Development of a Method of Evaluating Mechanical Properties of Aerated Powder

研制了充气粉末粘附性和聚集性的测试装置，研究了这些性能与床层鼓泡、流道和团聚流态化等流动特性的关系，得到了以下结果：(1)利用三维流态化实验装置，对不同粒度的电熔氧化铝粉末进行了床层压降测量和目视观察。结果表明：1)细粉存在三种流态化模式；A型：在低气速下开槽，然后在高气速下鼓泡(完全流态化)。B型：在低气速下形成裂纹，然后形成圆顶，聚集的颗粒被流态化。C型：在低气速下形成圆顶，然后在高气速下鼓泡。本研究提出的下列“流态化指数(FI)”可以有效地评价充气粉末的力学性能。uc：完全流态化速度Up：沉降速度DELTAP：压降W：粉粒重量A：床层横截面3)FI与溅射角作为粉末粘附性的指标密切相关。结果利用二维流化床对A型粉末进行了流态化试验。得到了以下结果：1)在通道顶端形成气泡。通道高度随气速的增加而减小。2)形成的气泡大小与气速和通道高度无关，是粉末颗粒所固有的。3)形成的气泡尺寸随气速增大而增大。4)通道高度的实验结果与本研究提出的估算模型符合得很好。

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.