On 06/07/2010 01:41 AM, Fred Klein wrote:
> If Frans is correct, it would appear to follow that the 912S plenum does
> not offer inlet air to the carbs under ram air pressure.
There is quite some information available on the internet about
naca-ducts, where they were designed for, and what they can and can't do.
Naca ducts were designed for applications where you want to "let air in"
without drag penalty. They harvest air from the boundary layer, the
non-moving layer of air attached to the airplane.
If you need RAM air, you need something to protrude through the boundary
layer, a sort of scoop, or a frontal inlet.
See:
http://www.flyingmag.com/scoop-naca-scoop
" ... The conclusions of the Ames group's 1945 report were upbeat, but
they included a caution that designers have been ignoring ever since.
"The submerged inlet is essentially a high inlet-velocity-ratio type in
contrast to wing-leading-edge and fuselage-nose inlets," they wrote.
This characteristic limited its most efficient use to systems "that
require only a small amount of diffusion, such as the internal ducting
for jet motors of the axial-flow type." Submerged inlets were unsuitable
for "oil coolers, radiators, or carburetors of ... reciprocating
engines," the report continued ... "
Of course, if there is anyone willing to measure the pressure inside a
naca duct against the static port (ASI ?) we know for sure. But as far
as I can see, the 912S naca inlet doesn't provide any ram effect to the
inlet air.
Frans
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