Development process and technical details of blade

Development process and technical details of the world's largest wind turbine blade

development process and technical details of the world's largest wind turbine blade

February 7, 2018

[China paint information]

the 88.4-meter-long composite wind turbine blade produced by LM wind energy company in Denmark is the longest blade produced by the global wind turbine blade manufacturer so far, which is similar to the length of a 100 yard American football field. The sweeping area of the 88.4m blade fan is equivalent to the size of three football fields, and the power output can be used by a small town

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the blade is named LM 88.4 P, which is 15 meters longer than LM 73.5 P, the longest blade ever produced by LM, but the weight is only increased by 6 tons. This is achieved by introducing light carbon fiber with high strength and high stiffness into the laminate of the blade main beam

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carbon fiber has been used in the manufacture of fan blades for more than 10 years. It is mainly carbon fiber reinforced epoxy resin prepreg main beam produced by pultrusion process, and its higher price is justified by the competitive unit megawatt hour energy generation cost (lcoe). Now, LM has explored a different method to embed the carbon glass hybrid reinforced composite girder into the standard glass fiber composite base shell laminate along the length direction. In this way, the blade shell and the main beam can be manufactured in the same mold, and the blade shell acts as the mold of the carbon glass hybrid composite main beam, which greatly saves time and cost. Michael Lund laverick, director of LM composite technology project, said, "LM 88.4 P is the first blade profile produced by hybrid reinforcement technology, which is manufactured by dry carbon glass hybrid fiber placement and vacuum assisted resin transfer molding (VARTM)." The hybrid enhanced design enables LM to produce LM 88.4 P blade profile by using the existing process, significantly improving its core competitiveness. Fully meet the design specifications of cost and construction period established by the customer. Lund laverick added, "we chose the technology scheme that is closest to the actual application, which significantly reduced the risk and promoted the rapid development of the technology required by customers."

The user of the blade with a height of

88.4 meters, adwen company (an affiliated enterprise of Siemens gamesa), expressed the hope to use the fan in the offshore wind farm under the condition of class I wind conditions. Therefore, the design engineer of LM 88.4 P blade set the reference wind speed that the blade can withstand as 50 meters/second (112mph), which meets the requirements of class I wind conditions

design driving force of new products: uncertainty and risk

next, the design of blades is affected by the uncertainty of LM's operation strategy. Lund laverick said, "hybrid enhancement method solves the biggest uncertainty problem first, which is also the biggest failure we can think of." LM adopts failure mode effect analysis software (FMEAs) - a formal analysis tool to evaluate the risks of design (DFMEA) and process (PFMEA) to analyze the feasibility of design and process. Of course, before turning to computer-aided, engineers will first discuss the possible risks orally. "In this way, we can manage the progress of the project by controlling risks, and determine the key problems by relying on the company's solid professional knowledge, rich development experience and good communication mechanism. Engineers list the possible problems one by one, and then avoid these problems through corresponding tests and engineering schemes."

the structure analyzed by FMEA is used to determine what kind of tests and experiments to be carried out. In this process, the actual sample parts are trial produced and tested, and the design limits and failure modes are verified before computer modeling and analysis. Computer simulation is also based on reality, not on primary theory, no matter how powerful the theory is

after confirming the wind condition grade, design limit and failure mode of the blade, the engineers used the design program and three-dimensional modeling software package LM blades developed by the company to simulate the static and dynamic fatigue loading of large blades within the limit range, the buckling of large pneumatic panels, the puck fracture criterion for the strength of unidirectional fiber reinforced composites, and other mechanical/strength, chemical/environmental requirements

carbon glass hybrid has the best of both worlds

lm's hybrid technology refers to the technology of using carbon glass hybrid fiber reinforced composite girder to strengthen the laminated plate of blade base shell of standard glass fiber reinforced polyester composite. The glass fiber fabric for blade shell produced according to LM technical requirements is supplied by many suppliers, and the supplier of typical application of H glass fiber is Owens Corning. The laminated plate of blade shell is obtained by pouring LM standard polyester resin into the sandwich structure with Barsa light wood as the core material

the uniaxial carbon fiber/h glass fiber hybrid fabric required for the blade girder was produced by devold AMT as, a Norwegian enterprise affiliated to SAERTEX, which won LM's "2017 best innovation Partner Award". The fiber fabric structure required by the blade shell and main beam is composed of ± 45 ° biaxial fabric, 0 °/± 45 ° composite fabric and 0 ° unidirectional fabric with different areal density. The new fiber fabric combination used for the first time in 88.4m leaves was independently developed by LM team and used with a LM proprietary unknown resin to obtain excellent blade performance. Although the proprietary resin used for pouring the blade main beam has different main chain structure in molecular structure, it can produce strong binding force with the polyester resin used for the blade shell through chemical reaction

carbon glass hybrid manufacturing strategy

the blade is formed by curing the upper and lower parts of the windward side and leeward side. The windward side and leeward side contain a main beam respectively. The carbon glass hybrid production technology includes two stages of pouring process: the first stage is the blade shell, which contains all structural elements except the main beam. The manufacturing steps are as follows:

plus the commissioning and running in of the production line, spray gel coat in the 88.4 meter mold: workers spray gel coat on the inner surface of the mold before laying the glass fiber fabric used for the blade shell, which can omit the spray painting process after the blade is demoulded

lay the biaxial glass fiber fabric covering layer on the outer surface of the blade

lay root and edge reinforcement materials, mainly unidirectional fabric materials

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place the sandwich structure with Barsa light wood core and fix it with small fasteners. Barsa light wood core is manually paved and fixed by workers

lay the internal biaxial fabric layer

vacuum infusion with vacuum bag and LM standard polyester resin

according to LM's proprietary operating specifications, the parts are cured at room temperature

after curing, the base shell is separated from the vacuum bag and ready to enter the next stage after inspection

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in the second stage, the main beam of hybrid composite blade is directly formed on the solidified base shell with the base shell as the mold:

the dry carbon glass hybrid unidirectional fabric layer is directly laid on the relatively flat center of the blade base shell along the length direction of the blade by the semi-automatic laying machine, from the position 4 meters away from the blade root

add light protective parts designed by LM

lay the ± 45 ° biaxial standard direction standard glass fiber coating at 200 yuan per square meter

vacuum bag and vacuum filling process are also adopted, and the filling conditions are accurately controlled, so that only the special resin is immersed in the hybrid fiber layer

according to LM's proprietary operating specifications, the main beam components are cured at room temperature

Lund laverick said, "we have the ability to scale up and apply the existing production technology to the ever lengthening fan blades. On these huge blade half shells, there is a slight pre bending along the length of the blades, while there is a little curling on both sides of the blades, but the central part is quite flat." In the flat area of each half shell, LM uses the semi-automatic equipment with internal design and computer control to lay the wide dry hybrid fiber fabric according to the laying method set by the program, so as to obtain the ideal strength performance

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due to the complex geometry of the curved blade edge, it is usually necessary to manually lay the layer

both the foundation shell and the hybrid main beam need equipment for laying. Since the carbon glass hybrid fabric is more sensitive than ordinary glass fiber fabric, LM has developed a manual laying technology to avoid wrinkles and other defects that may be introduced by manual operation

blade rib plate is a sandwich structure composed of glass fiber composite and foam core, which is mainly formed by pouring biaxial fabric layer and standard polyester resin

in terms of quality control, LM adopts the Six Sigma Lean management mode. Lund laverick said, "in the production process, we have a set of strict quality control documents and procedures, including continuous visual inspection of blades." After curing, ultrasonic inspection and visual inspection ensure the quality of products. Then, the two blade half shells are bonded together by conventional methods

After the two half shells are bonded together, LM uses a deflector to compensate for the relatively poor aerodynamic performance near the root of large blades. The deflector is specially designed for the geometric shape of individual blades, which is similar to fins. It is molded by injection process, and the VHb tape produced by Hexcel carbon fiber and composite 3M company is used in the final blade assembly process to adhere to the outer surface of the leeward half shell, usually extending from the position about 5m away from the blade root to the middle of the blade. This can reduce air separation (air separation occurs before reaching the trailing edge of the blade) and improve lift and energy output. In addition, LM will also use proprietary technology to customize the inner chord of the blade near the blade root to further improve the lift. It is usually produced by reaction injection molding (RIM) process

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at present, LM 88.4 P blades have passed the full-scale static mechanics and fatigue tests on LM's test platform and Denmark's independent blade Test Center (blaes reducer has the same type of reducer: helical gear reducer, planetary gear reducer, cycloid pin gear reducer, worm gear reducer, planetary friction mechanical stepless transmission, etc.), And has passed the certification of DNV GL Classification Society of Norway

the first set of commercial LM 88.4 P blades has been installed on adwen's next generation fan ad, with a rated power of 8mW and a rotor diameter of 180 meters. The three blades produced by LM are transported by truck and barge and installed by adwen. At present, they have been installed in Bremen port, Germany. Unfortunately, because adwen was acquired by gamesa, gamesa merged into Siemens, and the new Siemens gamesa renewable energy company canceled the ad platform, the product of this project has become a victim of industry integration

Lund laverick said that LM will continue to develop the carbon glass hybrid girder platform. At present, 69.3m blades are being delivered to Siemens gamesa. This is the largest onshore fan blade in the world at present. The blade still uses the same design, material and production specifications as the 88.4m blade, and will also use dry carbon glass hybrid fabric and resin system to obtain lower energy generation cost (lcoe). He added that at present, hybrid enhanced blades are mainly produced according to the needs of customers. In the future, with the continuous increase of blade length, LM will increase the number of blades produced by hybrid technology