An experimental study of leaning blades on the half-cone rotor of a squirrel cage fan

This article presents an improvement for the blade configuration of a squirrel cage fan. Numerical simulations have shown that a -2 degrees lean angle applied to a half-cone rotor of +10 degrees produces a higher efficiency. This is expected to be a result of blade alignment with the inlet stream. Performance curves in this article compare this new rotor with both a simple half cone of the same cone angle and a corresponding cylindrical rotor. The half-cone rotor with leaning blades had improved head coefficient and efficiency in the normal operating range, which is to the right of maximum head or efficiency points. The simple half-cone rotor had almost constant efficiency for all flow ranges, which is a very demanding feature for any fan. A study of velocity profiles inside the volute showed that maximum flow exited the rotor close to the cut-off. A leaning blade had negligible effect on radial and tangential components at this location but it changed the axial component. This was due to a movement of the vortex behind the inlet and a larger active region of the rotor blades.