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October 27, 2003
Ed...
This is strictly a matter of density altitude
or to put it differently, the amount of air
molecules per cubic foot of.....air!!
The air at 10,000 feet is much "thinner"
than the air at sea level...it is much
"lighter" per cubic foot. Fr'instance, at sea level a
cubic
foot of air weighs 14.7 lbs. It weighs half
of this at an altitude of 18,000 feet.
The adiabatic lapse rate (temp. change per thousand feet) and it's
humidity figure
into this but we'll ignore these for now.
So for the volume of air taken in at
10,000 feet, you are getting fewer molecules of air per cubic feet than
you would get as sea level.
So in terms of a normally aspirated
piston engine, as in automobile,
the operational upshot of this is you
require less fuel for a "proper" ignitable
mixture at altitude, than you would at sea level.....so.....
a given engine would produce less power
at any given throttle setting at higher altitude than it would at sea
level, feeding
it the proper amount of fuel for a "correct"
mixture, air induction system notwithstanding.
Turbo and supercharged engines do better
because they pack in greater volume to
make up for the reduced molecules in
a given cubic foot of air at altitude relative
to it's brother cubic foot of air found at sea level. Turbine engines
also do better at
this as well...they are great at packing in
"thinner" air, relatively speaking.
Cap'n. Bob
'60 :{)
PilotRob@... 26347
Posted on October 27, 2003 05:24 AM
Posted to category(s) Carburetor | Engine (external) | Engine (internal) | Forced Induction | Fuel System | Gauges | Intake System | Tuning
