A method for predicting the glue filling volume for repairing damage to in-service high-altitude wind turbine blades

Abstract

A method for predicting the volume of resin used for repairing damage to in-service high-altitude wind turbine blades involves preparing glass fiber splines with prefabricated cracks and conducting tensile testing. The method then establishes a correlation between damage and strain in glass fiber composite wind turbine blades based on the strain change rate (the ratio of the strain of the prefabricated cracked spline to the strain of the crack-free spline) and the damage percentage (the ratio of the crack length to the spline width) of the prefabricated cracked spline when the spline is damaged. In-service blade strain is monitored using a surface-mounted Fiber Bragg Grating (FBG) strain monitoring system. When abnormal strain is detected for a long period of time, the blade damage percentage is determined based on the abnormal strain and the damage-strain correlation mechanism. The damage extent is then determined based on the thickness of the measured location and the damage area. This method allows for accurate prediction of the resin volume required for repair, providing important guidance for repairing wind turbine blades with resin.

Description

Technical Field

[0001] The present invention relates to the field of wind power generation, and in particular to a method for predicting the glue filling volume for repairing damage to in-service high-altitude wind turbine blades. Background Art

[0002] The current manufacturing process for large wind turbine blades is through manual laying and mold closing, and minor defects are inevitable during the manufacturing process. During their service, due to the harsh environment, sand and gravel, storms, heavy rain and snowfall, these minor defects will expand internally, causing interlayer debonding damage inside the blades, affecting their operating status.

[0003] Fiber Bragg grating (FBG) strain monitoring is a commonly used method for monitoring the health of in-service blades. When the grating is subjected to stress, its wavelength changes, and the change in wavelength is proportional to the change in stress. The fiber Bragg grating (FBG) strain sensor calculates the strain of the blade by monitoring the wavelength change. When the strain is abnormal, it indicates that the blade is damaged.

[0004] When blades experience interlaminar debonding damage, they require repair by pouring glue. However, in-service blades are typically located over 70 meters above the ground. This requires repair workers to transport resin glue to the hub via an elevator inside the tower. The specific glue volume typically requires workers to estimate. If insufficient glue is delivered, repair requirements will be insufficient. Excessive amounts will increase the workload and repair costs. Therefore, precise, quantitative guidance for glue pouring repairs is urgently needed for wind turbine blade damage repair. Summary of the Invention

[0005] (1) Purpose of the invention

[0006] In order to solve the above technical problems, the present invention provides a method for predicting the glue filling volume for repairing damage to in-service high-altitude wind turbine blades. By establishing a correlation mechanism between damage and strain in glass fiber composite wind turbine blades, the glue filling repair volume is accurately predicted to guide the blade glue filling repair process.

[0007] (2) Technical solution

[0008] Step 1: Prepare glass fiber specimens with prefabricated cracks and perform tensile failure tests on the specimens to establish the correlation mechanism between damage and strain in glass fiber composite wind turbine blades;

[0009] Step 2: Use the FBG strain monitoring system to monitor the strain of in-service wind turbine blades in real time;

[0010] Step 3: When long-term abnormal strain is monitored, the injection volume is predicted based on the correlation mechanism between damage and strain, and the blade damage is repaired.

[0011] Furthermore, the preparation of the glass fiber spline with prefabricated cracks comprises the following specific steps:

[0012] Glass fiber splines were prepared based on the RTM molding process, with the direction of the glass fiber bundles parallel to the tensile direction;

[0013] The prefabricated crack is located in the middle of the spline, perpendicular to the tensile direction;

[0014] The upper and lower reinforcing plates are glued to both ends of the spline for clamping in the tensile tester.

[0015] Furthermore, the specific steps of the tensile failure test are as follows:

[0016] The upper and lower chucks of the tensile strain tester clamp the reinforcing sheet on the specimen;

[0017] The extensometer clamps the middle of the spline and is used to test the strain during the stretching process of the spline;

[0018] Furthermore, the specific steps of establishing the correlation mechanism between damage and strain of glass fiber composite wind turbine blades are as follows:

[0019] Record the corresponding strain value when damage cracks extend on splines with different prefabricated crack lengths;

[0020] The ratio of the strain value of the pre-cracked spline to the strain value of the uncracked spline when damage occurs is calculated as the strain change rate;

[0021] The damage ratio is obtained by calculating the ratio of the pre-crack length to the spline width;

[0022] According to the strain change rate and its corresponding damage ratio, a correlation mechanism between the two is established.

[0023] Furthermore, the FBG strain monitoring system is used to monitor the strain of in-service wind turbine blades in real time. The specific steps are as follows:

[0024] Surface-mounted FBG sensors are distributed and attached to different locations inside the leaf;

[0025] The sensor is connected to the strain demodulator to monitor the strain signal generated by the rotation of the fan blades in real time;

[0026] The strain demodulator is installed in the blade hub equipment area, and the monitoring data is processed and transmitted to the monitoring room.

[0027] Furthermore, the specific steps for predicting the glue filling volume based on the correlation mechanism between damage and strain change are as follows:

[0028] Based on the measured abnormal strain, the corresponding damage ratio is obtained according to the correlation mechanism between damage ratio and strain change rate;

[0029] According to the damage ratio, the thickness of the sensor is measured to obtain the damage amount in the thickness direction;

[0030] Measure the size of the damaged area and multiply it by the amount of damage to get the volume of the damaged area, which is the volume that needs to be repaired by glue injection.

[0031] (3) Beneficial effects

[0032] The above technical solution of the present invention has the following beneficial effects:

[0033] This invention addresses the urgent need for precise, quantitative guidance for glue-filling repairs of damaged, high-altitude blades in service. It establishes a correlation between wind turbine blade damage and strain, accurately predicting the volume of resin required for glue-filling repairs. This invention addresses the issue of unknown resin glue requirements during glue-filling repairs. It avoids situations where maintenance workers carrying too little glue during high-altitude operations result in incomplete repairs, while carrying too much glue increases the workload and costs of high-altitude operations. This invention effectively improves repair efficiency and provides important guidance for glue-filling repairs of wind turbine blades. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a flow chart of the method for predicting the glue filling volume of the present invention;

[0035] Figure 2 Schematic diagram of the tensile process of glass fiber spline with prefabricated cracks;

[0036] Figure 3 The strain and strain change rate diagrams of splines with different prefabricated cracks;

[0037] Figure 4 Schematic diagram of FBG strain monitoring system;

[0038] Figure 5 Comparison of strain data before and after injury;

[0039] Figure 6 Comparison of strain data before and after repair;

[0040] Reference numerals:

[0041] 1: Upper chuck of tensile strain tester, 2: Lower chuck of tensile strain tester, 3: Extensometer, 401: Upper reinforcement plate, 402: Tensile direction, 403: Glass fiber, 404: Prefabricated crack, 405: Lower reinforcement plate, 501: Strain demodulator, 502: Optical fiber, 503: Sensor, 504: Blade. DETAILED DESCRIPTION

[0042] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings. It should be understood that these descriptions are only exemplary and are not intended to limit the scope of the present invention.

[0043] Figure 1 This is a flow chart of a method for predicting the volume of resin used to repair damage in high-altitude wind turbine blades. First, a glass fiber spline with prefabricated cracks is prepared and subjected to tensile testing. The correlation between damage and strain in glass fiber composite wind turbine blades is established based on the strain change rate when the spline is damaged and the damage percentage of the prefabricated cracked spline. An FBG strain monitoring system is used to monitor strain in the in-service blades. When abnormal strain is detected over a long period of time, the abnormal strain is used to determine the blade damage percentage based on the damage-strain correlation mechanism. The damage extent is then determined based on the thickness of the measured location and the damage area, allowing for an accurate prediction of the resin volume required for the repair.

[0044] The preparation of glass fiber splines with prefabricated cracks is to prepare a 350mm×500mm×2mm glass fiber sample according to the RTM molding process, and then cut the sample into 250mm×25mm×2mm splines and 50mm×25mm×2mm reinforcement sheets. The surface of the reinforcement sheet and the spline is polished with 1000 mesh sandpaper to increase the roughness, so that the reinforcement sheet and the spline are firmly adhered, and the reinforcement sheet is adhered to the upper and lower ends of the spline with adhesive film, and placed in a hot press with a set temperature of 90°C and a pressure of 2MPa for two hours. Cracks with lengths of 0mm, 3mm, 6mm, and 9mm are prefabricated on one side of the middle of the spline. When the spline is stretched, the specimen is clamped on the tensile testing machine to ensure that the direction of the glass fiber bundle is parallel to the tensile direction. According to the test standard of the plastic tensile test guideline GB / T1040.1-2018, the tensile speed is set to 2mm / min, and the strain is measured with an extensometer. Figure 2 The figure shows a schematic diagram of the stretching of a glass fiber spline with prefabricated cracks. In the figure, the direction of the glass fiber bundle (403) of the spline is parallel to the stretching direction (402), and the prefabricated crack (404) is located in the middle of the spline, perpendicular to the stretching direction. Reinforcement sheets (401) and (405) are used to increase friction when clamping the tensile tester to prevent slipping during the stretching process. The upper chuck (1) and lower chuck (3) of the tensile strain tester clamp the reinforcement sheet on the spline, and the extensometer (3) is located in the middle of the spline to test the strain of the spline during stretching.

[0045] Record the corresponding strain and strain change rate when the damage crack propagates on splines with different prefabricated crack lengths. Figure 3 As shown, from Figure 3As can be seen from the data, the strain corresponding to crack propagation increases with increasing pre-crack size. The strain at internal crack initiation in the unpre-cracked specimen is 7001 με. The corresponding strain for the 3mm pre-cracked specimen is 7616 με, an increase of approximately 10% compared to the unpre-cracked specimen, reaching 110%. The strain for the 6mm pre-crack is 9784 με, an increase of approximately 40% compared to the unpre-cracked specimen, reaching 140%. The strain for the 9mm pre-crack reaches 14335 με, an increase of approximately 100% compared to the unpre-cracked specimen, reaching 200%. Furthermore, since the tensile specimen width is 25mm, 3mm-wide cracks account for 12% of the damage, 6mm-wide cracks account for 24%, and 9mm-wide cracks account for 36%. A correlation mechanism between the damage ratio and the strain change rate was established, namely, if the strain reaches about 110% of the normal level and is maintained for a long time, 12% damage will occur in the thickness direction of the blade; if the strain reaches about 140% of the normal level and is maintained for a long time, 24% damage will occur in the thickness direction of the blade; if the strain reaches about 200% of the normal level and is maintained for a long time, 36% damage will occur in the thickness direction of the blade.

[0046] Utilize FBG strain monitoring system to monitor the strain changes of in-service wind turbine blades in real time, such as Figure 4 As shown, surface-mounted FBG sensors (503) are distributed and attached to different locations of the blade (504), and are connected to a strain demodulator (501) via an optical fiber (502) to monitor the strain signal generated when the wind turbine blade rotates; the strain demodulator (501) is installed in the blade hub equipment area to collect and process the monitoring data and transmit it to the monitoring room.

[0047] The strain sensor detected that the blade strain increased by 9% compared with the initial value and maintained for a long time, indicating that damage occurred inside the blade, such as Figure 5 As shown. Based on the correlation mechanism between damage ratio and strain change rate, the damage ratio is predicted to be about 12%. The thickness of the blade where the sensor is attached is about 45mm, and the calculated damage thickness is about 5.4mm. The irregular white damage area observed inside the blade is measured to be 0.39mm. 2 The calculation predicts that the required resin glue for glue repair is about 2.106 liters. After glue repair, the damage disappears and the glue volume is about 2 liters, with an error of 5.3%. The strain data after repair is as follows Figure 6 As shown in the figure, it can be seen that the strain monitoring data is restored to the level before the damage after the glue filling repair, indicating that the damage repair is completed and the blade returns to normal working state.

[0048] In summary, the present invention provides a method for predicting the glue filling volume for repairing damage to in-service high-altitude wind turbine blades, which effectively solves the problem of accurate quantification during glue filling repair, improves the repair efficiency, and provides important guidance for the repair of damage to wind turbine blades.

[0049] Finally, it is necessary to point out here that the above-mentioned specific embodiments of the present invention are only used to illustrate or explain the principles of the present invention, and do not constitute a limitation of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above-mentioned contents of the present invention are within the scope of protection of the present invention.

Claims

1. A method for predicting the glue filling volume for repairing damage to in-service high-altitude wind turbine blades, characterized in that: The method comprises the following steps: Step 1: Prepare glass fiber splines with prefabricated cracks, perform tensile failure tests on the splines, and establish the correlation mechanism between damage and strain in glass fiber composite wind turbine blades; Step 2: Use the FBG strain monitoring system to monitor the strain of the in-service wind turbine blades in real time; Step 3: When long-term abnormal strain is monitored, the glue filling volume is predicted based on the correlation mechanism between damage and strain, and the blade damage is repaired. Surface-mounted FBG sensors are distributed and attached to different locations inside the blade. The corresponding damage percentage is calculated based on the measured abnormal strain and the correlation mechanism between the damage percentage and the strain change rate. Based on the damage percentage, the thickness of the sensor location is measured to determine the damage amount in the thickness direction. The size of the damaged area is measured and multiplied by the damage amount to obtain the volume of the damaged area, which is the volume requiring glue filling repair.

2. The method for predicting the glue filling volume for repairing damage to in-service high-altitude wind turbine blades according to claim 1 is characterized in that: In step 1, a glass fiber spline with prefabricated cracks is prepared as follows: Glass fiber splines were prepared based on the RTM molding process, with the direction of the glass fiber bundles parallel to the tensile direction; A crack is prefabricated in the middle of the spline, with the crack direction perpendicular to the tensile direction; The upper reinforcement sheet and the lower reinforcement sheet are bonded to both ends of the spline.

3. The method for predicting the glue filling volume for repairing damage to in-service high-altitude wind turbine blades according to claim 1 is characterized in that: In step 1, the specific steps of the tensile failure test are as follows: The upper and lower chucks of the tensile strain tester clamp the reinforcing sheet on the specimen; The extensometer clamps the middle of the specimen and is used to test the strain during the tensile process of the specimen.

4. The method for predicting the glue filling volume for repairing damage to in-service high-altitude wind turbine blades according to claim 1 is characterized in that: In step 1, the correlation mechanism between damage and strain of glass fiber composite wind turbine blades is established. The specific steps are as follows: Record the corresponding strain value when damage cracks extend on splines with different prefabricated crack lengths; The ratio of the strain value of the pre-cracked spline to the strain value of the uncracked spline when damage occurs is calculated as the strain change rate; The damage ratio is obtained by calculating the ratio of the pre-crack length to the spline width; According to the strain change rate and its corresponding damage ratio, a correlation mechanism between the two is established.

5. The method for predicting the glue filling volume for repairing damage to in-service high-altitude wind turbine blades according to claim 1 is characterized in that: In step 2, the FBG strain monitoring system is used to monitor the strain of the in-service wind turbine blades in real time. The specific steps are as follows: The sensor is connected to the strain demodulator to monitor the strain signal generated by the rotation of the fan blades in real time; The strain demodulator is installed in the blade hub equipment area, and the monitoring data is processed and transmitted to the monitoring room.

Images