volumetric efficiency

[Bruce Bowling]

~ How can vol. eff. be greater than 1?
~ 
~ Mattias Nyberg
~ 
Quoting from the superflow flow bench manual:

"Inertial Supercharging Effect:

When the intake valve starts to close, the fast moving air column 
tries to keep ramming itself into the cylinder. If the inlet
valve is closed at just the right instant, the extra charge will be trapped
in the cylinder (called inertial supercharging).  Volumetric efficiencies
up to 130 percent can be obtained......."

They then go on to define the inertia-supercharge index Z, which
is an empirical value which is a measure of the strength of the
inertia supercharge.  To compute this:

1) Find Cv = (valve flow (total) for one cylinder filling event at given test pressure)
	     ---------------------------------------------------
	     (Maximum flow possible at given test pressure)

   Cv is intake system flow rating (normalized)

2) Find average inlet valve area:

   A = Cv * (valve area in sq. inches)

3) Compute Z:

     Z=((RPM/126000)) * sqrt((CID * Inlet Length)/(A))

Z will usually be between 0.9 and 1.2 

- 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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