EFFECT OF MODE OF ROTATION AND SPEED ON THE PRESSURE FIELD AND AXIAL THRUST OF INDUSTRIAL CENTRIFUGAL FAN

Abstract

Centrifugal fans are used widely in most of the manufacturing processes for ventilating and/or air conditioning the working areas. Because of relatively limited documentation on the design of this type of fans, experimental and theoretical works are investigated in this paper for forward backward centrifugal fan to calculate the average dynamic pressure and axial thrust forces at different speed conditions. The flow in centrifugal fan is highly complex with taking place on the impeller .The centrifugal fan simulated using computational fluid dynamic (CFD) approach. Flow in centrifugal fan with duct is simulated by Navier – Stokes equation and performance curved are obtained. Most of companies creates in 3D model in Solid works version 2013 and the conduct analyses by the CFD programs. At first step , an experimental step was developed and prototypes of impeller was made to carry out at the south Baghdad power plant for the sake of flow measurements and next , computational fluid dynamics model was developed for the above step and the result are validated with experimental measurement. Fine mesh is generated for centrifugal fan with duct in GAMBIT programs to carry out analyses for whole computational domain in fluent programs. Further parametric studies were carried out to calculate the average dynamic pressure when rotating the impeller backward and forward rotation modes. The parameter considered in this study are changing in dimension of outlet duct at different speeds. Finally, the result shows Increasing the speed of motor caused increasing in the average dynamic pressure is (98.43% (at outlet and on the blade of the impellers .The average of dynamic pressure for forward rotation mode is (61.83%) greater than that of backward direction mode .The results exhibited that the maximum discrepancy between the experimental and numerical is (9.8%) for backward rotating and (10.44%) for forward direction at different speed. The magnitude of dynamic axial thrust forces in the z – direction are maximum for forward rotation mode compared with another rotation mode because the differences in pressure on the impeller fan. The experimental and theoretical results are in well agreement, with the (CFD) model developing .Benefit from the results of this research in the influence guess bearings on the vibration characteristics of the system