For the optimal design and safety evaluation of sodium-cooled fast reactors (SFRs), the risk estimation of tube failure in the steam generator (SG) via numerical analysis is very important. This requires the understand of the droplet entrainment behavior induced by high-speed steam injection from the heat transfer tube into the liquid sodium in the shell; however, there is a lack of detailed information such as droplet diameter and velocity due to measurement difficulties. Therefore, this study aims to understand the droplet entrainment caused by high-speed gas injection into a liquid pool and to obtain experimental data for developing proper analysis models. Air was injected into a water pool at various air superficial velocities and the droplets were visualized via the frame-straddling method, obtaining clear images of the droplet generation from the gas–liquid interface. The droplet entrainment was caused by the liquid phase stretching and tearing due to the gas jet shear stress. Based on the visualization results, the droplet diameter and velocity were simultaneously measured at various locations through image processing; the number of fast droplets decreased as the diameter increased. The droplet diameter increased along with the distance from the nozzle. At the center of the jet, the droplet velocity was higher near the nozzle and lower at larger distances. The droplets tended to be larger and slower near the jet interface than near the center of the jet. When the jet interface fluctuation became larger, the droplet diameter increased, while the velocity decreased. Therefore, to develop droplet entrainment analysis models for the risk evaluation of tube failures in SFR SGs, the effect of the jet interface fluctuation on the droplet behavior must be evaluated.

对于钠冷快堆（SFR）的优化设计和安全评估，通过数值分析对蒸汽发生器（SG）管子故障的风险评估非常重要。这需要了解从传热管向壳内液态钠中高速注入蒸汽引起的液滴夹带行为；然而，由于测量困难，缺乏诸如液滴直径和速度等详细信息。因此，本研究旨在了解由高速气体注入液体池引起的液滴夹带，并获得实验数据以开发适当的分析模型。空气以不同的空气表观速度注入水池，并通过框架跨法观察液滴，从气液界面获得液滴生成的清晰图像。液滴夹带是由气体喷射剪切应力引起的液相拉伸和撕裂引起的。根据可视化结果，通过图像处理在不同位置同时测量液滴直径和速度；快速液滴的数量随着直径的增加而减少。液滴直径随着距喷嘴的距离增加而增加。在射流的中心，喷嘴附近的液滴速度较高，而在较远的距离处较低。液滴在射流界面附近比在射流中心附近趋于更大和更慢。当射流界面波动变大时，液滴直径增加，而速度降低。所以，