摘要
在子通道雷诺数为6600、13200、26400和39600下,使用粒子成像测速仪对5×5棒束分流型交混翼定位格架下游横向和纵向流动进行测量。平均速度和湍流脉动速度均方根的实验结果最大不确定度低于1%的主流平均速度。格架下游二次流结构经历了交混翼脱落涡结构耗散、剪切产生双涡结构、双涡结构向单涡结构的转变及单涡结构沿程衰减过程,横向平均速度和湍流脉动速度均方根沿程变化均受涡结构演进影响。格架近场湍流统计量迅速衰减;格架远场湍流统计量缓慢衰减,流动趋于光棒束充分发展流动。横向流动受雷诺数效应和格架交混效应共同影响。
The single-phase sub-channel mixing mechanisms in rod bundle include diversion cross-flow mixing and turbulent mixing.The split-type mixing-vaned spacer grid strongly enhances cross-flow mixing and turbulent mixing,resulting in lower peak temperature on rod-bundle surface and higher critical heat flux.Thus,the split-type mixing-vaned spacer grid is an important device in fuel assembly for pressurized water reactor(PWR).However,the enhancement mechanism of spacer grid is still not clear.And clear enhancement mechanism of spacer grid mixing effect on sub-channel mixing is the basement for mechanical sub-channel mixing models.To study the spacer grid mixing effect,the cross-flow and longitudinal flow downstream a split-type mixing-vaned spacer grid in a 5×5 rod bundle was measured by particle image velocimetry(PIV),with sub-channel Reynolds number(Re)from 6600 to 39600.The rod bundle was fabricated with diameter 9.5 mm,pitch 12.6 mm and sub-channel hydraulic diameter 11.78 mm.The maximum standard uncertainty of statistical quantities of turbulence normalized by the bulk velocity is less than 1%.The secondary flow structure downstream of the spacer grid is dominated by the vortex shedding from mixing vanes near spacer grid within 3D_(h),and then the cross-flow develops and builds up after the dissipation of shedding vortices.The strong shear flow generates co-rotating vortices in each sub-channel.With flow development downstream of the spacer grid,the two vortices expand,weaken and become close to each other,and they merge into single vortex covering the whole sub-channel.Then the single vortex decays slowly.The vortex structure pattern coversion impacts on the lateral mean velocity and root mean square fluctuating velocity.Thus,the vortex pattern determines the sub-channel mixing,including the diversion cross-flow mixing and turbulent mixing.Near the space grid,lateral turbulent intensity is strong in the shedding vortices and decays fast with the dissipation of shedding vortices.With double-vortices generation by
作者
曲文海
陈仕龙
黄慧剑
熊进标
QU Wenhai;CHEN Shilong;HUANG Huijian;XIONG Jinbiao(School of Nuclear Science and Engineering,Shanghai Jiao Tong University,Shanghai 200240,China;Science and Technology on Reactor System Design Technology Laboratory,Nuclear Power Institute of China,Chengdu 610213,China)
出处
《原子能科学技术》
EI
CAS
CSCD
北大核心
2022年第6期1129-1137,共9页
Atomic Energy Science and Technology
基金
国家重点研发计划政府间国际科技创新合作重点专项(2018YFE0116100)
国家重点研发计划(2017YFC0307800-05)。
关键词
定位格架
子通道交混
折射率补偿
粒子成像测速仪
spacer grid
sub-channel mixing
matched index of refraction
particle image velocimetry
