Bryan Becker
Topic Author
Posts: 327
Joined: Fri Mar 02, 2001 12:38 pm

Exhaust Efficiency

Thu May 10, 2001 10:03 am

In a turbojet where you use the exhaust (thrust) to power what ever you have it on.Does the design of the exhaust exit have any affect on how the engine will perform,what I mean is will the way that the exhaust exits the engine have any affect on how much power you will get out.Like does a smaller diameter area where the exhaust exits have better results in thrust or a bigger diameter?Like VEN's on jets they control the diameter of the exhaust exit,I know that it maybe would have to do with what it was made to do the engine that is.Or that the design of the exhaust exit realy has nothing to do with the performance as long as the exhaust exits the engine.And realy how many different exhaust exit designs are made or produced.And what kinds of things can be done to a turbojet to make it more power efficient and fuel efficient?If this makes no sence to you please forgive me!!!! Smile

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Posts: 1048
Joined: Fri Mar 23, 2001 8:10 am

RE: Exhaust Efficiency

Thu May 10, 2001 10:49 am

The exhaust gases have to be properly directed when exiting the engine. Otherwise, potential thrust will be lost because not all the gases will exit in the same direction. The exhaust nozzle must be wide enough to prevent building pressure from blowing the engine's rear, but must be small enough to produce efficient high speed exhaust.
It's not much but hope it helps!

Posts: 3094
Joined: Tue May 18, 1999 6:40 am

RE: Exhaust Efficiency

Thu May 10, 2001 12:07 pm

You are getting into the physics of fluid dynamics something which should not be attempted on a mesage borad.

The size of the engine exhaust is in direct relation to exhaust gas velocity.

You need to get everything that goes in a jet engine out.

So the exhaust area is a direct tradeoff between velocity and pressure. An increase in pressure is a decrease in velocity.

The exhasut nozzle must be of appropriate size to maintain a balance between the two in order to be most efficient.

You don't use a firehose to dribble water.

And you don't use your garden hose at 3000 PSI. Although that would be pretty cool.

Posts: 129
Joined: Thu Dec 30, 1999 7:41 am

RE: Exhaust Efficiency

Sat May 12, 2001 12:10 am

jet pilot is very right.
this subject goes too far for the forum. get some good books on jet engine thermo and you'll find they tell you (nearly) all about how to get your exhaust nozzle right.
don't give up.
 Smile/happy/getting dizzyFW

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