循环流化床中颗粒旋转特性

Particle rotation characteristics in CFB riser

利用由高速数字摄影设备及大功率激光构成的测试系统在一截面为200mm×200mm、高为4m的冷态循环流化床实验台上进行了床内颗粒旋转特性的实验研究.对在距布风板3·54m高度的稀相区的1/4截面内13个测试点拍摄获得的图像序列利用Matlab、PhotoShop和ACDSee软件进行分析处理,采用人工直接判别获得颗粒转速,用双帧频验证法进行颗粒转速校验.结果表明:循环流化床气固两相流中固相颗粒普遍存在旋转现象,截面边壁区内的颗粒平均转速高于中心区域;粒径小或径向速度大的颗粒,其平均转速较大,反之亦然;不规则颗粒的平均转速明显高于球形颗粒;当空截面气体速度Vg=5m·s-1,固体质量循环流率Gs=1·5kg·m-2·s-1,玻璃珠颗粒平均粒径dp=0·5mm时,颗粒转速最高可达2000r·s-1,平均转速300r·s-1.

By using an advanced measurement system composed of a high-speed digital video camera and a high-power laser sheet, an experimental research was carried out on the particle rotation characteristics in a cold Circulating Fluidized Bed （CFB） riser with square cross-sectional area of 200 mm × 200 mm and height of 4 m. Particle movement images were analyzed with Matlab, PhotoShop and ACDSee software, captured at 13 measurement points in a quarter of a cross-section in the upper dilute phase area of the CFB riser. Particle rotation speed was observed and checked by the dual-frequency method. The results showed that the particle rotated when moving along the riser in gas-solid two-phase flow of the CFB riser, and the average particle rotational speed in the wall area was higher than that in the center area in the testing crosssection. Those particles, with either relatively smaller diameter or higher radial component of velocity, were inclined to have a higher rotational speed. The average rotational velocity of irregular particles was obviously higher than that of regular ones. Average particle rotational velocity in the CFB riser was 300 r ·s^-1 and maximum rotational velocity was 2000 r ·s^-1 at superficial gas velocity Vg = 5 m ·s^-1 , recycling solids mass flux Gs=1. 5 kg ·s^-2·s^-1 and particle average diameter dp=0.5 mm.