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jet engeins


hawk_za
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an interesting link to a manual for those of you who want to understand more about jet engines and their air dynamics its a real in depth thing and in pdf form

http://www.google.co.za/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&sqi=2&ved=0CCIQFjABahUKEwj2z9-e-vbGAhXpjtsKHVSZCyo&url=http%3A%2F%2Fwww.smartcockpit.com%2Fdocs%2FJet_Engines_Basics.pdf&ei=OduzVbbPFemd7gbUsq7QAg&usg=AFQjCNEN6m621Jio6yFwVPYFgmVB_EFjmA

yours in service

the hawk from za

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I was researching about jet engines some time back, trying to understand the efficiency against other type of engines.

But talk about efficiency in jet engines is complicated, they usually talks about thrust.

But from the energy input (fuel) to the work done.. then we can said they are 90 to 95% efficient. Something remarkable for a thermal engine.

Is hard to understand why turbines to generate electricity on the ground had much lower efficiencies. I imagine they dont have all that pressure wind entering in the engine and adding heat.

As I said.. I still dont have much clue how to calculate the efficiency.

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I was researching about jet engines some time back, trying to understand the efficiency against other type of engines.

But talk about efficiency in jet engines is complicated, they usually talks about thrust.

But from the energy input (fuel) to the work done.. then we can said they are 90 to 95% efficient. Something remarkable for a thermal engine.

Is hard to understand why turbines to generate electricity on the ground had much lower efficiencies. I imagine they dont have all that pressure wind entering in the engine and adding heat.

As I said.. I still dont have much clue how to calculate the efficiency.

Jet engines are so efficient because they use the air, which already has velocity, to oxidize the fuel. This means that the exhaust velocity is higher when the jet aircraft goes faster, to an extent.

On the ground, relative air speed is not hundreds (or thousands) of kilometers per hour, it's much less.

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Jet engines are so efficient because they use the air, which already has velocity, to oxidize the fuel. This means that the exhaust velocity is higher when the jet aircraft goes faster, to an extent.

On the ground, relative air speed is not hundreds (or thousands) of kilometers per hour, it's much less.

Also the jet engine produces trust, so the hot air who pass out back serve an purpose. On an jet turbine the hot air is exhaust, yes you use it to produce steam but its not an perfect process.

If weight is more important than fuel use you don't have the second steam stage, this is used for mobile or emergency/ standby turbines.

Nice to have on an cold day or then an major plants are down.

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Yeah I also imagine that, but still.. you get drag with the air... maybe at that speed the airflow becomes turbulent so it does not add so much drag.. but I guess the efficiency is measure on work "distance achieve with X amout of fuel" not sure, I dont remember.

The only thing that I know, is that for low speeds airplanes, the most efficient is a fuel cell, and at higher speeds, a jet engine.

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If you really want to know how jet engines work, check out a channel called AgentJayZ on Youtube. The guy works at a company that repairs old jet engines and has plenty of videos explaining just about everything you need to know about them. He even does these "Your Questions" videos where he answers questions posted by his viewers.

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