VCT pump impeller having monotonically decreasing head with increasing flow rate

A method of designing a VCT pump configured to meet specified requirements of a VCT pump application by vertically pumping a process fluid, while providing a monotonically decreasing head as a function of a flow rate of the process fluid over a range of flow rates of the process fluid from zero flow to a flow rate that is beyond a best efficiency point (BEP) flow rate of the VCT pump, the method comprising:

• A) determining an initial candidate pump design having an initial candidate impeller design, the candidate impeller design comprising a plurality of identical blades equally spaced about, and extending radially outward from, a central hub, each of the blades having a candidate blade shape comprising a pressure blade side and a suction blade side, each of the pressure and suction blade sides comprising a plurality of streamlines extending from a leading edge thereof to a trailing edge thereof, the plurality of streamlines comprising a shroud streamline at a radially outward edge of the blade side, a hub streamline along a radially inward edge of the blade side, and a mean streamline equally spaced apart from the shroud and hub streamlines, wherein all of the shroud streamlines and the mean streamlines are S-shaped, having blade angles that increase from the leading edge to an inflection point and decrease from the inflection point to the trailing edge, or having blade angles that decrease from the leading edge to an inflection point and increase from the inflection point to the trailing edge;
• and
• wherein all of the inflection points on all of the shroud and mean streamlines are between the exit throat and the trailing edge;
• B) determining whether the candidate pump design meets all of the specified requirements of the VCT pump application by applying computational fluid dynamics (CFD) to the candidate impeller design, and if not then modifying the candidate impeller design and repeating step B);
• C) if the candidate pump design meets all of the specified requirements of the VCT pump application, applying CFD to determine if a head vs flow rate curve of the candidate pump design is monotonic from zero flow to a flow rate that is beyond a best efficiency point (BEP) flow rate of the candidate pump design, and if not, then moving at least one of the inflection points of the shroud and mean streamlines of the candidate impeller design to a different location between the exit gate and the trailing edge, and repeating steps B) and C) until a successful VCT pump design is identified.