As automakers, the military, and industry take steps away from petroleum by experimenting in technologies including electrified and fuel cells, the internal combustion engine is still very much alive, and work is underway to maximize efficiency, while reducing pollution, complexity and cost.

One such endeavor claiming all these benefits in spades is the product of LiquidPiston, a 12-person company in Connecticut that’s had some success gaining money and attention for its unique, light, high-power-to-weight engines.

X1 engine running on the test bench. The company says one early on application could be as a range extender.
 

The company's engine design(s) may burn diesel or other fuels, and borrow from a number of architectures, but mainly utilize principles of the Wankel rotary. The company says its unique innovation is “versatile and capable of outperforming conventional engines on all parameters.”

LiquidPiston is fine-tuning different variations of its new architecture that it has dubbed "High-Efficiency Hybrid Cycle" (HEHC), and says it can deliver 50-percent efficiency compared to perhaps 30-percent peak efficiency of traditional engines.

 

The High Efficiency Hybrid Cycle' (HEHC) attempts to combine the best features of numerous thermodynamic cycles including Otto, Diesel, Rankine, and Atkinson to create a highly efficient engine.
The design – notably a more recent “X1” variant – is said to provide an improved thermodynamic cycle that optimizes each process (stroke) of the engine operation, with the aim of maximizing fuel efficiency.

In a recent interview with the company’s CEO and President Alexander Shkolnik, GigaOm was told various versions of the for-now small diesel burning powerplant promise 10-times fewer parts than current diesel engines and are thus smaller and lighter.

The engine actually borrows elements not just from Felix Wankel, but also from Otto, Diesel, Atkinson, and Rankine cycles, but resembles a Wankel the most, albeit in reverse.

 

X2 version.
Instead of the rotor doing the sealing, the X1 lets this task go to the housing which utilize its "apex" seals, with the claim being oil sealing is improved over a traditional rotary.

It utilizes an 18:1 compression ratio, direct injection, maintains constant volume during ignition and burns fuel much longer than traditional engines essentially getting more buck out of the bang.

The design also does away with liquid cooling, as it uses the fuel so much more efficiently, and produces less heat as a byproduct of combustion. Alternately, if cooling is needed, the engine can be made to suck in and exhaust cooling air, or have water injected in to the combustion chamber.

Popular Mechanics notes these neat tricks provides a triple payback: the engine is cooled, NOx emissions are reduced, some of the water is converted to steam, so power is increased.

 

Here is an earlier generation of a 20-horsepower prototype engine able to use diesel and gasoline fuel.
Various experiments are ongoing to increase efficiency even as the company seeks investors, and potential contracts for commercial applications.

Alexander Shkolnik told GigaOm the engine would likely see service in military vehicle applications, plug-in range-extended vehicles, long-haul trucks, and other niche markets at first, and the startup has raised $12.3 million to date, and is aiming for another $20 million later this year.

The company’s Web site says the original idea was the product of Alexander’s father, Dr. Nikolay Shkolnik, during PhD studies in theoretical physics at the University of Connecticut. A couple decades later in the early 2000s he was working as program manager for a consulting firm, at which he had developed fuel cells, super-capacitors, batteries, and other energy technologies.

But, says his brief history, "he understood that a more efficient engine could compete with fuel cells and other technologies on well-to-wheel efficiency, while being cheaper to make and more compact."

The actual first "Liquid Piston" engine was patented in 2003 by Nikolay, and in 2004 it won a $50,000 business plan competition at MIT, and today, having crossed other hurdles, the company led by his son has a 6,000-square-foot facility in Bloomfield, Conn., and says it sees light at the end of the tunnel.

But, you may ask, why call it "Liquid Piston?" This we asked for you, and were told by Alexander – who also goes by Alec – the "Liquid" name has stuck around from earlier designs that actually did use liquid instead of metal in the combustion chamber.

"LiquidPiston has been exploring the scientific principles of the High Efficiency Hybrid Cycle for several years. There are many potential ways of embodying this new thermodynamic cycle," said Alec. "Our first concept involved liquid in place of a metal piston, and gas would act on the liquid. It was a nice idea, but required a very large pump, so we moved towards a more 'conventional' (e.g. metal) solution. Over time, the design has continued to get more and more simple, while maintaining the cycle at the heart of the technology. The new X engine is the culmination of this effort. The new engine is incredibly simple, and still executes the original LiquidPiston' HEHC cycle."

 

 
LPI’s engine is architected to have the following unique properties:

• High fuel efficiency of 57-percent at peak, and 50 percent at part-load

• High power density of 1 hp / lb

• Simple design with low part count

• Multi-fuel capable: diesel, JP8, gasoline, natural gas, bio-fuels

• Low noise: the engine has low pressure exhaust and no poppet valves

LPI says its design outdoes traditional designs in applications where work loads can vary – such as during idling. Here. It says, traditional engines can drop as low as 1 percent efficient, and auto engines are typically only 15-percent efficient based on extensive bench testing and research.

 

Bigger is not always better.

In a best case scenario, it says, the “30-percent” efficiency of converting chemical energy to useful work also sees 40-percent of the fuel turned to heat, and 30-percent lost with exhaust gases.

Perhaps this is why 90-percent-efficient electric motors are gaining so much favor, but rather than digress, we’ll repeat the fact that the industry and society are still wedded to fuel burners, and there is a genuine need for them as other technologies are also being developed in the meantime.

The motor design and LiquidPiston were also briefly written about in June by the Society of Automotive Engineers , and for more info, you can visit the company’s Web site , or review a LiquidPiston SAE technical paper and another SAE technical paper as well.

 

Specs are very encouraging. I've been saying for years that the ultimate range extender will likely look different and likely be a rotary of some sort. Compact weight, size, and cost are enough on their own but even if they can get real world volume production efficiencies above 35% this would have the properties of a fantastic range extender. Apex seals with 18:1 compression ratios seem like a tall engineering hurdle to climb, however.

 

Being that I bought gas on Saturday for the first time since owning my Volt, and I only use about 1.5 gallons/month avg., ICE efficiency improvements do not mean much for the EREV. However weight reduction and space saving do. So, keep up the good work.

 

Yes, this is a very interesting design, and I believe an improvement on the Wankel. However it still has the Wankel's major nemesis of difficult sealing.

I still think that the best design for the Volt is the wave-disk engine. http://www.thetruthaboutcars.com/2011/03/ask-the-best-and-brightest-wave-disc-engines/

GM helped pay for the initial research on this engine and I hope that they have an improved version running in their engine lab. The wave-disk engine runs at a single rpm, and is therefore only suitable to run a generator, but is very simple, compact and efficient.

 

Good one Jeff.
You made me get out my Thermo book.

There's something confusing about the PV diagram. Why does it show a lower pressure ratio for the Diesel cycle than the Otto cycle. Diesels normally run at HIGHER pressure ratios than gas (Otto) cycle engines.

 

Seen a lot of these "next big thing" engines come and go. We can talk all we want about how embedded the industry is with current design but if an engine offered a 60% improvement (50% vs 30% is a bit over 60% improvement) the auto industry would be tripping over each other trying to get a hold of it. There usually is an Achilles heal somewhere in the design.

But all that said I still find these things really, really interesting and like rooting for the underdog and hope that this really is the "next big thing".

 

Looking at the SAE paper this engine has an "isolated combustion chamber". so now we may be talking materials that must be able to withstand being run at a constant temperature unlike a conventional otto cycle engine where the high temperature of combustion is transient allowing the use of cheaper materials. I believe the Scuderri engine operates with an isolated combustion chambrer also (as does a gas turbine).

Anyway... just thinking out loud (not that what I am thinking is correct

 

ronr64 :
.There usually is an Achilles heal somewhere in the design.
I'm not sure Ron but I think "isolated combustion chamber" might be the key (but I could be wrong)

 

Eliminating vibration of an E-Rev engine will make a difference in the feel of the car when the engine turns on. Having a 100% electric experience is so luxurious that car companies must do what they can to provide that feeling when the generator is running.

 

I don't understand something, If it is constant volume, where is the compression coming from unless it's from burning the fuel?

 

That bulbous thing on the end of the engine looks like a combustion chamber. Hmmmm

 

The aspects of necessary heat dissipation in potentially severely hostile geographical locations/conditions for these higher power to weight ratios ought not be understated. Longevity, after all, is what is in play for the long term reputation of any OEM. But it does, from an effort viewpoint, show that electric efficiencies are forcing the "raising of the bar" for combustion efficiencies.
The last few sentences of the SAE link reflect the overall measure of the balanced engineering viewpoint of SAE. The effort is interesting and has merit.

 

Good to hear alternate engine configurations are kicking in. I too do think a rotary will be good for Volt kind of application as the load is defined or its mostly constant load, constant speed operation.

But do they make to production is still a big question. I wonder what happened to http://www.libralato.co.uk . similarly was another piston engine (opec engine )

Same way the wave disk engine was supposed to have a model by last year end. but i never herd anything on it. The last news was something like wave disk engine achieved somewhere 30% efficiency and new news after this.

Lets wait for 2014 volt and what it comes. Till that time these engines hold only academic interests.

 

I always dreamed about such type solution for Volt. In case this engine will be real world bird it should start from being Voltec range extender - low weight and limited operating hours would be benefit for such application. In case it is not reliable enough the electric motor redundancy would help this feature not to be so critical as in pure ICE car application. I always been pusher for pure serial hybrid design which would be even more suitable for Wankel type engines. But may be current architecture could adapt to this engine as well.

Lutz and SUV developed by his company shell consider this peace of art and ordering limited series of such engines and testing in real world situation. May be it will pay back by being lowest MPG SUV in CS mode.
Would be worth to consider Voltec with such engine for military vehicles as well.

 

I need to read more about this engine.

I am an EE but I love mechanical engines, too, and as a hobby, I build scale models of such engines (my first was the Renwal Visible V8 in 1966). In that same year I knew and learned how the Wankel Rotary engine worked. My mother's cousin married an Argentine fellow who grew up in Germany (I have some German blood) and he taught me more about the Wankel and Diesel engines, which he worked on and ran races as a youth. He worked with the NSU car and had fun, so he was elated to teach me about it. But I never saw a Wankel until I bought my Renwal Visible Wankel model and several parts of a used Mazda Wankel engine later. I did enjoy a ride in the Mazda RX3 in 1970, and it wowed me.

When I started my first engineering classes I wasn't sure which branch to enter, but I liked mechanical engineering so my first written report in 1969 was a comparison of the different gas engines, including the Otto and Diesel cycles, and the piston, Wankel and turbine engines. My conclusion was the combination of the gas turbine and the piston engine, which is the present turbocharged engine in common use.

But as I enter electrical engineering classes, I discovered how efficient the electrical motor is and changed my view on gas engines. Now that I also understand how the fuel cell works, I support the research on a room-temperature fuel cell system that can convert many or most of the common gas and liquid fuels directly into electrical energy with little heat loss and emissions. The high heat of burning fuel is the main source of the nitrous oxides that does more damage than carbon monoxide and dioxide.

So if this new rotary can run cooler and thus produce much less emissions, then I agree that it may be a new range extender for the Voltec system, but I hope GM will use its fuel cell experience (with the 2008 Equinox) and build a new fuel cell range extender, until motor and battery technology can give us over 100 miles in range and eliminate completely the gas engine for transportation. Then these gas engines will become museum curiosities.

Raymond

 

Ultimately the issue is that worldwide demand for oil requires oil which is more difficult to recover and thus more expensive. Innovations in ICE technologies can decrease fuel consumption per vehicle, but if the number of vehicles rises faster than the efficiency increases, you end up with more demand and more expensive gasoline. As Mitt Romney pointed out in last night's debate, in just one country (China), every year there are 20M more Chinese moving from the country to the cities. Those folks are going to need transportation.

It's like bailing out a boat filling with water where the water is coming in at a rate of 2X and you can bail it out at a rate of 1.5X. Basically you need to find a different boat.

 

I will believe it when I see it working and all the numbers and costs are verified by third party sources.

They claim it is better in every way but the devil is always in the details. What are the maintenance costs and timetables. If you have to rebuild it every 1000 miles, it will be of little use. If the tolerances are so tight that it only works in the lab under perfect conditions then that is also of little use. What happens when a little dirt gets into the system? So many real-world conditions to be tested. I am also not convinced that so much efficiency can be squeezed from that thermal cycle, especially in any practical way.

If this does work as advertised (not likely and they are shooting for a lot of funding right now), then there are two versions that would be great to have:

1) Hydraulic - for robotic systems
2) Gen-set - for range extender

A specifically designed turbine would also be good for such applications because a turbine can burn just about anything, has an excellent power to weight ratio and doesn't have to respond quickly to changes in power demand (will have accumulators or batteries in the system design).

The main thing holding back great robotic systems and EVs are high energy density power systems. Batteries and engines are just too heavy for the required power output and fuel burning is just so loud.

Thus, we humans are very limited to what we can do, even if that is quite amazing - to be very impressed, just check out an Abrams tank moving all that mass with it's turbine.

 

Koz : Apex seals with 18:1 compression ratios seem like a tall engineering hurdle to climb, however.
#1

Yeah, right. I'm from Missouri.

 

Raymondjram : I did enjoy a ride in the Mazda RX3 in 1970, and it wowed me.
#14

Yeah, me too. It was great while it lasted, LOL. My neighbor had one and he loved it, but he gave up and dumped it after the 3rd engine.

I really got excited about the Wankel in those days but its performance in the real world so disappointed me that I'm totally cynical about this stuff. I give a lot of credit to Mazda for its dogged determination to make the damned thing work, but even they failed in the end.

I wish that someone would give me $20 million to pursued my pet project too. I noted with interest that the guy's father had worked on "super capacitors". Somehow the name EeStor is echoing in my poor brain.

 

Texas : to be very impressed, just check out an Abrams tank moving all that mass with it’s turbine.
#16

Yeah, until some mujahedin blows it up with an ANFO bomb. I saw a video from Iraq if an M1 being blown into the air by an "IED" and landing on its back. They may have been great for stopping the Russkies from coming through the Fulda Gap, but they're not much use in these troubled days of "asymmetric warfare".

 

Seems like a good idea if it saved space .. weight and burned regular gas.

But I wonder about how long they last with a high compression ratio and turning off and on many times...

Always good to see the effort to improve... I wish them luck and hope these people are allowed to reap the benefits (profits) of their design ...

 

DonC ,

Well at the rate the Chinese increase the demand and the result for their own costs, those 20 million will be taking the train.

Plus, Mitt has been excessively pushing for coal energy so consistently, it is apparent that coal interests run his show.

Also, it takes as much energy to get crude out of tar sands as is in those tar sands, which in itself, is a boondoggle. Why don't those foreign energy interests keep their energy for local use, and not use even more energy to pump it clear across America with even more wasteful pumping costs which include heating that sludgy stuff all the way to the Texas coast? Coal and Tar...... not exactly twenty first century thinking. Completely absurd obviously.

 

Dan Petit : Coal and Tar…… not exactly twenty first century thinking. Completely absurd obviously.

#21

Amen brother. Preach on! +1

 

Noel Park : Somehow the name EeStor is echoing in my poor brain.

Looks like they gave an update about a month ago. Still no working prototype that I see.

http://finance.yahoo.com/news/zenn-motor-company-provides-eestor-223448203.html

 

kdawg : Looks like they gave an update about a month ago. Still no working prototype that I see.
#23

Damn, what a confusing world. Now I can't decide whether to buy stock in LiquidPiston or EeStor! Or is it Zenn? I just dunno.