定位格架是反应堆燃料组件中较为重要的部分，带搅混叶片的AFA-2G/3G定位格架具有良好的支撑燃料棒束和强化棒束通道换热的性能，但结构复杂，加工难度大。设计一种制造工艺相对简单的带有矩形涡旋发生器（longitudinal vortex generators，LVGs）的新型定位格架，研究当此种定位格架用于5×5的燃料棒束时的热工水力特性。主要采用标准k-ε湍流模型和增强型壁面函数处理方法，分析雷诺数和LVGs攻角对流体换热的影响。结果表明：由LVGs产生的二次流扩散到下游区域并对燃料棒的边界层产生扰动，增强换热；60°和45°攻角的矩形涡旋发生器（RLVGs）的换热效果几乎相同，但60°攻角RLVGs的阻力和压降较大。本研究对这种新型燃料组件的工程设计具有一定的参考价值。
Spacer grid is an important part of fuel assembly in reactor. The AFA-2G/3G spacer with mixing vane supports rod bundles well and enhances the heat transfer, but it has a complex structure and difficult processing. A novel spacer grid with the rectangular longitudinal vortex generators (RLVGs) is designed to improve thermal-hydraulic characteristics of fuel assembly. Based on the standard k-ε model with the enhanced wall treatment, a three-dimensional numerical simulation of the novel spacer grid in the channel of PWR fuel rods is presented. The effects of Reynolds number and attack angle are investigated. Numerical results show that the second flow generated by LVGs spreads to the downstream region of spacer grid and improves the heat transfer. The spacer grids with RLVGs with attack angles of 60° and 45° result in almost equal heat transfer performances. However, the spacer grid with RLVGs with attack angle of 60° brings about more pressure drop in comparison with that of the 45° case. The present research on new fuel assembly has certain potential value for the engineering design.
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