基于时变性聚团识别方法的高密度循环流化床内聚团分布特性

Characterization of cluster distribution in a high-density circulating fluidized bed based on a time-varying cluster identification threshold

为研究高密度提升管内的聚团分布特性,在18 m高循环流化床提升管系统中测定了不同固体循环速率下(G_(s)=100~1800 kg·m^(-2)·s^(-1))的瞬时颗粒浓度。采用基于时变性的聚团识别方法对聚团进行识别,进而得到了聚团浓度、聚团持续时间和聚团速度在提升管中的分布。研究结果表明,高密度循环流化床中的颗粒浓度和聚团特性参数和与低密度循环流化床相比存在较大差异。高密度条件下,提升管内聚团浓度最高可达0.41。聚团持续时间最高可达5.5 ms。提升管截面内的聚团净向上运动,r/R=0.949时,聚团的净运动速度高达1.83 m·s^(-1)。此外,在极高的颗粒循环速率下(G_(s)=1800 kg·m^(-2)·s^(-1)),聚团特性参数的轴径向分布变得更均匀。

To investigate the characteristics of clusters within a high-density riser,measurements of the transient solids holdup were carried out at different solids circulation rates(G_(s)=100~1800 kg·m^(-2)·s^(-1))in an 18 m high circulating fluidized bed riser.Clusters were identified by a time-varying threshold with cluster solids holdup,cluster duration time and cluster velocity.Results indicated that time-averaged sol-ids holdup and cluster characteristics in the high-density circulating fluidized bed were significantly differ-ent from those in low-density circulating fluidized bed.At high density conditions,cluster solids holdup was higher up to 0.41.Cluster duration time was up to 5.5 ms.All clusters had a net upward movement with the velocity up to 1.83 m·s^(-1)at r/R=0.949.Moreover,the axial and radial distribution of the clus-ter was even at high solids circulation rate with G_(s) up to 1800 kg·m^(-2)·s^(-1).