【摘要】 利用CFD技术对锥盘底搅拌槽内的固液两相流混合浓度场进行数值模拟研究,考察了45°圆盘涡轮式搅拌桨直径d对固液混合时间数,单位体积混合能,浓度标准差,湍动能和湍动耗散率,和固相离底悬浮临界转速的影响。研究表明:随着搅拌桨直径的增大,搅拌槽内的流体由轴向流转变为径向流的流型转变高度逐渐减小。桨径比d/D大于0.3时,混合时间数显著减小;d/D小于0.4时,单位体积混合能较小;d/D达到1/3时,单位体积混合能最小。浓度标准差随搅拌桨直径的变化波动较小。d/D小于0.4时,湍动耗散率的增长率较低;d/D大于0.3时,固相离底悬浮临界转速显著减小。从提高混合效率和降低能耗的综合角度考虑,桨径比d/D应控制在0.3—0.4之间。更多还原

【Abstract】 Numerical simulation of concentration field of solid-liquid two-phase flow in stirring tank was carried out with CFD.The influence of 45° disc turbine impeller diameter on mixing time,mixing energy per unit volume,concentration standard deviation,turbulent kinetic energy and turbulent dissipation rate,solid and liquid critical off-bottom suspension speed was analyzed.The result show that with the increasing of paddle diameter,the inversion height of flow changed from axial flow to radial flow in stirred tank decreases.When d/D is more than 0.3,mixing time decreases obviously.When d/D is less than 0.4,the mixing energy per unit volume is small.When d/D reaches 1/3,the mixing energy per unit volume is the smallest.The standard deviation of the concentration fluctuates changed less with the stirring diameter.When d/D is less than 0.4,the growth rate of turbulent dissipation rate is low.Critical suspension speed of solid phase is significantly reduced as d/D is more than 0.3.So the ratio d/D should be controlled between 0.3 and 0.4 in order to improve the mixing efficiency and reduce the energy consumption.更多还原