Based on the experimental observation of the fluidization characteristics of solid mixtures(resin and rapeseed)with different densities and sizes,the jet behaviours of the binary system are simulated in a twodimension...Based on the experimental observation of the fluidization characteristics of solid mixtures(resin and rapeseed)with different densities and sizes,the jet behaviours of the binary system are simulated in a twodimensional jetting fluidized bed 0.30m in width and 2.00m in height.A simple mathematical model,by introducing two additional force terms in both gas and particle phase momentum equations of Gidaspow’s inviscid two-fluid model,is used to explore the effects of jet gas velocity and mixture combination on the jet penetration depth in the fluidized bed with a binary system.Experimental results show that there is a fluidization velocity interval(u_(if)-u_(ff))for the resin-on-rapeseed(flotsam-on-jetsam)segregated bed.The simulated jet penetration depth increases with the increase of jet gas velocity and the volume fraction of the flotsam(resin),which is in fair agreement with experimental data.The above findings show that the hydrodynamic model of Brandani and Zhang(2006),by introducing the average physical properties from Goossens et al.(1971),can be used to predict the jet behaviors of a well-mixing binary system.展开更多
A computational fluid dynamics （CFD） model is used to investigate the hydrodynamics of a gas-solid fluidized bed with two vertical jets. Sand particles with a density of 2660 kg/m3 and a diameter of 5.0 × 10^-4...A computational fluid dynamics （CFD） model is used to investigate the hydrodynamics of a gas-solid fluidized bed with two vertical jets. Sand particles with a density of 2660 kg/m3 and a diameter of 5.0 × 10^-4 m are employed as the solid phase. Numerical computation is carried out in a 0.57 m ×1.00 m two-dimensional bed using a commercial CFD code, CFX 4.4, together with user-defined Fortran subroutines. The applicability of the CFD model is validated by predicting the bed pressure drop in a bubbling fluidized bed, and the jet detachment time and equivalent bubble diameter in a fluidized bed with a single jet. Subsequently, the model is used to explore the hydrodynamics of two vertical jets in a fluidized bed. The computational results reveal three flow patterns, isolated, merged and transitional jets, depending on the nozzle separation distance and jet gas velocity and influencing significantly the solid circulation pattern. The jet penetration depth is found to increase with increasing jet gas velocity, and can be predicted reasonably well by the correlations of Hong et al. （2003） for isolated jets and of Yang and Keairns （1979） for interacting jets.展开更多
基金Financial supports from the National Natural Science Foundation of China(Grant No.20976191)the National Key Technology R&D Program of China(2006BAD07A0301)aInternational Cooperative Program of Guizhou Province([2009]700110)。
文摘Based on the experimental observation of the fluidization characteristics of solid mixtures(resin and rapeseed)with different densities and sizes,the jet behaviours of the binary system are simulated in a twodimensional jetting fluidized bed 0.30m in width and 2.00m in height.A simple mathematical model,by introducing two additional force terms in both gas and particle phase momentum equations of Gidaspow’s inviscid two-fluid model,is used to explore the effects of jet gas velocity and mixture combination on the jet penetration depth in the fluidized bed with a binary system.Experimental results show that there is a fluidization velocity interval(u_(if)-u_(ff))for the resin-on-rapeseed(flotsam-on-jetsam)segregated bed.The simulated jet penetration depth increases with the increase of jet gas velocity and the volume fraction of the flotsam(resin),which is in fair agreement with experimental data.The above findings show that the hydrodynamic model of Brandani and Zhang(2006),by introducing the average physical properties from Goossens et al.(1971),can be used to predict the jet behaviors of a well-mixing binary system.
基金support from National Natural Science Foundation of China(No.20976191and No.51076043)Major State Basic Research Development Program of China(973Program,2005CB221205)International Cooperative Program of GuizhouProvince([2009]700110)
文摘A computational fluid dynamics （CFD） model is used to investigate the hydrodynamics of a gas-solid fluidized bed with two vertical jets. Sand particles with a density of 2660 kg/m3 and a diameter of 5.0 × 10^-4 m are employed as the solid phase. Numerical computation is carried out in a 0.57 m ×1.00 m two-dimensional bed using a commercial CFD code, CFX 4.4, together with user-defined Fortran subroutines. The applicability of the CFD model is validated by predicting the bed pressure drop in a bubbling fluidized bed, and the jet detachment time and equivalent bubble diameter in a fluidized bed with a single jet. Subsequently, the model is used to explore the hydrodynamics of two vertical jets in a fluidized bed. The computational results reveal three flow patterns, isolated, merged and transitional jets, depending on the nozzle separation distance and jet gas velocity and influencing significantly the solid circulation pattern. The jet penetration depth is found to increase with increasing jet gas velocity, and can be predicted reasonably well by the correlations of Hong et al. （2003） for isolated jets and of Yang and Keairns （1979） for interacting jets.
