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Submersible Robot Diesel Recycles Its Exhaust
An Anonymous Coward writes: "This might be a good weekend topic to kick around. Trends in Japan has a short article on an undersea robot that uses a contained diesel. 'The engine itself is a completely closed system that needs no intake of air to run and chemically processes exhaust gas inside the robot. On-board devices reinfuse the exhaust with oxygen after removing its carbon dioxide and reuse the gas in the fuel mixture. The seawater is kept clean, as no gas is released.' Any /.'s working with this tech? Can it be applied to low emission vehicles?"
... the Draeger closed circuit breathing apparatus I used to use when I was on a mine rescue team. The only downside to these units was the fact that after about 10 minutes of use, the air would start getting /real/ hot. The chemical reaction that took place when cleaning the CO2 out of the exhaled air made everything hot. After a half hour of use, it would start to get almost to hot to breathe, and even more so if there was strenuous work involved.
Isn't this probably the exact same thing that's been done on diesel submarines for the last half a century?
No, not actually. Submarines (the non-nuclear variety) run on diesel engines while surfaced, but on battery power while submersed. Your typical garden-variety WWII sub could stay underwater for about a day before it had to surface to recharge its batteries. This made German U-boats (and other subs too, I'd imagine) quite vulderable to attack (the surfacing was to the tune of several hours) until a snorkel was developed to allow oxygen to be breathed into the motor without surfacing the whole ship.
So no, though there is probably a small amount of reuse of some exhaust gasses, previous diesel subs still need to breath air and operate on battery power while under water.
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Does sound like a somewhat useful step in submersible development, though of course it would have to surface sooner or late to refresh it's supply of fuel and vent spent fuel byproducts. Conservation of energy and all that.
I expect that whatever oxygenator they are using on the exhaust may be extremely expensive to implement on POVs.
It could be a catalyst, for example, that costs big $$ to make, and could be toxic and expensive to displose of when finished.
There's no magic here. In the past I've been a huge fan of EVs, but am disolusioned by the slow rate at which battery energy density has improved, especially considering the toxicity and expense of the new materials -- even compared to lead.
Slowly, I'm warming up to the hybrids. Something must be done to cut down on fossil fuel usage.
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There's a Thyssen system that uses liquid oxygen, diesel fuel, and argon. The liquid oxygen and argon are mixed to produce an "air" mixture for the engine, and then the argon is separated from the exhaust and recycled. This requires much less storage volume than carrying compressed or liquid air. Something like this is probably what's being discussed.
SAAB had a similar concept known as the vehicle exhaust recirculation concept. It was an experiment to address the fact that the majority of pollution given off by modern automobiles occurs at startup, before the catalytic converter reaches the critical temperature needed to properly "scrub" the exhaust of its pollutants.
SAAB's response was to develop a system that would route the exhaust of the car for the first 25 seconds into a balloon. After 25 seconds, the catalytic converter SAAB was using had heated sufficiently to properly scrub the exhaust, so the balloon's exhaust contents would then be filtered back through the intake manifold into the engine to be run through it again. The flow is regulated so as not to affect engine performance.
The net result from this system was lower emissions than the US Ultra Low Emission Vehicle (ULEV) standard, but SAAB hasn't announced any plans to put it into commercial use.
There is an article with more details here. Once the page loads, you can quickly get to the SAAB information by searching for "SAAB".
They used a tank of O2(liquid?), a small tank of Argon or Helium for ballancing appropriate pressures/volumes when using pure O2 for smooth combustion in the diesel engine(this being the only reused gas), a tank of diesel fuel, a condensation loop to remove the H2O vapor from the combustion products (simple, since theres cold seawater surrounding the whole deal) and from the inert pressurizer and a giant canister of Lithium Hydroxide. The LiOH removes the CO2 from the combustion products via:
2 Li(+) + 2 OH(-) + CO2 -------> Li2(CO3) + H2O.
The only "On-board devices that reinfuse oxygen" I'm guessing are going to be O2 tanks. Maybe I'm missing something but there dosen't appear to be anything revolutionary here.
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