Anyone know what this is???

[UnAnswerd]

I've heard of "turbo prop" which is a turbine engine spinning a propeller. I've heard of "turbo jet" which is your typical jet engine hanging off the wings of an airliner. But can anyone tell me what in the heck "turbo fan" is???

 

[qmaster3]

http://www.aircraftenginedesign.com/abe_right3.html

 

[UnAnswerd]

http://www.aircraftenginedesign.com/abe_right3.html

Hey thanks for the link. Pretty good pictures in there. I assume you can identify a turbofan by the distinctive turbine blades in front of the engine????

 

[qmaster3]

I assume it's turbofan (blades), and turboprops (props) Of course I am just the son of a GM/Ford tech.

Avbug will probably be here shortly to write a few pages.


Here's a better link

http://www.lerc.nasa.gov/WWW/K-12/airplane/turbfan.html

 

[Singlecoil]

Hey thanks for the link. Pretty good pictures in there. I assume you can identify a turbofan by the distinctive turbine blades in front of the engine????

You can also see them hanging off the wings of 737's, 757's, 767's, 747's, 777's, Airbus', etc.

 

[Gatorman]

The difference between the two can be difficult to see for some people. Putting it into simpler terms:
A turbo jet engine has a single shaft that connects the turbines with the fan blades.
A turbo fan engine has an additional shaft with a second set of turbine blades driving the forward set of inlet blades, i.e., the fan.

Did I make that simple enough?

 

[9GClub]

Bypass ratio is a crucial concept when you're distinguishing between turbojets and turbofans. The short answer is that a turbojet sends everything it sucks in through the engine core [i.e. through the compressor(s), burners, and turbine(s)]. A turbofan, on the other hand, sends some air around the engine core. Blowers on modern military jets typically have relatively low bypass ratios, whereas large commercial fans have higher bypass ratios. For example, the P&W F119 on the Raptor runs in the 0.25:1 range, which effectively makes it an almost-turbojet. The GE90-115B on the B772LR/773ER runs about 9:1. In the latter example, this means that for every unit of air going through the engine core, you've got nine units bypassing it. High-bypass fans are typically quieter and more fuel efficient than their low-bypass counterparts, but obviously each has pros and cons depending on the application.

As Gatorman noted, modern fans can get complex because they often incorporate multiple shafts, both high and low-pressure compressor/turbine stages, etc. Another topic you might wanna research is axial versus centrifugal-flow compressors. Engine technology has come a long way since the 1930s-- to the point where GE now has in the -115B a powerplant with a thrust-to-weight ratio of around 6:1. Who knows where aerospace engineering would be if cost- effectiveness wasn't a consideration.......

 

[Tina Fey's Scar]

Make the madness stop....

 

[USMCmech]

A turbo jet engine has a single shaft that connects the turbines with the fan blades.
A turbo fan engine has an additional shaft with a second set of turbine blades driving the forward set of inlet blades, i.e., the fan.

Useually, but not always.

By defintion a Trubofan allows air to bypass the "core" of the engine where the fuel is burned.

Most of the time turbofans are "dual spool" designs, but if they only ran off of one shaft it would still be a turbofan.

 

[avbug]

Bypass air is the key to deciding if it's a turbofan. Today, most all jet engines are turbofan engines. Turbofan engines have a bigger cross section than turbojet engines.

You can tell the two apart on takeoff. Turbofan engines sound pleasant, where turbojet engines make you hold your ears. Still a nice sound, but turbojets, generally speaking, sound a lot louder.

Turbojet powerplants become more efficient with altitude; higher up the turbojet thrust is the breadwinner. Turbofan powerplants produce greater efficiency with the fan at lower altitudes, with the jet thrust doing it's thing higher up.

qmaster, do you really need several pages?

 

[qmaster3]

qmaster, do you really need several pages?

LOL

PLEEEZE, this is the only education I can afford at the moment.

 

[belchfire]

You can also see them hanging off the wings of 737's, 757's, 767's, 747's, 777's, Airbus', etc.

Er, and 707's, DC-8's (both medium and high bypass
in the conversions) and in the tails of 727s, DC-9s
MD-80s and 717s...among others!

 

[qmaster3]

Or in the engine room of most US Naval warships.

 

[bocefus]

A turbofan in a naval vessel? Where does the bypass air go?

 

[9GClub]

A turbofan in a naval vessel? Where does the bypass air go?

I'm assuming he's talking about steam turbines, not "turbofans" per se. The M1 Abrams tank is also powered by a gas turbine, but it would be misleading to refer to it as a turbofan. A turboshaft maybe, but not a turbofan.

 

[bocefus]

I'm assuming he's talking about steam turbines, not "turbofans" per se. The M1 Abrams tank is also powered by a gas turbine, but it would be misleading to refer to it as a turbofan. A turboshaft maybe, but not a turbofan.

Perhaps, I'm well familiar with turboshaft engines in marine vessels, tanks etc.
The M1 is powered by a variant of the LTS-101 helicopter engine, GE produced versions of the J-79 for marine propulsion and PWC has many PT-6 variants for marine propulsion. I can't for the life of me imagine a turbofan in any application other than aircraft.

 

[belchfire]

The BAE Jetstream has two apu's...

One on each wing!

(and they do an outstanding job of
turning kerosene into noise)

hehehe

 

[BD King]

Thanks guys. I thought a turbo fan was a groupie.

 

[9GClub]

Thanks guys. I thought a turbo fan was a groupie.

No problem, there's no such thing as a stupid question, right boys and girls!!??

Actually, wait a second.......




Incidentally, if a turbo fan is a groupie, what's a scramjet?

 

[Dizel8]

"Turbofan engines sound pleasant"

No, they sound boring. Nothing says good morning like a CJ-610 at max power early in the am.

"Incidentally, if a turbo fan is a groupie, what's a scramjet"?

You running away from the girlfriend when she says she is pregnant?

 

[TrafficInSight]

The world needs more sabreliners

 

[pilotyip]

turbo-prop-fan

Someone once experimented with a single stage extremely hi-bypass 16-blade variable pitch hypersonic blade turbo fan. The blades changed angle of attack based upon performance desired. Test flew it on a DC-9 in mid-80's. It was a cross over between a turbo prop and turbo fan.

 

[Some guy]

Think of a the fan on a turbofan engine essentially being a prop.

 

[qmaster3]

powered by a gas turbine, but it would be misleading to refer to it as a turbofan..

Correct.


Four General Electric LM2500 Gas Turbine Engines (GTEs). This is why those little DDGs are so fast.

 

[crash-proof]

Someone once experimented with a single stage extremely hi-bypass 16-blade variable pitch hypersonic blade turbo fan. The blades changed angle of attack based upon performance desired. Test flew it on a DC-9 in mid-80's. It was a cross over between a turbo prop and turbo fan.

Like this?
http://www.md-80.net/SAS-MD91.jpg

Wonder why it fizzled out...too loud maybe?

 

[crash-proof]

"Turbofan engines sound pleasant"

No, they sound boring. Nothing says good morning like a CJ-610 at max power early in the am.

I agree, i remember back in the 80s used to live by DCA when them straight-pipe GIIs would take off screamin and trailin smoke, those were the days!

I'd like to take a trip to some eastern europe airport just to relive that, those ol ruskie airliners still rumble like the cold war ain't over yet!

 

[9GClub]

GE unducted fan (UDF)

http://www.aerospaceweb.org/question/propulsion/q0067.shtml

http://www.airliners.net/discussions/tech_ops/read.main/29254/6/

http://www.airliners.net/discussions/tech_ops/read.main/2783/6/


And from http://www.airliners.net/discussions/tech_ops/print.main?id=80729:



[font=ARIAL,]Topic: RE: Is There Any Aircraft That Uses An Un-ducted Fan?
Username: Okie
[font=ARIAL, Helvetica, Geneva]Posted 2004-02-03 02:41:30 and read 1837 times.[/font]

[font=ARIAL,]I think there was a lot of R & D done on that puppy and was promising until the powers that be (FAA) determined that it had to have Containment for the blades.
[/font]

[/font][font=ARIAL,]Topic: RE: Is There Any Aircraft That Uses An Un-ducted Fan?
Username: LMP737
[font=ARIAL, Helvetica, Geneva]Posted 2004-02-03 02:54:28 and read 1790 times.[/font]

[font=ARIAL,]Some of my former co-workers at Boeing Flight Test Long Beach worked on the UDF program during the MD days. They said while the engine was good on gas the noise inside the rear cabin was almost unbearable. Not exactly passenger friendly.[/font]

[/font][font=ARIAL,]Topic: RE: Is There Any Aircraft That Uses An Un-ducted Fan?
Username: GrandTheftAero
[font=ARIAL, Helvetica, Geneva]Posted 2004-02-03 08:14:39 and read 1662 times.[/font] [font=ARIAL,]Economics had a lot to do with it, too. The UDF was designed with lower SFC in mind. With the price of petroleum no longer a critical issue near the end of NASA's Advanced Turboprop Program study, airlines didn't see any reason to build airplanes with unducted fan engines.

On a related note... The SFC reduction than can be expected in future high-bypass ratio turbofan engines, such as the ones that are currently being proposed for the 7E7, will surpass the efficiency of the UDF.

--Shane[/font]

[/font]

 

[bocefus]

Oh yeah, I have a fair amount of time onboard the IL-76 many of them have "STAGE 3" stenciled on the nacelles, what a joke! Go to the Emirates or anywhere in Africa and you can see/hear plenty of them. They are becoming more and more rare in Eastern Europe and banned thoughout most western Europe.