激光诱导荧光技术对棒束通道内定位格架搅浑特性研究

基于激光诱导荧光（LIF）技术开展了5×5棒束通道内定位格架搅浑特性的可视化研究。常温常压下，通过示踪染色剂（RhB）浓度分布表征流体微团的搅浑行为，清晰展现染色剂溶液在定位格架作用下的搅浑扩散过程，获取格架下游流场的搅浑信息。采用自验证方法分析验证LIF技术测量的准确性，重构棒束通道内径向与轴向染色剂浓度分布，对比带定位格架与不带定位格架的实验结果，得到定位格架对其下游流场的影响范围及不同棒束子通道所受搅浑程度的差异，并以变异系数量化格架对流场搅浑性能的强弱。实验结果表明：定位格架能快速搅浑流动工质，其搅浑翼片分布形式的差异是造成不同子通道交叉搅浑强弱及各向异性的主要原因。本实验工况（Re＝10 478）下，格架对其下游流场的作用范围约为8倍当量直径(D_h)，流动工质在格架下游5D_h附近所受搅浑最为剧烈。

Mixing Characteristic of Spacer grid in Rod Bundle Channel by Laser Induced Fluorescence Technique

In order to study the effects of spacer grids on 5×5 rod bundles channel, laser induced fluorescence (LIF) technique was applied. The transverse exchange of the spacer grid on the flow field was obtained indirectly by the internal concentration distribution of the dye tracer (RhB) under normal temperature and pressure. The blending diffusion process of the dye tracer can be intuitively observed. The self-verification method was applied in order to check the accuracy of LIF technique measurement. By reconstructing the concentration of the dye tracer at different locations in the radial and axial positions of the rod bundle channel and comparing experimental results with spacer grid or not, the range of the influence of the spacer grid on the flow field was observed. The coefficient of variation (COV) was also applied to quantify the mixing intensity of the spacer grid. The results show that spacer grid can mix the flow quickly and the difference of the mixing vanes is the main reason cause of the cross-mixing strength and anisotropy. Under the Reynolds number is 10 478, the effect on the down-steam flow field is about 8 equivalent diameters (D_h) and the strongest mixing ability is at 5D_h downstream of the spacer grid.