海洋条件下U型管内倒流特征压降数值模拟

自然循环工况下立式倒 U 型管蒸汽发生器内单相流体存在倒流现象，增大了自然循环流动阻力，减少了有效换热面积，对核动力装置的安全运行造成不利影响。针对该问题，利用 Fluent 软件研究了海洋条件下 U 型管内倒流特征压降的变化规律。结果表明，横摇和起伏特征压降的周期与横摇和起伏运动的周期相同，而纵摇特征压降的变化周期为纵摇周期的一半。横摇和纵摇特征压降波动振幅随横摇和纵摇周期的减小而增大，随横摇和纵摇振幅的增大而增大，起伏特征压降的振幅与起伏周期无关，随起伏加速度振幅的增大而增大。横摇对特征压降的影响最大，起伏次之，纵摇最小。

Numerical Research on Critical Pressure Drop of Reverse Flow in U-Tubes Under Ocean Conditions

The single phase flow in vertically inverted U-tube steam generator under natural circulation can be instable and reverse flow occurs in some tubes.This phenomenon brings some negative effects on the safety operation of nuclear power equipment,such as the enhancement of the flow resistance and the decrease of the effective heat transfer area.The change rules of critical pressure drop of reverse flow in U-tubes under ocean conditions were studied by using Fluent codes.The results show that the periods of critical pressure drop in rolling and heaving motions are the same as the periods of the motions,whereas the period of that in pitching motion is half of the pitching period.The fluctuating amplitudes of critical pressure drop in rolling and pitching motions increase with the decreases of the motion periods and the increases of the motion amplitudes,and the fluctuating amplitudes of critical pressure drop in heaving motion is irrelevant to the heaving period,but it will increase with the increase of heaving acceleration amplitude.Among the three types of motions,the rolling motion has the biggest effect on the critical pressure drop,the heaving comes second and the effect of pitching is minimal.