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Effect of operational and geometric parameters on the Hydrodynamics of a Wurster coater:A CFD-DEM study

Particuology 2024年第2期85卷 62-76页

作者： Yinqiang Song Tuo Zhou Ruiqi Bai Man Zhang Hairui Yang Department of Energy and Power Engineering Tsinghua UniversityBeijing100084China Key Laboratory for Thermal Science and Power Engineering of Ministry of Education Tsinghua UniversityBeijing100084China State Key Laboratory of Power System and Generation Equipment Tsinghua UniversityBeijing100084China

A coupled CFD-DEM method was used to study the Hydrodynamics of a Wurster coater.Firstly,the CFD part of the model was validated by the accurate prediction of the pressure drops over a pseudo-2D fluidized bed under various gas velocities.The effect of gas velocity,gap height,tube length and batch volume of the particles on the cycle time and the residence time of the particles was thoroughly investigated.The central jet gas velocity ui was found to speed up the particle cycle but undermine the coating efficiency.The gas velocity at the horizontal transport zone u2 was able to promote the horizontal transport of the particles but should not be too high,otherwise,it would obstruct the normal falling back of the particles in the downward zone.Big gap heights would decrease the coating efficiency but tube length had little impact on that.The increment of batch volume would commonly abase the cycle time and the working efficiency under a given u1.The de-fluidization problem arose when the batch volume increased to 550 mL.However,this problem could be swept out by the optimization of u1 and u2.In a mixture of different sizes,the coarse particles enjoyed higher coating efficiency and could travel closer to the nozzles.This may shield the fine particles from getting enough coating liquids,and thus coarse particles and fine particles were not recommended to get coated in the same batch.

关键词： Numerical simulation CFD-DEM Wurster coater Hydrodynamics Cycle time Residence time

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CPFD modeling of Hydrodynamics,combustion and NOx emissions in an industrial CFB boiler

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Particuology 2023年第10期81卷 174-188页

作者： Jian Chang Xinrui Ma Xin Wang Xiaohang Li School of Energy Power and Mechanical EngineeringNorth China Electric Power UniversityBeijing102206China Bluestar(Beijing)Chemical Machinery Co. LtdBeijing100176China

The ultra-low NOx emission requirement(50 mg/m^(3))brings great challenge to CFB boilers in China.To further tap the NOx abatement potential,full understanding the fundamentals behind CFB boilers is needed.To achieve this,a comprehensive CPFD model is established and verified;gas-solid flow,combustion,and NOx emission behavior in an industrial CFB boiler are elaborated;influences of primary air volume and coal particle size on furnace performance are evaluated.Simulation results indicate that there exists a typical core-annular flow structure in the boiler furnace.Furnace temperature is highest in the bottom dense-phase zone(about 950℃)and decreases gradually along the furnace height.Oxygen-deficient combustion results in high CO concentration and strong reducing atmosphere in the lower furnace.NOx concentration gradually increases in the bottom furnace,reaches maximum at the elevation of secondary air inlet,and then decreases slightly in the upper furnace.Appropriate decreasing the primary air volume and coal particle size would increase the CO concentration and intensify the in-furnace reducing atmosphere,which favors for NOx reduction and low NOx emission from CFB boilers.

关键词： Hydrodynamics Combustion NOx emission CFB boiler CPFD

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Hydrodynamics and OCM reaction performance in a bubbling fluidized bed reactor and a riser reactor

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Particuology 2024年第3期86卷 188-204页

作者： Min Cai Shuangzhu Kong Sheng Chen Mengxi Liu Chunxi Lu State Key Laboratory of Heavy Oil Processing China University of PetroleumBeijing102249China China Special Equipment Inspection and Research Institute Beijing102249China

The reasonable reactor design is of great importance for increasing the C_(2) yield(C2H4 and C2H6)of the oxidative coupling of methane(OCM),and the OCM reactor should remove the heat released in reactions quickly and efficiently and minimize the consecutive reaction of ethylene to carbon oxides.The fluidized bed reactor is characterized by excellent heat transfer,superior mass transport,and large handling capacity,while fewer studies focused on large-scale fluidized bed reactors for the OCM reaction.Therefore,large cold-model experiments and computational fluid dynamics simulations were conducted to investigate Hydrodynamics and the OCM reaction performance in a large-scale bubbling fluidized bed(BFB)and a large-scale riser.In the BFB reactor,consecutive reactions of ethylene are acute because of the strong gas back-mixing,high solids holdup,and non-uniform solids distribution.While the consecutive reactions of ethylene are negligible due to the plug flow structure and low solids holdup in the riser reactor.Further,both reactors can achieve isothermal operation for the OCM process.The C_(2) selectivity of 45.4% and C_(2) yield of 21.1% are obtained in the riser reactor,increasing by 20.3% and 5.8% individually than that in the BFB reactor.This study provides useful information and reference to the OCM reactor designandcommercialization.

关键词： Oxidative coupling of methane Bubbling fluidized bed reactor Riser reactor Hydrodynamics Isothermal operation

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Molecular force mechanism of Hydrodynamics in clay nanopores

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浙江大学学报(英文版)A辑:应用物理与工程 2023年第9期24卷 817-827页

作者： Shengjie WEI Yuchao LI Peng SHEN Yunmin CHEN MOE Key Laboratory of Soft Soils and Geoenvironmental Engineering College of Civil Engineering and ArchitectureZhejiang UniversityHangzhou 310058China

Nanopores are prevalent within various clay morphologies,and water flow in clay nanopores is significant for various engineering applications.In this study,we performed non-equilibrium molecular dynamics(NEMD)simulations to reveal the molecular force mechanisms of water flow in clay nanopores.The water dynamic viscosity,slip length,and average flow velocity were obtained to verify the NEMD models.Since the water confined in the nanopores maintained a dynamic mechanical equilibrium state,each water lamina can be regarded as a simply supported beam.The applied driving force,the force from clay crystal layers,the force from compensating sodium ions,and the force from other water laminae were further calculated to investigate the force mechanisms.The van der Wals barrier above the surface and hydraulic gradient lead to distribution differences in water oxygen atoms,which contribute to a net van der Waals resistance component of the force from clay crystal layers.Meanwhile,the water molecules tend to rotate to generate the electrostatic resistance component of the force from clay crystal layers and balance the increasing hydraulic gradient.Due to the velocity difference,the water molecules in the slower lamina have a higher tendency to lag and generate a net electrostatic resistance force as well as a net van der Waals driving force on the water molecules in the faster lamina,which together make up the viscous force.

关键词： Molecular dynamics Hydrodynamics Clay Nanopore Molecular force Boundary effect Viscous force

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Microfluidic separation of particles by synergistic effect of geometry-induced Hydrodynamics and magnetic field

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Chinese Chemical Letters 2024年第2期35卷 380-385页

作者： Du Qiao Hongxia Li Weiping Zhu Lili Zhu Danyang Zhao Honglin Li Key Laboratory for Precision & Non-traditional Machining Technology of Ministry of Education Dalian University of TechnologyDalian 116023China Shanghai Key Laboratory of New Drug Design School of PharmacyEast China University of Science and TechnologyShanghai 200237China Lingang Lab Shanghai 200031China

Microfluidic combined with magnetic field have been demonstrated to be the promising solutions for fast and low-damage particles separation.However,the difficulties in the precise layout of magnets and accurate prediction of particle trajectories lead to under and over separation of target particles.A novel particle separation lab-on-chip(LOC)prototype integrated with microstructures and micropolar arrays is designed and characterized.Meanwhile,a numerical model for the separation of magnetic particles by the synergistic effect of geometry-induced Hydrodynamics and magnetic field is constructed.The effect of geometry and magnetic field layout on particle deflection is systematically analyzed to implement accurate prediction of particle trajectories.It is found that the separation efficiency of magnetic particles increased from 50.2%to 91.7%and decreased from 88.6%to 85.7%in the range of depth factors from 15µm to 27µm and width factors from 30µm to 60µm,respectively.In particular,the combined effect of the offset distance of permanent magnets and the distance from the main flow channel exhibits a significant difference from the conventional perception.Finally,the developed LOC prototype was generalized for extension to arbitrary systems.This work provides a new insight and robust method for the microfluidic separation of magnetic particles.

关键词： Microfluidic Particle separation Synergistic effect Hydrodynamics Magnetic field Numerical calculation

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Hydrodynamics of high-speed robots driven by the combustion-enabled transient driving method

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2022年第10期23卷 820-831页

作者： Yang YANG Yingzhong LOU Guanzheng LIN Zhiguo HE Pengcheng JIAO Hainan Institute Zhejiang UniversitySanya 572000China Institute of Port Coastal and Offshore EngineeringOcean CollegeZhejiang UniversityZhoushan 316021China Department of Civil and Environmental Engineering University of WashingtonSeatleWA98195USA Engineering Research Center of Oceanic Sensing Technology and Equipment of Ministry of Education Zhejiang UniversityZhoushan316021China Department of Electronic Engineering Faculty of EngineeringThe Chinese University of Hong KongHong Kong 999077China

Underwater vehicles play important roles in underwater observation, ocean resource exploration, and sample collection.Soft robots are a unique type of underwater vehicles due to their good environmental adaptability and motion flexibility, although they are weak in terms of actuation and response ability. The transient driving method(TDM) was developed to resolve these shortcomings. However, the interaction between the robots’ swift motions and flow fields has not yet been fully studied. In this study, a computational fluid dynamic model is developed to simulate the fluid fields disturbed by transient high-speed motions generated by the robots. Focusing on the dependence of robot dynamics on thrust force and eccentricity, typical structures of both flow and turbulence fields around the robots are obtained to quantitatively analyze robot kinematic performance, velocity distribution, vortex systems, surface pressure, and turbulence. The results demonstrate the high-speed regions at the robots’ heads and tails and the vortex systems due to sudden expansion, indicating a negative relationship between the maximum fluid velocity and eccentricity. The reported results provide useful information for studying the environmental interaction abilities of robots during operating acceleration and steering tasks.

关键词： Underwater vehicle Computational fluid dynamics(CFD) Robotics Transient driving method(TDM) Combustion actuation Hydrodynamics

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A brief discussion on offshore wind turbine Hydrodynamics problem

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Journal of Hydrodynamics 2022年第1期34卷 15-30页

作者： Zhi-teng Gao Xing-ya Feng Zi-tan Zhang Zheng-liang Liu Xiao-xia Gao Li-jun Zhang Shan Li Ye Li Multi-function Towing Tank School of Naval ArchitectureOcean and Civil EngineeringShanghai Jiao Tong UniversityShanghai200240China Department of Ocean Science and Engineering Southern University of Science and TechnologyShenzhen518055China Hebei key Laboratory of Low Carbon and High Efficiency Power Generation Technology Department of Power EngineeringNorth China Electric Power UniversityBaoding071003China

Recently, offshore renewable energy has received significant attentions from most oceanic countries. Its multiple disciplinary nature appears as a hot research spot. Among those resources, offshore wind has been experiencing a rapid growth with strong industrial and governmental support. Among the research topics related to offshore wind turbine, those related to efficiency and safety issue receive most attentions, and they cover Hydrodynamics, aerodynamics, structural dynamics, elasticity and so on. Hydrodynamics is considered as the key of these research for offshore wind turbine. This is not only because it is the fundamental of ocean engineering, but also it is similar to low speed aerodynamics which is the key of wind turbine rotor. In order to provide a comprehensive understanding of the important problems of offshore wind turbine Hydrodynamics, we briefly review the evolution of offshore wind turbine and discuss the Hydrodynamics problem associated with the research and development activities.

关键词： Offshore renewable energy offshore wind turbine Hydrodynamics low speed aerodynamics aero-hydro dynamics coupling

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Some topics on the smooth particle Hydrodynamics method

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Acta Mechanica Sinica 2023年第2期39卷 1-2页

作者： Fei Xu Renato Vacondio School of Aeronautics Northwestern Polytechnical UniversityXi'an 710072China Department of Engineering and Architecture University of ParmaParmaItaly

The smooth particle Hydrodynamics(SPH)method is one of the earliest meshfree methods,first proposed in 1977[1,2],to solve astrophysical problems.In the past years,as a Lagrangian,particle method,the SPH method has been widely applied in computational engineering sciences.It provides novel insights for solving complex problems in fluid dynamics and solid mechanics involving large deformations.

关键词： problems. particle Hydrodynamics

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三体船构型水动力性能试验研究

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Journal of Marine Science and Application 2022年第3期21卷 46-55页

作者：贾敬蓓宗智 School of Navigation and Naval Architecture Dalian Ocean UniversityDalian 16023China School of Naval Architecture Engineering Dalian University of TechnologyDalian 116024China State Key Laboratory of Structural Analysis for Industrial Equipment Dalian 116024China

This paper presents experimental results on configuration Hydrodynamics.Three models are used in the model tests,which are typical of hard,round,and soft chines.Although specific values are different,the influence patterns are similar in the three ship models.A set of different outrigger positions is investigated in calm water and regular waves.A variety of interesting phenomena are observed,among which the splash resistance is the dominant component for a trimaran at high speeds(with Froude number Fr>0.6).If two small outriggers are placed inside Kelvin’s wave systems of the main hull,a strong splash appears,resulting in a significant resistance increase.Moreover,short and long waves cannot be neglected,for they may excite the motions of much smaller outriggers.This condition leads to non-vanishing heaving at high-frequency and non-normalized pitches at low frequencies.Based on the tests,three spectra of optimum configurations for resistance,longitudinal motions,and transverse motions are presented.These results reveal the optimum configurations of a trimaran hull in terms of hydrodynamic performance,thus providing a very powerful tool for optimum design of trimaran ships.

关键词： Trimaran ship Configuration Hydrodynamics Splash resistance Spectra of optimum configurations

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Hydrodynamics and mass transfer performance analysis of flow-guided trapezoid spray packing tray

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Chinese Journal of Chemical Engineering 2021年第11期34卷 59-67页

作者： Shuo Yang Jilong Zhang Jiaxing Xue Qingpeng Wu Qunsheng Li Hongkang Zhao Liqun Zhang State Key Laboratory of Chemical Resource Engineering Beijing University of Chemical TechnologyBeijing 100029China China Nuclear Power Engineering Co. LtdBeijing 100840China College of Mining Engineering Taiyuan University of TechnologyTaiyuan 030024China Key Laboratory of Carbon Fiber and Functional Polymers Ministry of EducationBeijing University of Chemical TechnologyBeijing 100029China

Distillation is the most common separation technology utilized in the petroleum and chemistry industries.Due to the wide usage of the distillation column,even a small improvement in performance may result in significant energy cost savings.Aiming to improve the Hydrodynamics and mass transfer performance,the flow-guided trapezoid spray-packing tray(FTS-PT)was designed by combining flow-guided holes and trapezoidal caps with structured packing.And the experimental measurements of the FTSPT,including pressure drop,clear liquid height,weeping,entrainment,and tray efficiency,were conducted in a 500 mm diameter plexiglass column with the air-water-oxygen system.Moreover,the performance of the FTS-PT was compared with that of new vertical sieve tray(New VST)and F1 valve tray.The results show that FTS-PT has a significant advantage in pressure drop,entrainment,and capacity.Furthermore,the calculation model of the pressure drop was derived and used for the FTS-PT with a relative deviation of less than 5%.

关键词： Flow-guided hole Spray mode Hydrodynamics Mass transfer Calculation model

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