Electric centrifugal compressor

An electric centrifugal compressor, comprising:

• an electric motor including a rotational shaft;
• a first impeller disposed on one end side of the rotational shaft;
• a first bearing rotatably supporting the rotational shaft at a position between the first impeller and the electric motor and including a lubricant;
• and
• a first bearing housing accommodating the first bearing, and
• a biasing spring configured to bias the first bearing to a side opposite to the first impeller;
• wherein the first bearing housing includes a compressed gas supply hole for supplying a compressed gas from outside of the first bearing housing to a gap between a rotating body including the rotational shaft and the first bearing housing, and
• wherein an outlet of the compressed gas supply hole is disposed on an inner surface of the first bearing housing and is located between the first impeller and the first bearing in an axial direction of the rotational shaft,
• wherein the electric centrifugal compressor further comprises:
• a first seal element disposed so as to seal the gap at a position between the first impeller and the outlet of the compressed gas supply hole in the axial direction;
• a second seal element disposed so as to seal the gap at a position between the outlet of the compressed gas supply hole and the first bearing in the axial direction;
• a compressed gas introduction line configured to introduce compressed gas to an inlet of the compressed gas supply hole so that a pressure in a space of the gap between the first seal element and the second seal element is larger than a pressure in a space of the gap adjacent to a back surface of the first impeller;
• and
• a cooler provided in the compressed gas introduction line for cooling the compressed gas, and
• a lip seal provided at a position between the second seal element and the first bearing in the axial direction so as to seal the gap, the lip seal being configured to separate from an outer peripheral surface of the rotating body by a pressure of the compressed gas supplied from the compressed gas supply hole to the gap when a rotational speed of the rotational shaft exceeds a reference value;
• wherein the first bearing housing includes an annular space configured to accommodate the biasing spring, the annular space communicating with a region between the second seal element and the first bearing,
• wherein the first bearing housing includes a purge hole for discharging the compressed gas supplied from the compressed gas supply hole to the gap to outside of the first bearing housing, and
• wherein an inlet of the purge hole is disposed on the inner surface of the first bearing housing and is located between the second seal element and the first bearing in the axial direction and communicates with the annular space.