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Astonishing claims.... what do you think?

Astonishing claims.... what do you think?

RE: Astonishing claims.... what do you think?

Bullshit!

Firstly, modern conventional IC engines can exceed 40% which is much more than 15%

Second, the work done is is the related to the expansion ratio. It has absolutely ZERO relationship to what is going on under the piston other than friction loss.

Revetech marketed themselves on this some years ago. They were ambitious and built and tested an engine. Not much happened after the first official test.

https://en.m.wikipedia.org/wiki/Controlled_combust...

RE: Astonishing claims.... what do you think?

(OP)

Quote (TugboatEng)

Bullshit!

My thoughts exactly. The common "layman science" that compressed gasses are like muscles that waste energy by exerting themselves when the lever is in the "wrong" position is misguided. Engines run on gases, not muscles, and as long as they have good ring seal, there's very little lost efficiency resulting from holding pressure and expressing it as work later in the cycle. Their efficiency improvements are absurd at face value, and their suggestion that there's something wrong with thermodynamics because it doesn't support their claims is classic "layman science" mixed with a bit of anti-intellectualism. Their web site says: "Our vision is to reduce by 50%-100% the amount of carbon emission released into the atmosphere by a typical ICE's which improves the lives of everyone on the planet... But that goes against the laws of thermodynamics? I am pretty sure scientists and experts believed we couldn't fly, break the sound barrier or go in to space either but we did it anyways. In fact we seem to have new discoveries that go against old theories more often than not."


Quote (Greg Locock)

Revetec had the guts to get their engine tested by an outside company, and managed a none too shabby 38% when run lean

Revetec tested at numerous facilities and gained a lot of support. See https://fuel-efficient-vehicles.org/energy-news/?p...

What kills an engine that makes it so far through evaluation? I can think of only a a few:

1) Reliability. None of the tests appear to address endurance... perhaps it failed after 50,000 miles.
2) Bad business deal. They signed an agreement with a Turkish firm... perhaps it didn't expire if the licensee failed to commercialize.
3) Greed. Auto companies rarely license outside tech... perhaps they charged too much, or the auto companies just decided to wait out the patent.
4) Conspiracy. Maybe Big Oil worked through the Turkish firm to kill the engine... just kidding.

RE: Astonishing claims.... what do you think?

Yes I suspect durability in novel engines is often their Achilles Heel. Industry wide in automotive you don't have an engine that is worth developing unless it can do 100 hours at full power. This can happen as soon as the first attempt (Austin A+ series turbo) or months (LT5), or never (many diesel adaptations of petrol engines by BL).

Cheers

Greg Locock


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RE: Astonishing claims.... what do you think?

I don't think it's exactly bull shit but clearly needs some proper like for like testing.

As far as I can make out what this comprises is a piston rod which has a spring inside it so that when you reach max compression the piston stops moving, but allows the crankshaft to rotate from about 30 degrees BTDC to 30 degrees ATDC which is when you ignite the mixture with the crank angle a bit more in your favour.

I suspect though that this gives lower time per rpm for the fuel to burn so they end up reducing the fuel mixture / quantity.

Also as the mixture ignites the spring will get rapidly compressed to it full extent with a bit of shock loading going on.

You'll probably see failures after a fairly short time from this moving piston rod.

Would be good if it worked, but I just can't see it.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: Astonishing claims.... what do you think?

It is simpler than that. Like tugboat said - its all about what happens above the piston. Leverage, mechanical advantage and fancy mechanisms have no effect. There are slight effects due to changes in heat loss associated with time spent at various piston positions but nothing to do with the kinematics.

je suis charlie

RE: Astonishing claims.... what do you think?

Their website needs about as much proofreading as it does fact-checking.

RE: Astonishing claims.... what do you think?

A lot of engine inefficiency is due to the cooling jacket. If you could find a magic material that did not need to be cooled to keep it from melting. I read somewhere that if diesel engines did not need coolant they would be about 70% efficient instead of the usual 35% efficiency. This is plausible given that about 1/3rd of the fuel value in diesel fuel goes into heating the cooling jacket or air cooling fins. Back in 9th grade our school had an air cooled 1 cylinder diesel engine. Starting it with a hand pull cord was a b i t c h because it took multiple pulls to get the cylinder head warmed up enough for the engine to start and run. These were the kinds of engines that were used for temporary road signs.

I read back in the 1970s the Smokey Yunick was working on an engine that could work with cooling water or fins. It turns out that silicon carbide has 3 different solid states depending upon how it is heat treated. Only 1 of them acts as an abrasive. One of the solid states is easy to machine and another is very tough and easy to lubricate.

Could have also been that the article in Popular Mechanics was pure B.S.

RE: Astonishing claims.... what do you think?

(OP)

Quote (mc5w)

If you could find a magic material that did not need to be cooled to keep it from melting.
I went down that rabbit hole early on only to discover that the limitation is not the melting temperature (or reduced strength at temperature) of the metals but the breakdown temperature of the lubricating oil. Conventional oils are good to about 300F and mainstream synthetics are are good to around 400F (Krytox XH-1000 oil is among the best high temperature oils, but it sells for $150 per ounce. See https://www.grainger.com/product/KRYTOX-Oil-35RV61 ). Beyond breakdown temperature, the oil rapidly degrades and soon fails to lubricate properly. Thus, one can make an "adiabatic engine" that runs at very high temperatures long enough to capture some impressive efficiency numbers, but it won't run for long after the lubricating oil breaks down. There have been efforts to make engines that don't require lubricants and can thus operate at much higher temperatures, but they required extremely costly materials and didn't yield efficiency gains as high as hoped for.

Bottom line: engine designers have known for well over a century that they were losing efficiency to the cooling system, and many attempts at eliminate those losses have been made. The few successes require exotic and costly materials, and the gains weren't as high as expected because higher temperature degrades performance in some portions of the cycle. Engine design is like whack-a-mole.

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