Liquid Piston HEHC-Rotary out of the Dyno for first time.

Mauller

Mauller

Mauller

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Edit2 - info on the engine can be found here. http://liquidpiston.com/
edit 3- they blocked and removed the videos i had linked, so i have removed the links :(
Edit 4 - Added links from their site instead.
Edit 5 - Videos are back with engine construction and gokart :D
Edit 6 - Added some more info from an interview here http://jalopnik.com/tiny-rotary-engine-thats-not-a-wankel-powers-go-kart-fo-1781988639 220hp for 1.2L single rotor engine is fantastic for its size. :O
Edit 7 - Re added Gocart video they removed from a month ago.
Edit 8 - 70cc X-mini heavy-fuel prototype video showing 14:1 compression ignition https://vimeo.com/172430180

Vimeo video of gocart and how the x-mini engine works. https://vimeo.com/164412266

Youtube videos of gokart



Dyno test https://vimeo.com/99002635
How it works https://vimeo.com/163543761

If people have not seen it before, it is a new concept engine. It combines the best parts of the Otto, Diesel and Atkinson engine cycles into a lighter and more efficient engine.

It is a new type of rotary, but it is not a Wankel rotary, it is something new.

This thing has a combined 70cc, although it has 3x 23.3cc chambers. They consider it 70cc since it performs 3 combustion per rotation, giving It some decent power for its size.

you can find out more on liquidpiston.com, it is pretty interesting how this could turn out. they have already gained a contract with DARPA for this.

The X Mini is a gasoline-powered 70 cc engine with a 4-pound core that fits in a 6.6” x 6.2” x 5.4” box, making it 30% smaller and lighter than comparable four-stroke piston engines. The spark-ignited engine only has two moving parts and has shown high power density, producing 3.5 HP (indicated at 10,000 RPM). The engine weighs just four pounds and produces over 5 HP at up to 15,000 RPM.
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The engine architecture is inherently scalable from 1hp to 1000hp. They can scale the engine by increasing the size of the rotor (width / diameter) and also by stacking multiple rotors together (so each rotor balances the other, much like the Mazda rotary design). In a multi-rotor design, each rotor behalves like a 3-cylinder 4-stroke engine. LiquidPiston’s first ‘X’ engine prototype was larger, at 1.2L (up to 220HP), and operated on Diesel in true Compression Ignition mode. The 70cc X-mini is now relatively far advanced in its development, but the initial 1.2L X1 Alpha prototype demonstrates the breadth of the technology.

However, LiquidPiston’s primary long-term goal is for the engine to serve as a range-extension for Electric Vehicles. Consider the auto-maker that can provide an EV that has 30 miles of electric range - sufficient to cover 90% of a user’s daily driving needs. Such a battery pack would be small, light, and cheaper. Our X4 engine (currently a concept) will provide 30kW of power on Diesel fuel, in a package that weighs just 30 pounds, and fits in a 10x8x8" box. If configured as a range extender for the EV, such an engine can be used to power a generator that would charge the EV batteries, extending the range to 300 miles that drivers are accustomed to - while also enabling the driver to refuel at any gas station, much like they do today (no planning through charging way points required).

Not only is this a win-win combination for auto makers and drivers, but perhaps most interestingly - the X4 engine is envisioned to have better fuel economy than a heavy duty diesel truck; as such, charging the battery with Diesel will actually have a lower CO2 footprint, as compared to charging the EV on the U.S. power grid. It is sometimes forgotten that the US power grid actually burns coal and gas to supply a significant amount of energy, and the transmission / distribution network is not very efficient. Generating the power right at the point of consumption can change this.
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one of the naturally aspirated Diesel prototypes that produced 40hp at light load compared to a 35hp piston diesel. The part produced up to 220hp from what a different source says.
LiquidPiston-X2Engine-Comparison.jpg
 
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acemastr said:
Sounds cool, 3hp from '70cc' isn't wonderful though
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It is still a prototype, they are making it lighter and with >5 HP for the 70cc model, they already have a 40hp model that is far smaller than an equivalent diesel engine. All naturally aspired.

Although for the 70cc model, 3hp while it has 23cc per chamber is pretty decent for its size.

delta0 said:
I thought Wankel was 2x equivalent because it has 2 power pulses per crankshaft rotation. That makes it 2.6l equivalent for the RX8.
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Yeah, i just double checked and altered things. The 3x the chamber volume thing is still true, but from what i could find it is just one combustion per crank rotation. but that could vary depending on model and engine size.

This is a slightly interesting read on the matter. http://www.hemmings.com/magazine/hsx/2008/04/How-Big-Are-Wankel-Engines-/1610620.html
 
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delta0 said:
I just verified the exact number and the rotary is 3 pulses per rotor rotation and 1 pulse per eccentric shaft rotation. A piston engine only does 1 pulse per 2 rotations so the Wankel has 2x more pulses and hence is equivalent to a piston engine with twice the capacity. A 1.3L Wankel becomes a 2.6L equivalent.
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Yeah, makes sense when comparing to a piston engine. But likewise if you consider the engines displacement, the wankel is 3x that of what it is rated. Considering a single rotation of the rotor compared to a stroke of the reciprocating engine. The displacement would then be 7.8L, you can see why they decided to go by an equivalent displacement based on the eccentric shaft rotation compared to a reciprocating engine.
 
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Just a new bit of info, but this thing is 19cc per chamber on the intake stroke, 23cc per chamber on the expansion.

It over-expands the gasses back to near atmospheric pressure to achieve higher efficiency like with the Atkinson cycle.

So it is only 57cc for 3-5 HP on the intake volume.
 
Dogbreath said:
Looks like it will have similar rotor sealing challenges as a Wankel engine, and the inlet going through the "crank" doesn't look great for gas flow. I hope it does come to something, but many derivative four stroke engine designs have fallen by the wayside.
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No seal issues or incomplete combustion as with the wankel, the seals are on the body rather than the rotor.

This engine compresses and combusts at constant volume. The issue with combustion in the wankel, is that the flame has a very large area to pass over so fuel is often left unburnt. And with the seals being on the rotor in a wankel, the seals are always being forced away from the rotor.
 
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Dogbreath said:
Makes no real difference, it's still a very awkward shape to seal compared to a round cylinder and piston, and you still have to seal the sides of the rotor so the challenges are pretty similar. What about cylinder lubrication, still total loss?

It hopefully fixes the large temperature gradients seen on the wankel due to the single combustion chamber, so that should help with sealing.

It does appear to fix the long flame path with a much nicer combustion chamber shape, but as soon as the rotor starts moving it presents the same "wedge" shapes at the sides of the combustion chamber which presents a lot of surface area to a small volume of gas.

The large expansion ratio is a major bonus of the design.



You want to seal to be forced away from the rotor, onto the housing, they won't do much sealing otherwise. Or did you mean something else?

How are you involved with this BTW?
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Just a physics undergrad with an interest in things like this.

The issue with the seals is that they are forced away from the rotor with more force than is required to seal the chamber. So they require far more lubricant than is required for fixed seals. An issue with earlier Wankel engines was seal failure as they would pop out of their housings. But with the liquid piston design the seals are fixed to the walls of the chamber and do not need to deal with the same forces the seals in a wankel engine does. They also do not need to deal with as much pressure from the air/fuel mixture due to their positioning. This means the seals can be lubricated with the right amount of lubricant required without it needing to be sprayed into the engine with the fuel.

It does fix the large temperature gradient as all 4 parts of the combustion cycle occur in the same 3 chambers. Unlike with the Wankel where it occurs in different places within the rotor housing.

The face sealing is not as much of an issue for the reason you stated, that compared to the Wankel this does not have a hot spot issue in the design. So it does mean that the rotor and seals can work within larger tolerances compared to the Wankel. As the design is not subject to uneven expansion.

They have also taken into account skipping cycles on different parts of the cylinder to allow it to cool for a cycle if required. But they also have designs for fixed installations or longer term situations where water can be fed into a cylinder between combustion cycles to take advantage of the heat and provide a Rankine cycle between combustion cycles. Further improving efficiency.

Also compared to the Wankel the flame front still passes over a smaller surface, but the rotor also keeps the fuel compressed at a constant volume for a longer period compared to the Wankel which is a huge bonus.
 
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Updated initial post with new gokart video

Pretty awesome thing, under half the power than the original engine but at 1/10th the weight. :D
But that is 6.5HP/3600rpm from 200cc compared to 3hp/10k rpm from 70cc :D

Also added some new info from a few articles that were released today.
 
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Diddums said:
I'm really struggling to get excited about this, and I love new engineering designs and disruptive technologies.

This just seems way to complicated for very little return.

Good luck to the developers but I can't see this evolving past a hobby project sadly. Hopefully I'm wrong.
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They already have 2 Million + in funding from DARPA.
 
rhyswt said:
Am I right in thinking that they are using ram air cooling through the rotor? If so they will face the same challenges as the air-cooled-rotor Wankel engines.

There is a reason that their working engine is only a 3 horse power unit, it will most likely cook itself in a larger unit without masses of air flow.

I find the new combustion cycle interesting but this is nothing new, there are many "new cycles" out there that look great on paper, but translating that into a working prototype that has any amount of durability is a different story.

Good luck to them anyway, they seem to be publicising it well (just hope they are in it for the long haul, rather than just the investment opportunities).
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They have already tested it and compared to petrol, diesel and other engines, it pretty much runs within a few percentage difference to the theoretical cycle.

it also runs far cooler compared to a normal petrol engines since the over expansion on the exhaust cycle helps to extract more energy from the fuel rather than it being wasted as heat.

each combustion chamber is only 23cc and there are three of them and all three have a combustion every cycle. it gets 3HP at 10k rpm and 5 at 15k while being 1/10th the weight of a comparable engine.

The diesel prototype was also an early proof of concept engine that ran far better than expected. And was only ever run over short periods, that is why it has no cooling system built in.
 
rhyswt said:
Any more sources for further reading? I have many questions I can't see answers to on their website :D

Are they taking the exhaust gas back through the rotor? Any details on the lubrication system?
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From the videos that i have seen there is over expansion on the exhaust but no exhaust gas recovery. i assume they don't need to factor it in with how clean the exhaust is. There was an earlier video that demonstrated the exhaust from the engine and there was no vapour or smoke from it, visibly it didn't even look like the engine was running.

Nothing that i can see about lubrication, but there was talk about only having to apply the right amount of lubricant to the chamber seals.
 
Dogbreath said:
Simply because people have been looking for 150 years and despite a huge number of attempts nothing so far has proven competitive in all areas. Many designs have promised to deliver better efficiency, lower emissions etc. but are almost always dogged by size/complexity/manufacturability/longevity/reliability issues.

I suspect Mazda spent an awful lot more money developing the Wankel engine than this one (so far at least) and that was hardly the saviour of the ICE.

There's always going to be water vapour in the exhaust of an ICE burning fuels containing hydrogen, and the exhaust of a correctly tuned conventional four stroke engine is also invisible.

I don't want to come across as negative because I truly hope that something like this can provide the boost in efficiency that ICEs need, but expectations need to be realistic.
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of course, it is just a matter that the exhaust overall is cleaner etc, where as a lot of engines are not perfectly tuned so you often see exhaust smoke/vapour etc.
 
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