A Critical Review of Stall Control Techniques in Industrial Fans

Figure 9

An axial flow fan fitted with an anti-stall ring. The anti-stall ring comprises an extension to the fan casing just over and upstream of the blades. The anti-stall casing incorporates static vanes, shown in yellow. As a fan approaches stall the flow though the fan is centrifuged up the blades and stalls as the flow spills out of the fan inlet. The blades redirect the flow in an axial direction, and reintroduce it upstream. This process of straightening and reintroducing the flow stabilises the fan’s performance, eliminating the drop in pressure developing capability classically associated with a fan operating in a stalled condition [72].