Centrifugal blood pump impeller and flow path
An impeller and rotor structure for a magnetically levitated pump define a smooth primary flow path and U-shaped secondary flow path, which extends around an annular magnetic rotor. The u-shaped secondary flow path is defined by a large outer side gap along an outer surface of the rotor, a large bottom gap along a bottom surface of the rotor and a large inner gap along an inner surface of the rotor. Shroudless impeller blades are purely radial and overhung from a thin peripheral ring attached to the annular magnetic rotor. A center post having a low aspect ratio extends through the annular rotor. The low aspect ratio is configured to prevent flow in the primary flow path from colliding directly with flow in the secondary flow path at the inner radial gap.
1. A magnetic levitation pump apparatus, comprising:
an inlet cannula defining an axial inlet;
an annular magnetic rotor;
an impeller coupled to the magnetic rotor, the impeller includes:
a flat peripheral ring including a first surface coupled to the annular magnetic rotor, a second surface facing away from the annular magnetic rotor, and a central circular aperture concentrically aligned with the annular magnetic rotor, and
a plurality of blades extending from the peripheral ring inwardly towards an axis of rotation of the annular magnetic rotor,
wherein each of the blades includes:
a blade root surface facing the annular magnetic rotor and located in a first plane normal to the axis of rotation, and
a blade tip surface facing away from the annular magnetic rotor and located in a second plane normal to the axis of rotation, wherein the blade root surface and the blade tip surface are in parallel planes and define a purely radial inducerless characteristic of the plurality of blades; and
a nose cone portion extending through the central circular aperture of the flat peripheral ring, wherein a curved central portion of the nose cone extends axially beyond the plurality of blades and into the axial inlet.
2. The apparatus of claim 1 , wherein each of the blades further includes:
a trailing edge portion coupled to the second surface of the flat peripheral ring; and
a leading edge portion overhanging the central circular aperture of the flat peripheral ring.
3. The apparatus of claim 1 , wherein the blade tip surface of each of blades is shroud-less.
4. The apparatus of claim 1 , wherein the magnetic rotor includes magnetic portions and non-magnetic portions.
5. The apparatus of claim 1 , further comprising:
a housing portion including a center post and an annular cavity concentric with the center post, wherein the annular magnetic rotor is located in the annular cavity.
6. The apparatus of claim 5 , further comprising:
a secondary flow path in the annular cavity, the secondary flow path having a U-shaped cross-section and extending around the annular magnetic rotor from a first gap between the annular magnetic rotor and an outer surface of the annular cavity, to a second gap between the annular magnetic rotor and a bottom surface of the annular cavity, and to a third gap between the annular magnetic rotor and an inner surface of the annular cavity,
wherein the first gap, the second gap and the third gap are between about 0.010 inches and about 0.020 inches.
7. The apparatus of claim 5 , further comprising:
a secondary flow path in the annular cavity, the secondary flow path having a U-shaped cross-section and extending around the annular magnetic rotor from a first gap between the annular magnetic rotor and an outer surface of the annular cavity, to a second gap between the annular magnetic rotor and a bottom surface of the annular cavity, and to a third gap between the annular magnetic rotor and an inner surface of the annular cavity,
wherein the first gap, the second gap and the third gap are between about 0.005 inches and about 0.030 inches.
8. The apparatus of claim 2 , wherein the nose cone portion includes a substantially flat peripheral portion overlapping the leading edge portion of each of the blades and defining a constant gap between the nose cone portion and the blades.
9. The apparatus of claim 8 , wherein the curved central portion of the nose cone extends into the axial inlet and corresponds to an internal curvature of the inlet cannula to define a substantially smooth spacing between the nose cone and the inlet cannula.
10. The apparatus of claim 9 , comprising:
a volute extending partially around a periphery of the impeller and in fluid communication with the axial inlet, wherein the impeller and volute define a primary flow path.
11. The apparatus of claim 7 , wherein the third gap is located radially outward from the curved central portion of the nose cone.
12. The apparatus of claim 7 , wherein the third gap is located radially outward from the inlet cannula.