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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