WO2024243414A1

WO2024243414A1 - Wind turbine with a rotor hub gap

Info

Publication number: WO2024243414A1
Application number: PCT/US2024/030785
Authority: WO
Inventors: Nojan BAGHERI-SADEGHI; Gitvik MAMORIA; Brian T. HELENBROOK; Kenneth D. Visser
Original assignee: Clarkson University
Priority date: 2023-05-23
Filing date: 2024-05-23
Publication date: 2024-11-28

Abstract

A structure and method to improve the performance of fixed pitch wind turbines by reducing the impact of the central hub. The rotor includes a gap of specified geometry between the root of the rotor blade and the central hub in such a manner as to provide for the ambient air to accelerate though the gap, thereby resulting in an increased amount of air being allowed to impinge on the hub surface which reduces the impact of the hub's presence on the flow field.

Description

WIND TURBINE WITH A ROTOR HUB GAP

Government Funding

[0001] N/A

Cross-Reference to Related Application

[0002] The present application relates and claims priority to United States Provisional Patent Application No. 63/468374, filed May 23, 2023, the entirety of which is hereby incorporated by reference.

Field of the Invention

[0003] The present disclosure is directed generally to wind turbines and more particularly to the manner in which a blade connects to a rotor hub.

Background

[0004] Wind power is presently one of the world's fastest growing renewable energy resource technologies. The need to improve the extraction efficiency of power from the wind is increasingly desirable for both commercial and residential applications. Notably, most residential sized wind turbines are approximately half as efficient as the accepted theoretical maximum, indicating a potential to decrease lifetime system costs by increasing the turbine efficiency.

[0005] Traditional fixed-pitch wind turbine designs incorporate a hub and a set of blades which, when combined, are referred to as the rotor. The blades are joined to the hub with either a simple fixed mechanical attachment, resulting in a fixed pitch configuration, or to a mechanism enabling rotation of the blade along the longitudinal axis termed a variable pitch configuration. In the fixed pitch case, the blade intersects the hub in such a manner as to provide a continuous airfoil surface to the hub, as shown in FIGS. 1 and 3.

[0006] Accordingly, there is a need in the art for renewable, sustainable and green energy sources with improved energy extraction efficiency. Summary

[0007] The present disclosure is directed to a rotor for a wind turbine having a gap formed between the hub and the lifting surface of the blade.

[0008] According to an aspect, a rotor for use in a wind turbine, comprises a blade having a lifting surface and a non-lifting structural member, and a hub to which the non-lifting member of the blade is attached with a gap being formed between the hub and the lifting surface of the blade. [0009] According to an embodiment, the wind turbine can be one of ducted or open rotor.

[0010] According to an aspect, a method for affecting performance of a fixed pitch wind turbine, comprising the steps of providing a rotor with a blade having a lifting surface and nonlifting surface, and a hub connected to the non-lifting surface, and providing a gap between the hub and the lifting surface, whereby ambient air will accelerate though the gap resulting in an increased amount of air being allowed to impinge on the hub surface reducing the impact of the hub’s presence on the flow field.

[0011] These and other aspects of the invention will be apparent from the embodiments described below.

Brief Description of the Drawings

[0012] The present invention will be more fully understood and appreciated by reading the following Detailed Description in conjunction with the accompanying drawings, in which: [0013] FIG. l is a cross sectional view of a typical fixed pitch wind turbine rotor.

[0014] FIG. 2 is a cross sectional view of a wind turbine rotor, in accordance with an embodiment.

[0015] FIG. 3 is a forward-facing view of the typical wind turbine of FIG. 1.

[0016] FIG. 4 is a forward-facing view of a wind turbine rotor reflecting the rotor geometry of

FIG. 2, in accordance with an embodiment.

[0017] FIG. 5 is a graphical representation of the flowfield solution for the typical wind turbine of FIG. 1 showing the large wake that is created behind the hub where the flow recirculates.

[0018] FIG. 6 is a graphical representation of the flowfield solution for a hub gapped wind turbine, where the recirculation zone has been eliminated, in accordance with an embodiment.

[0019] FIG. 7 is a graphical representation of a flowfield solution for a typical ducted wind turbine showing the large wake that is created behind the hub where the flow recirculates. [0020] FIG. 8 is a graphical representation of a flowfield solution for a hub gapped ducted wind turbine reflecting the rotor geometry of FIG. 2, where the recirculation zone has been eliminated, in accordance with an embodiment.

[0021] FIG. 9 is a table of results for both ducted and open rotor wind turbines and their coefficient of performance with and without the rotor gap.

Detailed Description of Embodiments

[0022] The present disclosure describes a wind turbine with a rotor hub gap.

[0023] Referring to FIG. 2, in one embodiment, is a wind energy extractor comprising a set of blades 1 attached to a central hub 2 containing the electrical conversion equipment and with a gap 10 between the rotor and hub 2. In one embodiment, the gap is about the thickness of the flow boundary layer. A front view of this configuration is shown in FIG. 4, where the same numbering is used. In this case, non-lifting structural members 5 are shown whose purpose is to support the rotor blades while allowing an accelerated flow to be forced between the inner edge of the blade and the hub. In typical turbines, the gap does not exist as is shown in FIG. 1 and FIG. 3.

[0024] FIG. 5 graphically shows the streamlines and velocity magnitude contours of a typical turbine. The hub separates off of the hub creating a large recirculation zone behind the hub 2. This reflects the geometry and view of FIG. 1.

[0025] FIG. 6 shows that this recirculation zone is eliminated by providing the small gap 10 between the inner tip of the lifting surface of the rotor blade 1 and the hub 2. The flow that passes through the gap serves to reduce the flow separation and keep more flow attached to the hub 2.

[0026] FIG. 7 graphically shows the streamlines and velocity magnitude contours of a typical ducted turbine. The hub separates off of the hub creating a large recirculation zone behind the hub. This reflects the rotor geometry and view of FIG. 1 with a surrounding duct.

[0027] FIG. 8 shows that in the ducted case this recirculation zone is again eliminated by providing the small gap 10 between the inner tip of the lifting surface of the rotor blade and the hub. The flow that passes through the gap serves to reduce the flow separation and keep more flow attached to the hub.

[0028] FIG. 9 shows power coefficients for rotors without and with a gap. Two configurations were studied, an open rotor (WT) and a ducted wind turbine (DWT), each without and with a gap. The power coefficients C_P are the power normalized by the pu³A/2 where p is the air density, u is the wind speed, and A is the cross-sectional area of the device A = TT ² , where R is the outer radius of the rotor. C_{P totai} is similar for a ducted turbine but the area is based on the outer radius of the duct. The results show that for open rotors, although there is a significant improvement in the flow field, the effect on the power is not significant, whereas for a ducted turbine there is a significant increase in power by adding the gap 10.

[0029] While various embodiments have been described and illustrated herein, those of ordinary skill in the art will readily envision a variety of other means and/or structures for performing the function and/or obtaining the results and/or one or more of the advantages described herein, and each of such variations and/or modifications is deemed to be within the scope of the embodiments described herein. More generally, those skilled in the art will readily appreciate that all parameters, dimensions, materials, and configurations described herein are meant to be exemplary and that the actual parameters, dimensions, materials, and/or configurations will depend upon the specific application or applications for which the teachings is/are used. Those skilled in the art will recognize or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments described herein. It is, therefore, to be understood that the foregoing embodiments are presented by way of example only and that, within the scope of the appended claims and equivalents thereto, embodiments may be practiced otherwise than as specifically described and claimed. Embodiments of the present disclosure are directed to each individual feature, system, article, material, kit, and/or method described herein. In addition, any combination of two or more such features, systems, articles, materials, kits, and/or methods, if such features, systems, articles, materials, kits, and/or methods are not mutually inconsistent, is included within the scope of the present disclosure.

Claims

Claims What is claimed is:

1. A rotor for use in a wind turbine, comprising: a. a blade having a lifting surface and a non-lifting structural member; and b. a hub to which the non-lifting member of the blade is attached with a gap being formed between the hub and the lifting surface of the blade.

2. The rotor of claim 1, wherein the wind turbine can be one of ducted or open rotor.

3. A method for affecting performance of a fixed pitch wind turbine, comprising the steps of: a. providing a rotor with a blade having a lifting surface and non-lifting surface, and a hub connected to the non-lifting surface; b. providing a gap between the hub and the lifting surface, whereby ambient air will accelerate though the gap resulting in an increased amount of air being allowed to impinge on the hub surface reducing the impact of the hub’s presence on the flow field.