声场作用下超细颗粒在气-固流化床中的流体力学研究  

Fluid Dynamics of Ultrafine Particles in a Gas-Solid Fluidized Bed Coupling with Acoustic Field

作　　者：杨慧[1] 曹长青[1] 

机构地区：[1]青岛科技大学化工学院,山东青岛266042

出　　处：《化学反应工程与工艺》2013年第4期338-343,共6页Chemical Reaction Engineering and Technology

基　　金：国家自然科学基金(20876082)

摘　　要：在内径0.16m,高1.8m的气固流化床中,以空气和超细SiO_2颗粒为气相和固相,采用声场模型与计算流体力学软件Fluent 6.2中传统动量模型耦合,系统研究了声场对瞬时颗粒浓度分布场的影响规律、声能在不同流型和不同轴向位置的变化规律、声压级对最小流化速度和颗粒温度等流场的影响。研究结果显示,鼓泡床密相区径向颗粒浓度呈抛物线分布,声场的加入增大了轴向颗粒浓度,减小气泡尺寸;随着表观气速增加,声能增加非常明显,表观气速0.05 m/s为流型从固定床到流化床的过渡点。声能在床层中部区域较大,在床层底部和顶部较小。粒径增大最小流化速度随颗粒明显增加;当颗粒粒径一定时,随着声压级增大,最小流化速度增加,但增加的不是很明显;颗粒温度随声压级的增大而增大,表明气泡聚并和破碎的频率增大。A gas-solid acoustic fluidized bed, which is 0.16 m in diameter and 1.8 m in height, was employed to investigate systematically the effects of sound assistance on the instantaneous particle concentration profile, the variation of sound energy in different flow regimes and axial positions, the effect of sound pressure level （SPL） on the minimum fluidization velocity （Umf） and granular temperature with air as gas phase and ultrafine SiO2 particles as solid phases. The developed model concerning the sound assistance was coupled with conventional momentum equation in computational fluid dynamics software Fluent 6.2 to simulate hydrodynamics. The research results showed that the instantaneous particle concentration distribution in the dense phase region was a parabolic profile. The axial particle concentration was increased and the bubble size was decreased as the sound assistance was introduced into the fluidized bed. The sound energy increased significantly as the gas velocity increased. The threshold point of the gas velocity 0.05 m/s indicated the transition of flow regime from the fixed bed to fluidized bed. The sound energy at the middle region of bed was larger than that at top and bottom regions. Umf increased significantly with increasing particle diameter. The granular temperature increased with increasing sound pressure level, which showed that the frequency of bubble coalescence and breakup are increased.

关 键 词：气固流化床 声场 最小流化速度 流型 超细颗粒 流体动力学 

分 类 号：TQ028.2[化学工程]