Aerodynamics
The characteristic external feature of cross-flow fans is
the impeller cylinder, which is often very long in a ratio
with the diameter.
These fans differ aerodynamically from all other types of
fan in that air flows through the impeller crosswise from
outside in radial planes. Pressure is applied twice to the
blade row with the cross-flow, and the flow is diverted inside
the impeller in a curve around an eccentric centre. This characteristic
cross-flow is independent of external control systems, it
occurs therefore without baffle plates as well.
The only task of external control systems is to support this
natural cross-flow above all in throttled operating conditions
and to separate the incoming and outgoing flows from one another.
The normal flow of a cross-flow fan is dependent roughly on
a 90° deflection.
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