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Ducted PropFans  
User currently offlineCloudboy From United States of America, joined Jan 2004, 807 posts, RR: 0
Posted (7 years 1 month 3 weeks 4 days 21 hours ago) and read 3519 times:

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
7 replies: All unread, jump to last
 
User currently offlineFlight209 From United States of America, joined May 2006, 78 posts, RR: 0
Reply 1, posted (7 years 1 month 3 weeks 4 days 20 hours ago) and read 3472 times:

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.
User currently offlineDEVILFISH From Philippines, joined Jan 2006, 4781 posts, RR: 1
Reply 2, posted (7 years 1 month 3 weeks 4 days 19 hours ago) and read 3375 times:

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?.....

View Large View Medium
Click here for bigger photo!

Photo © Frank C. Duarte Jr.


View Large View Medium
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
User currently offlineFlight209 From United States of America, joined May 2006, 78 posts, RR: 0
Reply 3, posted (7 years 1 month 3 weeks 4 days 18 hours ago) and read 3321 times:

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.
User currently offlineDEVILFISH From Philippines, joined Jan 2006, 4781 posts, RR: 1
Reply 4, posted (7 years 1 month 2 weeks 5 days 1 hour ago) and read 3115 times:

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
User currently offlineAirframeAS From United States of America, joined Feb 2004, 14150 posts, RR: 24
Reply 5, posted (7 years 1 month 2 weeks 5 days 1 hour ago) and read 3100 times:

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.
User currently offlineCloudboy From United States of America, joined Jan 2004, 807 posts, RR: 0
Reply 6, posted (7 years 1 month 2 weeks 4 days 22 hours ago) and read 2999 times:

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
User currently offlineAirframeAS From United States of America, joined Feb 2004, 14150 posts, RR: 24
Reply 7, posted (7 years 1 month 2 weeks 4 days 22 hours ago) and read 2971 times:

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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What Happened To The 7J7/Propfans? posted Mon Aug 30 1999 00:08:41 by Flyinglen