Study on Jet Mixing Characteristics of Lead-Bismuth Eutectic Cooled Reactor Assembly Head Based on CFD Method
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摘要: 在铅铋堆上腔室内，不同功率组件流出的铅铋搅混过程中流体温度波动可能导致固体结构发生热疲劳，危害铅铋堆运行安全。本文基于计算流体动力学（CFD）方法，建立了适用于铅铋堆组件操作头射流模拟的计算模型并通过实验数据进行了验证，之后对不同入口参数的操作头射流工况进行了模拟。研究结果表明：入口温差的增加会导致操作头下游轴向截面上温度分布不均匀性显著增加，且影响范围持续到测量柱的位置，在计算工况范围内，温差每减小20 K时，下游各个截面上温度均方根约减小23.5%；入口速度增加使得二次流增加，但是二次流强度会减小，在计算范围内搅混程度随入口速度增加呈现先减小后增大的变化趋势。本文可为铅铋堆组件操作头下游流场分析、操作头结构优化设计和堆芯流量分配设计等研究提供参考。
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关键词:
- 射流搅混 /
- 堆芯出口 /
- 铅铋合金 /
- 计算流体动力学（CFD）
Abstract: In the upper chamber of the Lead-Bismuth Eutectic (LBE) cooled reactor, fluid temperature fluctuations during the LBE mixing process from different power assemblies may lead to thermal fatigue of the solid structure, threatening the safety of LBE reactor operation. Based on the Computational Fluid Dynamics (CFD) method, this paper established a computational model suitable for the jet simulation of the LBE reactor assembly head and validated it through experimental data. Then, simulations of jet flow conditions with various inlet parameters were carried out. The research results show that the increase in the inlet temperature difference will lead to a significant increase in the temperature distribution inhomogeneity on the axial section downstream of the assembly head, and the influence range continues to the position of the measuring column. Within the calculation range, when the temperature difference decreases by 20 K, the root mean square temperature of each downstream section decreases by approximately 23.5%. The increase in inlet velocity causes the secondary flow to increase, but the intensity of the secondary flow will decrease. Within the calculation range, the degree of mixing first decreases and then increases as the inlet velocity increases. This paper can provide reference for research on flow field analysis downstream of the assembly head, structural optimization design of the assembly head, and LBE reactor core flow distribution design.-
Key words:
- Jet mixing /
- Core outlet /
- Lead-Bismuth Eutectic /
- CFD
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图 3 计算结果与实验测量值的对比
R—与实验段轴向中心线的距离
Figure 3. Comparison between Calculated Results and Experimental Measurements
图 4 实验段内温度及流线分布
Figure 4. Temperature and Streamline Distribution in the Experimental Section
图 11 工况1、2、3温度均方根及搅混程度分布
Figure 11. Root Mean Square of Temperature and Distribution of Mixing Degree for Cases 1, 2 and 3
图 12 工况1、2、3二次流及二次流强度分布
Figure 12. Secondary Flow and Secondary Flow Intensity Distribution for Cases 1, 2 and 3
图 13 工况1、4、5二次流及二次流强度分布
Figure 13. Secondary Flow and Secondary Flow Intensity Distribution for Cases 1, 4 and 5
图 14 工况1、4、5温度均方根及搅混程度分布
Figure 14. Root Mean Square of Temperature and Distribution of Mixing Degree for Cases 1, 4 and 5
表 1 铅铋合金物性
Table 1. Physical Properties of Lead-Bismuth Eutectic
物理量 表达式 ρ/(kg·m−3) ρ=11096−1.3236T cP/(J·kg−1·K−1) $ c_P=159-2.72\times10^{-2}T+7.12\times10^{-6}T^2 $ λ/(W·m−1·K−1) $ \lambda=3.61+1.517 \times 10^{-2} T-1.741 \times 10^{-6} T^{2} $ μ/(Pa·s) $\mu=4.94 \times 10^{-4} \exp \left(\dfrac{754.1}{T}\right) $ 
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表 2 实验段计算边界条件设置
Table 2. Calculation Boundary Conditions of Experimental Section
边界 边界条件 参数 参数值 入口 流量入口 流量/(kg·s−1) 1.3 出口 压力出口 压力/Pa 0 侧壁面加热区域 定热流密度边界 热流密度/(W·m−2) 36396.48 侧壁面非加热区域 定热流密度边界 热流密度/(W·m−2) −190.86 其余壁面 绝热边界
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表 3 三操作头模型计算工况
Table 3. Calculated Conditions for Three-head Model
工况 低温铅铋 高温铅铋 温差/K 速度/(m·s−1) 温度/K 速度/(m·s−1) 温度/K 1 0.5 573 0.5 658 85 2 0.5 583 0.5 648 65 3 0.5 593 0.5 638 45 4 1.0 573 1.0 658 85 5 0.25 573 0.25 658 85
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