Cloudboy From United States of America, joined Jan 2004, 668 posts, RR: 0 Posted (5 years 11 months 3 weeks 1 day 21 hours ago) and read 2614 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
Flight209 From United States of America, joined May 2006, 78 posts, RR: 0 Reply 1, posted (5 years 11 months 3 weeks 1 day 20 hours ago) and read 2567 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.
DEVILFISH From Philippines, joined Jan 2006, 4427 posts, RR: 1 Reply 2, posted (5 years 11 months 3 weeks 1 day 18 hours ago) and read 2470 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
AirframeAS From United States of America, joined Feb 2004, 14150 posts, RR: 26 Reply 7, posted (5 years 11 months 2 weeks 1 day 21 hours ago) and read 2066 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!
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