LiquidPiston: Efficient rotary engine • Hacker News Board

It even has disadvantages compared to the Wankel engine, in that the intake and exhaust airflows are through the sides of the engine, so you can't even stack them along the same crankshaft without seriously compromising the airflow and packaging. Also, while it doesn't have the Wankel rotor tip seals and their associated issues, they don't say much about sealing all their other surfaces.

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.

Re: LiquidPiston: Efficient rotary engine

#19

Post by deelowe » Wed, Jun 29, 2016, 5:11 PM UTC

dsfyu404ed wrote: post #7

The way the shape of the combustion area changes to include long thin areas as the rotor is moved looks like an emissions nightmare. Deep and/or wedge shaped combustion chambers went away in the 1960s because of that. 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 a…

They list the benefits here: http://liquidpiston.com/technology/engine-benefits/

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.

Re: LiquidPiston: Efficient rotary engine

#20

Post by en4bz » Wed, Jun 29, 2016, 5:12 PM UTC

dsfyu404ed wrote: post #7

The way the shape of the combustion area changes to include long thin areas as the rotor is moved looks like an emissions nightmare. Deep and/or wedge shaped combustion chambers went away in the 1960s because of that. 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 a…

Since combustion happens on the three corners of the engine the heat distribution will be much more even compared to a Wankel where there is a heat differential between the combustion and compression side of the engine. Since there is better heat distribution the tolerances may be able to be smaller reducing the sealing issues.