ORIGINAL: iron eagel
"The inlet is a strange thing to analyze -
It appears to be a "ram air " inlet - it isn't.
actually -the air behind the prop - at the base of the prop -is somewhat stagnant (?)
What I mean is that it is swirling and moving outward at that point on the prop--so no air is being rammed into the cowl.
The exit air (lowering of pressure in the cowl) is the controlling factor.
a very small inlet does the job as long as the exit air pressure drop is sufficient"
Dick I really don't understand that...
whereas in FS we were told:
Basic principles of air cooling
. This ambient air creates a high pressure area inside the engine cowling than the static air around the aircraft."
I clipped out this part of the quote-because --in order for the air to flow thru the fins the pressure in the cowl must be lower not higher than ambient.
A cowl full of high pressure air is a burnt up engine waiting to happen
Cowl flaps on an old radial create a powerful low pressure at the rear of the engines -this is what creates the flow. NOT high pressure blowing air thru the engine. IF there is positive pressure at the inlet it does help but in many cases there is little or no pressure at the base of the prop.