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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?"
Sounds great on paper, and it'll probably work quite well in smaller applications, but can this tech really be transferred to personal transportation?
I would imagine the delicate nature of the devices would make it hard and very expensive to enlarge. Hydrogen and solar power would probably be more practical for personal transportation, but underwater (especially deep sea) you don't have much solar energy and you probably wouldn't need all the power hydrogen can shovel at you.
... 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.
Mostly correct. Turbochargers do not recycle the exhaust gases like this diesel, but they do re-use it. Exhaust leaving the cylinders is redirected through a small turbine, which spins FAST (20-30k plus rpm ) that compresses fresh air into the intake valves. After spinning through the turbine, the exhaust gases leave as normal - polluting just as much as they would have otherwise.
:)
This creates more power because the one thing engines need to create power effectively other than gasoline is air. Instead of air coming in through an unassisted intake, compressed air that is forced into the engine is much denser and helps the fuel-air mixture ignite with much more "oomph". Some engines that can't handle the extra oomph don't take to turbocharging well as the explosions in the cylinders are more powerful than they were designed to safely take. But SOME motors take to it incredibly well...
It doesn't neccesarily consume more fuel. In fact, the act of turbocharging in itself does not make the engine automatically consume more fuel - it makes it CAPABLE of consuming more fuel because now it will be able to ignite mixtures containing more fuel that it couldn't ignite before. This is only if you have a lead foot, however.
On the note of both turbocharging engines and non-pulluting diesel engines, many (if not most) newer diesel engines on the road are turbocharged to help make up for the power deficiencies diesels have as the engine gets above ~2500-3000rpm (depending on the motor, of course). I wonder if this diesel is also turbocharged, meaning the exhaust would spin through the turbo, THEN go get recycled into oxygen. Interesting thought...
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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.
Of course, back in the 1960's Al Capp's Lil' Abner comic introduced the concept originally.
It's probably not a 'closed system' in the scientific sense, but is perhaps a closed system in the 'catalyst, fuel, waste' sense.
It must generate waste heat, for example, and I'm pretty sure that this waste heat is lost into the effectively infinite depths of the ocean, using it as a huuuge cold resevoir. On the other hand, there's no technical reason that the waste heat, in tandem with a complex metal catalyst, and a secondary cooling cycle, plus another process to trap 'waste' fuel byproducts, couldn't scrub the exhaust in such a way that it can be reused in the combustion cycle.
More bluntly:
water cooled air + disel => work, waste heat, emissions
work is work
waste heat + catalyst + emissions => hot air, hot gases, hot waste byproducts
hot air + heatsink + ocean => water cooled air
hot gases + hot waste byproducts + catalyst => contained wastes
Then N months later, when the fuel is completely spent, the submersible is collected, the solid waste cartridge is cleaned, and a new supply of fuel is fed into the system.
I'm guessing at this cycle, of course, but it's conceivable. =)
GPL Deconstructed
Volvo advertises it as the Prem-aire system, but I think they developed it in conjunction with Dow or some other chemical/manufacturing giant.
It is a big catalytic converter+radiator, using the waste heat piped into the radiator plus some really expensive and fancy metal catalyst/complexes to break down some emission gasses, NO2, NO3, O3, whatever, into cleaner and safer compounds. It probably is similar to what the Japanese sub does too, actually, but directly on the output of it's own emissions. I would think that the sub is able to store/trap the emissions because of a second cycle that takes advantage of the ocean as a big cold resevoir, otherwise volume/pressure/gas storage becomes a big deal under the ocean =)
The Volvo just lets the emissions free, but because they are technically cleaner and safer, it's okay, or something.
GPL Deconstructed
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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Brief product spec page from Matsui
Fuller details from U of Tokyo. Huge amounts of technical detail, but a January 1995 article (ie before the sea trials). Should answer most of the calls for "but how does it work?".
Paper describing and appraising the sea trials. Less detail on the CCDE, but a better overview (and written after they've tested the thing for real!).
Ok, so I'll have to throw some more authority into this... I'm German, and I tell you that there is no German word Schnorkel. There is a word Schnörkel, thich is entirely unrelated. The German work for snorkel is indeed Schnorchel.