A new concept for squirrel-cage fan inlet

Abstract

The squirrel-cage fan with a newly introduced outward inlet lip is studied experimentally. Previous research has demonstrated the importance of inlet flow control on the general flow field and vortex generation of such fans. The bell-mouth inlet, which is the common industrial and academic practice, has drawbacks that result in flow separation and turbulence enhancement. The adapted experimental approach is a conceptual study. It is a combination of standard characteristic measurements and detailed laser Doppler anemometry. The measured flow pattern inside the volute demonstrates that the separated flow behind the inlet lip, which for an ordinary inward lip occupies a large part of the rotor blades, disappears. This is promising since removing this separated flow diminishes a major loss-making region in this fan and adds to the effective flow area. It also reduces noise and gives uniform blade loading. The results also show an improvement in performance in comparison with that of a fan with an ordinary inward inlet lip. This modification is industrially feasible with no extra manufacturing cost and therefore can represent a substantial advance over the current practice.