Unducted Jet Engines.....comming back?

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Doc
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Unducted Jet Engines.....comming back?

Post by Doc »

What's the bet, with the price of fuel, we see these puppies making a come back? Granted, they never really got past the test stage the last time around...but I'll bet you see them trying to make these things a reality in the not so distant future....

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Doc
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Re: Unducted Jet Engines.....comming back?

Post by Doc »

Next time around, they'll use a high bypass fan jet engine, rather than the skinny things bolted on this DC9.

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Lost in Saigon
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Re: Unducted Jet Engines.....comming back?

Post by Lost in Saigon »

Doc wrote:Next time around, they'll use a high bypass fan jet engine, rather than the skinny things bolted on this DC9.
Do realize that those blades you see at the back replace the large fan blades of a high bypass fan jet? That is why it is called a "Unducted Fan Engine" or "Propfan".
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Re: Unducted Jet Engines.....comming back?

Post by x-wind »

Im thinking (and hoping) the hydrogen age is coming.
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small penguin
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Re: Unducted Jet Engines.....comming back?

Post by small penguin »

For the un-initiated please?
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Re: Unducted Jet Engines.....comming back?

Post by AuxBatOn »

x-wind wrote:Im thinking (and hoping) the hydrogen age is coming.
I can't see that happening. Hydrogen is very hard to carry efficiently and would be very hard to store at an airport (or in an airplane for that matter) in its liquid form (the most desirable form I would say). Plus, where can you find hydrogen in nature (pure H2)? Not on Earth. Making it by electrolysis is very inneficient and would cost probably much more than fuel.

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Re: Unducted Jet Engines.....comming back?

Post by Mode C »

small penguin wrote:For the un-initiated please?
http://en.wikipedia.org/wiki/Unducted_fan
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pika
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Re: Unducted Jet Engines.....comming back?

Post by pika »

Only place you will see the unducted fan is a museum. Pulse jet is the future for now.
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Re: Unducted Jet Engines.....comming back?

Post by xsbank »

Au contraire, the next step in engines is the geared fan engine, like that proposed for the 'C' series. The fan is geared to the most efficient speed and the corresponding power section can be much smaller. Very quiet, too. All that moaning that you hear from an angry 'Bus will be a thing of the past <sigh>.

I did a paper on the UDF engine for my Transportation Economics class, when Doc was in diapers; the biggest drawback was noise. They were quite efficient but they were very vulnerable to FOD and if there was a catastrophic there was no shroud to contain the blades, which would do severe damage to the tail of the a/c or to entire neighbourhoods on the ground! Complexity is a problem, too, as the blades would have to be reversible.

If you have a high-bypass engine, say 6:1, you have '1' portion of the air feeding the actual engine and '6' providing the thrust. Not much of that '1' escapes the engine as thrust as its busy running the compressor and and the low-pressure turbine that runs the fan with a shaft. If you were running a set of blades attached to the low-pressure fan, I doubt if there would be enough thrust to run a ducted fan too, unless you just stuck blades all over it like a corn cob! See drawbacks above.
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Re: Unducted Jet Engines.....comming back?

Post by teacher »

I'm sure everyone remembers Easyjet's Ecojet from last year....

http://www.flightglobal.com/articles/20 ... cojet.html
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Re: Unducted Jet Engines.....comming back?

Post by alctel »

AuxBatOn wrote:
x-wind wrote:Im thinking (and hoping) the hydrogen age is coming.
I can't see that happening. Hydrogen is very hard to carry efficiently and would be very hard to store at an airport (or in an airplane for that matter) in its liquid form (the most desirable form I would say). Plus, where can you find hydrogen in nature (pure H2)? Not on Earth. Making it by electrolysis is very inneficient and would cost probably much more than fuel.

AuxBatOn

I know a guy who is working on Hydrogen Fuel cells and they have *just* (as in the last few weeks) perfected a method to seperate water for extremely cheap (not using electrolysis). He wouldn't give me anymore details though. However I don't think they still have an efficent and safe way to carry enough on an airplane for long distance flight (or a short one for that matter).

Also those unducted jet engines look completely rad.
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Re: Unducted Jet Engines.....comming back?

Post by ragbagflyer »

alctel wrote: I know a guy who is working on Hydrogen Fuel cells and they have *just* (as in the last few weeks) perfected a method to seperate water for extremely cheap (not using electrolysis). He wouldn't give me anymore details though. However I don't think they still have an efficent and safe way to carry enough on an airplane for long distance flight (or a short one for that matter).

Also those unducted jet engines look completely rad.
Sweet, can you ask him to make a briefcase sized cold fusion reactor too?
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Re: Unducted Jet Engines.....comming back?

Post by THEICEMAN »

Im thinking (and hoping) the hydrogen age is coming.
Fossil fuels will be available for airplanes in the long run. If anything...cars, trucks & trains will have to run on alternative energy sources.

Priority will/should be given to commercial ships & airplanes, in order to keep the economy going.
If we can achieve this within the not so distant future, then this will be good news.
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Re: Unducted Jet Engines.....comming back?

Post by KAG »

I have seen pictures or read of those type of engines for over 10 years. I can't see it happening. What about the PDE engine, heard lots of hype 3-4 years ago, and still nothing.
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pika
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Re: Unducted Jet Engines.....comming back?

Post by pika »

Perhaps we should define "future".
B787 has engines, A350 has engines and the C Series has engines.
No unducted fans to be seen.
Military aviation has always been the future.
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Re: Unducted Jet Engines.....comming back?

Post by iflyforpie »

pika wrote: Military aviation has always been the future.
Not quite. Turbofans were introduced in the civilian world. Also single stage high-bypass turbo fans and wide chord fan blades.

I seriously doubt the UDF will get any farther than it did in the 80s due to the huge technical problems that bogged it down in the first place.


If the airlines really want to save fuel, they will switch to turboprop engines which will add only marginally to the total travel time (as much time is taken by security procedures and boarding/deboarding) and jets now are flying on average 100MPH slower than they were in the 1960s due to their draggy high bypass ratio engines and desire to stay as far out of the transonic regime as they can.
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Re: Unducted Jet Engines.....comming back?

Post by AuxBatOn »

THEICEMAN: actually fuel supply will be given to militaries before it is given to commercial aviation/transport industries.
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Re: Unducted Jet Engines.....comming back?

Post by Lommer »

Agreed, the UDF is not gonna happen soon. As for Pulse-jets and PDEs - gimme a break; that's ancient technology (well, pulsejets anyways) that has only seen a recent renaissance because they're easy for hobbyists to build, run, and experiment with. When scaled up to commercial applications the numbers just aren't there.

I, unlike many others, think that hydrogen airplanes will happen given some time. The initiative to tackle the technical storage hurdles is growing, and the benefits are clear: hydrogen has the greatest gravimetric energy density of any fuel we know, fuel cells powering electric motors have an extraordinary energy conversion efficiency and are very quiet, and the primary method of producing commercial hydrogen (cracking natural gas) relies on a currently-under-valued fuel and successfully removes lots of pollutants from the upper atmosphere. I'm not denying that there's serious hurdles, even without considering the regulatory ones, but I think it's pretty promising overall.

Just my $0.02
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Re: Unducted Jet Engines.....comming back?

Post by x-wind »

[quote="AuxBatOn"] [quote="x-wind"]Im thinking (and hoping) the hydrogen age is coming.[/quote]

I can't see that happening. Hydrogen is very hard to carry efficiently and would be very hard to store at an airport (or in an airplane for that matter) in its liquid form (the most desirable form I would say). Plus, where can you find hydrogen in nature (pure H2)? Not on Earth. Making it by electrolysis is very inefficient and would cost probably much more than fuel.

AuxBatOn [/quote]

Desperate times will call for desperate measures. I'm sure if we worked on it hard enough the tanks could be made lighter. As for electrolysis- Nuclear power?? :shock:

http://www.cbc.ca/ideas/media/2008/hydr ... sode-1.mp3 - This is a whole radio program.

http://www.youtube.com/watch?v=lJVzySk0Pks :) - this is a short movie.
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