Centrifugal compressor for use with low global warming potential (GWP) refrigerant

1. A centrifugal compressor for use with a low global warming potential (GWP) refrigerant, the centrifugal compressor comprising:

a casing having a first inlet portion and a first outlet portion;

a first impeller disposed between the first inlet portion and the first outlet portion, the first impeller being attached to a first end of a shaft that is rotatable about a rotation axis, the first impeller being equipped with first blades, each of the first blades having a fully nonlinear shape in a quasi-orthogonal cross-sectional view, each of the first blades having a hub-side blade angle delta from a hub portion of the first impeller to a mid-span position of the first blade, the hub-side blade angle delta of each of the first blades varying along a streamwise direction such that the hub-side blade angle delta is largest at a first position closer to a leading edge of the first blade than to a trailing edge of the first blade;

a motor arranged inside the casing to rotate the shaft in order to rotate the first impeller,

the casing being configured such that the low global warming potential (GWP) refrigerant enters the first impeller from the first inlet portion along an axial direction of the first impeller and exits the first impeller to the first outlet portion in a radial direction of the first impeller.

2. The centrifugal compressor according to claim 1 , wherein

the first position is located between 10% and 40% of a blade length of the first blade in the streamwise direction, where 0% corresponds to the leading edge and 100% corresponds to the trailing edge.

3. The centrifugal compressor according to claim 1 , wherein

the hub-side blade angle delta is in a range of 10 to 30 degrees at the first position.

4. The centrifugal compressor according to claim 1 , wherein

a hub-side wrap angle delta of each of the first blades from the hub portion to the mid-span position varies along the streamwise direction such that the hub-side wrap angle delta is largest at a second position closer to the leading edge than to the trailing edge.

5. The centrifugal compressor according to claim 4 , wherein

the leading edge of each of the first blades has a nonlinear shape when an inlet side of the first impeller is viewed along a direction parallel to the rotation axis.

6. The centrifugal compressor according to claim 1 , wherein

the first impeller is a closed type impeller including the hub portion and a shroud portion, the first blades being disposed between the hub portion and the shroud portion, and

each of the first blades has a shroud-side blade angle delta from the mid-span position to the shroud portion, the shroud-side blade angle delta varying along the streamwise direction such that the shroud-side blade angle delta is largest at a third position closer to the leading edge of the first blade than to the trailing edge of the first blade.

7. The centrifugal compressor according to claim 6 , wherein

the shroud-side blade angle delta has a second peak disposed closer to the trailing edge than to the leading edge, the second peak being smaller than the largest shroud-side blade angle delta.

8. The centrifugal compressor according to claim 6 , wherein

the third position is located between 10% and 40% of a blade length of the first blade in the streamwise direction, where 0% corresponds to the leading edge and 100% corresponds to the trailing edge.

9. The centrifugal compressor according to claim 8 , wherein

the shroud-side blade angle delta is in a range of 6 to 14 degrees at the third position.

10. The centrifugal compressor according to claim 6 , wherein

a shroud-side wrap angle delta of each of the first blades from the mid-span position to the shroud portion varies along the streamwise direction such that the shroud-side wrap angle delta is largest at a fourth position closer to the leading edge than to the trailing edge.

11. The centrifugal compressor according to claim 1 , wherein the trailing edge of each of the first blades has a positive rake angle.

12. The centrifugal compressor according to claim 1 , further comprising

a second impeller attached to the shaft,

the second impeller being disposed between a second inlet portion and a second outlet portion of the casing, the second impeller being equipped with second blades, each of the second blades having a nonlinear shape in the quasi-orthogonal cross-sectional view, each of the second blades having a hub-side blade angle delta from a hub portion of the second impeller to a mid-span position of the second blade, the hub-side blade angle delta of each of the second blades varying along the streamwise direction such that the hub-side blade angle delta is largest at a fifth position closer to a leading edge of the second blade than to a trailing edge of the second blade.

13. The centrifugal compressor according to claim 12 , wherein

the first impeller and the second impeller are arranged back-to-back with the motor being disposed between the first impeller and the second impeller.

14. A method of producing refrigeration comprising:

compressing the low global warming potential (GWP) refrigerant within a chiller system that includes the centrifugal compressor according to claim 1 .

15. The method according to claim 14 , wherein

the first impeller is a closed type impeller including the hub portion and a shroud portion, the first blades being disposed between the hub portion and the shroud portion.

16. The method according to claim 15 , wherein

a curvature of the fully nonlinear shape in the quasi-orthogonal cross-sectional-view varies along a length of the quasi-orthogonal cross-sectional view from the hub portion to the shroud portion.

17. A refrigeration circuit comprising:

the centrifugal compressor according to claim 1 ;

a condenser;

an expansion valve;

an evaporator; and

piping connecting the centrifugal compressor, the condenser, the expansion valve, and the evaporator to form a loop, the refrigeration circuit containing the low global warming potential (GWP) refrigerant.