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About Wind Turbine Blade

Wind Turbine Blade
Wind turbine blade is the most basic and key components of the wind turbine, the design of the blade in the wind turbine directly affects the conversion efficiency of wind energy, directly affect its annual power generation, is an important part of wind energy utilization.

wind turbine blade design

1.Blade shape design
Blade aerodynamic design main shape optimization design, which is the blade design in the crucial step. Shape optimization design in the blade airfoil design directly determine the fan power generation efficiency, in the wind turbine operating conditions, the flow of the Reynolds number is relatively low, blade usually in low speed, high lift coefficient state operation, blade flow interference between the blades caused by flow is very complex. For the blade shape of the complex flow state and blade by the blade in different directions of the distribution of the composition, the blade leaf shape design becomes very important.
At present,the blade design technology usually adopts the advanced airplane wing design method to design the blade shape.Advanced CFD techniques have been widely used in the design of different types of aerodynamic shapes. For the operating conditions of wind turbine with low Reynolds number and high lift coefficients, it is essential to analyze the flow field of the blade  shape by using the N-S control equation considering viscosity.

Wind Turbine Blade manufacturing
Wind Turbine Blade manufacturing

2.Structure design

The current structure of large wind turbine blades are in the form of skin main beam. The skin is mainly reinforced by biaxial composite layers, which provide aerodynamic shape and bear most of the shear load. The trailing edge cavity is wider and the sandwich structure is used to improve its anti-destabilization ability. The main beam is mainly reinforced by unidirectional composite layers, which is the main load-bearing structure of the blade. The web is a sandwich structure, which provides support to the main beam.
Blade force analysis: the blade to bear the thrust drive blade rotation. The distribution of thrust is not uniform but proportional distribution with the blade length. The tip of the leaf to bear the thrust is greater than the root of the blade.
Beam design: due to the blade self-weight and external thrust generated by the bending deformation is the blade of the most important load, in order to improve the bending performance, in the blade length direction using a one-way fiber cloth, and the middle through the shear web will be the upper and lower two layers of beam cap as far as possible to separate, shear web using diagonally laid two-way fiber cloth plus foam (PET) core material composition, to increase the overall rigidity of the role.
Internal beam structure: in order to reduce production costs, the design can remove some unnecessary materials, common blade are hollow design.
Blade casing: The role of the blade casing is primarily to provide an aerodynamic profile. Rigidity is increased by the sandwich structure of the blade casing, which consists of a FRP surface layer with a PET core or a BALTEK core. The core structure is rigid enough to withstand bending loads and prevent debonding. The diagonally distributed fibers in the leaf shell provide the necessary torsional rigidity.
Blade root design: The blade root section is usually designed as a circle. At the same time, in order to meet the needs of maintenance and other needs, the blade root is mostly bolted to facilitate disassembly and assembly. For the metal beam can be used welded flange connection.

3.Why do wind turbines need only three blades?

The more blades a wind turbine has, the more wind volume it can intercept, but at the same time it also makes the wind speed through the blades lower. After calculation, the efficiency of the blades there is an optimal value, three blades turbine in the higher level. With the increase in the number of blades, efficiency does have to rise, but 3-4 blades to improve the magnitude than 2-3 blades to improve the magnitude is much smaller. And the increase in the number of blades, corresponding to the cost is also on the rise.
So a comprehensive consideration of many factors, three blades than four blades; and the reason why not use two blades, to a large extent, from the structural considerations: two blades in the rotation, it is very easy to form a rotation imbalance, causing a large dynamic load. To sum up, wind turbine choose three blades is the best result under the consideration of various factors.

Wind turbine blade material

Wind turbine blade accounts for about 15%-20% of the total cost of the fan, the current large wind turbine blade is basically composed of composite materials, composite material content is usually more than 80%. According to statistics, the fan blade size of each increase of 6%, the capture of wind energy can increase by 12%.
Fiberglass reinforced plastic, abbreviated as GFRP, is a reinforced plastic made of epoxy resin, unsaturated resin and other plastics infiltrated with glass fiber or carbon fiber of different lengths. Reinforced plastic high strength, light weight, aging resistance, the surface can be wrapped glass fiber and epoxy resin, other parts of the filling foam. The main role of foam in the blade is to ensure its stability while reducing the quality of the blade, so that the blade in meeting the stiffness at the same time to increase the wind catching area.
1.For the blade, stiffness is a very important indicator, at present, GFRP is the most commonly used composite material for modern wind turbine blade, research shows that the carbon fiber composite blade stiffness is 2-3 times of GFRP in line with the blade. Although the performance of carbon fiber composite material is greatly superior to the glass fiber composite material, but the price is expensive, affecting it in the wind power large scale application.
And with the blade gradually become larger, wind turbine diameter has broken through 120m, the longest blade has done 61.5m, blade from the weight of 18t. Whole GFRP blade has been unable to meet the blade large-scale, lightweight requirements. So the advantages of the two combined, the main body using GFRP, carbon fiber or other high-strength fibers are more applied to the blade local area, to achieve maximum benefit.

Wind Turbine Blade Installation
Wind Turbine Blade Installation

2.Wind turbine blade on the material requirements
The blade is the most basic and critical part of wind turbine, its good design, reliable quality and superior performance are the decisive factors to ensure the normal and stable operation of the unit. In order to ensure long-term non-stop and safe operation in the field and its harsh environment, the requirements for blade materials are:
(1) light density and has the best fatigue strength and mechanical properties, can withstand extreme harsh conditions such as windstorm and random load test.
(2) blade elasticity, rotational inertia and its vibration frequency characteristic curve are normal, transfer to the whole power generation system load stability is good, shall not be in the case of loss of control (flying car) download centrifugal force under the action of pull off and fly out, also shall not be in the role of wind pressure under this section, also shall not be in the flying car speed below the range caused by the whole wind turbine strong resonance.
(3) the blade material must ensure that the surface is smooth to reduce wind resistance, rough surface will also be torn by the wind.
(4) shall not produce strong electromagnetic wave interference and light reflection.
(5) does not allow the generation of large noise.
(6) good resistance to corrosion, ultraviolet radiation and lightning strike performance.
(7) Lower cost and lowest maintenance cost.

Boland/CRRC adopt blades with excellent aerodynamic performance and integrate many advanced control technologies to significantly improve power generation performance. Among them, WT2000/WT2500 models have larger unit kW area than conventional models. WT4000+/WT5000+ units are even capable of blade length and power level series design, providing customized wind farm solutions; single blade lifting + split lifting customized solutions. CRRC with wind products the sales of wind turbine generator ranked first in China, blade sales ranked second in China, tower sales ranked third in China .

About wind turbine blade length depends on the design power of the wind turbine, and wind farm conditions. The same wind farm, the higher the power blade longer. The same power, the annual average wind speed of the lower wind field need longer blade. In fact, according to research, different wind farm, need to match the corresponding power wind turbine, in order to achieve the real cost performance. In addition: the same length of the blade, due to differences in wing shape, power is not the same.

CRRC wind turbine blade factory
CRRC wind turbine blade factory
CRRC wind turbine blade factory
CRRC wind turbine blade factory

Boland Renewable Energy Co.,LTD As an integrated new energy power company, providing youwith high quality integrated wind energy , solar energy and energy storage system solutions.Boland is now a subsidiary of CRRC, and is responsible for the overseas expansion of CRRC's wind power & solar power business. We have a relatively complete internal supply chain, service network and excellent product quality and technology.

Boland Provide power plant EPC,Power plant investment and acquisition.

Please feel free contact us if you need any technical support.Cheers for our cooperation!



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