Effects of Aeration on the Flow and Mixing States of Fluids Possessing Yield Stress in a Stirred Vessel when a Cavern Region Occurs

在装有凹面叶轮的搅拌槽中，定量研究了曝气量q[L/分钟]和叶轮转速n[n^-1]等条件对具有屈服应力的浆状流体混合速度的影响。利用图像分析的方法，根据未混合面积与容器整个垂直面积之比的动态变化，定义了混合速率常数k_S[n^&lt；-1]。结果表明，无论q值如何，当转速大于某一值时，随着n的增加，ks急剧增加，这对改善混合状态是有效的。研究还发现，这一改善是由于叶轮排放流量引起的气泡漂浮模式发生了变化。

In this study, the effects of aeration and agitation conditions, such as aeration rate, Q[L/min], and impeller rotational speed, n[n^<-1>], on the mixing rate for slurry-like fluids possessing a yield stress were quantitatively investigated in a stirred vessel equipped with a concave impeller, when a Cavern region occurs. We defined the mixing rate constant, k_s[n^<-1>], based on the dynamic change of the ratio of the unmixed area to the whole vertical area of the vessel, using an image analysis method. It was found that regardless of the value of Q, ks increased drastically with an increase in n, when the rotational speed was above a certain value, and this was effective in improving the mixing state. It was also found that this improvement was attributable to the fact that the floating pattern of the bubbles due to the discharge flow from the impeller changed.