RIM DRIVEN THRUSTER HAVING PROPELLER DRIVE MODULES
A rim driven thruster comprises an annular housing, a propulsor assembly, a magnetic rotor assembly and a stator assembly. The annular housing defines a flow path extending along an axis. The propulsor assembly is supported within the housing and comprises propeller blades extending radially from the axis of the flow path. The propeller blades are configured to rotate about the axis. The magnetic rotor assembly is mounted to radially outer ends of the propeller blades. The stator assembly comprises spaced propeller drive modules mounted to an inner circumferential surface of the annular housing. The propeller drive modules are configured to provide electromagnetic torque to the magnetic rotor assembly.
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The present invention is directed generally to rim driven thrusters (RDT) used as propulsion systems for watercraft and the like. More particularly, the present invention relates to permanent magnet brushless motors for RDTs.
In rim driven thrusters, an electro-magnetic motor is integrated with propeller blade propulsors. In typical RDTs, a rotor assembly is integrated at outer diameter ends of the propeller blades and a stator assembly is integrated into a stationary annular housing surrounding the propeller blades. The stator assembly electro-magnetically causes the rotor assembly to rotate and generate propulsive thrust with the propeller blades. The housing is connected to the vessel through a pylon that rotates about a vertical axis so that the RDT is able to provide propulsion and steering in a single unit.
RDTs are advantageous for submerged operation because the electro-magnetic motor is removed from the center of the propulsor. In such a configuration, electrically active components of the stator assembly are positioned within the housing so as to be easily insulated. Moreover, the motor is positioned so as to minimize hydraulic drag. Specifically, the stator assembly is positioned within the annular housing and the rotor assembly is positioned in close proximity to the housing at the outer diameter of the blades. The stator and rotor assemblies are, however, still exposed to hydraulic drag when submerged. Thus, it becomes desirable to reduce the thickness of the rotor and stator assemblies to further minimize hydrodynamic losses.
Typical RDTs utilize conventional slotted stator cores in the stator assembly. In these designs, however, it is difficult to accommodate multiple windings in the narrow and shallow slots that are needed to achieve favorable thickness dimensions. Another proposal for reducing stator core thickness has included the use of a slot-less stator winding and spiral wound stator core laminations. This stator assembly design is expensive, difficult to manufacture and suitable only for small motors. There is, therefore, a need for a permanent magnet motor configuration having favorable hydraulic drag properties in an easily and inexpensively manufactured configuration.
SUMMARYThe present invention is directed to a rim driven thruster having propeller drive modules. The rim driven thruster comprises an annular housing, a propulsor assembly, a magnetic rotor assembly and a stator assembly. The annular housing defines a flow path extending along an axis. The propulsor assembly is supported within the housing and comprises propeller blades extending radially from the axis of the flow path. The propeller blades are configured to rotate about the axis. The magnetic rotor assembly is mounted to radially outer ends of the propeller blades. The stator assembly comprises spaced propeller drive modules mounted to an inner circumferential surface of the annular housing. The propeller drive modules are configured to provide electromagnetic torque to the magnetic rotor assembly.
RDT 10 provides propulsive power to vessel 12 by rotation of propellers 22. RDT 10 swivels about pylon 18 behind keel 16 to steer vessel 12. RDT 10 rotates on pylon 18 under an external power source such as provided from within vessel 12. Propellers 22 are rotated by an electro-magnetic motor integrated into rim 26 and housing 20. A stator core is mounted within housing 20 and receives electric power from vessel 12 through pylon 18. Magnetic forces from the stator core are transmitted to a rotor core mounted on rim 26. Rim 26 drives propellers to rotate on hub 24 within housing 20. Forward fairing 28A and aft fairing 28B provide hydrodynamic shields for housing 20, rim 26, the stator core and the rotor core.
RDT 10 provides hydrodynamic advantages to vessel 12 because the electro-magnetic motor is moved out of the center of the flow path provided within housing 20. As such, the effect of hub 24 on hydrodynamic drag within housing 20 is minimized. It is also desirable to reduce the hydrodynamic drag of housing 20. RDT 10 of the present invention utilizes propeller drive modules in the stator core that are spaced around the rotor core between rim 26 and housing 20 to reduce the cross-sectional area of the stator core. The spaced propeller drive modules form channels that reduce hydrodynamic drag produced by RDT 10.
Housing 20 circumscribes rotor assembly 32 to form gap G. Gap G comprises a flow space through which water or fluid in which RDT 10 is submerged is able to flow. As such, in other embodiments, forward fairing 28A and aft fairing 28B may be omitted during operation of RDT 10. The thicknesses of gap G, as well as rim 26, rotor assembly 32, propeller drive modules 30A-30D and housing 20 are not drawn to proportion in
Annular housing 20 is connected to vessel 12 (
Forward fairing 28A and aft fairing 28B are connected to housing 20 to provide hydrodynamic surfaces to RDT 10. Forward fairing 28A is connected to housing 20 at a forward end using any suitable attachment means, such as fasteners. Alternatively, forward fairing 28A may be integrated with housing 20. Forward fairing 28A is shaped to smoothly direct flow of water over RDT 10, while allowing water to enter housing 20 to engage propulsor assembly 36A. Aft fairing 28A is connected to housing 20 at an aft end using any suitable attachment means, such as fasteners. Aft fairing 28A is removable from housing 20 to provide access to propeller drive modules 30A and 30C and rotor assembly 32. Although, in other embodiments, aft fairing 28A may be integrated with housing 20 if access is provided elsewhere.
Housing 20 is spaced a distance away from rim 26 to form gap G, which forms a flow path in which fluid is able to flow. As shown in
Support brackets 38A and 38B extend radially inward from aft fairing 28B straight towards support ring 40A and across gap G. Support brackets 38A and 38B comprise two of three support brackets (the third not seen in the cross-section of
Propeller drive modules 30A and 30C are mounted to a radially inward facing surface of housing 20. Specifically, stator cores 50A and 50C are joined to housing 20 by any suitable means. Stator cores 50A and 50C comprise ferromagnetic material that is fashioned in the form of studs or blocks that protrude from housing 20. In the tangential, or circumferential, direction, stator cores 50A and 50C are spaced equally along housing 20 with open space being provided between to form channels 33A-33D (
Rotor assembly 32 is mounted to a radially outward facing surface of rim 26. Specifically, rotor core 42 is joined to rim 26 by any suitable means. Rotor core 42 comprises ferromagnetic material that is fashioned in the form of an annular ring that circumscribes rim 26. Rotor core 42 is positioned on rim 26 to align with stator cores 50A and 50C. Permanent magnet 44 is mounted to a radially outward face of rotor core 42 in a surface-mount configuration. In other embodiments, permanent magnet 44 may be mounted in a buried configuration. In yet another embodiment, rim 26 is omitted from propulsor assembly 36A and rotor core 42 is mounted directly to tips of propellers 22. The orientation of the magnetic poles of permanent magnet is in the circumferential direction.
Arranged as such within RDT 10, propeller drive modules 30A and 30C and rotor assembly 32 form a magneto-electric motor. Alternating electrical current is supplied directly to coil windings 52A and 52C such as from a power source in vessel 12 (
Forward fairing 28A includes bearing pad 58B located at an aft end so as to be positioned near rim 60B. Aft fairing 28B includes bearing pad 58A located at a forward end so as to be positioned near rim 60A. Aft fairing 28B also includes shield 66, which extends radially inward past bearing assembly 34C and alongside bearing rim 60A. Shield 66 protects bearing assembly 34C and provides a hydrodynamic surface. In other embodiments, shield 66 may be omitted from aft fairing 28B, as shown in
Rim 26 is supported by bearing assemblies 34C and 34D at bearing rims 60A and 60B. Bearing rims 60A and 60B comprise forward and aft axial extensions, respectively, of rim 26. Bearing rims 60A and 60B may be integral with rim 26 or separate components fastened to rim 26. Bearing rims 60A and 60B increase the available surface of rim 26 not used to support rotor assembly 32. Bearing rims 60A and 60B extend axially beyond propeller drive module 54A such that a radially outer surface faces towards forward fairing 28A and aft fairing 28B, respectively. Bearing rims 60A and 60B thus comprise annular rings against which bearing assemblies 34C and 34D engage.
Forward fairing 28A includes bearing pad 58B, and aft fairing 28B includes bearing pad 58A. Bearing pad 58B is integrally formed with forward fairing 28A, and bearing pad 58A is integrally formed with aft fairing 28B. In other embodiments, bearing pads 58A and 58B may comprise separate components or may be formed as part of housing 20. In any embodiment, bearing pads 58A and 58B comprise annular surfaces or lands against which bearing assemblies 34C and 34D engage. Thus, bearing assemblies 34C and 34D are positioned concentrically between rims 60A and 60B and pads 58A and 58B to permit propulsor assembly 36B to rotate within housing 20 when propeller drive module 54A is activated by rotor assembly 32. Specifically, propeller drive module 54A applies an electro-magnetic force to rotor assembly 32 to produce rotational movement of propellers 22 about center line CL.
Stator core 62A of propeller drive module 54A comprises a ferromagnetic core block that includes an arcuate surface that facing rotor assembly 32. A plurality of axial slots extend along the arcuate surface to provide spaces for coil windings. For example, coil winding 64A extends axially along stator core 62A. Thus, propeller drive module included a plurality of circumferentially spaced slots and associated coil windings as shown in
Arranged as such within RDT 10, propeller drive module 54A and rotor assembly 32 form a magneto-electric motor in the form of a linear actuator. Alternating electrical current is supplied directly to coil winding 64A such as from a power source in vessel 12 (
Construction and performance of RDT 10 benefits from propeller drive modules 30A-30D (
While the invention has been described with reference to an exemplary embodiment(s), it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment(s) disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.
Claims
1. A rim driven thruster comprising:
- an annular housing defining a flow path extending along an axis;
- a propulsor assembly supported within the annular housing, the propulsor assembly comprising propeller blades extending radially from the axis of the flow path and configured to rotate about the axis;
- a magnetic rotor assembly mounted to radially outer ends of the propeller blades; and
- a stator assembly comprising spaced propeller drive modules mounted to an inner circumferential surface of the annular housing and configured to provide electromagnetic torque to the magnetic rotor assembly.
2. The rim driven thruster of claim 1 wherein:
- the magnetic rotor assembly and the annular housing define a flow space within the rim driven thruster; and
- the spaced propeller drive modules form a plurality of channels within the flow space.
3. The rim driven thruster of claim 2 wherein the spaced propeller drive modules occupy less than half of the flow space.
4. The rim driven thruster of claim 1 wherein the spaced propeller drive modules are spaced equally around the inner circumference of the annular housing.
5. The rim driven thruster of claim 1 wherein the spaced propeller drive modules are spaced non-uniformly around the inner circumference of the annular housing.
6. The rim driven thruster of claim 1 wherein the spaced propeller drive modules comprise:
- a plurality of electro-magnets spaced about a circumference of the stator assembly.
7. The rim driven thruster of claim 2 wherein each of the electro-magnets comprises:
- a ferromagnetic core stud projecting from the annular housing; and
- a coil winding wrapped around the ferromagnetic core stud so as to extend in both axial and tangential directions.
8. The rim driven thruster of claim 1 wherein the spaced propeller drive modules comprise:
- a plurality of arc shaped linear actuators spaced about a circumference of the stator assembly.
9. The rim driven thruster of claim 8 wherein each of the plurality of arc shaped linear actuators comprises:
- a ferromagnetic core block comprising: an arcuate surface facing the rotor assembly; and a plurality of axially extending slots disposed in the arcuate surface; and
- a plurality of axially extending coils disposed in the plurality of axially extending slots.
10. The rim driven thruster of claim 1 wherein the propulsor assembly further comprises:
- a hub from which the propeller blades extend;
- a shaft extending through the hub;
- support brackets extending from the annular housing toward the shaft to support the propulsor assembly; and
- bearings positioned between the shaft and the support brackets.
11. The rim driven thruster of claim 1 wherein the propulsor assembly further comprises:
- a hub from which the propeller blades extend;
- a support rim surrounding the propulsor blades within the annular housing; and
- bearings supporting the propulsor assembly between the support rim and the annular housing.
12. A rim driven thruster comprising:
- an annular housing defining an axial flow path;
- a propulsor assembly comprising: a hub mounted co-axially within the annular housing; and a plurality of propeller blades extending radially out from the hub;
- a rotor assembly comprising: an annular rotor core connected to the plurality of propeller blades, wherein the annular rotor core and the annular housing define a flow path; and a plurality of permanent magnets disposed about the annular rotor core within the flow path; and
- a stator assembly comprising: a first propeller drive module connected to the annular housing in the flow path; and a second propeller drive module connected to the annular housing in the flow path to define a channel between the first and second propeller drive modules.
13. The rim driven thruster of claim 12 wherein the spaced propeller drive modules comprise:
- a plurality of electro-magnets spaced about a circumference of the stator assembly.
14. The rim driven thruster of claim 13 wherein each of the electro-magnets comprises:
- a ferromagnetic core stud projecting from the annular housing; and
- a coil winding wrapped around the ferromagnetic core stud so as to extend in both axial and tangential directions.
15. The rim driven thruster of claim 12 wherein the spaced propeller drive modules comprise:
- a plurality of arc shaped linear motor spaced about a circumference of the stator assembly.
16. The rim driven thruster of claim 15 wherein each of the plurality of arc shaped linear motor comprises:
- a ferromagnetic core block comprising: an arcuate surface facing the rotor assembly; and a plurality of axially extending slots disposed in the arcuate surface; and
- a plurality of axially extending coils disposed in the plurality of axially extending slots.
17. The rim driven thruster of claim 12 wherein the spaced propeller drive modules are spaced equally within the flow path.
18. The rim driven thruster of claim 12 wherein the spaced propeller drive modules are spaced non-uniformly within the flow path.
19. The rim driven thruster of claim 12 wherein the propulsor assembly further comprises:
- a shaft extending through the hub;
- support brackets extending from the annular housing toward the shaft to support the propulsor assembly; and
- bearings positioned between the shaft and the support brackets.
20. The rim driven thruster of claim 12 wherein the propulsor assembly further comprises:
- a support rim surrounding the propulsor blades within the annular housing; and
- bearings supporting the propulsor assembly between the support rim and the annular housing.
Type: Application
Filed: Oct 18, 2010
Publication Date: Apr 19, 2012
Applicant: HAMILTON SUNDSTRAND CORPORATION (Windsor Locks, CT)
Inventors: Jacek F. Gieras (Glastonbury, CT), Gregory I. Rozman (Rockford, IL)
Application Number: 12/906,793
International Classification: F04B 17/03 (20060101); B63H 23/24 (20060101);