An equivalent calculation method for wind turbine blade surface loads characterizing fluid-structure coupling effects

Abstract

The present invention belongs to the technical field of wind turbine blade load calculation, and proposes an equivalent calculation method for wind turbine blade surface load that characterizes fluid-solid coupling effect. The main scheme is: first, establish a wind turbine blade aerodynamic load simulation calculation model in computational fluid dynamics simulation software to solve the unidirectional force of incoming wind on the blade surface; second, derive the interaction relationship between blade deformation and incoming wind force, and obtain the calculation expression of the incoming wind force on the blade surface under the bidirectional fluid-solid coupling effect; then, derive the equivalent relationship of the blade surface pressure coefficient that characterizes the bidirectional fluid-solid coupling effect, introduce the coupling coefficient, and obtain the equivalent calculation expression of the pressure coefficient; finally, use the equivalent calculation expression to solve the wind turbine blade surface pressure under the bidirectional fluid-solid coupling effect. The present invention can solve the current problems of difficulty in converging the bidirectional fluid-solid coupling aerodynamic performance simulation of wind turbine blades and high cost of numerical calculation.

Description

Technical Field

[0001] The present invention relates to the technical field of wind turbine blade load calculation, and in particular to a wind turbine blade surface load equivalent calculation method for characterizing fluid-solid coupling effect. Background Art

[0002] In the structural optimization design of wind turbine blades, accurate calculation of the loads on the blades is an important step to ensure good aerodynamic performance and structural safety. However, traditional load calculation methods often ignore the fluid-structure coupling effect of the blades, resulting in a large deviation between the calculation results and the actual operating conditions. Blade load simulation calculations involving fluid-structure coupling usually face the problems of high computing hardware requirements, high convergence difficulty, and low computing efficiency. Therefore, under the premise of ensuring the accuracy of the calculation, how to reflect the fluid-structure coupling effect of wind turbine blades, improve the computing efficiency, and save computing costs is a key issue that needs to be solved in the calculation of wind turbine blade surface loads. Summary of the invention

[0003] The purpose of the present invention is to provide a method for calculating the equivalent surface load of a wind turbine blade for characterizing the fluid-solid coupling effect, aiming to solve the current problems of great difficulty in converging the aerodynamic performance of bidirectional fluid-solid coupling simulation of wind turbine blades and high numerical calculation cost.

[0004] The present invention solves the technical problem and adopts the following technical solution:

[0005] A wind turbine blade surface load equivalent calculation method for characterizing fluid-solid coupling effect comprises the following steps:

[0006] A simulation model for aerodynamic loads on wind turbine blades is established in computational fluid dynamics simulation software to solve the unidirectional force of incoming wind on the blade surface;

[0007] The interaction relationship between blade deformation and incoming wind force is derived, and the calculation expression of the incoming wind force on the blade surface under the bidirectional fluid-solid coupling effect is obtained;

[0008] The equivalent relationship of blade surface pressure coefficient that characterizes the bidirectional fluid-solid coupling effect is derived, and the coupling coefficient is introduced to obtain the equivalent calculation expression of the pressure coefficient.

[0009] The equivalent calculation expression is used to solve the surface pressure of wind turbine blades under the bidirectional fluid-structure coupling effect.

[0010] As a further optimization, the computational fluid dynamics simulation software is STARCCM+, which solves the unidirectional force F of the incoming wind on the blade surface based on the basic principles of fluid mechanics, expressed as: F = C p ρv 2 A / 2, where C pis the surface pressure coefficient of the blade under the unidirectional action of the incoming wind, ρ is the fluid density, v is the flow velocity, and A is the force area of ​​the blade.

[0011] As a further optimization, the interaction relationship between blade deformation and incoming wind force is derived to obtain a calculation expression for the incoming wind force on the blade surface under the bidirectional fluid-solid coupling effect, including the following steps:

[0012] According to Hooke's law, the deformation δ of a certain position on the blade at a distance of L from the blade root under the action of the incoming wind is calculated. The expression is: δ = FL / EA, where E is the elastic modulus of the blade, A is the force area of ​​the blade, and L is the length of a certain position on the blade from the blade root;

[0013] The relationship between the deformation δ at a certain position on the blade at a distance L from the blade root and the incoming wind force F is derived as follows:

[0014]

[0015] Introducing the coefficient m representing the influence of blade deformation on the flow field of the incoming wind, the force F' exerted by the incoming wind on the blade surface under the bidirectional fluid-solid coupling effect is expressed as: F' = F + mδ;

[0016] The calculation expression for calculating the force F' exerted by the downflow on the blade surface under the bidirectional fluid-solid coupling effect is: Among them, C p ′ is the pressure coefficient of the blade under the bidirectional fluid-solid coupling effect.

[0017] As a further optimization, the expression for the influence coefficient m of blade deformation on the incoming wind flow field is:

[0018]

[0019] Among them, D FSI The value is the blade deformation obtained in the bidirectional fluid-structure coupling simulation, D BEM The value of is the deformation obtained by FEM simulation after the blade is loaded with aerodynamic loads calculated based on BEM theory.

[0020] As a further optimization, the derivation of the equivalent relationship of the blade surface pressure coefficient characterizing the bidirectional fluid-solid coupling effect, the introduction of the coupling coefficient, and the acquisition of the equivalent calculation expression of the pressure coefficient include the following steps:

[0021] The relationship between the unidirectional force of the incoming wind on the blade surface and the force on the blade surface under the bidirectional fluid-solid coupling effect is derived as follows:

[0022] The relationship between the pressure coefficient of the blade surface under the unidirectional action of the incoming wind and the bidirectional fluid-solid coupling effect is derived as follows:

[0023] The blade surface pressure coefficient C calculated by the established wind turbine blade aerodynamic load simulation model p The pressure coefficient C of the incoming wind on the blade surface under the bidirectional fluid-solid coupling effect p ′ introduces the coupling coefficient λ, and the coupling coefficient expression is:

[0024]

[0025] Establish an equivalent relationship and obtain the equivalent calculation expression C of the pressure coefficient p ′=λC p , in order to calculate the blade surface pressure coefficient considering the fluid-solid coupling effect.

[0026] As a further optimization, the equivalent calculation expression is used to solve the surface pressure of the wind turbine blade under the bidirectional fluid-solid coupling effect, which is expressed as:

[0027] The beneficial effect of the present invention is: through the above-mentioned equivalent calculation method for the surface load of a wind turbine blade that characterizes the fluid-solid coupling effect, by introducing a coupling coefficient, the surface pressure coefficient of the wind turbine blade calculated based on fluid mechanics is corrected to equivalently characterize the fluid-solid coupling effect, thereby quickly estimating the blade surface pressure load considering the bidirectional fluid-solid coupling effect under extreme wind conditions, and providing an accurate load basis for the structural optimization design of wind turbine blades. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a flow chart of a method for equivalent calculation of wind turbine blade surface loads characterizing fluid-solid coupling effect in an embodiment of the present invention;

[0029] Figure 2 This is a CFD-based wind turbine blade surface aerodynamic load simulation model diagram in an embodiment of the present invention;

[0030] Figure 3 is a value curve of the influence coefficient m of the blade r / R position deformation on the incoming wind flow field under extreme wind conditions in an embodiment of the present invention;

[0031] Figure 4 is a comparison diagram of surface pressure coefficients at a typical position of r / R=0.7 calculated by three methods: CFD simulation, equivalent method, and bidirectional fluid-solid coupling simulation in an embodiment of the present invention;

[0032] Figure 5 It is a comparison chart of the calculation time of wind turbine blade output power using an equivalent method and a direct solution based on bidirectional fluid-solid coupling simulation in an embodiment of the present invention. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0034] Example

[0035] This embodiment provides a method for calculating the equivalent surface load of a wind turbine blade to characterize the fluid-solid coupling effect. Figure 1 , wherein the method comprises the following steps:

[0036] S1. Establish a wind turbine blade aerodynamic load simulation model in computational fluid dynamics simulation software to solve the unidirectional force of the incoming wind on the blade surface;

[0037] S2. The interaction relationship between blade deformation and the force of incoming wind is derived, and the calculation expression of the force of incoming wind on the blade surface due to the bidirectional fluid-solid coupling effect is obtained;

[0038] S3. Derive the equivalent relationship of the blade surface pressure coefficient that characterizes the bidirectional fluid-solid coupling effect, introduce the coupling coefficient, and obtain the equivalent calculation expression of the pressure coefficient;

[0039] S4. Use the equivalent calculation expression to solve the surface pressure of wind turbine blades under the bidirectional fluid-solid coupling effect.

[0040] In step S1 of the above method, a wind turbine blade aerodynamic load simulation model can be established in the computational fluid dynamics (CFD) simulation software SRARCCM+. The simulation model is as follows: Figure 2 As shown, according to the basic principles of fluid mechanics, the unidirectional force F of the incoming wind on the blade surface is solved, which is expressed as: F = C p ρv 2 A / 2, where C p is the surface pressure coefficient of the blade under the unidirectional action of the incoming wind, ρ is the fluid density, v is the flow velocity, and A is the force-bearing area of ​​the blade;

[0041] It should be noted that the derivation of the interaction between blade deformation and incoming wind force (i.e., bidirectional fluid-solid coupling) in step S2 of the above method to obtain the calculation expression of the incoming wind force on the blade surface under the bidirectional fluid-solid coupling effect may include the following steps:

[0042] S201. According to Hooke's law, the deformation δ of a certain position on the blade at a distance L from the blade root under the action of the incoming wind is calculated, and the expression is: δ = FL / EA, where E is the elastic modulus of the blade, A is the force-bearing area of ​​the blade, and L is the length of a certain position on the blade from the blade root;

[0043] S202. Derivation of the relationship between the deformation δ at a certain position on the blade at a distance L from the blade root and the incoming wind force F:

[0044]

[0045] S203, introducing the influence coefficient m of blade deformation on the flow field of the incoming wind, the force F' of the incoming wind on the blade surface under the bidirectional fluid-solid coupling effect is expressed as: F'=F+mδ; Here, the expression for the influence coefficient m of blade deformation on the flow field of the incoming wind is:

[0046] Among them, D FSI The value is the blade deformation obtained in the bidirectional fluid-structure coupling simulation, D BEM The value of is the deformation obtained by FEM simulation after the blade is loaded with aerodynamic loads calculated based on BEM theory;

[0047] S204. Calculate the force F' of the downflow on the blade surface due to the bidirectional fluid-solid coupling effect. The calculation expression is: Among them, C p ′ is the pressure coefficient of the blade under the bidirectional fluid-solid coupling effect.

[0048] It should be noted that the derivation of the equivalent relationship of the blade surface pressure coefficient characterizing the bidirectional fluid-solid coupling effect in step S3 of the above method, introducing the coupling coefficient, and obtaining the equivalent calculation expression of the pressure coefficient may include the following steps:

[0049] S301. The relationship between the unidirectional force of the incoming wind on the blade surface and the force on the blade surface under the bidirectional fluid-solid coupling effect is derived as follows:

[0050] S302. The relationship between the pressure coefficient of the blade surface under the unidirectional action of the incoming wind and the bidirectional fluid-solid coupling effect is derived as follows:

[0051] S303, the blade surface pressure coefficient C calculated by the established wind turbine blade aerodynamic load simulation calculation model p The pressure coefficient C of the incoming wind on the blade surface under the bidirectional fluid-solid coupling effect p ′ introduces the coupling coefficient λ, and the coupling coefficient expression is:

[0052]

[0053] S304. Establish an equivalent relationship and obtain the equivalent calculation expression C of the pressure coefficient p ′=λC p , in order to calculate the blade surface pressure coefficient considering the fluid-solid coupling effect.

[0054] Finally, the equivalent calculation expression used in step S4 of the above method to solve the surface pressure of the wind turbine blade under the bidirectional fluid-solid coupling effect is expressed as:

[0055] It should be noted that the value of the influence coefficient m of the blade deformation on the incoming wind flow field in step S203 is as follows: Figure 3 As shown; among them, D FSI The value is the blade deformation obtained in the bidirectional fluid-structure coupling simulation, D BEM The value of is the deformation obtained by FEM simulation after the blade is loaded with aerodynamic loads calculated based on BEM theory.

[0056] Figure 4 The pressure coefficient C of the blade at the section r / R=0.7 calculated according to the equivalent method in this embodiment is shown. p ′ and C calculated by bidirectional fluid-structure coupling simulation p "Comparison of numerical distribution, and evaluation of the correctness of the method proposed in this embodiment based on relative error.

[0057] Specifically, this embodiment calculates the pressure coefficient at a typical position of the blade where r / R=0.7, and compares and analyzes the blade pressure coefficient calculated by the equivalent method based on CFD and the blade pressure coefficient calculated by the two-way fluid-solid coupling simulation to verify the correctness and effectiveness of the proposed equivalent method.

[0058] Specifically, the blade elastic modulus mainly depends on the homogenized equivalent E x The equivalent modulus parameters of the blade composite material are shown in Table 1. After calculation, in this embodiment, the modulus E=E x =24.22, L=0.7*40.3=28.21, A=1, m=0.276, then λ=1.321;

[0059] Table 1 Equivalent modulus parameters of blade composite materials

[0060]

[0061] In this embodiment, the equivalent method and the bidirectional fluid-solid coupling simulation are used to directly solve the blade output power. After reaching stability, the calculation time of the two is compared, and the efficiency of the equivalent method in solving the blade surface pressure in this embodiment can be qualitatively evaluated.

[0062] Combined with Figure 5 By comparing the calculation time of the wind turbine blade surface pressure directly solved by the equivalent method and the bidirectional fluid-solid coupling simulation, it was found that the calculation time using the equivalent method is 2.83 times the calculation time of the bidirectional fluid-solid coupling simulation, which verifies the high efficiency of the equivalent method.

[0063] Therefore, through the above description of this embodiment, it can be seen that this embodiment has accuracy, efficiency and universality in calculating the surface load of wind turbine blades that characterize the bidirectional fluid-solid coupling effect, and provides important use value for the analysis and calculation of aerodynamic loads on the blade surface. In addition, through this embodiment, it can be seen that the calculation speed of calculating the blade surface pressure using the equivalent method is about 2.8 times that of the direct solution, which verifies the efficiency of the proposed equivalent method.

[0064] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A wind turbine blade surface load equivalent calculation method for characterizing fluid-solid coupling effect, characterized in that: The steps include: A simulation model for aerodynamic loads on wind turbine blades is established in computational fluid dynamics simulation software to solve the unidirectional force of incoming wind on the blade surface; The interaction relationship between blade deformation and incoming wind force is derived, and the calculation expression of the incoming wind force on the blade surface under the bidirectional fluid-solid coupling effect is obtained; The equivalent relationship of blade surface pressure coefficient that characterizes the bidirectional fluid-solid coupling effect is derived, and the coupling coefficient is introduced to obtain the equivalent calculation expression of the pressure coefficient. The equivalent calculation expression is used to solve the surface pressure of wind turbine blades under the bidirectional fluid-solid coupling effect; The derivation of the interaction relationship between blade deformation and incoming wind force to obtain a calculation expression for the incoming wind force on the blade surface under the bidirectional fluid-solid coupling effect includes the following steps: According to Hooke's law, calculate the distance from the blade to the root L A certain position is deformed by the incoming wind , the expression is: , Among them, among them, E is the elastic modulus of the blade, A is the blade force area, L is the distance from a certain position on the leaf to the leaf root; Derivation of the distance from the blade to the root L The deformation at a certain position δ The force of incoming wind F Relationship: ; The coefficient representing the influence of blade deformation on the incoming wind flow field is introduced m , then the force exerted by the downflow on the blade surface due to the bidirectional fluid-structure coupling effect is F' It is expressed as: ; Calculation of the force exerted by downflow on blade surface due to bidirectional fluid-structure interaction F' , its calculation expression is: ,in, is the pressure coefficient of the blade under the bidirectional fluid-solid coupling effect; The coefficient indicating the influence of blade deformation on the incoming wind flow field m The expression is ; in, D FSI The value is the blade deformation obtained in the bidirectional fluid-structure coupling simulation. D BEM The value of is the deformation obtained by FEM simulation after the blade is loaded with aerodynamic loads calculated based on BEM theory; The method of deriving the equivalent relationship of the blade surface pressure coefficient characterizing the bidirectional fluid-solid coupling effect, introducing the coupling coefficient, and obtaining the equivalent calculation expression of the pressure coefficient includes the following steps: The relationship between the unidirectional force of the incoming wind on the blade surface and the force on the blade surface under the bidirectional fluid-solid coupling effect is derived as follows: ; The relationship between the pressure coefficient of the blade surface under the unidirectional action of the incoming wind and the bidirectional fluid-solid coupling effect is derived as follows: ; The blade surface pressure coefficient calculated by the established wind turbine blade aerodynamic load simulation model C p The pressure coefficient of the incoming wind on the blade surface under the bidirectional fluid-structure coupling effect Introducing the coupling coefficient λ , the coupling coefficient expression is: ； Establish an equivalent relationship and obtain the equivalent calculation expression of the pressure coefficient , in order to calculate the blade surface pressure coefficient considering the fluid-solid coupling effect; The equivalent calculation expression is used to solve the surface pressure of the wind turbine blade under the bidirectional fluid-solid coupling effect, which is expressed as: 。 2. The equivalent calculation method for wind turbine blade surface load characterizing fluid-structure coupling effect according to claim 1 is characterized in that: The computational fluid dynamics simulation software is STARCCM+, which solves the unidirectional force of the incoming wind on the blade surface based on the basic principles of fluid mechanics. F , expressed as: ,in, C p is the surface pressure coefficient of the blade under the unidirectional action of the incoming wind, ρ is the fluid density, v is the flow rate, A is the blade force area.

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