湍流发生器中气泡水平向心运动试验

Experiment on centripetal motion of air bubble in turbulence generator

通过理论分析和试验测量,研究气泡在湍流发生器中的气液两相流运动特征.通过简化气泡在旋转流场中的运动,分析气泡在湍流发生器中的受力情况,推导气泡在运动过程中的速度以及运动轨迹方程,分析了气泡运动的动力学特性.搭建了一套可视化两相流测试平台,采用高速摄影技术拍摄气泡在湍流发生器中的运动图像序列.编制图像处理程序,追踪目标气泡,获取气泡特征参数,得到了直径分别为0.8,1.5,1.9 mm气泡在湍流发生器中不同转速(80,130,200r/min)下的瞬态运动轨迹.研究结果表明:水平运动过程中,气泡的径向位置与其转过的角度成自然指数函数关系,且随着气泡的直径和旋转角速度的增加而迅速减小;湍流发生器旋转速度的增大有利于气泡的加速向心运动;直径较大的气泡率先到达旋转轴面.试验结果与理论分析结果基本吻合,获得了影响湍流发生器中气泡向心运动的关键因素,为进一步的研究提供参考.

The motion characteristic of air bubble was investigated analytically and experimentally.The forces on an air bubble were analyzed and its velocity and trajectory equations were derived,the unsteady motion characteristics of air bubble were studied. An experimental set-up was established to visualize the two-phase flow field of air and water. The air bubble motion images in a turbulence generator were taken by making use of high speed photography technology. The unsteady motion trajectory of the air bubbles with diameters 0. 8,1. 5 and 1. 9 mm were obtained at 80,130 and 200 r/min generator rotational speeds,respectively,by using image processing method. It was found that the radial position of an air bubble is related to the rotational angle of the turbulence generator with an exponential function,and decreased rapidly with increasing air bubble diameter and generator rotational speed.The results reveal that an increased generator rotational speed can accelerate air bubble to move cen-tripetally and the air bubbles with larger diameter can arrive at the rotating hub by taking the lead. The experimental observations were in agreement with analytical results basically,and the key factors influencing centripetal motion of air bubble were identified,providing a base for further study.