FlyingBattery26
Topic Author
Posts: 22
Joined: Wed Mar 27, 2013 3:22 pm

Open Rotor Engines - The Future?

Wed Mar 27, 2013 4:29 pm

I was just wondering, what is the probability that open rotor engines will replace jet turbofans in the future? I have been doing a lot of reading on the subject, and from my understanding they are more fuel efficient but also slower and noisier than conventional turbofan engines.. they're also quite hideous looking in design. I personally don't like them, and would hate to see them replacing the turbofan jet engine that we all know and love. Would anyone care to comment on this?

For those of you who don't know about these engine types, here's a link: http://www.sustainableaviation.co.uk...en-rotor-engine-briefing-paper.pdf

What they look like:
 
cornutt
Posts: 333
Joined: Sun Jan 20, 2013 6:57 am

RE: Open Rotor Engines - The Future?

Fri Mar 29, 2013 3:39 am

AFAIK, everyone has given up on those things. They seemed like a great idea in the late 1980s when they promised to be a lot more efficient than the turbofans that existed then. But I believe the ultra-high-bypass turbofans we have now have matched what the unducted fans were going to accomplish in efficiency. And no good solution for the noise of the UDFs was ever found.
 
wingscrubber
Posts: 806
Joined: Fri Sep 07, 2001 1:38 am

RE: Open Rotor Engines - The Future?

Fri Apr 12, 2013 9:47 am

The concept of bridging the gap between a traditional turbofan, and a contra-rotating twin-prop turbofan is a viable one, as it seeks to find the sweet-spot between max fuel efficiency and highest economical cruise speed. Combining technologies such as gear-reduction and variable pitch blades could achieve a very efficient engine that sits somewhere between a turboprop and a turbofan.

The problem with the UDF though is the noise! the open rotor engines would work if only they put a duct around it, something like Kuznetsov NK-93 is a good example of what could be done, but Russian aerospace companies just don't have the economical clout to bring a concept like this to fruition, and western aerospace companies are too risk averse to try anything so radical. It'll be a long time before any commercial aircraft are flying with turbine engines this advanced.


View Large View Medium
Click here for bigger photo!

Photo © Ilya Morozov

Resident TechOps Troll
 
User avatar
TWA772LR
Posts: 3605
Joined: Thu Nov 17, 2011 6:12 am

RE: Open Rotor Engines - The Future?

Sun Apr 14, 2013 7:10 am

Quoting wingscrubber (Reply 2):

The concept of bridging the gap between a traditional turbofan, and a contra-rotating twin-prop turbofan is a viable one, as it seeks to find the sweet-spot between max fuel efficiency and highest economical cruise speed. Combining technologies such as gear-reduction and variable pitch blades could achieve a very efficient engine that sits somewhere between a turboprop and a turbofan.

Couldn't an engine manufacturer make a turbofan engine with two main fans before the core and make them variable pitch?

Side question, does any contra-rotating prop powered aircraft have variable pitch props?

[Edited 2013-04-14 00:12:19]

[Edited 2013-04-14 00:13:07]
Not every day we find light winds. What do we do in these situations? Fly.
 
User avatar
Starlionblue
Posts: 17053
Joined: Fri Feb 27, 2004 9:54 pm

RE: Open Rotor Engines - The Future?

Sun Apr 14, 2013 7:50 am

Quoting TWA772LR (Reply 3):
Couldn't an engine manufacturer make a turbofan engine with two main fans before the core and make them variable pitch?

Sure. But it's not a simple solution and apparently current solutions are still better.

Quoting TWA772LR (Reply 3):
Side question, does any contra-rotating prop powered aircraft have variable pitch props?

I don't have the data but I would think all of them do. Only the simplest propeller planes have fixed props in my experience. It would seem a terrible waste to go to all the trouble to make contra-rotating props without implementing a hundred-year old technology like variable pitch.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
jetlife2
Posts: 179
Joined: Sun Jul 09, 2006 11:32 am

RE: Open Rotor Engines - The Future?

Sun Apr 14, 2013 3:53 pm

Open rotor solutions are being studied for next gen narrowbody aircraft, 2030+. The noise problem has been largely solved using current gen aero tools that were not around in the time of the UDF; and this has been validated by test. Remaining hurdles are mostly regulatory (not a turbofan; not a propeller; rules are very different). This technology is very likely the next generation; of course new airframes are needed, so given the current narrowbody space, there will be many years of study before the industry is ready for that investment.

[Edited 2013-04-14 08:55:39]
My views are not necessarily the views of the GE Company
 
User avatar
Stitch
Posts: 22937
Joined: Wed Jul 06, 2005 4:26 am

RE: Open Rotor Engines - The Future?

Sun Apr 14, 2013 4:23 pm

I think UDFs might have a chance in the sub-150 seat market for regional work where distances are short enough that the slower cruise speed doesn't really matter. One issue with UDFs is that they have to be mounted in the rear so you're not going to see a UDF-powered plane larger than an MD-90.
 
JoeCanuck
Posts: 3939
Joined: Mon Dec 19, 2005 3:30 am

RE: Open Rotor Engines - The Future?

Sun Apr 14, 2013 4:41 pm

The new generation of jet engines, (especially the GTF), is already encroaching on the fuel efficiency estimates achievable by the Open Rotor engines.

I suspect that the Open Rotors will never be efficient enough to justify the cash to solve the speed and blade out problems. The GTF is such a simple design with a lot of room to improve still.
What the...?
 
United727
Posts: 351
Joined: Sat Nov 13, 2010 1:26 am

RE: Open Rotor Engines - The Future?

Sun Apr 14, 2013 5:45 pm

Quoting jetlife2 (Reply 5):
Open rotor solutions are being studied for next gen narrowbody aircraft, 2030+.

Thus one would expect...

Quoting Stitch (Reply 6):
that they have to be mounted in the rear so you're not going to see a UDF-powered plane larger than an MD-90.

I would expect up to Twin 757 "ish" size based on the 757 original model with the T Tail design. It's possible!
 
User avatar
DocLightning
Posts: 19606
Joined: Wed Nov 16, 2005 8:51 am

RE: Open Rotor Engines - The Future?

Sun Apr 14, 2013 9:15 pm

Quoting jetlife2 (Reply 5):
Remaining hurdles are mostly regulatory (not a turbofan; not a propeller; rules are very different). This technology is very likely the next generation; of course new airframes are needed, so given the current narrowbody space, there will be many years of study before the industry is ready for that investment.

Not just regulatory.

The development of a new airliner powered by such an engine will be astronomically expensive. No airframe manufacturer is going to just dive into this technology and risk bankrupting their company without seeing it in action on a smaller scale first. I predict we will start seeing UDF's in private aircraft first.

It is very rare that the industry wholesale adopts a new propulsion technology. Jet engines were available long before the 707. CFRP has been in use for major structural members for years now. Turbofans get better and better over time, too.

The OEM's and airlines are going to need a lot of convincing.
-Doc Lightning-

"The sky calls to us. If we do not destroy ourselves, we will one day venture to the stars."
-Carl Sagan
 
rwessel
Posts: 2448
Joined: Tue Jan 16, 2007 3:47 pm

RE: Open Rotor Engines - The Future?

Mon Apr 15, 2013 4:28 am

Quoting DocLightning (Reply 9):
Jet engines were available long before the 707. CFRP has been in use for major structural members for years now. Turbofans get better and better over time, too.

Boeing (not that they were actually first) started work on a jet transport, what was to become the 367-80 (and then the KC-135 and 707), in 1949. Barely a decade after the first jet took flight (the Heinkel He178, on 27-Aug-1939). And it's hard to credit turbojets as any sort of serious aircraft propulsion system before about 1943/44.
 
eaglepower83
Posts: 357
Joined: Tue Oct 04, 2011 2:54 pm

RE: Open Rotor Engines - The Future?

Fri Jun 07, 2013 8:21 pm

Quoting DocLightning (Reply 9):
The development of a new airliner powered by such an engine will be astronomically expensive. No airframe manufacturer is going to just dive into this technology and risk bankrupting their company without seeing it in action on a smaller scale first.

Indeed.
The GTF wasn't even taken seriously by airframers until Pratt started building and flying them around ..... and only after hundreds of on-test bed hrs did anyone actually come to the table. Then once some small airframers started choosing it, did Airbus explore and offer the GTF for Neo.
Boeing is even more sceptical on the GTF.....plus they're in tucked in bed with CFM.

Who is online

Users browsing this forum: No registered users and 14 guests