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对开式自然循环系统的启动过程进行了实验研究,并详细分析了不同加热功率和不同入口过冷度条件下系统出现的实验现象和流动特性,最后给出了自然循环系统在启动过程中的流动不稳定性边界图。结果如下:在低加热功率下,随着入口过冷度的减小系统会依次经历单相稳定、两相振荡和两相稳定流动;增大加热功率会使系统的两相流动不稳定范围增大,甚至很难形成稳定的两相流动。在两相振荡阶段,系统会出现由闪蒸诱发的不稳定流动以及由沸腾喷发和闪蒸共同诱发的不稳定流动两种模式,这两种不同模式的流动不稳定性均属于密度波不稳定性。
The start-up process of open natural circulation system is studied experimentally, and the experimental phenomena and flow characteristics of the system under different heating power and different entrance undercooling conditions are analyzed in detail. Finally, the natural circulation system is given Flow instability boundary map. The results are as follows: At low heating power, with the decrease of inlet undercooling, the system will sequentially undergo single-phase stabilization, two-phase oscillation and two-phase steady flow. Increasing the heating power will increase the instability of the two- Large, even difficult to form a stable two-phase flow. In the two-phase oscillation phase, the system will have instable flow induced by flashover and unsteady flow induced by both flash eruption and flash evaporation. Both of these two modes have instabilities in flow instability Sex.