"Jim Carriere" wrote in message
...

This is a better explanation than I gave, but I'll elaborate further to
this that while technically only 15 of those parts of air are "burned"
(use to support combustion), and the secondary air begins mixing with the
flame very close to where the fuel nozzle(s) are located. Depending on
the design of the engine, some or even all the secondary air flowing
around the combustor liner mixes with the primary air/flame before
entering the turbine.

Complex engines will route some of the secondary air through tiny cooling
passages in the turbine blades themselves (I'm pretty sure you, Colibri,
understand this, I'm speaking to the group and not trying to insult you),
but I strongly doubt this is the case with Juan's engine.

You are correct. My engine is not a turbofan, it is a turbojet, circa 1973.

None of this is impingement starting air, which hits the turbine blades
and then goes right out the exhaust duct.

This is an important distinction, so is the difference between secondary
and bypass.