cloudboy
Posts: 972
Joined: Mon Jan 26, 2004 12:38 pm

Ducted PropFans

Tue Jun 05, 2007 11:11 am

With fuel prices going up, fuel efficiency is growing more and more important. In the 80s and 90s there were experiments with Propfans. But so far, only Russia has put one into production. As I understand it, noise and prop inefficiency were two major problems.

Has anyone experimented with putting a shroud around the blades of a Propfan, essentially creating a ultra-high bypass turbofan? Instead of using conventional fan blades, it would use airfoil shaped blades as in a conventional prop. In particular, I am wondering if this would have an impact on the smaller end of the jet range.
"Six becoming three doesn't create more Americans that want to fly." -Adam Pilarski
 
Flight209
Posts: 49
Joined: Sun May 21, 2006 8:07 am

RE: Ducted PropFans

Tue Jun 05, 2007 11:49 am

I have a roughly twenty-year-old coffee-table book about commercial aircraft, and one section of the book dealt with both propfans and ultra-high-bypass versions of traditional ducted turbofans. The propfan got much more attention in the book, as I'm sure it did in real-life aviation industry circles, but the writers managed to include one photo of an experimental UHB ducted turbofan engine (a Rolls-Royce project called the ContraFan, I believe) and a side-profile diagram for a UHB ducted turbofan engine right below a similar one for a propfan engine.

Frankly, IMO, based on both the photo and the diagram, the UHB ducted turbofans under development back in the mid 1980s would have been rather awkward, inelegant, and just plain ugly in layout, particularly since those engines were slated to have the same "pusher" fan configurations as the propfans then being devised for such stillborn aircraft as the Boeing 7J7 and the McDonnell-Douglas MD-91X, MD-92X, and MD-94X. FWIW, however, the authors of that book believed that UHB ducted turbofans would have had at least one edge over propfans; the authors thought that UHB ducted turbofans were better suited to longhaul aircraft than were propfans.
I may question your opinion, but I'll never question your right to it.
 
Devilfish
Posts: 5181
Joined: Tue Jan 24, 2006 7:52 am

RE: Ducted PropFans

Tue Jun 05, 2007 1:16 pm

Quoting Cloudboy (Thread starter):
Has anyone experimented with putting a shroud around the blades of a Propfan



Quoting Flight209 (Reply 1):
the UHB ducted turbofans under development back in the mid 1980s would have been rather awkward, inelegant, and just plain ugly in layout, particularly since those engines were slated to have the same "pusher" fan configurations

Something like this?.....


View Large View Medium
Click here for bigger photo!

Photo © Jorgos Tsambikakis



Or these?.....

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Click here for bigger photo!

Photo © Frank C. Duarte Jr.


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Click here for bigger photo!

Photo © AirNikon
View Large View Medium
Click here for bigger photo!

Photo © Flemming K. Fogh



See here.....

http://www.flightglobal.com/articles...-set-for-first-flight-in-june.html
X-49 Speedhawk - Poor Man's Osprey? (by DEVILFISH May 31 2007 in Tech Ops)

Old thread here.....
What Happened To The 7J7/Propfans? (by Flyinglen Aug 30 1999 in Civil Aviation)
"Everyone is entitled to my opinion." - Garfield
 
Flight209
Posts: 49
Joined: Sun May 21, 2006 8:07 am

RE: Ducted PropFans

Tue Jun 05, 2007 1:51 pm

A drawing of a Rolls-Royce ContraFan is included on this page:

http://members.aol.com/sciszek/propfan.htm

Just scroll down to Section 3.4, "Ducted Propfan", and you'll see what I mean.

(BTW, I'm not the writer of that paper, nor am I affiliated with the writer in any way, shape, or form.)
I may question your opinion, but I'll never question your right to it.
 
Devilfish
Posts: 5181
Joined: Tue Jan 24, 2006 7:52 am

RE: Ducted PropFans

Tue Jun 12, 2007 6:28 am

Here's a new, related article.....

http://www.flightglobal.com/articles...whatever-happened-to-propfans.html

Suggest moving to Tech/Ops.
"Everyone is entitled to my opinion." - Garfield
 
AirframeAS
Posts: 9811
Joined: Thu Feb 05, 2004 3:56 pm

RE: Ducted PropFans

Tue Jun 12, 2007 6:36 am

Quoting Cloudboy (Thread starter):

May I make a kind suggestion? Post this in the Tech/Ops forum. You'll get better answers there.
A Safe Flight Begins With Quality Maintenance On The Ground.
 
cloudboy
Posts: 972
Joined: Mon Jan 26, 2004 12:38 pm

RE: Ducted PropFans

Tue Jun 12, 2007 10:03 am

Alas, they would not be in a language I would be able to understand.
"Six becoming three doesn't create more Americans that want to fly." -Adam Pilarski
 
AirframeAS
Posts: 9811
Joined: Thu Feb 05, 2004 3:56 pm

RE: Ducted PropFans

Tue Jun 12, 2007 10:18 am

Quoting Cloudboy (Reply 6):
Alas, they would not be in a language I would be able to understand.

Not to worry, I don't think they would bombard you with not understanding that. No question is a stupid question over there. This is exactly what they teach us in A&P school. If you dont understand something no matter how stupid it sounds, ASK!  Smile
A Safe Flight Begins With Quality Maintenance On The Ground.

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