Comparative Performance Evaluation of a Multistage Axial Fan Assembly

Small fans which are primarily axial machines induce the air movement of a relatively large mass flow within comparatively low velocities for reasons of thermal management. In the present investigation six axial fans of the same type were assessed for their structural (inactivity), geometrical and dynamic similarity. The results indicated that the fans including the stators and the rotors were operationally and dynamically similar. A series of experiments was conducted for a single stage, 2-stage and 3-stage fan configurations. The experimental data were used for the derivation of a linear algebraic model, as well as for calibrating a stage stacking model developed by Cranfield University for predicting the overall performance of multi-stage axial flow machines. The comparison between the computed values and the experimental data indicated very good agreement in the entire range of speed lines. The algebraic model can be used with high confidence for predicting the fan performance for rotational speeds where experimental data are not available. The validated stage stacking model can be used for predicting the performance of multi-stage lowvelocity axial fans when experimental data are only available for a single stage