An LDA study of the turbulent flow field in a baffled vessel generated by a PTD and PTU

摘要

The flow fields in fully baffled, cylindrical vessels of 250 and 360 mm diameter respectively, with a series of downflow pitched turbines (PTD) and upflow pitched turbines (PTU) have been measured using the two-component LDA. The flow fields of the PTD and PTU are substantially more complex than the conventional patterns reported previously. instead of a single circulation loop, present results show that a primary circulation loop doesn't reach the bottom of the tank for an impeller clearance of the T/2, but it is accompanied by a secondary circulation loop. However, when the diameter of the impeller decrease from T/2 to T/3, the secondary circulation loop disappear. The distribution of axial pumping capacity is also provided.