Effects of cut volute profile on squirrel cage fan performance and flow field

The flow pattern in the volute of a squirrel cage fan is complicated and non-axisymmetric. In this article, the original volute profile of a squirrel cage fan was cut to control and reshape this non-axisymmetric flow structure. An experimental study was conducted to investigate the effects of the cut volute profile on the fan aerodynamic and acoustic performance. The results showed that cutting the volute profile with a relative cut position of 90 degrees and a secondary clearance of 0.02D(2) could enhance the fan total pressure at the volume flow rate of 0.4Q(BEP) by about 7% without affecting the noise level. High-precision steady computational fluid dynamics simulation was also carried out to reveal the flow mechanism of the performance improvement. The results indicated that cut volute profile caused an impeller-across flow structure in the vicinity of the second clearance and re-organized the circumference distribution of the impeller flow status. Both the impeller working capability and the overall flow losses of the cut fan increased compared to the original one but the increment of the former was greater. This explains why fan pressure improved under low-flow conditions.