A wind turbine main shaft design method based on stress field

Abstract

The present invention provides a wind turbine main shaft design method based on stress field, comprising the following steps: S1, establishing a finite element model; S2, determining the stress gradient in the radial direction, and performing differentiated stratification; S3, assigning mechanical performance levels of different regions to different strata; S4, verifying the ultimate stress level and fatigue damage value of the main shaft; S5, performing structural optimization according to the verified stress and level and fatigue damage value. The main shaft finite element model is accurately layered and divided at different load levels, and the grid nodes between different levels are matched one by one through model optimization, so that the load can be smoothly transferred, and different mechanical performance parameters are assigned to different regions based on the actual performance levels of different thickness regions of the actual product. Avoiding the limitation of using a single performance indicator to represent the overall main shaft performance makes the finite element model of the main shaft closer to the actual load situation, thereby improving the design level of the main shaft and improving the competitiveness of the unit.

Description

Technical Field

[0001] The invention relates to the technical field of wind power generation, and in particular to a wind turbine main shaft design method based on a stress field. Background Art

[0002] With the parity of wind power market, higher requirements are put forward for the performance and reliability of wind turbine products. The main shaft, as one of the key components of the unit's transmission chain system, is directly related to the subsequent bearing selection, main frame and bearing seat design. Improving the reliability of the main shaft part design can control the cost and reliability of the unit as a whole from the transmission chain level.

[0003] The traditional mechanical performance parameter selection of spindle strength verification is based on the actual performance level of the sample at a certain position selected according to the relevant standards, without considering the performance distribution of the actual production finished parts, nor the actual stress field of the shaft parts, which easily leads to the failure of the spindle strength verification. This kind of problem is generally solved by increasing the shaft diameter, which will lead to an increase in the bearing model, an increase in the size of related structural parts, and a decrease in the competitiveness of the whole machine. Summary of the invention

[0004] In view of this, the problem to be solved by the present invention is to provide a wind turbine main shaft design method based on stress field, avoiding the limitation of representing the overall main shaft performance by a single performance indicator, making the finite element model of the main shaft closer to the actual load condition, thereby improving the design level of the main shaft and improving the competitiveness of the unit.

[0005] The present invention solves the above technical problems through the following technical means: The present invention provides a wind turbine main shaft design method based on stress field, comprising the following steps:

[0006] S1. Establish the initial finite element model of the main shaft;

[0007] S2. Based on the finite element model, the force model of the main shaft is analyzed to determine the stress gradient in the radial direction of the main shaft, and the finite element model is differentiated and layered;

[0008] S3. Obtain the mechanical property levels of product materials in different regions, and assign the mechanical property levels of different regions to different layers;

[0009] S4. Verify the ultimate stress level and fatigue damage value of the spindle;

[0010] S5. Structural optimization is performed based on the verified stress and level and fatigue damage value;

[0011] S6. Repeat steps S4 to S5 until the final optimization solution is obtained.

[0012] Furthermore, step S2 also includes analyzing the force model of the main shaft, determining the actual bearing stress level at each radial position of the main shaft, verifying the interval division of the main shaft in the radial direction, and then determining the stress gradient of the main shaft in the radial direction.

[0013] Further, in step S3, based on the stress distribution of the main shaft in the radial direction, the main shaft finite element model is divided into three layers a, b, and c based on the stress field in the radial direction, and each layer is assigned a corresponding mechanical property index value based on the performance of the material.

[0014] Furthermore, in step S4, when checking the fatigue damage value, different fatigue curves are generated for each layer based on the performance of the material for checking.

[0015] Further, in step S5, the structure is optimized according to the verified stress level and fatigue damage value. When the stress level and fatigue damage value meet the preset requirements and the margin is greater than the reference value, weight reduction optimization is performed. When the stress level and fatigue damage value do not meet the preset requirements, shaft diameter increase structural optimization is performed.

[0016] It can be seen from the above technical scheme that the beneficial effects of the present invention are as follows: the present invention provides a wind turbine main shaft design method based on stress field, comprising the following steps: S1, establishing a preliminary finite element model of the main shaft; S2, based on the finite element model, analyzing the force model of the main shaft, determining the stress gradient in the radial direction of the main shaft, and performing differential stratification on the finite element model; S3, obtaining the mechanical performance level of the product material in different regions, and assigning the mechanical performance level of different regions to different layers; S4, verifying the ultimate stress level and fatigue damage value of the main shaft; S5, optimizing the structure according to the verified stress and level and fatigue damage value; S6, repeating steps S4 to S5 until the final optimization scheme is obtained. First, the different load levels of the main shaft finite element model are accurately layered and divided, and then the grid nodes between different levels are matched one by one through model optimization, so that the load can be smoothly transferred, and finally different mechanical performance parameters are assigned to different regions based on the actual performance level of different thickness regions of the actual product. It avoids the limitation of using a single performance indicator to represent the overall spindle performance, making the finite element model of the spindle closer to the actual load conditions, thereby improving the design level of the spindle and the competitiveness of the unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following is a brief introduction to the drawings required for the specific embodiments or the description of the prior art. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn according to the actual scale.

[0018] Figure 1It is a schematic diagram of the process of the present invention;

[0019] Figure 2 This is the stress analysis diagram of the A model spindle;

[0020] Figure 3 This is the stress analysis diagram of the B model shaft;

[0021] Figure 4 is the trend diagram of principal axis stress changing with depth;

[0022] Figure 5 This is the SN curve of 34CrNiMo6 material;

[0023] Figure 6 This is the SN curve of 42CrMo4 performance material. DETAILED DESCRIPTION

[0024] The following embodiments of the technical solution of the present invention are described in detail in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and are therefore only used as examples, and cannot be used to limit the protection scope of the present invention.

[0025] See also Figures 1 to 6 As shown, the present invention provides a wind turbine main shaft design method based on stress field, comprising the following steps:

[0026] S1. Establish the initial finite element model of the main shaft;

[0027] S2. Based on the finite element model, the force model of the main shaft is analyzed to determine the stress gradient in the radial direction of the main shaft, and the finite element model is differentiated and layered; the force model of the main shaft is analyzed to determine the actual bearing stress level at each radial position of the main shaft, the interval division of the main shaft in the radial direction is verified, and then the stress gradient of the main shaft in the radial direction is determined.

[0028] Specifically, the trend of the main axis stress along the radial direction is analyzed in the finite element model; through the verification of the finite element model, such as Figures 2-3 As shown, the stress level decreases sharply from the skin to the center along the radial direction of the main axis.

[0029] Table 1. Decrease trend of principal axis stress along radial direction

[0030]

[0031] S3. Obtain the mechanical property levels of product materials in different areas, and assign the mechanical property levels of different areas to different layers; based on the radial stress distribution of the main shaft, divide the main shaft finite element model into three layers a, b, and c based on the stress field in the radial direction. Each layer is assigned a corresponding mechanical performance index value based on the performance of the material, where layer a: within 10 mm subcutaneous; layer b: between 10 mm and 40 mm subcutaneous; layer c: between 40 mm subcutaneous and the core.

[0032] Specifically, the main materials of the main shaft in the industry are 42CrMo4 and 34CrNiMo6. Under the existing heat treatment process level, the mechanical properties of the finished main shafts of the two materials at various radial positions are mainly shown in Table 2.

[0033]

[0034] S4. Verify the ultimate stress level and fatigue damage value of the main shaft; when checking the fatigue damage value, generate different fatigue curves for each layer based on the material performance for verification. Assign the performance index values ​​that can be assigned to different grid areas to different layers to obtain fatigue life curves.

[0035] The mechanical performance index values ​​that can be assigned to different grid areas according to the layering are shown in Table 3:

[0036]

[0037] S5. Perform structural optimization based on the verified stress level and fatigue damage value; Perform structural optimization based on the verified stress level and fatigue damage value. When the stress level and fatigue damage value meet the preset requirements and the margin is greater than the reference value, perform weight reduction optimization. When the stress level and fatigue damage value do not meet the preset requirements, perform structural optimization by increasing the shaft diameter.

[0038] S6. Repeat steps S4 to S5 until the final optimization solution is obtained.

[0039] Since the ultimate strength verification result is linearly related to the load level, the ultimate strength verification result after adopting the present invention is not significantly different; since the fatigue damage value is closely related to the fatigue life curve, the fatigue damage value result after adopting the present invention has been significantly improved compared with before. After adopting the calculation method of the present invention, the actual performance of the parts is obviously more fully utilized. Taking the main shaft of a megawatt model as an example, the difference in strength verification results is shown in Table 4.

[0040] Ultimate stress level Fatigue damage value Prior art 347.6Mpa 2.417 This program 338.4Mpa 0.723

[0041] The present invention proposes differentiated modeling of the finite element model based on the stress field of the main shaft of the wind turbine generator set. By adjusting the number of grids, nodes and other optimization measures, the finite element model can be made to simulate the actual load conditions of the product more directly, providing strong support for the design of the main shaft of the wind turbine generator set. The performance level of the actual production product in different radial regions is fully combined with the finite element model, and different mechanical performance levels are given to different regions, and different fatigue life curves are loaded. The actual performance of the product can be fully utilized in the strength verification stage to avoid excess mass, thereby further reducing weight and optimizing, and improving the competitiveness of the unit.

[0042] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. These modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be included in the scope of the claims and specification of the present invention.

Claims

1. A wind turbine main shaft design method based on stress field, characterized in that: The steps include: S1. Establish the initial finite element model of the main shaft; S2. Based on the finite element model, the force model of the main shaft is analyzed to determine the stress gradient in the radial direction of the main shaft, and the finite element model is differentiated and layered; S3. Obtain the mechanical property levels of product materials in different regions, and assign the mechanical property levels of different regions to different layers; S4. Verify the ultimate stress level and fatigue damage value of the spindle; S5. Structural optimization is performed based on the verified stress and level and fatigue damage value; S6. Repeat steps S4 to S5 until the final optimization solution is obtained.

2. The wind turbine main shaft design method based on stress field according to claim 1 is characterized in that: Step S2 also includes analyzing the force model of the main shaft, determining the actual bearing stress level at each radial position of the main shaft, verifying the interval division of the main shaft in the radial direction, and then determining the stress gradient of the main shaft in the radial direction.

3. The wind turbine main shaft design method based on stress field according to claim 2 is characterized in that: In step S3, based on the stress distribution of the spindle in the radial direction, the spindle finite element model is divided into three layers a, b, and c based on the stress field in the radial direction, and each layer is assigned a corresponding mechanical property index value based on the performance of the material.

4. The wind turbine main shaft design method based on stress field according to claim 3 is characterized in that: In step S4, when checking the fatigue damage value, different fatigue curves are generated for each layer based on the performance of the material for checking.

5. The wind turbine main shaft design method based on stress field according to claim 4 is characterized in that: In step S5, the structure is optimized according to the verified stress level and fatigue damage value. When the stress level and fatigue damage value meet the preset requirements and the margin is greater than the reference value, weight reduction optimization is performed. When the stress level and fatigue damage value do not meet the preset requirements, shaft diameter increase structural optimization is performed.

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