Turbomachine with mixed-flow stage and method

1. A turbomachine for imparting energy to a multiphase fluid, the multiphase fluid comprising at least a liquid phase and a gaseous phase, the turbomachine comprising:

a casing having an inlet and an outlet;

an axial stage part comprising at least one axial stage;

a mixed-flow stage part comprising at least one mixed-flow stages fluidly connected to the axial stage part;

a centrifugal stage part comprising at least one centrifugal stage fluidly connected to the mixed-flow stage part;

a shaft connecting the axial stage part, the mixed-flow stage part, and the centrifugal stage part;

wherein the at least one axial stage is defined by an angle between an axial impeller outlet flow and an axis parallel to a rotational axis of the shaft having a value between 0° and 5°;

the at least one mixed-flow stage is defined by an angle between a mixed-flow impeller outlet flow and the axis parallel to the rotational axis of the shaft having a value between 5° and 80°; and

the at least one centrifugal stage is defined by an angle between a centrifugal impeller outlet flow and the axis parallel to the rotational axis of the shaft having a value between 80° and 90°;

wherein the angles of the axial, the mixed-flow, and the centrifugal stage part are configured to correlate with Gas-Volume-Fraction (GVF) values of the multiphase fluid, and

wherein GVF is a ratio of gaseous phase to liquid phase volume rates of the multiphase fluid.

2. The turbomachine of claim 1 , wherein the axial stage part comprises at least two axial stages, and the centrifugal stage part comprises at least two centrifugal stages.

3. The turbomachine of claim 2 , wherein each stage comprises a rotor having impellers that are configured to rotate with the shaft and a diffuser fixed to the casing and configured to change a direction of a corresponding flow.

4. The turbomachine of claim 1 , wherein the inlet is axial and the outlet is radial.

5. The turbomachine of claim 1 , further comprising:

an adjusting part between the axial stage part and the mixed-flow stage part.

6. The turbomachine of claim 1 , wherein a transition from the axial stage part to the mixed-flow stage part takes place when a Gas-Volume-Fraction (GVF) value of the multiphase fluid reaches a threshold value, wherein the threshold value is determined based on a correlation between the CAT value and a relative pressure rise across the axial and the mixed-flow stage part.

7. The turbomachine of claim 1 , wherein the angle of the mixed-flow stage has a value between 20° and 60°.

8. A method for imparting energy to a multiphase fluid, the multiphase fluid comprising at least a liquid phase and a gaseous phase, the method comprising:

fluidly connecting an axial stage part to a mixed-flow stage part and to a centrifugal stage part in this order, the mixed flow stage part comprising a plurality of mixed flow stages;

providing the axial stage part, the mixed-flow stage part and the centrifugal stage part into a casing having an inlet and an outlet; and

connecting an axial impeller of the axial stage part, a mixed-flow impeller of the mixed-flow stage part, and a centrifugal impeller of the centrifugal stage part to a shaft,

wherein the axial stage part is defined by an angle between an axial impeller outlet flow and an axis parallel to a rotational axis of the shaft having a value between 0° and 5°,

the mixed-flow stage part is defined by an angle between a mixed-flow impeller outlet flow and the axis parallel to the rotational axis of the shaft having a value between 5° and 80°, and

the centrifugal stage part is defined by an angle between a centrifugal impeller outlet flow and the axis parallel to the rotational axis of the shaft having a value between 80° and 90°;

wherein the angles of the axial, the mixed-flow, and the centrifugal stage part are configured to correlate with Gas-Volume-Fraction (GVF) values of the multiphase fluid, and

wherein GVF is a ratio of gaseous phase to liquid phase volume rates of the multiphase fluid.

9. The method of claim 8 , wherein the axial stage part comprises at least two axial stages, and the centrifugal stage part comprises at least two centrifugal stages.

10. The method of claim 9 , wherein each stage comprises a rotor having impellers that are configured to rotate with the shaft and a diffuser fixed to the casing and configured to change a direction of a corresponding flow.

11. The method of claim 8 , wherein the inlet is axial and the outlet is radial.

12. The method of claim 8 , further comprising:

adjusting the axial stage part and the mixed-flow stage part.

13. The method of claim 8 , wherein a transition from the axial stage part to the mixed-flow stage part takes place when a Gas-Volume-Fraction (GVF) value of the multiphase fluid reaches a threshold value, wherein the threshold value is determined based on a correlation between the CAT value and a relative pressure rise across the axial and the mixed-flow stage part.

14. The method of claim 8 , wherein the angle of the mixed-flow stage has a. value between 20° and 60°.

15. A turbomachine for imparting energy to a multiphase fluid, the multiphase fluid comprising at least a liquid phase and a gaseous phase, the turbomachine comprising:

a casing having an inlet and an outlet;

an axial stage part comprising at least one axial stage and configured to receive the multiphase fluid via the inlet;

a mixed-flow stage part fluidly connected to the axial stage part, the mixed-flow stage part comprising at least one mixed-flow stage;

a shaft connecting the axial stage part and the mixed-flow stage part;

wherein the at least one axial stage is defined by an angle between an axial impeller outlet flow and an axis parallel to a rotational axis of the shaft having a value between 0° and 5°; and

the at least one mixed-flow stage is defined by an angle between a mixed-flow impeller outlet flow and the axis parallel to the rotational axis of the shaft having a value between 5° and 80°;

wherein the angles of the axial and the mixed-flow stage part are configured to correlate with Gas-Volume-Fraction (GVF) values of the multiphase fluid, and

wherein GVF is a ratio of gaseous phase to liquid phase volume rates of the multiphase fluid.

16. The turbomachine of claim 15 , wherein the axial stage part comprises at least two axial stages.

17. The turbomachine of claim 16 , wherein each stage comprises a rotor having impellers that are configured to rotate with the shaft and a diffuser fixed to the casing and configured to change a direction of a corresponding flow.

18. The turbomachine of claim 15 , wherein the inlet is axial and the outlet is radial.

19. The turbomachine of claim 15 , wherein the axial stage part comprises at least two axial stages, and the centrifugal stage part comprises at least two centrifugal stages.

20. A turbomachine for imparting energy to a multiphase fluid, the multiphase fluid comprising at least a liquid phase and a gaseous phase, the turbomachine comprising:

a casing having an inlet and an outlet;

a mixed-flow stage part, the mixed-flow stage part comprising at least one mixed-flow stage;

a centrifugal stage part comprising at least one centrifugal stage fluidly connected to the mixed-flow stage part;

a shaft connecting, the mixed-flow stage part and the centrifugal stage part;

wherein

the at least one mixed-flow stage is defined by an angle between a mixed-flow impeller outlet flow and the axis parallel to the rotational axis of the shaft having a value between 5° and 80°; and

the at least one centrifugal stage is defined by an angle between a centrifugal impeller outlet flow and the axis parallel to the rotational axis of the shaft having a value between 80° and 90°,

wherein the angles of the mixed-flow and the centrifugal stage parts are configured to correlate with Gas-Volume-Fraction (GVF) values of the multiphase fluid, and

wherein GVF is a ratio of gaseous phase to liquid phase volume rates of the multiphase fluid.