Mixing Performance Of Coaxial Impellers

Coaxial Rushton Turbine-Four Pitched Blade Turbine(RT-PBT)and coaxial inner-outer helical ribbon were designed in this essay and their mixing performance,including power consumption,mixing time and flow pattern.The research results shows that power consumption of coaxial RT-PBT impeller is the plus of RT and PBT single rotation power consumption.RN plays an important role to impeller's power consumption.When PBT in rotates down flow situation,its power consumption increases from 26%at speed ratio RN=1 to 95.4%at speed ratio RN=4.When it comes to up flow situation,the ratio increase from 23.8%to 94.5%.While RN=10,the figure is up to 99%in these two situation.When input same power consumption,mixing time decreased as RN increasing.Mixing time decreased 14.3%when RN increased from 1 to 3.This figure is 17.8 when RN increased from 1 to 10.The same law was found in up flows and the mixing time decreased respectively 13.9 and 21.5%.As for flow pattern,the increase of either impeller can decrease the low speed zone between two impellers or on the bottom of the stirred tank.For coaxial inner-outer helical ribbon,power consumption of inner helical ribbon and outer helical ribbon are lower than rotating themselves in co-rotating situation.Power consumption of outer helical ribbon is lower than its single rotating and for inner helical ribbon it decrease little in counter rotating situation.Speed ratio has a significant influence to power consumption.The percentage of inner helical ribbon's power consumption to coaxial impeller increased from 6.4%to 91%and these figures are 9.5%and 83%at counter rotating situation.The mixing time of co-rotating situation is short than counter-rotating situation.Observation flow pattern shows that co-rotating has a virtuous cycle performance than counter rotation situation.