Rotary engines: I'm not dead yet!

[Just Jeepin']

LiquidPiston's "inside-out" rotary X-Engine wins Army research contract

https://newatlas.com/military/liquidpiston-rotary-x-engine-army-generator/

We've written a few times before about the fascinating LiquidPiston rotary engine. It's not a Wankel – indeed, it's closer to an inside-out Wankel – and with only two moving parts, it's able to deliver extraordinary power density at up to 1.5 horsepower per pound (0.45 kg).

According to co-founder and CEO Alec Schkolnik, the X Engine design combines the high compression ratio and direct injection of a diesel engine with the constant volume combustion process of an Otto cycle engine and the over-expansion abilities of an Atkinson cycle engine, while solving the lubrication and sealing issues of the Wankel rotary engine and delivering huge power and efficiency.

Some videos of their engines:

Description of working at LiquidPiston by a former employee (courtesy THE_PUN_STOPS on Hacker News) :

It was just like any startup really, a great team of really smart and dedicated folks trying to disrupt an entrenched industry using new ideas. Lots of simulation, lots of practical prototyping, lots of test rig time. We spent so, so many hours in test chambers observing how a particular engine type behaved with incremental changes to its design, changes which were backed up by simulation. The resulting data was used to strengthen the simulation and we repeated this loop many times. The challenge with this is that there are seemingly infinite different parameters to observe and control in each loop in both the physical and simulated engines, which must be done with high fidelity to learn things.

My understanding of thermodynamics was routinely humbled by my coworkers. I remember one time rolling into the office in the morning to find my coworker twirling with excitement and saying something like "I had a realization at 3AM and came to the office and figured out my enthalpy problem!"

Working with your buddies to create a working engine from scratch that is unlike any engine that has ever been created before it is a real rush. I recommend it for anyone.

[Manwich]

@just-jeepin

Sadly I predict they will be dead sooner or later. Batteries, electric motors, electronics and the software is where the money is going forward... unless this thing has efficiency better than a diesel with no emissions (including CO2)

[RacinBob]

I swear I saw the same release something like 7 years ago.

[WhoIsTheLeader]

All hail the rotaries! I wish they included a sound clip of it actually running instead of that terrible ear bleeding music. I'm happy to hear the rotary continues though it's not clear what application these would be used for.

[Just Jeepin']

@racinbob They’ve definitely been around for a while. The prototype video was published 5 years ago.

[CobraJoe]

@manwich There still is room in the market for a "Range extended EV".

Keep the electric range low, but add an efficient small gas generator to recharge it. The result is a car that will never use gas on the average commute, but has all the advantages of a gas powered car for quick refuelling on long drives.

Plus, it would require less batteries than a normal EV, and could potentially be lighter too.

I'm still betting that we'll see a lot of range extended EVs to fill the gap between primarily gas powered cars and 100% electric cars.

[HammerheadFistpunch]

@cobrajoe I'm hopeful for a replacement for petroleum as a fuel, but I honestly don't think it's batteries. The resources aren't there to support an EV expansion without a big change in battery technology. I think gas and diesel will be around for a long while still, though I do think a strong push away from carbon is necessary and important.

[CobraJoe]

@hammerheadfistpunch It won't be the current design of batteries at least. If ultracapacitors or fuel cells or some other new tech can't meet the demands of a EV, there are still several new battery technologies that look promising.

Until one of these new technologies (and the infrastructure) is developed enough to provide viable energy storage for every current vehicle on the road, we'll either need to just accept the current state of petroleum powered cars for longer, or have a "bridge" type vehicle that is partially EV and partially gasoline.

Personally, I don't think the transition to full EV will happen in a timely manner unless there is a solid push away from oil, so the "bridge vehicle" seems like the most likely outcome for the immediate future.

[MybirdIStheword]

@just-jeepin so basically a wankel but a pringle instead of a dorito. Nice.