Abstract: The flow characteristics of a typical pseudoplastic fluid, xanthan gum solution, stirred by three different types of impeller in vessels were investigated. FLUENT? software, combined with standard k-e turbulent equations and multiple reference frame method, was employed to solve the problems numerically. The flow pattern, cavern volume, viscosity distribution, and power consumption of various concentrations of xanthan solution were obtained. Concentration of xanthan solution ranged from 0 to 2.0%(w), and impeller rotation speeds were 5 and 7.5 r/s, respectively. A remarkable effect of shear thinning was observed near the installation position, and there were significant differences of the distribution of liquid viscosity for each impeller. The impeller efficiency declined drastically with xanthan concentration, and increase of impeller speed barely improved impeller efficiency. When the xanthan concentration increased, power consumption generated by different flow patterns showed adverse results. When xanthan concentration was 2.0%(w) and rotation speed 7.5 r/s, the cavern volumes of all the operations were less than 60% of total vessel volume. Power consumption in the vessel with a Rushton turbine was dropped by 7%, while increased by about 29% with a Pitched blade turbine.

Key words: multiple reference frame, xanthan gum, flow pattern, viscosity, power consumption

摘要： 使用FLUENTa软件对黄原胶溶液在搅拌槽内的流动特征、桨叶搅拌效果和功率消耗进行了数值模拟. 计算采用多重参考系方法和标准k-e湍流方程. 黄原胶浓度为0~2.0%(w)，桨型为直叶圆盘涡轮、非对称抛物线圆盘涡轮和四斜叶桨. 结果表明，不同桨型下溶液的粘度分布有较大差异，且搅拌效率随溶液浓度增加急剧下降，转速增加能有限提高搅拌效率. 径流桨和轴流桨产生的功率消耗随溶液浓度改变呈相反的变化趋势. 在黄原胶浓度2.0%(w)、搅拌转速7.5 r/s时，所有桨型下有效搅拌体积所占比例均低于60%；与在水中相比，直叶圆盘涡轮的功率消耗降低约7%，而四斜叶桨的功率消耗增加29%.

关键词: 多重参考系, 黄原胶, 流型, 粘度, 功率消耗