喷动流化床气固流动特性的三维数值模拟

采用离散元方法（DEM），在用欧拉方法处理气相场的同时用拉格朗日方法处理离散颗粒场，对喷动流化床煤部分气化炉内的气固流动进行了三维数值模拟．直接跟踪床内每一个离散颗粒，考虑了碰撞力、携带力、重力、剪切提升力和Magnus升力，颗粒碰撞采用软球模型．获得了喷动流化床典型操作参数下的流动结构、颗粒的受力、颗粒的速度分布、气体和颗粒的湍流强度等结果．结果表明，颗粒之间碰撞率随着喷动气速的增大而增大，随粒径的增大而减小，然而颗粒与壁面的碰撞率受喷动气速和粒径的影响不明显．颗粒的运动受重力、携带力和碰撞力主导，除喷动区与环形区交界外，Magnus力和Saffman力可以忽略．气体湍流强度是颗粒湍流强度的2～3倍，近壁面区的气体和颗粒的湍流强度均较小．

Three-dimensional numerical simulation of gas-solid flow behavior in spout-fluid bed

Numerical simulation of gas-solid flow behaviors in a spout-fluid bed coal gasifier was carried out three dimensionally by discrete element method(DEM).Eulerian method and Lagrangian method were employed to deal with the gas phase and solid phase respectively.Shear lift force,Magnus lift force as well as drag force,contract force and gravitational force acting on individual particle were considered when establishing the mathematic models.The collision of particles was modeled by soft-sphere model.The flow patterns,forces acting on particles,particle mean velocities,gas turbulent intensities and particle turbulent intensities under the typical operating conditions were obtained.The results show that the ratio of collision between particles increases with the increase of spouting gas velocity but decreases with the increase of particle size,while the ratio of collision between particles and wall is found no variation with spouting gas velocity and particle size.Gravitational force,drag force and contact force dominate the particle motion,while shear lift force and Magnus lift acting on the particles are negligible when the particles are not in the boundary of the spout region.The gas turbulent intensity is always two or three times stronger than the particle turbulent intensity,while they are both smaller near the wall.