A motor-jet is a intermediate form of jet propulsion developed during the interwar period. As its name implies, an external motor drives the compressor section of the jet engine. This is easier to build than a turbojet (no need for high-temperature alloys) but less efficient.

I think that the heat from the combustion chamber could be used to power a steam engine which would drive the compressor. I am using an axial engine design to keep the motor diameter low.