Perry Mick wrote:

Here is a cross-sectional view of duct6. Straighter walls both inside
and out. Longer exit by a factor of two. Current duct2 has a chord of 2
feet, inlet 1 foot, exit 1 foot. This would have inlet 1 foot, exit 2
feet. Inlet size reduced, hoping that using slots all around the inlet
near the fan, will draw in extra air static/low speed but be largely
bypassed in cruise. Like your "blow-in doors" with no moving parts.

Perry

That looks good Perry. Looks like less external drag due to the
coning effect.

You might need spring loaded doors on  those slots as 
pressure in the duct at cruise could be higher than pressure
outside the duct. A few static pressure taps would confirm
that on your current duct.

The slots will feed more air to the fan at static forward speeds
no doubt but will generate no low pressure thrust as would be the case
with a large radius inflatable lip. That is not the same as saying
slots will not increase static thrust. I just think you would
get better results with an inflatable lip. On the other hand if
takeoff distances are almost good enough slots are simpler.

It would be nice if you put some pito tubes back there in your current
duct and measured a few velocities of the air going in and out. 
Then you could make a determination of the best combination of 
blade width and pitch.

Paul Lamar
 
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