颗粒物质在竖直管中下行蠕动流动的实验测量

颗粒流蠕动行为是颗粒物质在竖直管中流动时常见的一种流动现象,其产生机理较复杂。为此,本文在在内径为150mm、高为5000mm的竖直管实验装置上,以FCC催化剂为固体颗粒物料,采用PV6型颗粒速度测量仪,测量不同颗粒流率下竖直管中的颗粒下行蠕动流动速度以及颗粒固含率,系统地考察了颗粒物质在竖直管中下行流动时的蠕动流动特性及产生机理。实验结果表明,颗粒物质在竖直管中下行流动时的流动行为可划分为两种形式。在颗粒流率较小时,颗粒物质下行速度呈现脉冲式变化,有速度停滞,可称之为蠕动I型流动。随着颗粒流率的增加,颗粒下行速度停顿消失,但仍是起伏变化,为蠕动II型流动。当颗粒流率增大到一定值后,颗粒物质下行蠕动行为消失,转变为流化流动。颗粒物质下行的蠕动行为是出口区颗粒成拱与崩塌、颗粒与器壁滑动摩擦和颗粒力链作用的综合反映。

Experimental Measurement of Downstream Creeping Flow of Granular Matter in a Vertical Pipe

Particle flow creeping behavior is a common flow phenomenon of granular matter flowing downstream in a vertical pipe, which has a complex formation mechanism. Therefore, taking FCC catalyst as the granular material, using a PV6 type particle velocimetry, systematical investigation was carried out in a vertical pipe with internal diameter of 150 mm and height of 5000 mm to measure the downstream creeping flow velocity and particle solid content of granular matter with different particle flow rates, at the same time, to observe its creeping flow characteristics and formation mechanism. Experimental results indicate that the flow behavior of downstream flowing granular matter in a vertical tube can be divided into two forms. When particle flow rate is small, downstream flow velocity of granular matter presents pulse variation, and there is speed stagnation. So it is called type I creeping flow. Along with the increase of particle flow rate, the speed stagnation disappears, but velocity variation still exists. So it is called type II creeping flow. When particle flow rate increases to a certain value, downstream creeping flow disappears and creeping flow converts into fluidized flow. The creeping flow behavior of granular matter in a vertical pipe is a comprehensive presentation due to particle arching and collapse in the outlet area. Meanwhile, the sliding friction force between particles and pipe wall and the force chain between particles also contribute to the creeping flow of granular matter.