# Jet Thrust

#### vincentryan

Hi,
i am trying to increase the jet engine thrust. today most of the aircrafts are using high bypass ratio turbofan engine. thurbofan engine delivers thrust in two steps
one: hot exhuast gas
second : by pass air
how i have to find the thrust developed by the bypass air?
how i have to find the thrust developed by the hot exhaust gas?
GE90- 115B turbofan engine delivers total thrust of 115,000 pounds of thrust, in that how much amount of thrust delivered by the bypass air and by the hot exhaust gas?

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#### Danger

Gold Member
Welcome to PF, Vincent.
I believe that Fred Garvin is the guy to answer your questions. Bear in mind, though, that since he designs jets for a living, he won't give you any proprietory information.

#### Astronuc

Staff Emeritus
I'll defer to Fred on this, but I've looked at lots of articles and not one showed the fraction of thrust from the jet exhaust or bypass flow. I would guess that the exhaust thrust is about 20,000 lbs or so, based on the CFM56 technology.
http://www.cfm56.com/index.php?level2=engines&level3=1126

I did find some cool stuff though.

http://www.snecma.com/IMG/pdf/GE90_Anglais-2.pdf [Broken]

http://www.ihi.co.jp/ihi/file/technologygihou2/10006_1.pdf [Broken]

http://en.wikipedia.org/wiki/GE90

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#### vincentryan

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#### FredGarvin

That is exactly correct. However, you will not always know the velocities of each stream as required by that page. You may need to delve farther into the thermodynamic relations for the turbofan cycle. You may look to this (usually one starts with known conditions at the inlet and works their way to the back end of the engine):

http://en.wikipedia.org/wiki/Jet_Engine_Performance

#### Astronuc

Staff Emeritus
Just as Fred mentioned, one needs to know the velocities of the jet exhaust and bypass flow (exit).

"Jet Thrust"

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