Thread: Discussion F22 Raptor Drawings - Update
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Old Feb 08, 2008, 09:49 AM
Ron Pogue is offline
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Hi nem -
Your CAD skills are very good, I am envious!
I have a few observations about ducts that you may find entertaining.

In my opinion, in an inlet duct, air flows fastest at the center of the duct, and slower near the duct walls. This is due to friction, air viscosity, surface effect, boundary layer, whatever you want to call it.
Since the air is traveling faster in the middle of the duct, it becomes more important to streamline the center. Most of the supplied fans give us these big, blunt, spinning obstacles right in the middle of the fastest moving airstream. Some way needs to be found to move the air gently away from the center. Perhaps a model rocket nosecone (the long graceful kind) in front of the fan spinner would help. The nosecone could be supported by a thin wall across the diameter of the inlet duct.

The outlet duct is a differant matter. Since the fan imparts a large 'spin' on the airstream, centrifugal force might tend to force a lot of the airflow outwards, towards the duct walls. Any corners, (as in square outlets), might restrict the aftward flow, and have the same affect as necking down the outlet.

The above is presented not as proven fact, but rather, as an opinion. Your mileage may vary.

Darn F22s are very duct intensive!

Ron
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