3D Euler double-fluid model was applied and three different feedstocks and reverts formations were simulated. By calculating and analyzing the state of gas and solid fluxion in absorber using three different methods o...3D Euler double-fluid model was applied and three different feedstocks and reverts formations were simulated. By calculating and analyzing the state of gas and solid fluxion in absorber using three different methods of the feedstocks and reverts in recirculating fluidized bed, described the behavior of gas and solid through the gas-phase velocity, turbulence intensity, gas-solid sliding velocity, and density of particles. The results show that the feedstocks and reverts enters into absorption tower through two symmetrical feedings and are mixed with flue gas. Based on the respective analysis of each model and the com- parison analysis of the three models, this paper drew conclusions. The turbulence intensity of absorption tower is high, gas-solid sliding speed is big, and granule concentration near the axis is high, which has advantages for desulfurization and im- proving the utilization rate of absorbent.展开更多
The flow structure of one isothermal swirling case in the Sydney swirl flame database was studied using two numerical methods. Results from the Reynolds-averaged Navier-Stokes (RANS) approach and large eddy simulation...The flow structure of one isothermal swirling case in the Sydney swirl flame database was studied using two numerical methods. Results from the Reynolds-averaged Navier-Stokes (RANS) approach and large eddy simulation (LES) were compared with experimental measurements. The simulations were applied in two different Cartesian grids which were investigated by a grid independence study for RANS and a post-estimator for LES. The RNG k-ε turbulence model was used in RANS and dynamic Smagorinsky-Lilly model was used as the sub-grid scale model in LES. A validation study and cross comparison of ensemble average and root mean square (RMS) results showed LES outperforms RANS statistic results. Flow field results indicated that both approaches could capture dominant flow structures, like vortex breakdown (VB), and precessing vortex core (PVC). Streamlines indicate that the formation mechanisms of VB deducted from the two methods were different. The vorticity field was also studied using a velocity gradient based method. This research gained in-depth understanding of isothermal swirling flow.展开更多
This study proposes a new approach in which an impermeable plate is placed under the pipeline to prevent the local scour around the pipeline.In order to understand the performance of this approach,the finite volume me...This study proposes a new approach in which an impermeable plate is placed under the pipeline to prevent the local scour around the pipeline.In order to understand the performance of this approach,the finite volume method(FVM) and volume of fluid(VOF) method are adopted to simulate the flow field around the pipeline.The pressure distribution along the sandy bed surface is obtained by considering the variation of water surface.Furthermore,the effects of water depth,unidirectional and bidirectional impermeable plates on pressure difference are discussed.The seepage flow field of sandy bed near underwater pipeline is numerically simulated using the laminar and porous media model.On this basis,the effect of the impermeable plate length on hydraulic gradient is investigated and the critical length of impermeable plate is obtained.The simulated results show that when the water depth is smaller than 5.00D(D is the diameter of pipeline),the effect of the water depth on the pressure difference is remarkable.The pressure differences between two endpoints of both the unidirectional and bidirectional plates decrease with the increase of the plate length.The variations of the pressure differences for both the unidirectional and bidirectional plates are similar.With the increase of plate length,the hydraulic gradient decreases and the piping at the seepage exit is avoided effectively as long as it reaches a certain length.Such a critical length of the plate decreases with the increase of the water depth.When water depth is larger than 4.00D,the effect of the water depth on the critical length is small.For the same water depth,the critical length of impermeable plate increases with the increase of the dimensionless flow parameter.Numerical simulation results are in good agreement with the available experimental measurements.展开更多
文摘3D Euler double-fluid model was applied and three different feedstocks and reverts formations were simulated. By calculating and analyzing the state of gas and solid fluxion in absorber using three different methods of the feedstocks and reverts in recirculating fluidized bed, described the behavior of gas and solid through the gas-phase velocity, turbulence intensity, gas-solid sliding velocity, and density of particles. The results show that the feedstocks and reverts enters into absorption tower through two symmetrical feedings and are mixed with flue gas. Based on the respective analysis of each model and the com- parison analysis of the three models, this paper drew conclusions. The turbulence intensity of absorption tower is high, gas-solid sliding speed is big, and granule concentration near the axis is high, which has advantages for desulfurization and im- proving the utilization rate of absorbent.
基金the financial support of DONG Energy [PSO2007-7333]
文摘The flow structure of one isothermal swirling case in the Sydney swirl flame database was studied using two numerical methods. Results from the Reynolds-averaged Navier-Stokes (RANS) approach and large eddy simulation (LES) were compared with experimental measurements. The simulations were applied in two different Cartesian grids which were investigated by a grid independence study for RANS and a post-estimator for LES. The RNG k-ε turbulence model was used in RANS and dynamic Smagorinsky-Lilly model was used as the sub-grid scale model in LES. A validation study and cross comparison of ensemble average and root mean square (RMS) results showed LES outperforms RANS statistic results. Flow field results indicated that both approaches could capture dominant flow structures, like vortex breakdown (VB), and precessing vortex core (PVC). Streamlines indicate that the formation mechanisms of VB deducted from the two methods were different. The vorticity field was also studied using a velocity gradient based method. This research gained in-depth understanding of isothermal swirling flow.
基金supported by the National Natural Science Foundation of China(Grant No.51279189)the National Hi-Tech Research and Development Program of China("863"Project)(Grant No.2008AA09Z309)China Scholarship Council and University of Aberdeen
文摘This study proposes a new approach in which an impermeable plate is placed under the pipeline to prevent the local scour around the pipeline.In order to understand the performance of this approach,the finite volume method(FVM) and volume of fluid(VOF) method are adopted to simulate the flow field around the pipeline.The pressure distribution along the sandy bed surface is obtained by considering the variation of water surface.Furthermore,the effects of water depth,unidirectional and bidirectional impermeable plates on pressure difference are discussed.The seepage flow field of sandy bed near underwater pipeline is numerically simulated using the laminar and porous media model.On this basis,the effect of the impermeable plate length on hydraulic gradient is investigated and the critical length of impermeable plate is obtained.The simulated results show that when the water depth is smaller than 5.00D(D is the diameter of pipeline),the effect of the water depth on the pressure difference is remarkable.The pressure differences between two endpoints of both the unidirectional and bidirectional plates decrease with the increase of the plate length.The variations of the pressure differences for both the unidirectional and bidirectional plates are similar.With the increase of plate length,the hydraulic gradient decreases and the piping at the seepage exit is avoided effectively as long as it reaches a certain length.Such a critical length of the plate decreases with the increase of the water depth.When water depth is larger than 4.00D,the effect of the water depth on the critical length is small.For the same water depth,the critical length of impermeable plate increases with the increase of the dimensionless flow parameter.Numerical simulation results are in good agreement with the available experimental measurements.
