具有双层桨结构的自吸式搅拌反应器的流体力学性能

在直径0.48 m的搅拌槽中以水?空气为介质，对具有双层桨结构的自吸式反应器的流体力学性能进行了实验研究，考察了自吸式桨浸没深度、底层桨结构和搅拌桨层间距对自吸式桨的临界吸气转速、吸气速率和气含率的影响。结果表明，临界吸气转速随自吸式桨浸没深度增加而增加，临界吸气转速几乎与下层桨的结构无关；吸气速率与气含率随浸没深度增加而减小，吸气速率与气含率受下层桨影响较大，层间距为自吸式桨直径(D)且采用上推式的四叶宽叶翼形轴流式桨作下层桨时，自吸式桨的吸气性能最佳。

Hydrodynamics performance of self-inducing stirred tank equipped with double impellers

Stirred tank equipped with a self-inducing impeller is a typical gas–liquid reactor which attracted much concern in recent years. In order to investigate the hydrodynamics characteristics of a four-blade self-inducing impeller and find the optimized impeller combination, experiments were conducted with the air?water system in a tank of 0.48 m diameter. The effects of impeller submergence, impeller spacing and the structure of bottom impeller on the critical impeller speeds of air inducing, gas holdup and gas-inducing rate were investigated. The results showed that the critical impeller speed increased with the increase in impeller submergence, while the critical impeller speed of different double impeller combinations were nearly the same. Although the bottom impeller had a little influence on the critical impeller speed, it obviously influenced global parameters such as the gas-inducing rate and the total gas holdup, which decreased as the impeller submergence increased. Under the same power consumption, when the bottom impeller was WHU (wide hydrofoil pumping up), a good gas-inducing rate and gas holdup were achieved. Impeller spacing also had influence on gas-inducing rate and gas holdup. When the impeller spacing was equal to a diameter of the self-inducing impeller, the latter showed the optimal performance on gas-inducing and gas holdup. The influence of impeller submergence and impeller rotation speed on gas-inducing rate, gas holdup and relative power demand (RPD) of gas-inducing impeller can be taken into account by introducing a modified Froude number to help the design of stirred tank.