LiquidPiston: Efficient rotary engine
liquidpiston.com
liquidpiston.com
Emissions speculation aside, what part of this is superior to a Wankel?
I can see the three chamber design having merit for compression ignition apps because you can better spread the combustion force around the block and reduce the amount of material needed for a particular power level or part life. With some creativity off-highway diesel could probably be used a the lubricant(highway diesel is ultra low sulfer and doesn't lubricate well at all) in low power (portable equipment) applications. All the simplicity and light weight of a two stroke gas engine but with far less idle fuel consumption, no worrying about forgetting to premix or forgetting that you already premixed and doubling the oil and you can refill it by siphoning off your tractor (and don't have to worry about fuel going stale over the winter). This is just wishful thinking though.
With a little reworking the three small chambers per rotor would probably be pretty nice for an air compressor application. More of a smooth hum and less of a drone.
The only possible thing I can think of is
Last time this was discussed, the power density was listed at the most interesting feature. Also that apex seals are in the casing instead of the rotor, which I think some speculated could help with wear/maintenance.
It has almost all the problems of Wankel. Low torque, difficult sealing, weirdly shaped expansion chamber (where part of the burn happens at high RPM, this might get you impurities in the burn). This seems to be kinda "sleeve valve" type valves. Poppets dominate for couple of reasons: A quick open and close and B self sealing. Both features that these things necessarily lack. The balance of the thing seems horrible. You could get good balance if you put four of these on single crankshaft. But then you have 12 incredibly small burn volumes for given size of engine -> even less torque.
"A dwell near top-dead-center forces combustion to occur at nearly constant-volume conditions." If you increase chamber pressure in regular engine during top dead center, you risk breaking the crankshaft. It's likely this thing can only do it because of low HP and no crankshaft. Which in turn fucks the balance.
I'd pick rotary Atkinson over this. https://en.wikipedia.org/wiki/Atkinson_cycle
I can't quite figure out how they can manage to seal this contraption - plenty of rotating and sliding gaps in there.
Manufacturing of some of the shown parts look tricky as well.
It looks more like some cool gadget that you design for a movie than a practical machine.
It doesn't look like it would be efficient at a car-sized scale.
But even a comparison to typical lawnmower-sized engines would be helpful.
This is likely why they replaced the 6.5Hp motor in their demo go-kart with a 3Hp version of their own motor (if it was a real Wankel, they would have used a two- or three-rotor stack and gotten almost the same or more power for ~1/4 the weight, which would have been a good demo. Instead, they look like they're driving a go-kart at about 1/4 throttle.
Although they tout weight advantages, their power-weight ratio is actually pretty bad compared to a variety of other engines, including Wankels and two-strokes of similar sizes, e.g., for model airplane power plants.
For examples of actual liquid piston engines, see:
https://en.wikipedia.org/wiki/Fluidyne_engine
https://en.wikipedia.org/wiki/Humphrey_pump