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Influence of suction flow control on energy extraction characteristics of flapping foil

INTERNATIONAL JOURNAL OF GREEN ENERGY 2022年第8期19卷 888-903页

作者： Wang, Jiayue Huang, Shengxian Hou, Longfeng Wang, Ying Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai Key Lab Multiphase Flow & Heat Transfer Shanghai 200093 Peoples R China

Flapping foil (FF) is a relatively new renewable energy extraction device, which has the advantages of simple structure, strong environmental adaptability and little impact on the environment. This study proposed a new FF energy extraction equipment with suction control added to the surface. Based on the moving grid technology, the effect of different suction control methods on energy extraction characteristics of FF was numerically investigated. In this paper, taking NACA0012 as the reference airfoil, the influence laws of key parameters, such as suction velocity, suction port position and suction mode on the energy extraction efficiency of FF were studied respectively. The results show that, compared with the original FF, the addition of suction control can effectively control the size of the leading edge negative effect vortex, increase the force consistent with the motion direction of the FF and its surface pressure difference, thus improving the energy extraction efficiency. In addition, the innovative change of suction mode to sinusoidal suction mode in this paper can not only enhance the stability and safety of FF operation structure, but also its energy extraction efficiency is not much different from that of FF with sudden suction control.

关键词： flapping foil energy extraction suction flow control simulation

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Theoretical and experimental evaluation on the electrical properties of multi-junction solar cells in a reflective concentration photovoltaic system

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ENERGY REPORTS 2022年 8卷 820-831页

作者： Wang, Zilong Zhang, Hua Dou, Binlin Zhang, Guanhua Wu, Weidong Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai Key Lab Multiphase Flow & Heat Transfer Shanghai 200093 Peoples R China

Solar photovoltaic systems represent an important technology for renewable energy utilization and have broad potential for application and development. However, the further development of solar photovoltaic systems is hindered by their higher generation costs. A high-concentration photovoltaic system (HCPVs) can use an inexpensive concentrator to replace solar cells;this, in turn, reduces the cost of electricity generation, because the solar cell requirement decreases for a given power. This study developed a mathematical model for multi-junction solar cell (MJSC) based on single-diode equivalent circuit, furthermore, an HCPVs with hyperboloid mirrors was established. The electrical properties for an MJSC module, including the short-circuit current (I-sc), peak power (P-m), open-circuit voltage (V-oc), fill factor (FF), and efficiency (eta) were investigated at concentration ratios between 650 X and 800 X and direct solar radiation intensities between approximately 400 W/m(2) and 730 W/m(2). Furthermore, the experimental results and theoretical values were comparatively analyzed. The results demonstrated that I-sc, V-oc,V- and P-m of MJSC module increased as the direct solar radiation raised. In contrast, the FF and eta of an MJSC module decreased as the direct solar radiation raised. As the direct solar radiation intensity was 700 W/m(2) and concentration ratio increased from 650 X to 800 X, I-sc, V-oc, and P-m increased from 1.002 A to 1.243 A, 11.095 V to 11.158 V, and 9.466 W to 11.358 W, respectively. Conversely, the FF and eta of the MJSC module decreased from 32.51 % to 31.33 % and 0.851 to 0.819, respectively. The tallied between the numerical and experimental results was evaluated, which indicated that root-mean-square error between the experimental and calculated values increased as the direct solar radiation increased.(c) 2021 The Author(s). Published by Elsevier Ltd.

关键词： Solar energy Triple-junction solar cell High-concentration photovoltaic system Hyperboloid mirrors Mathematical model

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The airfoil design and parameter optimization of the deformable micro air vehicle

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engineering COMPUTATIONS 2023年第9/10期40卷 2029-2048页

作者： Huang, Shengxian Qiu, Huihe Wang, Ying Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai Peoples R China Dept Mech & Aerosp Engn Hong Kong Peoples R China

Purpose - Since most of the existing literature do not disclose the node coordinate data of its fixed-wing aircraft airfoil, in order to develop and obtain a practical and suitable deformation airfoil for fixed-wing micro air vehicle (MAV), this paper proposes an improved airfoil design method of fixed-wing MAV based on the profile data of S5010 ***/methodology/approach - Combined with the body shape variation of the stingray in the propulsion process, the parametric study of the aerodynamic shape of the original design airfoil is carried out to explore the influence of a single parameter change on the aerodynamic performance of the airfoil. Then, according to the influence law of single parameter variation on the aerodynamic performance of the airfoil, the original airfoil is synthetically deformed by changing multiple *** - By comparing the aerodynamic performance of the multi-parameter deformed airfoil with the original airfoil, it is found that the lift coefficient of the multi-parameter deformed airfoil changes from negative to positive value when AOA = 0 degrees. When AOA = 2 degrees, the lift coefficient growth rate is the largest, which is 47.27%, and the lift-to-drag ratio is increased by 50.00%. At other angles of attack, the lift, drag, and torque coefficients of the multi-parameter deformed airfoil are optimized to some ***/value - Combined the body shape variation of the stingray in the propulsion process, the parametric study of the aerodynamic shape of the original design airfoil is carried out to explore the influence of a single parameter change on the aerodynamic performance of the airfoil.

关键词： Micro air vehicle Airfoil design Parameter optimization Deformed airfoil Aerodynamic performance

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Optimization of fin for rectangular microchannel printed circuit heat exchanger using supercritical CO2 as working fluid

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JOURNAL OF SUPERCRITICAL FLUIDS 2025年 219卷

作者： Ren, Yan Zeng, Le Zhong, Shaogeng Wu, Weidong Yang, Yingying Yang, Qiguo Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai 200093 Peoples R China Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai 200093 Peoples R China Fujian Polytech Normal Univ Sch Elect & Mech Engn Fuzhou 350300 Peoples R China

To improve the performance of printed circuit heat exchanger (PCHE) in the supercritical carbon dioxide (SCO2) Brayton cycle system, the mathematic-physical model of the heat exchange unit was established, based on a newtype rectangular microchannel PCHE (RM-PCHE) manufacturing by total-etching technology in this study. And the influence mechanism and laws on the flow and heat transfer of the different fin distributions and shapes were numerically investigate. Results showed average simulation deviations of 0.9 % for outlet temperature and 13.3 % for heat transfer quantity, meeting accuracy requirement. Uniform fin distribution at 10 mm intervals significantly reduced pressure drop and improved comprehensive heat transfer performance by 14.8 %. When elliptical and airfoil fins were selected for the hot-side and cold-side channels, the flow characteristic significantly improved and the heat transfer process became more stable, improving the single-side performance by 15.9 % and 12.3 %, respectively.

关键词： Supercritical carbon dioxide Printed circuit heat exchanger Rectangular microchannel flow and heat transfer characteristics Optimization of fin distribution and shape

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Discrete element simulation of dry adhesive granular flow in a vertical pipe

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POWDER TECHNOLOGY 2025年 460卷

作者： Gao, Xin Parteli, Eric J. R. Fan, Fengxian Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai 200093 Peoples R China Univ Duisburg Essen Fac Phys Lotharstr 1 D-47057 Duisburg Germany Univ Shanghai Sci & Technol Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai 200093 Peoples R China

The transportation and storage of granular materials with adhesive properties often involves particulate flow through narrow pipes, which is accompanied by still poorly understood dynamic behavior. Due to the difficulty in achieving a quantitative understanding of such flows based solely on experiments, here we perform particle-based numerical simulations of vertical pipe flows of adhesive granular materials using the discrete element method (DEM). Our simulations unveil different regimes of vertical pipe flow depending on the pipe-to-particle diameter ratio and the interparticle adhesive strength. Surprisingly, we find that the particle mass flow rate through the pipe increases substantially with this adhesive strength. This rather counterintuitive result is caused by an enhanced tendency of the particles to form stable agglomerates around the pipe symmetry axis, thus leading to reduced interaction of the particles with the frictional pipe walls. By contrast, incorporation of particle-wall adhesive interactions leads to exactly the opposite behavior, with such interactions dictating the granular dynamics in the pipe and leading to lower mass flow rate values compared to cohesionless flows. Furthermore, we show that the different flow regimes are associated with distinct spatiotemporal patterns of the granular solid fraction along the pipe axis (density waves). Therefore, our results provide theoretical references for future experimental research and application of adhesive granular flows through narrow pipes.

关键词： Granular flow Discrete element method Adhesive particles flow rate

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Lattice Boltzmann study of liquid water flow and freezing in the gas diffusion layer

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INTERNATIONAL JOURNAL OF HYDROGEN ENERGY 2024年 71卷 32-41页

作者： Zang, Linfeng Zhu, Xiaojing Hao, Liang Dalian Univ Technol Sch Energy & Power Engn Key Lab Ocean Energy Utilizat & Energy Conservat Minist Educ Dalian 116024 Liaoning Peoples R China Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai 200093 Peoples R China

The flow and freezing process of liquid water in the gas diffusion layer (GDL) is studied using a proposed lattice Boltzmann method that integrates the multi-component pseudo-potential model and the enthalpy-based method. The evolution of liquid water, ice, and temperature distributions inside the GDL during this process is specifically analyzed, and the effect of GDL porous structure, such as porosity and carbon fiber diameter, is discussed. Results indicate that liquid water exhibits a propensity to break through the GDL through the regions characterized by larger pores, subsequently forming a liquid droplet on the GDL surface and beginning to freeze. The freezing process extends from the droplets to the CL side through the liquid pathways within the GDL. In addition, liquid water is more prone to freezing around carbon fibers. Due to the released latent heat during freezing, the temperature at the liquid water/ice interface stabilizes at 273 K. Moreover, it is also demonstrated that a large porosity and coarse carbon fibers both facilitate the flow of liquid water into the GDL where it then freezes, leading to more serious blockage of pores by ice and liquid water.

关键词： Lattice Boltzmann method Gas diffusion layer flow and freezing Porous structure

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Effects of agglomerate structure and operating humidity on the catalyst layer performance of PEM fuel cells

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APPLIED ENERGY 2024年 355卷

作者： Dou, Shaojun Hao, Liang Wang, Qianqian Liu, Hong Dalian Univ Technol Sch Energy & Power Engn Key Lab Ocean Energy Utilizat & Energy Conservat Minist Educ Dalian 116024 Liaoning Peoples R China Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai 200093 Peoples R China

Understanding the transport mechanism in catalyst layer (CL) agglomerates is crucial to enhance Pt utilization and overall fuel cell performance. In this study, high-resolution porous agglomerates are stochastically recon-structed, and capillary condensation of water in agglomerates is directly simulated using a lattice Boltzmann pseudopotential model. On this basis, a pore-scale electrochemical model is developed to investigate the effects of agglomerate structure and operating humidity on local transport resistance and agglomerate effectiveness at different Pt loadings. The results reveal that liquid water formed above 70%RH improves the electrochemical surface area (ECSA) of agglomerates with low ionomer content. An optimum I/C of 0.4 in agglomerates is determined by balancing the activated ECSA and oxygen transport resistance. Through the comparison of local transport resistance with limiting current data, an additional oxygen dissolution resistance of 60-350 s m-1 at the pore/ionomer or ionomer/Pt interface is quantified. The lowest local transport resistance of the agglomerate is achieved at about 70%RH, while condensed water at higher humidities hampers oxygen diffusion within the agglomerate, leading to reduced Pt utilization. Agglomerate size significantly affects the local transport resis-tance only when excessive ionomer or liquid water severely blocks primary pores. Finally, a novel multiscale coupling strategy integrating the porous agglomerate sub-model with a continuous-scale CL model is proposed, offering innovative insights into comprehending the relationship between CL structure and the performance of proton exchange membrane fuel cells.

关键词： Pore -scale simulation Lattice Boltzmann method Catalyst layer Agglomerate

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Enhanced oxygen evolution reaction kinetics through biochar-based nickel-iron phosphides nanocages in water electrolysis for hydrogen production

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INTERNATIONAL JOURNAL OF HYDROGEN ENERGY 2022年第67期47卷 28782-28793页

作者： Ying, Zhi Gao, Li Zheng, Xiaoyuan Dou, Binlin Cui, Guomin Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai 200093 Peoples R China

Highly-efficient and stable non-noble metal electrocatalysts for overcoming the sluggish kinetics of oxygen evolution reaction (OER) is urgent for water electrolysis. Biomass -derived biochar has been considered as promising carbon material because of its advan-tages such as low-cost, renewable, simple preparation, rich structure, and easy to obtain heteroatom by in-situ doping. Herein, Ni2P-Fe2P bimetallic phosphide spherical nanocages encapsulated in N/P-doped pine needles biochar is prepared via a simple two-step pyrolysis method. Benefiting from the maximum synergistic effects of bimetallic phosphide and biochar, high conductivity of biochar encapsulation, highly exposed active sites of Ni2P-Fe2P spherical nanocages, rapid mass transfer in porous channels with large specific surface area, and the promotion in adsorption of reaction intermediates by high-level heteroatom doping, the (Ni0.75Fe0.25)2P@NP/C demonstrates excellent OER activity with an overpotential of 250 mV and a Tafel slope of 48 mV/dec at 10 mA/cm(2) in 1 M KOH. Also it exhibits a long-term durability in 10 h electrolysis and its activity even improves during the electrocatalytic process. The present work provides a favorable strategy for the inexpensive synthesis of biochar-based transition metal electrocatalysts toward OER, and improves the water electrolysis for hydrogen production. (c) 2022 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

关键词： Water electrolysis Oxygen evolution reaction (OER) Biochar Ni2P-Fe2P Hydrogen

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Lattice Boltzmann simulation of wetting gradient accelerating droplets merging and shedding on a circumferential surface

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engineering APPLICATIONS OF COMPUTATIONAL FLUID MECHANICS 2022年第1期16卷 1796-1812页

作者： Chen, Lu Gao, Ming Liang, Jia Wang, Dongmin Hao, Liang Zhang, Lixin Univ Shanghai Sci & Technol Sch Power Engn Shanghai Key Lab Multiphase Flow & Heat Transfer Shanghai Peoples R China

A lattice Boltzmann method (LBM) based on Shan-Chen pseudo-potential model is used to investigate the process of droplets merging and shedding on a gradient wetting circular surface. The effects of wetting gradient, radius, and radius ratio on droplet merging and shedding were mainly explored. The results show that applying a wetting gradient on the circumferential surface can accelerate the process of droplet merging and shedding. The velocity of droplets merging and shedding increase with the increase of the wetting gradient. The more hydrophilic the original surface, the better the optimization effect of accelerating drainage is by applying a wetting gradient. The radius and radius ratio significantly affect droplets merging and shedding on the gradient wetting surface. The larger the radius and radius ratio, the shorter the droplets merging and shedding time.

关键词： Droplets lattice boltzmann method wetting gradient circumferential surface shedding

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CoCx-induced interfacial octahedral Co2+sites of NiCo-LDH electrode with improved faradic reactivity toward high-performance supercapacitor

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JOURNAL OF COLLOID AND INTERFACE SCIENCE 2023年第1期651卷 602-611页

作者： Yin, Baoyi Hao, Liang Li, Xiaogan Yang, Qiguo Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai Key Lab Multiphase Flow & Heat Transfer Shanghai 200093 Peoples R China Dalian Univ Technol Sch Microelect Dalian 116024 Peoples R China

Battery-like electrode materials are characterized by large theoretical capacitance but suffer from poor surface reactivity and insufficient electroactive sites thus limiting their practical charge storage capacity. To overcome this challenge, an effective strategy for vacancy modulation on battery-like electrode materials is necessary. Herein, we report for the first time an elaborately designed three-dimensional (3D) hierarchical heterostructure consisting of CoCx@NiCo-LDH on conductive nickel foam as a freestanding supercapacitor electrode. Benefiting from the weakening of the coordination of Co-O bonds, the CoCx structure induces in-situ reconstruction of the NiCo-LDH lattice, resulting in the formation of abundant oxygen vacancies (interfacial octahedral Co2+ sites) that lower the OH- adsorption energy as determined by the density functional theory (DFT) calculation. The resulting CoCx@NiCo-LDH/NF electrode exhibits an ultrahigh rate capability (2330 mF cm-2 at 0.3 mA cm-2, with capacitance retention of 51.5 % at 30 mA cm-2) and remarkable cycling performance (capacitance retention of 81.6 % after 10,000 cycles). Additionally, the assembled asymmetric devices deliver an extremely high energy density of 246 & mu;Wh cm-2 at the power density of 798 & mu;W cm-2, with 87.8 % capacitance retention after 10,000 cycles at 8 mA cm-2. Overall, this study presents a simple yet effective strategy to construct high-performance battery-like electrodes for potential applications in energy storage, transportation, and communication.

关键词： Battery-like electrode Supercapacitor Vacancy modulation Ultrahigh rate capability

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