You are describing a Wankel type engine, which is not a piston engine, but is a type of 4 stroke "otto cycle" engine.
They have been around since forever (the 60s), and would seem to be ideal replacement for aircraft piston engines, having the simplicity and power to weight approaching that of a turbine. You would think.
But if you read up on the Wankel's history with Mazda, and the numerous attempts to stick them in airplanes, you find they are just riddled with frustrating limitations:
- High fuel consumption, like 2 strokes or worse (Mazda RX7s and 8s were notorious for lousy fuel economy).
- Low torque production due to the very low "leverage" the combustion chamber is able to apply to the eccentric cam of the crankshaft. They are equivalent to an extremely short stroke piston engine.
- Because of the low torque, they have to spin very fast to make any power, requiring very large gear reductions, although they don't suffer from the torsional resonance problems of gear reduced piston engines, because of the way the power strokes of multi-rotor Wankels overlap.
- Apex seal wear, which Mazda finally dealt with by feeding oil directly to the Apex seals (equivalent to piston rings in a piston engine), which means they consume oil like 2 strokes.
There have been many attempts to make aircraft engines out of multi-rotor Mazdas, and they have flown, but eventually were abandoned due to technical problems (not to mention ear splitting noise levels - I saw an RX7 powered Van's RV-4 at Oshkosh in the 90s - wow what a racket it made, even with a muffler).
Roton is just another case of someone stumbling onto the configuration and making a go at getting around the engine's limitations. The configuration's simplicity and potential reliability is just so enticing.
However, there IS something new under the sun, with a new rotary design that just may be the answer.
As for propellers, oodles of propellers here.