Qs about turbofans

[jetman]

i guess the reason for me to ask about RPM was to figure out if the fan blades went supersonic and if so how is the problem of increased drag,shock waves,noise were solved.Same applies to compressors and turbine blades for they are all airfoils of some kind and have similar caracteristics to wings.
As for the smaller size of the turbine and compressors in turboprop engines,compare to turbofans, the power turboprops developed is much less than a turbofan engine also turbofans do not have a reduccion gear to power the fan that sares the same shaft with the low pressure compressor and probably is much slower than N2.
OK guys i did not mean to be a smart a........./// asking so many questions that are probably irrelevant to the everyday ops but i like to know and i found in this forum people MUCH MORE SMARTER than im and i hope toe learn something////

but ..............
Could the fan blades be made like a variable pitch prop to increase efficienciy?

maybe thats a topic for another day

.
regards jetman

 

[ERAU_Intern]

Actually jetman, there are a few engines in developent right now that have variable geometry fan blades. The problem is that this presents EXTREME complexity increases in already complex engines. You would need something to power the movent of the blades (pneumatic, hydraulic, or electric), and you would need a more sophisticated engine control system (FADEC), in order to accomplish this. The 777's fan blades actually break the sound barrier slightly at the tips, and if you listen to one go buy you, you will hear a growling sound as it passes. That is the sound of a bunch of little sonic booms in the engine housing, from the fan!

 

[IrishSheepdog]

The technology for variable vanes doesn't need to be THAT elaborate. I mean, our Saab has them, so it can't be THAT complex!

hehehe

We have variable inlet guide vanes/variable stator vanes. The first three stages of stator vanes (between compressor blades) vary in pitch thanks to mechanical movement from the Hydromechanical Unit.

 

[CF6_rep]

Looks like the others have answered for commercial engines, but I used to be a rep on the F110 engine that powers the F-16 C/D aircraft. That engine turned about 8,000 RPMs for the N2 and about 15,000 for N1 at full throttle. As a little side note, when we went into augmenter (afterburner) it was pumping about 55,000 lbs/hr.

 

[derg]

Here's a spot of trivia for you guys:

"What was the PT6 turbine engine originally designed to do?"

 

[IrishSheepdog]

Hmm, I'd say power helicopters? That's what our Saab 340 CT7-9B engine was originally for!

 

[JDMcFly]

Engine like things?

 

[derg]

I was told that the original PT6's were used to power oil drilling machines.

 

[Mr_Creepy]

I'll take a shot. I heard it before but I'm having memory problems which is not unusual for my age group.

I believe it was:

a) Turbine for Electric Powerplants, or
b) Turbine for Air Conditioning

I will really laugh if it was designed to dry the track at NASCAR events

 

[seagull]

The rotation speeds of turbojet/turbofan are under 10k, the turboprop engines have very high rotation speeds. Much smaller turbine/compressors. For the internal combustion engine, think turbochargers, not the engine itself, for a more reasonable comparison.

As for knowing the speeds, I would say that any training program that asked the question or even gave the answer as part of the normal course is in need of serious overhaul, it is totally useless information for the pilot.

 

[ananoman]

The turbochargers in some piston engines spin at 90,000 rpm.

 

[Cleared_ILS_RWY_9L]

Doug-
A GE tech-rep and I were talking about the engine I used to overhaul, the T-58 turboshaft. He was telling me about a call he got month before from a farmer who used the engine as a pump motor. He ran the engine for 10 years before he shut it down for inspection. He called because he couldn't figure out how to start it again. The thing had run for 10 years straight.

 

[rausda27]

Was it for pumping stations for gas and oil pipelines and/or marine propulsion systems for ships?

 

[CF6_rep]

I'm guessing it was for an individual user with a smaller type farm or something since the T58 is an older engine and relatively small. Most gas pipelines and ships use the larger "LM 2500s or larger. It is true that they can operate literally for years because what really ages engines are the thermal cycles from starting, operating and shutting down. Lots of the aero-derivitive engines only shut down on holidays, etc. when there is no need to pump oil, natural gas, etc. I know some GE reps on the aero-derivitive side of the house. Who was the GE rep (maybe I know the guy)? Small world...

 

[Mr_Creepy]

I wish Doug would answer the question

I'm getting curious!!!

 

[derg]

I did!

 

[Mr_Creepy]

You must have answered it while I was typing my "guess" - I just saw it now.

Never heard that one about oil drilling machines - hmmm.

 

[Cheechako]

Power a tank?

I think the M1 Abrams has PT-6s. . .

Something agricultural, I think. That's what the "A" stands for in PT-6A.

Drive a generator?

 

[MikeD]

bumped for interest

 

[PeanuckleCRJ]

The PT-6 was originally designed as an oil pipeline pump driver thingy or whatever you call it. Pretty neat.

The CRJ N1 (fan) speed is around 8900 RPM at 100% N1. Not sure about the N2 (core) speed...unfortunately our manuals do not mention it.