蒸汽直接喷射冷凝过程中两相流特性的数值研究

Numerical Investigation for Two-Phase Flow Characteristics in Direct Steam Injection Condensation Process

为了获得泄压系统中蒸汽直接喷射冷凝过程两相流特征的变化规律,采用数值模拟方法,结合VOF两相流模型和冷凝相变模型,通过控制变量的方式研究了过冷水温和蒸汽入口压力对蒸汽喷射直接接触冷凝过程的影响,分析了不同工况下的冷凝两相流场特征。结果表明:过冷水温和蒸汽入口压力均对喷射水箱中的蒸汽羽流特征具有显著影响,更高的过冷水温和入口压力均会导致更大的蒸汽羽流长度和影响区域;当过冷水温较低时,沿喷射轴线方向上蒸汽温度逐渐减小,而在过冷水温较高时,蒸汽温度先增加然后快速降低,这是因为来不及冷凝的蒸汽滞止在两相混合区之前;随着蒸汽入口压力的降低,纯蒸汽区越短,且两相混合区的蒸汽体积分数下降速度越快。

To reveal two-phase flow characteristics of direct steam injection condensation process in pressure relief system,combining VOF two-phase flow model with condensation phase change model,the influences of initial subcooled water temperature and steam inlet pressure on the direct contact condensation process of steam jet are numerically simulated and the characteristics of condensation two-phase flow field in different cases are analyzed.The results show that both subcooled water temperature and steam inlet pressure significantly affect the characteristics of steam plume in tank;higher subcooled water temperature and initial steam pressure lead to larger steam plume length and influence area.When the temperature of subcooled water is low,the steam temperature along the jet axis decreases monotonically and when the temperature of subcooled water is high,the steam temperature along the jet axis first increases and then decreases rapidly,which results from stagnation of the steam before the two-phase zone.With the decreasing steam inlet pressure,the pure steam zone gets shorter and the steam volume fraction decreases faster in the two-phase mixing zone.