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

Mauller

Mauller

Mauller

Soldato
Joined
7 Feb 2015
Posts
2,864
Location
South West
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.
Click to expand...

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.
Click to expand...

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
 
Last edited:
I thought Wankel was 2x equivalent because it effectively does parts of the "4-stroke" process at the same time. The eccentric shaft rotates 3x for every rotor rotation. Each rotor is 0.65l and gives 3 power pulses per rotor rotation. That is equivalent to 1 pulse per rotation of eccentric shaft. With two rotors working together this gives 1.3l. You get 2.6l as an equivalent when compared to a piston engine because the piston engine has one stroke where it does not combust fuel. This means the crank shaft rotates 2x for every pulse. To compare the two engines as an equivalent the rotary capacity is then multiplied by 2.
 
Last edited:
acemastr said:
Sounds cool, 3hp from '70cc' isn't wonderful though
Click to expand...

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.
Click to expand...

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
 
Last edited:
Mauller said:
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.



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
Click to expand...

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.
 
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.
Click to expand...

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.
 
Last edited:
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.
 
Having an applied thermodynamics module at uni, I found this very interesting. Cheers for posting.

Will be interesting to see how far this goes and where it could end up.
 
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.
 
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.
Click to expand...

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.
 
Last edited:
Mauller said:
No seal issues or incomplete combustion as with the wankel, the seals are on the body rather than the rotor.
Click to expand...

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.

Mauller said:
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.
Click to expand...

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?
 
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?
Click to expand...

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.
 
Last edited:
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.
 
Last edited:
You must log in or register to reply here.
Back
Top Bottom