Waterjet propulsor with shaft fairing device

• US 8,932,092 B1
• Filed: 06/18/2013
• Issued: 01/13/2015
• Est. Priority Date: 06/18/2013
• Status: Active Grant

• Current Assignee: the united states of america as represented by the secretary of the navy
• Original Assignee: the united states of america as represented by the secretary of the navy
• Inventors: Sadowski, Thaddeus J.
• Primary Examiner(s): AVILA, STEPHEN P
• Application Number:
  US13/920,214
• Time in Patent Office: 574 Days
• Field of Search: 114/243, 440/38, 440/66, 440/83
• US Class Current: 440/38
• CPC Class Codes: B63H 11/08 of rotary type
• CPC Class Codes: B63H 2011/081 with axial flow, i.e. the axis of rotation being parallel to the flow direction

Abstract

The invention is directed to a waterjet propulsor. The propulsor includes a structure covering an impeller shaft. The implementation of the elongated structure results in reduced drag, increased thrust and increased craft speed. The elongated structure may be a sleeve that is mounted in a free-floating arrangement over the impeller shaft that self-aligns, the sleeve having an airfoil cross section for optimizing the flow of water over the shaft. The elongated structure may also be a fixed housing arrangement that includes an airfoil cross section for optimizing the flow of water over the shaft.

Claims

1. A waterjet propulsor comprising:

a frame having a forward end, an aft end, an upper end, and a lower end;

a nozzle assembly located at the aft end of the frame;

an impeller assembly comprising;

a forward impeller bearing arrangement at the forward end of the frame;

an aft impeller bearing arrangement at the aft end of the frame;

an impeller shaft extending from the forward end of the frame to the aft end of the frame in a longitudinal direction X and mounted within each of the forward impeller bearing arrangement and the aft impeller bearing arrangement; and

an impeller blade assembly comprising a central hub and a plurality of blades attached to the central hub, wherein the central hub is supported on the impeller shaft;

a water intake extending from the lower end of the frame towards the impeller, the water intake having intake walls forming a conduit, wherein the conduit is angled to create an intake flow F_I having flow vectors in perpendicular X, Y, and Z axes, and wherein intake flow F_I-xy in the X-Y plane impinges on the impeller shaft at an angle α

with respect to the longitudinal direction X of the shaft;

an elongated structure positioned over the impeller shaft, wherein the elongated structure has an airfoil cross section in the Y-Z plane, the elongated structure further comprising an offset streamlined airfoil cross section aligned with the intake flow angle α

, so that the intake flow F_I-xy flows over the elongated structure in a path defined by the offset streamlined airfoil cross section, thereby minimizing the deleterious flow effects caused by the shaft, and increasing the efficiency of the propulsor.

2. The waterjet propulsor of claim 1, wherein the elongated structure is an elongated sleeve positioned over the impeller shaft so that the impeller shaft and the elongated sleeve are freely rotatable with respect to each other.

3. The waterjet propulsor of claim 2, wherein the elongated sleeve is mounted over the impeller shaft in a free-floating arrangement wherein the elongated sleeve has an inner diameter D_SL that is larger than the outer diameter of the impeller shaft D_SH, and wherein in operation there is a running clearance between the elongated sleeve and the impeller shaft because of the difference in diameters, the running clearance filled with water from the intake flow F_I acting as a lubricant between the elongated sleeve and the impeller shaft, and wherein the elongated sleeve is positioned on the impeller shaft between an abutment portion of the frame and the impeller blade assembly to prevent axial movement of the elongated sleeve along the impeller shaft.

4. The waterjet propulsor of claim 3, wherein the elongated sleeve is rotatably adjustable to adjust for the intake flow F_I-yz in the Y-Z plane, and wherein when the intake flow F_I-yz contacts the elongated sleeve at an angle θ

with respect to a chord of the airfoil cross section, the elongated sleeve rotates by an angle of about θ

to ensure that the angle between the intake flow and the chord is zero, thereby aligning the elongated sleeve with intake flow.

5. The waterjet propulsor of claim 1, wherein the elongated structure is rigidly attached to the frame, extending from the forward end of the frame towards impeller blade assembly.

14. The waterjet propulsor of claim 4, wherein the elongated sleeve is an ultra-high molecular weight polyethylene, and the offset streamlined airfoil cross section is a NACA 0030 profile.

15. The waterjet propulsor of claim 5, wherein the offset streamlined airfoil cross section is a NACA 0030 profile.

6. A method of optimizing the flow within a waterjet propulsor, the method comprising:

providing a waterjet propulsor comprising;

a frame having a forward end, an aft end, an upper end, and a lower end;

a nozzle assembly located at the aft end of the frame;

an impeller assembly comprising;

a forward impeller bearing arrangement at the forward end of the frame;

an aft impeller bearing arrangement at the aft end of the frame;

an impeller shaft extending from the forward end of the frame to the aft end of the frame in a longitudinal direction X and mounted within each of the forward impeller bearing arrangement and the aft impeller bearing arrangement; and

an impeller blade assembly comprising a central hub and a plurality of blades attached to the central hub, wherein the central hub is supported on the impeller shaft;

a water intake extending from the lower end of the frame towards the impeller, the water intake having intake walls forming a conduit, wherein the conduit is angled to create an intake flow F_I having flow vectors in perpendicular X, Y, and Z axes;

providing an elongated structure positioned over the impeller shaft, wherein the elongated structure has an airfoil cross section in the Y-Z plane;

directing the intake flow F_I having intake flow vector F_I-xy in the X-Y plane into the waterjet propulsor, the intake flow F_I-xy impinging on the impeller shaft at an angle α

with respect to the longitudinal direction X of the shaft, wherein the elongated structure further comprises an offset streamlined airfoil cross section aligned with the intake flow angle α

, so that the intake flow F_I-xy flows over the elongated structure in a path defined by offset streamlined airfoil cross section, thereby minimizing the deleterious flow effects caused by the shaft, and increasing the efficiency of the propulsor.

7. The method of optimizing the flow of claim 6, wherein the elongated structure is an elongated sleeve, the method further comprising positioning the elongated sleeve over the impeller shaft so that the impeller shaft and the elongated sleeve are freely rotatable with respect to each other.

8. The method of optimizing the flow of claim 7, wherein in the positioning of the elongated sleeve over the impeller shaft, the impeller shaft is provided in a free-floating arrangement wherein the elongated sleeve has an inner diameter D_SL that is larger than the outer diameter of the impeller shaft D_SH, and wherein there is a running clearance between the elongated sleeve and the impeller shaft because of the difference in diameters, the running clearance filled with water from the intake flow F_I acting as a lubricant between the elongated sleeve and the impeller shaft, and wherein the elongated sleeve is positioned on the impeller shaft between an abutment portion of the frame and the impeller blade assembly to prevent axial movement of the elongated sleeve along the impeller shaft.

9. The method of optimizing the flow of claim 8, wherein the elongated sleeve is provided to be rotatably adjustable to adjust for the intake flow F_I-yz in the Y-Z plane, and wherein when the intake flow F_I-yz contacts the elongated sleeve at an angle θ

with respect to a chord of the airfoil cross section, the elongated sleeve rotates by an angle of about θ

to ensure that the angle between the intake flow and the chord is zero, thereby aligning the elongated sleeve with intake flow.

10. The method of optimizing the flow of claim 6, wherein the elongated structure is rigidly attached to the frame, extending from the forward end of the frame towards impeller blade assembly.

16. The method of optimizing the flow of claim 9, wherein the elongated sleeve is an ultra-high molecular weight polyethylene, and the offset streamlined airfoil cross section is a NACA 0030 profile.

11. An elongated sleeve for optimizing an airflow in a waterjet propulsor having a frame with a forward end, an aft end, an upper end, and a lower end, a nozzle assembly located at the aft end of the frame, and an impeller assembly comprising a forward impeller bearing arrangement at the forward end of the frame, an aft impeller bearing arrangement at the aft end of the frame, an impeller shaft extending from the forward end of the frame to the aft end of the frame in a longitudinal direction X and mounted within each of the forward impeller bearing arrangement and the aft impeller bearing arrangement, and an impeller blade assembly comprising a central hub and a plurality of blades attached to the central hub, wherein the central hub is supported on the impeller shaft, the waterjet propulsor further comprising a water intake extending from the lower end of the frame towards the impeller, the water intake having intake walls forming a conduit, wherein the conduit is angled to create an intake flow F_I having flow vectors in perpendicular X, Y, and Z axes, and wherein intake flow F_I-xy in the X-Y plane impinges on the impeller shaft at an angle α

with respect to the longitudinal direction X of the shaft, the elongated sleeve positioned over the impeller shaft and having;

an airfoil cross section in the Y-Z plane, the elongated sleeve further comprising an offset streamlined airfoil cross section with a NACA 0030 profile aligned with the intake flow angle α

, so that the intake flow F_I-xy flows over elongated sleeve in a path defined by offset streamlined airfoil cross sections, thereby minimizing the deleterious flow effects caused by the shaft, and increasing the efficiency of the propulsor.

12. The elongated sleeve of claim 11, wherein the elongated sleeve is mounted over the impeller shaft in a free-floating arrangement wherein the elongated sleeve has an inner diameter D_SL that is larger than the outer diameter of the impeller shaft D_SH, and wherein in operation there is a running clearance between the elongated sleeve and the impeller shaft because of the difference in diameters, the gap filled with water from the intake flow F_I acting as a lubricant between the elongated sleeve and the impeller shaft, and wherein the elongated sleeve is positioned on the impeller shaft between an abutment portion of the frame and the impeller blade assembly to prevent axial movement of the elongated sleeve along the impeller shaft.

13. The elongated sleeve of claim 12, wherein the elongated sleeve is rotatably adjustable to adjust for the intake flow F_I-xy in the Y-Z plane, and wherein when the intake flow F_I-xy contacts the elongated sleeve at an angle θ

with respect to a chord of the airfoil cross section, the elongated sleeve rotates by an angle of about 0 to ensure that the angle between the intake flow and the chord is zero, thereby aligning the elongated sleeve with intake flow.