Posted: Tue Apr 29, 2008 7:41 am Post subject: Re: Aviation - new turboprop is 30% more efficient
I've been waiting for GE's contra-rotating engine to be reintroduced. This offered something like 30% reduction in fuel consumption IIRC. I"d bet dollars to donuts that we'll hear something on it soon.
Joined: Apr 28, 2005 Posts: 3270 Location: West shore Lake Eire, MI, USA
Posted: Tue Apr 29, 2008 11:44 am Post subject: Re: Aviation - new turboprop is 30% more efficient
I also wonder how much more efficient Tubercles will make more conventional turboprop and piston prop aircraft?
http://www.peakoil.com/fortopic37467-0.html _________________ Oxygen: - An intensely habit-forming accumulative toxic substance. As little
as one breath is known to produce a life-long addiction to the gas, which addiction invariably ends in death.--Isaac Asimov
Posted: Fri May 09, 2008 12:28 am Post subject: Re: Aviation - new turboprop is 30% more efficient
just thought I'd point out that a machine can often be designed to work most efficently in a given environment and often cost is a major factor why some machines are built in great numbers and why some machine designs kinda fade away...
those not familiar with airplanes, might wonder why jets dominated after WW II, and why planes with prop engines faded away.
Well after WWII jet engines took over from piston prop planes, because they were more economical from a maintenance stand point.
the problem with an internal combustion engine, is it does not scale too well. If ya built a radial engine big enough to power something like a 747, the engine would be so big and complex, heavy and unreliable, that it would not be worth doing.
Another reason prop planes are limited is because ya just can't drive a prop ever faster, this is because props loose effiency when the tips of the propeller go supersonic (all kinds of interesting physics occurs when things go faster than the speed of sound)
The jet engine, is pretty simple in theory, basically ya compress the air with a series of turbines, add fuel which is ignited at the end to produce thrust.
a jet engine is less complex than piston engine, and lasts much longer before failure,so that is why jet engines exist (not because of the speed difference), which is what lots of people not familiar with airplanes think. The major drawback to jet engines is they are not very fuel efficent at lower altitudes, becase they make thrust by moving a small amount of air very quickly. When oil was cheap, the a turbojet engine was very economical to operate, because it lasted a very long time in operational use, with respect to a piston engine.
Its basic physics to see that its lots more efficent to move lots of air more slowly than it is to move a small amount of air quickly to produce thrust, and that idea combined with the fact that it takes time to climb to altitude, so for shorter distances, aircraft makers, use a turbo prop design. Basically a turboprop is a jet engine but they adds a prop at the end of shaft
There is a variation of a turboprop engine used at higher altitudes, where jetliners traditionally fly between 35,000 ft and 42,000 (this is the altitude where jets operate most efficently), and this engine is called a turbofan. Basically there is a duct around one really large set of compressor blades.
In engineering there are always tradeoffs, for example an SUV is never going to handle as well as a car, becasue the center of gravity in an SUV is much higher than it is in a car, so that is why SUVs are more prone to tip over while in a turn.
One thing I just read, that efficent geeks might find interesting is an article about a new jet engine design, optimized for low and slow flight that is optimized for altitudes of about 15,000 ft and cruise speeds of about 300 MPH for small general aviation airplanes.
http://www.airspacemag.com/flight-today/16047832.html _________________ "I'm 100% sure that unsustainable conspicuous consumption of natural basic resources will eventually lead to a proverbial hell on earth for those people who get stuck with the mismanagement mess of mankind not being stewards of the environment!"
Posted: Fri May 09, 2008 12:40 am Post subject: Re: Aviation - new turboprop is 30% more efficient
Frank wrote:
I've been waiting for GE's contra-rotating engine to be reintroduced. This offered something like 30% reduction in fuel consumption IIRC. I"d bet dollars to donuts that we'll hear something on it soon.
bet ya won't!
the problems are two fold with this design, first if prop efficeny at jetliner speeds and altitude was not as efficent as designers had hoped, and second the designs tried on some of the test bed aircraft had major noise problems which cause metal fatigue near the nacelles, etc...
remember reading some proposals for a duct to try and dampen the noise of the contra-rotating props, but then the problem becomes one of really tight tolerances for huge props, so that IMHO along with major advances in computional fluid dynamics is why turbofans with ever increasing bypass ratios is the way things are go to go... _________________ "I'm 100% sure that unsustainable conspicuous consumption of natural basic resources will eventually lead to a proverbial hell on earth for those people who get stuck with the mismanagement mess of mankind not being stewards of the environment!"
Posted: Fri May 09, 2008 2:06 am Post subject: Re: Aviation - new turboprop is 30% more efficient
smallpoxgirl wrote:
emersonbiggins wrote:
-'cept it's a turboprop.
The regression of civilization has begun, in earnest.
I'm not sure how you conclude that a turboprop is a regression from pure jet engines. Seems to me the trade off is in wasting a lot of energy with a jet in order to go a little faster, or using that energy much more efficiently to turn a prop. I suppose it's a regression if you see progress as being about trying to maximize waste. Its a regression in the same way that the Toyota was a regression over a Buick in the 70's.
I ride a q400 back and forth to Seattle every week, and it's a very nice little plane. Actually has bigger seats than a 757. It's a bit noisy, especially in rows 7 and 8, but seriously, noise canceling headphones are cheap compared to airfare.
I think EB is right, it is a change being brought about by hitting a practical limit. It would be hard to go faster, cheaper, and waste more energy than we did last year.
So, turbo props eh? Aight, when do they replace automobiles? Why not get rid of domestic airlines all together and get us some a 'dem maglevs like they have in France and Japan. Now you get 300 kph safely on the ground and you power the whole thing with Hoover Dam.
The airlines are really in a bind. I do not see a bright long term future for that industry in light of peak oil. _________________ I return to you now at the turning of the tide.
Posted: Fri May 09, 2008 2:11 am Post subject: Re: Aviation - new turboprop is 30% more efficient
phaster wrote:
just thought I'd point out that a machine can often be designed to work most efficently in a given environment and often cost is a major factor why some machines are built in great numbers and why some machine designs kinda fade away...
those not familiar with airplanes, might wonder why jets dominated after WW II, and why planes with prop engines faded away.
Well after WWII jet engines took over from piston prop planes, because they were more economical from a maintenance stand point.
the problem with an internal combustion engine, is it does not scale too well. If ya built a radial engine big enough to power something like a 747, the engine would be so big and complex, heavy and unreliable, that it would not be worth doing.
Another reason prop planes are limited is because ya just can't drive a prop ever faster, this is because props loose effiency when the tips of the propeller go supersonic (all kinds of interesting physics occurs when things go faster than the speed of sound)
The jet engine, is pretty simple in theory, basically ya compress the air with a series of turbines, add fuel which is ignited at the end to produce thrust.
a jet engine is less complex than piston engine, and lasts much longer before failure,so that is why jet engines exist (not because of the speed difference), which is what lots of people not familiar with airplanes think. The major drawback to jet engines is they are not very fuel efficent at lower altitudes, becase they make thrust by moving a small amount of air very quickly. When oil was cheap, the a turbojet engine was very economical to operate, because it lasted a very long time in operational use, with respect to a piston engine.
Its basic physics to see that its lots more efficent to move lots of air more slowly than it is to move a small amount of air quickly to produce thrust, and that idea combined with the fact that it takes time to climb to altitude, so for shorter distances, aircraft makers, use a turbo prop design. Basically a turboprop is a jet engine but they adds a prop at the end of shaft
There is a variation of a turboprop engine used at higher altitudes, where jetliners traditionally fly between 35,000 ft and 42,000 (this is the altitude where jets operate most efficently), and this engine is called a turbofan. Basically there is a duct around one really large set of compressor blades.
In engineering there are always tradeoffs, for example an SUV is never going to handle as well as a car, becasue the center of gravity in an SUV is much higher than it is in a car, so that is why SUVs are more prone to tip over while in a turn.
One thing I just read, that efficent geeks might find interesting is an article about a new jet engine design, optimized for low and slow flight that is optimized for altitudes of about 15,000 ft and cruise speeds of about 300 MPH for small general aviation airplanes.
Joined: Apr 28, 2005 Posts: 3270 Location: West shore Lake Eire, MI, USA
Posted: Fri May 09, 2008 5:53 am Post subject: Re: Aviation - new turboprop is 30% more efficient
phaster wrote:
One thing I just read, that efficent geeks might find interesting is an article about a new jet engine design, optimized for low and slow flight that is optimized for altitudes of about 15,000 ft and cruise speeds of about 300 MPH for small general aviation airplanes.
Its a nice dream, but with $120.00 oil I do not beleive it will ever become a reality. I beleive general aviation will soon be a thing of the past as only megacorps and the governments will be able to afford commercial fuel. Some might keep flying with home produced biofuels, but I do not see them being a large factor in the future. _________________ Oxygen: - An intensely habit-forming accumulative toxic substance. As little
as one breath is known to produce a life-long addiction to the gas, which addiction invariably ends in death.--Isaac Asimov
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