Study Of Structure And Flow Field Characteristics In A Turbo Air Classifier

The turbo air classifier is very important dry-state classification equipment. By using Laser Doppler Velocimeter (LDV) the flow field characteristics of the annular region and the rotor in a turbo air classifier is measured. Classification experiment of raw materials is carried out to test the effect of the structure of classifier rotor and classifier volute on classification performance. This result should increase the depth of understanding of optimizing the structure of the turbo air classifier.Velocity measurement of air flow in the classification region of the rotor in a turbo air classifier is performed by Laser Doppler Velocimeter (LDV). The results indicated that the tangential velocity of air flow is not agreement with tangential velocity of the rotary rotor blade. In the low rotary speeds of the rotor the tangential velocity of air flow decreases with the decreasing radius of the measurement point; in the high rotary speeds of the rotor the tangential velocity of air flow increases with the decreasing radius of the measurement point. Vortex is present in the revolving flow field, and position of vortex is in relation to the rotary speeds of the rotor. The axial velocity is in evidence because of the rotation of the rotor and the present of negative pressure. The axial velocity distribution is not uniform in the classification region of rotor blades and the value is in relation to the inlet air velocity and the rotary speed of the rotor. The effect of rotary speed on the flow field characteristics of the annular region was studied. The influence coefficient of rotary speed on the flow field characteristics of the annular region is defined as F. F decrease with the increase of rotary speed.The results indicate that the axial velocity of the annular region is decreased and flow field is optimized when horizontal boards are installed in the classifier volute. Horizontal boards are installed in the blades so that the axial velocity decreases in a certain extent. Experiments of the material classification are carried out. The results show that as low rotary speeds are employed the annular region is considered as the main classification region, and in high rotary speeds the annular region works as the function of dispersion and secondary classification.