Sponsor Message:
Aviation Technical / Operations Forum
My Starred Topics | Profile | New Topic | Forum Index | Help | Search 
Unducted Fan Engine  
User currently offlinesurajit001 From India, joined Dec 2012, 7 posts, RR: 0
Posted (1 year 7 months 1 week 3 days 2 hours ago) and read 2953 times:

I was going through the mechanism of Ultra High Bypass Engine type and i found out that Unducted fan engine can eliminate the need of gearbox. I would like to know how is it done?

Thank you

4 replies: All unread, jump to last
 
User currently offlineAesma From France, joined Nov 2009, 6530 posts, RR: 9
Reply 1, posted (1 year 7 months 1 week 3 days 1 hour ago) and read 2920 times:

You're talking about a specific engine, the General Electric's GE36 Unducted Fan.

As found on wikipedia : it has a novel direct drive arrangement, where the reduction gearbox is replaced by a low-speed seven-stage free turbine. The turbine rotors drive one propeller, while the other propeller is connected to the free turbine stators and rotates in the opposite direction. So, in effect, the power turbine has 14 stages.

I don't know if current efforts into unducted fans still use that concept.



New Technology is the name we give to stuff that doesn't work yet. Douglas Adams
User currently offlineprebennorholm From Denmark, joined Mar 2000, 6387 posts, RR: 54
Reply 2, posted (1 year 7 months 1 week 2 days 19 hours ago) and read 2799 times:

The GE36 was (as far as I know) the only attempt to make an ungeared UDF. Only one engine was made as a concept demonstrator on a contract with NASA.

In principle it was a separate unit added on the back of an off the shelf GE F-404 engine from an F/A-18 Super Hornet fighter. It was used as gas generator to power the aft UDF unit.

The back unit first split the gas into a wide annular gas flow so the UDF turbines could get a proper moment arm to pull the fan blades at the rather low speed, not much over 1500 rpm.

The UDF unit had two turbines each with 7 stages. One was a quite normal turbine pulling one fan in one direction.

The other 7 stages turbine "replaced" the stator vanes. The turbine blades were mounted on their outer ends inside a "barrel" which rotated in the opposite direction and pulled the other fan.

Mechanically it was an immensely complicated thing, and just the lubricating system was a nightmare to develop. How they also made variable pitch on all 16 fan blades is beyond me. But they did.

It had the potential to produce a more lightweight unit with high efficiency by eliminating the gearbox, and by eliminating the drag from separate stator vanes.

The single GE36 was optimized for speeds up to Mach 0.72, and a reviced version good for Mach 0.80 was planned.

The project was discontinued due to noise related problems.

The front fan on the Mach 0.72 version would be largely subsonic, but due to the accelerated air by the front fan the aft fan tips were supersonic. On a Mach 0.80 version the supersonic noise would have been somewhat more of a problem.



Always keep your number of landings equal to your number of take-offs, Preben Norholm
User currently offlineLMP737 From , joined Dec 1969, posts, RR:
Reply 3, posted (1 year 7 months 1 week 2 days 3 hours ago) and read 2593 times:

I used to work with some people who were on the UDF program for MD. From what they told me it was good on the gas. However the interior noise and vibration was awful.

User currently offlinejetlife2 From United States of America, joined Jul 2006, 221 posts, RR: 25
Reply 4, posted (1 year 7 months 1 week 2 days 2 hours ago) and read 2576 times:

Current studies on open rotors are looking at both geared and ungeared configurations.

The GE36 met all its goals for performance. At the time it was expected that fuel prices would continue to rise and that fuel burn reduction would be a huge incentive to produce new aircraft with this configuration. But that did not come to pass. The main reason for dropping the program was the lack of a convincing cost-benefit trade in the face of low fuel price.

Since then the noise issues have been solved. Open rotor configurations are at the front of the pack for the next generation of narrow bodies (2025+).


Top Of Page
Forum Index

Reply To This Topic Unducted Fan Engine
Username:
No username? Sign up now!
Password: 


Forgot Password? Be reminded.
Remember me on this computer (uses cookies)
  • Tech/Ops related posts only!
  • Not Tech/Ops related? Use the other forums
  • No adverts of any kind. This includes web pages.
  • No hostile language or criticizing of others.
  • Do not post copyright protected material.
  • Use relevant and describing topics.
  • Check if your post already been discussed.
  • Check your spelling!
  • DETAILED RULES
Add Images Add SmiliesPosting Help

Please check your spelling (press "Check Spelling" above)


Similar topics:More similar topics...
Unducted Fan Should Have Been Used! posted Wed Sep 14 2005 00:19:06 by NWDC10
Unducted Fan? posted Sat Aug 23 2003 02:08:42 by AvroArrow
Engine Fan Spin Direction Question posted Sun Jul 26 2009 13:43:51 by Boacvc10
757 Engine Fan Blade Speed posted Sat Dec 27 2008 15:09:08 by Iowaman
Interior Noise And Engine/ Fan Sizes posted Thu Mar 20 2008 18:58:26 by KochamLOT
TurboFan Engine: Fan Operating In Reverse? posted Thu Nov 15 2007 11:24:54 by Guessbb
Fan Blades In #2 Engine Of 3 Engine A/c? posted Sun Aug 8 2004 00:15:10 by WakeTurbulence
GE CF6 80E1 Engine Fan Specs posted Fri May 28 2004 21:31:00 by BWIA330
"One-Piece" Jet Engine Fan? posted Fri Dec 14 2001 21:08:06 by Mr Spaceman
Aircraft Engine posted Thu Dec 20 2012 03:37:16 by surajit001

Sponsor Message:
Printer friendly format