Fusionfire
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Suitable material for holding a plasma
Hello folks,
I am trying to assess the budget of how much it would cost to build the ducting of a high temperature plasma generator.
The basic idea is to start with an off-the-shelf propane torch to get around 1600-1800C (accounting for losses) and inject vaporised lithium and boron
into the airflow.
Lithium metal which is cheaper to get than boron will initially react with oxygen, producing an oxygen deficient atmosphere while yielding 43.13 kJ/g
in accordance to:
4Li + O2 → 2Li2O ΔfH° = -598.73 kJ/mol
Subsequently powdered boron will be injected into the flow, reacting with nitrogen in an anaerobic flow while yielding 23.21 kJ/g, in accordance to:
2B + N2 → 2BN ΔfH° = -250.91 kJ/mol
Burning boron the entire time would be thermodynamically ideal but expensive.
A later design may use oxy-acetylene instead of propane/air.
So the design requirements are:
1) Melting point in excess of 3000C
2) Chemically stable to attack from elemental boron and lithium dusts/gases.
3) As sensitive equipment will be next to the plasma generator it is preferable that the duct walls are not thermally conductive (pretty much narrows
it down to the refractory ceramics and glasses).
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IrC
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Tantalum hafnium carbide is a ceramic with a melting point of 4215 C - the highest known. Good luck finding some. Or something on this page?
http://www.azom.com/article.aspx?ArticleID=5127
"Science is the belief in the ignorance of the experts" Richard Feynman
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AndersHoveland
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The plasma may still be highly corrosive to the walls, even below the melting point.
Sometimes plasmas are seeded with potassium compounds to lower the plasma temperatures.
I'm not saying let's go kill all the stupid people...I'm just saying lets remove all the warning labels and let the problem sort itself out.
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Wizzard
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Superconductive magnets. Or at least AlNiCo magnets (better heat tolerance). Plasmas are conductive, and if you can shape a very strong field, it will
flow along it (and not along the walls necessarily).
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watson.fawkes
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Quote: Originally posted by Fusionfire  | | I am trying to assess the budget of how much it would cost to build the ducting of a high temperature plasma generator. |
Why is it that you're seeking a chemically-generated plasma rather than a electrically-generated one? Your eventual goal could
greatly affect your engineering choices.
If all you want is the flame, use a large steel chamber and a high speed vacuum pump to evacuate the reaction products. You'll need to refrigerate the
structural elements, or at very least address where the heat goes.
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Fusionfire
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| Quote: Originally posted by watson.fawkes | | Quote: Originally posted by Fusionfire | | I am trying to assess the budget of how much it would cost to build the ducting of a high temperature plasma generator. |
Why is it that you're seeking a chemically-generated plasma rather than a electrically-generated one? Your eventual goal could
greatly affect your engineering choices.
If all you want is the flame, use a large steel chamber and a high speed vacuum pump to evacuate the reaction products. You'll need to refrigerate the
structural elements, or at very least address where the heat goes. |
Because most electrical energy you get off the grid is ultimately chemically generated (unless you live in certain areas like hydro-power rich Norway
or near nuclear reactor rich Japan).
Chemically generated plasmas are much more convenient, compact and portable  .
Boron has among the highest energy density of elements, too bad it is so expensive. Lithium has a more -ve oxidation enthalpy per gram of reactant
than even magnesium. I haven't done an exhaustive survey but:
4B + 3O2 → 2B2O3 ΔfH° = -1271.94 kJ/mol
Heat per gram of B = 58.83 kJ/g
2Mg + O2 → 2MgO ΔfH° = -601.24 kJ/mol
Heat per gram of Mg = 24.74 kJ/g
4Li + O2 → 2Li2O ΔfH° = -598.73 kJ/mol
Heat per gram of Li = 43.13 kJ/g
Problem with lithium is that is sucks burning in anaerobic conditions once the oxygen is depleted...
6Li + N2 → 2Li3N ΔfH° = -164.56 kJ/mol
Heat per gram of Li = 7.903 kJ/g
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watson.fawkes
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Frankly, by the time you deal with an oxygen tank (to get your temperature up and avoid heating argon),
chemical storage, metering devices, etc., you're not talking about a compact unit. Commercial plasma-based metallizing guns have small guns, but the
supporting gear requirements aren't small at all. I do expect that you'll get a more compact and portable unit using an engine-powered generator and a
few jerrycans of fuel.
Frankly, though, I feel you've dodged the question. You've talked about secondary properties (convenience, etc.) not about the primary purpose. What
do you want to do with the plasma, regardless of how it's sited or transported?
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Neil
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Have you looked at plasma furnace technology? They have a variety of ways of containing the plasma without using crazy materials, some such as cool
air vortex methods may be in reach of home science.
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Neil
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Have you looked at plasma furnace technology? They have a variety of ways of containing the plasma without using crazy materials, some such as cool
air vortex methods may be in reach of home science.
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metalresearcher
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What about an electric arc furnace using a welder from the hardware shop around the corner ? You will get temperatures over 3000oC this way. The arc
is a plasma which you can flush with argon gas.
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Fusionfire
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I want to inspect the augmentation of thrust on a test stand using powdered metal/metalloid fuels for afterburning, rather than JP8.
Which is why I am also asking about propane torch exhaust conditions. Some metal/metalloid fuels will also burn in the presence of water vapour or
carbon dioxide; 19% oxygen is also great.
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Sedit
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Magnetic bottles as they are so called is your best (only)option by far. There is no need to mess around with anything else because as your
experiments progress and temperatures become higher the ability to find suitable material will become impossible sooner or later. You may as well
start on the right path now before you have to back track down the road when you have already made forward progress.
Knowledge is useless to useless people...
"I see a lot of patterns in our behavior as a nation that parallel a lot of other historical processes. The fall of Rome, the fall of Germany — the
fall of the ruling country, the people who think they can do whatever they want without anybody else's consent. I've seen this story
before."~Maynard James Keenan
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Fusionfire
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| Quote: Originally posted by Sedit | | Magnetic bottles as they are so called is your best (only)option by far. There is no need to mess around with anything else because as your
experiments progress and temperatures become higher the ability to find suitable material will become impossible sooner or later. You may as well
start on the right path now before you have to back track down the road when you have already made forward progress. |
I have thought about that but don't you still need a good heat shield between the permanent or electromagnets to protect them from conductive,
convective or radiative heat?
It seems magnetic lensing or plasma filamentation approaches augment but do not replace high temperature refractories in plasma chambers.
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Neil
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A plasma spray gun?
Edit: I just noticed that it double posted up above, if some kind hearted admin would delete one of them I'd be grateful.
[Edited on 24-10-2011 by Neil]
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Sedit
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Thats funny Neil, What you just posted is what I do for a living yet our guns work slightly different except the 4000 gun which is exactly what you
posted.
Knowledge is useless to useless people...
"I see a lot of patterns in our behavior as a nation that parallel a lot of other historical processes. The fall of Rome, the fall of Germany — the
fall of the ruling country, the people who think they can do whatever they want without anybody else's consent. I've seen this story
before."~Maynard James Keenan
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Fusionfire
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Thanks Neil. But how will the above topology produce thrust augmentation by afterburning?
AIUI the afterburning has to be within the engine cavity to produce additional thrust by a pressure rise + faster ejected flow.
If the fuel is dumped outside the engine (e.g. "dump and burn") then it produces no thrust augmentation.
http://en.wikipedia.org/wiki/Fuel_dumping#Dump-and-burn
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Neil
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@Sedit Haha Ironic, You've got a wicked job.
@ fusionfire
Spray the fuel of choice into the engines exhaust gases, just replace a fuel nozzle with a plasma injector nozzle. A conventional plasma cutter with
some kind of venturi may even work - Ask Sedit!
There are lots patents pertaining to exactly this in SCRAM jet starting and fuel seeding tech. You may even find the same for afterburners. I know
I've seen articles on plasma igniters and seed plasma flame enhancement... If I was on my home computer I'd even have some at hand to link too.
So long as it is cooled; copper, alumina and tungsten may be all you need. No reason for you to keep a 'jug' of plasma sitting around. If injection is
the game then it might as well be your aim.
If you get a afterburner to run on silicon carbide let me know, it was a childhood dream of mine 
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Sedit
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| Quote: Originally posted by Neil | @Sedit Haha Ironic, You've got a wicked job.
@ fusionfire
Spray the fuel of choice into the engines exhaust gases, just replace a fuel nozzle with a plasma injector nozzle. A conventional plasma cutter with
some kind of venturi may even work - Ask Sedit!
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LOL naaa don't ask Sedit, just because I do it don't make me an expert, I just started a few months back and I have only so far worked with the 3000
gun which is a duel Nichrome wire ( or whatever we are using to coat) feed where the arc is generated between the two wires and they are vaporized
using electricity and blasted onto the surface using high pressure air or argon depending on the material being used. The 4000 gun is the one
mentioned above and due to its light weight, ease of use, and relatively low efficiency that is for the higher ups or very special jobs like when we
need to coat something with Titanium Nitride or another insainly hard material or ceramic.
PS: Its not a glamorous job as it sounds either, it is the hardest most grueling back breaking work I have ever done in my entire life and I have been
in the construction industry for over a decade now. This job is a total nightmare other then the pay 
[Edited on 25-10-2011 by Sedit]
Knowledge is useless to useless people...
"I see a lot of patterns in our behavior as a nation that parallel a lot of other historical processes. The fall of Rome, the fall of Germany — the
fall of the ruling country, the people who think they can do whatever they want without anybody else's consent. I've seen this story
before."~Maynard James Keenan
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Texium
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19-11-2023 at 16:50 |
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