摘要
采用多重参考系(Multi-reference frame,MRF)法处理桨叶旋转和以颗粒动力学为基础的Euler-Euler双流体模型,对下沉颗粒和上浮颗粒分别在双层涡轮桨搅拌槽内的固液悬浮特性进行数值模拟研究。得到搅拌槽内宏观流动场和下沉颗粒与上浮颗粒的固含率分布,并考察操作条件对两类颗粒悬浮特性的影响。数值模拟的液相速度分布和流型与文献试验结果吻合良好。研究结果表明,上浮颗粒与下沉颗粒的固液悬浮特性有很大的差别。下沉颗粒固含率分布总体上随轴向高度的增加而降低,固含率在槽底中心处最高,而在循环涡涡心、叶片和挡板的背流面则相对较低,上浮颗粒的固含率分布则与上述下沉颗粒分布趋势相反。搅拌转速增大使下沉颗粒固含率在循环涡涡心有下降趋势,而上浮颗粒固含率则有所增加。平均固含率降低或颗粒尺寸减小有利于两类颗粒均匀悬浮,平均固含率或粒径增大使下沉颗粒和上浮颗粒分别更易于在槽底和液面中心处聚集。
Solid-liquid suspension characteristics for sinking and floating particles in a dual-impeller stirred tank are simulated numerically by using computational fluid dynamics（CFD）.The multi-reference frame（MRF） method for treatment of impeller rotation and Euler-Euler two-fluid model based on the kinetics of granular are used in the simulation.Flow field and solid holdup distribution for sinking and floating particles in the agitated tank are predicted,and the effects of operating conditions on solid-liquid suspension are investigated.The numerical simulated liquid velocity distribution and flow pattern are good agreement with experimental data in literature.The simulated results indicated that solid-liquid suspension of sinking particles is quite different from that of floating particles.For sinking particles,solid holdup decreases along axial height as a whole,and the highest solid holdup is found in the centre of the bottom region.Local solid holdup in the centre of circulation loops,behind the blades and baffles was relatively low.Nevertheless,solid holdup distribution for floating particles is contrary to that of sinking particles as above-mentioned.The increase of impeller speed can cause local solid holdup in the centre of circulation loops decrease for sinking particle,while contrarily for floating particles.Decreasing solid content or smaller particles size is beneficial to the uniformity of solid-liquid suspension for the two types of particles.With increasing of particles content or particles size,sinking particles and floating particles are more prone to aggregate in the centre of bottom region and surface region,respectively.
出处
《机械工程学报》
EI
CAS
CSCD
北大核心
2014年第12期185-191,共7页
Journal of Mechanical Engineering
基金
西南科技大学博士研究基金资助项目(11zx7162)
关键词
下沉颗粒
上浮颗粒
固液悬浮
搅拌槽
两相流
数值模拟
sinking particles
floating particles
solid-liquid suspension
stirred tank
two-phase flow
numerical simulation
