George, For the bell
shaped duct, what I have read in K & W it appears they say the inlet
area should be between 0.25 – 0.40 of the core area. The more slowing of
the air velocity that needs to be done by the diffuser before the core that is
needed appears to call for lower area ratio values of Ai/Ab (area inlet/area
core). In the example plotted of an streamline duct in K&W the chart
shows the area ratio was 0.40.
From:
Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net] On
Behalf Of George Lendich
Sent: Wednesday, January 20, 2010 6:16
PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Wedge/Oblique
Duct
If Ai is .33 Ab and .44 Ab for the
wedge ducts, what's it for the bell shaped duct - is there any similar
drawing?
----- Original Message -----
Sent:
Wednesday, January 20, 2010 3:39 AM
Subject:
[FlyRotary] Wedge/Oblique Duct
George, here are two figures
from K&W – one could be described as a “Wedge” figure 12-6 and the other
one a “streamline” wedge figure 12-12.
Always dangerous for me to
try to interpret what K&W are really saying, but from what I get from
these two figures, it would appear that the “streamline” wedge permits you
to use a smaller inlet (Ai = 0.30 Ab) for the same performance (same losses)
that you get with a larger opening Ai = 0.44 Ab for the pure Wedge.
But, that is just my take on it.
The slight bump (where the 64
deg angle is annotated) of the Streamline wedge may be to increase the
boundary layer velocity to delay separation of the boundary layer in
that far corner where duct meets core.
Ed
Ed
Anderson
Rv-6A N494BW Rotary
Powered
Matthews,
NC
eanderson@carolina.rr.com
http://www.andersonee.com
http://www.dmack.net/mazda/index.html
http://www.flyrotary.com/
http://members.cox.net/rogersda/rotary/configs.htm#N494BW
http://www.rotaryaviation.com/Rotorhead%20Truth.htm
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