View Full Version : Did this work?
touch&go
30th Oct 2005, 17:38
How did this work or was it a bad idea?
http://www.airliners.net/open.file?id=947367
A-FLOOR
30th Oct 2005, 17:45
Do a quick search on google for "unducted fan" and all will be revealed ;)
Reportedly such a system could save as much as 40% in terms of fuel burn.
Although this seems much, it was dwarfed by its reversed cousin the "unfanned duct", which saved the other 60%. The UFD is seen here (http://www.hauke.notsitz.info/frankreich_10.JPG), featured on an experimental Dassault Mercure. :p
barit1
30th Oct 2005, 19:06
The photo shows a MD-80 with the UDF on each side. GE also had a 727-100 testbed with only one UDF installed.
'twas designed at a time when fuel costs were in decline from 1980 highs. It showed great promise, but no airline wanted to take on the technical risk of much new technology, with cheaper fuel on the (then) horizon. Cabin noise was also an issue.
Alternative translation (http://www.udfinc.com/) of UDF
JustaFew
30th Oct 2005, 20:12
In the late 70s/early 80s, there resided at Shoreham airport a BN2 Islander (GFANS) which had ducted fans. Never seen anything like it since.
Volume
1st Nov 2005, 05:04
How did this work
Fuel economy was as predicted, but the noise was enormous. To reduce it a little bit, the number of blades is different in the two stages. It was still able to remove the paint from the VTP within a few flights (!)
One of the killers was the blade containment problem.
enicalyth
1st Nov 2005, 11:17
A-Floor you made me laugh, the unfanned duct indeed.
Seriously. Bad idea.
Just as a harp is a nude piano, the UDF is, if not nude, at least a topless jet and is going to have every vice that high speed prop aircraft have and none of the virtues of its lower speed siblings because “ye cannae change the laws of physics”.
Whenever the topic of the UDF arises (and it does every other month) I am reminded of Professor Richard Shevell, of DC-9 and DC-10 fame. When asked where he “saw” the propfan he would reply “On somebody else’s airplane!”
He also used to say that if any of his first year students could not utterly condemn the project in 100 words or less he would see them off to another university.
Dentists and paint sprayers thought it wonderful. My late father who had something to do with it called it the McGonagal Doneless Propbang. He was being kind.
too much toulouse
1st Nov 2005, 14:03
Gentlemen
When engines consumed 1 lb of fuel per hour per lb of thrust then a 40% reduction would bring this down to 0.6lb which we have today, have we not and better?
Ah yes! Blade containment? I suggest we enclose a very large fan or even tandem fans in a housing. How big? Well yes I would put them on the wing not the tail and so the critical size is determined by having no damage to the engine should the nosewheel collapse. Maybe 9-10 times the amount of air can pass through the ducted fans than the core.
Fuel efficiency? Well instead of dwelling in the past read NASA NOW about the Ultra Efficient Engine Technology Program. But meanwhile, my idea, I think perhaps we will not call it the ducted fan. I like the name turbofan. I shall patent it. Oh yes you keep asking about fuel efficiency. Very well. Does 0.53 lb per lb hour suit you? and no no no. Taking the covers off does not reward you with an immediate 40% improvement.
She is very quiet and vibration free this new-fangled idea of mine. Residents near aeroports are very happy. Bean counters delighted. Engineers in fits of delirium. Passengers choose it
My friends all of you the unducted fan is dead, why have you a fascination?
A-FLOOR
1st Nov 2005, 14:22
toulouse: From an engineering point of view it's always interesting to look at things from the past that didn't work or didn't succeed for reasons other than those purely technical, even if it's just to prevent youreself from trying to reinvent the wheel.
Also, remember that the knowledge gained learning from someone elses mistakes is more often than not more valuable than knowledge gained from someone elses success :ok: