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Can one burn aluminium wires using an electric arc?

  1. Apr 18, 2012 #1
    Could one burn aluminium wires by striking up an electric arc between them and then feeding them towards each other as they are consumed (like an arc light)?

    I assume the aluminium oxide would be burnt off as a vapour by the high temperature of the electric arc and thus would not inhibit the combustion process.

    I was thinking that one could convert the light and heat generated into electricity to power a vehicle.
     
    Last edited: Apr 18, 2012
  2. jcsd
  3. Apr 22, 2012 #2
    Are you planning to leaving a pollution of whitish Aluminum oxide fumes behind your car? also how effective will you be at harnessing the available heat energy and converting to motive force unless you can completely condense the products and remove their full heat value?

    The scenario is actually played out in the solid fuel boosters for the old Space Shuttle program which use aluminum powder and an oxidizer in a rubber (Thiokol) binder. Since the binder also burns and forms CO2 and H2O vapor, there is something to expand under the heat and form a propulsive gas. It's a light once, and no turning off type scenario, and I would suspect that aluminum wire burning would be subject to the same issue.

    In some sense, MIG and TIG welding (use of inert gas) for aluminum spells out the difficulty of sustaining an electric arc- the aluminum oxide can form an electrical insulator- fluxxing uses the principal of fluorides of aluminum still having conductivity as a melt. This allows for the arc to turned on and off at will
     
    Last edited: Apr 22, 2012
  4. Apr 22, 2012 #3
    I think i would like to capture the Aluminium oxide rather than emit it. I'm not sure how easy that would be! Maybe one could use cyclonic separation.

    I suppose most of the energy would be in the form of electromagnetic radiation that could be captured by photovoltaic cells.

    The wikipedia entry on TIG says AC current can remove the layer of aluminium oxide.

    I suppose my idea is just like MIG welding of aluminium but instead of using an inert gas to prevent chemical reactions I would be using air/oxygen to promote combustion.
     
    Last edited: Apr 22, 2012
  5. Apr 22, 2012 #4

    Borek

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  6. Apr 22, 2012 #5
    But in principle could one burn aluminium by striking an electric arc between Al electrodes and say directing a jet of oxygen on the arc?

    It seems feasible to me but I'm not an experimentalist (actually I'm not a theorist either!)
     
  7. Apr 22, 2012 #6
    I'm hoping that you can see that you will have so much more energy to harvest as heat than will be available as light, and that if you are taking an energy hit with photovoltaics and then electromotive conversion, the efficiency is all of the fractions multiplied. At "theoretical best' you might only get 1 ppth to 1 ppm of the energy converted to motion.

    The engineering nightmares of dealing with reflective and insulative Al2O3 vapor coatings condensing on all surfaces meant to channel or collect any of the energy forms would throw another fractional loss into the efficiency calculation.
     
  8. Apr 22, 2012 #7
    I've done it. Not for propulsion but by accident.

    An arc (if the current is high enough) can vaporize any substance known to man. It's far hotter than the Sun.
     
  9. Apr 24, 2012 #8
    Well one could heat up a thermocouple. They aren't that efficient apparently only 5-10% but thats better than ppth. As the temperature of burning Al is high one should get a good thermodynamic efficiency factor.
     
  10. Apr 24, 2012 #9
    Are you by any chance talking about something like this?

    In any case, aluminium is famous for requiring a lot of energy to refine properly. This obviously makes aluminum less useful as a fuel source. The industrial Hall-Heroult process is considered most efficient, and consumes approximately 55MJ (though modern smelters can achieve an efficiency of 46MJ) per kg of aluminium.
     
  11. Apr 24, 2012 #10
    Interesting link.

    I guess you have to make the Sodium hydroxide. Wiki says you can do it by electrolysis of sea water I think.
     
  12. Apr 25, 2012 #11
    Better than a thermocouple one could use direct thermionic conversion to produce electricity.
     
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