That is for straight airflow.
What you have inside a ducted fan is a vortex.
Air molecules are like marbles. When you spin them
around they tend to congregate out near the walls
of the ducts. Nothing short of CFD is going to come
close to telling you what losses you will have.
As Matt says, build it and try it. Perry Mick worked
on his for 13 years as I recall. He now uses a gear box
and prop.
Paul Lamar ...No rotor no motor.
In the interest of accuracy, this is not really correct Paul.
It was 13 years from the start of building my Long-EZ until first flight
- which was with a ducted fan. But I did not work on the ducted fan for
13 years.
I worked on the airframe from 1986 to 1997. I bought the rotary engine
January 1997, had it installed and was doing taxi testing with the first
ducted fan by Summer 1998. First flight was July 1999 on the second
ducted fan.
So actual ground experiments with ducted fans only consumed about 1 year
before first flight. I experimented with a third ducted fan after it was
flying.
I flew it for 500 hours with the ducted fan, until December 2004. Top
cruise speed achieved was 135 knots, engine speed 5400 RPM. With the
same engine (the engine has not been removed from the plane since 2001)
with RD1B and 62/68 3-blade prop top cruise speed is now 160 knots,
engine speed 6400 RPM. I am getting more power out of the engine now
since I can turn it up higher. Flying at 5400 RPM now, I am back around
130 knots again.
Some of the drag of the duct can be offset if the duct has a dual use as
a horizontal/vertical stabilizer. See my LSA proposal at
http://www.bridgingworlds.com/LSA.htm
Perry
http://www.ductedfan.com
Even tho the speed is the same at 5400 RPM the power generated
is less. One needs to know the intake manifold pressure at a
given RPM to determine the HP consumed.
What is the intake manifold pressure now at 5400 RPM Perry?
--
Paul Lamar ...No rotor no motor.
I think this thread has ended, but you are right, it would be a
significant throttle reduction to 5400 RPM. I will have to see what the
manifold pressure is on the next flight, maybe tomorrow morning.
Perry
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