检索结果-南通市图书馆

Performance evaluation of an improved biomass-fired cogeneration system simultaneously using extraction steam, cooling water, and feedwater for heating

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Frontiers in Energy 2022年第2期16卷 321-335页

作者： Peiyuan PAN Yunyun WU Heng Chen Beijing Key Laboratory of Emission Surveillance and Control for Thermal Power Generation North China Electric Power UniversityBeijing 102206China

An advanced cogeneration system based on biomass direct combustion was developed and its feasibility was demonstrated. In place of the traditional single heat source (extraction steam), the extraction steam from the turbine, the cooling water from the plant condenser, and the low-pressure feedwater from the feedwater preheating system were collectively used for producing district heat in the new scheme. Hence, a remarkable energy-saving effect could be achieved, improving the overall efficiency of the cogeneration system. The thermodynamic and economic performance of the novel system was examined when taking a 35 MW biomass-fired cogeneration unit for case study. Once the biomass feed rate and net thermal production remain constant, an increment of 1.36 MW can be expected in the net electric production, because of the recommended upgrading. Consequently, the total system efficiency and effective electrical efficiency augmented by 1.23 and 1.50 percentage points. The inherent mechanism of performance enhancement was investigated from the energy and exergy aspects. The economic study indicates that the dynamic payback period of the retrofitting project is merely 1.20 years, with a net present value of 5796.0 k$. In conclusion, the proposed concept is validated to be advantageous and profitable.

关键词： biomass-fired cogeneration district heat production system absorption heat pump extraction steam cooling water low-pressure feedwater

A coal-fired power plant integrated with biomass co-firing and CO_(2) capture for zero carbon emission

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Frontiers in Energy 2022年第2期16卷 307-320页

作者： Xiaojun XUE Yuting WANG Heng Chen Gang XU Beijing Key Laboratory of Emission Surveillance and Control for Thermal Power Generation North China Electric Power UniversityBeijing 102206China

A promising scheme for coal-fired power plants in which biomass co-firing and carbon dioxide capture technologies are adopted and the low-temperature waste heat from the CO_(2) capture process is recycled to heat the condensed water to achieve zero carbon emission is proposed in this paper.Based on a 660 MW supercritical coal-fired power plant,the thermal performance,emission performance,and economic performance of the proposed scheme are evaluated.In addition,a sensitivity analysis is conducted to show the effects of several key parameters on the performance of the proposed system.The results show that when the biomass mass mixing ratio is 15.40%and the CO_(2) capture rate is 90%,the CO_(2) emission of the coal-fired power plant can reach zero,indicating that the technical route proposed in this paper can indeed achieve zero carbon emission in coal-fired power plants.The net thermal efficiency decreases by 10.31%,due to the huge energy consumption of the CO_(2) capture unit.Besides,the cost of electricity(COE)and the cost of CO_(2) avoided(COA)of the proposed system are 80.37/MWhand41.63/tCO_(2),respectively.The sensitivity analysis demonstrates that with the energy consumption of the reboiler decreasing from 3.22 GJ/tCO_(2) to 2.40 GJ/tCO_(2),the efficiency penalty is reduced to 8.67%.This paper may provide reference for promoting the early realization of carbon neutrality in the power generation industry.

关键词： coal-fired power plant biomass co-firing CO_(2)capture zero carbon emission performance evaluation

Correlation of surface features with corrosion behaviors of interstitial free steel processed by temper rolling

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2020年第1期36卷 37-44页

作者： Heng Chen Zebang He Lin Lu Institute for Advanced Materials and Technology University of Science and Technology BeijingBeijing100083China State Key Laboratory of Metal Material for Marine Equipment and Application Anshan114000China

Temper rolling,as a final manufacturing procedure,brings the change of surface features and hence affects the corrosion behaviors of interstitial-free(IF)steel.This study investigates changes in residual stress,microstructure,and surface topography of IF steel using X-ray diffraction,electron backscatter diffraction,and optical interferometric microscopy.And the synthetic influence of surface features on the corrosion process of the steel was evaluated by damp heat tests and electrochemical measurements.Results showed that low tensile and compressive residual stresses are introduced to the surface of the IF steel.Some grains had a grain orientation spread(GOS)value greater than 0.50 after temper rolling.Moreover,temper rolling caused a slight change in the surface profile of the IF steel.The compressive residual stress had an overwhelming role at the macroscopic level,in retarding the corrosion evolution process of IF steel,as well as in decreasing the average corrosion rate.And corrosion was more likely to initiate and propagate in matrices with a high GOS value,which played the determinant role at the microscopic level.Moreover,the depth of valley in the surface profile could affect the diffusion process involved in the electrode reactions,which was more likely to exert an extra influence on the corrosion rate of IF steel.

关键词： Temper rolling Surface feature Corrosion behavior Interstitial-free steel

Photocatalytic performance and dispersion stability of nanodispersed TiO2 hydrosol in electrolyte solutions with different cations

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Journal of Environmental Sciences 2020年第2期32卷 59-71页

作者： Zixiao Wang Pan Feng Heng Chen Qingliang Yu Jiangsu Key Laboratory of Construction Materials School of Materials Science and EngineeringSoutheast UniversityNanjing 211189China Department of the Built Environment Eindhoven University of Technology5600 MB Eindhoventhe Netherlands School of Civil Engineering Wuhan UniversityWuhan 430072China State Key Laboratory of High Performance Civil Engineering Materials Nanjing 210008China

The existence of electrolytes in aquatic environment on the photocatalytic performance and coagulation of nanodispersed TiO2 hydrosol and the corresponding photocatalytic alteration were investigated by studying cations(Na^+, K^+, Ca^2+, Mg^2+, and Al^3+).The photocatalysis reactions of nano TiO2 with different dosages of electrolytes were measured by monitoring the degradation of Rhodamine B(Rh B) under ultraviolet A(UV-A) irradiation over time.The results showed that the photocatalytic performance of TiO2 was improved by the presence of Al^3+, while the performance was impaired by the other tested cations.The negative influences of divalent ions on the photocatalytic performance of TiO2 were more significant than monovalent ions.The TiO2 sol dispersed stable at nano scale at low concentration of electrolyte( 0.1 mol/L) with larger increase or decrease of pH.The positive effects of Al^3+on the photodegradation rate of Rh B might relate to the strong hydrolytic action of Al^3+in aquatic solutions.The photocatalytic processes of TiO2 in the presence of all ions followed the Langmuir-Hinshelwood model, and the reaction kinetic constant was increased with the decrease of pH caused by different cations.These work suggested a new perspective about the relationship between coagulation and photocatalytic performance of TiO2 hydrosols in electrolyte with hydrolysable cations, which demonstrated that TiO2 hydrosols may be suitable as photocatalysts in aquatic environments.

关键词： Photocatalytic oxidation Nano dispersed TiO2 hydrosol Aqueous inorganic cations Stability Photocatalytic kinetic

Rarefied gas effect in hypersonic shear flows

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Acta Mechanica Sinica 2021年第1期37卷 2-17,I0002页

作者： Jie chen heng Zhou Laboratory of High-speed Aerodynamics Tianjin UniversityTianjin300072China

Recently,as aerodynamics was applied to flying vehicles with very high speed and flying at high altitude,the numerical simulation based on the Navier-Stokes(NS)equations was found that cannot correctly predict certain aero-thermo-dynamic properties in a certain range of velocity and altitude while the Knudsen number indicates that the flow is still in the continuum regime.As first noted by Zhou and Zhang(Science in China,2015),the invalidity of NS equations for such flows might be attributed to an non-equilibrium effect originating from the combined effects of gas rarefaction and strong shear in the boundary-layer flows.In this paper,we present the scope,physical concept,mathematical model of this shear non-equilibrium effect in hypersonic flows,as well as the way of considering this effect in conventional computational fluid mechanics(CFD)for engineering applications.Several hypersonic flows over sharp bodies and blunt bodies are analyzed by the proposed new continuum model,named direct simulation Monte Carlo(DSMC)data-improved Navier-Stokes(DiNS)model.

关键词： Rarefied gas effect Hypersonic shear flow Aerodynamics properties Direct simulation Monte Carlo Continuum model

Fast scanning growth of high-quality graphene films on Cu foils fueled by dimeric carbon precursor

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Nano Research 2023年第10期16卷 12246-12252页

作者： Heng Chen Xiucai Sun Xiaofeng Song Buhang chen Ziteng Ma Wanjian Yin Luzhao Sun Zhongfan Liu Center for Nanochemistry Beijing Science and Engineering Center for NanocarbonsBeijing National Laboratory for Molecular SciencesCollege of Chemistry and Molecular EngineeringPeking UniversityBeijing 100871China Beijing Graphene Institute Beijing 100095China College of Materials Science and Technology Beijing University of Chemical TechnologyBeijing 100029China College of Energy Soochow Institute for Energy and Materials InnovationS(SIEMIS)Key Laboratory of Advanced Carbon Materials and Wearable Energy Technologies of Jiangsu ProvinceSUDA-BGI Collaborative Innovation CenterSoochow UniversitySuzhou 215006China

Carbon source precursor is a critical factor governing chemical vapor deposition growth of graphene films.Methane(CH4),has been the most commonly used precursor in the last decade,but it presents challenges in terms of decomposition efficiency and growth rate.Here we thoroughly evaluated acetylene(C2H_(2)),a precursor that is probably for providing carbon dimer(C2)species,for fast growth of large-scale graphene films.We find that the graphene growth behaviors fueled by C2H_(2) exhibit unconventional localized growth behavior with significant advantages in terms of high growth rate,which mainly ascribe to the as-decomposed C2 species.Therefore,a C2-fueled scanning growth strategy is proposed,and the fast scanning growth rate of 40 cm/min was experimentally demonstrated.This growth strategy is compatible with the approach of unidirectional growth of single-crystal graphene films,and the as-grown graphene films are of high-quality.This work demonstrates a reliable and promising strategy for the rapid synthesis of high-quality graphene film and may pave the avenue to cost-effective mass production of graphene materials in the roll-to-roll system.

关键词： graphene film chemical vapor deposition fast growth carbon dimer roll-to-roll production

Multifunctional design of single-atom catalysts for multistep reactions

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Science China Chemistry 2023年第5期66卷 1241-1260页

作者： Zechuan Xu Qingcheng Zhang Zaimei Huang Heng Chen Jian Zhang Wei chen Ge Meng Dingsheng Wang Key Laboratory of Carbon Materials of Zhejiang Province College of Chemistry and Materials EngineeringWenzhou UniversityWenzhou 325035China Department of Chemistry Tsinghua UniversityBeijing 100084China

With the merits of high atom utilization,low cost,unique and tunable microstructures,as well as the particular catalytic behaviors,single-atom catalysts(SACs)have gained worldwide interest and achieved great advancements in heterogeneous catalysis recently.However,catalyzing an intricate multistep reaction is usually challenging for one single-atom center,in which case multiple catalytic sites are needed.In this review,the experimental and computational advances in the construction strategies of multi-active-site SACs will be summarized and classified as single-atom/single-atom,single-atom/nanoparticle and single-atom/support multifunctional catalysts.The microstructures of different active centers and their catalytic behaviors during catalysis will be emphatically highlighted.Moreover,the confronting challenges and opportunities of this field will be discussed.This review will place emphasis on the design of multifunctional SACs for multistep reactions,which will shed light on their further development in heterogeneous catalysis and beyond.

关键词： single-atom catalysts multifunctional catalysts multistep reactions

Influence of cycle time distribution on coating uniformity of particles in a spray fluidized bed by using CFD-DEM simulations

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Particuology 2023年第5期76卷 151-164页

作者： heng Li Daoyin Liu Jiliang Ma Xiaoping chen Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education School of Energy&EnvironmentSoutheast UniversityNanjing210096China

Cycle Time Distribution(CTD)plays a critical role for determining uniformity of particle coating in spray fluidized beds.However,the CTD is influenced by both geometrical structure and operating conditions of fluidized bed.In this study,a spray fluidized bed of coating process is simulated by a comprehensive Computational Fluid Dynamics-Discrete Element Model(CFD-DEM).To achieve different behaviors of CTD,some modifications are designed on a pseudo-2D internally circulating fluidized bed,which traditionally composes of a high-velocity upward bed and low-velocity downward bed.These modifi-cations include making the air distributor slope and/or laying a baffle in the downward bed.First,the CTD and evolution of particle size distribution under different bed structures are compared.The CTD directly influences the coating uniformity.By making the particles flowing along a parallel direction in the downward bed through the geometrical modifications,the CTD becomes narrower and the coating uniformity is significantly improved.Second,under the optimized bed structure,the influence of oper-ating conditions on the coating uniformity is studied.Properly increasing the fluidization gas velocity and the fluidization gas temperature and reducing the liquid spray rate can improve the coating uniformity.

关键词： Spray fluidized bed Particle coating Cycle time distribution CFD-DEM

Two-Level Hierarchical PCG Methods for the Quadratic FEM Discretizations of 2D Concrete Aggregate Models

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Advances in Applied Mathematics and Mechanics 2019年第6期11卷 1376-1397页

作者： Yingxiong Xiao Heng Chen Lingjie Xie Civil Engineering and Mechanics College Xiangtan UniversityXiangtan 411105HunanChina

The concrete aggregate model is considered as a type of weakly discontinuous problem consisting of three phases:aggregates which randomly distributed in different shapes,cement paste and internal transition zone(ITZ).Because of different shapes of aggregate and thin ITZs,a huge number of elements are often used in the finite element(FEM)analysis.In order to ensure the accuracy of the numerical solutions near the interfaces,we need to use higher-order elements.The widely used FEM softwares such as ANSYS and ABAQUS all provide the option of quadratic elements.However,they have much higher computational complexity than the linear elements.The corresponding coefficient matrix of the system of equations is a highly ill-conditioned matrix due to the large difference between three phase materials,and the convergence rate of the commonly used solving methods will deteriorate.In this paper,two types of simple and efficient preconditioners are proposed for the system of equations of the concrete aggregate models on unstructured triangle meshes by using the resulting hierarchical structure and the properties of the diagonal block matrices.The main computational cost of these preconditioners is how to efficiently solve the system of equations by using linear elements,and thus we can provide some efficient and robust solvers by calling the existing geometric-based algebraic multigrid(GAMG)methods.Since the hierarchical basis functions are used,we need not present those algebraic criterions to judge the relationships between the unknown variables and the geometric node types,and the grid transfer operators are also trivial.This makes it easy to find the linear element matrix derived directly from the fine level matrix,and thus the overall efficiency is greatly improved.The numerical results have verified the efficiency of the resulting preconditioned conjugate gradient(PCG)methods which are applied to the solution of several typical aggregate models.

关键词： Concrete aggregate model hierarchical quadratic elements ill-conditioned matrix algebraic multigrid method preconditioner