中文摘要：

气固流化床离散颗粒模拟中通常采用面积加权平均法计算局部空隙率,不能较好地反映流化床中显著的非均匀结构特性。为了考虑非均匀结构对局部空隙率的影响,文中提出一个适用鼓泡流化床的局部空隙率模型。将流场划分为稀区（气泡区）和密区（乳相区）;非均匀结构对密区局部空隙率的影响通过引入局部空隙率下限和非均匀影响系数描述;将提升管流动中颗粒团的空隙率关联式进行修正,得到鼓泡流化床中局部空隙率的下限;采用基于颗粒分布的自适应方法计算非均匀影响系数,从而建立了计算局部空隙率的气泡乳相模型。模拟结果表明：气泡乳相模型在气泡鼻区域计算的局部空隙率显著低于面积加权平均法的计算结果,因而在该区域能较大幅度地修正曳力。与传统离散颗粒方法的模拟相比较,采用气泡乳相模型计算局部空隙率的模拟更接近实验结果,并能捕捉气泡冒出床层的复杂现象。

英文摘要：

Area weighted averaging is usually adopted to calculate the local voidage in discrete particle simulations of gas-solid fluidized beds.However,it results in poor characterization of distinct heterogeneity in fluidized beds.In order to take into account the influence of the heterogeneous structure on local voidage,a local voidage model for simulations of bubbling fluidized beds was presented.The flow field was divided into the dilute region（the bubble region） and the dense region（the emulsion region）.The influence of the heterogeneous structure on the local voidage in the dense region was characterized by introducing the lower bound of local voidage and the heterogeneous influence coefficient.The lower bound of local voidage in bubbling fluidized beds was obtained by revising the correlation for the voidage inside clusters in riser flow.The heterogeneous influence coefficient was determined by an adaptive method based on particle distribution.Thus the local voidage model was set up,named as bubble and emulsion model.The simulation results show that local voidage calculated by bubble and emulsion model is observably lower in the bubble nose region,compared with that calculated by area weighted averaging.Thus drag on particles in this region can be revised to a greater extent.The simulation results corresponding to the proposed model are much more consistent with the experiment observations.Bubble eruption can be captured by simulations with the model.