I was looking at unconventional IC engines when I came across
Otto Lutz's swing piston engine.
Contemporary German turbines were having trouble coping with high temperature produced by the combustion chamber. To solve this problem Lutz's engine was supposed to be put in as a gas generator. It would extract some work and cool the heated mixture so that the turbine could handle the heat.
Does anyone know how it actually worked? I have looked at Lutz's patent but couldn't tell how it would operate.
Here is a drawing
If the German designers had dropped the turbine instead using only Lutz's engine to do work, could the resultant machine have functioned like a turboprop?