Jet engine

[expat]

1. N1 and N2? Do turbojet engines which have only one turbine have also this N1 and N2 or only other jet engines which have 2 turbines instead of one? Like turbofan, turboprop and turboshaft?

2. I know that N1 is the rotational speed of the low pressure compressor and N2 is the rotational speed of the high pressure compressor and N2 always has a higher RPM percentage. How come they are not rotating at the same speed and how is this possible?
Does the letter 'N' up here mean something or not?

3. Do I have to monitor N2 and is it spinning faster than N1?

4. Some aircraft like Beechcraft King Air 350 with a turboprop engine has a torque gauge in percentage (some in ft-lbs, what is that) and a gas generator RPM gauge. What does each of these gauges show?

5. On a piston engine the propeller spins faster and faster as airspeed increases. Does the RPM of the compressor and the turbine also increase with airspeed?

6. When power is set to reverse in aircraft with turboprop engines does the turbine continue to spin in the same direction or what? How is this reverse achieved? I don't see any changes with the propeller rotation.

I would suggest getting hold of a copy of this book: Rolls Royce Jet Engine Book A new version or a second hand older version will answer all the questions you have. This book is the basic course for jet engines whether you are schooled by the RAF (as in my case......many moons ago) or do an apprenticeship with British Airways or anyone else for that matter. I could answer all your questions here, but the answers would just lead to more questions. This book is a bible.   Try and get hold of it and all will become very clear. A word of warning, don't get it from Amazon or Ebay........you will pay very silly money if you do.

Matt

[Slotback]

1. Look at this photo of a turboFAN.

http://upload.wikimedia.org/wikipedia/c ... ration.svg

See the 'low pressure shaft'? That's N1.
See the 'high pressure shaft'? That's N2.

N1 gauges thrust the best because the majority of thrust is produced by it.

SOME engines have THREE spools because it's slightly more efficiant but more complex and heavy.



Now look at this turboJET.

http://upload.wikimedia.org/wikipedia/c ... ne.svg.png

It's single spool, so I doubt they'd call it N1 or N2... just 'engine RPM' or something. HOWEVER, there is no reason why they cannot be dual spools, & I'm sure some engines do have dual spools.

I don't know much about turboprops...

[Mobius]

Ft-lbs is indeed a measurement of torque, and power output can be found by multiplying the torque output by the engine rotational speed:

Power = Torque x Speed

So it seems it's just another way of showing engine load or thrust output.