Australian Team Working On Engines Without Piston Rings 368
JabrTheHut writes "An Australian team is seeking funding for bringing an interesting idea to market: cylinder engines without piston rings. The idea is to use small grooves that create a pressure wave that acts as a seal for the piston, eliminating the piston ring and the associated friction. Engines would then run cooler, could be more energy efficient, and might even burn fuel more efficiently, at least according to the article. Mind you, they haven't even built a working prototype yet. If it works I'd love to fit this into an older car."
Let me be the first to say (Score:3)
This is 2014, where's my flying car?
Oh wait, I can't afford it.
Please give me grooves for an extra 2 miles a gallon in a way that the local shop can fix (looking at you, battery/hybrid-CVT/regen-braking monster).
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This is 2014, where's my flying car?
Oh wait, I can't afford it.
Please give me grooves for an extra 2 miles a gallon in a way that the local shop can fix (looking at you, battery/hybrid-CVT/regen-braking monster).
My local shop can fix Priuses. Last time I was there with my car (not a Prius), they had one up on the rack for a transmission/transaxle replacement.
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In the old days, if you blew a transmission, the shop could rebuild it while you waited. Now, they wait for a replacement to be flown in, then swap it out.
That's true, but that's not limited to Priuses -- when I thought I had a leaking shaft seal in my transmission, they were going to have to send it out to a specialty shop and wait a week for them to rebuild it because they don't rebuild transmissions in-house.
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Back in the 60s you werent getting 40mpg and 500 mile range in a car that required no warm-up time in the dead of winter, went 10000 miles between oil changes / servicing (easily), and was affordable on a waiter's salary.
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They are working on channeling climate change problems into carnado. It even comes with shark wipers.
Re:Let me be the first to say (Score:5, Insightful)
I'm really annoyed at the US car market.
Take any car that is available in Europe, and the only engine you can get here is the biggest one that's available there. I drove on European highways with a 1.1l Fiesta. It won't win any races, but it goes fast enough, and sips fuel. Same car, US side? 1.6l engine. Still pretty good mileage by US standards, but few people would buy it across the pond with the "big" wasteful engine.
Diesel? over 60% of the market in multiple Euro countries. Small HDI engines that give you more oomph than a 2.0l gas one, and torque like a small V6, for two drops of fuel per mile. States-side? Gotta buy a VW/Audi at a premium, or trust GM to have finally made a reliable econobox. For starter, the GM solution with a urea tank is probably not really happy today in the northwest (freezes at 12F according to the web).
So yeah, I'd love a diesel, or a European car, so I can say bye-bye to the fuel pump without lugging batteries and paying a repair premium (and no 10yr resale value). But you can't get them here, because someone decided that Americans NEED MORE POWAAAAR, or something. To drive 65MPH.
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European fuel typically has a higher octane rating than fuel sold in the USA, therefore they can tune their engines more aggressively, therefore they can get more power out of a smaller displacement engine.
Re:Let me be the first to say (Score:5, Informative)
I believe this is not true. When I lived in New Zealand I noticed that the octane ratings were higher than in the USA, but after researching this, discovered that the difference is mostly accounted for in a difference in the way that octane is measured. In New Zealand (and probably Australia, and probably Europe), the rating uses just the "research octane", i.e. that measured in a lab somewhere; but in the USA, the rating is an average of the "research octane" and the "measured octane", the measured octane producing a lower number, that when averaged with the research octane, means that the same fuel is rated at a lower octane rating than it would be in New Zealand.
Re:Let me be the first to say (Score:4, Informative)
The parent poster is correct. See examples of conversion between various fuel ratings [wikipedia.org] and look at the "regular" gasoline entry. Basically, take the US rating and add 4 to get the Australian/New Zealand equivalent.
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European fuel typically has a higher octane rating than fuel sold in the USA,
Not only is that not true but you could always just use an octane booster. And anyway it doesn't actually matter in modern cars; if you put lower-octane fuel in them you'll lose low-end performance, but they'll do fine in the high end and they won't kill themselves because they have a knock sensor and can retard their own timing.
Further, diesel doesn't run on octane, it runs on cetane. And the small diesels are what we really want and don't get.
Fuel efficiency is nice, but... (Score:5, Insightful)
Extra fuel efficiency would be nice, but I am most excited about the prospect of the engine itself lasting longer. Less friction = less heat, less wear & tear, etc. A cool, frictionless engine could potentially last for half-million miles before needing replacement. At my paltry 10-20k miles per year, I could potentially never have to buy another car again.
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Except engines aren't the things that cause you to buy a new car. The chassis rusting through, or the plastic components all rotting simultaneously, or the suspension beginning to go, or a whole bunch of small things adding up... These are the kind of things that cause you to buy a new car.
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Extra fuel efficiency would be nice, but I am most excited about the prospect of the engine itself lasting longer.
Buy a diesel.
For a light duty diesel truck engine, 300,000 miles is considered the 50/50 point where you *might* have to fix stuff that's starting to wear out.
For industrial/heavy diesels, they can more or less run forever as long as you keep changing the fluids.
My understanding is that gasoline engines are generally not overbuilt for strength, otherwise they'd have the same service life as diesels.
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Extra fuel efficiency would be nice, but I am most excited about the prospect of the engine itself lasting longer. Less friction = less heat, less wear & tear, etc. A cool, frictionless engine could potentially last for half-million miles before needing replacement. At my paltry 10-20k miles per year, I could potentially never have to buy another car again.
What do you think is going to keep those pistons centered and friction-less? And where is the heat of combustion going to go?
At 10 to 20K a year you may already never need to buy another car, you just WANT one.
Modern cars have no particular problem reaching 200,000 miles, and even 300k.
The wear that piston rings impose is undone by a ring job. Used to be able to get that done at the corner garage without a great deal of hassle or money, but now days it costs around $2000 bucks do to the complexity of mode
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When I was driving around an '86 golf I was considering upgrading the engine since the old VWs made that a trivial affair. I'm sorry to report that you can buy a brand new engine for a few thousand dollars. It's rarely "the engine" which gives out in a car. It starts with the door handles breaking off, the dash getting smashed, the bumper starting to rust and then you get into the really expensive stuff like transmission and random engine bits.
If you just want to drive the same car with a well running
A car refurbishment industry (Score:3)
Why isn't there a car refurbishment industry, or at least a cottage industry?
There are always those models of cars which through design refinement seem to reach a "bullet-proof" stage where the major mechanicals are extremely durable and are produced in massive scale, like the Camry.
Assuming they don't rust out (which seems to be less a function of corrosion than mistreatment and unrepaired body damage), you would think that someone would be in the business of refurbishing them to a near-new kind of state.
T
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I've never had an engine fail due to piston ring wear.
Seems to me this may be an idea looking for a problem.
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The engine is about the LAST part of the car to wear out, given reasonable care and maintenance. An engine actually WILL last a half million miles without major overhaul as it is - only if your treatment is not assholish. An automatic transmission is much more liable to seddenly fail completely, often with no warning. If you are stuck living in the rust belt, the body, frame, brake and exhaust components, are by far the shortest lived due to corrosion.
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I hear people complaining about this as much as ever, but cars are lasting a lot longer now than they used to. It wasn't all that long ago that a car that reached 100,000 miles was sold off or traded in as a junker. Now, any car that can't reach 200,000 miles at a minimum (with moderate care) is considered to be of poor quality. Maintenance itself is getting easier, with longer times between oil changes, tune-ups, and other general maintenance. Hell, even tires are lasting considerably longer.
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The Auto Industry would never have that. Planned obsolescence is the current MBA business model.
I do not know how old you are, but when I was a kid, cars were nothing like they are today. A lot of people bought new cars every two years. And if you got 100 K miles on a vehicle, you did well, and the vehicle was just about finished.
As the years went by, there were many improvements in both the mechanics and structures of the vehicles. My first car, a 1965 Buick Skylark, had a lot of work done to it to repair rust at 70K miles. That was typical.
When I was a gear head way back when, we would some tim
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The question really isn't whether or not it could last 30 years, but rather would you *want* it to?
I drive a 2001 convertible. It's not a bad car, and runs as if it were new. It has all the luxury options: automatically dimming rear view mirror, leather seats, Bose Infinity speakers, 200 HP engine, etc. I've taken excellent care of it, regular oil changes, fix any problems before they escalate, etc. Even so, it's near the end of its being interesting to me. Its styling is looking pretty passe, the electroni
Re:Fuel efficiency is nice, but... (Score:4, Funny)
Yes, yes this is exactly what we want you to think.
Thanks,
The Auto Industry
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Take a good hard look at new cars.
Touch screen controls, throttle by wire, even more plastic then your 2001.
You should be able to afford a really nice older car by now. No more payments bullshit.
Corvettes of many years are interesting. Original ZR1? Any pre-disco 'vette.
Jag E types with the six have all the styling and much less unreliability vs. the V12s. Still Lucas electrics and English, so wear good walking shoes.
77 7.3 super duty TA?
Last gen RX-7?
Original Audi Quattro?
GMC Syclone/Typho
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And safety regulations allowed it to be seatbeltless, as it came that way from the factory. And a non-compressible steering column, and "bad" bumpers, and all that.
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Do you know how I can tell you're a kid?
Do you think gas powered cars have always run 250K between engine rebuilds? (That's mostly down to hard chrome plated piston rings.)
When I started driving you got 100K between engine rebuilds.
When my dad started driving you got 40K between engine rebuilds.
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Car overhauls rarely do this because its the cylinders aren't meant to be as easily removable as they are on aircraft engines.
You end up needing a whole new block. If you have some aluminum engines, you can get away with just sleeves.
But still, pulling an engine, pulling pistons, honing cylinders, new rings, valves, maybe new piston rod bearings, maybe new pistons, can be done for around 2000. New/rebuilt engines can be had for 3 to 6K.
I See A Problem (Score:2)
So, the idea is that the grooves in the piston will create little eddies of air that separate the combustion chamber from the oil galley, right?
Here's the problem - the air that forms said eddies has to come from somewhere, and there's only two options: the combustion chamber, or the oil galley.
Still, to a gear head such as myself, it's still a pretty cool idea.
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So, the idea is that the grooves in the piston will create little eddies of air that separate the combustion chamber from the oil galley, right?
Here's the problem - the air that forms said eddies has to come from somewhere, and there's only two options: the combustion chamber, or the oil galley.
Still, to a gear head such as myself, it's still a pretty cool idea.
It is cool. You're right about the eddies having to come form somewhere. I think, from reading the article, (sorry slashdot Gods) that the eddiese are frmo the fuel -air mixture, as they talk about a stratified charge happening.
Anyhow, the concept is fairly sound - I think - my concerns are regarding cold to hot operation, and starting.
At least it's not like the goofy Magnets pulling on pistons crap some scammers have been trying to feed us.
Okay...nice and all... (Score:3, Informative)
But we already have an engine that doesn't use piston rings. [wikipedia.org] And it's not like this idea hasn't been tried before either on reciprocating piston engines, usually with a whole series of problems. Mostly compression issues.
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Right, because the seals along the rotor don't do exactly the same thing as piston rings, only less effectively.
Re:Okay...nice and all... (Score:5, Informative)
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Ringless engines are common: 2 stroke model airplane engines.
You mill the piston sleeve from the bottom, so tool runout leaves a slight taper. Then you hard chrome one side of the piston/sleeve combination. When you break it in the hard side wears the soft side to match 'perfect', with the seal tightening at the top of the stroke.
They run a little dirty and aren't exactly long lived.
funding for bringing to market? (Score:5, Insightful)
Wait, what? (Score:5, Insightful)
From TFA:
A 'virtual model' equates to 'proof-of-concept'? Since when?
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A 'virtual model' equates to 'proof-of-concept'? Since when?
This is an interesting question, I'd also love to hear what the US Patent Office has to say about it.
Why not eliminate the piston too? (Score:4, Interesting)
I thought this was about this article [newscientist.com] which uses a pistonless pressure wave and makes all the same promises.
Hang Ten big Kahuna (Score:3, Funny)
Why not eliminate the engine completely? Just aim in the direction of the destination, detonate, and surf the pressure wave.
With the engine-less car you can't take it with you, but if you don't make it on the first shot you won't be around to care.
Interesting (Score:2)
Why are they developing a new engine? (Score:2)
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I can't see that it will be beneficial. (Score:2)
You'd have to keep the CR low enough to not overcome the pressure wave of the ringless design. That means you'd lose efficiency in the engine. Reducing friction is a great concept but I'd still like to see the math involved as to how they'd get the efficiency out of the engine vs. a traditional design and how they'd keep the crankcase temps down and the oil clean. Most of that black/brown gunk in your oil at an oil change is blow-by, products of the combustion process. Even with piston rings you get a ce
This is an old idea (Score:5, Interesting)
Australian? (Score:2)
I thought they were shutting down thte Australian car plants (by 2017)
Looking for funding? For what? (Score:4, Informative)
How much would it cost to create a prototype? Get a used lawnmower engine, find a piston from a slightly larger used lawnmower engine (up to here you spent about $50), then turn some grooves in there and see how it purrs.
What are we talking about? a couple hundred bucks?
It would cost way less to try this in real life than all the computer simulations. Something smells fishy.
Re:Nice idea but... (Score:5, Funny)
I'm sorry but the energy density of hopes and dreams is nowhere close to that of gasoline.
Re:Nice idea but... (Score:5, Funny)
But hopes and dreams are of endless supply. Gasoline not so much.
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Re:Nice idea but... (Score:5, Funny)
That's how the Prius works. It's partly powered by smug.
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Are you sure they didn't say you can't BREED it like you can a horse?
If that were the case, they were correct.
Find me two cars you can rub together and get a third, without losing anything from the prior two.
And all for the cost of not mowing your lawn.
Re:Nice idea but... (Score:5, Funny)
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I'm not switching from gasoline until someone makes an engine that will run on distilled suffering of hippies.
Not all 'hippies' are created equal. I tend to consider myself as somewhat hippy-ish. I believe in peace, love, understanding, environmentalism, nuclear power, GMO foods, high-technology, and the idea that we can - in a perfect world - eliminate the need for work allowing people to concentrate on the betterment of themselves and their fellow man.
Note that the vast majority of 'hippies' disagree with me vehemently on nuclear power and GMO foods (and some disagree on the high-tech). From my point of view a
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Gasoline's energy density is nothing special, the advantage it has is in procurement, having resulted from millions of years of energy collection which means the effort of getting to it is trivial.
And compared to the alternatives, it's a messy bit of junk.
Its pretty special.
Even discounting cost, there are virtually no other fuels that come close.
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It is nothing special from a volumetric energy density (MJ/L) point of view. It's in the same general range as all primarily petroleum based fuels which are liquid at room temperature and atmospheric pressure; more toward the lower end of the range. It is substantially more than liquefied gases and solids such as coal and wood.
Petrodiesel 37.3 MJ/L
Crude Oil 37.0
Gasoline 34.2
Gasohol E10 33.2
Jet A 33.0
Biodiesel 33.0 for comparison
Diesel is both cheaper (in normal countries, not the ridiculous US pricing struc
Millions of years of storage, not collection (Score:2)
Gasoline's energy density is nothing special, the advantage it has is in procurement, having resulted from millions of years of energy collection which means the effort of getting to it is trivial. And compared to the alternatives, it's a messy bit of junk.
You are confusing storage not collection. The energy was collected over the very short time span of a plant in a swamp. The millions of years that turns this into crude oil is just chemical transformation and storage.
Gasoline is a simple molecule that can be created in a variety of ways. One way is the distilling of crude oil. Another is biological production via engineered photosynthetic organisms. Same energy source of the fossil fuels, the sun, however carbon is coming from the current atmosphere not
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In what universe is gasoline a molecule? I was under the impression it was a mix of various hydrocarbon molecules (among other things).
OK its a few simple molecules, C7H16 through C11H24. Things vary with the desired octane. Ignoring government mandated additives MTBE, dyes, etc
Still, very amenable to a biological process.
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-1, you forgot "Burma Shave!"
or were you going for haiku format? Too many syllables in that one for a haiku.
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Whereas the majority of other peoples' are between 5% and 50% ethanol.
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Put ALL effort into engines that don't use fossil fuel at all. Thanks.
Exactly, since the internal combustion engine has no future at all in the long term, such a breakthrough is not exactly "news that matters". Now, a great breakthrough in battery technology, or, even better, a nuclear fusion electrical generation station would be something worth thinking about. High storage capacity batteries that can be fully charged in only a few minutes and last for hundreds of kilometers of high-speed driving would kill the internal combustion engine for most vehicles. But nuclear fus
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Soylent gas be okay?
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Soylent gas be okay?
Isn't that the solution to pension plan problems and social security?
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Put ALL effort into engines that don't use fossil fuel at all. Thanks.
Then effort doesn't go into 'engines' - It goes into energy storage solutions that have the weight / energy capacity of gasoline.
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Hardly imbecilic to me. It depends on how you define volumetric energy density. If based on the simple energy release of combustion, then yes the engine is not a factor. If based on the actual energy put to useful purpose (turning wheels), then it is directly proportional to engine/drivetrain efficiency.
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Who says it needs to run on fossil fuel? Alcohol runs just fine as a fuel in an internal combustion engine with little modification needed.
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Ethanol has only about 2/3 the energy density of gasoline, and methanol less than half. Whether you call that "running fine" depends on your point of view. And modification most certainly is required. The stoichiometric air/fuel ratio for alcohols is majorly different from that of gasoline. If using a carburetor you need to rejet, if electronic fuel injection you must remap the mixture in the ECU. Also, the requirements for seals in the fuel system is different.
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Fuel injected cars are quickly learn a new fuel map when the fuel changes.
Even 10+ year old cars do that to an extent. My turbo charged engine has two maps. There is the basic programmed map and a learnt one based on readings from the knock sensor, so it can handle fuel of varying octane ratings.
Gasoline, diesel, etc don't have to be Fossil Fuel (Score:2)
Put ALL effort into engines that don't use fossil fuel at all. Thanks.
Gasoline, diesel, etc don't have to be Fossil Fuels. We can make them with a biological process for example. These processes are basically carbon neutral since the carbon emitted during internal combustion recently came out of the atmosphere.
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That applies now.
The only reason it is not economically feasible is because it is so cheap to dig fossil fuels out of the ground.
Allegedly, we are now past peak oil, and the price of fossil fuels should start going up. Eventually it will be economical to produce synthetic hydrocarbon fuels using solar/nuclear/other power and either biomass or CO2 and water - either because the technology has improved, or the products have risen in value, or more likely, both.
Re:It won't work (Score:5, Insightful)
Trust me, I have a PhD in engineering.
Would you care to expand upon that? Or is this the scenario we are looking at below?
If an elderly but distinguished scientist says that something is possible, he is almost certainly right; but if he says that it is impossible, he is very probably wrong. -- Arthur C. Clarke [brainyquote.com]
Or perhaps we simply have a loose troll?
Re:It won't work (Score:5, Interesting)
Trust me, I have a PhD in engineering.
Would you care to expand upon that? Or is this the scenario we are looking at below?
I'm an engineer too, but without PhD. I don't know what he was thinking of (or even if he is an engineer at all), but I can say one major flaw that I noticed. The piston rings serves two functions and they only consider one.
The article deals with combustion, which is on top of the piston. It never mentions what is below, which is the piston rod and the crankshaft. The connection between those two needs to be well lubed, but the construction makes it really tricky to lube a "run away" bearing. The solution is to make an "oil fog", which sticks to everything, including the cylinder below the piston. When the piston moves downwards, the piston rings scrape off the oil from the cylinder and provides a clean surface for the combustion.
When running an engine with cracked piston rings, lube oil will start to enter the combustion. This will produce toxic black and foul smelling exhaust and the engine "will be burning oil". Even worse the oil burns badly and leaves behind soot, which will damage/block the valves. Some of it will stick to the cylinder wall and not be removed by the piston rings, which mean it ends up in the lube oil. The higher the amount of soot in the oil, the worse lubing ability it has. Eventually you have an engine with enough oil, but no lubing.
In short: no piston rings will destroy every valve and bearing in the entire engine and replacing it could be cheaper than repairing it.
I consider this to be a far more serious problem than anything the article mentions and I find it rather shady that they completely avoid this rather serious issue. It isn't like it is an unknown problem. If you run big engines like trains or ships, then you will periodically test the oil for soot (and other stuff related to other defects) to detect faulty piston rings before the engine is wrecked. Anybody working in the engine industry should know this.
How do you know? (Score:4, Interesting)
When running an engine with cracked piston rings, lube oil will start to enter the combustion. This will produce toxic black and foul smelling exhaust and the engine "will be burning oil".
You mention an engine where a specific feature, specifically the piston rings, has failed, so it's no surprise that it's operation would be undesirable. I will counter with 2 stroke and wankel/rotary engines, which burn oil by design. Burning oil isn't as much of a problem if you design for it.
The Australians are working on a design where the piston rings won't be necessary. It could end up that they need a new lube system for the piston rod/crankshaft, or it could end up being an insurmountable problem(for now). I like that they're looking into it though. It reminds me about how HD platter arms are suspended by air flow from the rotating platters. High enough pressures might cause the air to act more like a liquid.
Re:It won't work (Score:5, Insightful)
Trust me, I have a PhD in engineering.
Heh heh. Posting anonymously when resting your authority on the strength of your name rather than the validity of your argument. Have to feed the troll on this one.
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No Ph.D. here, but I used to was a mechanic.
TFA is not quite right. Piston ring friction is not the reason an engine needs a cooling system. Quite a lot of heat is produced by the combustion! So much so that the piston rings' are used to transfer heat from the top of the piston to the cylinder wall; typically pistons are made of aluminum alloys which melt around 2000 F. Combustion temps are much. much higher than that. If the metal piston ring didn't conduct heat, the piston would melt.
Solve that with
Re:It won't work (Score:4, Interesting)
Re:It won't work (Score:5, Funny)
How about Ceramic Engines ? (Score:5, Interesting)
From the TFA:
"... that an absolute seal isnâ(TM)t that important, and eliminating the friction generated by the rings on the cylinder wall can have far-reaching effects on engine design on the whole "
" ... that the whole thing is blowing a bunch of hot air?"
If they _ CAN _ use that bunch of hot air to form a seal, and achieve a drastic reduce of friction in between the piston ring and the bore itself, I feel that it's time for the return of the ceramic engine.
The chief reason why ceramic engine doesn't make it into the mainstream despite having had under research since the 1970's is that the friction in between the piston ring and the wall of the bore itself result in the wearoff of the ceramic material in the form of a pile up of fine ceramic dust inside the chamber.
If what the vendor said is proven to be true, then we should bring the ceramic engine back to the fore-front.
Re:How about Ceramic Engines ? (Score:4, Insightful)
Re:How about Ceramic Engines ? (Score:5, Informative)
What are the advantages of ceramic engines?
Heat resistance would allow the engine to run hotter, allowing more efficiency per the Carnot cycle. Difficulties include preventing your fuel from combusting early, how to lubricate at temperatures that will cause normal oils to smoke, etc...
There's some weirdness in that ceramics done right can be lighter than steel, and due to their hardness and not expanding/contracting as much tolerances can be tighter, perhaps even reducing the need for lubricants.
An engine that needs no cooling (Score:5, Interesting)
To add on to what user Firethorn has said, try imagine an engine that needs no cooling.
The very reason we need to COOL our engine because the metal that we use in our engine can withstand heat up to a certain limit, and beyond that, the engine starts to melt.
Ceramics don't have that problem. Some ceramic compounds can withstand thousands of degrees of heat (and for that they have been used as shields for the Space Shuttles) and they are excellent insulators !
Serious research has been carried out on ceramic engines since before 1970's, by almost all the developed countries (America, Europe, Japan) and prototype engines had been developed.
The main problem so far is that, unlike metal, ceramics are not as durable against friction. Very fine ceramic dusts will fall out as a result of the friction, and combined with the fuel, it become "sludge"-like, jamming up the chamber.
There are a lot of places inside an engine where there are frictions, but the MAIN place which friction takes place is in between the piston ring and the bore wall.
If what the TFA says is true - that they can manipulate the air to become a "force" and takes the place of the piston ring, which means, the friction in between the piston ring and the wall of the bore is gone, then, the number one problem facing the ceramic engine is solved !
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No need. If they're proper engineers, they read slashdot, comments included (especially if it's talking about their research).
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This also removes the piston-to-liner pathway as a way of cooling the piston head - the hardest part of an internal combustion engine to keep cool.
Re:It won't work (Score:4, Informative)
That has been solved for a while. Oil jet to to bottom of the piston. They have been doing that for a long time in racing and motorcycle engines.
Re:It won't work (Score:5, Insightful)
In place of the rings, each piston has numerous small, angled grooves, semi-circular at their apex. With the small clearances between them, the movement of the piston creates high-speed eddies -- air pressure working like metal rings to cut leakage and loss during the compression and combustion strokes.
“That means there’s no metal-to metal contact between the pistons or rotors and their mating cylinders or housings. Virtually no friction means the mechanism needs no lubrication and there’s no wear and tear on major components,” said Trigg.
There’s an important by-product here, too. Putting an “air cushion” around the periphery of the combustion chamber creates a stratified air-fuel charge – an injection profile that enriches the mixture in the centre of the chamber and leans it up towards the periphery.
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So will this mean that sleeve valves will be practical.
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'Knock' is detonation. The words you are looking for are 'piston slap'.
Re:TDC/BDC (Score:4, Informative)
'Knock' is detonation. The words you are looking for are 'piston slap'.
No, 'piston slap' is something different. It's what we do to people who quibble about terminology. ;)
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When I think of knock, I think of bad bearings, main or rod. Pre-ignition I call pinging. Different people have different terminologies, possible due to culture.
Re:It won't work - sure about that? (Score:2, Interesting)
I wouldn't dismiss this right away.
If the physical features on the piston provide resistance to gas flow along the piston/cylinder annulus similar to that provided by piston rings, they wouldn't need a close-fitting piston - therefore no expansion coefficient headaches. It may also be that the hydrodynamics tend to center the piston in the cylinder, which would reduce contact events and scuffing wear.
You could probably get a feasibility go/no check with a few weeks' worth of modeling. The resonance interact
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What the heck are you talking about? Piston rings are there to save money by not requiring precision honing of the bore and piston. If you select the materials correctly you have never needed piston rings.
Just about every model airplane engine now uses a piston with no rings, and it scales perfectly well. It's just a matter of how much it costs, and the cost has been prohibitive.
And yes, you do need to match the coefficients of expansion in some combinations of ma
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What ever happened to Coates International?
They're still there -- http://www.coatesengine.com/ [coatesengine.com]
But still no product on the market. I first read about them in a magazine back in about 1993. 20 years gone by and I can't buy a retrofit head for a 4-banger. Seems their patents should be about up.
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