Centrifugal impeller with controlled force balance

1. An impeller for a centrifugal pump comprising:

a disk-shaped shroud having a central axis, a front surface, a rear surface, and a circular perimeter;

a hub at the center of the shroud, the hub having an axial bore;

a first plurality of vanes on the front surface of the shroud, the first plurality of vanes extending radially inward from the perimeter towards the hub;

a second plurality of vanes on the rear surface of the shroud, the second plurality of vanes extending radially inward from the perimeter towards the hub

a balancing area on the rear surface of the shroud, the balancing area extending radially outward from the hub; and

a plurality of openings in the shroud, the plurality of openings configured to allow a fluid to pass from one side of the shroud to the other.

2. The impeller of claim 1 , wherein a diameter of the of the balancing area is defined by the inward extension of the second plurality of vanes.

3. The impeller of claim 1 , wherein the plurality of openings comprises a plurality of circular openings.

4. The impeller of claim 3 , wherein the plurality of circular openings comprises one or more circular openings having a first diameter, and one or more circular openings having a second diameter, wherein the first diameter is different from the second diameter.

5. The impeller of claim 3 , wherein the plurality of circular openings is spaced symmetrically around the circumference of the shroud.

6. The impeller of claim 5 , wherein at least one circular opening is located between each pair of adjacent vanes of the first plurality of vanes.

7. The impeller of claim 5 , wherein the plurality of circular openings comprises a first group and a second group, wherein each circular opening in the first group is located in a first region and each circular opening in the second group is located in a second region, wherein the first region is farther from the axis than the second region.

8. The impeller of claim 7 , wherein the number of circular openings in the second group is two thirds the number of circular openings in the first group.

9. The impeller of claim 1 , wherein the plurality of openings comprises a plurality of radially-extending slotted openings.

10. The impeller of claim 9 , wherein the diameter of the of the balancing area is defined by the inward extension of the slotted openings.

11. The impeller of claim 9 , wherein at least one slotted opening is located between each pair of adjacent vanes of the first plurality of vanes.

12. The impeller of claim 9 , wherein each of the plurality of radially-extending slotted openings is a curved slotted opening.

13. The impeller of claim 1 , wherein each of the first plurality of vanes is curved.

14. The impeller of claim 13 , wherein the plurality of vanes is evenly spaced around the circumference of the shroud.

15. The impeller of claim 14 , wherein the plurality of vanes comprise a group of long vanes and a group of short vanes.

16. The impeller of claim 15 , wherein the long vanes and short vanes are placed in an alternating sequence around the circumference of the shroud.

17. The impeller of claim 1 , wherein each of the second plurality of vanes is curved.

18. The impeller of claim 1 , wherein each of the first plurality of vanes extends in a direction substantially orthogonal to the front surface of the shroud, and wherein the degree of the extension defines the vane height.

19. The impeller of claim 18 , wherein the height of each vane of the first plurality of vanes tapers linearly from a maximum height near the hub to a minimum height at the perimeter.

20. The impeller of claim 1 , wherein each of the second plurality of vanes extends in a direction substantially orthogonal to the rear surface of the shroud.

21. The impeller of claim 1 , wherein the balancing area, when subjected to a pressure from the fluid, develops a force in an axial direction that opposes another axial force acting on the impeller.

22. A centrifugal pump comprising:

a driveshaft configured to be rotated;

a pump casing comprising:

an inlet;

an outlet;

and a chamber disposed between the inlet and outlet;

an impeller disposed in the pump casing and attached to the driveshaft, the impeller comprising;

a circular shroud having an central axis, a front surface, a rear surface, and a circular perimeter;

an eye at the center of the shroud, the eye having an axial bore;

a first set of vanes on the front surface of the shroud, the first set of vanes extending radially inward from the perimeter towards the hub;

a second set of vanes on the rear surface of the shroud, the second set of vanes extending radially inward from the perimeter towards the hub;

a balancing region on the rear surface of the shroud, the balancing region extending radially outward from the hub; and

a plurality of openings in the shroud, the plurality of openings configured to allow a fluid to pass from one side of the shroud to the other.

23. The centrifugal pump of claim 22 , wherein, during pump operation, axial forces on the impeller from plug load at the inlet are opposed by pressure-induced forces resulting from the fluid acting on the balancing region.

24. The centrifugal pump of claim 22 , wherein the surface area of the balancing region is defined by the inward extension of the second set of vanes.

25. The centrifugal pump of claim 22 , wherein the surface area of the balancing region is defined by the proximity of the plurality of openings to the eye.

26. The centrifugal pump of claim 22 , wherein each of the second set of vanes is curved.

27. The centrifugal pump of claim 22 , wherein each of the first set of vanes is curved.

28. The centrifugal pump of claim 22 , wherein the plurality of openings comprises a plurality of circular openings.

29. The centrifugal pump of claim 22 , wherein the plurality of openings comprises a plurality of radially-extending slotted openings.

30. The centrifugal pump of claim 29 , wherein each of the plurality of radially-extending slotted openings is a curved radially-extending slotted opening.