斜分布板对鼓泡流化床流动特性的影响与数值模拟

Experimental and numerical investigation on effect of inclined distributor on hydrodynamic characteristics of a bubbling fluidized bed

为了研究斜分布板下颗粒流化特性,将烧结丝网制成的分布板倾斜放置在流化床底部,在一定流化速度下观察床内颗粒的流动状态,发现流化气基本从床层较低的地方射出,有明显的“短路”现象。采用基于欧拉-欧拉方法的双流体气-固两相流模型进行模拟,分布板简化为多孔介质模型,模拟得到的流动特性与实验现象基本一致。保持流化速度恒定,改变多孔介质参数以提高分布板压降,模拟结果表明:随着分布板压降的增大,能弱化短路现象带来的局部流化不利影响,使得床层较为均匀的膨胀。另外,通过比较4种曳力模型,发现斜分布板的起始流化位置基本一样,其中Syamlal&0,Brien模型预测的床层膨胀程度相对偏小。

Proper design of gas distributor was crucially critical to the performance of fluidized beds flow.In this work,sintered metallic porous materials was used as distributor,which was inclined at the bottom of the fluidized bed.Under specific fluidized velocity,it was found that the fluidizing gas favorites to flow through the less-resistance region where the height of bed is lowest.Meanwhile,two-fluid model based on Eulerian-Eulerian framework was used to simulate the gas-particle flow in the bed,and the distributor is simplified as porous media.The results show that the prediction of fluidization characteristics is in agreement with experimental observation.Keeping constant fluidized velocity and increasing the pressure drop through distributor,the quality of fluidization is improved.Numerical simulations indicate that drag coefficients have a negligible effect on the predicted onset of fluidization,while Syamlal&0'Brien drag model gives a minimum bed expansion height.