FIELD: machine building.SUBSTANCE: invention relates to the fluid radial turbo-power machine return stage (RS), in particular, of the radial turbo compressor (TCO), with rotational axis (X) including the annular flow channel (CH) for the current process fluid (PF) supply from the first impeller (IMP1) flow hole to the downstream second impeller (IMP2) flow hole. To increase efficiency it has been proposed that the flow channel (CH) is formed by the limiting surface areas (SFA), of which at least one is determined, passing in the circumferential direction rough surface has increased roughness (RZ) as compared to the remaining areas.EFFECT: higher efficiency.15 cl, 1 dwg
