engineering Jiangsu University Zhenjiang212013China

The group-hole nozzle concept is proposed to meet the requirement of nozzle hole minimization and reduce the negative impact of poor spatial spray distributions.However,there are limited researches on the effects of intake conditions and nozzle geometry on spray characteristics of the group-hole nozzle.Therefore,in this study,an accurate spray model coupled with the internal cavitating flow was established and computational fluid dynamics(CFD)simulations were done to study the effects of intake conditions and nozzle geometry on spray characteristics of the group-hole nozzle.Experimental data obtained using high-speed digital camera on the high-pressure common rail injection system was used to validate the numerical model.Effects of intake conditions(injection pressure and temperature)and nozzle geometry(orifice entrance curvature radius and nozzle length)on the flow and spray characteristics of the group-hole nozzle were studied numerically.The differences in Sauter mean diameter(SMD),penetration length and fuel evaporation mass between single-hole nozzle and group-hole nozzle under different nozzle geometry were also discussed.It was found that the atomization performance of the group-hole nozzle was better than that of the single-hole nozzle under same intake conditions,and the atomization effect of the short nozzle was better than that of the long nozzle.With increase in the orifice entrance curvature radius,the average velocity and turbulent kinetic energy of the fuel increased,which was conducive to improving the injection rate and flow coefficient of the nozzle.Meanwhile,the penetration length and SMD value rose,while evaporation mass dropped.When the ratio of the orifice entrance curvature radius(R)to the diameter of injection hole(D)was 0.12,the spray characteristics reached a constant state due to elimination of cavitation.Conclusions were made based on these.This study is expected to be a guide for the design of the group-hole nozzle.

关键词： Diesel spray characteristics group-hole nozzle coupling model

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Analysis and Economic Evaluation of Hourly Operation Strategy Based on MSW Classification and LNG Multi-Generation System

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energy engineering 2023年第6期120卷 1325-1352页

作者： Xueqing Lu Yuetao Shi Jinsong Li School of Energy and Power Engineering Shandong UniversityJinan250061China

In this study,a model of combined cooling,heating and power system with municipal solid waste(MSW)and liquefied natural gas(LNG)as energy sources was proposed and developed based on the energy demand of a large community,andMSW was classified and utilized.The systemoperated by determining power by heating load,and measures were taken to reduce operating costs by purchasing and selling LNG,natural gas(NG),cooling,heating,and power.Based on this system model,three operation strategies were proposed based on whether MSW was classified and the length of kitchen waste fermentation time,and each strategy was simulated hourly throughout the year.The results showed that the strategy of MSW classified and centralized fermentation of kitchen waste in summer(i.e.,strategy 3)required the least total amount of LNG for the whole year,which was 47701.77 t.In terms of total annual cost expenditure,strategy 3 had the best overall economy,with the lowest total annual expenditure of 2.7730×108 RMB at LNG and NG unit prices of 4 and 4.2 RMB/kg,respectively.The lower heating value of biogas produced by fermentation of kitchen waste from MSW being classified was higher than that of MSW before being classified,so the average annual thermal economy of the operating strategy of MSW being classified was better than that of MSW not being classified.Among the strategies in which MSW was classified and utilized,strategy 3 could better meet the load demand of users in the corresponding season,and thus this strategy had better thermal economy than the strategy of year-round fermentation of kitchen waste(i.e.,strategy 2).The hourly analysis data showed that the net electrical efficiency of the system varies in the same trend as the cooling,heating and power loads in all seasons,while the relationship between the energy utilization efficiency and load varied from season to season.This study can provide guidance for the practical application of MSW being classified in the system.

关键词： Municipal solid waste liquefied natural gas energy recovery combined power heating and cooling determining power by heating load net electrical efficiency energy utilization efficiency

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Current status of applying microwave-associated catalysis for the degradation of organics in aqueous phase – A review

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Journal of Environmental Sciences 2019年第7期31卷 119-135页

作者： Chao Xue Yanpeng Mao Wenlong Wang Zhanlong Song Xiqiang Zhao Jing Sun Yanxiang Wang School of Energy and Power Engineering Shandong University school of Material Science & engineering Shandong University

Interactions between microwaves and certain catalysts can lead to efficient, energy-directed convergence of a relatively dispersed microwave field onto the reactive sites of the catalyst,which produces thermal or discharge effects around the catalyst. These interactions form"high-energy sites"(HeS) that promote energy efficient utilization and enhanced in situ degradation of organic pollutants. This article focuses on the processes occurring between microwaves and absorbing catalysts, and presents a critical review of microwave-absorbing mechanisms. This article also discusses aqueous phase applications of relevant catalysts(ironbased, carbon-based, soft magnetic, rare earth, and other types) and microwaves, special effects caused by the dimensions and structures of catalytic materials, and the optimization and design of relevant reactors for microwave-assisted catalysis of wastewater. The results of this study demonstrate that microwave-assisted catalysis can effectively enhance the degradation rate of organic compounds in an aqueous phase and has potential applications to a variety of engineering fields such as microwave-assisted pyrolysis, pollutant removal,material synthesis, and water treatment.

关键词： Microwaves Catalysts High energy sites Organics degradation Aqueous phase

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A novel preheating method for the Li-ion battery using supercooled phase change materials

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Science China(Technological Sciences) 2023年第1期66卷 193-203页

作者： FANG XuanYi NONG XinLu LIAO ZhiRong XU Chao Key Laboratory of power Station energy Transfer Conversion and System of Ministry of Education School of EnergyPower and Mechanical EngineeringNorth China Electric Power UniversityBeijing 102206China

The Li-ion battery is widely used in power tools, energy storage systems, and electric vehicles. In reality, battery thermal management is essential to control the battery temperature within a specific temperature range. Although research has shown that preheating the battery at low temperatures on cold days can improve output performance significantly, few efforts have been made to study the preheating method in-depth. As a result, this research proposes two preheating designs for cylindrical batteries with supercooled phase change materials: Single-and dual-phase change material(PCM) designs. A mathematical model is developed to analyze the effect of the PCM layer’s height, thickness, and mass on the preheating effect for seven candidate PCMs with high supercooling degrees. Furthermore, the economic efficiency of the single-PCM design with different PCMs is compared. In addition, the optimal ratio of the PCMs’ height for the dual-PCM design is investigated. Eventually, the improvement of the battery’s output performance is discussed. The results reveal that the proposed designs can effectively preheat the battery with a temperature rise higher than 10°C. The single-PCM design using Li NO3·3H2O shows the best preheating ability, while CH3COONa·3H2O is the most economical. Although the dual-PCM design cannot outperform the single-PCM design, it can preheat the battery twice and show better flexibility. Compared with the battery without preheating, a 26650-format battery with the single-PCM design can prolong the operating time by 38.8 min and save the electric quantity by 2.1 A h;while they are by 42.8 min and 2.3 A h with the dual-PCM design.

关键词： preheating method Li-ion battery phase change material supercooling

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Experimental Study on the Molten Salt at Micron Scale during the Melting Process

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Journal of Thermal Science 2024年第1期33卷 70-85页

作者： TIAN Ziqian LIAO Zhirong XU Chao FANG Yongzhe JIANG Kaijun YUAN Mengdi Key Laboratory of power Station energy Transfer Conversion and System Ministry of Education of ChinaSchool of Energy Power and Mechanical EngineeringNorth China Electric Power UniversityBeijing 102206China

The investigation of the melting behaviors of the molten salt at micron scale during the melting process is critical for explaining the solid-liquid phase transition mechanism.In this paper,a novel experimental system and analysis method were proposed to study the melting process with three heating rates in the range of1-10℃/min of the solar salt at micron scale.The solid-liquid boundary morphology and phase transition kinetics of molten salt particles were focused on.Meanwhile,the correlations between liquid fraction,temperature and time under different heating rates were studied.The solid-liquid boundary morphology was depicted by the visualized experimental set-up,and the instantaneous liquid volume fraction during the non-isothermal phase transition was obtained.Then,the correlation between temperature and liquid volume fraction was proposed to reveal the evolution of the solid-liquid boundary with temperature at different heating rates.Furthermore,the non-isothermal phase transition kinetic equation was established by introducing a constant parameter(V_(a,b)),and more kinetic parameters such as 1g V_(a,b) and-lg V_(a,b)/b were studied.The results showed that the exponent b is not sensitive to the heating rate with a range of 3-5 for solar salt particles.However,the heating rate influences the value of V_(a,b) and presents a positive relationship.Besides,the non-isothermal phase transition kinetic equations at different heating rates in the range of 1-10℃/min can be quickly predicted by the proposed improved experimental test method.This study could fill the research insufficiency and provide significant guidance for future research on the solid-liquid transition mechanism of molten salts at micron scale.

关键词： molten salt non-isothermal phase transition solid-liquid boundary morphology liquid volume fraction micron scale melting process

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A switchable concentrating photovoltaic/concentrating solar power(CPV/CSP)hybrid system for flexible electricity/thermal generation

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Science China(Technological Sciences) 2023年第8期66卷 2332-2345页

作者： PAN XinYu YUAN MengDi JU Xing XU Chao Key Laboratory of power Station energy Transfer Conversion and System of Ministry of Education School of Energy Power and Mechanical EngineeringNorth China Electric Power UniversityBeijing 102206China

Due to the intermittency and indeterminacy of solar irradiance,balancing energy supply and load demand remains a challenge.This paper proposed a switchable hybrid system that combines concentrating photovoltaic/concentrating solar power(CPV/CSP)technology with thermal energy storage(TES)to achieve flexible electricity and thermal generation by adjusting the incident solar flux of photovoltaic(PV).The hybrid system can directly transfer surplus solar energy into high-quality heat for storage using a rotatable PV/heat receiver.The simulated results demonstrated that the hybrid system effectively improves power generation,optimally utilizes TES capacity,and reduces the levelized cost of electricity(LCOE).Over a selected seven-day period,the single-junction(1J)Ga As solar cells used in the hybrid system sustainably satisfied the load demand for more than five days without grid supplement,outperforming the CSP plant by an additional two days.The hybrid system utilizing the 1J Ga As with the base configuration of solar multiple(SM)of 1.26 and TES capacity of 5 h improved the annual power production and renewable penetration(RP)by 20.8%and 24.8%compared with the conventional CSP plant,respectively.The hybrid plant with monosilicon and a configuration of SM(1.8),PV ratio(1),and TES capacity(6 h)achieved an optimal LCOE of11.52$ct/k Wh and RP of 75.5%,which is 8.8%lower and 12.1%higher than the CSP plant,respectively.

关键词： concentrated photovoltaic concentrated solar power hybrid system flexible electricity/thermal ratio techno-economic analysis

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Mesoporous molecular sieve confined phase change materials with high absorption,enhanced thermal conductivity,and cooling energy charging/discharging capacity

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Frontiers of Materials Science 2024年第1期18卷 1-14页

作者： Qi Zhang Chongyang Liu Xuehong Wu Xueling Zhang Jun Song School of Energy and Power Engineering Zhengzhou University of Light IndustryZhengzhou 450007China

The biggest challenge for organic phase change materials(PCMs)used in cold energy storage is to maintain high heat storage capacity while reducing the leakage risk of PCMs during the phase transition process.This is crucial for expanding their applications in the more demanding cold storage field.In this study,novel formstable low-temperature composite PCMs are prepared with mesoporous materials,namely SBA-15 and CMK-3(which are prepared using the template method),as supporting matrices and dodecane as the PCM.Owing to the combined effects of capillary forces within mesoporous materials and interactions among dodecane molecules,both dodecane/SBA-15 and dodecane/CMK-3 exhibit outstanding shape stability and thermal cycling stability even after 200 heating/cooling cycles.In comparison to those of dodecane/SBA-15,dodecane/CMK-3 exhibits superior cold storage performance and higher thermal conductivity.Specifically,the phase transition temperature of dodecane/CMK-3 is-8.81℃ with a latent heat of 122.4 J·g^(-1).Additionally,it has a thermal conductivity of 1.21 W·m^(-1)·K^(-1),which is 9.45 times that of dodecane alone.All these highlight its significant potential for applications in the area of cold energy storage.

关键词： cold energy storage phase change material mesoporous molecular sieve CMK-3 SBA-15 cooling energy charging/discharging capacity

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A comprehensive review of recent advancements and developments in heat exchanger network synthesis techniques

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Science China(Technological Sciences) 2024年第2期67卷 335-356页

作者： XU Yue LIU WeiWei ZHANG Lu CUI Guo Min XIAO Yuan ZHANG GuanHua YANG QiGuo School of Energy and Power Engineering University of Shanghai for Science and TechnologyShanghai 200093China

The rapid development of computational technology and the increasing energy demand have improved heat exchanger network(HEN)synthesis.The HEN synthesis involves several optimizations of matches,distributions of heat loads,and stream splitting of heat units.Thus,obtaining good results at high efficiency has been the main standard for evaluating the techniques in the research area of HEN synthesis.This paper first summarizes and analyzes the main contributions of the existing HEN synthesis techniques.To compare related data quantitively,information on ten typical cases is presented in this paper.Furthermore,recently improved solutions for commonly encountered existing literature cases demonstrate the evolution and competition trends in the field of HEN synthesis.The comparison data presented in this paper not only provide a useful reference for future research but also present the optimization directions.Based on the findings of this study,it is noted that there is still a large room for improvement,and current approaches are incapable of dealing with all HEN cases.Moreover,it is still difficult to escape a local optimum and overcome structural constraints when seeking the global optimum.As a follow-up to the current work,the parallel computing mode and adaptively coordinating the ratio of global and local searching abilities are major development trends for future investigation.

关键词： heat integration heat exchanger network synthesis sequential synthesis method simultaneous synthesis method optimization techniques development optimization quality

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Numerical Investigation on the Effects of Design Parameters and Operating Conditions on the Electrochemical Performance of Proton Exchange Membrane Water Electrolysis

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Journal of Thermal Science 2023年第6期32卷 1989-2007页

作者： HASSAN Alamir H. WANG Xueye LIAO Zhirong Xu Chao Key Laboratory of power Station energy Transfer Conversion and System of MOE School of EnergyPower and Mechanical EngineeringNorth China Electric Power UniversityBeijing102206China Mechanical power engineering Department Faculty of Engineering-MattariaHelwan UniversityCairo11718Egypt

Proton exchange membrane electrolysis cell(PEMEC)is one of the most promising methods to produce hydrogen at high purity and low power consumption.In this study,a three-dimensional non-isothermal model is used to simulate the cell performance of a typical PEMEC based on computational fluid dynamics(CFD)with the finite element method.Then,the model is used to investigate the distributions of current density,species concentration,and temperature at the membrane/catalyst(MEM/CL)interface.Also,the effects of operating conditions and design parameters on the polarization curve,specific electrical energy demand,and electrical cell efficiency are studied.The results show that the maximum distribution of current density,hydrogen concentration,oxygen concentration,and temperature occur beneath the core ribs and increase towards the channel outlet,while the maximum water concentration distribution happens under the channel and decreases towards the channel exit direction.The increase in gas diffusion layer(GDL)thickness reduces the uneven distribution of the contour at the MEM/CL interface.It is also found that increasing the operating temperature from 323 K to 363 K reduces the cell voltage and specific energy demand.The hydrogen ion diffusion degrades with increasing the cathode pressure,which increases the specific energy demand and reduces the electrical cell efficiency.Furthermore,increasing the thickness of the GDL and membrane rises the specific energy demand and lowers the electrical efficiency,but increasing GDL porosity reduces the specific electrical energy demand and improves the electrical cell efficiency;thus using a thin membrane and GDL is recommended.

关键词： hydrogen production proton exchange membrane water electrolysis gas diffusion layer cell efficiency

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Numerical investigation on leakage and rotordynamic performance of the honeycomb seal with swirl-reverse rings

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Chinese Journal of Aeronautics 2022年第6期35卷 87-100页

作者： Chengjing GU Wanfu ZHANG Xingchen YANG Kexin WU Lu YIN School of Energy and Power Engineering University of Shanghai for Science and TechnologyShanghai 200093China

Honeycomb seals are a crucial component to restrict the leakage flow and improve system stability for the turbomachines and aero-engines.In this work,the leakage and rotordynamic performance of honeycomb seals with the Swirl-Reverse Ring(SRR)is predicted by employing the approach of Computational Fluid Dynamics(CFD)and the multifrequency whirling model theory.Numerical results show that the positive preswirl flow and circumferential velocity can be effectively weakened for the honeycomb seal as SRR is introduced.The obtained results also suggest that the direct stiffness,direct damping,and effective stiffness will not reduce,for the honeycomb seal is introduced to SRR.However,the honeycomb seal with SRR can significantly reduce the crosscoupled stiffness and remarkably enhance the effective damping.Meanwhile,the absolute value of negative tangential force acting on the rotor surface significantly increased for the honeycomb seal introduced SRR.Therefore,the whirling velocity of the rotor would be weakened.This phenomenon would be conducive to improve the stability of the rotor.Besides,the performance of SRR can be further enhanced when SRR possesses a smaller bending angle,and a higher arrangement density and height.

关键词： Computational Fluid Dynamics(CFD) Honeycomb seal Leakage Rotordynamic performance Stability Swirl-Reverse Ring(SRR)

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