wrote:
On May 6, 2:00Â*pm, wrote:
Jim Logajan wrote:
wrote:
True that propeller research went away around WWII, but wind turbine
research is currently a hot topic and that's what the propeller
becomes when the engine stops.

True, but if the propeller airfoil has asymmetrical camber then when the
engine stops, the relative wind is inverted (coming from the wrong side -
similar to inverted flight.) So it wouldn't be terribly efficient and
attributes like prop stall angle differ from engine on versus engine off.

When the engine stops producing power, it becomes a frictional load to
the prop, which becomes a wind turbine.

There is nothing about the prop being attached to an airplane that
invalidates analysis as a wind turbine under that condition.

Whether it is an efficient wind turbine or not is irrelevant, it is
still a wind turbine when the engine is not producing power and air
is flowing past it.

--
Jim Pennino

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Yeah,, but. If the prop is not efficient enough to even rotate with
the wind passing over it it never really becomes a wind turbine....
Those need to spin to be called that. A non rotating prop is called ..
DRAG . A rotating prop not under power is called more DRAG.. IMHO

Ben.

And if the prop is in the special case of being motionless, it is just
an area equal to the frontal area of the prop.

There are three cases:

1. engine producing power and the prop spinning; prop has thrust X

2. engine not producing power and the prop spinning; prop has drag Y

3. engine not producing power and the prop stopped; prop has drag Z

Each is a different set of conditions and different net result.


--
Jim Pennino

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