Ludwig Wittgenstein designed (and received a patent for, at the remarkable age of 22) an aeronautical propeller.
Wittgenstein’s design required air and gas to be forced along the propeller arms to combustion chambers on the end of each blade, where it was then compressed by the centrifugal force exerted by the revolving arms and ignited.
Propellers of the time were typically wood, whereas modern blades are made from pressed steel laminates as separate halves, which are then welded together. This gives the blade a hollow interior, and therefore creates an ideal pathway for the air and gas.
I've found some plans for this design, and some discussion of it, but it's not clear to me whether a working model was ever built, or attempted. I'd love to know whether it actually offered any advantage, or even whether it could be made to work with a reasonable degree of success.