Method for obtaining improved segmented blade

Abstract

The invention relates to a method for obtaining an improved segmented blade, in which, for a 95 m long blade, the connection of which is located at a distance of 25 m to 30 m from the blade tip: a) the chord length and the overall thickness of the outer module (3) in 20 m are reduced by 75%; b) the outer module (3) extends by 1 m; c) for each blade shroud, the number of connecting elements (5) is reduced from 10 to 8 and the mass of the blade is reduced from 800 kg to 640 kg, thereby reducing the influence of the mass of the connections on the remainder of the wind turbine; d) the load on the blade root is reduced by 11% without affecting the performance of the wind turbine. Standard blades and elongated blades are made using the same mold, according to the desired design, by adding removable inserts at the ends of the mold.

Description

Technical Field

[0001] The present invention is in the field of segmented wind turbine blades and more particularly relates to developing a flexible and efficient method for blade design that allows multiple sets of segmented blades to be optimized and brought to market with minimal time and cost. Background Art

[0002] Given the evolving requirements for new generations of machines and their components, manufacturers in the wind energy sector need to continually adapt to the growth of blade sets. It is crucial to facilitate the transition to longer transportable blades, maintain competitive costs and limit investments in production resources as much as possible.

[0003] To this end, a methodology is being developed that allows the development and manufacturing processes of modular blades to be as standardized as possible and, to a large extent, enables the use of already available production lines with minimal impact on the initial models.

[0004] There are some solutions for blades with interchangeable tips. Thus, patent WO2009135902 describes how to change the tip of a blade by adjusting the blade load size in case of a longer tip, and patent US200702553824 describes how to replace the tip and then inject it into the beam.

[0005] On the other hand, there is a design possibility of changing the aerodynamic profile of the blade. RISO and TUF filed patents WO01 / 14740 and EP 2275671, modifying the lift by changing the blade profile, and submitted analytical design methods with blade profiles drawn.

[0006] The proposed solution differs from the prior art because it is specifically defined for mass optimization and AEP (Annual Energy Production) of modular blades, which will be essential in the future for logistical reasons. To this end, the chord length is reduced, which indirectly reduces the loads and the AEP. To recover the lost AEP, the length of the blade is extended at its end. The invention is based on the application of these design techniques, taking into account the required geometrical constraints, in order to optimize the use of the same production means for the entire blade set and adapting existing molds with minimal changes to the production line. Summary of the invention

[0007] One of the effects of blade modularization is the increase in loads, which may be caused by the additional weight implied by the modular union. It is therefore logical to reduce the mass and cost of the modular union as much as possible without compromising the AEP. To this end, the invention envisages different measures along the blade.

[0008] In the region where the connection is formed, the cross section must be as thick as possible in order to have a reaction arm with which the specific load is temporarily reduced at a given cross section.

[0009] In the blade tip area, the chord length and thickness of the blade are reduced in order to reduce the load on the connecting section. The disadvantage of this "thinning" is a certain loss of AEP. In order to recover the lost AEP, the length of the blade is lengthened at the tip.

[0010] One object of the present invention is to reduce the tip chord length of the blade, which reduces loads and power generation compared to a nominal blade configuration.

[0011] Another object of the present invention is to lengthen the outer modules so as to recover the power generation without significantly affecting the load, so as to compensate for the disadvantage of the previous point.

[0012] Another object of the invention is to adapt existing moulds to manufacture these new blades.

[0013] The advantages are as follows:

[0014] This concept can be adopted in non-modular blade designs, but not as effectively as in modular blades, because lengthening the blade would severely affect the logistics costs, which does not happen in modular blades because the outer modules (which are the ones being lengthened) do not have L greater than 30m. 外侧 .

[0015] The core of the present invention lies in a method that allows an ideal combination of these technologies to obtain an optimal modular blade. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Below is given a brief description of a series of drawings which facilitate a better understanding of the invention and which relate expressly to an embodiment of said invention presented as a non-limiting example of the invention.

[0017] Figure 1 A modular blade having two modules is shown.

[0018] Figure 2 It is shown how the moment loads (size factors) in the connection section respond to the overall base load in the different elements that make up the connection.

[0019] Figure 3 Shown are the chord length and thickness distribution of a reference blade (standard version) and a final modification that may be applied to this blade (slim version).

[0020] Figure 4 A reference blade is shown in plan (chord length) and elevation (thickness).

[0021] Figure 5Shown are the plan views (chord length) of a reference blade (standard), a chord reduction modification (slim) and a length extension modification (slim+extended) and details of the areas comprising these modifications.

[0022] Figure 6 Shown are elevation views (thickness) of a reference blade (standard), a chord reduction modification (slim) and a lengthening modification (slim+lengthened), as well as details of the areas incorporating these modifications.

[0023] Figure 7 The influence of thinning effect on load and AEP according to the thinning starting position is shown.

[0024] Figure 8 The effect on loads and AEP of selecting a thinner blade configuration due to increased blade length is shown.

[0025] Fig. 9 The moulds used and different outer module combinations are shown. DETAILED DESCRIPTION

[0026] like Figure 1 As shown, the modular blade has a connection point 1 and consists of two modules: an inner module 2, which is located between the blade root and the connection and has a length L 内侧 Outer module 3, which is located between the connection portion and the blade tip and has a length L 外侧 Add the two lengths mentioned above to get the total length of the blade L 叶片 .

[0027] like Figure 2 As shown, whatever the connection concept, its quality and cost depend on the loads on the section 4 and its geometry. In particular, the unit load in the connection element 5 depends on the load to be carried in said section 4 and its geometry. Thus, thick blades respond to loads or moments with a lower unit load due to the larger reaction arm, while thin blades respond to loads or moments with a higher unit load due to the smaller reaction arm. The final quality and cost of the connection essentially depends on the unit load on the connection element 5. Therefore, it is crucial to reduce the unit load on the connection element 5 as much as possible.

[0028] Since the connection part 1 is a metal connection part, for L 叶片 = 95m modular blades with a connection 25m-30m from the blade tip, which means an increase of about 8%-10% in the load on the blade root, which means a redesign of the wind turbine components (including the inner module 2 of the blade).

[0029] In order to alleviate this overloading, an elongated or "tapered" portion of the outer module 3 of the blade is formed, thereby reducing the chord length / thickness of the geometry, e.g. Figure 3 and Figure 4 shown.

[0030] exist Figure 3 In FIG. 1 , for a standard 95 m blade and an elongated configuration constructed from said blade, chord length distribution 6A for the standard version and chord length distribution 7A for the elongated version as well as thickness distribution 6B for the standard version and thickness distribution 7B for the elongated version can be seen, where:

[0031] a) For the last 20m from the blade tip, the chord length is reduced by 75%;

[0032] b) an additional 15 m transition zone is defined to accommodate the original chord length of the standard blade;

[0033] c) The distribution of relative thicknesses is maintained, which results in the same reduction in overall thickness as the chord length.

[0034] This slender portion has two effects:

[0035] a) Directly reduce the load at the blade root.

[0036] b) Reducing the loads directly in the area of ​​the connection, which means reducing the connection and thereby reducing its influence on the loads at the blade root.

[0037] This elongated part has a disadvantage, namely the loss of power output (AEP) of the machine. This can be solved by lengthening the length of the outer module 3, such as Figure 5 (chord length) and Figure 6 (thickness), which means that the recovery of power generation comes at the expense of some load improvement.

[0038] This approach, slender part + extension part, allows:

[0039] a) Absorb the load increase caused by modularization;

[0040] b) allows optimization of aerodynamic blade design without limiting blade length;

[0041] c) having blade groups for different positions, the blade groups having:

[0042] i. Same inner module 2

[0043] ii. Different outboard modules 3 to increase AEP or reduce loads depending on location, have the same manufacturing cost as the inboard modules 2, which accounts for 80% of the blade cost, and capital investment is only made for the outboard modules 3 (much lower than the inboard modules).

[0044] d) modularization of wind turbine rotors is possible at the closed design stage without the need to redesign components to absorb the increased loads;

[0045] e) A larger rotor can be achieved for the same wind turbine without redesigning the connection. Other techniques based on the extension of the root connection involve additional weight and therefore additional costs, an order of magnitude greater than those proposed by the present technique, and moreover make it impossible to overcome the extension limitations due to the excessive loads induced.

[0046] For example, Figure 7 and Figure 8 Including L 叶片 The result of applying this process to a blade with a length of 95 m:

[0047] Step 1: Figure 7 Results for the root joint load (RJ) and joint loads (loads in the modular blade joint (MBJ)) based on the selected slenderness position and 75% chord length reduction are included. Also, for each configuration, the associated reduction in Annual Energy Production (AEP) is included.

[0048] Step 2: From Figure 7 Choose one of the configurations shown, in this case a constant slenderness (75% reduction in chord length) starting at 20 m from the blade tip. This configuration is included in Figure 3 , Figure 4 , Figure 5 and Figure 6 Starting from this configuration, an extended study was performed, the results of which are included in Figure 8 As shown in this figure, with the 1m extension, all the lost AEP was recovered, while the root loads in the connection area were reduced by 11.5% and 6%.

[0049] This 6% reduction in the connection area allows the number of joint elements 5 to be reduced from 10 to 8 per blade cap, with a reduction in mass from 800 kg to 640 kg, with an associated reduction in cost. This reduction in elements is greater than the reduction in loads, since the elements removed are the least efficient and will hardly increase the incremental load of the connection more than the 6% reduction.

[0050] like Fig. 9 As shown, the common mould for the standard blade version and the slim blade version is longer. The outer mould has inserts for making the standard modular blade and the slim modular blade.

[0051] The mould must be a shell for both types of blades: standard blades and slender blades. The same mould is used for both types of blades. The mould for the standard blade has no changes, except that the last 2m have more reinforcing elements (strings). That is why on the CC' section the removable insert is in the standard version.

[0052] The slim version is longer and thinner, with removable inserts placed in sections AA' and BB'.

Claims

1. A method for obtaining an improved segmented blade, the method being based on blade geometry / blade length L 叶片 , the position of the connection part (1) and the number of elements (5) used in the connection part, characterized in that The method follows these steps: a) reduce the chord length and overall thickness in the outer module (3) by 75%, b) Extend the span of the outer module (3) to restore 3.5% AEP, c) Due to the effect of reducing loads without affecting the performance of the wind turbine, The number of connecting elements (5) is reduced by 6%, and therefore the weight is also reduced by 6%.

2. The method for obtaining an improved segmented blade according to claim 1, wherein: In addition to reducing the chord length and the overall thickness, as well as extending the span of the outer module (3) and reducing the number of connecting elements, a common mold with removable inserts is used, which are arranged in different sections of the outer module (3).

3. The method for obtaining an improved segmented blade according to claim 1, wherein: For a 95 m long blade with the connection located at a distance of 25 m - 30 m from the blade tip, a 75% reduction in chord length and total thickness is performed in the 20 m of the outer module (3).

4. The method for obtaining an improved segmented blade according to claim 1, wherein: For a 95m long blade, the outer modules (3) extend by 1m.

5. The method for obtaining an improved segmented blade according to claim 1, wherein: For a 95 m long blade, the number of connection elements (5) is reduced from 10 to 8 and the mass of the blade is reduced from 800 kg to 640 kg, thereby reducing the impact of the mass of the connection on the rest of the wind turbine.

6. The method for obtaining an improved segmented blade according to claim 1, wherein: Without affecting the performance of the wind turbine, the load on the blade root is reduced by 11% for a 95 m long blade.

7. The method for obtaining an improved segmented blade according to claim 2, wherein: The same mould is used to manufacture standard blades and elongated blades, adding removable inserts in the outer module (3) in sections AA' and BB' for the elongated blades and in section CC' for the standard blades.

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