Intake runner sizing..

Bruce Bowling bowling at cebaf.gov
Thu Feb 22 19:44:16 GMT 1996


~ Looked up the basic equation, and it should work for Rotary engines.  One 
~ question, however.  I've heard mentioned that the airflow through a 
~ rotary is essentially twice its "displacement".  I've pretty much ignored 
~ rotaries, so I'm not sure how technically sound this is...
~ 
~ Anyways, here is the equation:
~ 
~    _c_ {_(ab+a+1)+-(((ab+a+1)^2 - 4ab))^.5_}
~ f= 2pi {         2ab(L/A)sub 1 * V sub 1   }
~ 
~ where:  a=(L sub 2 A sub 1)/(L sub 1 A sub 2)
~ 	b=(V sub 2)/(V sub 1) 
~ 	V sub 1= Vswept/2*((CR + 1)/(CR - 1))
~ 	c=speed of sound
~ 
~ CR:  Volumetric Compression Ratio
~ L sub 1:  Inlet pipe length
~ A sub 1:  Inlet pipe area (cross sectional)
~ L sub 2:  Air duct length
~ A sub 2:  Air duct area (cross sectional)
~ 
~ 
I have been lurking for this for some time (I have a WWW page
just licking its chops for this info).....

A few questions:
The equation appears to be a solution for a quadratic. Is the sign
of the numerator term (ab+a+1), (the term before the +-), really
positive?

The denominator term of 2ab(L/A)sub 1, I do not see the definition
of this (to reference the "sub 1").  Or is this just 2ab(L/A)?

Is Vswept the volume swept by the piston?

Are the units self-consistant (i.e. use feet in speed of
sound and cubic feet for Vswept, and feet for lengths and
cross-sections.

Very nice info - Bruce

--
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               Bruce A. Bowling
  Staff Scientist - Instrumentation and Controls
 The Continuous Electron Beam Accelerator Facility
    12000 Jefferson Ave - Newport News, VA 23602
                 (804) 249-7240
                bowling at cebaf.gov  
        http://devserve.cebaf.gov/~bowling
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