中文摘要：

研究燃料组件定位格架及棒束通道的流动特征对组件结构设计有重要意义．为此，以5×5燃料组件的全结构定位格架为研究对象，建立组件的三维几何模型及非结构化网格，并采用CFD程序对棒束通道的流动特征与燃料棒的传热特征进行仿真，研究定位格架上搅混翼、刚突、弹簧和条带对组件流场的影响．研究表明定位格架对燃料组件的流动搅混和传热有明显的增强，搅混翼对流场的扰动最显著，其下游的横流主要沿翼片伸张方向发展，扰流长度为格架高度的10倍以上；刚突和弹簧只在其结构部位产生局部横流，刚突的横流以自条带向凸沿发展，单弹簧结构的横流沿弹簧的弯曲方向，双弹簧结构只在与条带连接处有微弱横流．

英文摘要：

The flow characteristics of spacer grid and rod bundle channels play an important role in the frame design of fuel assembly. In this paper, one unabridged spacer grid of a 5 - 5 fuel assembly is investigated. Its 3 D geometry and unstructured grids are established, and a CFD code is adopted to simulate the flow characteristics of rod bundle channels and the heat transfer characteristics of the fuel rod. Then, the effects of mixing vane, dimple, spring and band on the flow field of the fuel assembly are analyzed. The results show that （ 1 ） the spacer grid can significantly enhance the flowing mixture and the heat transfer in the fuel assembly; （2） the mixing vane has the most signifi- cant effect on the flow field, and the downstream lateral flow of the mixing vane forms along the vane stretch direc- tion with a lateral flow length of more than 9 times greater than the grid length ; and （3） the dimple and the string cause the lateral flow to form only near their location; specifically, the lateral flow of the dimple extends from the band to the dimple front, the lateral flow of the single spring runs along its bending direction, and as for the dual spring, there exists a weak lateral flow in its joint part with the band.