流化床内流动特性的DEM数值模拟研究

华北电力大学硕士学位论文AbstractAs a new clean-burning technology,circulating fluidized bed(CFB)has being widelyused in the production.But because of its complex nature,people don't have clear andcomprehensive understanding of fluidization mechanism.To get a more in-depth study ofthe mechanism of fluidized bed,hydrodynamics characteristics of fluidized bed withdifferent nozzle count was researched with numerical simulation method in this paper.Numerical simulation technology for dense gas-solid flow could be divided into twocategories:the Euler-Euler particles quasi-fluid model and Euler-Lagrangian discreteparticle model.In this paper,the discrete element method was used,a description of thefluidized bed gas-solid flow was build,and simulated the progress of gas-soild flow,analysis the dynamic characteristics.First,discrete element method was proposed to implement numerical simulation offlow characteristics in fluidized bed,through the simulation,the prograss ofconformation,ascension and burst of bubble was obtained,the effect of flowcharacteristics in different entrance velocity was also revealed.Numerical simulationresults show that particle move with gas,the motion of gas was the main power source ofparticle,relative to single-nozzle system,because of the mergence,extrusion and burstbetween congenial bubbles,the motion and the diffusion was more fierce indouble-nozzles system.Secondly,on the basis of the single and double nozzles simulation,the multi-nozzlefluidized bed system was simulated,through the analysis of the impact of the nozzlenumber,the nozzle position,the gas velocity,particle density,the coefficient of elasticityof solid flow,contrast with single and double nozzle system,with the increase in thenumber of nozzle,the coefficient of elasticity was the main factors affecting thephenomenon of "interlock"between particles;with the increase of the number of inletholes,the time of changing into full flow stage was shorter;also,the intensive of nozzlesimpacted the vertical and the horizontal velocity of the particles and gas,the degree ofgas-solid flow intensity and the velocity increase with the increase of intensive.Keywords:circulating fluidized bed;dynamic characteristics;multi-nozzle;numericalsimulation