This paper presents simulation results of the density segregation in a dense binary gas fluidized bed using a multi-fluid model from Chao et al. （2011）, The segregation behavior of two types of particles with approx...This paper presents simulation results of the density segregation in a dense binary gas fluidized bed using a multi-fluid model from Chao et al. （2011）, The segregation behavior of two types of particles with approximately same particle diameters and different particle densities was studied and validated using the experimental data from Formisani et al, （2008）. Some detailed information regarding the gas, particle velocity profiles, the distributions of the particle volume fractions and the flotsam-to-total par- ticle volume fraction ratios is presented. The simulation results show that the simulated axial average flotsam-to-total particle volume fraction ratio distribution agrees reasonably with the experimental data of Formisani et al. （2008）. The binary particle velocities are closely coupled though the segregation exists, The segregation behavior and the particle velocity profiles are superficial gas velocity dependent. The number and distribution of particle velocity vortices change dramatically with superficial gas velocity： at a comparatively low superficial gas velocity, the particles mainly segregate axially, and at a comparatively high superficial gas velocity, the particles segregate both axially and radially.展开更多
The transient finite element technique is applied, and a transient heat conduction model of wet brake friction disk is established. For obtaining the accurate heat flow density mathematic model and avoiding possibly i...The transient finite element technique is applied, and a transient heat conduction model of wet brake friction disk is established. For obtaining the accurate heat flow density mathematic model and avoiding possibly instable thermoelastic stress produced by the non uniform contact pressure of friction pair, a test method is applied to collect accurate contact pressure between the dual sheet steel and friction disk in the combining process. And then the heat-flow density and transient ther mo mechanical coupling simulation are analyzed. At the same time all possible boundary conditions are considered, such as the heat generation, heat conduction problem, relation between friction and contact, variation in load and heat change problem etc. The simulation results show that the me chanical model of thermo mechanical coupling can express well the dynamic characteristics of fric tion disk, and gives perfect reference for more study on thermoelastic distortion of brake friction pairs.展开更多
Riser operating modes are vital to designing a circulating fluidized bed （CFB） reactor for a required process of either a gas-solid or a gas-catalytic nature. Different operating modes provide different solids＇ res...Riser operating modes are vital to designing a circulating fluidized bed （CFB） reactor for a required process of either a gas-solid or a gas-catalytic nature. Different operating modes provide different solids＇ residence times and mixing behaviors, which define the reactions＇ efficiency and yield. The literature demonstrates distinct operating modes resulting from observed differences in slip factors and the range of particle velocities and their associated residence time distribution. The present research uses positron emission particle tracking （PEPT） in a riser of B-type bed material to determine the different operating modes by measuring （i） particle velocities and residence time distribution, （ii） population densities of these particles in the cross-sectional area of the riser, and （iii） solids flow pattern at the bottom of the riser, Data treatment defines four distinct solids hold-up regimes in the riser and proposes a ＂phase diagram＂ depicting the existence of the different operating modes （dilute, dense, core-annulus and combined） as a function of the superficial gas velocity and solids circulation flux in the riser. The delineated regimes have good agreement with available literature data and known industrial operations. Comparison with literature data for risers using A-type powders is also fair. The diagram enables CFB designers to better delineate operating characteristics.展开更多
基金The PhD fellowship(Chao Z.)financed through the GASSMAKS program(Advanced Reactor Modeling and Simulation)the PAFFrx project(Particle-Fluid Flow with Chemical Reaction-Multi level models for design and optimization of fluidized bed processes)of the Norwegian Research Council
文摘This paper presents simulation results of the density segregation in a dense binary gas fluidized bed using a multi-fluid model from Chao et al. （2011）, The segregation behavior of two types of particles with approximately same particle diameters and different particle densities was studied and validated using the experimental data from Formisani et al, （2008）. Some detailed information regarding the gas, particle velocity profiles, the distributions of the particle volume fractions and the flotsam-to-total par- ticle volume fraction ratios is presented. The simulation results show that the simulated axial average flotsam-to-total particle volume fraction ratio distribution agrees reasonably with the experimental data of Formisani et al. （2008）. The binary particle velocities are closely coupled though the segregation exists, The segregation behavior and the particle velocity profiles are superficial gas velocity dependent. The number and distribution of particle velocity vortices change dramatically with superficial gas velocity： at a comparatively low superficial gas velocity, the particles mainly segregate axially, and at a comparatively high superficial gas velocity, the particles segregate both axially and radially.
基金Supported by the National Basic Research Program of China("973"Program)(613002)
文摘The transient finite element technique is applied, and a transient heat conduction model of wet brake friction disk is established. For obtaining the accurate heat flow density mathematic model and avoiding possibly instable thermoelastic stress produced by the non uniform contact pressure of friction pair, a test method is applied to collect accurate contact pressure between the dual sheet steel and friction disk in the combining process. And then the heat-flow density and transient ther mo mechanical coupling simulation are analyzed. At the same time all possible boundary conditions are considered, such as the heat generation, heat conduction problem, relation between friction and contact, variation in load and heat change problem etc. The simulation results show that the me chanical model of thermo mechanical coupling can express well the dynamic characteristics of fric tion disk, and gives perfect reference for more study on thermoelastic distortion of brake friction pairs.
文摘Riser operating modes are vital to designing a circulating fluidized bed （CFB） reactor for a required process of either a gas-solid or a gas-catalytic nature. Different operating modes provide different solids＇ residence times and mixing behaviors, which define the reactions＇ efficiency and yield. The literature demonstrates distinct operating modes resulting from observed differences in slip factors and the range of particle velocities and their associated residence time distribution. The present research uses positron emission particle tracking （PEPT） in a riser of B-type bed material to determine the different operating modes by measuring （i） particle velocities and residence time distribution, （ii） population densities of these particles in the cross-sectional area of the riser, and （iii） solids flow pattern at the bottom of the riser, Data treatment defines four distinct solids hold-up regimes in the riser and proposes a ＂phase diagram＂ depicting the existence of the different operating modes （dilute, dense, core-annulus and combined） as a function of the superficial gas velocity and solids circulation flux in the riser. The delineated regimes have good agreement with available literature data and known industrial operations. Comparison with literature data for risers using A-type powders is also fair. The diagram enables CFB designers to better delineate operating characteristics.
