Abstract: A fluid energy conversion apparatus including a fluid path assembly having an outside guide assembly, a cylindrical wall inside surface and at least one inside guide assembly is provided. There is also a cylindrical partition wall which extends between the outside guide assembly and the inside guide assembly with its central axis set on the central axis of the cylindrical wall inside surface, the cylindrical wall inside surface of the outside guide assembly and the cylindrical partition wall defining an annular outside path therebetween and the outside peripheral surface of the inside guide assembly and the cylindrical partition wall defining an annular inside path therebetween. There is a plurality of support struts connecting the outside guide assembly, the inside guide assembly and the cylindrical partition wall.