Patent Application
20070145751
This invention relates to the field of fluid power conversion and, more particularly, to electrical motor-driven fluid pumps and fluid-driven electrical power generation.
Fluid power conversion apparatus such as a turbine-generator combination or an electrically-driven continuous flow pump, an example of which is shown in
In both of these cases, the drawback of separating the functions of the motor and the pump (or the turbine and the generator) is that it requires that a shaft 102 pass through a housing penetration 100. Housing penetration 100 requires a rotary seal 101 between shaft 102 and housing 103 to prevent escape of the fluid or the ingress of ambient air. In both cases, an external bearing 104 is needed to support shaft 102 connected to impeller 107.
Another drawback of such systems is that a bend in the inlet or outlet duct 103 is needed to allow shaft 102 to exit in line with impeller 107, disturbing the natural flow direction of the fluid and adversely affecting efficiency. Also, the presence of shaft 102 in the flow creates turbulence and drag, also adversely affecting efficiency.
A further drawback is that the bend in duct 103 complicates the installation, especially in locations with tight space requirements. Installation with in-line flange connections is not possible.
Lastly, the motor or generator is a separate entity from the pump or turbine, requiring that these components be installed so as to maintain the alignment of the shafts of each of the pair of components. This requires that a coupling 108 be placed in between the pair of shafts. The motor and pump or turbine and generator need to be mounted to a common base (not shown) to maintain such alignment during operation and to transmit the generated torque from one to the other.
To adapt the high rotational speed of an electric motor/generator to the lower speed of the pump/turbine, a gearbox is frequently placed between pump/turbine and motor/generator, adding another component which then requires yet another coupling. Alignment between motor/generator and pump/turbine are required, and the torque compensation provided by a common base is also necessary.
An electric motor or generator rejects heat during the consumption or generation of electric power and requires the removal of the heat through an external cooling system for the motor or generator.
These drawbacks, which result in higher costs, inefficient operation and inefficient use of space, are summarized in the following list:
The present invention arranges the fluid power conversion apparatus by combining the impeller and the motor/generator rotor concentrically and in radially-coincidental planes whereby the armature windings are outside the fluid flow path at the pump periphery, and the armature is fixed to an outer housing. The motor/generator rotor is attached directly to the impeller at the periphery of the impeller blade tips.
The present invention eliminates all extraneous requirements of the conventional pump or turbine as described above, namely the drive shaft, the external bearing, the shaft seal, the bend in the duct, the installation and alignment of the motor/generator, a common installation base, a gearbox, and the external cooling requirements of the motor/generator. All of this is accomplished by integrating the motor/generator with the pump/turbine impeller in a more efficient and compact way.
The motor/generator rotor is affixed directly to the pump/turbine impeller and is “wet” (exposed to the fluid flow) while the armature with windings is located outside the fluid flow pump/turbine housing. The gap between armature and rotor is situated at a greater diameter from the centerline than is economically practical with a suitable conventional electric motor or generator so that more torque can be generated and more power can be transmitted at lower shaft speed than in an otherwise identical motor envelope. The fluid is forced through the rotor/armature gap to cool the motor/generator by the pressure difference between the intake and outlet side of the impeller. An impeller support bearing serves as a common bearing for both pump/turbine and motor/generator.
The wet rotor consists of magnets and encapsulating material and contains no electrical windings or brushes, thereby eliminating the need to keep the rotor dry. The larger diameter of the rotor of the electric motor/generator in combination with electronic speed control/power conditioning can perform the function of a conventional gearbox.
In a hollow rotor design that is entirely supported at the periphery, the bearing and the water seal are placed at the periphery of the rotor around the impeller. This requires an expensive, large diameter bearing and seal and is difficult to maintain over extended periods of operation. In the present invention, the impeller/rotor bearing is not placed at the periphery of the impeller but at the centerline of the pump/turbine, and the support is supplied by a hub held in place by the pump/turbine diffusor stator vanes.
U.S. Pat. No. 5,490,768 (Veronesi et al.) discloses an electrically-driven waterjet propulsion system in which the electric motor portion is placed forward of the pump over the reduced-diameter suction portion of the rotor. The rotating portion is supported by a peripheral bearing 54 as well as bearings 56 and 58 mounted inside the impeller hub 30. The combined arrangement, as a result of the motor portion being placed in front of the pump, considerably lengthens the waterjet intake. Moreover, it places the intake opening on the bottom of the vessel hull substantially farther forward, unfavorably affecting waterjet performance (increasing the likelihood of picking up boundary air at high speeds). Furthermore, placing the motor forward of the pump greatly increases the requirement for structural support and the complexity of additional structure, both resulting in increased weight and cost.
In addition, Veronesi et al. utilize water-lubricated bearings for each of the three bearings 54, 56 and 58. Water-lubricated bearings are by nature less precise than precision roller bearings, thus requiring both a larger gap tolerance and an impeller peripheral clearance, resulting in loss of overall system efficiency. Further, the AC-powered squirrel cage motor in such systems has severe limitations in power density (power output per volume of the apparatus), thus causing a scale mismatch between the capability of the electric motor and the waterjet positioned therein and powered thereby. The motor can only provide a fraction of the power that the waterjet would be capable of providing.
It is an object of this invention to provide a significantly more compact fluid power conversion apparatus applicable to a variety of fluid power conversion applications.
An important object of this invention is to provide a fluid power conversion apparatus which can be used as an electric marine propulsion apparatus of a simpler, more efficient and lower-cost design.
A further object of this invention is to provide a fluid power conversion apparatus which can operate as both a generator and a pump.
Another object of this invention is to provide a fluid power conversion apparatus which can be placed inline within a fluid duct with minimal external components.
Another object of this invention is to provide a fluid power conversion apparatus with lower acquisition, installation and maintenance costs.
Another object of this invention is to provide a fluid power conversion apparatus with many fewer components than conventional systems and with no external enclosure.
Another object of this invention is to provide a fluid power conversion apparatus that weighs much less than conventional systems.
Another object of this invention is to provide a fluid power conversion apparatus with higher efficiency than conventional systems.
Another object of this invention is to provide a fluid power conversion apparatus with higher power density and greater torque than conventional systems.
Other objects of this invention include eliminating the need for an external bearing, a bend in the duct, an external water seal, a drive shaft, shaft couplings, a gearbox, a common foundation, separate major system components, and an external cooling system.
A further object is to simplify the fluid power conversion apparatus in structural design so that components may be built of lower-cost, non-corroding lightweight composite components.
These and other objects of the invention will be apparent from the following descriptions and from the drawings.
The present invention is a fluid power conversion apparatus which can serve the functions of fluid pumping and/or power-generation. The inventive apparatus comprises: (a) an impeller having an impeller hub and a periphery; (b) a housing around the impeller; (c) a diffusor having an outer wall attached to the housing, a diffusor hub axially-aligned with the impeller hub, rotatable support of the impeller being provided only by a bearing assembly internal to the hubs, and at least one stator vane securing the diffusor hub to the outer wall; and (d) a rotating electrical machine having an armature attached to the housing and a rotor attached to the impeller periphery and positioned to form a gap between rotor and armature. The impeller and the rotor form an integrated unit.
In a preferred embodiment of the inventive apparatus, the armature includes radially-inward protrusions having laminations and windings, and the rotor includes two or more parallel magnetic rings configured to sandwich the protrusions therebetween, the rings each having a plurality of magnetic poles. In a highly preferred embodiment, the magnetic poles are aligned such that each magnetic north pole is aligned with a magnetic south pole on its neighboring ring(s).
In some embodiments, the rotating electrical machine is substantially centered over the bearing assembly.
In certain embodiments, the rotating electrical machine is an electric motor and the apparatus is used as a fluid pump. In certain of these embodiments, a portion of the fluid flows through the gap to cool the motor.
In certain embodiments, the apparatus, configured as a fluid pump, includes an intake duct and an exit nozzle and the apparatus is used for marine propulsion. In some such embodiments, the exit nozzle is under the water surface and the apparatus is used as an underwater thruster. In other such embodiments, the exit nozzle is above the water surface and the apparatus is used as a waterjet.
In certain preferred embodiments, the rotating electrical machine is a generator and the apparatus is used as a fluid-driven electrical power generator.
In preferred embodiments, the housing of the inventive apparatus includes at least two housing portions assembled to form the housing.
The term “turbine” is used to identify an appliance designed to be driven by fluid flow, recovering kinetic energy from this flow and turning it into a rotary output.
The term “impeller” refers to a driving (pump) and driven (turbine) rotating hydrodynamically-shaped rotary foil that can impart or recover kinetic energy to or from a fluid.
The term “pump/turbine” identifies the substantially-identical hardware the function of which is reversible: when driven by a rotary mechanical input, it pumps a fluid; when a fluid is driven through it, it produces a rotary mechanical output to, for example, drive an electric generator.
The term “motor/generator” identifies the substantially-identical hardware the function of which is reversible: it performs as a motor when electrical current is supplied and generates electrical current when driven by a rotary mechanical input.
The term “pump/motor” identifies the integrated pump and electric motor that is one embodiment of the present invention. The term “turbine/generator” identifies the integrated turbine and electric generator that is also an embodiment of the present invention. In each case, the physical hardware of such fluid power conversion apparatus is substantially identical.
Since the invention is a fluid power conversion apparatus that is reversible in function (producing a turbine generating electric current or an electric motor driving a continuous flow pump), the detailed description of either function is intended to cover both functions.
When operating in a pumping mode, the rotation of impeller 5 will force fluid F to flow in a direction 22, pressurizing the fluid down stream from impeller 5 in discharge pipe 3. The increased pressure will force a portion of fluid F to pass through gap 18 between rotor 20 and armature 16 and flow to the intake side of sleeve 10. This flow produces cooling for the armature 16 and rotor 20. Conversely, when operating in a power generating mode, fluid F flows in a direction 23 causing impeller 5 to rotate and creating a pressure differential across impeller 5, thereby forcing a portion of fluid F to pass through gap 18.
Rotor 20, armature 16 and gap 18 are shown in cylindrical shape; however, other embodiments may have tapered or curved shapes in place of the cylindrical shape shown.
In another embodiment in certain applications, rotor 20 and armature 16 must not be in the fluid environment of fluid F and can be isolated by means of a magnetic coupler including a magnetic outer coupling element 34 and a magnetic inner coupling element 35 as shown in
In another embodiment of the invention, the apparatus from integration of motor and pump is a marine underwater propulsor 50 as shown in
The identical embodiment described in the preceding paragraph can be an underwater power generating device by placing it fixedly under water in a river, tidal, pool or ocean current. Impeller 5 is now driven by the water current, and rotor 20 generates electricity in the windings of armature 16.
In yet another embodiment of the invention of pump/motor integration is a waterjet propulsor 60 as shown in
Armature 72 includes one or more sets 73 of laminations (four sets shown in
The magnetic field is concentrated between the magnetic poles N and S of rings 71 and oriented perpendicular to sets 74 of windings. Because of this arrangement, the strength of the magnetic field is not as dependent on the size of the gaps 76 between rings 71 and sets 73 of laminations. Magnetic flux is perpendicular to sets 74 of windings thereby producing maximum induced current (or torque) and yielding a high power density and power conversion efficiency.
While the principles of this invention have been described in connection with specific embodiments, it should be understood clearly that these descriptions are made only by way of example and are not intended to limit the scope of the invention.
This application is a continuation-in-part of U.S. patent application Ser. No. 11/217,808, filed on Sep. 1, 2005, now U.S. Pat. No. ______, issued on ______, the contents of which are incorporated by reference herein.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 11217808 | Sep 2005 | US |
| Child | 11680579 | Feb 2007 | US |
