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bix wrote:

Basic theory, maybe, but the "coupled" statement must have been made by an AF Engineer who writes TOs for a living, and has never even seen a jet engine operate from the control cab.

An engine will make pleanty of power without the nozzle, just not "optimum". Commercial turbofans don't have variable nozzles on their fan or core flow. Biggest problem of not having a nozzle is N1 speed. Without the backpressure that would be presented by a closed nozzle, the fan has nothing to hold down it's RPM, and the core is pumping heat to the N1 turbine as if it had a nozzle to control it............BANG!

Speaking of "engine lore", want to get into the how does a jet engine moves?
1. Screws it's way through the air like a propeller
2. Pressure on the turbine wheel pushes it forward
3. Pressure in the combustion chamber pushes it along
4. Mass acceleration through the engine
5. Pressure at the front of the engine is less than inside the engine...........
Shall I go on!?

I've had debates on that with 20+ year jet engine mechanics!

You Make a good point of how the engine works bix. So let me see if I have this right.... the engine works like this..... SUCK BANG BLOW..... hmm sounds like I might need to go the drug store after that Twisted Evil

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Joined: Feb 01, 2007 Posts: 0 Status: Offline

Joined: Feb 01, 2007 Posts: 0 Status: Offline

Must be a CC, there is a SQUEEZE in there between the SUCKing and BANGing........

Back to Engine Fam.

Very Happy

bix wrote:

Must be a CC, there is a SQUEEZE in there between the SUCKing and BANGing........

Back to Engine Fam.

Very Happy

touche'

Quote:

When flying the fan and core are areodynamicly connected, one will not go faster than the other.

Not a 100% true. It is still possible for the fan to overspeed. Since your DEC is the only thing controlling your fan speed.

Veteran Joined: Jul 21, 2005 Posts: 471 Status: Offline

Yes, I can throw in an engineer's perspective... well because I can and it's 2:30 am and I'm bored. The philosophy my prof taught me was Suck Squeeze Burn Blow. Pretty friggin kinky aye? The F-16 is a two spool engine right? This is so you can take advantage of the rising temperature in the engine as you compress the air more. You can spin the core faster because the speed of sound rises and the tips won't shock (not good). Whatever, you guys know this so I have no idea why I'm saying this. Oh yeah, it's 2:30. Do the two spools on the engine spin in the same direction (I've seen examples where they spin different ways)?

No prob. To be honest with you. The direction of rotation of your Low Pressure (LPT, Fan) and core (HPT, compressor) is the same direction. Like I said earlier, you Fan speed is controlled by your DEC (Digital Engine Control). The DEC schedules more fuel, core turns faster, high pressure air comes off the High Pressure Turbine (HPT), hits the Low Pressure Turbines (Free Spinning), diriving how fast you fan turns. The DEC slows down fan speed by regulating the Inlet Guide Vanes (IGVs), limiting the amount of air into the engine with out causing a stall. It's not about sound, it's about air picking up velocity, compressing, igniting, high pressure, then BOOM!!

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