Air Flow Turbulent Fluctuations in a Centrifugal Fan

Abstract

In this work air flow turbulent fluctuations within the volute-impeller interaction region in a centrifugal fan are analyzed. The fan is part of one group of four similar units that provide the necessary air into a steam generator, in a power plant of 70 MW capacity. A numerical approach based on the finite volume method has been employed to solve the full set of Navier-Stokes equations in 3-D. Multiple reference frame was used to simulate the circular motion of the rotor inside the volute which remained static as well as the air entrance and exit sections. The whole domain was divided into 1.350 × 106 cells. Additional terms due to centrifugal and Coriolis forces were taken into account in the computation. The turbulence was addressed using one model based on renormalized group theory, RNG. Emphasis is focused on describing the velocity field within the annulus in between the rotor and the volute and its fluctuations. One first set of results indicate that the highest velocities appear in the region close to the blades tip, but they decay immediately after entering the annular volute-impeller region. Over there, the flow develops into two zones which are well defined through dynamic and static pressure contours. The results show how the magnitude of turbulence intensity varies according to different operation conditions of the fan, taking as fixed parameter the pressure at exit. The behavior of turbulence in the radial direction for a number of flow sections, starting from the cutter at the exit of the fan are examined as well.