内循环流化床颗粒流动特性的直接数值模拟

内循环流化床是一种新型式的流化床，采用多风室非均匀布风实现床料颗粒的大尺度循环流动，从而增强了颗粒的横向混合。内循环流化床已应用于城市生活垃圾的焚烧制能，其燃烧速度、燃尽率及污染物排放优于传统的链条炉或鼓泡床。但是，目前设计的内循环流化床普遍较小，还不能满足城市垃圾的处理要求．根本原因在于对床内的气-固流动特性，特别是颗粒的运动规律没有深入的认识。内循环流化床内的气一固流动属于稠密的两相流，通过试验手段，如PIV、PDA也很难获得床内单个颗粒的运动特征。因此，采用前言的DEM(Discrete Element Method)模型对二维内循环流化床内的颗粒流动进行直接数值模拟．模拟结果表明非均匀布风内循环流化床内确实存在颗粒的大尺度循环流动。图4表1参5

Direct Numerical Simulation on Particles Flow in the Internally Circulating Fluidized Bed

Internally circulating fluidized beds are new type of fluidized beds, uneven distribution is used to cause large scale circulating flow of bed material, then enhance transverse mix of particles. Internally circulating fluidized beds have been applied to municipal waste incineration for power, these beds' combustion velocity, burn-off rate and pollution control are better than chain furnace or bubble beds. However internally circulating fluidized beds designed are small at present, don't reach the standard of municipal garbage treatment, it is the essential reason that the characteristic of gas-solid flow, especial particles moving, in beds are not understood by researchers. Gas-solid flow in internally circulating fluidized beds is dense two-phase flow, single particle's moving characteristic can't be easilyobtained through experimental methods such as PIV, PDA, etc. So particles flow in a two-dimension internally circulating fluidized bed is directly simulated with advance DEM (Discrete element method) model in this paper. The simulated result indicates that there is large scale particles circulating flow in the internally circulating fluidized with uneven distribution.Figs 4, table 1 and refs5.