Slashdot Mirror
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?"
Can it be applied to low emission vehicles
Eventually... maybe, forseeably... no.
This little robot cannot possibly be consuming as much fuel as your 2 ton car. Now if we can make your 2 ton car consume as much as the little robot, we're in business...
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.
"I say consider this day seized!" -Hobbes
"Tomorrow we'll seize the day and throttle it!" -Calvin
One might stop to notice the date of November 22, 1996 on this article.
Don't you love cutting edge Slashdot.
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.
" Instruments aboard the robot take quick measurements of the seawater's oxygen content, salinity, temperature, and pH value at four-second intervals, or about every five meters. The robot can also be equipped with instruments to measure magnetic fields and metal concentrations in the water, and otherwise investigate the oceanic environment."
Well ain't that nice. Is this supposed to imply that seawater is somehow used in the function of the engine, or are those sensors for other purposes?
--
"Karma can only be portioned out by the cosmos." - Homer Simpson [1F10]
My question is why not use a fuel cell, then I saw the date. That's why.
"Mr Peabody, set the way-back machine"
"You never truly understand a thing until you can explain it to your grandmother" -Albert Einstein
If I understand turbo correctly, all it does is take some of the pressure from the exhaust gas and uses that to force more air into the intake, consuming more fuel but also providing more power.
"I say consider this day seized!" -Hobbes
"Tomorrow we'll seize the day and throttle it!" -Calvin
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.
Treatment, not tyranny. End the drug war and free our American POWs.
See my user info for links.
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...
"This is Zombo Com, and welcome to you who have come to Zombo Com" - www.zombo.com
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.
You might want to reconsider that statement. That is unless this is a story about how there are no longer any laws of thermodynamics.
If I understand turbo correctly, all it does is take some of the pressure from the exhaust gas and uses that to force more air into the intake, consuming more fuel but also providing more power.
/. that are also capable of mech hacking. It's a different, but very similar art.
Correct. A turbocharger (technically, they're called turbosuperchargers, the nomenclature you'll find in older literature) simply captures kinetic energy and heat energy (via gas expansion) from the hot exhaust gasses and uses that energy to stuff more air into the engine's intake. This results in a denser fuel/air charge and volumetric efficiency of over 100%. Plain old superchargers do the same thing, but are driven directly by the engine rather than by the exhaust. Now that they can be made cheaply, superchargers are gaining in popularity (check out some of Mercedes new motors) since they avoid the "turbo lag problem, and also provide a cooler intake charge (the centrifugal compressors in most turbos put a lot of paddle wheel work into the air.)
As an aside, high performance normally aspirated engines (no turbo or supercharger) can also exceed 100% volumetric efficiency, but not by a whole lot. A good turbocharger or supercharger system does *amazing* things to the performance and efficiency of a car, and if you take good care of them (use really good oil and change it religiously), they aren't a significant maintenance problem.
I'm always surprised that we don't have more multidisciplinary hackers here on
"The future's good and the present is nothing to sneeze at." - Roblimo's last
Of course, back in the 1960's Al Capp's Lil' Abner comic introduced the concept originally.
I'm pretty sure that Subaru's WRC rally cars have an efficency-increasing trick that, although not as scientifically interesting as the concept peresented in the story, would improve a car's effeciency.
AFAIK, there is a heated plate in between the engine exhaust outlet and the turbo turbines. This plate heats up any uncombusted fuel in the exhaust (there's generally a fair amount of uncombusted fuel left over) and it ignites, thus giving more power to the turbines. Of course, in the rally cars, it is tuned towards power (it does wonders to decrease low-end lag, I guess).
I bet this would be a great thing to add to, say, a high-efficency economy turbocharged engine. Also, it doesn't seem that complicated to implement. Anybody ever try adding a similar mod to their car?
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.
Fuel cells work adequately as a solution to the fossil fuel problem, if you can live with less fuel or a bigger gas tank (hydrogen is the most often proposed fuel, and can't be stored at liquid densities). Many varieties of hydrogen-based fuel cells are made from cheap materials, so cost shouldn't be a problem. This skips the carbon cycle all together (source water -> hydrogen -> water vapour -> rain -> source water).
Another solution is to switch to burning methanol. You can either produce this by fermentation, or build it directly from air (for CO2), water (for H2), and power (solar, nuclear, or whatever). Both ways draw carbon back in from the environment, stopping the short-circuit of the carbon cycle that's causing problems with fossil fuels. Methanol can be burned (cleanly) in conventional internal combustion engines, and can also be burned in advanced fuel cells (which may be expensive; I'd just use a normal engine). It can be stored as a liquid, though you'd probably want to put it in a pressure vessel (like propane) to keep it from slowly boiling off.
In practice, neither of these solutions will be implemented until the cost of gasoline and diesel rises to a level high enough to justify the switchover cost.
I know it's off topic from the underwater diesel, but superchargers are on many more cars than just new Mercedes motors. Turbochargers are out there, as well. One will never replace the other, no matter what the price difference gets to be. As you pointed out, some prefer superchargers because they don't have the lag characteristics of turbos, but there's also a preferences for turbos since superchargers are belt driven and therefore parasitic on the motor, whereas turbos merely use waste exhaust anyway.
;) Just to letcha all know who didn't already, engines are growing so dependant on computers that a common upgrade is to swap out the engine management chip with one that gives more aggressive valve timing and fuel mapping (at the expensive of fuel economy, of course) that can bump the output by 10 or 20% or more. On the note of turbochargers, turbocharged engines usually respond to these chip upgrades AMAZINGLY well since the computer can also control the boost characteristics of the turbo.
:)
Also, there have been a number of successes in turbocharging systems that cut the lag to virtually zero, namely twin-turbo systems. The best such success that comes to mind being the twin-turbo Toyota Supra of the mid-90's, these systems utilize a small turbo that spins up faster with almost no lag, and a larger turbo which takes longer to spin up, but provides more power than the small turbo once it does.
I agree with your comment of surprise about the lack of gearheads (or at least wannabe gearheads) amongst slashdotters.
After all, whats the point of having an overclocked, Linux powered mp3 player in your ride if it's a stock Dodge Neon or Toyota Corolla that has so much potential under the hood that can be "overclocked" itself?
"This is Zombo Com, and welcome to you who have come to Zombo Com" - www.zombo.com
In any case, I think solar energy is better suited to stationary or low power mobile devices, not transportation. I am a big fan of biomass energy [biomass.org] for cars. Biomass methanol has a very high net energy value, a closed carbon cycle, and is safer than compressed hydrogen.
You could also produce methanol directly from air, water, and power, which might have higher efficiency (as long as you have an efficient source of energy). I'm told that the solar conversion efficiency of plants is actually rather low (your linked page didn't list figures to check this).
Hydrogen comes by electrolysis, which is very efficient.
CO2 comes out of air by fractional distillation or by effusion (take your pick; I'd personally go with fractional distillation). Energy cost of producing the low temperatures needed will be much less than the cost of the hydrogen electrolysis, so efficiency of this step isn't very important.
Then you burn the CO2 incompletetly in a hydrogen atmosphere, and fractionally distill the results to get the methanol. The other products (water and some other simple compounds of carbon, hydrogen, and oxygen) can either be sold as solvents or for use in industrial processes, or burned (producing heat or power) and fed back into the system. Even the primary reaction (burning of CO2 in hydrogen) is exothermic, so you'll get some heat recovered from this stage too.
Cleanly powering the conversion plant is left as an exercise to the reader, but either a solar heat plant or a nuclear plant should be adequate and reasonably clean (compared to fossil fuels).
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".
I work on all kinds of cars, whenever I can. I used to be a faculty advisor for a college car club at Purdue University, (http://fox.vet.purdue.edu/) and got down and dirty with all sorts of automobiles.
My current project vehicle and daily driver is a 1984 Chevy K10 Blazer with the 6.2L diesel. I'm planning on adding a turbo kit from Banks in a year or so, and get this truck over 40mpg on the highway.
Should be interesting...
The local rally coverage mentioned the no-lag turbo systems this afternoon.
The way they described it is that when the driver takes their foot of the throttle, air/fuel is still sent to the engine but not ignited - the EMS cuts the spark, like with some rev. limiters. Instead, the fuel is ignited in the exhaust which keeps the turbine spinning up to speed. When the throttle is opened up again, there is no turbo lag. The downside is the exhaust is *much* hotter (> 1000 deg. C) which places additional strain on the engine components, and the firewall requires heavy insulation to prevent injury to the occupants, particularly the driver's feet.
This type of system wouldn't work on a road car - the unburnt fuel igniting in the exhaust would wreck the catalytic converter/mufflers in short order.
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.
- "Hear that?! The percolations are imminent! Cease your ingress!"
...we obey the laws of thermodynamics!
Photos.
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!).
Although this is offtopic, I thought I'd put in a couple of words.
It's true that superchargers are lesser used in production vehicles than turbochargers. This is for several reasons.
First, turbos use exhaust energy instead of the crankshaft to drive them. Turbos have a lot of useful features that make them better than superchargers for production vehicles. Firstly they are more efficient (this is assuming a properly sized unit that is tuned by the factory), they can compensate for altitude, and they can be controlled by an emissions computer.
Superchargers on the other hand are not computer controlled, do not compensate for altitude, and (in production vehicles) have a higher air temperature than turbos (most all production vehicles have intercoolers).
The type of supercharger used on production vechicles is usually a roots/twin screw positive displacement variety. These produce almost instantaneous boost, but are inefficient at high boost values. Cosequently they usually don't go higher than 8 psi max, 4 or 5 psi nominal. These installations use aftercoolers (water cooled radiators in the manifold) to cool the intake charge, on vehicles with enough intake volume (such as the Ford Lightning). The primary manufacturer of these superchargers is Eaton.
Turbochargers on the other hand are very widely used and generally produce more power than superchargers. The 1984 Mustang SVO and Thunderbird Turbo Coupe saw about 18psi max. That is an HPT (High Pressure Turbo) design. Volvo uses LPT (Low Pressure Turbo) turbos in several of their vehicles, the S80 T6 to be one. LPT turbos provide a small amount of improvement over NA power, however they can be tuned via computer to produce much more power. Turbos suffer from an efficiency problem that many are not aware of. Specifically they have anywhere from a 2:1 up to 6:1 pressure differential between the exhaust port and intake port of cylinders. This means that if you have 10 psi boost, you have 20 to 60 psi backpressure. This is a significant limitation of turbo designs and what limits their output. Maximum compressor RPM is the other limitation. Most compressors do not exceed 120,000 RPM. Smaller turbos turn faster to move the same amount of air that larger turbos move at lower RPM.
In conclusion, superchargers are generally installed on cars that were originally naturally aspirated, because it's a relatively easy conversion. However, turbos do not easily adapt to naturally aspirated cars because they don't integrate with the engine control system easily.
Here's a list of cars that come with superchargers (that I know off the top of my head):
Volkswagen Corrado G60
Ford Thunderbird SC
Pontiac Grand Prix GTP
Mercedes SLK Kompressor
Jaguar XK8
Ford Lightning (1999+)
Nissan Frontier (2001+)
Aston Martin Coupe (Jaguar)
However the list of turbo cars is probably 20 times the above.
As a side-note: the Dutch actually had invented the schnorkel I think already before the war. The Germans discovered and applied the invention later on. (I read Doenitz's memoirs so I consider it a good source)
Reminds me of a funny quote I ran across awhile back. This is exactly how I feel about life:
So I can't do some of those things, but I wouldn't mind learning! That's probably what sets us geeks apart from a lot of other people: we like to learn as much about everything as we can."I say consider this day seized!" -Hobbes
"Tomorrow we'll seize the day and throttle it!" -Calvin
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.
We've got Air Independent Propulsion on some of our subs in the Swedish Navy... (well, as some of you would point out, it's only independent for a period of time.) The trick is to use liquid O2 and a diesel burner to drive a Stirling engine, and use enough pressure during combustion to be able to feed the exhaust out into the water. Since it's mostly CO2 it dissolves quickly. For the burner to get "air-like" oxidizer the O2 is mixed with a small back feed of reused exhaust. There is a more thorough explanation on Kockums website.
This is not as clean as the drone in the original article, but OTOH, the collected exhaust in the drone has to be disposed of somewhere - it's not gonna disappear just because it's not in the atmosphere.
Score:-1, Wrong
There are a lot more supercharged cars than that, and they began appearing decades before the first turbos (the 1962 Chevy Corvair Monza Spyder and Olds Jetfire.)
For more info on superchargers and their advantages over turbos in many circumstances, check out:
Jackson Racing's Supercharger Info Page (Talks about the advantages of supercharging over turbos in many apps. Check out the rest of the site for info on their kits, which have received rave reviews for value, performance, and reliability.)
Paxton Superchargers (The one that popularized production superchargers in Studebakers and 1960's Mustangs and Shelbys.)
Vortech superchargers (Hybrid type - turbo-style compressor driven by a gearbox. Persoanlly, I think this combines the worst features of both, but some people really like these...)
"The future's good and the present is nothing to sneeze at." - Roblimo's last
The world leader in the production of liquid hydrogen is Air Products & Chemicals. Their website includes information on how they produce liquid hydrogen, and current research they are doing on powering automobiles with hydrogen.
First, hydrogen is rarely produced by electrolysis--it's cheaper to use a reformer to extract it from waste gas at a petroleum refinery.
Second, there are two proposed methods of powering fuel cells in cars with hydrogen. One way is to separate the hydrogen from gasoline (or propane) in the vehicle. This is less efficient, but is simpler: you don't have to replace the gas station infrastructure. The other route is to ship and store liquid hydrogen, and go through the hassle of replacing the gas station infrastructure.
There are a lot of benefits of liquid hydrogen. There's lots of power there--but nobody should forget that liquid hydrogen is what sends the space shuttle blasting into space. While the explosion risk is real, the more likely risk is the extreme temperatures: liquid hydrogen boils at more than 400 degrees (F) below zero. If a little bit of liquid splashes on you, you can lose a limb.