Optimization of the deceleration ratio in impellers of centrifugal fans

The diffusion factor of Rodgers (1978) for impellers of centrifugal compressors, which is a modified version of the diffusion factor of Lieblein et al. (1953) for axial cascades with decelerating flow, is adapted for impellers of radial fans. The relation between the impeller efficiency and the diffusion factor is determined from numerical analysis of 31 impeller configurations. These are variants of the impellers of 2 built radial fans by varying the blade shape and the blade number. The numerical technique is validated by comparison with the measured performance of the two built fans. Recommendations on optimal values of the diffusion factor are formulated, with a similar limiting value DF=0.6 as for axial cascades.