竖直圆管中泡状流含汽率径向分布的统计测量方法

为了研究竖直圆管中高含汽率泡状流的含汽率径向分布,设计了一种测量含汽率径向分布的方法.该方法通过统计投影视图中的像素信息得到泡状流的投影含汽率,根据汽泡投影重叠概率计算出截面含汽率在投影面上的边缘分布;再基于竖直圆管中含汽率分布轴对称的假设,使用改进的傅里叶级数展开方法求解Abel逆变换,计算出含汽率沿圆管径向的分布.为验证该方法的有效性,测量了较低含汽率时的泡状流径向含汽率,并与匹配方法的测量结果进行比较.实验结果表明:此方法能得到高含汽率或含汽率近壁分布等其他方法难以测量的含汽率分布.

Statistical Measurement of Radial Void Fraction Distribution of Bubbly Flow in a Vertical Pipe

An image-based method has been developed for measuring the instantaneous radial void fraction distribution in bubbly flows with higher void fractions in a vertical pipe. The method is based on the statistical analysis to shadow images of a bubbly flow, which were obtained using a stereo photographic technique. The projection void fraction distribution was obtained, by counting all pixels of bubble shadow images and considering the overlapping probability of the bubble shadows. Then the instantaneous radial void fraction distribution in the bubbly flow was reconstructed from projection void fraction distributions on the assumption that the radial void fraction distribution is axial symmetrical. An improved algorithm for Abel inversion calculation has been proposed to reconstruct the radial distribution of the local void fraction based on the Fourier method. Finally, the method is checked for the accuracy in the measurement of the radial bubbles distribution by comparing with the labeling method results. The comparison results showed that some special void fraction profiles, such as the wall-peaked or high void fraction distributions that usually cannot be obtained by other methods, could be measured by this method.