Interesting take on the combustion engine - LiquidPiston - Page 1
Forum section: electronics / general

author: daqq
author_rank: Super Contributor
timestamp: February 15, 2021, 07:48:12 pm
content: They claim that they are 30% more efficient and 10x more power dense than the competition. While this does raise a few alarms in my head, they seem pretty serious and they seem to work:https://www.liquidpiston.com/I don't have enough knowledge on the matter to judge whether this sort of thing is fishy.

author: RoGeorge
author_rank: Super Contributor
timestamp: February 15, 2021, 08:10:58 pm
content: Looks like some sort of Wankel engine to me (not a mechanic).https://en.wikipedia.org/wiki/Wankel_engineHowever, the level of bullshit and fluffy words in those videos raised me a flag. I couldn't bare it, skipped through the two videos without sound, sorry. Same about the musical background. Cringe advertising like one would need to do for a scam, not saying it's a scam just that it looks like one, maybe they just hired a really bad advertising team.I would be very cautious, and go there to see and test the engine myself before investing.

author: Benta
author_rank: Super Contributor
timestamp: February 15, 2021, 09:05:23 pm
content: "Inverse" Wankel. Has exactly the same same thermodynamic issues. Certainly not my choice when buying stock. And ICEs are slowly dying anyway.I'd call it a "conversation piece".

author: Stray Electron
author_rank: Super Contributor
timestamp: February 15, 2021, 09:44:31 pm
content: Quote from: RoGeorge on February 15, 2021, 08:10:58 pmIt's still a Wankel engine and will suffer from all of the problems of a Wankel engine. The high speed at the tips of the rotor will cause rapid seal wear and wear of the interior of the engine block (the equivalent of the cylinder bore in a normal piston engine). That wear will cause exhaust leaks and dilation of the intake fuel-air mixture which will get worse with time. Both of those will cause emissions issues and will prevent it from being approved in most countries. Among other things, Wankels are basically like a 2 stroke engine in that they don't have a separate crank case and combustion chamber so they need to have oil added to the fuel mixture, either manually or via an injection system. The oil is consumed in the combustion and that will cause even more hydrocarbon emissions.This MIGHT be a good engine but it will never be approved for production in any modern country due to emissions problems. A good modern piston IC engine can easily run for 250,000 miles but no Wankel has ever come close to that due to the oiling and the wear problems.

author: hans
author_rank: Super Contributor
timestamp: February 15, 2021, 10:25:12 pm
content: The 'how it works' page states: "While it is a rotary engine, LiquidPiston’s X Engine is NOT a Wankel engine. It has a fundamentally different thermodynamic cycle, architecture and operation."But it doesn't really state what is revolutionary. And when I hear rotary engine, I immediately think about sport car engines like the Mazda RX-8. Great for a fun car with smooth power delivery, but it needs tons of revs to perform (some RX-8 engines deliver peak torque at 5.5k rpm and power at 8.5k rpm) and are not economical at all (and thereby efficient).I'm sure it can live up to the compactness factor to some degree; because it basically fits 3 cilinders around a rotating cilinder+crankshaft. One issue I think however is the geometry. If you decide to build a larger engine (e.g. 1.5L for a road car), you need to fit 3 large cilinders. The way those inlet/outlets are drawn makes it harder to build a 2-rotor design. The only way is to then go out in width/height, which is unpractical. It also needs a good bearing and seal between gasses and the crankshaft.I believe the RX-8 wankel engine is also loved because you can mod it to a 3/4-rotor rebuilt design. AFAIK you can even reuse many parts of the original 2-rotor design, as it's quite a modular block.

author: nctnico
author_rank: Super Contributor
timestamp: February 16, 2021, 04:13:14 pm
content: Quote from: Stray Electron on February 15, 2021, 09:44:31 pmI'm not quite sure this concept qualifies as a wankel engine because it is very different and there are 3 burns during one rotation. It looks more like a rotary engine which uses the Atkinson cycle. But you are right about the potential problems with getting the rotor sealed. If this where such a good invention then car makers would have jumped on it long ago.

author: richard.cs
author_rank: Super Contributor
timestamp: February 16, 2021, 04:54:05 pm
content: Is the "liquid" just some marketing name? I was expecting something like thishttps://en.wikipedia.org/wiki/Humphrey_pump

author: tom66
author_rank: Super Contributor
timestamp: February 16, 2021, 05:46:52 pm
content: I don't know why anyone would try to create a startup company to market a new ICE, the technology is dying.Sure, it will still be around for another 15-20 years, but the applications for this product look to be at low power levels (go karts, power tools, etc.) where already electric motors and batteries are competitive -- it looks like an increasingly small portion of the market and not necessarily a better solution (it's more efficient but who measures the efficiency of their weed-whacker? Is the fuel even a significant cost?)

author: nctnico
author_rank: Super Contributor
timestamp: February 16, 2021, 06:23:43 pm
content: Quote from: tom66 on February 16, 2021, 05:46:52 pmNot at all. Look for the KPMG 'automotive outlook 2020' report. It says that in 2050 (about 30 years from now!) 75% to 85% of the cars sold will still have an internal combustion engine. With ever tighter emission regulations and need for higher efficiency it still pays of to invest in ICE technology.

author: David Hess
author_rank: Super Contributor
timestamp: February 16, 2021, 09:16:45 pm
content: Quote from: Stray Electron on February 15, 2021, 09:44:31 pmIt is only a Wankel engine in the sense that the rotor and stator are swapped, so in this design, the seals are stationary allowing them to be continuously lubricated.

author: tom66
author_rank: Super Contributor
timestamp: February 16, 2021, 09:25:04 pm
content: Quote from: nctnico on February 16, 2021, 06:23:43 pmThat would surprise me. Perhaps if they're counting developing nations, but most European nations have committed to eliminating the ICE by 2030-2040. Whether they hit their targets is another matter, but automakers seem to be aiming this way.

author: Sal Ammoniac
author_rank: Super Contributor
timestamp: February 16, 2021, 10:52:34 pm
content: It's always amazed me how well modern IC engines work considering the large number of moving parts that all need to operate in a coordinated fashion. I guess that's a result of over a century of development. Contrast that to electric motors, which have a single moving part and are far far simpler than IC engines.

author: retrolefty
author_rank: Super Contributor
timestamp: February 17, 2021, 01:20:05 am
content: Quote from: Sal Ammoniac on February 16, 2021, 10:52:34 pmThere was never a question of the superiority of electric motors over ICE engines. The problem was/is the power density of the energy sources used.

author: tom66
author_rank: Super Contributor
timestamp: February 17, 2021, 08:45:52 am
content: Quote from: Sal Ammoniac on February 16, 2021, 10:52:34 pmI think it's worth putting in perspective though.An average car might do say 250,000 miles before the ICE needs a serious rebuild. If that car did an average speed of 40 mph - a mix of highway and city driving, say, that's a runtime of about 6,000 hours.It's not uncommon for machines to exceed that so in some senses you could ask why do ICE vehicles require such regular servicing and have a relatively short lifespan in comparison to e.g. an industrial machine that may last 10 years continuous use (2 x 8 hrs shifts per day) before major rebuilds - that's 58,000 hours.Of course given cars are generally used on short duty cycles (pre-COVID the average car still spent about 90% of its time parked up) it doesn't matter so much that their lifespan is perhaps 'comparably' short.

author: KE5FX
author_rank: Super Contributor
timestamp: February 17, 2021, 08:55:12 am
content: Quote from: nctnico on February 16, 2021, 06:23:43 pmInteresting. Where do they expect those cars to be sold? It won't be to the US, the UK, Europe, or probably even China by that point.

author: nctnico
author_rank: Super Contributor
timestamp: February 17, 2021, 09:32:28 am
content: Quote from: KE5FX on February 17, 2021, 08:55:12 amYes it will. Politicians count ICE hybrids as electric cars as well. Car makers say they will switch to BEVs but they know very well that it just isn't affordable / financially interesting for everyone.One of the problems car makers are facing is that small 3 cylinder engines vibrate a lot which reduces the comfort. The rotary design of LiquidPiston could be interesting to car makers to have a compact engine that doesn't vibrate so much. A power output in the 50kW to 90kW range is enough for a hybrid drive system in a passenger car.

author: Circlotron
author_rank: Super Contributor
timestamp: February 17, 2021, 11:21:40 am
content: Poor surface to volume ratio in the combustion chamber which makes for high unburned hydrocarbons emission, just like a Wankel. Might be interesting running on hydrogen though. No HC.

author: DenzilPenberthy
author_rank: Frequent Contributor
timestamp: February 17, 2021, 12:46:15 pm
content: Quote from: tom66 on February 16, 2021, 05:46:52 pmThis is definitely in the same category as someone pouring resources into breeding better carthorses in 1900, or developing new thermionic valves in the late 50s. Utterly bonkers.

author: nctnico
author_rank: Super Contributor
timestamp: February 17, 2021, 04:15:18 pm
content: Quote from: Circlotron on February 17, 2021, 11:21:40 amIf you look closely at the video you'll see that that isn't the case. The claim is that it is opposite of the Wankel engine. If you look at the video you'll see that the burn chamber is closed off by the rotor giving a well defined (small) space in which the burn occurs.

author: Benta
author_rank: Super Contributor
timestamp: February 17, 2021, 06:04:39 pm
content: Quote from: nctnico on February 17, 2021, 04:15:18 pmSo put your money where your mouth is: buy some shares.I'll refrain.

author: nctnico
author_rank: Super Contributor
timestamp: February 17, 2021, 06:34:07 pm
content: Quote from: Benta on February 17, 2021, 06:04:39 pmWhy would I do that? It is just an interesting concept from a technical point of view.

author: Benta
author_rank: Super Contributor
timestamp: February 17, 2021, 07:38:46 pm
content: It's about as interesting as an over-unity machine.

author: KE5FX
author_rank: Super Contributor
timestamp: February 18, 2021, 08:37:46 am
content: Quote from: nctnico on February 17, 2021, 09:32:28 amI don't think so. In the UK, for instance, they're talking about a cutoff date of 2030 for conventional vehicles and2035 for hybrids.By 2050, gasoline-powered passenger cars will be as common as horses are today. Strictly an item for wealthy hobbyists and a very few specialists. It's crazy to put any money into R&D of gasoline-powered engines at this point. It's so pointless that it almost has to be a scam. If KPMG disagrees, well.... we'll see, I guess.

author: tautech
author_rank: Super Contributor
timestamp: February 18, 2021, 09:15:31 am
content: LP has the advantage of great power density that's apparently even better than traditional NA rotarys however it's not clear if they have obtained an even reasonable operational lifetime from the LP design although if they are making that diesel version and with the compression ratios required for self combustion they need be reasonably strong.From the promotional blurb it seems they can upsize the single rotor design to 1000hp so the need for a multi rotor design like the Mazda rotarys is apparently unnecessary.Wonder if they respond well to turbocharging like the Mazdas ?

author: nctnico
author_rank: Super Contributor
timestamp: February 18, 2021, 01:15:02 pm
content: Quote from: KE5FX on February 18, 2021, 08:37:46 amSeeing is believing. Nothing is cast in stone. There is a move towards the political right in Europe where the climate skeptics &deniers reside as well. In the end moving to new ways of transportation need to be affordable for the public and (unfortunately) the left parties fail misserably to show how to achieve that. Trump's 'Climexit' may not be the last one we see. In the end it is up to the voters.

author: coppice
author_rank: Super Contributor
timestamp: February 18, 2021, 01:38:59 pm
content: Quote from: Stray Electron on February 15, 2021, 09:44:31 pmThat's not accurate. When Wankel engines are run at a fairly steady high speed they can last 250k miles. The old NSU RO80, which was notorious for poor life in most applications, had an excellent life when used as a motorway cruiser by limo services. The problem is few people spend 90% of their miles at a steady high speed on fast highways. Wankel engines just chatter too much when they aren't spinning fast enough. The demo applications for this new engine seem to be flight and electrical generation. Both of those keep the engine at a steady speed.