Improvement Of Structure And Analysis Of Flow Field In Turbo Air Classifier

Turbo air classifier is the most important device in the powder classification and isused widely. With the development of powder engineering technology, there are morestrict requirements with powder classification, that is, the classification precision must beimproved and cut size of classified particles should become smaller on condition that theoutput must be achieved. Flow field characteristic in the turbo classifier is one of the mostimportant factors of classification performance. In this study, the structure of the turbo airclassifier was improved, and the numerical simulation of3D flow field of annulus regionand rotor cage was performed by Fluent software. The flow field characteristics wereanalyzed in order to provide basis for improving performance of the turbo air classifier.The content of the dissertation is summarized as follows:(1)0、2、4、6、8、12parallel vertical stems are installed symmetrically on the peripheryof rotor cage in turbo air classifier. The effect of parallel vertical stems on turbulentdissipation rate and3D flow field characteristics were analyzed in annulus region. Theresults show that the turbulent dissipation rate can be increased and the dispersing powercan be improved in the turbo air classifiers if2parallel vertical stems are installed.Compared with the classifiers with the other numbers of parallel vertical stems, the cutsize of classified particles becomes smaller and classification precision can be improved inthe classifier with2parallel vertical stems. The result of flow field simulation is in goodagreement with that of the material experiment.(2) Short blades are installed between the blades in rotor cage. Six turbo air classifiermodels are established, in which the length of short blades are0mm,5mm,10mm,15mm,20mm,25mm, respectively. Flow simulation was carried out at an air inlet velocity of12m/s,16m/s and20m/s, respectively. The result shows that short blades can weak theinertia counter-vortex, and make the flow field more uniform in the rotor cage. As a result,the classification precision can be improved. With the increase of the inlet air velocity, thelength of the short blades should be increased in order to make the flow filed more even. (3) The influence of the blade angle of rotor cage and the angle of guide vanes on theflow field characteristics was investigated synthetically in the turbo air classifier. Therewere25kinds of orthogonal simulation models including5levels of guide vane anglesand5levels of blade angles in rotor cage. The result of numerical simulation indicates thatthe dispersing power can be improved in the turbo air classifiers and the distribution offlow field is more stable when the angle of blade curved backward in rotor cage is40°and the included angle between the guide vanes and the basic circle of guide vanes is20°.It can found that the classification precision can be increased and cut size can be decreasedin this air classifier.