Patent Application
20130294916
The present disclosure generally relates to wind turbines, and more particularly, relates to inverted tooth silent drive chains for wind turbine powertrains.
Typical utility-scale wind turbines include a plurality of rotor blades which radially extend from a central rotor hub. The combined assembly of the rotor blades and the rotor hub is generally referred to as the rotor. The rotor blades aerodynamically interact with wind energy, creating lift and drag, which the rotor hub then translates into a driving torque. The driving torque is communicated from the rotor hub through a main shaft that is coupled to the rotor hub. The rotational torque is then distributed to one or more generators via a drivetrain or powertrain, which in turn produces electric power to be processed and transmitted to an associated electrical grid. The main shaft, the powertrain and the generators are all situated within a nacelle that is located on top of a tower.
It is a commonly shared interest to reduce the size and mass of components situated within the nacelle so as to minimize the costs associated with manufacturing, assembly, transportation, and the like. Among others, one of the larger components within the nacelle is the generator. Generators that are more directly driven by the main shaft of the wind turbine tend to be larger in size due to the lower operational speeds at which the blades and rotor hub drive the generator input. Thus, one way to enable significant reductions in generator size and mass is to increase the drive speed at the generator inputs to speeds that are compatible with smaller and lighter generators. This can be accomplished in one of a number of different ways, for example, using speed increasing powertrains consisting of gearboxes or drive chains configured to receive the lower rotational speed of the main shaft and supply a higher rotational drive speed to the generator inputs. While such configurations may prove to be adequate in certain respects, there is still much room for improvement.
Conventional gearboxes are commonly used to increase the speed of the main shaft of the wind turbine to a higher rotational speed that is compatible with conventional moderate to high speed electric power generators. However, the alignment of the gears in conventional gearboxes is critical for gear reliability. For instance, if any component in the gearbox, such as housings, gears, shafts, or the like, are deflected under a load during operation, the gears may become misaligned, resulting in substantial localized contact stresses. These stresses may further result in gear pitting and eventual gear failures. Gear misalignment problems become more prevalent in wind turbine applications, where the rotor hub assembly as well as the drive gear for the first stage speed increaser may be bolted or mounted to the input shaft of the gearbox assembly. As aerodynamic and gyroscopic loads are applied to the rotor hub assembly, the gearbox input shaft may be deformed by some finite amount, which tends to force the first stage drive gear out of alignment for the first stage driven gear.
As an alternative to less tolerant gearboxes, powertrains with roller drive chain configurations have also been considered and used to communicate rotor hub and main shaft rotations to generators. More specifically, these powertrains employ a drive sprocket that is rigidly coupled to the main shaft which rotatably engages a set of roller drive chains. The roller drive chains further engage a driven sprocket that is rigidly attached to a generator input such that rotations of the rotor hub and main shaft drive the generator and output electrical power. The geometry of roller drive chain configurations enables higher tolerance to misalignment, and thus, provides some benefits over the less tolerant conventional gearbox. However, roller drive chain configurations are only adequate for lower speed wind turbine operations and are not suited for moderate to high speed wind turbine operations. When used in higher speed, higher power applications, greater unidirectional accelerations are exerted on the rolling elements of the roller drive chains. This can lead to an asymmetric distribution of the rolling elements and lubrication fluids of the roller drive chain relative to the prescribed installation circumference, which can further result in binding as well as increased friction and wear on the rolling elements.
Accordingly, it would be beneficial to provide a powertrain which alleviates some of the disadvantages of conventional wind turbine powertrain applications. Specifically, there is a need for a powertrain which increases the rotational speed of the rotor hub and main shaft to speeds compatible with smaller and lighter generators. There is also a need for a powertrain that can support and safely handle low speed operations as well as high speed operations while reducing localized stresses on individual powertrain components. Moreover, there is a need for a speed increasing powertrain that is more tolerant to misalignments and thus more reliable.
In accordance with one aspect of the present disclosure, a speed increaser apparatus for a wind turbine is provided. The speed increaser apparatus may include at least one drive sprocket that is rotatably driven at least indirectly by a hub and a main shaft of the wind turbine, at least one driven sprocket that is rotatably driven by the drive sprocket, and at least one inverted tooth drive chain disposed at least partially about each of the drive and driven sprockets. The drive sprocket may be rotated at a first rotational speed in response to rotations of the main shaft. The driven sprocket may be rotated at a second rotational speed in response to rotations of the drive sprocket.
In accordance with another aspect of the present disclosure, a powertrain for a wind turbine is provided. The powertrain may include a first stage speed increaser and a second stage speed increaser in communication with the first stage speed increaser. The first stage speed increaser may include a first stage drive wheel being driven by a main shaft of the wind turbine, and at least one first stage driven wheel being driven by the first stage drive wheel through one or more roller drive chains. The second stage speed increaser may include a second stage drive wheel being driven by the first stage driven wheel, and at least one second stage driven wheel being driven by the second stage drive wheel through one or more inverted tooth drive chains.
In accordance with yet another aspect of the present disclosure, a wind turbine is provided. The wind turbine may include a hub, a main shaft rotating with the hub, a first stage speed increaser coupled to the main shaft, a second stage speed increaser coupled to the first stage speed increaser, and one or more generators being coupled to the second stage speed increaser. The first stage speed increaser may include a first stage drive wheel being driven by the main shaft, and at least one first stage driven wheel being driven by the first stage drive wheel through one or more roller drive chains. The second stage speed increaser may include a second stage drive wheel being driven by the first stage driven wheel, and at least one second stage driven wheel being driven by the second stage drive wheel through one or more inverted tooth drive chains.
Other advantages and features will be apparent from the following detailed description when read in conjunction with the attached drawings.
For a more complete understanding of the present disclosure, reference should be made to the embodiments illustrated in greater detail on the accompanying drawings, wherein:
While the following detailed description has been given and will be provided with respect to certain specific embodiments, it is to be understood that the scope of the disclosure should not be limited to such embodiments, but that the same are provided simply for enablement and best mode purposes. The breadth and spirit of the present disclosure is broader than the embodiments specifically disclosed and encompassed within the claims eventually appended hereto.
Referring to
As shown more particularly in
Still referring to
Similar to the first stage speed increaser 22, the second stage speed increaser 24 may also include a drive wheel 32 and a driven wheel 34. Specifically, the second stage drive wheel 32 may be rigidly coupled to and rotating with the first stage driven wheel 28, while the second stage driven wheel 34 may be rotatably coupled to the second stage drive wheel 32 through another set of drive chains 36. As shown, the first stage driven wheel 28 and the second stage drive wheel 32 may be coaxially coupled along a single shared drive shaft 38. However, in alternative embodiments, the first stage driven wheel 28 and the second stage drive wheel 32 may be coaxially disposed on and incorporated into a single drive wheel having a surface area configured to receive both drive chains 30, 36. The drive chains 32 of the second stage 24 may be at least partially engaged about each of the second stage drive and driven wheels 32, 34 such that any rotation of the first stage driven wheel 28 and the second stage drive wheel 32 causes a corresponding rotation in the second stage driven wheel 34. Additionally, the driven wheel 34 may be sized to have a circumference that is less than that of the drive wheel 32 such that the driven wheel 34 rotates at a speed that is greater than that of the corresponding drive wheel 32, but is also compatible for driving the inputs of lightweight generators 20. Correspondingly, each of the driven wheels 34 of the second stage 24 may be directly coupled to an input of one of the generators 20.
Turning to
Although other drive chains may be employed, the first stage speed increaser 22 may employ roller drive chains 30 and roller chain sprockets 40, 42 for their ability to maintain traction and alignment with relatively more consistency at such low rotational speeds. Furthermore, the use of roller drive chains 30 and roller chain sprockets 40, 42 may provide more tolerance to any deflection within the main shaft 14 resulting from aerodynamic and/or gyroscopic forces received at the blades 10 of the wind turbine 2. Additionally, while the embodiments of
With reference now to
While other drive chain configurations may be employed, the second stage speed increaser 24 may employ inverted tooth silent drive chains 36 and inverted tooth drive chain sprockets 50, 52 for their ability to more consistently maintain traction at moderate to high rotational speeds of operation. Furthermore, inverted tooth drive chains 36 may provide a drive configuration that is relatively more tolerant to misalignments as compared with conventional gearboxes configured for comparable speeds, as well as a more silent alternative to roller drive chain configurations. Additionally, while the embodiments of
Thus, the present disclosure sets forth an efficient as well as a reliable powertrain for wind turbine applications which enables the use of substantially smaller and lighter generators within the wind turbine nacelle. Moreover, the present disclosure provides a multi-stage speed increasing powertrain which effectively increases the rotational speed of the main shaft to drive speeds compatible with smaller lightweight generators. A first stage speed increaser of the powertrain comprises a roller drive chain configuration that is well adapted to receive the lower rotational speeds associated with the hub and the main shaft, while a second stage speed increaser of the powertrain comprises an inverted tooth silent drive chain configuration that is well adapted for more moderate to higher rotational speeds required by the smaller and lighter generators. By using at least two distinct drive chain configurations, each adapted for a different range of speed, the powertrain operates more effectively and more efficiently within a wider range of operating speeds. Furthermore, because the powertrain employs drive chains rather than conventional gearboxes to increase the speed, the powertrain is less prone to misalignments which may be caused by aerodynamic and/or gyroscopic forces exerted on the wind turbine. Still further, use of the inverted tooth silent drive chains enable high speed powertrain operations with significantly less noise being emitted from the nacelle of each wind turbine.
While only certain embodiments have been set forth, alternatives and modifications will be apparent from the above description to those skilled in the art. These and other alternatives are considered equivalents and within the spirit and scope of this disclosure and the appended claims.
