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提出了一种新型下行管入口结构,并采用计算流体力学对这种下行管入口结构的流体动力学进行数值模拟。对气固两相流采用双流体模型,其中采用颗粒动理学模型描述固相粘度和固相压力。模拟结果表明新型下行管入口区相对周围其它区域为负压区,气固初始接触区的流体被抽吸进入下行管。下行管入口段颗粒浓度在径向上的分布呈中心高、边壁低的分布,随着轴向位置的增加,颗粒逐渐向边壁方向扩散,使得颗粒浓度在径向上分布趋向均匀。气固初始接触区颗粒浓度相对较高。颗粒在下行管中运动历程可分为三个阶段:加速段、减速段和恒速段,这与气固并流接触入口结构的颗粒运动历程不同。
A new type of downcomer inlet structure is proposed, and the fluid dynamics of the downcomer inlet structure is numerically simulated by computational fluid dynamics. A two-fluid model is used for gas-solid two-phase flow, in which the particle-kinetic model is used to describe the solid-phase viscosity and the solid-phase pressure. The simulation results show that the inlet area of the new downcomer is in negative pressure area relative to the other surrounding areas, and the fluid in the initial contact area of gas-solid is sucked into the downpipe. The radial distribution of the particle concentration in the downcomer tube center is high, the distribution of the wall is low, with the axial position increases, the particles gradually spread to the side wall, so that the particle concentration in the radial distribution tends to be uniform. The gas-solid initial contact zone particle concentration is relatively high. Particles in the down tube movement history can be divided into three stages: acceleration, deceleration and constant velocity segment, which is different from the gas-solid cocurrent contact inlet particle structure.