Centrifugal pump stage with radiused impeller flow passage exit for reduced erosion

A method of assembling an electric pump, comprising:

• coupling a first drive shaft of an electric motor to a second drive shaft of a seal section;
• and
• coupling the second drive shaft to a third drive shaft disposed at least partly within a housing containing a centrifugal pump stage, wherein the centrifugal pump stage comprises:
• an impeller rotationally coupled to the third drive shaft, wherein the impeller comprises:
• a first hub;
• a first shroud concentrically disposed about the first hub and comprising a first axial end and a second axial end, wherein the second axial end is disposed radially outward with respect to the first axial end;
• and
• first vanes extending from the first hub to the first shroud;
• and
• a diffuser fluidly coupled to the impeller and comprising:
• a second hub;
• a second shroud concentrically disposed about the second hub;
• and
• second vanes extending from the second hub to the second shroud,
• wherein a slope of an interior surface of the first shroud proximate the second axial end is within 20 degrees of being parallel to a longitudinal axis of the third drive shaft so that when the impeller rotates, flow entering a volume between the second hub and the second shroud has a velocity comprising a radial component and an axial component, and a magnitude of the radial component is less than 15% of the magnitude of the axial component.

A method of lifting fluid in a wellbore, comprising:

• running an electric submersible pump into a wellbore, wherein the electric submersible pump comprises:
• a shaft;
• a motor mechanically coupled to the shaft;
• an impeller rotationally coupled to the shaft, wherein the impeller comprises:
• a first hub;
• a first shroud concentrically disposed about the first hub and comprising a first axial end and a second axial end, wherein the second axial end is disposed radially outward with respect to the first axial end;
• and
• first vanes extending from the first hub to the first shroud;
• and
• a diffuser fluidly coupled to the impeller and comprising:
• a second hub;
• a second shroud concentrically disposed about the second hub;
• and
• second vanes extending from the second hub to the second shroud;
• and
• providing electric power to the motor to drive the shaft to rotate the impeller to induce flow in a fluid passageway defined by the first hub, the first shroud, the first vanes, the second hub, the second shroud, and the second vanes,
• wherein an inflection point at which radially outward flow transitions to radially inward flow occurs proximate to the second axial end,
• wherein flow entering a volume between the second hub and the second shroud has a velocity comprising a radial component and an axial component, and
• wherein a magnitude of the radial component is less than 15% of the magnitude of the axial component.