Continuous curve high solidity hydrofoil impeller

An impeller for producing fluid flow in an axial direction relative to a shaft rotating on an axis, comprising:

• at least three blades, each said blade being of uniform thickness and extending outwardly along a respective radius relative to the axis of the shaft, each said blade being continuously curved to define a section of a regular cylinder, and having a leading edge and a trailing edge in a rotational direction of the shaft;
• said regular cylinder defining a roll axis for each said blade, the roll axis occupying a plane that lags said radius in the rotational direction of the shaft, by an offset angle;
• each of the blades defining a pitch angle relative to the radius, such that in the direction of axial flow, the leading edge precedes the radius and the trailing edge follows the radius;
• and
• a base member coupling between the blades and the shaft, each said blade and the base member abutting one another along a surface parallel to the plane of the roll axis.

A method for making an impeller for moving fluid in an axial direction relative to a shaft rotating on an axis, comprising the steps of:

• forming a plurality of blades for extending outwardly along a radius relative to the shaft, the blades each being formed from a sheet of uniform thickness, curved to conform to a section of a regular cylinder around a roll axis, the roll axis occupying a plane that lags said radius in a rotational direction of the shaft, by an offset angle, said forming step including cutting the sheet from flat stock, thereby defining a two dimensional contour, and rolling the sheet to conform to said section;
• pitching each of the blades about a respective said radius, such that in the direction of axial flow, the leading edge precedes the radius and the trailing edge follows the radius;
• and,
• attaching the blades to the shaft, including by affixing the sheet to a base member and coupling the base member to the shaft, the base member abutting the blade along at least one surface referenced to the roll axis and wherein said rolling is referenced to said at least one surface.