Chris S. Mottram@ECCI
07/01/99 12:00 PM
As far as automotive application is concerned, the question must be "will a
fans of equal diameter, and speed but different number of blades (with
optimum or possibly differing pitch and surface area?) produce more or less
air movement across the radiator?
It looks like the science guy quoted below is comparing the energy required
to spin the fan vs.the air moved. I think both my Tiger and Alpine have
enough extra HP to spin the fan. It is very interesting though. I am
going home tonight to dig out my old LAT single bladed cooling fan ;-)
Chris
Jay Wrote:
A: The more blades a fan has, the less efficient it becomes because each
blade is moving in the turbulent wake of the blade preceding it. But a fan
with fewer blades has to turn faster to move the same amount of air, so it
will have a higher tip speed and thus be noisier. The same principles
apply to airplane and ship propellers. The optimum efficiency is achieved
with a single blade attached to a suitable counterweight, and some planes
have actually flown with such a design. The primary reason for multiple
blades is to reduce the diameter and the noise."
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