100
3 Fans
3.1.5 Small Axial Fans
Stator vanes are mostly omitted with small axial fans. The flow then contains postswirl impairing the efficiency. The rotor is commonly mounted onto the driving motor, often with the motor in the hub. The rotor is mostly manufactured from mould
injected plastic Design examples are discussed in Sect. 3.7.
3.1.6 Cross-Flow Fans
Small power applications, such as generating an air flow with a small pressure
rise, may, apart from axial fans and radial fans with forward curved blades, feature
fans of a third type. Figure 3.4 shows a cross section of a so-called cross-flow fan.
Air passes through the rotor twice. The stator shape determines the suction and
Fig. 3.3 Two-stage axial fan;
flow from left to right; normal build is struts with axial
inflow and outflow, followed
by two stages rotor-stator
u
u
1
v
1
w
1
'
w
1
'
v
'
u
2
'
v
'
u
2
'
w
2
v
2
w
Fig. 3.4 Cross-flow fan