转运点落料诱导气流非线性变化影响因素

Nonlinear variation influence factors for induced airflow of bulk materials in transfer station

转运点诱导气流是散料输送过程扬尘的主要诱因,本文以半封闭转运点为研究对象,通过对落料质量流量mp、有效诱导气流量Q、落料高度h及密闭罩阻力系数ξ等的研究,探讨转运点落料诱导气流非线性变化影响因素。结果表明：诱导气流随物料质量流量增加而增加;受物料相互作用对气流流动的影响和落料管有效流动空间变化影响,有效诱导气流随质量流量增加而减小,在量值上与物料质量流量的-0.77次方近似成正比;转运点落差的有限性使落料过程处于加速阶段,物料曳力系数处于Allen区,诱导气流速度随落料高度的变化趋势基本相同;对平均阻力系数ξ=2.12的密闭罩系统,诱导气流速度与下落高度的0.86次方近似成正比;物料下落初期颗粒间相互碰撞、接触等作用较强,对3.6~11.1 mm的落料,诱导气流随粒度增大有减小趋势,但关联性较弱。

Induced airflow of free-falling particles process serving as the chief temptation of dust fugitive in transfer station of conveying process for bulk materials. The semi-closed transfer station was chosen as the study object in the present paper. Nonlinear variation influence factors for induced airflow were explored through the study of mass flow rate of bulk material mp, specific induced air flow Q, drop height h and resistance coefficient of suction hood ξ. The primary conclusions are as follows： With the mass flow increasing, the induced airflow increases, and the specific induced air flow decreases due to the influences of the interaction between the particles for airstream and the change of effective flow space of blanking tube. The specific induced air flow is found to be proportional to the mass flow raised to the power of approximately-0.77. Owing to the finiteness of the drop height of the transfer station the falling particles is in the acceleration phase all along. The drag coefficient of falling particles is in the Allen area. The change trends of induced airflow velocity with the change of drop height are generally similar. On one suction hood system, which drag coefficient is 2.12, the induced airflow velocity is approximately 0.86 th power of drop height. On initial stage of material falling process, because of the strong impact and contact roles between particles whose size are 3.6~11.1 mm, the induced airflow velocity has a tendency to decrease with increasing particle size. But the relatedness between induced airflow velocity and particle size is appreciably weak.