板式螺旋桨搅拌槽内的流场及其流动特性

以板式螺旋桨叶轮为例,采用相位多普勒粒子分析仪测量了直径为300 mm的平底圆筒搅拌槽内的流场;分析了时均速度、脉动速度及湍流动能的分布,以及叶轮离底间隙变化和挡板对流场的影响。结果表明:随离底间隙增大,叶轮区脉动速度和湍流动能增大,时均速度和脉动速度最大值位置向槽中心方向移动;主循环区轴向速度最大值随离底间隙增大而减小;叶轮区湍流动能较高,随离底间隙增大,湍流动能最大值增大,位置靠近叶轮端部;挡板阻碍槽内切向流动,影响湍流动能的分布,挡板前流场反映了叶轮区的湍流动能分布。

Flow field and its flowability in a stirred tank with a plate propeller

The flow field produced by a plate propeller in a fully baffled flat bottomed cylindrical stirred tank with the diameter of 300 mm was measured using phase doppler particle analyzer.The radial distributions of the time-averaged,fluctuation velocity and turbulent kinetic energy were analyzed.The effects of off-bottom clearance and baffle on the flow field were investigated.The results showed that the fluctuation velocity and turbulent kinetic energy increased with increasing off-bottom clearance in the impeller region;meanwhile,the maximum values of the time-averaged and fluctuation velocity moved to the center of the stirred tank.The maximum axial velocity decreased with increasing off-bottom clearance in the bulk flow.The turbulent kinetic energy was higher in the impeller region.The maximum value of the turbulent kinetic energy increased with increasing off-bottom clearance and occured near the end of the impeller.The baffle hindered the tangential velocity and exerted strong influence on the turbulent kinetic energy.The flow field in front of the baffle reflected the distribution of the turbulent kinetic energy in the impeller region.