基于激光截面成像法的气液两相流气泡群特征测量

Measurement of Bubble Group Characteristics of Gas-Liquid Two-Phase Flow by Laser Cross Section Imaging

针对核反应堆热工设计与建模中堆芯气液两相流参数的测算需求,研究了一种基于激光成像的气泡群特征测量方法。在透明模型堆芯外部使用平面激光照射两相流形成横向探测截面,通过高速摄影获取气泡群在该截面处的前向光散射图像,利用圆度值分类法和优化的快速径向对称变换图形分割算法对图像进行处理,有效降低了气泡影像重叠引入的面积计算误差。基于气泡“断层轮廓-速度-形态”的约束关系,完成了气泡垂直速度的求解,最终所提方法实现了瞬时截面含气率测量、截面含气率均值成像、气泡三维形态重建和平均粒径分布计算。

According to the measurement requirements of the gas-liquid two-phase flow parameters in thermal design and modeling of a nuclear reactor,a laser-imaging-based method for measuring the characteristics of bubble groups is investigated.Specifically,a planar laser is used to illuminate the two-phase flow outside the transparent model core to form a transverse detection cross-section,and the forward light scattering images of the bubble groups in this cross-section are obtained by high-speed photography.Then,the images are processed with a roundness classification method and an optimized graph segmentation algorithm of the fast radial symmetry transform to effectively reduce the area calculation errors introduced by the overlapping bubble images.Finally,the vertical velocity of the bubbles is calculated on the basis of the"fault contour-velocity-morphology"constraint of bubbles.Thus,the proposed method achieves the measurement of the instantaneous cross-sectional void fraction,the imaging of the mean value of cross-sectional void fraction,the threedimensional morphology reconstruction of bubbles,and the calculation of average particle size distribution.