Mailing List flyrotary@lancaironline.net Message #45093
From: Lynn Hanover <lehanover@gmail.com>
Subject: Bernulli's Principle
Date: Sat, 7 Feb 2009 15:32:42 -0800
To: <flyrotary@lancaironline.net>
I invite you to the Bernulli Principle web site.
 
http://home.earthlink.net/~mmc1919/venturi.html
 
 
I did some shapes to play with in the attachment.
 
Leave the reverse cone at the right end to replicate the port into the chamber. Note a little yellow sign pop on when flow slows too fast and separates.
 
This would be at the bowl shape where the flow makes the 180 turn into the chamber. This area is too big volume wise and costs power. Some racers fill this in slightly to eliminate this problem. The lack of this feature in the periphery port engine makes a huge difference, in that velocity is carried right into the chamber, rather than slowing.
 
Although not practical the ideal shape is probably a long tapered runner. So velocity rate of increase is a constant value.
 
Imagine that the mixture is a sausage, and you want the biggest piece of sausage cut off by each rotor face.
The highest possible velocity is important for that. However the high velocity creates the highest drag over a long distance.
 
Two 44MM chokes in a Weber is enough for 310 HP at 10,300 RPM from a 12A. The TB size need not be the runner size. My engine with a bridgeport gets 250 HP at 9,400 RPM from two 38MM chokes.
 
Short runners for high RPM. Long runners for low RPM.
 
Big runners slow velocity and ruin low speed performance with big thin pieces of sausage. Small runners give crisp low speed performance with smaller, longer pieces of sausage.
 
Now you won't sleep tonight either.
 
Lynn E. Hanover
 
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