| The centrifugal fan, which has been widely used in various industries, agriculture, is one kind of the fluid machinery. When centrifugal fans working, particles will inevitably rub, impact, rebound, abrase with and accumulate at the centrifugal fans, these actions are harmful to balance of impellers and reduce using-time of the mechanism. At present, the numerical simulation is a major measure in the centrifugal fans field. In this paper, I have finished this work by numerical of gas flow field and gas-solid two phases flow field in centrifugal fans.First in this paper, making use of the centrifugal fans'trim size constituted mathematics model in the software PRO/E. The centrifugal fans was meshed in the software GAMBIT. The unstructured grid with small dimension is selected in the regions where the flow is complex, on the other hand the structured grid with large dimension is selected in the inlet and the worm shell. The three-dimensional time averaged N-S equation, the K-E turbulent model are based and the SIMPLE arithmetic are used. The moving reference frame is used in the impeller region and the boundary are velocity inlet and pressure outlet. And have a gas numerical simulation, When the computation converged, the discrete phase injection is set in the inlet of the simulation model, then the Lagrange particle track model and the uniphase copping method are used to simulate the gas-solid two phase flow field in the centrifugal fan. Some flow phenomena are captured in simulation of gas flow, for example the separation of the boundary layer, the secondary flow and the gap flow, and the particles with different diameters 0.03mm,0.05mm,0.1mm in the centrifugal fan are obtained in the simulation of gas-solid flow too.The result of simulation shows that the solid particles are divided into two airflows when entering impeller and the way of the blades where is a 90°swerve. the big particles can concussion the back tray of impeller and then course along the back tray. The small particles are flowed by the airflow, and which are separated from the big particles flow. In this paper some new results are found, when the particles enter the impeller, the flow way are not pumping the particles any more.the particles can bounce, rebound, glide or tumble on the working blades. The big particles will course on the working blades.the small particles will course on the un-working blades and even adhere to it where the small particles aggradate on. The aggradations area will be bigger and bigger, at last the un-working blades will be bestrewed entirely. But there will be small eddy in the impeller, small particles will course with the airflow contrarily. So the un-working blades will get glide abrasion, and as a result of the big particles'inertial concussion, the working blades will get erosion abrasion.The results of simulation are coincident with the experiment, it shows that the method of simulation deleloped in this article is reliable and can be used to guide the optimum design of the centrifugal fan.
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