Advanced Materials Research Vols. 516-517

Abstract: Gas-solid two-phase flow of the quick-contact cyclone reactor used in FCC was simulated with the multi fluid Eulerian model, especially the velocity field and volume fraction of solid in the mixing chamber was researched. The results show that flow pattern and catalyst particles concentration are non-uniform in the direction of axial, radial and tangential. The tangential gas admission increases turbulent intensity, it has a great benefit on spreading the catalyst particles uniformly, enhancing gas-solid contact effect. This work could offer a base for the structure optimization of the quick-contact reactor.

Abstract: The present paper focuses on the analysis of transient heat transfer and flow in a vibratory tube. The characteristics of flow and heat transfer are investigated by dynamic mesh of CFD (computational fluid dynamics) software FLUENT, the velocity and temperature distributions in a vibration cycle are analyzed by field synergy theory. The results indicate that the vibration parameters have great effect on heat transfer, and the tube vibration leads to heat transfer enhancement or reduction. Moreover, the optimum heat transfer performance inside tubes is obtained in a half-cycle when time phase is 90°.

Abstract: Numerical simulations have been captured for 3-D crossing shock wave/turbulent boundary layer interactions generated by 15-deg sharp fins mounted symmetrically on a flat plate at mach8.3. The full Reynolds-averaged Navier-Stokes equations are solved with high-resolution implicit finite-volume scheme. Turbulence closure is achieved with Spalart-Allmaras(SA), Wilcox’ k-ω and Menter’s Shear Stress Transport (SST) models. Complex crossing shock wave interactions, flowfield structures including the boundary-layer separation, centerline vortex, vortex interaction and entrainment flow have been revealed. Comparisons for profiles of the velocity vector, pressure and heat transfer distribution have been observed between calculated results and experimental measurements. Behavior of turbulence models in the complex flow have been pointed out. SST shows better performance in calculating the pressure and the velocity vector and all turbulence models over-predicted heat transfer coefficient.

Abstract: Taking the G4-73№8D centrifugal fan as research object and utilizing the software of NUMECA to simulate flow fields of impellers with different splotted blades, the parameters of slotted blade are optimized through contrastive analysis of the effects on internal flow characteristics and performance. Results show that the optimized scheme can improve the uniformity of internal flow field, full pressure and efficiency seperatly increase by 4.25% and 1.49% under the design flow. For the needs of variable fan load operation, this paper puts forward the optimization principle of slit parameter.

Abstract: Centrifugal pumps adopt annular casings instead of volute casings when working in high temperature and high pressure conditions, which results in conservative safety factors in sacrifice of hydraulic efficiency. This paper presents numerical simulations on two assembly modification methods for one annular casing imitating the volute casing to improve hydraulic performance. Method one was the eccentric axis method. Method two was the extended vane method. Numerical simulation results, given by CFX, showed that both the two method could increase the hydraulic efficiency and head while rise in radial force was small.

Abstract: In order to study the flow characteristics in the stator and air gap for a large air-cooled turbo-generator with multi-air-zone of stator, a 3-D physical model includes the stator, rotor, and air gap was established. Numerical simulation was carried out by the finite volume method according computational fluid dynamics (CFD) principle, based on some corresponding boundary conditions and assumptions. The results show that the cooling air flowing into the air-gap through the outlets of rotor wedge rotates with rotor in the spiral trajectory and in higher velocity than ambient. The air velocity alternate high and low in axial direction. There are different flow characteristics in different regions of the air gap because of the influence of stator and rotor radial air injection and axial through flow. The air flowing into the air-gap from the cold zone forms the secondary flow near the side of stator.

Abstract: Swirling flows are widely used in energy engineering, such as swirling combustor, cyclone separator in pulverized coal burners. The vortex evolution and correlation between twin swirling flows are investigated via direct numerical simulation. Three typical swirl flows with different swirl number are simulated. The structure of vortex evolution, velocity correlation between the twin flows are illustrated and analyzed in detail. The results show the phase-locked correlation of flow velocity between the twin swirling jets which would be useful and helpful for improving the understanding of aerodynamics of multi-swirling systems.

Abstract: In this study, SPMD parallel computation of compressible turbulent jet flow with an explicit finite difference method by direct numerical method is performed on the IBM Linux Cluster. The conservation equations, boundary conditions including NSCBC (charactering boundary conditions), grid generation method, and the solving processing are carefully presented in order to give other researchers a clear understanding of the large scale parallel computing of compressible turbulent flows using explicit finite difference method, which is scarce in the literatures. The speedup factor and parallel computational efficiency are presented with different domain decomposition methods. In order to use our explicit finite method for large scale parallel computing, the grid size imposed on each processor, the speedup factor, and the efficiency factor should be carefully chosen in order to design an efficient parallel code. Our newly developed parallel code is quite efficient from that of implicit finite difference method or spectral method on parallel computational efficiency. This is quite useful for future research for gas and particle two-phase flow, which is still a problem for highly efficient code for two-phase parallel computing.

Abstract: The flow field inside cyclone separator is a kind of complex three-dimensional rotation turbulent flow with two-phase separation phenomenon. In order to optimize the structure and shorten the cycle of research and development, it is very essential to find the appropriate calculation method for the flow field inside cyclone separator. In this article, the internal flow field of tangential inlet cyclone separator was simulated and calculated by adopting different calculation model and different numerical simulation scheme by orthogonal design method. And the result was compared with that of existing experiment to find a reasonable method for the simulation of the flow field inside the cyclone. On the basis of standard k-ε model, the numerical simulation scheme was formulated by the orthogonal test method, through the comparison of results, the best combinations are gained; This research result has certain reference value for cyclone separator design and performance optimization.

Abstract: In China, currently there are more than 7, 000 tailings impoundments all over the country and most of them have potential hazard. With the gradually increasing of tailings dam-break disaster because of multifarious factors, the people’s lives, property and the environment of nearby regions can suffer great harm, The safety of tailings management facilities has caused increasing concern and attention from the governments and local community. Because of the different hydraulic power, the tailings pulp concentration surging from tailings dam-break have great differences, research on the movement mechanism of different concentration tailings pulp surging from tailings dam-break and to propose the emergency preparedness is very important. Therefore, In this study, a physics test model for tailings dam-break was carried out in hydrodynamic laboratory based on the design data of impoundments. Through the simulation experiment, the movement mechanism of tailings dam-break wave which includes the law of debris flow evolution, the change of impact force strength and velocities of the front of wave are considered in the conditions of changing the tailings pulp. The results can provide reliable information for guiding the crowd of downstream to remove immediately and lighten the loss of disaster.