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Carbon monoxide afterburner

I can't believe no-one's thought of this
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I expect this idea to disappear quickly because it seems too obvious and there must either be a fatal flaw in it or it's already been thought of, but what the hell, here it is.
Take the exhaust to the engine and burn the carbon monoxide in a second chamber, link this to the transmission and you have a more efficient engine as well as less toxic exhaust fumes.
Please feel free to demolish this as i think i must be missing something obvious. Baked, impossible or pointless, i'd guess, but in the case of the last two, why?
nineteenthly, Aug 08 2009

Carbon monoxide http://en.wikipedia...iki/Carbon_monoxide
acurafan07, you're talking bollocks. [Loris, Aug 08 2009]

Internal combustion engine with dual exhaust expansion cylinders http://www.freepate...ne.com/6393841.html
Strewth ... ! [8th of 7, Aug 09 2009]

[link]






       carbon monoxide can't be burned. what it is is basically carbon dioxide with one oxygen atom missing (which is why when it is inhaled it "steals" oxygen from your body to turn into more stable carbon dioxide).   

       now what would be very nice is if there was an efficient way of splitting the oxygen atoms from the carbon, but unfortunately not.
acurafan07, Aug 08 2009
  

       I thought 2CO + O2 --> 2CO2 was exothermic
FlyingToaster, Aug 08 2009
  

       That's what a catalytic converter does, among other things. Under normal conditions, it oxidizes about 99% of the CO that the engine produces. CO is a problem mainly when a car is left running in an enclosed garage, because it uses up most of the available oxygen, and there isn't enough left to support complete combustion. Neither a catalytic converter nor an afterburner would work without sufficient oxygen.
Jim Bob of Merriam Park, Aug 08 2009
  

       // carbon monoxide can't be burned. //   

       Wrong. It's very flammable; Coal gas ("town gas") is a mixture of Hydrogen, CO, and other compounds.   

       The problem with vehicle exhaust is that it's a very "lean" mixture; only 1 percent CO maximum with modern engines - even less for Diesels.   

       If the CO could be separated from the other gases in an energetically efficient way then maybe, just maybe, you could derive a small amount of energy from it.   

       Consider: A 4-cytlinder 4-stroke engine of 1000 cc capacity running at 4000 RPM. Total gas flow, 2000 litres per minute. At best, 1% CO = 20 litres per minute. One mole of CO is 28 g (approx) which occupes 22.4 l at STP - but this gas will be hot, which means there will be rather less than one mole present. So, derating for temperature, a yield of 20g per minute of CO as a "pure" fuel gas. The enthalpy of combustion is 283 kJ/mol; assuming perfect combustion, that's about 200 kJ per minute, equivalent to 3.3kW. Assuming an internal combustion engine is going to convert this heat energy to mechanical energy, with an efficency of (if you're lucky) 20%, that's nearly 700W of useful mechanical power, near enough one horsepower in the old money.   

       So you have all the extra mass and complecity of the reburner system, which is going to give you, in the end, an extra one horsepower and since modern 1000cc engines can develop 50 horsepower, that's about a 2% gain .... and you still have to have a zero-energy system to extract the CO from the exhaust gas stream (Some sort of preferential barrier diffusion might just do it).   

       All those agreeing that the idea has been comprehensively 'shot down in flames', say "Aye !"
8th of 7, Aug 08 2009
  

       //which is why when it is inhaled it "steals" oxygen from your body to turn into more stable carbon dioxide//
Err, no, it just binds more effectively with haemoglobin than oxygen does.
AbsintheWithoutLeave, Aug 08 2009
  

       This would fulfill the role of burning CO and unburned HC (hydrocarbons), like a catalytic converter does. But it wouldn't do anything about NOx. It might 'come on' faster than a cat, but it would need a constant or regular source of ignition to keep it burning reliably. Also, it would be more likely to cause backfiring and local hotspots than a cat. On the upside, it could be simple and lightweight and require no precious metals for catalyst. Funny, I was recently thinking of this, as a replacement for the recently-rusted-off cat on my daily driver.
afinehowdoyoudo, Aug 08 2009
  

       //carbon monoxide can't be burned. what it is is basically carbon dioxide with one oxygen atom missing (which is why when it is inhaled it "steals" oxygen from your body to turn into more stable carbon dioxide).//   

       Carbon monoxide can be burned. It's been used as a fuel as coal gas.   

       Also, it doesn't 'steal' oxygen when inhaled; its toxicity is due to the fact that it strongly binds to haemoglobin, preventing oxygen transport.
Loris, Aug 08 2009
  

       I'm happy for the idea to be shot down in flames, but a new thought has now occurred: NOx combustion. I have no idea if that could happen.
I also feel that this is in a time-honoured tradition in this place of trying to harvest teeny bits of leftover energy, which always makes me wonder about an engine which somehow harvests all of those teeny bits together. For instance, combine this with my hot car greenhouse effect Stirling engine and see what you get, plus maybe have the car sit there with a couple of wind turbines on top plastered in photovoltaics with a flywheel storing the energy from braking, and what have you got?
nineteenthly, Aug 08 2009
  

       Public humiliation, a gigantic repair bill, a claim for damages and possible criminal proceedings the first and only time you use a drive-through automatic car wash .....
8th of 7, Aug 08 2009
  

       Sounds groovy to me. Wash it manually and put little waterwheels all over it too.
nineteenthly, Aug 08 2009
  

       a combination HC's and CO high-speed fuel cell instead of a cat... manage that and you wouldn't need an alternator. Confused about NOx though: its production is endothermic so you should be able to get something out of it(?)
FlyingToaster, Aug 08 2009
  

       I'm going to bugger off temporarily and read up on nitrogen oxides.
nineteenthly, Aug 08 2009
  

       // run it rich //   

       Better combustion-chamber cooling, yes. Analogous to a double expansion steam engine, where energy is extracted by successive cylinders.   

       Double-expansion internal combustion engine, anyone ?   

       <link>
8th of 7, Aug 09 2009
  

       IIRC, Mazda cars use afterburners. But they don't generate more useful power; they're just a cheaper but less efficient alternative to catalytic converters, to reduce pollution.
notexactly, Aug 26 2019
  

       //IIRC, Mazda cars use afterburners.//   

       I had a good look around at this and as far as I can tell you're talking about recirculaion, which is not Mazda specific. Anyhow, diesel exhaust, nasty stuff. Certainly not suitable for the busses that tool around urban areas, usually right in front of me.
bs0u0155, Aug 26 2019
  

       Hmm. Maybe the thing I read years ago was mistaken or misleadingly written. Yes, EGR isn't Mazda-specific, but I didn't think that's what I was referring to.
notexactly, Aug 26 2019
  

       //I didn't think that's what I was referring to//   

       There are cylinders that capture particulates and slowly burn them, not Mazda specific either. Mazda seem to be doing fancy things with diesel engines, essentially lowering the compression ratio, there's benefits in NOX and materials there, but I can't work out how they're getting around the absolute basics of compression ignition. Lower compression ratio is lower efficiency, and no amount of fancy injectors are going to compensate for a cold charge.
bs0u0155, Aug 26 2019
  
      
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