高温大颗粒气固流化床流化行为数值模拟

Numerical simulation of hydrodynamic behavior in a high temperature gas-solid fluidized bed with coarse granules

通过数值模拟,对内含直径为3 mm流化颗粒的二维高温流化床开展了研究。其中欧拉途径被用于描述气相运动,而对颗粒相描述则采用拉格朗日途径。采用离散单元法跟踪颗粒在不同时刻位置和速度。结果表明:与300K时相比,1 000 K高温床的临界流化风速有所提高,压降脉动及床层最大膨胀比明显降低。1 000 K时,流化数提高至1.67,高温床内可见到大尺寸的气泡。在气泡之外上、下2个区域中处于气泡对称轴上的颗粒,水平速度具有相反的方向;而y方向上,这二部分颗粒群的速度均向上并大致在10-1m/s范围之内。

In a high-temperature gas-solid fluidized bed with granules of 3 mm diameter, its hydrodynamic behavior was investigated by combined Euler to gas phase and Discrete Element Method to granules motion. The bed used in the simulation was operated at 300 K and 1 000 K. It shows that minimum fluidizing velocity is improved at 1 000 K, whereas degree of pressure fluctuation and bed expansion ratio are obviously decreased compared with 300 K. For a given value of fluidizing number of 1.67, rapid growth of bubbles can be observed in the bed. Granules between regions of the roof and base of bubbles move contrarily in x-direction, however, those granules in y-direction go upward and their values of velocities are approximately in a range of 10^-1m/s at 1 000 K.