Performance Improvement of Centrifugal Fan by Using CFD

The flow in a centrifugal impeller is simulated firstly by solving the Navier-Stokes equations with the Spalart-Allmaras turbulence model and the performance curves are then obtained. Effect of the match between the inlet duct and the impeller inlet on the performance of the centrifugal fan is studied numerically. Based on the numerical analysis, the flow characteristics of a centrifugal fan including an inlet duct, an impeller, a diffuser and a volute are predicted. The impeller consists of twelve blades. The numerical results indicate that the leakage loss is produced by the circular flow occurring in the shroud outside. At the same time, the flow is found to have returned to the upstream of the volute. Because of the interaction between the impeller and the volute, the flow parameters along the circumference in the impeller outlet and the volute inlet are not uniform. Also, the flow in each impeller passage is different apparently. Compared with the impeller, the efficiency of the centrifugal fan drops by about 3–4%. According to the calculated results, the linkage profile between the inlet duct and the impeller inlet is redesigned. The linkage smoothness is favorable to performance improvement and a wider range of operation of the fan. Finally, the effects of the straight shroud with different inclined angles on the performance of the fan are studied. In a reasonable range of inclined angles, the performance of the fan is enhanced by selecting a straight shroud and the difficulties in manufacturing the fans are lessened.