It's effectively an inside-out wankel, so the seals are stationary. This is a much easier problem to solve, and now you don't need to throw oil in the combustion chamber to lubricate the moving seals.
problem one will be balancing forces if combustion is taking place on one side. also i don't see why this should be burning less oil. you are smearing the oil constantly around.
This isn't all that different from a four stroke, at some level. With a piston engine you lubricate from below, the oil never getting above the rings. Practically some does and gets burned away, but that's negligible usually. Anyway, the seals on the liquidpiston engine supposedly do the same, keeping the oil from leaking around the seals (in a significant quantity anyway; I'm sure it's higher than a four stroke though).
Here's what their webpage says:
> The seals do not experience centrifugal forces, and can be lubricated directly by metering small amounts of oil directly to the sealing surface through the housings, which means that oil consumption can be reduced to levels potentially comparable to that of a 4-stroke piston engine (essentially negligible).
Obviously take all this with a grain of salt. I haven't read any practical studies on this.
Yeah but "just replacing $50 seal every few years" is smaller problem than "taking apart whole engine to replace the $50 seal". And now they can technically be directly oiled instead of whole oil in petrol thing.
If you look at an image, you can see the three apex seals on the stator, which is shaped the same way as a wankel rotor. The rotor of the liquidpiston engine is shaped similarly to the wankel stator and has no seals. It's almost the same just turned inside-out.