气-固环流反应器内瞬态流体力学特性的数值模拟

Numerical simulation of transient hydrodynamics in gas-solid airlift loop reactor

采用双流体模型和颗粒动力学理论,并考虑颗粒团聚现象对气固相间曳力的影响,对气-固环流反应器内的流体力学特性进行了数值模拟。模拟的时均固含率和颗粒速度与实验数据具有较好一致性,验证了模拟方法的可靠性。模拟结果表明:气-固环流反应器内瞬态固含率的分布具有典型聚式流态化的非均匀特征;压力脉动沿床层轴向的分布在一定程度上定性反映了气泡运动的信息;颗粒速度的时间序列和概率密度分布函数表明,床层各径向位置均存在颗粒的向上、向下运动,颗粒主体在床层内向上运动的同时还存在微观的内循环运动,模拟值为颗粒时均速度的径向非均一性宏观分布提供了合理的微观解释。

The hydrodynamics in a gas-solid airlift loop reactor were simulated by using two-fluid model and granular kinetics theory in this paper.The gas-solid inter-phase drag force function included in the two-fluid model was modified accounting for the interparticles clustering.The simulated time averaged values of solid fraction and particle velocity agree well with the experimental data,verifying the feasibility of the numerical simulation method.The simulated results demonstrate that the profiles of transient solid fraction present the similar heterogeneous feature of aggregative fluidization usually occurred in normal fluidized beds.The axial profiles of bed pressure fluctuation qualitatively reflect the information about the bubble movement in a certain extent.The time series of particle velocity and their probability density functions display that both the particle upward and downward movement appears at each local bed position.The microcosmic internally circulating flow pattern of particles exists simultaneously when the mainstream of particles move upward in the bed.The particle transient velocity profiles offer a microcosmic interpretation for the macroscopical lateral nonuniform distribution of time averaged particle velocity.