Anti-icing and deicing method for fan blade based on composite material

Abstract

A fan blade anti-icing and deicing method based on a composite material comprises the following steps that epoxy resin and carbon fiber particles are selected to be evenly mixed and combined into the composite material; the surface of the fan blade is coated with a composite material, and a glass fiber reinforced plastic layer is formed after curing forming; fixing a plurality of piezoelectric sensors on the glass fiber reinforced plastic layer; the piezoelectric sensor is electrically connected with the signal generator and the data collector, and the data collector is electrically connected with the computer; a glass fiber reinforced plastic layer loop is conducted, set voltage is input, and the surface temperature of the glass fiber reinforced plastic layer rises to prevent icing; under the condition that the fan blade is iced, a glass fiber reinforced plastic layer loop is conducted, the surface temperature of the glass fiber reinforced plastic layer is gradually increased, the surface adhesive force of an ice layer and the glass fiber reinforced plastic layer is reduced, and the ice layer is separated from the fan blade by means of centrifugal force under the rotating action of the fan blade; blade icing is measured based on pressure stress waves, and anti-icing and deicing are actively carried out on the fan blade based on the continuous carbon fibers under the electric conduction effect.

Description

Technical Field

[0001] The invention belongs to the technical field of anti-icing and de-icing of fan blades, and relates to an anti-icing and de-icing method for fan blades based on composite materials. Background Art

[0002] Wind turbines in cold regions or high altitude areas often encounter icing climates during winter operation. Ice on wind turbine blades will significantly affect the aerodynamic performance of the blades, resulting in power production losses and mechanical failures caused by asymmetric loads due to increased icing, which may even lead to downtime. Therefore, how to ensure the normal operation of wind turbines installed in cold regions in winter icing climates is a key issue that needs to be solved at present.

[0003] Currently, there is a video monitoring method, which is to install a network camera on the wind turbine to monitor the blade icing condition. This method can provide effective icing information and monitor the blade surface in real time through video images. However, this method is only suitable for short-term monitoring, because visual monitoring must have sufficient visibility, and continuous monitoring at night requires artificial light, which is very costly. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method for anti-icing and de-icing of wind turbine blades based on composite materials, measuring blade icing based on compressive stress waves, and actively anti-icing and de-icing the wind turbine blades based on the conductive effect of continuous carbon fibers. In order to solve the above technical problems, the technical solution adopted by the present invention is: a wind turbine blade anti-icing and de-icing method based on composite materials, comprising the following steps: S1, material, epoxy resin and carbon fiber particles are uniformly mixed and combined into a composite material; S2, molding, coating the composite material on the surface of the wind turbine blade, and forming a fiberglass layer after curing and molding; S3, setting, fixing a plurality of piezoelectric sensors on the fiberglass layer; S4, connecting, the piezoelectric sensor is electrically connected to the signal generator and the data collector, and the data collector is electrically connected to the computer; S5, anti-icing, conduction FRP layer circuit, input set voltage, FRP layer surface temperature rises to prevent ice formation; S6, de-icing, when the fan blades are frozen, the FRP layer circuit is turned on, the surface temperature of the FRP layer gradually increases, the adhesion between the ice layer and the surface of the FRP layer decreases, and under the rotation of the fan blades, the ice layer is separated from the fan blades by centrifugal force.

[0005] In S2, the composite material uses a layer of continuous carbon fiber cloth and two layers of glass fiber cloth, and the continuous carbon fiber cloth is in contact with the surface of the wind turbine blade.

[0006] In S2, the continuous carbon fiber layer in the FRP layer is electrically connected to the wind turbine power generation system to form a loop, which is controlled by a controller to be turned on or off and the voltage is adjustable.

[0007] In S2, ignoring the heat loss, the heat generated by the carbon fiber electrification should be equal to the sum of the heat storage energy of the FRP blade heating, the heat absorbed by the ice heating and the heat absorbed by the ice melting into water; that is: ; In the formula, , , are the mass, specific heat and temperature rise of the FRP blade respectively; , , are the mass, specific heat and temperature rise of ice respectively; is the heating power, is the power-on time, The heat of melting of ice.

[0008] In S2, the resistance test of the fan blades is carried out. Beryllium copper electrodes with wires welded to them are attached to both ends of the carbon fiber cloth and conductive glue is applied around them. Then, the ends are insulated with epoxy resin. The two ends of the wires are directly connected to a DC power supply. Different input voltage values ​​are adjusted and the corresponding current is tested. The output current has a good linear relationship with the input voltage. The resistance value of the carbon fiber cloth of the fan blades is obtained through linear regression. When the resistance of each fan blade is known, ; In the formula, is the input voltage, is the ohmic resistance of the fan blade.

[0009] In S3, the piezoelectric sensor is pasted. After the piezoelectric sensor is pasted to the fiberglass layer, epoxy resin is used for waterproofing. When the piezoelectric sensor is elastically deformed by external force, it is longitudinally stretched or compressed, and the positive and negative charge centers inside the piezoelectric sensor move relative to each other, resulting in polarization, causing charges of opposite signs to appear on the two surfaces of the piezoelectric sensor. When the external force is removed, the piezoelectric element will return to its original uncharged state. This piezoelectric effect converts mechanical energy into electrical energy. The relationship between the reaction elastic variable and the electrical variable, under different mechanical boundary conditions and electrical boundary conditions, includes four types of piezoelectric equations.

[0010] In S3, the first type of piezoelectric equations of the four types are: stress T and electric field intensity E are selected as independent variables, electric displacement D and strain S are selected as dependent variables, electrical short circuit and mechanical freedom are selected as boundary conditions, and the corresponding piezoelectric equations are as follows: ; ; In the formula, is the dielectric constant; is the compliance coefficient; E represents the electric field intensity, which is equal to zero or a constant; d is the piezoelectric strain constant.

[0011] In S3, the second type of piezoelectric equations of the four types are: When strain S and electric field strength E are selected as independent variables, electric displacement D and stress T are selected as dependent variables, and electrical short circuit and mechanical clamping are selected as boundary conditions, the corresponding piezoelectric equation can be expressed as: ; ; In the formula, is the dielectric constant when the strain is constant; is the elastic stiffness coefficient under constant voltage; e is the piezoelectric stress constant.

[0012] In S3, the third type of piezoelectric equation is that when stress T and electric displacement D are selected as independent variables, strain S and electric field intensity E are selected as dependent variables, and mechanical freedom and electrical open circuit are selected as boundary conditions, the piezoelectric equation can be expressed as: ; ; In the formula, is the dielectric isolation ratio when the stress is constant, and is the dielectric constant The reciprocal of is the elastic compliance constant under constant electric displacement; g is the piezoelectric voltage coefficient.

[0013] In S3, the fourth type of piezoelectric equation is that when strain S and electric displacement D are used as independent variables and mechanical clamping and electrical open circuit are used as boundary conditions, the piezoelectric equation of the dependent variables electric field intensity E and stress T can be expressed as: ; ; In the formula, is the isolation ratio of the sandwiched medium, is the dielectric constant The reciprocal of is the open circuit elastic stiffness constant; h is the piezoelectric stiffness constant.

[0014] The main beneficial effects of the present invention are: By coating the surface of the iced area of ​​the wind turbine blades with a composite material based on continuous carbon fiber, the continuous carbon fiber layer is electrically connected to the wind turbine power generation system to form a circuit, which is then heated for anti-icing and de-icing, achieving the effect of active anti-icing and reducing costs.

[0015] When the wind blades are frozen, the passage between the continuous carbon fiber layer and the wind turbine power generation system is opened to form a water film between the fiberglass layer and the ice layer. The adhesion between the ice layer and the fiberglass layer is utilized, and the centrifugal force of the rotation of the wind blades is used to separate the ice layer from the wind blades. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0017] Figure 1 This is a partial layout diagram of the carbon fiber cloth of the present invention on the fan blade.

[0018] Figure 2 This is a diagram showing the layout of the piezoelectric sensor of the present invention on the fan blade.

[0019] Figure 3 This is a simplified control diagram of the electrical connection of the fan blades of the present invention.

[0020] Figure 4 This is a diagram showing the relationship between the voltage and current of the fan blades of the present invention.

[0021] Figure 5 This is a schematic diagram of the piezoelectric effect under pressure of the present invention.

[0022] Figure 6 This is a schematic diagram of the piezoelectric effect under tension of the present invention.

[0023] Figure 7 It is a schematic diagram of the internal deformation of the piezoelectric effect of the present invention.

[0024] Figure 8 It is a schematic diagram of external deformation of the piezoelectric effect of the present invention. DETAILED DESCRIPTION

[0025] like Figure 1 to Figure 8 A method for anti-icing and deicing wind turbine blades based on composite materials comprises the following steps: S1, material, epoxy resin and carbon fiber particles are uniformly mixed and combined into a composite material; S2, molding, coating the composite material on the surface of the wind turbine blade, and forming a fiberglass layer after curing and molding; S3, setting, fixing a plurality of piezoelectric sensors on the fiberglass layer; S4, connecting, the piezoelectric sensor is electrically connected to the signal generator and the data collector, and the data collector is electrically connected to the computer; S5, anti-icing, conduction FRP layer circuit, input set voltage, FRP layer surface temperature rises to prevent ice formation; S6, de-icing, when the fan blades are frozen, the FRP layer circuit is turned on, the surface temperature of the FRP layer gradually increases, the adhesion between the ice layer and the surface of the FRP layer decreases, and under the rotation of the fan blades, the ice layer is separated from the fan blades by centrifugal force.

[0026] In a preferred solution, in S2, the composite material uses a layer of continuous carbon fiber cloth and two layers of glass fiber cloth, and the continuous carbon fiber cloth is in contact with the surface of the wind turbine blade.

[0027] Preferably, in the composite material, each component still maintains its original properties, and after combination, it has the advantages of each material, with more complete comprehensive performance, forming an advanced composite material.

[0028] Preferably, carbon fiber composite materials, especially thermosetting resin-based carbon fiber composite materials, are easy to design and shape because of their high specific strength and specific modulus, good corrosion resistance, excellent electromagnetic properties and fatigue resistance.

[0029] In a preferred solution, in S2, the continuous carbon fiber layer in the FRP layer is electrically connected to the wind turbine power generation system to form a loop, which is controlled to be turned on or off by a controller and the voltage is adjustable.

[0030] Preferably, the carbon fiber resin matrix composite conductive mechanism composite material is a new type of material composed of multiple single materials to improve the performance of the material, or to meet special functional requirements on certain physical properties, wherein the dispersed phase is the reinforcement and the continuous phase is the matrix.

[0031] Preferably, epoxy resin is an oligomer with epoxy groups, which can form a solid with a three-dimensional network structure when reacting with a curing agent. As a kind of thermosetting resin, it has many advantages, such as active epoxy groups, hydrocarbon groups and ether groups in chemical structure, so it has strong bonding force, can firmly bond the reinforcing fibers together, and make it a whole that bears external force; it generates a three-dimensional network structure during the curing process, with high cross-linking density and small curing shrinkage, generally less than 2%; it has high strength, modulus and large elongation, which is beneficial to improving the mechanical properties of advanced composite materials; it is heat-resistant and cold-resistant, can be used in the range of -50~180°C, and has small thermal expansion, which is 39x106 / C below the glass transition temperature; it has good molding processability, strong adaptability, and relatively mature molding process; it has good chemical resistance and strong corrosion resistance.

[0032] From the above characteristics, it can be seen that epoxy resin does not have conductive properties, but because it is combined with conductive carbon fiber, the carbon fiber resin-based composite material also has conductive properties.

[0033] Preferably, the conductivity of carbon fiber is anisotropic, so the distribution of carbon fiber in the composite material determines the conductivity of the composite material. In the preferred solution, in S2, under the condition of ignoring heat loss, the heat generated by the carbon fiber when it is electrified should be equal to the sum of the heat storage energy of the fiberglass blade heating, the heat absorbed by the ice heating and the heat absorbed by the ice melting into water; that is: ; In the formula, , , are the mass, specific heat and temperature rise of the FRP blade respectively; , , are the mass, specific heat and temperature rise of ice respectively; is the heating power, is the power-on time, is the heat of melting of ice.

[0034] In the preferred solution, in S2, the resistance test of the fan blades is performed, beryllium copper electrodes with wires welded to them are attached to both ends of the carbon fiber cloth and conductive glue is applied around them, and then the ends are insulated with epoxy resin; the two ends of the wire are directly connected to a DC power supply, different input voltage values ​​are adjusted, and the corresponding current is tested. The output current has a good linear relationship with the input voltage, and the resistance value of the carbon fiber cloth of the fan blade is obtained by linear regression; when the resistance of each fan blade is known, ; In the formula, is the input voltage, is the ohmic resistance of the fan blade.

[0035] In the preferred scheme, in S3, the piezoelectric sensor is adhesive-type, and the piezoelectric sensor is pasted to the fiberglass layer and then coated with epoxy resin for waterproofing; when the piezoelectric sensor is subjected to external force and produces elastic deformation, longitudinal stretching or compression, the positive and negative charge centers inside the piezoelectric sensor move relative to each other, resulting in polarization, causing charges of opposite signs to appear on the two surfaces of the piezoelectric sensor; when the external force is removed, the piezoelectric element will return to its original uncharged state, and this piezoelectric effect converts mechanical energy into electrical energy; the relationship between the reaction elastic variable and the electrical variable, under different mechanical boundary conditions and electrical boundary conditions, includes four types of piezoelectric equations.

[0036] In the preferred solution, in S3, the first piezoelectric equation of the four types of piezoelectric equations is that stress T and electric field intensity E are selected as independent variables, electric displacement D and strain S are selected as dependent variables, electrical short circuit and mechanical freedom are selected as boundary conditions, and the corresponding piezoelectric equation is as follows: ; ; In the formula, is the dielectric constant; is the compliance coefficient; E represents the electric field intensity, which is equal to zero or a constant; d is the piezoelectric strain constant.

[0037] In the preferred solution, in S3, the second piezoelectric equation of the four types of piezoelectric equations is that when strain S and electric field intensity E are selected as independent variables, electric displacement D and stress T are selected as dependent variables, and electrical short circuit and mechanical clamping are selected as boundary conditions, the corresponding piezoelectric equation can be expressed as: ; ; In the formula, is the dielectric constant when the strain is constant; is the elastic stiffness coefficient under constant voltage; e is the piezoelectric stress constant.

[0038] In the preferred solution, in S3, the third piezoelectric equation of the four types of piezoelectric equations is that when stress T and electric displacement D are selected as independent variables, strain S and electric field intensity E are selected as dependent variables, and mechanical freedom and electrical open circuit are selected as boundary conditions, the piezoelectric equation can be expressed as: ; ; In the formula, is the dielectric isolation ratio when the stress is constant, and is the dielectric constant The reciprocal of is the elastic compliance constant under constant electric displacement; g is the piezoelectric voltage coefficient.

[0039] In the preferred solution, in S3, the fourth type of piezoelectric equation is that when strain S and electric displacement D are used as independent variables and mechanical clamping and electrical open circuit are used as boundary conditions, the piezoelectric equation of the dependent variables electric field intensity E and stress T can be expressed as: ; ; In the formula, is the isolation ratio of the sandwiched medium, is the dielectric constant The reciprocal of is the open circuit elastic stiffness constant; h is the piezoelectric stiffness constant.

[0040] Preferably, if Figure 3In the present invention, the anti-icing and de-icing monitoring device includes a plurality of piezoelectric sensors 2 arranged on a wind turbine blade 1, the piezoelectric sensor 2 is electrically connected to an access end of an electric slip ring 3, a signal generator 4 is electrically connected to an output end of the electric slip ring 3; a data acquisition device 5 is electrically connected to the signal generator 4 and a computer 6; the signal generator 4 amplifies the sensing signal of the piezoelectric sensor 2 and sends it to the computer 6 through the data acquisition device 5.

[0041] When in use, the electric slip ring 3 is installed between the fan base and the rotating hub. When the electric slip ring 3 rotates synchronously with the rotating hub, it still maintains electrical connection with the piezoelectric sensor 2 on the fan blade 1.

[0042] When ice crystals or ice is present on the fan blades 1 , the piezoelectric sensor 2 is compressed to generate a voltage difference, and the piezoelectric signal is amplified by the signal generator 4 and sent to the computer 6 through the data acquisition device 5 .

[0043] A plurality of piezoelectric sensors 2 are distributed on the surface of the wind turbine blade 1 in the area prone to ice formation. No matter which piezoelectric sensor 2 has a voltage change, it will be amplified by the signal generator 4 and collected by the data collector 5 .

[0044] The voltage threshold of each piezoelectric sensor 2 is preset. When the voltage threshold displayed by the computer 6 is greater than the preset voltage threshold, the computer 6 issues an instruction to start the de-icing program.

[0045] The above-mentioned embodiments are only preferred technical solutions of the present invention and should not be regarded as limitations of the present invention. The embodiments and features in the embodiments of the present application can be arbitrarily combined with each other without conflict. The protection scope of the present invention shall be the technical solutions recorded in the claims, including the equivalent replacement solutions of the technical features in the technical solutions recorded in the claims. That is, equivalent replacement improvements within this scope are also within the protection scope of the present invention.

Claims

1. A method for anti-icing and de-icing wind turbine blades based on composite materials, characterized in that: The steps include: S1, material, epoxy resin and carbon fiber particles are uniformly mixed and combined into a composite material; S2, molding, coating the composite material on the surface of the wind turbine blade, and forming a fiberglass layer after curing and molding; S3, setting, fixing a plurality of piezoelectric sensors on the fiberglass layer; S4, connecting, the piezoelectric sensor is electrically connected to the signal generator and the data collector, and the data collector is electrically connected to the computer; S5, anti-icing, conduction FRP layer circuit, input set voltage, FRP layer surface temperature rises to prevent ice formation; S6, de-icing, when the fan blades are frozen, the FRP layer circuit is turned on, the surface temperature of the FRP layer gradually increases, the adhesion between the ice layer and the surface of the FRP layer decreases, and under the rotation of the fan blades, the ice layer is separated from the fan blades by centrifugal force.

2. The anti-icing and de-icing method for wind turbine blades based on composite materials according to claim 1 is characterized by: In S2, the composite material uses a layer of continuous carbon fiber cloth and two layers of glass fiber cloth, and the continuous carbon fiber cloth is in contact with the surface of the wind turbine blade.

3. The anti-icing and de-icing method for wind turbine blades based on composite materials according to claim 1 is characterized by: In S2, the continuous carbon fiber layer in the FRP layer is electrically connected to the wind turbine power generation system to form a loop, which is controlled by a controller to be turned on or off and the voltage is adjustable.

4. The anti-icing and de-icing method for wind turbine blades based on composite materials according to claim 1 is characterized by: In S2, ignoring the heat loss, the heat generated by the carbon fiber electrification should be equal to the sum of the heat storage energy of the FRP blade heating, the heat absorbed by the ice heating and the heat absorbed by the ice melting into water; that is: ; In the formula, , , are the mass, specific heat and temperature rise of the FRP blade respectively; , , are the mass, specific heat and temperature rise of ice respectively; is the heating power, is the power-on time, is the heat of melting of ice.

5. The anti-icing and de-icing method for wind turbine blades based on composite materials according to claim 4 is characterized by: In S2, the resistance test of the fan blades is carried out. Beryllium copper electrodes with wires welded to them are attached to both ends of the carbon fiber cloth and conductive glue is applied around them. Then, the ends are insulated with epoxy resin. The two ends of the wires are directly connected to a DC power supply. Different input voltage values ​​are adjusted and the corresponding current is tested. The output current has a good linear relationship with the input voltage. The resistance value of the carbon fiber cloth of the fan blades is obtained through linear regression. When the resistance of each fan blade is known, ; In the formula, is the input voltage, is the ohmic resistance of the fan blade.

6. The anti-icing and de-icing method for wind turbine blades based on composite materials according to claim 1, characterized in that: In S3, the piezoelectric sensor is pasted. After the piezoelectric sensor is pasted to the fiberglass layer, epoxy resin is used for waterproofing. When the piezoelectric sensor is elastically deformed by external force, it is longitudinally stretched or compressed, and the positive and negative charge centers inside the piezoelectric sensor move relative to each other, resulting in polarization, causing charges of opposite signs to appear on the two surfaces of the piezoelectric sensor. When the external force is removed, the piezoelectric element will return to its original uncharged state. This piezoelectric effect converts mechanical energy into electrical energy. The relationship between the reaction elastic variable and the electrical variable, under different mechanical boundary conditions and electrical boundary conditions, includes four types of piezoelectric equations.

7. The anti-icing and de-icing method for wind turbine blades based on composite materials according to claim 6 is characterized by: In S3, the first type of piezoelectric equations of the four types are: stress T and electric field intensity E are selected as independent variables, electric displacement D and strain S are selected as dependent variables, electrical short circuit and mechanical freedom are selected as boundary conditions, and the corresponding piezoelectric equations are as follows: ； ； In the formula, is the dielectric constant; is the compliance coefficient; E represents the electric field intensity, which is equal to zero or a constant; d is the piezoelectric strain constant.

8. The anti-icing and de-icing method for wind turbine blades based on composite materials according to claim 6 is characterized by: In S3, the second type of piezoelectric equations of the four types are: When strain S and electric field strength E are selected as independent variables, electric displacement D and stress T are selected as dependent variables, and electrical short circuit and mechanical clamping are selected as boundary conditions, the corresponding piezoelectric equation can be expressed as: ； ； In the formula, is the dielectric constant when the strain is constant; is the elastic stiffness coefficient under constant voltage; e is the piezoelectric stress constant.

9. The anti-icing and de-icing method for wind turbine blades based on composite materials according to claim 6, characterized in that: In S3, the third type of piezoelectric equation is that when stress T and electric displacement D are selected as independent variables, strain S and electric field intensity E are selected as dependent variables, and mechanical freedom and electrical open circuit are selected as boundary conditions, the piezoelectric equation can be expressed as: ； ； In the formula, is the dielectric isolation ratio when the stress is constant, and is the dielectric constant The reciprocal of is the elastic compliance constant under constant electric displacement; g is the piezoelectric voltage coefficient.

10. The anti-icing and de-icing method for wind turbine blades based on composite materials according to claim 6, characterized in that: In S3, the fourth type of piezoelectric equation is that when strain S and electric displacement D are used as independent variables and mechanical clamping and electrical open circuit are used as boundary conditions, the piezoelectric equation of the dependent variables electric field intensity E and stress T can be expressed as: ； ； In the formula, is the isolation ratio of the sandwiched medium, is the dielectric constant The reciprocal of is the open circuit elastic stiffness constant; h is the piezoelectric stiffness constant.

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