The present disclosure relates in general to wind turbine rotor blades, and more particularly to improved airfoil configurations for wind turbine rotor blades.
Wind power is considered one of the cleanest, most environmentally friendly energy sources presently available, and wind turbines have gained increased attention in this regard. A modern wind turbine typically includes a tower, a generator, a gearbox, a nacelle, and a rotor having a rotatable hub with one or more rotor blades. The rotor blades capture kinetic energy of wind using known airfoil principles. The rotor blades transmit the kinetic energy in the form of rotational energy so as to turn a shaft coupling the rotor blades to a gearbox, or if a gearbox is not used, directly to the generator. The generator then converts the mechanical energy to electrical energy that may be deployed to a utility grid.
Each rotor blade extends from the hub at a blade root of the rotor blade and continues to a blade tip. A cross-section of the rotor blade is defined as an airfoil. The shape of an airfoil may be defined in relationship to a chord line. The chord line is a measure or line connecting the leading edge of the airfoil with the trailing edge of the airfoil. The shape may be defined in the form of X and Y coordinates from the chord line. The X and Y coordinates generally are dimensionless. Likewise, the thickness of an airfoil refers to the distance between the upper surface and the lower surface of the airfoil and is expressed as a fraction of the chord length.
The inboard region, i.e., the area closest to the hub, generally requires the use of relatively thick airfoils (30%≤t/c≤100% or at least 70% t/c). The aerodynamic performance of conventional airfoil designs, however, degrades rapidly for thicknesses greater than 30% of chord largely due to flow separation concerns. For certain increased chord thicknesses (e.g. above 70% of chord), massive flow separation may be unavoidable such that the region of the rotor blade may be aerodynamically compromised.
In some instances, flatback airfoils may be used in the inboard region to allow for higher lift of thick airfoils but at reduced chords. Traditional flatback designs, however, can be complicated to manufacture. Though roundback airfoils are substantially less complicated to manufacture than flatback airfoils and allow the airflow to “feel” a larger trailing edge thickness, such airfoils can create flow separation on the curved surface that is sensitive to small details in the inflow. As such, the separation location and hence the lift from the roundback airfoil can fluctuate to an unacceptable extent.
Thus, there is a need for new and improved airfoil configurations for wind turbine rotor blades that addresses the aforementioned issues. More specifically, an airfoil that provides improved aerodynamic performance particularly with respect to the inboard region would be advantageous.
Aspects and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the invention.
In one aspect, the present disclosure is directed to a rotor blade assembly for a wind turbine. The rotor blade assembly includes a rotor blade having exterior surfaces defining a pressure side, a suction side, a leading edge, and a trailing edge each extending in a generally span-wise direction between an inboard region and an outboard region. The inboard region is typically characterized by a rounded trailing edge. Further, the rotor blade assembly further includes at least one airflow separation element mounted to either or both of the pressure or suction sides of the rotor blade within the inboard region and adjacent to the rounded trailing edge. In addition, an edge of the at least one airflow separation element is configured to provide a fixed airflow separation location in the inboard region during standard operation. The rotor blade assembly also includes at least one airflow modifying element configured with the trailing edge of the rotor blade.
In one embodiment, the rotor blade assembly may include one or more airflow separation elements mounted to the suction side of the rotor blade and one or more airflow modifying elements mounted to the pressure side of the rotor blade. In alternative embodiments, the rotor blade assembly may include opposing airflow separation elements, with at least one airflow separation element mounted on the pressure side and another airflow separation element mounted on the suction side of the rotor blade.
In another embodiment, the airflow modifying element(s) may include a splitter plate. In such embodiments, the splitter plate(s) may be mounted between the opposing airflow separation elements at the trailing edge. More specifically, in certain embodiments, the splitter plate(s) may be secured between the pressure and suction sides of the rotor blade at the trailing edge.
In further embodiments, the airflow separation element(s) may include one or more airflow separation anchors, one or more airflow separation plates, a non-structural fairing, or any other suitable airflow separation elements. In additional embodiments, the one or more airflow separation anchors may have a proximal end and a distal end, with both the proximal and distal ends being fixed to at least one of the pressure side or the suction side of the rotor blade. In such embodiments, the rounded trailing edge of the rotor blade may extend beyond the airflow separation anchors in a generally chord-wise direction.
In additional embodiments, the rotor blade assembly may include a plurality of airflow separation elements or a plurality of airflow modifying elements. In such embodiments, the airflow separation elements and/or the airflow modifying elements may be grouped into a plurality of groups with each group having a different, constant cross-section.
In further embodiments, the airflow separation element(s) and/or the airflow modifying element(s) may have a uniform wall thickness. In such embodiments, a filler material may be arranged in the hollow space of the airflow separation element(s) and/or the airflow modifying element(s).
In another aspect, the present disclosure is directed to a method for improving aerodynamic efficiency of a rotor blade at an inboard region thereof. The method includes forming at least one airflow separation element and at least one airflow modifying element via an extrusion process such that the airflow separation element(s) and the airflow modifying element(s) have a constant cross-section. The method also includes securing the at least one airflow separation element to at least one of a pressure side or a suction side of the rotor blade within the inboard region adjacent to a trailing edge of the rotor blade. As such, an edge of the at least one airflow separation element is configured to provide a fixed airflow separation location in the inboard region during standard operation. Further, the method includes securing the at least one airflow modifying element at the trailing edge of the rotor blade.
In one embodiment, the method may further include segmenting the at least one airflow separation element into a plurality of airflow separation elements. In another embodiment, the method may include segmenting the at least one airflow modifying element into a plurality of airflow modifying elements.
In further embodiments, the method may include mounting the airflow separation element(s) to the suction side of the rotor blade and mounting the airflow modifying element(s) to the pressure side of the rotor blade at the trailing edge.
In alternative embodiments, the method may include mounting opposing airflow separation elements to the pressure and suction sides of the rotor blade, respectively. In such embodiments, the airflow modifying element(s) may include a splitter plate. As such, the method may further include mounting the splitter plate between the opposing airflow separation elements at the trailing edge.
In additional embodiments, the step of securing the airflow separation element(s) to at least one of the pressure side or the suction side of the rotor blade may include attaching the airflow separation element(s) to at least one of the pressure side or the suction side via at least one of double-sided tape, a bond paste, or combinations thereof. In similar embodiments, the step of securing the airflow modifying element(s) at the trailing edge of the rotor blade may include attaching the airflow modifying element(s) at the trailing edge via at least one of double-sided tape, a bond paste, or combinations thereof.
In several embodiments, the method may also include forming the airflow separation element(s) and/or the airflow modifying element(s) from at least one of a thermoset material or a thermoplastic material.
In yet another aspect, the present disclosure is directed to an airflow separation kit for an inboard region of a rotor blade in a wind turbine. The airflow separation kit includes a plurality of airflow separation elements. Each of the airflow separation elements includes a proximal end and a distal end, with the proximal and distal ends configured to mount to at least one of the pressure side or the suction side of the rotor blade within an inboard region of the rotor blade adjacent to a rounded trailing edge thereof. Further, each of the airflow separation elements is configured to provide a fixed airflow separation location in the inboard region during standard operation. The airflow separation kit further includes at least one airflow modifying element for mounting at the rounded trailing edge of the rotor blade. Further, each of the airflow separation elements and the airflow modifying element(s) has a constant cross-section. It should be appreciated that the airflow separation kit may further include any of the features as described herein.
These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.
A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended figures, in which:
Reference now will be made in detail to embodiments of the invention, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For instance, features illustrated or described as part of one embodiment can be used with another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents.
Generally, the present disclosure is directed to a rotor blade assembly for a wind turbine having an improved airfoil configuration. More specifically, the rotor blade assembly includes unique combinations of airflow separation elements (such as flow anchors, etc.) and airflow modifying elements (such as pressure side attachments, splitter plates, etc.) mounted an inboard region of the rotor blade as well as manufacturing and/or attachments methods for such combinations. Providing such elements in the root transition area of the rotor blade alters the airflow to increase the effective chord length in areas of the rotor blade that are less efficient due to the transition to the substantially circular blade root. As such, the unique combinations provided herein are configured to improve aerodynamic efficiency.
The combination of elements of the present disclosure provide many advantages not present in the prior art. For example, the combination of the airflow separation elements and the airflow modifying elements enhances the lift of the rotor blade and reduces drag of the blade root (from near the maximum chord inboard). The increase in lift and the decrease in drag increases the axial induction, thereby improving the annual energy production of the wind turbine. In addition, the combination of elements of the present disclosure significantly reduces the manufacturing difficulty and cost associated with traditional flatback airfoils.
Referring now to the drawings,
Thus, the present disclosure is directed to an improved rotor blade assembly that acts as a flatback airfoil without the associated manufacturing issues. More specifically, as generally illustrated in
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One or more structural components may also be included within the rotor blade 22 to provide structural support to the rotor blade 22. For example,
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The airflow separation element(s) 102 may include any suitable elements configured to separate airflow from a surface of the blade 22. For example, in certain embodiments, the airflow separation element(s) 102 may include one or more airflow separation anchors 104, one or more airflow separation plates, a non-structural fairing, or any other suitable airflow separation elements. For example, as shown in
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In alternative embodiments, as shown in
In additional embodiments, the airflow separation element(s) 102 may be secured to either or both of the pressure or suction sides 24, 23 of the rotor blade 22 via at least one of double-sided tape, a bond paste, or combinations thereof. Similarly, the airflow modifying element(s) 106 may be secured at the trailing edge 28 of the rotor blade 22 via at least one of double-sided tape, a bond paste, or combinations thereof. In further embodiments, where the elements 102, 106 are segmented, in-line double sided foam tape may be cut into multiple strips to allow for structural adhesive to be used between segments during installation.
Each airflow separation element(s) 102 and/or airflow modifying element(s) 106 according to the present disclosure may be formed from any suitable materials. For example, the material utilized to form the element(s) 102, 106 may preferably be lightweight, and may further preferably be suitably rigid to maintain its structure during use in a wind turbine 10. More specifically, in several embodiments, element(s) 102, 106 may be formed from a thermoset material, a thermoplastic material, metal, or combinations thereof, and may also be optionally reinforced with any suitable material, such as fiber material.
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 include 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.