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在内径120mm的圆柱形导向管喷动流化床内,实验测定了单相气体流场的时均速度分布和湍流强度分布以及声波对它们的影响。结果表明:采用高速射流作为喷动气时,在卷吸区射流中心速度衰减快,卷吸作用强;进入导向管后中心速度开始下降仍然很快,但在经过较短距离后即趋于稳定,径向速度分布亦趋于稳定但不均匀;环隙速度分布在分布板影响下则较均匀;在喷泉区,刚离开导向管时射流中心速度仍较大,但随高度增加而较快下降,径向速度分布也趋于平缓。导向管区的湍流强度远高于环隙区和喷泉区。声波在导向管喷动流化床内单相气流中传播时衰减很小,并对时均速度几乎没有影响,但可以显著提高气流的湍流强度,且湍流强度的增加幅度随声强增加而加大,随频率增加而减小。湍流强度的增加,可以增强气流对颗粒的分散作用,有利于抑制导向管内粉体偏析,防止被射流破碎后的小聚团在环隙区发生再团聚,减少喷泉区粉体夹带,提高超细粉的流化质量。
In a fluidized bed with a cylindrical guide tube with an inner diameter of 120mm, the time-averaged velocity distribution and the turbulent intensity distribution of the single-phase gas flow field and the influence of the sound waves on them were experimentally determined. The results show that when the high-speed jet is used as the jet gas, the jet center velocity decays rapidly and the entrainment effect is strong at the entrainment zone. The center speed begins to decline rapidly after entering the guide tube, but tends to be stable after a short distance, The radial velocity distribution also tends to be stable but not uniform. The distribution of annular velocity is more uniform under the influence of distribution plate. In the fountain area, the jet center velocity is still larger when it leaves the guide tube, but decreases rapidly with the height increasing. The radial velocity distribution also tends to be flat. The turbulence intensity in the guide zone is much higher than that in the annulus zone and the fountain zone. The acoustic wave attenuation is small when it propagates in the single-phase flow in the spout-fluidized bed with almost no effect on the average hourly velocity, but it can significantly increase the turbulence intensity of the turbulent flow and the increase of the turbulence intensity increases with the sound intensity Large, decreases with increasing frequency. The increase of turbulent intensity can enhance the dispersion effect of air flow on the particles, which is helpful to suppress the segregation of powder in the guide tube, prevent the agglomeration of the small agglomerates in the annular zone after the jet is broken, reduce the entrainment of powder in the fountain area, and improve the ultrafine Fluidized mass of powder.