lehpron
Posts: 6846
Joined: Tue Jul 10, 2001 3:42 am

Electric Fan Motor Set Does What?

Mon Sep 05, 2005 1:29 pm

Would an electric motor attached to a ducted fan increase flow velocity, pressure, temperature, two of the above or all of them?
The meaning of life is curiosity; we were put on this planet to explore opportunities.
 
FredT
Posts: 2166
Joined: Thu Feb 07, 2002 9:51 pm

RE: Electric Fan Motor Set Does What?

Mon Sep 05, 2005 3:41 pm

Velocity, yes. Pressure, but only immediately behind the fan. As the air accelerates, the pressure will even out. And as there will be friction, temperature as well although not by much... and the cooling of the motor will probably generate more heating of the air than the friction.
I thought I was doing good trying to avoid those airport hotels... and look at me now.
 
abbs380
Posts: 118
Joined: Mon Mar 21, 2005 11:25 am

RE: Electric Fan Motor Set Does What?

Mon Sep 05, 2005 5:35 pm

Lehpron, Im not sure what you are getting at, or how important the electric motor is, but if you are interested in ducted fans, vis a vis, aircraft check this out. It may knock your socks off.

http://www.custerchannelwing.com/
 
lehpron
Posts: 6846
Joined: Tue Jul 10, 2001 3:42 am

RE: Electric Fan Motor Set Does What?

Fri Sep 09, 2005 2:06 pm

Thank you FredT, that answered my question. But if the motor gives off some heat then shouldn't the pressure increase slightly, even if negligible?

Abbs380, I meant that any info on ducted fans led me to jet variants and if I asked about propellers I would have gotten piston-based ideas. I have never seen that plane in the link you provided before. A facinating read.

[Edited 2005-09-09 07:07:48]
The meaning of life is curiosity; we were put on this planet to explore opportunities.
 
FredT
Posts: 2166
Joined: Thu Feb 07, 2002 9:51 pm

RE: Electric Fan Motor Set Does What?

Fri Sep 09, 2005 5:25 pm

There's nothing containing the air inside the duct. Thus, it will expand to ambient pressure. As the air is heated, this means it will expand to a slightly greater volume - but it will still expand to ambient. In effect, you get a slight thrust increase from the heating of the air, just as in a ram engine.

As a sidenote, the heat exchanger under the P51 Mustang will often contribute thrust due to the design of the duct and the heating of the air inside it. Ram engine...  Smile

Cheers,
Fred
I thought I was doing good trying to avoid those airport hotels... and look at me now.

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