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Exhaust Efficiency  
User currently offlineBryan Becker From United States of America, joined Mar 2001, 333 posts, RR: 0
Posted (15 years 2 weeks 6 days 10 hours ago) and read 1262 times:

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

-BB Big thumbs up

3 replies: All unread, jump to last
User currently offlineBio15 From Colombia, joined Mar 2001, 1089 posts, RR: 7
Reply 1, posted (15 years 2 weeks 6 days 9 hours ago) and read 1229 times:

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!


User currently offlineJETPILOT From United States of America, joined May 1999, 3130 posts, RR: 27
Reply 2, posted (15 years 2 weeks 6 days 7 hours ago) and read 1219 times:

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.


User currently offlineF-WWAI From Andorra, joined Dec 1999, 131 posts, RR: 0
Reply 3, posted (15 years 2 weeks 4 days 19 hours ago) and read 1200 times:

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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