ABSTRACT

Distorted inflow caused by the complex structure of the steam generator channel head (SGCH) occurs at the entrance to the reactor coolant pump (RCP) in the AP1000 system, which may generate impeller cracks and result in deterioration of performance and stability. In this paper, to analyze the influence of distorted inflow on flow properties of the RCP, the inflow distortion characteristics are studied by a full three-dimensional steady and unsteady numerical simulation. The simulation model was verified experimentally by testing the RCP with a straight pipe and a channel head at different flow rates. Using this model, the inlet distortion was quantified and the variation law of different distortion was obtained. The results showed that a non-uniform swirling flow under lateral pressure differences was formed when the pump was coupled with a channel head instead of a straight pipe, leading to the destruction of circular symmetry of the inflow field. Further increasing the tube length alone was not effective in improving the inflow field of the RCP, and the inlet swirl effect always existed. As the distorted flow entered the pump with a pair of vortices, the chaotic flow field imposed a non-uniform stress on each blade of the impeller, resulting in the unevenly distributed flow rate of each flow-path of the blade. Then, in the flow channels of the impeller, there were obvious asymmetrical vortex core regions, even in opposite directions, which originally formed in the inflow field of the RCP and raised the risk of blade fatigue failure. Owing to the significant effects of inflow distortion produced by the SGCH, understanding the mechanism of non-uniform inflow characteristic is of great value to the design and optimization of the RCP.

Abbreviations: RCP: reactor coolant pump; SG: steam generator; SGCH: steam generator channel head

摘要

在AP1000系统的反应堆冷却剂泵（RCP）的入口处会发生由蒸汽发生器通道头（SGCH）的复杂结构引起的流入变形，这可能会产生叶轮裂纹，并导致性能和稳定性下降。为了分析流入的变形对RCP流动特性的影响，通过完整的三维稳态和非稳态数值模拟研究了流入变形特性。通过用不同流量的直管和通道头测试RCP，通过实验验证了仿真模型。利用该模型对进气道变形进行了量化，得出了不同变形的变化规律。结果表明，当泵与通道头而不是直管耦合时，在侧向压力差下会形成不均匀的旋流，从而导致流入场的圆形对称性破坏。仅进一步增加管长并不能有效地改善RCP的入流场，并且始终存在进气涡流效应。当扭曲的流通过一对涡流进入泵时，混乱的流场在叶轮的每个叶片上施加了不均匀的应力，从而导致叶片的每个流路的流量分布不均匀。然后，在叶轮的流道中，即使在相反的方向上，也存在明显的不对称涡旋核心区域，这些区域最初形成在RCP的流入场中，并增加了叶片疲劳失效的风险。

缩写： RCP：反应堆冷却剂泵；SG：蒸汽发生器；SGCH：蒸汽发生器通道头