Advanced super-critical CO2 expander-generator

A method for operating a rotating machine, comprising:

• expanding a working fluid in an expansion device disposed within a hermetically-sealed housing, the expansion device being configured to rotate an expander rotor having a hollow shaft defining a chamber therein;
• driving a generator rotor with the expander rotor, the generator rotor being supported by one or more radial bearings and at least partially supporting a generator disposed within the housing and axially-spaced from the expansion device;
• extracting working fluid from an intermediate expansion stage arranged within the expansion;
• introducing a first portion of extracted working fluid into the housing to cool the generator and the radial bearings;
• and
• introducing a second portion of extracted working fluid into the chamber to minimize unequal axial thrust loads.

A rotating machine, comprising:

• an expander casing coupled to a generator casing to form a hermetically-sealed housing, the expander casing having an expansion device disposed therein and the generator casing having a generator disposed therein;
• a hollow expander rotor arranged for rotation within the expander casing and defining a chamber within the expander rotor;
• a generator rotor arranged for rotation within the generator casing and being supported by one or more radial bearings, the generator rotor being coupled to the expander rotor with a coupling disposed at least partially within the chamber such that the expander rotor drives the generator rotor;
• an extraction line fluidly coupled to an intermediate expansion stage of the expansion device and configured to extract working fluid therefrom;
• a first fluid line fluidly coupled to the extraction line and configured to introduce a first portion of extracted working fluid into the generator casing to regulate a temperature of the generator and the radial bearings;
• and
• a second fluid line fluidly coupled to the extraction line and configured to introduce a second portion of extracted working fluid into the chamber.