CN105760629A - Lamination optimum design method of wind turbine blade main beam - Google Patents

Abstract

A wind turbine blade main girder layup optimization design method, the method includes blade structure analysis: based on the beam and shell theory, the blade is simplified into a cantilever beam, and combined with the given blade parameters to carry out the blade section geometric characteristics, load internal force, stress-strain and blade Calculation of ply thickness; optimization of genetic algorithm: optimal design of ply thickness of wind turbine blades, constrained by the stiffness and strength of wind turbine blades, and aiming at the minimum mass of blades, to determine the ply thicknesses at different positions of the blades; the present invention utilizes the compiled The optimized design program calculates the blade layup thickness for the specific environment. The calculation results show that the quality of the blade decreases when the stiffness and strength conditions are met, and the optimized model is practical and effective.

Description

Optimal design method for main girder layup of wind turbine blades

technical field

The invention relates to a large wind turbine blade, in particular to an optimal design method for the ply thickness of the main girder of the wind turbine blade.

Background technique

The problem of global warming is becoming more and more serious, and renewable clean energy has attracted much attention. Wind energy, as an available green energy, has great prospects for development. The effective use of wind energy depends on wind turbines. As a device for directly capturing wind energy, wind turbine blades are an important part of wind turbines. The trend of wind turbines is towards large-scale development. Although the increase of the blades can increase the power of the wind turbine, it will also bring a lot of structural burdens, the weight of the blades will increase, and the force on the blades will increase. These changes will bring a series of effects, so the structural design of wind turbine blades is very important for blade design.

For large (megawatt) wind turbine blades, the structure of the blade is mainly composed of main beams, skins and other structures. The blades are generally shell structures, and the main beam part is the main force-bearing structure. Megawatt wind turbines usually operate in a complex and changeable environment. The blades are subjected to aerodynamic loads, centrifugal loads, and gravity loads. The increase in blade size will lead to an increase in its own weight, which not only increases the cost of the blades but also drags down the wind power. machine operating efficiency.

Therefore, for large-scale wind turbine blades, the genetic algorithm combined with modular programming is used to divide the blade design into four parts to realize the optimal design of the blade lay-up thickness, so that the blade can reduce the weight of the blade under the condition of satisfying the stiffness.

The blade layup optimization design can effectively reduce the blade weight, further realize the large-scale wind turbine and increase the power of a single wind turbine, and the reduction of the blade weight can reduce its own burden, which means that the blade can reduce a certain fatigue load and prolong its service life. In the long run, optimizing the design of blade layup thickness can effectively save costs.

Contents of the invention

The purpose of the present invention is to provide a wind turbine blade main girder layup optimization design method.

The present invention is a wind turbine blade main girder layup optimization design method, the steps of which are:

(1) The aerodynamic shape parameters of the blade are determined. The main beam of the blade is a box-shaped main beam. The blade section is in the form of a main beam plus skin structure. The blade is discretized along the span direction to obtain n cross-sections. The area of each section is divided into three parts. A ₁ , girder cap area A ₂ and shear web area A ₃ , the area of the entire section is A=A ₁ +A ₂ +A ₃ ;

(2) The formula for calculating the cross-sectional area moment according to the skin area in step (1) is as follows:

, ;

Further, the section centroid is equal to: , ;

The moment of inertia of the blade section is equal to , , , the moment of inertia under the principal axis coordinates can be obtained through coordinate conversion;

(3) Calculate the blade load and internal force. Under normal working conditions, the blade is subjected to aerodynamic force, centrifugal force and its own gravity;

(4) The aerodynamic bending moment and torque can be calculated according to the section geometric characteristic parameters calculated in step (2), the formula is as follows:

, ;

;

In the formula, blade aerodynamic center, is the torsion center of the blade section;

(5) The bending moment and torque of the gravity load on the blade can be calculated according to the following formula:

,

;

in , are the converted density and cross-sectional area of the blade, respectively, is the acceleration of gravity, is the blade rotation azimuth, is the coordinates of the center of gravity of the blade;

(6) The calculation formulas for the bending moment and torque of the centrifugal force load on the blade are as follows:

, ;

;

in, , for the blade Center of gravity at section;

(7) The bending moment and torque calculated in step (3), step (4) and step (5) correspond to the section coordinate system. Further, the section internal force is transformed into the section centroid position coordinate system, including the first principal axis and the second spindle , the calculation formula of blade bending normal stress is:

, ;

Among them, M is the bending moment and I is the corresponding axis, the moment of inertia of the first principal axis, Indicates the maximum value of the off-axis of the discrete points of the section;

(8) Each blade section is divided into three parts: skin, main spar cap and shear web; the thickness of the blade layup is calculated using the equivalent design, and the skin is laid with bidirectional cloth, which provides sufficient The shear strength is calculated as:

;

In the formula, for the first and the first the width of the panels between the webs; is the thickness of a single layer of bidirectional fabric; The minimum number of layers laid for a single layer of bidirectional fabric;

(9) The main beam is laid with unidirectional fabric, and the thickness of the unidirectional fabric can be calculated according to the strength criterion. The specific calculation formula is as follows:

;

The above formula shows that different calculated stiffnesses can be obtained according to different layer thicknesses. When the stiffness calculated by substituting different layer thicknesses into the above formula can meet the maximum stress requirement, the blade thickness meets the requirements;

(10) According to the genetic algorithm, set the thickness of the blade layer as a variable, and calculate the geometric characteristic parameters of the section, the force on the section, and the stress on the blade according to the above steps and sequence, and finally obtain the layer thickness that satisfies the conditions according to the strength criterion;

When iteratively calculating the thickness of the blade ply, the ply thickness that meets the strength requirements and minimizes the mass of the blade is selected as the output result.

Compared with the prior art, the present invention adopts modularization to deal with complex parameter calculation in the blade structure design process, and divides the blade structure design part into four parts. Combined with the genetic algorithm, the appropriate stiffness and strength conditions are set, and the thickness of the blade layup is optimally designed with the weight of the blade as the target. The optimal design program of the present invention designs the ply thickness of the cross-section for specific operating conditions. The calculation results show that the weight of the optimized blade is reduced without losing the original stiffness and strength, which proves the practicability and effectiveness of the optimized model.

Description of drawings

Figure 1 shows the calculation flow chart of the optimization model of the blade layup thickness, Figure 2 shows the schematic diagram of the blade section structure, Figure 3 shows the comparison before and after the optimization of the layup thickness of the main beam of the blade, and Figure 4 shows the comparison before and after the optimization of the layup thickness of the front and rear edge of the blade.

detailed description

The present invention adopts following technical scheme:

The first step is to select the appropriate aerodynamic shape parameters, divide the blades equidistantly into n segments to obtain your cross-section, and calculate the area of each section given the initial main beam lay-up thickness parameters;

The second step is to calculate the section area moments S _x , S _y , centroids X _c , Y _c , and moments of inertia I _x , I _y , I _xy ;

The third step is to calculate the bending moment and torque of the aerodynamic force, gravity and centrifugal force on the blade;

The fourth step is to calculate the linear density of the blade mass as the fitness value and the stiffness of a given layer thickness, and compare it with the maximum stress to eliminate the layer thickness that does not meet the requirements.

The fifth step is to obtain the optimization result by iterating a certain number of steps and select the optimal value for output.

Based on the above method, a 1.5MW wind turbine blade is taken as an example to optimize the design. Figure 1 shows the flow chart of the optimization calculation of the blade lay-up thickness. Figure 2 shows the schematic diagram of the blade lay-up structure. The comparison before and after optimization of the ply thickness of the main girder. Figure 4 shows the comparison before and after the optimization of the ply thickness of the leading and trailing edges of the blade.

As shown in Figure 1, the present invention is a wind turbine blade main girder layup optimization design method, and its steps are:

(1) The aerodynamic shape parameters of the blade are determined. The main beam of the blade is a box-shaped main beam. The blade section is in the form of a main beam plus skin structure. The blade is discretized along the span direction to obtain n cross-sections. The area of each section is divided into three parts. A ₁ , girder cap area A ₂ and shear web area A ₃ , the area of the entire section is A=A ₁ +A ₂ +A ₃ ;

(2) The formula for calculating the cross-sectional area moment according to the skin area in step (1) is as follows:

, ;

Further, the section centroid is equal to: , ;

The moment of inertia of the blade section is equal to , , , the moment of inertia under the principal axis coordinates can be obtained through coordinate conversion;

(3) Calculate the blade load and internal force. Under normal working conditions, the blade is subjected to aerodynamic force, centrifugal force and its own gravity;

(4) The aerodynamic bending moment and torque can be calculated according to the section geometric characteristic parameters calculated in step (2), the formula is as follows:

, ;

;

In the formula, blade aerodynamic center, is the torsion center of the blade section;

(5) The bending moment and torque of the gravity load on the blade can be calculated according to the following formula:

,

;

in , are the converted density and cross-sectional area of the blade, respectively, is the acceleration of gravity, is the blade rotation azimuth, is the coordinates of the center of gravity of the blade;

(6) The calculation formulas for the bending moment and torque of the centrifugal force load on the blade are as follows:

, ;

;

in, , for the blade Center of gravity at section;

(7) The bending moment and torque calculated in step (3), step (4) and step (5) correspond to the section coordinate system. Further, the section internal force is transformed into the section centroid position coordinate system, including the first principal axis and the second spindle , the calculation formula of blade bending normal stress is:

, ;

Among them, M is the bending moment and I is the corresponding axis, the moment of inertia of the first principal axis, Indicates the maximum value of the off-axis of the discrete points of the section;

(8) Each blade section is divided into three parts: skin, main spar cap and shear web; the thickness of the blade layup is calculated using the equivalent design, and the skin is laid with bidirectional cloth, which provides sufficient The shear strength is calculated as:

;

In the formula, for the first and the first the width of the panels between the webs; is the thickness of a single layer of bidirectional fabric; The minimum number of layers laid for a single layer of bidirectional fabric;

(9) The main beam is laid with unidirectional fabric, and the thickness of the unidirectional fabric can be calculated according to the strength criterion. The specific calculation formula is as follows:

;

The above formula shows that different calculated stiffnesses can be obtained according to different layer thicknesses. When the stiffness calculated by substituting different layer thicknesses into the above formula can meet the maximum stress requirement, the blade thickness meets the requirements;

(10) According to the genetic algorithm, set the thickness of the blade layer as a variable, and calculate the geometric characteristic parameters of the section, the force on the section, and the stress on the blade according to the above steps and sequence, and finally obtain the layer thickness that satisfies the conditions according to the strength criterion;

When iteratively calculating the thickness of the blade ply, the ply thickness that meets the strength requirements and minimizes the mass of the blade is selected as the output result.

Claims (1)

1. The wind turbine blade main beam laying optimization design method is characterized by comprising the following steps:

(1) determining aerodynamic shape parameters of the blade, wherein a blade girder is a box-shaped girder, the blade section is in a girder and skin structure form, the blade is discretized in the spanwise direction to obtain n cross sections, and each section area is divided into three skin areas A₁Area of main girder cap A₂And shear web area A₃The area of the whole cross section is A = A₁+A₂+A₃；

(2) Calculating the sectional area moment formula according to the skin area in the step (1) as follows:

、；

further, the cross-sectional centroid is equal to:，；

blade section moment of inertia equal to、、The inertia moment under the main shaft coordinate can be obtained through coordinate transformation;

(3) calculating the load and the internal force of the blade, wherein the blade is subjected to aerodynamic force, centrifugal force and self gravity in a normal working state;

(4) and (3) calculating the aerodynamic bending moment and the aerodynamic torque according to the section geometric characteristic parameters calculated in the step (2), wherein the formula is as follows:

，；

；

in the formula,the aerodynamic center of the blade is provided with a plurality of blades,is the blade section torsion center;

(5) the bending moment and the torque of the gravity load borne by the blade can be calculated according to the following formulas:

，

；

wherein、Respectively the reduced density and the cross-sectional area of the blade,in order to be the acceleration of the gravity,in the form of the blade rotation azimuth angle,the coordinates of the gravity center of the blade are taken;

(6) the calculation formula of the bending moment and the torque of the centrifugal force load borne by the blade is as follows:

，；

；

wherein,、is a bladeThe center of gravity at the section;

(7) the bending moment and the torque obtained by calculation in the step (3), the step (4) and the step (5) correspond to a section coordinate system, and further, the section internal force is converted into a section centroid position coordinate system comprising a first main shaftAnd a second main shaftThe positive bending stress calculation formula of the blade is as follows:

，；

wherein M is bending moment I corresponding toThe moment of inertia of the shaft, i.e. the first main shaft,represents the maximum value of deviation of the discrete points of the cross section from the axis;

(8) the section of each blade is divided into three parts: skin, spar caps, and shear webs; the blade layer thickness is calculated by adopting an equal generation design, the covering adopts a bidirectional cloth layer, the covering bidirectional cloth layer provides enough shearing strength, and the calculation formula is as follows:

；

in the formula,is as followsIs first and secondThe width of the panel between webs;is the thickness of the bidirectional drape layer;the minimum number of layers for laying bidirectional cloth single layers;

(9) the thickness of the unidirectional cloth laying layer for the girder can be calculated according to the strength criterion, and the specific calculation formula is as follows:

；

the above formula shows that different calculated stiffness can be obtained according to different layer thicknesses, and when the stiffness obtained by substituting different layer thicknesses into the above formula can meet the maximum stress requirement, the blade thickness meets the requirement;

(10) according to a genetic algorithm, the thickness of the layering of the blade is set as a variable, according to the steps and the sequence, the geometric characteristic parameters of the section, the stress of the section and the stress of the blade are calculated, and finally the layering thickness meeting the conditions is obtained according to the strength criterion;

and when the thickness of the blade layer is calculated in an iterative manner, selecting the layer thickness which meets the strength requirement and enables the blade mass to be minimum as an output result.