Centrifugal compressor with diffuser

1. A centrifugal compressor comprising:

a rotation shaft provided inside a housing having a rotation axis;

a compressor impeller accommodated inside the housing and attached to one end of the rotation shaft;

a first wall surface and a second wall surface formed inside the housing, the first wall surface and the second wall surface facing each other in an axial direction of the rotation axis;

a diffuser formed between the first wall surface and the second wall surface in the axial direction; and

a wall portion including the second wall surface and separating the diffuser from an axial space inside the housing in which the rotation shaft extends,

wherein the wall portion includes at least one extraction hole that fluidly couples the diffuser to the axial space and that is configured to extract a gas from the diffuser.

2. The centrifugal compressor according to claim 1 , further comprising:

a gas bearing structure supporting the rotation shaft;

a bearing cooling line formed inside the housing as a part of the axial space, the bearing cooling line fluidly coupling the extraction hole to the gas bearing structure; and

a cooler that is fluidly coupled to the bearing cooling line and that is configured to cool the gas extracted through the extraction hole.

3. The centrifugal compressor according to claim 1 ,

wherein a plurality of vanes are fixed to the wall portion, the plurality of vanes protruding toward the first wall surface and being arranged in the diffuser at spaced apart intervals in a circumferential direction of the rotation axis, and

wherein the extraction hole is formed between two adjacent vanes.

4. The centrifugal compressor according to claim 3 ,

wherein each of the plurality of vanes includes a trailing edge, and

wherein the at least one extraction hole is provided at a position overlapping a pitch circle diameter (PCD) of the trailing edge.

5. The centrifugal compressor according to claim 3 ,

wherein the at least one extraction hole comprises an elongated hole that is elongated in a flow direction between the two adjacent vanes.

6. The centrifugal compressor according to claim 1 ,

wherein the wall portion only has a single through-hole, the single through-hole consisting of the at least one extraction hole.

7. The centrifugal compressor according to claim 1 ,

wherein the housing includes a bearing housing and a compressor housing fixed to the bearing housing, and

wherein the wall portion comprises a diffuser plate that at least partially forms the diffuser, the diffuser plate being disposed between the bearing housing and the compressor hosing.

8. The centrifugal compressor according to claim 7 ,

wherein the at least one extraction hole comprises a through-hole penetrating the diffuser plate.

9. The centrifugal compressor according to claim 1 ,

wherein the at least one extraction hole comprises an elongated hole that is elongated in a direction inclined with respect to a radial direction of the rotation axis.

10. The centrifugal compressor according to claim 1 ,

wherein the wall portion does not include a through-hole configured to return the extracted gas to the diffuser.

11. A centrifugal compressor comprising:

a rotation shaft having a rotation axis;

a compressor impeller attached to the rotation shaft, the compressor impeller including a front surface and a back surface;

a compressor housing accommodating the compressor, the compressor housing including an opening which exposes the back surface of the compressor impeller; and

a diffuser plate that at least partially covers the opening of the compressor housing and faces the back surface of the compressor impeller in an axial direction of the rotation axis, the diffuser plate at least partially forming a diffuser that extends in both a radial direction and a circumferential direction of the rotation axis, the diffuser being disposed radially outward from the compressor impeller,

wherein the diffuser plate includes at least one extraction hole configured to extract a gas from the diffuser.

12. The centrifugal compressor according to claim 11 ,

wherein a plurality of vanes are attached to the diffuser plate, the plurality of vanes being arranged in the diffuser at spaced apart intervals in the circumferential direction, and

wherein the extraction hole is formed between two adjacent vanes.

13. The centrifugal compressor according to claim 12 ,

wherein each of the plurality of vanes includes a trailing edge, and

wherein the at least one extraction hole is provided at a position overlapping a pitch circle diameter (PCD) of the trailing edge, the PCD taken with respect to a radial distance of the trailing edge from a center of the diffuser plate, the PCD equal to twice the radial distance.

14. The centrifugal compressor according to claim 11 ,

wherein the at least one extraction hole comprises an elongated hole that is elongated in a direction inclined with respect to the radial direction of the rotation axis.

15. The centrifugal compressor according to claim 14 ,

wherein the elongated hole is additionally elongated in a direction that is inclined with respect to the circumferential direction of the rotation axis.

16. The centrifugal compressor according to claim 11 ,

wherein the diffuser plate has only a single through-hole, the single through-hole consisting of the at least one extraction hole.

17. The centrifugal compressor according to claim 11 ,

wherein the at least one extraction hole comprises a pillar-shaped through-hole formed in the diffuser plate.

18. The centrifugal compressor according to claim 11 , further comprising:

an impeller chamber, the impeller chamber at least partially forming a compressor scroll that is fluidly coupled to the diffuser.

19. The centrifugal compressor according to claim 18 ,

wherein the impeller chamber includes a first wall surface that is located between the diffuser and the compressor scroll.

20. The centrifugal compressor according to claim 19 ,

wherein the diffuser plate includes a second wall surface that faces the first wall surface, and

wherein the diffuser is located between the first wall surface and the second wall surface in the axial direction of the rotation axis.