here’s a serious question. Why the hell are we still using the same damned internal combustion engine? Why the hell can’t they use the double-linkage Atkinson cycle? I always read that there’s “issues with vibration and balance”, but are those really not solvable problems? Can’t they mount the engine on vibrational dampers or something? Or just add more cylinders but facing the other way to cancel out the vibration?
Or better yet a ROATRY engine that has a much larger expansion stroke than compression stroke. There are like a million obscure engine designs out there by independent inventors. I just can’t believe there isn’t some way to make an exaggerated (and thus extra-efficient) Atkinson cycle engine that gets over the balance/vibration problem.
I’m thinking that to make a more efficient engine, they’d have to make one where the compression stroke is like 25:1, like diesel, so it’d be like a diesel engine with the flash detonation, and then a power stroke of like 40:1. I know those are big numbers to work with and “fit” into the engine, but apparently it’s doable, as a double-linkage Atkinson cycle engine is no big deal, but it’s just that there’s issue with vibration and balance. So, like I said above, why is the vibration and balance such an unsolvable problem?
I guess the best answer is indirect: With more than two dozen makers all slugging it out for the same market, why do you suppose all of them use engines that are effectively identical? If another engine design were even slightly better in any respect, why wouldn’t it find a place in such a competitive market?
(I am ignoring the brief run of the Wankel, whose advantages largely went away once it required valves and smog compliance.)
This also brings up another point: why spend a great deal of time and effort on an incremental change to the internal combustion engine when there’s potentially greater payoffs to be had investing in hybrid or electric systems?
This phrase jumped out at me from the WP entry: “… was designed to avoid infringing certain patents covering Otto cycle engines.” Bingo; it’s one of ten million inventions, be it an engine, a light bulb, a wireline insulator, a pepper grinder, whatever designed solely from the premise “he had a good idea; how can I horn in on it?” It’s literally different for [patent] difference’s sake.
What’s being used in modern hybrid combos is less an Atkinson-cycle engine than standard Otto-cycle engines with the kind of highly variable valve timing that computer-controlled cams and roller rockers permit. I have a cam in a 1968 302 block that would have been nearly impossible to implement in the day; with computer-controlled grinding and roller tappets, it opens up almost 100 HP. My Odyssey has solenoid-controlled valves that adjust in ways cam profiles can’t and shut off three cylinders for highway cruising. (Absolutely indetectibly, I should note.)
But both are just Otto engines with mods, and while the Prius et al. might technically meet Atkinson cycle parameters, they are, too. Nice to see the idea have merit more than a century later, but the original design was still “different for different’s sake” and not really of much value except to makers who didn’t want to license Otto technology while it was under patent.
Tech history is shot through with such “almost” ideas… and their supporters who are convinced it was a superior approach crushed by Big _____.
There are other IC designs that in theory could be better than our old standard.
One potential reason you aren’t seeing them is a combination of two factors.
The better part is more incremental than revolutionary.
A mega buttload of money has been invested in the past hundred years making the old standard IC very damn good.
A slightly better engineering solution that has its issues and has had in comparison virtually no money invested in making it work is going to be a tough sell for investors that would have to compete with a very mature and entrenched current engineering solution.
Novel and better nuclear reactor designs suffer the same problem.
That’s true to a point, but between the many viable makers engines new-from-scratch have been designed many times, especially in the last 25 years or so. If there was any real merit to things like the Atkinson cycle, they would have incorporated it. It’s not some cycle of laziness and dull thinking, or a conspiracy by the Otto Illuminati… it’s that 100 years of optimal tech evolution and the fact that the alternatives were just that - alternatives, not really improvements - keep coming back to the same solution, even under today’s incredible demands. Adapting the best bits of the Atkinson idea to relatively conventional designs is an example of the whole process. A true historian of IC engines could no doubt list dozens, if not hundreds of little tweaks and improvements taken from nominally different designs.
the other thing is that many of these alternative engine designs have serious fundamental handicaps compared to a traditional 4-stroke Otto engine. The Wankel is a good example. It’s unique and interesting thanks to its high power-to-weight ratio, but there’s no getting around its fundamental thermodynamic problems. At the peak of the compression stroke, there’s simply too much combustion chamber surface area for heat to transfer to the cooling system. When a 3,000 lb, 230 hp Mazda RX-8 gets markedly worse fuel economy than a 3,700 lb, 420 hp Mustang, there’s a problem. The Wankel is great if you need a lot of power out of a small package, but not if you want an efficient powerplant.
The original Atkinson engine has the disadvantage of being far more complex than an Otto engine, and would need a lot more reciprocating/rotating mass to work. Which means the engines would be bulkier and slower-revving. Using variable-cam timing on a conventional engine (which is what everybody does with hybrids) gets you most of the benefits of the Atkinson cycle without most of the downsides.
diesel may be on the upswing now that they’re a lot quieter and it’s possible to get them to meet the same emissions standards as gas engines. Though the cost and complexity of the exhaust aftertreatment will have to be improved before they have a chance to really take off.
Some of the other wackier designs (Rand Cam, Orbital, etc) are novel but sealing and lubrication have been as yet an unsolvable problem.
They have. Like you said, the hybrids from Toyota, Ford, Hyundai and others is a “fake” Atkinson cycle, but it is “close enough” to get most of the benefits without all of the other complexity.
I keep hearing about “would have done this” 's ; that is, how if it were possible it would have already been invented, but like the above guy said
In general, industry works almost solely on already-existing technologies. There is very little venturing out into the unknown. 90% of all commerce is doing something that’s been done before. Don’t you guys find this generally to be true?
Which is why I was asking for scientific/technical reasons. Does anybody know specifically about this balancing problem? I know about Prius’ variable valve timing doing sort of an atkinson cycle, but my understanding is that the real deal (like delivered with a double linkage providing actually different sized cycles) is actually better
Make no mistake about it, a genuine Atkinson cycle with a double linkage is more efficient. One of the big companies is designing a new generator to sell that uses one - the vibration/balance problem obviously isn’t a problem if you’re bolted to the ground and only need to go one speed. Or at least it’s less of a problem
Note that the question is again if anybody knows about this balance /vibration problem
You’ve posed the problem though there’s only a tradeoff between efficiency and mechanical balance, but there are many more factors involved, such as power density, cost, and physical size. If someone is going to market with a multi-link Atkinson cycle engine for stationary power generation, then apparently the mechanical balance issues aren’t insurmountable. What about the other issues, though? The multi-link mechanism increases the physical size of the engine, which is going to make it more difficult to stuff under the hood of the average passenger car. It also increases cost, which is going to make it difficult to sell to most customers (a few are interested in reducing fuel consumption for political reasons, but most just want to save money). If power density goes down (on either a per unit-power or per unit-weight basis), that’s also unattractive.
“Just the extra double linkage”?? The stress on the linkage pivot is almost as great as on the crankshaft - so we’re essentially talking about an engine block with 3 crankshafts. And you have 2 connecting rods per piston, instead of the usual 1. Not only that, but you have the linkage rod itself, which must be much stronger (and heavier) than the connecting rods because it’s under torque (bending stress), not compression. Not to mention, you have 2 sets of all these per cylinder. That’s a huge amount of additional complexity.
Also, nothing is 100% rigid. Everything flexes. And any flex in the engine structure and the linkage rods result in loss of energy. Energy loss is especially bad in a back-and-forth motion - energy is lost on every cycle.
Any ways, to the OP: a better IC engine compared to what? They all burn in excess of 98% of their fuel, typically operate for a very long time with minimal maintenance, and work in a variety of environmental conditions with little modification. The only real drawback to them is that a significant amount of the energy is wasted as heat and that’s something that’s been continuously worked on.
Wait what?
OMG I think I understand what you’re talking about. I’m gonna come back to this later when I have more time and look at some diagrams and think about it visually again
Good point. Also look up the Commodore Amiga. Great computer, didn’t go much of anywhere because almost everyone else was standardizing on Wintel boxes. Same thing with the Macintosh in the mid-90’s. It was a good computer, but could have been a greater computer if more money had been thrown at it to improve its software library and market penetration.
And simple economics comes in to play with cars too. Most people want to get from Point A to Point B without spending a crapload of money. People trust their Toyota Camrys and Honda Accords that have been tuned and refined ten times over to be especially reliable. Sure, you might be able to pull out a Brazilian-made weirdo car that supposedly got 5% better mileage if you remember to refilter the transdynamic rod system every 50,000 miles. But who would buy it?
You are starting with a flawed hypothesis/observation. The IC engine has been improved and tweaked to an amazing extent. Modern IC engines are very powerful, efficient, clean, reliable and affordable. That’s not to say we won’t have an entirely new design someday, but it’s simply false to imply that current automobile engines are noticeably inferior to untested designs. People have been denigrating the “old, dirty” IC engine for decades, but significant improvements keep being made to it.
As regarding the rotary engine, not only is pollution a problem, so is energy use and torque. I seriously thought about an RX8, but the fuel mileage was horrible.
You may have heard that internal combustion engines are horribly inefficient. This is true. But they’re horribly inefficient for fundamental reasons: There’s a maximum possible efficiency for any heat engine called the Carnot limit, and modern car engines are actually reasonably close to that maximum. If you want to significantly increase the efficiency of an engine, your only option is to increase the temperature of combustion of the fuel, and if you can’t do that, you’re just nibbling around the edges of the problem. So, can these alternate designs you mention increase the temperature? By how much?
The only way that I know of to escape Carnot is the use of chemical energy, aka batteries. As this is no longer a “heat” based engine.
In theory, we could throw money into electric vehicles and then use nuclear plants to recharge them. As I think with any fossil based fuel, the efficiency is about the same… maybe with some synthetic fuels we can increase the efficiency?
