The flow field of gas and liquid in a φ150mm rotating-stream-tray (RST) scrubber is simulated by using computational fluid dynamic (CFD) method. The sismulation is based on the two-equation RNG κ-ε turbulence model...The flow field of gas and liquid in a φ150mm rotating-stream-tray (RST) scrubber is simulated by using computational fluid dynamic (CFD) method. The sismulation is based on the two-equation RNG κ-ε turbulence model, Eulerian multiphase model, and a real-shape 3D model with a huge number of meshes. The simulation results include detailed information about velocity, pressure, volume fraction and so on. Some features of the flow field are obtained: liquid is atomized in a thin annular zone; a high velocity air zone prevents water drops at the bottom from flying towards the wall; the pressure varies sharply at the end of blades and so on. The results will be helpful for structure optimization and engineering design.展开更多
A three-dimensional computational fluid dynamics model is developed by software Fluent 6.2, to simulate the flow field inside the nozzle block of the Murata vortex spinning. The flowing state and the distribution law ...A three-dimensional computational fluid dynamics model is developed by software Fluent 6.2, to simulate the flow field inside the nozzle block of the Murata vortex spinning. The flowing state and the distribution law of static pressure and velocity are characterized and analyzed. The relationship between the flowing state and the structure of the vortex spun yarn is also discussed. The research results can enhance the understanding of the yarn formation principle from viewpoint of the airflow field law inside the nozzle block of Murata vortex spinning.展开更多
Based on the primitive equations in polar coordinates and with the supposition that parcel velocity in tropical cyclones is in linear variation and that the distribution of surface pressure agrees with the Fujita form...Based on the primitive equations in polar coordinates and with the supposition that parcel velocity in tropical cyclones is in linear variation and that the distribution of surface pressure agrees with the Fujita formula, a set of equations are derived, which describe the impact of perturbations of central pressure, position of tropical cyclones, direction and velocity of movement of tropical cyclones on the wind field. It is proved that the second order approximation of the kinetic energy of tropical cyclones can be described by the equations under linear approximation. Typhoon Wipha (2007) is selected to verify the above interpretation method, and the results show that the interpretation method of the wind field could give very good results before the landfall of tropical cyclones, while making no apparent improvement after the landfall. The dynamical interpretation method in this paper is applicable to improving the forecasts of the wind field of tropical cyclones close to the coast.展开更多
The inner flow field of a biogas plant can be optimized by agitating the feedstock to be evenly distributed for a rising biogas production rate. A hydraulic agitator can be installed in the digester with outlets far a...The inner flow field of a biogas plant can be optimized by agitating the feedstock to be evenly distributed for a rising biogas production rate. A hydraulic agitator can be installed in the digester with outlets far above the bottom. Hydraulic mixing is essential in a solid-liquid two-phase flow process, in which large solid particles can be found at the initial stage and turn to being high-concentration viscous liquid （non-Newtonian fluid）. A 0.75 m3 digester was taken as a case study with CFD （computational fluid dynamics） software. The basic pattern was simulated by using water as the medium and the pattern of pseudo plastic fluid state was simulated by the Euler-Euler Model, then the effect of optimized design with bottom inflow and high dispersed outlets could be verified. Viewed from the mixing effects, the velocity of 0.6 m/s is better than l m/s for water medium, while 1 m/s better than 0.6 m/s for pseudo plastic fluid medium.展开更多
Spiral Magnus is a unique wind turbine system that rotates with cylinders which have spiral-shaped fins coiled around them （instead of using the more common propeller-type blades）. In the present study, three models...Spiral Magnus is a unique wind turbine system that rotates with cylinders which have spiral-shaped fins coiled around them （instead of using the more common propeller-type blades）. In the present study, three models （cylinder with no fins, cylinder with straight fins and cylinder with spiral fins） were installed, and fluid force measurements were performed by a strain gauge force balance. A PIV （particle image velocimetry） system was used to better understand the flow fields around the cylinder. Considering the results of the experiment, it was confirmed that, the aerodynamic performance of the rotating cylinder can be improved by the fin. However, the straight fin makes the flow close to the cylinder surface ineffective. The rotary cylinder with the spiral fins was able to generate the greatest lift among three models, because the spiral fin effectively influences the vicinity of the cylinder surface.展开更多
In this paper, the effect of the imaginary circle diameter opi and the initial flow field on the aerodynamic field in a tangentially fired furnace was studied by numerical simulation and experiments in the cold model....In this paper, the effect of the imaginary circle diameter opi and the initial flow field on the aerodynamic field in a tangentially fired furnace was studied by numerical simulation and experiments in the cold model. Results show that merely reducing the imaginary circle diameter rki can not significantly reduce the rotatiollal diameter op in the range considered. The flow still rotates coullter-clockwise stably and does not change rotation direction when the direction of all jet axes are defiected suddenly to the opposite rotation direction by up to 5.4" in a countereclockwise llow field. It is the first time that the numerical sAnulation results were obtained which agreed quite well with this experimental phenomena qualitatively. The experimental data, i.e., the rotational diameter & and the maximum velocity on the syrnmetric central line of fUrnace Vm, are only a bit larger than the simulation results. It is shown that the initial flow field has an important influence on the aerodynamic field in the furnace. Other measures have to be taken as wel1 in order to reduce & to resist slagging and high temperature corrosion of furnace tubes. Moreover, a new kind of grid arrangement was proposed in this paper, which can reduce effectively the false diffosion at the exit zone of burner.展开更多
The present paper has compared a group of furnace aerodynamic fields at different velocities of side secondary air （SSA） in a test model of 420t/h utility boiler, applying Horizontal Bias Combustion Pulverized Coal ...The present paper has compared a group of furnace aerodynamic fields at different velocities of side secondary air （SSA） in a test model of 420t/h utility boiler, applying Horizontal Bias Combustion Pulverized Coal Burner with Side Secondary Air （HBC-SSA Burner）. Experimental results show that, when the ram pressure ratio of side secondary air （SSA） to primary air （PA） （p2s..v2s2./p1v12） is between 1.0-2.4, the furnace aerodynamic field only varies slightly. The relative rotational diameters （φ/L） in the burner domain are moderate and the furnace is in good fullness. When p2sv2s2/p1v12 is beyond 4, φ/L is so large that the stream sweeps water-cooled wall and rotates strongly in the furnace. Therefore, slagging and high temperature corrosion of tube metal will be formed on the water-cooled wall in actual operation. This investigation provides the basis for the application of this new type burner. In addition, numerical simulations are conducted, and some defects in the numerical simulation are also pointed out and analyzed in this paper.展开更多
基金Supported by the National 863 Project (2001AA642030-1) and Zhejiang Provincial Key Research Project (010007037).
文摘The flow field of gas and liquid in a φ150mm rotating-stream-tray (RST) scrubber is simulated by using computational fluid dynamic (CFD) method. The sismulation is based on the two-equation RNG κ-ε turbulence model, Eulerian multiphase model, and a real-shape 3D model with a huge number of meshes. The simulation results include detailed information about velocity, pressure, volume fraction and so on. Some features of the flow field are obtained: liquid is atomized in a thin annular zone; a high velocity air zone prevents water drops at the bottom from flying towards the wall; the pressure varies sharply at the end of blades and so on. The results will be helpful for structure optimization and engineering design.
基金This project is supported by the National Natural Science Foundation of China,under grant No.10872047.
文摘A three-dimensional computational fluid dynamics model is developed by software Fluent 6.2, to simulate the flow field inside the nozzle block of the Murata vortex spinning. The flowing state and the distribution law of static pressure and velocity are characterized and analyzed. The relationship between the flowing state and the structure of the vortex spun yarn is also discussed. The research results can enhance the understanding of the yarn formation principle from viewpoint of the airflow field law inside the nozzle block of Murata vortex spinning.
基金National Basic Research Program of China (973 Program) (2009CB421505)Major Projects for Science and Technology Development of Zhejiang Province (2007C13G1610002)Natural Science Foundation Project of Zhejiang Province(Y505286)
文摘Based on the primitive equations in polar coordinates and with the supposition that parcel velocity in tropical cyclones is in linear variation and that the distribution of surface pressure agrees with the Fujita formula, a set of equations are derived, which describe the impact of perturbations of central pressure, position of tropical cyclones, direction and velocity of movement of tropical cyclones on the wind field. It is proved that the second order approximation of the kinetic energy of tropical cyclones can be described by the equations under linear approximation. Typhoon Wipha (2007) is selected to verify the above interpretation method, and the results show that the interpretation method of the wind field could give very good results before the landfall of tropical cyclones, while making no apparent improvement after the landfall. The dynamical interpretation method in this paper is applicable to improving the forecasts of the wind field of tropical cyclones close to the coast.
文摘The inner flow field of a biogas plant can be optimized by agitating the feedstock to be evenly distributed for a rising biogas production rate. A hydraulic agitator can be installed in the digester with outlets far above the bottom. Hydraulic mixing is essential in a solid-liquid two-phase flow process, in which large solid particles can be found at the initial stage and turn to being high-concentration viscous liquid （non-Newtonian fluid）. A 0.75 m3 digester was taken as a case study with CFD （computational fluid dynamics） software. The basic pattern was simulated by using water as the medium and the pattern of pseudo plastic fluid state was simulated by the Euler-Euler Model, then the effect of optimized design with bottom inflow and high dispersed outlets could be verified. Viewed from the mixing effects, the velocity of 0.6 m/s is better than l m/s for water medium, while 1 m/s better than 0.6 m/s for pseudo plastic fluid medium.
文摘Spiral Magnus is a unique wind turbine system that rotates with cylinders which have spiral-shaped fins coiled around them （instead of using the more common propeller-type blades）. In the present study, three models （cylinder with no fins, cylinder with straight fins and cylinder with spiral fins） were installed, and fluid force measurements were performed by a strain gauge force balance. A PIV （particle image velocimetry） system was used to better understand the flow fields around the cylinder. Considering the results of the experiment, it was confirmed that, the aerodynamic performance of the rotating cylinder can be improved by the fin. However, the straight fin makes the flow close to the cylinder surface ineffective. The rotary cylinder with the spiral fins was able to generate the greatest lift among three models, because the spiral fin effectively influences the vicinity of the cylinder surface.
文摘In this paper, the effect of the imaginary circle diameter opi and the initial flow field on the aerodynamic field in a tangentially fired furnace was studied by numerical simulation and experiments in the cold model. Results show that merely reducing the imaginary circle diameter rki can not significantly reduce the rotatiollal diameter op in the range considered. The flow still rotates coullter-clockwise stably and does not change rotation direction when the direction of all jet axes are defiected suddenly to the opposite rotation direction by up to 5.4" in a countereclockwise llow field. It is the first time that the numerical sAnulation results were obtained which agreed quite well with this experimental phenomena qualitatively. The experimental data, i.e., the rotational diameter & and the maximum velocity on the syrnmetric central line of fUrnace Vm, are only a bit larger than the simulation results. It is shown that the initial flow field has an important influence on the aerodynamic field in the furnace. Other measures have to be taken as wel1 in order to reduce & to resist slagging and high temperature corrosion of furnace tubes. Moreover, a new kind of grid arrangement was proposed in this paper, which can reduce effectively the false diffosion at the exit zone of burner.
文摘The present paper has compared a group of furnace aerodynamic fields at different velocities of side secondary air （SSA） in a test model of 420t/h utility boiler, applying Horizontal Bias Combustion Pulverized Coal Burner with Side Secondary Air （HBC-SSA Burner）. Experimental results show that, when the ram pressure ratio of side secondary air （SSA） to primary air （PA） （p2s..v2s2./p1v12） is between 1.0-2.4, the furnace aerodynamic field only varies slightly. The relative rotational diameters （φ/L） in the burner domain are moderate and the furnace is in good fullness. When p2sv2s2/p1v12 is beyond 4, φ/L is so large that the stream sweeps water-cooled wall and rotates strongly in the furnace. Therefore, slagging and high temperature corrosion of tube metal will be formed on the water-cooled wall in actual operation. This investigation provides the basis for the application of this new type burner. In addition, numerical simulations are conducted, and some defects in the numerical simulation are also pointed out and analyzed in this paper.
