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LiquidPiston – The combustion engine reimagined
- canbus 3y agohmmm.. still uses apex seals, would need seriously small tolerances to make it work effectively. Call me skeptical but I don't see how this is really any better than the traditional wankel/rotary design
- stefncb 3y agoIt's effectively an inside-out wankel, so the seals are stationary. This is a much easier problem to solve, and now you don't need to throw oil in the combustion chamber to lubricate the moving seals.
- drcongo 3y agoThanks both, I'm not very mechanical and came to the comments to find out what makes this not a wankel.
- 2-718-281-828 3y agoto me it still looks like its principally a wankel motor just with a few changes.
- stefncb 3y agoIf you look at an image, you can see the three apex seals on the stator, which is shaped the same way as a wankel rotor. The rotor of the liquidpiston engine is shaped similarly to the wankel stator and has no seals. It's almost the same just turned inside-out.
- 2-718-281-828 3y agotrue - now i see it.
- canbus 3y agoright, but any float in the main eccentric shaft is still going to wear them out
- ilyt 3y agoYeah but "just replacing $50 seal every few years" is smaller problem than "taking apart whole engine to replace the $50 seal". And now they can technically be directly oiled instead of whole oil in petrol thing.
- 2-718-281-828 3y agoproblem one will be balancing forces if combustion is taking place on one side. also i don't see why this should be burning less oil. you are smearing the oil constantly around.
- stefncb 3y agoThis isn't all that different from a four stroke, at some level. With a piston engine you lubricate from below, the oil never getting above the rings. Practically some does and gets burned away, but that's negligible usually. Anyway, the seals on the liquidpiston engine supposedly do the same, keeping the oil from leaking around the seals (in a significant quantity anyway; I'm sure it's higher than a four stroke though). Here's what their webpage says: > The seals do not experience centrifugal forces, and can be lubricated directly by metering small amounts of oil directly to the sealing surface through the housings, which means that oil consumption can be reduced to levels potentially comparable to that of a 4-stroke piston engine (essentially negligible). Obviously take all this with a grain of salt. I haven't read any practical studies on this.
- chipsa 3y agoIt inverts where the apex seal goes. So instead of having it on the rotor, and hard to lubricate, it goes on the housing, which is much easier to lubricate.
- TheCondor 3y agoSmall, multi-fuel, engines do have interesting applications. I tend to agree though. The other big thing, these rotary engines have traditionally had poor combustion. Direct injection and turbulent jet ignition have focused on improving combustion efficiency and made tremendous gains. I’m not sure how liquidpiston addresses that, especially with the fuel claims. Traditionally you’d add fuel additives to help with combustion efficiency.
- toss1 3y agoYou are right - it is not better - not even close. It is 2-4X WORSE on Liquid Piston's main advertised claim to fame "lightweight" "power/weight" than many available actual Wankel engines. And the fact that this is still in development a decade+ later and 7-8 years after I was first vetting them for a hybrid multirotor drone company indicates that your suggestion is correct — they have many nagging and serious not-easily-solved problems.
- ilyt 3y agoWell, they are on outside. Which means possible way to replace it without tearing the engine apart. And we did get better at making them. And they could possibly even be oiled directly from there. But the fact companies make normal wankel engines that are better at everything is worrying for them
- rjmunro 3y ago> Hydrogen may be generated by renewable sources such as solar energy, making it overall a cleaner alternative than batteries on a well to wheel basis Err, what? I guess you could contrive a scenario in which the extra solar panels and equipment needed for generating, managing and storing the hydrogen was less "well" than the batteries for equivalent "wheel" output. Perhaps if you make infrequent but long journeys, so you need a big battery, but only a small amount of power generation, but hydrogen is a very inefficient way of storing electrical power, maybe 50% of the energy back compared to over 90% with batteries.
- pfdietz 3y agoRight. Hydrogen only makes sense for leveling over very long periods, and then only when the capital cost of the hydrogen storage tank is low enough (for example, storing it underground like natural gas is stored) so this can overwhelm the "cost of inefficiency".
- kitd 3y agoVideo describing the engine: https://www.youtube.com/watch?v=0e785YnDmq0 https://www.youtube.com/watch?v=0e785YnDmq0
- xnx 3y agoPosts on Hacker News related to LiquidPiston go back 11(!) years. The most comments are on this post: https://news.ycombinator.com/item?id=25450477 https://news.ycombinator.com/item?id=25450477 If this was going to revolutionize anything, it would've happened by now.
- Cthulhu_ 3y agoI think any engine design that was popularized was backed by a car company, even the Wankel engine. If they want to make this design popular, they need to design products around it so their claims are proven. I mean I still don't believe Tesla's primary business model is cars; the competition is outselling them left right and center. Theirs is batteries and charging infrastructure. That's a huge market that can fuel the company for a century if they play their cards right.
- 7jjjjjjj 3y agoTesla doesn't make their batteries, they buy them from Panasonic.
- dreamcompiler 3y agoIf you have evidence that Tesla doesn't make batteries, perhaps you should alert their shareholders that the company is lying on this page: https://www.tesla.com/giga-nevada https://www.tesla.com/giga-nevada
- ngvrnd 3y agocells are not the same thing as batteries; it's possible tesla is making batteries with cells from Panasonic or whatever.
- taylodl 3y agoYou're both right. Tesla doesn't make battery cells, they make battery packs. A battery pack is comprised of several battery cells, for example the Model Y has over 4,000 cells in its battery pack.
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- obituary_latte 3y agoUnless they are getting some miraculous increase in efficiency compared to any other Wankel engine (see Mazda), I don't see the value add here. It's essentially just a different way to do what the Wankel does with a few differences (apex seal placement, rotor shape and function).
- toss1 3y agoThey are not. There are many available actual Wankels in multiple sizes and power outputs. They ALL provide far better power-weight ratios — like 2.4X better — than this still-in-development-after-a-decade+ 'product'. More details in other post.
- 0x445442 3y agoThe video on the main page had me until they said their main focus now was on helping the U.S. empire's attempts to subjugate the rest of the world. If small form factors were a focus, how about off grid generators or the like. Leading with military applications does not inspire IMHO.
- UncleEntity 3y ago> If small form factors were a focus, how about off grid generators or the like. Which is probably why the military is interested in it. If it runs on diesel all the better as they have pretty much standardized on JP8 for all their subjugation needs.
- lebuffon 3y agoLegacy technology always "improves" when a serious disruptor enters the market. It seldom can overcome the disruption for very long. However this engine seems to be a great improvement on pistons if we want to continue burning dinosaur juice. It might be interesting to try it as a range extender for long-haul electric trucks due the smaller size and weight.
- linuxftw 3y agoOn the one hand, it seems like they have an addressable market. On the other hand, it seems like a scam because they're trying to attract investors with a fancy web page and thin statements about where they're actually selling. The comparison to a 25HP Kholer on the main page is... something. Here's the 'brochure': https://uploads-ssl.webflow.com/5f6086e9bbbabd41a20f2984/6427fdcf5c4c4c3d073e9bc4_LPI%20Brochure%2020230331.pdf https://uploads-ssl.webflow.com/5f6086e9bbbabd41a20f2984/642... Less than half the torque at more than double the RPMs. And very low compression, I don't see how this can run diesel.
- ilyt 3y ago> Less than half the torque at more than double the RPMs. I mean if you double RPM you halve the torque at same power, dunno what's weird here ? It's smaller CC faster rotating engine. > And very low compression, I don't see how this can run diesel. I'm also on "show us the working engine" side but supercharger will also add some heat and pressure to the system it might work?
- linuxftw 3y agoThey're comparing a small engine to a 25HP diesel engine. A 25HP diesel is what powers my tractor, they're really not in the same class as a small 25HP gasoline engine that powers my lawnmower. If we're comparing the usefulness of an engine, torque is a big part of the equation. If they can get a small diesel engine for light load applications like generators or small aircraft, that might be a win so the military doesn't have to bring a different type of fuel (gas) or a heavier diesel engine. But I'm not sure 8:1 compression ratio is enough to operate the diesel cycle.
- ilyt 3y ago>They're comparing a small engine to a 25HP diesel engine. A 25HP diesel is what powers my tractor, they're really not in the same class as a small 25HP gasoline engine that powers my lawnmower. Their comparison was essentially for mostly-constant RPM usage (generators,UAVs), rather than something more dynamic. Which means they can just peg the engine at most efficient point, just like Mazda's range extender wankel. So yeah, not for tractor-like usages. > If we're comparing the usefulness of an engine, torque is a big part of the equation. No, torque on its own is not, else you could compensate with gearing. Power (and in relation, torque) curve is the important one. The "tractor" like uses want "constant power" across the range, which essentially means flat-ish power curve across whole range[1], and that means torque is dropping fast with RPM. This "theoretical" one liquid piston one is probably classical high-revver curve which is near-constant torque across most of the range and very small range of peak power. Just the torque number tells very little about that, you need a graph. * [1] https://www.darksidedevelopments.co.uk/Blog/reading-a-dyno-graph/ https://www.darksidedevelopments.co.uk/Blog/reading-a-dyno-g...
- zokier 3y agoApparently they have 210cc 25hp engine available.. is there any reason someone (or they themselves) couldn't throw that into a bike to see how it performs in real-world? There are plenty of 250-300cc bikes around with comparable power ratings, so you'd think it'd be feasible project and a bike sounds much simpler than car/aircraft/etc
- ilyt 3y agoWell, if you want Wankel in your bike... https://www.aieuk.com/225cs-40bhp-wankel-rotary-engine/ https://www.aieuk.com/225cs-40bhp-wankel-rotary-engine/
- cwmma 3y agoThis is basically a variant of the Wankel engine, and if you do a cursory view of the Wankel engine wikipeida page it paints a pretty clear picture of a theoretically better engine that ends up not performing as well as standard engines due to a 1000 little things like the seals, ignition and chamber shape that have been perfected over the century + of normal engine designs. This engine is going to have all those problems and more preventing it from being as good as a regular engine in practice.
- ilyt 3y agoIt does solve few of them, althought it doesn't look it will be easy to scale to more than one engine. For example the apex seals being on "the outside" instead of on the rotating assembly means they could be made easier to replace and easier to oil too. But yeah, improvements look not all that big, certainly not revolution