基于介尺度曳力模型的细颗粒扬析CFD模拟

CFD simulation of fines elutriation with a sub-scale drag model

为了揭示细颗粒扬析特性,采用双流体模型,并结合考虑气泡影响的介尺度曳力模型,对双组分流化床内细颗粒扬析过程进行了CFD数值模拟。验证了气泡介尺度曳力模型的合理性,分析了入口气体速度、初始细颗粒质量分数、细颗粒直径和床层温度对细颗粒扬析过程的影响。结果显示:气泡介尺度曳力模型可以较好地再现颗粒扬析过程,气体入口速度和初始细颗粒质量分数的增大有利于扬析过程的加深,并且由于颗粒聚集导致细颗粒扬析速率与细颗粒直径呈非单调线性关系,同时,床层温度过高会使得相间曳力非均一化程度加深,细颗粒的扬析速率减小。

In order to reveal the fines elutriation characteristics,a CFD numerical simulation of the fines elutriation process in binary component fluidized bed was carried out based on the two-fluid model,where the sub-scale drag model was implemented to describe the bubble effect in the bed.The rationality of the bubble-based drag model was verified,and the effects of inlet gas velocity,initial fines mass fraction,fines diameter and bed temperature on fines elutriation process were analyzed.The results show that the bubble-based drag model can reproduce the elutriation process of fines better.The increases of the gas inlet velocity and the initial fines mass fraction are conducive to the deepening of the elutriation process,and the relationship between the fines elutriation rate and the fines diameter is non monotonic linear due to particle aggregation.Meanwhile,the high bed temperature will increase the degree of heterogeneity of the phase drag and decrease the elutriation rate of fines.