水平气液两相流流型图像信息递归特征分析

On the streaming video of all typical flow pattern filmings on the experiment system by the high-speed video camera,the information of a single-frame was extracted and made into time-series.The series was analyzed with the non-linear chaotic recurrence plot(RP),less used in the last years.It was combined with the average diagonal length and Shannon entropy of recursive features changed after the increase of gas superficial velocity.The results showed that the information entropy of flow image combined with RP could well characterize the evaluated tract of gas-liquid two-phase flow patterns.At the same time,the information well characterized the volume fraction of all kinds of gas-liquid two-phase flow patterns.The average diagonal length and recursive Shannon entropy of recursive features all increased first and then decreased with the increase of gas superficial velocity,and it reflected the transition of the mechanisms of five typical flow patterns from the recursive characteristics.

小通道并联管干涸热动力学特性实验

针对小通道并联管在沸腾传热过程中传热不稳定的问题,对小通道并联管在干涸时的热动力学特性进行研究。首先,通过观察小通道并联管内干涸点前后流型的转变,将流型分成环状预警区、干涸初始点区和雾状干涸区3个区域。对3个流型下并联通道沸腾传热过程中通道内工质干度和传热系数的变化进行分析,发现随着干涸的发展,通道沸腾传热系数下降明显。然后,对通道3个流型下的压降信号,通过自适应最优核时频表示法(AOKTFR)、自回归(AR)模型功率谱分析法和递归图分析法进行分析,发现在干涸初始点区,通道内反复出现干涸现象,且回流现象严重。最后,通过对递归图分析法中特性参数归纳总结,得到干涸初始点区与环状预警区、雾状干涸区的区别,实现通过压降信号检测干涸的目的。研究结果可对小通道沸腾传热领域中的热动力学特性进行补充和完善。