Flow instability can cause mechanical oscillations in the equipment as well as periodic changes in the thermal stress, both of which have a great impact on the safety of the reactor. In addition, flow instability can interfere with the control system, making it difficult to capture stable parameters. In this study, to examine the change in the stability of a parallel channel-loop system with natural circulation under asymmetric conditions, the single-loop natural circulation system is taken as the starting point, and the control equations are obtained by using a dimensionless analysis method. The Fourier expansion of displacement term in the control equations is carried out to obtain the Jacobian matrix representing the single-loop natural circulation system. Based on this matrix, the Jacobian matrix model of parallel channel-loop system is constructed. According to the model, the natural circulation stability of parallel channel-loop under different load and resistance difference is analyzed, and the effects of geometric characteristics, coolant and power on the stability boundary under asymmetric condition are examined. The results show that there are two critical Reynolds numbers, and the system becomes unstable when the load difference introduced by the left and right loops is greater than the critical Reynolds numbers. The area of stable region can be increased by increasing the aspect ratio and heating zone length, and reducing the pipe diameter and cooling zone length. Furthermore, the stability boundary of natural circulation is sensitive to the aspect ratio and the length of heating zone. In addition, the stability can be improved within the allowable range of the natural circulation by choosing liquid metal coolant and increasing the pressure drop, and this model cannot accurately describe the changes in the stability boundary at low power. Overall, the above results can serve as useful reference for the design of the parallel channel-loop systems and can be used to improve the stability of natural circulation. The stability boundary can be used to preliminarily judge the stability distribution and the variation trend of the parallel channel-loop system with a certain degree of reliability.

流动不稳定会引起设备的机械振荡以及热应力的周期性变化，这两者对反应堆的安全都有很大影响。此外，流量不稳定会干扰控制系统，使其难以捕获稳定的参数。本研究以单回路自然循环系统为出发点，通过无量纲分析得到具有自然循环的并联渠道回路系统在非对称条件下稳定性的变化。方法。对控制方程中的位移项进行傅里叶展开，得到代表单回路自然循环系统的雅可比矩阵。基于这个矩阵，构建了并行通道环路系统的雅可比矩阵模型。根据该模型，分析了不同负载和阻力差下并联通道回路的自然循环稳定性，考察了几何特性、冷却剂和功率对非对称条件下稳定性边界的影响。结果表明，存在两个临界雷诺数，当左右回路引入的负载差异大于临界雷诺数时，系统变得不稳定。增大纵横比和加热区长度，减小管径和冷却区长度，可以增加稳定区的面积。此外，自然循环的稳定边界对纵横比和加热区长度很敏感。此外，在自然循环的允许范围内，通过选择液态金属冷却剂和增加压降可以提高稳定性，该模型不能准确描述低功率下稳定性边界的变化。综上所述，上述结果可为平行通道-环路系统的设计提供有益参考，可用于提高自然循环的稳定性。稳定性边界可用于初步判断具有一定可靠性的并行通道回路系统的稳定性分布和变化趋势。上述结果可为平行通道-环路系统的设计提供有益参考，可用于提高自然循环的稳定性。稳定性边界可用于初步判断具有一定可靠性的并行通道回路系统的稳定性分布和变化趋势。上述结果可为平行通道-环路系统的设计提供有益参考，可用于提高自然循环的稳定性。稳定性边界可用于初步判断具有一定可靠性的并行通道回路系统的稳定性分布和变化趋势。