检索结果-南通市图书馆

Experimental investigation on flow asymmetry in solid entrance region of a square circulating fluidized bed

在线全文

学校读者我要写书评

暂无评论

Particuology 2009年第6期7卷 483-490页

作者： Zhengyang Wang Shaozeng Sun Hao Chen Qigang Deng Guangbo Zhao Shaohua Wu combustion Engineering Research Institute Harbin Institute of Technology Harbin 150001 China

To study the influence of back feeding particles on gas-solid flow in the riser, this paper investigated the flow asymmetry in the solid entrance region of a fluidized bed by particle concentration/velocity measurements in a cold square circulating fluidized beds （CFB）. The pressure drop distribution along the riser and the saturation carrying capacity of gas for Geldart-B type particles were first analyzed. Under the condition of u0 = 4 m/s and Gs = 21 kg/（m^2 s）, the back feeding particles were found to penetrate the lean gas-solid flow near the entrance （rear） wall before reaching the opposite （front） wall, thus leading to a relatively denser region near the front wall in the bottom bed. Higher solid circulation rate （u0 =4 m/s, Gs = 33 kg/（m^2 s）） resulted in a higher particle concentration in the riser. However the back feeding particles with higher momentum increased the asymmetry of the particle concentration/velocity profile in the solid entrance region. Lower air velocity （u0 =3.2 m/s） and Gs =21 kg/（m2 s）, beyond the saturation carrying capacity of gas, induced an S-shaped axial solid distribution with a denser bottom zone. This limited the penetration of the back feeding particles and forced the flnidizing air to flow in the central region, thus leading to a higher solid holdup near the rear wall. Under the conditions of uo = 4 m/s and Gs = 21 kg/（m^2 s）, addition of coarse particles （dp= 1145 μm） into the bed made the radial distribution of solids more symmetrical.

关键词： Square circulating fluidized bed Solid entrance region flow asymmetry Experimental investigation

Experimental Investigation on Active Cooling for Ceramic Matrix Composite

在线全文

学校读者我要写书评

暂无评论

Defence Technology（防务技术） 2009年第2期5卷 102-105页

作者：彭丽娜何国强刘佩进 National Key Laboratory of combustion Flow and Thermo-structureNorthwestern Polytechnical University

Compared with conventional materials,the active cooling ceramic matrix composite used in ramjet or scramjet makes their structures lighter in mass and better in *** this paper,an active and a passive cooling refractory composite specimens are designed and tested with an experimental facility composed of multilayer smale scale cooling penel which consists of a water cooling system and a ceramic matrix composite specimen,and a gas generator used for providing lower and higher transfer rate gases to simulate the temperatures in combustion chamber of *** active cooling specimen can continuously suffer high surface temperature of 2 000 K for 30 s and that of 3 000 K for 9.3 s,*** experiment results show that the active cooling composite structure is available for high-temperature condition in ramjet.

关键词：陶瓷基复合材料主动冷却实验冲压发动机气体发生器装置组成冷却结构水冷却系统

Direct Numerical Simulation of Incompressible flows in a Zero-Pressure Gradient Turbulent Boundary Layer

在线全文

学校读者我要写书评

暂无评论

Advances in Applied Mathematics and Mechanics 2010年第4期2卷 503-517页

作者： Chuanta Lin Zuojin Zhu Multiphase Reactive flow Division Department of Thermal Science and Energy EngineeringUSTCHefei230026China

Direct numerical simulation(DNS)of incompressible flows in a zeropressure gradient turbulent boundary layer(TBL)is conducted by a finite difference method in which a fourth order upwind scheme is applied to discretize the convective terms while a re-scaling approach is used to set inlet flow *** Reynolds numbers based on free flow velocity and momentum thickness at the recycle section are respectively 687,1074,and *** DNS has obtained favorable results indicating that the turbulence statistics is quite satisfactory as compared with the existing numerical and experimental *** three dimensional turbulent structures at the momentum thickness Reynolds number of 1430 in several different instants are illustrated by the iso-surface of swirl strength square(the square of imaginary part of the complex eigenvalue of velocity gradient tensor)together with velocity vectors in three different cross *** is found that there are three kinds of vortical structures:quasi-symmetrical and asymmetrical hairpin vortices,and worm-like *** DNS based on the numerical method can certainly reveal the main characteristics of the TBL flows at the given Reynolds numbers.

关键词： Direct numerical simulation incompressible boundary layer flows hairpin vortex worm-like vortex

A New Method of Simulating Fiber Suspensions and Applications to Channel flows

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Physics Letters 2012年第6期29卷 189-192页

作者： YANG Wei ZHOU Kun department of Mechanics Zhejiang UniversityHangzhou 310027 Clean combustion Research Center King Abudullah University of Science and TechnologyThuwalSaudi Arabia

A successive iteration method is proposed to numerically simulate fiber *** computational field is discretized with the collocated finite volume method,and an ergodic hypothesis is adopted to gready accelerate the solution to the Fokker-Planck *** method is employed in channel flows with different fiber volume fractions and aspect ratios,and its effectiveness is *** numerical results show that the existence of fibers significantly changes the pressure distribution,and the fiber aspect ratio has a greater effect on the velocity profile than on the volume *** the center of the channel,the velocity increases along the streamwise direction,while the velocity near the wall decreases *** uncoupling and coupling solutions of the additional stress of the fiber suspensions are quite different.

关键词： equation suspensions iteration

Experimental Investigation on Ablation Characteristic of EPDM Insulator in Different Gas Environments

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Defence Technology（防务技术） 2010年第2期6卷 109-113页

作者：王书贤何国强李江刘佩进 National Key Laboratory of combustion Flow and Thermal-structureNorthwestern Polytechnical University

Some ablation experiments of Ethylene-Propylene-Diene Monomer(EPDM)insulator were carried out in quasi-static low temperature gas environment,gas-phase environment,two-phase environment with Al2O3 grain and high concentration Al2O3 grain gas *** charring ablation rate,thickness,surface morphology and main ingredient of the charring layer were *** experiment results show that the main influent factors for the charring ablation rate are the gas temperature,grain concentration and state of grain impact;the main influent factors for the charring layer thickness are the gas velocity and environment pressure;and the process of SiO2 migrating in the charring layer occur commonly in different gas *** provide a foundation for the ablation mechanism research and modeling of EPDM insulator.

关键词： propulsion system of aviation and aerospace EPDM insulator experiment environment charring ablation rate charring layer thickness surface morphology ingredient

Prediction of the Resonance Characteristics of combustion Chambers on the Basis of Large-Eddy Simulation

在线全文

学校读者我要写书评

暂无评论

Journal of Thermal Science 2005年第2期14卷 156-161页

作者： Franco MAGAGNATO Balázs PRITZ Horst BCHNER Martin GABI department of Fluid Machinery University of Karlsruhe GermanyDepartment of Fluid Machinery University of KarlsruheGermanyEngler-Bunte-Institute/Division for Combustion Technology University of KarlsruheGermanyDepartment of Fluid Machinery University of KarlsruheGermany

In the last few years intensive experimental investigations were performed at the University of Karlsruhe to develop an analytical model for the Helmholtz resonator-type combustion system. In the present work the resonance characteristics of a Helmholtz resonator-type combustion chamber were investigated using large-eddy simulations (LES), to understand better the flow effects in the chamber and to localize the dissipation. In this paper the results of the LES are presented, which show good agreement with the experiments. The comparison of the LES study with the experiments sheds light on the significant role of the wall roughness in the exhaust gas pipe.

关键词： compressible large-eddy simulation combustion instabilities oscillating flow damping ratio.

Measurement and characterization of bulk nanobubbles by nanoparticle tracking analysis method

在线全文

学校读者我要写书评

暂无评论

Journal of Hydrodynamics 2022年第6期34卷 1121-1133页

作者： Xiao-tong Ma Ming-bo Li Chao Sun Center for combustion Energy Key Laboratory for Thermal Science and Power Engineering of Ministry of EducationDepartment of Energy and Power EngineeringTsinghua UniversityBeijing100084China

The size of the bulk nanobubbles(typically 100 nm-200 nm in diameter)is below the optical resolution of the typical microscopes,which makes it difficult to make a direct observation of them and differentiate between the nanoparticles and the *** this work,a nanoparticle tracking analysis(NTA)system is developed for tracking and sizing the bulk nanobubbles,and more broadly,the Brownian diffusing *** demonstrate the capabilities of the NTA in characterizing the nanoparticles through systematic validation of accuracy and *** particularly exhibit its unique advantages in detecting the polydisperse nanoparticle *** the nucleation and the thermodynamic stability of the bulk nanobubbles are systematically studied by the NTA *** bulk nanobubbles smaller than 600 nm in size are generated via the ultrasonication *** is shown that both the ultrasonic cavitation treatment time and amplitude,essentially,the energy input,favor the nucleation of the bulk nanobubbles with a more concentrated size distribution,a higher concentration,and a smaller hydrodynamic *** temperature dependence of the bulk nanobubbles over a wide range from 25°C to 70°C is *** is found that the nanobubble first shrinks in size significantly and then the size keeps approximately constant with the increasing temperature,showing a narrow size *** transition temperature is around 45°***,as an open system,the NTA is a potential tool in the study of the dynamic behavior of the bulk nanobubbles in situ,such as the coalescence and the collapse.

关键词： Nanoparticle tracking analysis bulk nanobubble light scattering hydrodynamic size number concentration

Simulation of 3D Porous Media flows with Application to Polymer Electrolyte Fuel Cells

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Communications in Computational Physics 2013年第3期13卷 851-866页

作者： N.I.Prasianakis T.Rosen J.Kang J.Eller J.Mantzaras F.N.Buchi combustion Research Laboratory Paul Scherrer InstituteVilligen PSI 5232Switzerland Electrochemistry Laboratory Paul Scherrer InstituteVilligen PSI 5232Switzerland Linne flow Centre KTH MechanicsSE-10044 StockholmSweden

A 3D lattice Boltzmann(LB)model with twenty-seven discrete velocities is presented and used for the simulation of three-dimensional porous media *** accuracy in combination with the half-way bounce back boundary condition is *** properties of the gas diffusion layers that are used in polymer electrolyte fuel cells can be determined with this *** in samples that have been obtained via X-ray tomographic microscopy,allows to estimate the values of permeability and relative effective ***,the computational LB results are compared with the results of other numerical tools,as well as with experimental values.

关键词： Porous media GDLs lattice Boltzmann fuel cells fluid dynamics

Numerical investigation of particle separation in Y-shaped bifurcating microchannels

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Particuology 2021年第3期19卷 142-151页

作者： Mahya Meyari Zeinab Salehi Reza Zarghami Mahdi Saeedipour School of Chemical Engineering College of EngineeringUniversity of TehranTehranIran department of Particulate flow Modelling Johannes Kepler UniversityLinzAustria

In this study the Zweifach-Fung effect is investigated in a Y-shaped bifurcation when the clearance between the rigid spherical particle and the walls is small compared to both channel’s and particle’s ***-and two-particle systems are studied using resolved computational fluid dynamics coupled to discrete element method to obtain a two-dimensional map of the initially positioned particles that would enter each child *** all cases,the path selection of the sphere depends on its two-dimensional positioning far from the bifurcation region in the parent *** the flow rate ratio or decreasing the Reynolds number intensifies the Zweifach-Fung bifurcation effect in a single-particle ***,in two-particle systems where non-contact particle-particle interaction is present,decreasing the particle-to-particle distance reduces the bifurcation effect,while changing the Reynolds number has the same influence as in the single-particle *** results provide insight for optimizing the flow characteristics in bifurcating microchannels to separate the suspended particles.

关键词： Zweifach-Fung effect Bifurcation CFD-DEM MicrOfluidics Particle separation