Impeller for axial flow pump
A rotor for an axial-flow blood pump has blades projecting outwardly from a hub and channels between the blades. The blades incorporate hydrodynamic bearing surfaces capable of suspending the rotor during operation. The rotor has a configuration which provides superior pumping action and reduced shear of blood passing through the pump. The forwardly facing pressure surfaces of the blades may include outflow corner surface at their downstream ends. The outflow corner surfaces desirably slope rearwardly and intersect the rearwardly-facing suction surfaces of the blades at outflow ends of the blades.
1. A rotor for an axial flow blood pump comprising:
a hub defining an upstream direction, a downstream direction, and an axis extending therethrough, the hub including a plurality of blades projecting therefrom, the plurality of blades including an inflow end and an outflow end opposite the inflow end and being rotatable around the axis in a forward direction and a rearward direction, each of the plurality of blades including:
a pressure surface facing in the forward direction, the pressure surface defining an outflow corner surface sloping in the rearward direction toward the outflow end, a vector normal to the outflow corner surface having positive, non-zero components in radially outward direction from each blade away from the axis and in the downstream direction;
a suction surface facing in the rearward direction;
the pressure surface and the suction surface of adjacent blades defining a channel therebetween; and
a tip surface between the pressure surface and the suction surface, the tip surface including a first hydrodynamic bearing surface and a second hydrodynamic bearing surface, the first and second hydrodynamic bearing surfaces encompassing a majority of the tip surface.
2. The rotor of claim 1 , wherein the tip surface defines an outermost extremity of each of the plurality of blades.
3. The rotor of claim 1 , wherein the tip surface of each blade of the plurality of blades has a cross-sectional area greater than a cross-sectional area defined by the channel defined between the suction surface and pressure surface of the adjacent one of the plurality of blades.
4. The rotor of claim 3 , wherein the hub defines a floor surface within the channel.
5. The rotor of claim 4 , further comprising a fillet forming a juncture between the floor surface within the channel and the outflow corner surface of the pressure surface at the outflow end of at least one of the plurality of blades.
6. The rotor of claim 4 , further comprising a fillet joining the suction surface of at least one of the plurality of blades and the floor surface of the channel.
7. The rotor of claim 1 , wherein the outflow corner surface of each of the plurality of blades is within 0.4 mm of the suction surface.
8. The rotor of claim 1 , wherein the outflow corner surface of each of the plurality of blades is within 0.15 mm of the suction surface.
9. The rotor of claim 1 , wherein the first hydrodynamic bearing surface of the tip surface extends in the rearward direction from the pressure surface.
10. The rotor of claim 1 , wherein the rotor includes an average outflow angle less than 30 degrees at the outflow end of the rotor.
11. The rotor of claim 1 , wherein the outflow corner surface is disposed at an outflow end of each blade.
12. A rotor for an axial flow blood pump comprising:
a hub defining an upstream direction, a downstream direction, and an axis extending therethrough;
a plurality of blades projecting from the hub, each of the plurality of blades including an inflow end, an outflow end opposite the inflow end, and a pressure surface defining an outflow corner surface at the outflow end sloping in the downstream direction, a vector normal to the outflow corner surface having positive, non-zero components in radially outward direction from each blade away from the axis and in the downstream direction; and
each of the plurality of blades includes a suction surface proximate a tip surface of each of the plurality of blades, the suction surface and the pressure surface of an adjacent one of the plurality of blades defining a channel therebetween, and the hub defining a floor surface within the channel, the tip surface of each of the plurality of blades includes a first hydrodynamic bearing surface and a second hydrodynamic bearing surface, the first and second hydrodynamic bearing surfaces encompassing substantially an entirety of the tip surface.
13. The rotor of claim 12 , wherein the plurality of blades are rotatable in a forward circumferential direction with respect to the axis and the outflow corner surface of each of the plurality of blades defines an outer curve at the outflow end and a curve diverging from the outer curve in the forward direction away from the axis in the downstream direction.
14. The rotor of claim 12 , wherein the tip surface of each blade of the plurality of blades has a cross-sectional area greater than a cross-sectional area defined by the channel defined between the suction surface and pressure surface of the adjacent one of the plurality of blades.
15. The rotor of claim 12 , further comprising a fillet forming a juncture between the floor surface and the outflow corner surface at the outflow end of at least one of the plurality of blades.
16. The rotor of claim 12 , wherein the channel includes a cross-sectional area narrowing in a direction from the inflow end of the plurality of blades to a mid-region of the rotor and widening in a direction from the mid-region of the rotor to the outflow end of the plurality of blades.
17. The rotor of claim 12 , further comprising an edge defining a junction between the outflow corner surface and the suction surface, the outflow corner surface defining a lead angle relative to the edge.
18. The rotor of claim 17 , wherein the outflow corner surface includes an inner end and an outer end opposite the inner end, and the lead angle decreases from the inner end to the outer end.
19. A rotor for an axial flow blood pump comprising:
a hub defining an upstream direction, a downstream direction, and an axis extending therethrough, the hub including a plurality of blades projecting therefrom, the plurality of blades including an inflow end and an outflow end opposite the inflow end and being rotatable around the axis in a forward direction and a rearward direction, each of the plurality of blades including:
a pressure surface facing in the forward direction, the pressure surface defining an outflow corner surface sloping away from the axis and in the rearward direction toward the outflow end, a vector normal to the outflow corner surface having positive, non-zero components in radially outward direction from each blade away from the axis and in the downstream direction;
a suction surface facing in the rearward direction, the pressure surface and the suction surface of an adjacent one of the plurality of blades defining a channel therebetween; and
a tip surface between the pressure surface and the suction surface, the tip surface defining an outermost extremity of each of the plurality of blades with respect to the axis and including a first hydrodynamic bearing surface and an immediately adjacent second hydrodynamic bearing surface, the first and second hydrodynamic bearing surfaces encompassing substantially an entirety of the tip surface.