Patent Application
20110138951
The apparatus described herein relates generally to a wind turbine. More specifically, the apparatus relates to a wind turbine having a gear with a wear indicator.
Recently, wind turbines have received increased attention as environmentally safe and relatively inexpensive alternative energy sources. Wind turbines do not emit greenhouse gases (GHGs), and therefore, do not contribute to global warming. With the growing interest in wind generated electricity, considerable efforts have been made to develop wind turbines that are reliable and efficient.
Wind is usually considered to be a form of solar energy caused by uneven heating of the atmosphere by the sun, irregularities of the earth's surface, and rotation of the earth. Wind flow patterns are modified by the earth's terrain, bodies of water, and vegetation. The terms wind energy or wind power, describe the process by which the wind is used to rotate a shaft and subsequently generate mechanical power or electricity.
Typically, wind turbines are used to convert the kinetic energy in the wind into mechanical power. This mechanical power may be used for specific tasks (such as grinding grain or pumping water) or a generator may convert this mechanical power (i.e., the rotation of a shaft) into electricity. A wind turbine usually includes an aerodynamic mechanism (e.g., blades) for converting the movement of air into a mechanical motion (e.g., rotation), which is then converted with a generator into electrical power. Power output from the generator is proportional to the cube of the wind speed. As wind speed doubles, the capacity of wind generators increases almost eightfold.
The majority of commercially available wind turbines utilize geared drive trains to connect the turbine blades to the electrical generators. The wind turns the turbine blades, which spin a low speed shaft, which feeds into a gearbox having a higher speed output shaft. This higher speed output shaft connects to a generator and makes electricity. The geared drive aims to increase the velocity of the mechanical motion.
The industry standard drive train for large (e.g., >1.5 MW) wind turbines consists of discrete gearbox and generator units that are separately mounted to a mainframe (also commonly called a bedframe or bedplate). Power is transferred from the gearbox to the generator via a flexible “high-speed” shaft coupling. This arrangement forces the gearbox and generator to be physically distanced from each other, as well as, requires both the output shaft of the gearbox and the input shaft of the generator to be separately supported by gearbox bearings and generator bearings, respectively.
In an aspect of the present invention, a wind turbine is provided having a tower, a nacelle supported by the tower and a rotor with one or more blades and a hub. A gearbox is connected to the rotor and includes one or more gears having at least one wear indicating line that facilitates identification of gear wear. The wear indicating line is located on side surfaces of the gears.
In another aspect of the present invention, a gearbox for a wind turbine is provided having one or more gears with wear indicating lines that facilitate identification of gear wear. The wear indicating lines are located on side surfaces of the gears.
A horizontal axis wind turbine (HAWT) 100 is illustrated in
The blades 130 are connected to the hub 140, and the hub may contain a pitch control mechanism to control the pitch angle of each blade. Typically, three blades are employed in most commercial wind turbines, however, one, two or four or more blades could be employed as well. The blades convert the kinetic energy of the wind into mechanical energy by rotating a low speed shaft. Blades may be manufactured from fiberglass or graphite composites, fiberglass reinforced plastics or wood/epoxy laminates, or other suitable materials. The low speed shaft is connected to the hub 140 typically via a bolted flange coupling.
Generators are used to convert the rotation of a shaft into electrical energy. A gearbox is typically used to increase the speed of the input shaft to the generator. The gearbox has the low speed shaft as its input, and the output is a higher speed shaft, which according to aspects of the present invention, can feed directly into the generator.
The gearbox 202 may be any suitable type of gearbox including, but not limited to parallel-shaft gearboxes and planetary gearboxes. The gearbox may have, one, two, three or more stages, although for a large wind turbine three or fewer stages are preferred. The individual gears (e.g., low speed shaft gear, high speed shaft gear, sun gear, planetary gear, ring gear, etc.) include a number of teeth that engage the teeth of adjacent gears. For example, the teeth on sun gear 250 engage the teeth on planetary gear 242.
During operation of the wind turbine, the gears of the gearbox 202 can experience wear. It is important to monitor this wear and repair or replace any gears that are out of specification. However, to date it has been difficult to determine how much wear has occurred on the gears. One known solution has required a technician to use a template where the gear impression was machined in and then the gap between the template and the gear tooth would be measured using feeler gauges. However, this process can return variable results based on the specific technician performing the measurement.
An improved gear 300 is illustrated in
The wear indicating lines can be recessed into the gear surface and be formed by grooves or inscribed lines.
However, in some applications it may be desirable to have wear indicating lines protrude from the gear surface.
The roughened surface wear indicating line 920 can provide good contrast between the line 920 and nearby portions of the tooth 910 or gear 900. As most gears will have a coating of lubricant (e.g., oil), the roughened surface will tend to retain more lubricant than the surrounding smooth surfaces. Even if a technician wipes a side surface of tooth 910, the roughened surface will “stand out” compared to non-roughened portions of tooth 910.
The polished or reflective surface wear indicating line 922 can also provide good contrast between the line 922 and nearby portions of the tooth 912 or gear 900. As most gears will have a coating of lubricant (e.g., oil), the polished or reflective surface will tend to retain less lubricant than the surrounding side surfaces of tooth 912. The polished and/or reflective surface of line 922 will “stand out” compared to “rougher” portions of tooth 912. The wear indicating line 922 could also be formed of a fluorescent or phosphorescent ink/material. This could help “illuminate” the line under low light conditions or with the use of specific lighting sources (e.g., a Wood's lamp or black light).
The magnetic surface wear indicating line 924 can facilitate differentiating between the line 924 and nearby portions of the tooth 914 or gear 900. The magnetic surface can be easily located with a magnetic probe. The magnetic surface may also retain small particles that will contrast with the non-magnetic surrounding side surfaces of tooth 914.
The wear indicating line can be placed on one or both sides of the gears and or teeth, and each side can have one or more wear indicating lines. Typically, at least one side of the gear will have at least one wear indicating line. The wear indicating line can be spaced inward from the wearable surfaces of the gear by a predetermined amount that indicates undesirable wear on the gear and/or tooth surface. The wear indicating line can also be formed of a combination of a recessed groove, a raised rib, a roughened surface, a polished surface, a reflective surface, fluorescent material, phosphorescent material and/or a magnetic material, or any combinations thereof. As one example only, the wear indicating line could be formed of a grooved portion, a raised rib portion, a roughened surface portion and a magnetic material portion.
The wear indicating lines can also be used with optical devices and processing systems that image the gears or portions thereof, and then calculate the amount of wear or estimate the remaining amount of gear life. The contrasting surfaces of the wear indicating lines facilitate manual or electronic identification and location of the wear indicating lines, and subsequent evaluation of wear experienced by the gears and/or gear teeth.
One preferred generator type that can be used with the wind turbine of the present invention is a PM synchronous generator, but induction generators, wound-field synchronous generators, or doubly-fed asynchronous generators could be used as well. A wind turbine employing a single generator has been described, but it is to be understood that multiple generators could also be used with modifications to the gearbox. In addition, it is to be understood that the wear indicating line(s) of the present invention could be used in any application where an indication of gear wear is desired.
This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.
