不同管口浸没方式下气泡运动特性实验研究

Experimental Study on Motion Characteristics of Bubbles in Different Submerged Modes of Nozzle

为了对比研究不同管口浸没方式下气泡的运动特性,通过可视化实验揭示了顶部、侧部和底部三种管口浸没方式下的气泡上升运动过程,得到了气泡形状、等效直径、位移、速度以及高宽比的变化规律,通过获得相邻气泡质心间垂直距离定量表征了气泡在上升过程中的紊乱程度。研究结果表明,顶部管口浸没方式下的气泡形态明显区别于侧部和底部管口浸没方式,其气泡高宽比变化相对较稳定;随着进气流量的增大,气泡间的碰撞几率逐渐增大,其运动紊乱程度加强;气泡上升呈现出直线形、折线形和螺旋形运动轨迹;折线形运动轨迹下的气泡水平位移、气泡速度随上升高度的增加均呈现出较为明显的周期性波动;直线形轨迹下的气泡水平位移以侧部浸没方式下为最大;折线形运动轨迹下的气泡水平速度变化幅度以顶部浸没方式下为最大;螺旋形运动轨迹下的气泡垂直速度变化以底部浸没方式下最为剧烈。

The rising process of bubbles is performed by a visualization experiment for studying the motion characteristics of the bubbles formed at the top-submerged,side-submerged and bottomsubmerged nozzle.The variation rule of the shape,equivalent diameter,displacement,velocity and aspect ratio of bubbles are obtained.The disorder degree in the rising process of bubbles is characterized quantitatively by the vertical distance between adjacent bubbles.The results show that the shape of bubbles formed at the top-submerged nozzle is obviously different from the side-submerged and bottom-submerged nozzles.The variation of the aspect ratio of bubbles is relatively stable in the top-submerged nozzle mode.The collision probability between the bubbles gradually increases and the disorder degree of the movement of bubbles becomes more and more strong with the increase of the gas intake flow.The rising motion of bubbles present three trajectories:rectilinear trajectory,zigzag trajectory and helical trajectory.There is an obvious periodic fluctuations of the horizontal displacement and the velocity of bubbles with the zigzag trajectory.The horizontal displacement of bubbles with the rectilinear trajectory in the side-submerged nozzle mode is the largest.The variation amplitude of the horizontal velocity of bubbles with the zigzag trajectory in the top-submerged nozzle mode is the largest.The variation of the vertical velocity of bubbles with the helical trajectory in the bottom-submerged nozzle mode is the most violent.