Development of a Method of Evaluating Mechanical Properties of Aerated Powder

研制了充气粉料粘附性和凝聚性测定装置，并利用该装置研究了充气粉料粘附性和凝聚性与床层流动特性（鼓泡、沟流和凝聚流化）的关系，得到了以下结果。(1)结果利用三维流化床对不同粒度的电熔氧化铝粉体进行了流化试验，包括床层压降的测定和外观观察。结果表明：1）细粉存在三种流化模式：A型：低气速下的沟流，其次为鼓泡B型：在较低的气体速度下形成裂纹，随后形成圆顶，其中团聚颗粒被流化C型：在较低的气体速度下形成圆顶，然后在较高的气体速度下鼓泡。uc：完全流化速度up：沉降速度DELTAP：压降W：粉末重量A：流化床截面积FI与作为粉料粒度指标的刮刀角密切相关。(2)结果利用二维流化床对A型粉进行了流化试验。结果表明：（1）通道顶端形成气泡;通道高度随气流速度的增加而减小; 2）气泡尺寸与气流速度和通道高度无关，是粉末颗粒固有的尺寸; 3）气泡尺寸随气流速度的增加而增大; 4）通道高度的估算模型能很好地描述实验结果。

Equipments for measuring the adhesive and aggromarative properties of aerated powder were manufactured and the relations between these properties and the flow characteristics of bed such as bubbling, channeling and agglomerating fluidization were investigated by using the equipments.The following results were obtained.(1) Results by using a three dimensional fluidized bedFluidization tests including the measurement of bed pressure drop and visual observation were conducted for fused alumina powder with various particle size. The results were as follows :1) Three types of fluidization pattern exist for fine powder ; Type A : channeling at lower gas velocity followed by bubbling (complete fluidization) at high gas velocity Type B : crack-forming at lower gas velocity followed by the formation of domes where aggromarating particles are fluidized Type C : dome-forming at lower gas velocity followed by bubbling at higher gas velocityThe following "Fluidization Index (FI)" proposed in this research is effective for evaluating a mechanical property of aerated powder.uc : complete fluidization velocity up : settling velocity DELTAP : pressure drop W : powder weight A : bed cross section3) FI is closely related to spatula angle as an index of adhesiveness of powder.(2) Results by using a two dimensional fluidized bedFluidization tests of type A-powder were conducted. The following were obtained.1) Bubbles form at the tip of channels. Channel height decreases with gas velocity.2) The size of bubbles formed is independent of gas velocity and channel height, and is inherent to powder particles.3) The size of bubbles formed increases with FI.4) The experimental results of channel height is well described by an estimative model proposed in this research.