摘要
利用kε湍流模型模拟了斜四叶涡轮搅拌槽内不同条件下宏观流动场, 研究了搅拌桨与搅拌槽直径比( D/ DT) 、桨叶离槽底距离(C) 对搅拌槽内宏观流动场的影响。数值模拟结果表明, 桨叶离槽底距离与槽径之比较小( C/ DT=0-33)时, 叶轮区域轴向流动较强, 在整个rz 断面形成一个整体循环。随着桨叶离槽底距离增加, 叶轮区径向流动增强, 当C/ DT= 0-5 时, 在搅拌桨下方区域形成二次循环区。搅拌桨与搅拌槽直径比较小时( D/DT= 0-33) , 挡板前后宏观流动场差别很大, 在挡板后面区域, 流体在桨叶安装位置高度附近转向轴心流动, 槽体上半部区域形成二次循环区域, 且二次循环区域内流体以向上流动为主。
The standard k ε model has been employed to predict the turbulent flow generated by pitched blade turbines in a cylindrical baffled vessel. The effect of D/D T and C/D T on the three dimension flow in the stirred tank has been studied as well. The model prediction shows that the mean circulation loop for low impeller off bottom clearance is a single circulation loop. As the off bottom clearance is increased, the radial flow is enforced, and a secondary circulation loop forms close to the tank bottom when the impeller clearance is increased to D T/2. The simulation results also show that the flow in front of the baffles is different from the flow behind the baffles for D/D T=0 33. In front of the baffles, only one circulation loop has formed, and the flow pattern is approximately the same. Behind the baffles, a small second recirculation loop has formed in the upper part of the vessel, and is directed upwards rather than downwards.
出处
《北京化工大学学报(自然科学版)》
CAS
CSCD
1999年第4期1-4,共4页
Journal of Beijing University of Chemical Technology(Natural Science Edition)
基金
国家自然科学基金