h a l f b a k e r yWhat's a nice idea like yours doing in a place like this?
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Chances are, you've heard of ion wind devices. Some are used as "lifters," which can hover above the ground. Others are sold as ineffective air purifiers like the "Ionic Breeze Quadra." All move air.
Then there are vaneless ion-wind turbines, which use the same principle in reverse to harness
wind energy. cowtown posted the extremely-cool idea [see link1], and it turned out to actually be baked!
Now, my contribution: Put these two devices in series, with a combustion chamber in between. We have a device in which air flows through a compressor, then a combustor, and then a turbine. Sound familiar? It's a jet engine!!
In a conventional jet engine, a mechanical turbine powers a mechanical compressor; power is transmitted mechanically by a rotating shaft. In this jet engine, an electrical turbine powers an electrical compressor, and power is transmitted electrically via wires.
This device could be used either to generate thrust, or to generate high-voltage DC. Coupled to an inverter, it could be used to generate the household AC.
Without carefully-machined parts spinning at tens of thousands of RPMs, I would expect these to be significantly cheaper to produce than existing jet engines.
There are some problems to be overcome, however. The biggest is that most existing ion wind devices do not generate a great deal of thrust - more of a gentle breeze than the blast you get from a centrifical compressor. But I think that's solvable - perhaps by putting a great many ion wind stages in series. There are other approaches too, which may increase performance [see link2].
Well, that ought to cover just about everything. So what do you think?
Halfbakery: Vane-less Ion Wind Turbine
http://www.halfbake...on_20Wind_20Turbine
cowtown's great idea. [TerranFury, Oct 04 2004, last modified Oct 05 2004]
Blaze Labs: Lifters
http://www.blazelabs.com/l-intro.asp
Lifter information, without appeals to "electrogravatics" and other pseudoscience! [TerranFury, Oct 04 2004, last modified Oct 21 2004]
Dragonfly Research
http://www.dragonfl...nts/Experiments.asp
Some experiments with different wire gauges, voltages, air flow etc. [tiromancer, Jan 04 2005]
Page about "lifters"
http://jnaudin.free.fr/lifters/main.htm
the website is a bit out there, but there's a lot of good pictures and links [tiromancer, Jan 04 2005]
Low-pressure ramjet ion thruster
[MB]'s idea, mentioned in my anno. [notexactly, Jan 14 2016]
[link]
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I have no clue if this is feasible, but it sure sounds good. + |
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Physics is against you. What you need for thrust is momentum of the exhaust p=m*v. To get that momentum you have to put in energy E=m*v^2. As you see momentum (thrust) is proportional to speed, but energy is proportinal to the square of speed. A drive that gets thrust from little mass at high speed is therefor highly inefficient. |
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Ion drives are competitive in space where available mass is expensive (carried up from earth), but solar energy is free. On earth they won't ever be competitive. |
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Thanks for the criticism, kbecker, but I'm not so sure about some of your conclusions. Tell me what you think... |
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Space ion drives eject small amounts of propellant at high velocities; I agree that this is inefficient. |
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Ion breeze devices, however, do not do this, as far as I know. I was under the impression that they generate just what the name implies: A breeze. They move a relatively large volume of air at rather low velocities. If anything, I thought they'd be TOO slow, and our goal to make a workable gas turbine would be to INCREASE the velocities/pressures. |
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Also, it's fairly easy to trade velocity for mass flux when we're working in the atmosphere, if for some reason we need to. That's exactly what a jet-pump does. It injects a small high-velocity jet into a larger stream, which is accelerated by viscous effects. The net effect is a lower-velocity stream with a higher mass flux. So if for some reason we had the problem of too much velocity and too little mass flux, we could easily increase efficiency by doing just this. This is what thrust augmentors on pulsejets do. |
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First, both of you need to know that to call low mass with high velocity 'inefficient' would be wrong, 'ineffective' would be a better word. Ion drives, or anything with high velocity, low mass gives a very efficient change in momentum with the energy and mass used; however, the thrust is low, but in space that is okay.
Now as for the ion compressor, the real questions to ask are, how well do all these ion wind generators work when the air is already moving? Will it take move power to charge the air when it is already moving at a higher speed? How does pressure affect things, last I checked plasma (ionized gas) forms easier in lower pressures. Turbo jets runs by compressing air, combusting fuel further increasing the pressure, then the pressurized air is passed through a nozzle converting the pressure into velocity. And another thing, ionized gases don’t combust the same way normal air does.
I think the idea is cool, and might have merit, but not like this. |
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Ian Donovan
BS Aerospace Engineering |
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I like this idea a lot, but I'm going to avoid giving it a bun because I doubt it would work well with current technology. On the other hand, I will not give it a fish bone either because I think this idea has a lot of potential if the right advancements were made. |
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The concept of a jet engine with no moving parts that can operate from zero airspeed up is a very appealing idea. You might say that this could be modified to make an ion-assisted ramjet. How does the term "electroramjet" sound? In principle, if you could use this engine to reach sufficient airspeed, you could turn off the ionizing components and allow it to fly like a standard ramjet. |
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Unfortunately, I think this engine would be severely handicapped by efficiency. I don't know how the efficiency of an Ionic Breeze compares to that of a standard electric fan. If I were to hazard a guess, I'd say that the Ionic Breeze is far less efficient. In something like the forementioned device, the percentage of molecules of air that are actually ionized is probably very small. The non-ionized molecules could only be moved by the Ionic Breeze by collision with ionized molecules or by the vacuum formed when ionized molecules are moved. In a standard fan, ionization doesn't matter; any molecules in the way of the fan blades get pushed. |
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However, in the future some method of greatly improving the efficiency of such devices may be discovered. The development of room-temperature superconductors would probably help to an extent. Perhaps electrical arcs could be used to ionize the air directly. |
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//E=m*v^2//
sp. "E=m*v^2 / 2" |
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// How does pressure affect things, last I checked plasma
(ionized gas) forms easier in lower pressures. Turbo jets
runs by compressing air, combusting fuel further
increasing the pressure, then the pressurized air is
passed through a nozzle converting the pressure into
velocity. // |
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And then it goes through the turbine, either aerodynamic
or electroaerodynamic. But it's already a plasma by
virtue of being on fire, so that's not an issue. |
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// And another thing, ionized gases don’t combust the
same way normal air does. // |
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Air emitted from a 'lifter' is neutral, so no issue. |
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// Unfortunately, I think this engine would be severely
handicapped by efficiency. I don't know how the
efficiency of an Ionic Breeze compares to that of a
standard electric fan. If I were to hazard a guess, I'd say
that the Ionic Breeze is far less efficient. // |
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[MaxwellBuchanan] surmises that they're very efficient
because there's nowhere else for the power to go: [link]. |
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