非对称条件下双环路自然循环稳定性分析

In order to study the change of the stability of the double-loop natural circulation under asymmetric conditions, starting from the single-loop natural circulation heat-carrying system, a dimensionless analysis method is adopted. The displacement terms in the dimensionless control equations of the single-loop natural circulation are expanded by Fourier, thus obtaining the Jacobi matrix characterizing the single-loop natural circulation heat-carrying system and verifying it. On this basis, a double-loop Jacobi matrix analysis model is constructed. Based on the constructed model, the stability analysis of the double-loop natural circulation under different load differences and resistance differences is carried out respectively, as well as the influence of the loop geometric characteristics on the stability boundary. The results show that for a certain double-loop system, there are two critical Reynolds numbers. When the load difference introduced into the left and right loops is greater than these two critical Reynolds numbers, the system will become unstable. Increasing the aspect ratio, reducing the pipe diameter, increasing the length of the heating section and reducing the length of the cooling section can increase the range of the loop stability region, and the stability boundary of the reactor loop is more sensitive to the aspect ratio of the loop and the length of the heating section; in addition, within the allowable range formed by the natural circulation loop, increasing the loop pressure drop can improve the system stability.

为研究非对称条件下双环路自然循环稳定性的变化,以单环路自然循环载热系统为起点,采用无量纲分析方法,将单环路自然循环的无量纲控制方程组中关于位移项进行傅里叶展开,从而得到表征单环路自然循环载热系统的雅克比(Jacobi)矩阵,并进行验证。在此基础上,构建了双环路Jacobi矩阵分析模型,基于所构建的模型,分别开展不同负荷差和阻力差下双环路自然循环稳定性分析,以及回路几何特征对稳定性边界的影响。结果表明,对于某一双环路系统而言,存在2个临界雷诺数,当左、右环路引入负荷差大于这2个临界雷诺数时,系统将会变得不稳定。增大高径比、减少管道直径、增加加热段长度和减少冷却段长度可以增加回路稳定性区域范围,且反应堆回路稳定性边界对环路高径比、加热段长度较为敏感;此外,在自然循环回路形成的允许范围内,增加环路压降可以提高系统稳定性。