Centrifugal compressor with seal bearing

1. A centrifugal compressor adapted to be used in a chiller system, the centrifugal compressor comprising:

a casing having an inlet portion and an outlet portion;

an impeller attached to a shaft rotatable about a shaft rotation axis, the impeller having an impeller shroud which encloses the impeller;

a motor configured and arranged to rotate the shaft in order to rotate the impeller;

a diffuser disposed in the outlet portion downstream of the impeller;

a seal bearing attached to the inlet portion to seal the impeller shroud, and rotatably supporting the impeller and the shaft; and

an oil sump configured and arranged to receive oil,

the seal bearing including

an oil supply groove formed on a shroud facing surface of the seal bearing which faces the impeller shroud,

at least one oil return groove formed on the shroud facing surface of the seal bearing, and

at least one separation groove formed on the shroud facing surface of the seal bearing,

oil being supplied to the oil supply groove from the oil sump, and the oil being returned to the oil sump via the oil return groove.

2. The centrifugal compressor according to claim 1 , wherein

oil containing refrigerant in the separation groove is introduced into the oil sump in which oil containing refrigerant is separated into an oil portion and a refrigerant portion, and

the refrigerant portion is returned to a suction side of the centrifugal compressor.

3. The centrifugal compressor according to claim 1 , wherein

the seal bearing is a radial bearing.

4. A centrifugal compressor adapted to be used in a chiller system, the centrifugal compressor comprising:

a casing having an inlet portion and an outlet portion;

an impeller attached to a shaft rotatable about a shaft rotation axis, the impeller having an impeller shroud which encloses the impeller;

a motor configured and arranged to rotate the shaft in order to rotate the impeller;

a diffuser disposed in the outlet portion downstream of the impeller; and

a seal bearing attached to the inlet portion to seal the impeller shroud, and rotatably supporting the impeller and the shaft, the seal bearing including

an oil supply groove formed on a shroud facing surface of the seal bearing which faces the impeller shroud,

at least one oil return groove formed on the shroud facing surface of the seal bearing, the at least one oil return groove including a first oil return groove and a second oil return groove, and

a first separation groove and a second separation groove formed on the shroud facing surface of the seal bearing,

the oil supply groove being interposed between the first oil return groove and the second oil return groove,

the first oil return groove being interposed between the oil supply groove and the first separation groove,

the second oil return groove being interposed between the oil supply groove and the second separation groove,

the first oil return groove and the first separation groove being disposed upstream of a refrigerant flow relative to the oil supply groove, and

the second oil return groove and the second separation groove being disposed downstream of the refrigerant flow relative to the oil supply groove.

5. The centrifugal compressor according to claim 4 , wherein

the seal bearing is a radial bearing.

6. A centrifugal compressor adapted to be used in a chiller system, the centrifugal compressor comprising:

a casing having an inlet portion and an outlet portion;

an impeller attached to a shaft rotatable about a shaft rotation axis, the impeller having an impeller shroud which encloses the impeller;

a motor configured and arranged to rotate the shaft in order to rotate the impeller;

a diffuser disposed in the outlet portion downstream of the impeller; and

a seal bearing attached to the inlet portion to seal the impeller shroud, and rotatably supporting the impeller and the shaft, the seal bearing including

an oil supply groove formed on a shroud facing surface of the seal bearing which faces the impeller shroud,

at least one oil return groove formed on the shroud facing surface of the seal bearing, and

at least one separation groove formed on the shroud facing surface of the seal bearing,

a first set of teeth and a second set of teeth being formed on the shroud facing surface of the seal bearing, the first set of teeth being located between an end of the seal bearing and the separation groove, and the second set of teeth being located between the separation groove and the oil return groove, and

the at least one separation groove receiving oil and refrigerant which pass through the first set of teeth and the second set of teeth, respectively.

7. The centrifugal compressor according to claim 6 , wherein

the seal bearing is a radial bearing.

8. A centrifugal compressor adapted to be used in a chiller system, the centrifugal compressor comprising:

a casing having an inlet portion and an outlet portion;

an impeller attached to a shaft rotatable about a shaft rotation axis, the impeller having an impeller shroud which encloses the impeller;

a motor configured and arranged to rotate the shaft in order to rotate the impeller;

a diffuser disposed in the outlet portion downstream of the impeller; and

a seal bearing attached to the inlet portion to seal the impeller shroud, and rotatably supporting the impeller and the shaft, the seal bearing including an oil supply groove formed on a shroud facing surface of the seal bearing which faces the impeller shroud,

the impeller shroud having a stepped part which outwardly projects in a direction perpendicular to the shaft rotation axis,

the seal bearing having a recessed part which receives the stepped part, and

the oil supply groove being provided in the recessed part.

9. The centrifugal compressor according to claim 8 , wherein

the seal bearing further includes at least one oil return groove formed on the shroud facing surface of the seal bearing.

10. The centrifugal compressor according to claim 9 , wherein

the at least one oil return groove includes a first oil return groove and a second oil return groove, and

the oil supply groove is interposed between the first oil return groove and the second oil return groove.

11. The centrifugal compressor according to claim 10 , wherein

the seal bearing further includes a first separation groove and a second separation groove formed on the shroud facing surface of the seal bearing,

the first oil return groove is interposed between the oil supply groove and the first separation groove, and

the second oil return groove is interposed between the oil supply groove and the second separation groove.

12. The centrifugal compressor according to claim 9 , wherein

the seal bearing further includes at least one separation groove formed on the shroud facing surface of the seal bearing.

13. The centrifugal compressor according to claim 12 , wherein

a first set of teeth and a second set of teeth are formed on the shroud facing surface of the seal bearing, the first set of teeth being located between an end of the seal bearing and the separation groove, and the second set of teeth being located between the separation groove and the oil return groove.

14. The centrifugal compressor according to claim 12 , wherein

the separation groove has an annular shape extending circumferentially around the impeller shroud.

15. The centrifugal compressor according to claim 12 , further comprising

an oil sump configured and arranged to receive oil,

oil being supplied to the oil supply groove from the oil sump, and the oil being returned to the oil sump via the oil return groove.

16. The centrifugal compressor according to claim 8 , wherein

the seal bearing is a radial bearing.