Design and arrangement method of blade inner cavity microwave radiation antenna

Abstract

The invention discloses a design and arrangement method of a blade inner cavity microwave radiation antenna, and belongs to the field of microwave radiation deicing. According to the high-power horn pyramid antenna, the microwave radiation coverage of the middle-rear section area of the blade is ensured, the rod-shaped antennas with omnidirectional radiation capability are arranged at the front edge of the blade, and 2-4 pairs of rod-shaped antennas focus on covering the seriously frozen area at the front edge, so that the directional radiation of microwave energy is realized; the silicon carbide / graphite / polyurethane composite wave-absorbing coating absorbs microwave energy and converts the microwave energy into heat energy, and efficient deicing of the blade is achieved. The antenna is flexible in layout, can be adjusted according to different spatial characteristics of the inner cavity of the blade, is suitable for various application scenes, and has wide adaptability. The antenna is structurally designed, and miniaturization of the microwave radiation antenna is achieved. Through reasonable layout of the microwave radiation antenna, efficient directional radiation of microwave energy is realized.

Description

Technical Field

[0001] The invention relates to the field of microwave radiation deicing, and in particular to a method for designing and arranging a microwave radiation antenna in a blade cavity. Background Art

[0002] As a clean and renewable energy source, wind energy has been widely used and developed. However, in cold climates, wind turbine blades are prone to icing, which leads to reduced wind energy conversion efficiency, unstable operation, and increased risk of equipment damage. Therefore, in order to improve the reliability and economy of wind farms, wind turbine blade deicing technology has become the focus of research and attention.

[0003] At present, common wind turbine blade deicing methods include mechanical deicing, heating deicing and chemical deicing. However, traditional mechanical deicing requires additional equipment and manual operation, which is costly and inefficient. The heating deicing method mainly uses electric heating or heating medium for heating, but there are problems of high energy consumption and complex operation. Chemical deicing requires the use of chemical substances, which pollutes the environment.

[0004] In order to overcome the limitations of traditional deicing methods, microwave radiation deicing technology came into being. Microwave radiation deicing uses microwave energy to heat the blade surface, absorbs microwave energy, quickly melts ice and snow and prevents new ice and snow from forming. Compared with traditional methods, microwave radiation deicing has the advantages of low energy consumption, high efficiency and environmental protection.

[0005] However, the existing microwave radiation deicing technology still faces some challenges. Among them, the design of effective blade cavity radiation antenna and layout issues need to be solved urgently. Therefore, the present invention provides a blade cavity microwave radiation antenna design and layout method, which achieves efficient and low energy consumption wind turbine blade deicing effect through reasonable design of microwave radiation antenna and layout method. Summary of the invention

[0006] In order to solve the above problems, the present invention provides a design and arrangement method for an inner cavity microwave radiation antenna applied to a wind turbine blade.

[0007] The technical solution of the present invention is as follows:

[0008] A method for designing and arranging a blade cavity microwave radiation antenna, the steps are as follows:

[0009] The first step is to give the technical indicators and working principles of the antenna design; the technical indicators include operating frequency, gain and polarization mode.

[0010] The second step is to select the most suitable antenna type based on the technical indicators of the antenna and the spatial characteristics of different positions in the blade cavity.

[0011] (1) Selection of antenna type for the blade root area:

[0012] The blade root area has a large space and light icing. The antenna gain at the blade root is not less than 15dB, so a pyramidal horn antenna is chosen.

[0013] (2) Selection of antenna type for the leading edge of the blade:

[0014] The space at the leading edge of the blade is long and narrow, and ice is severe. The gain of the antenna placed at the leading edge of the blade should not be less than 5dB. A rod antenna, that is, a vertical rod-shaped dielectric antenna, is chosen.

[0015] Furthermore, the length of the rod antenna is 1 / 4 or 1 / 2 of the central wavelength, and it has omnidirectional radiation performance, and can cover the 360-degree icing area in the longitudinal direction.

[0016] The third step is to design the antenna structure based on the antenna selection and combined with simulation calculations.

[0017] 3.1 Pyramidal horn antenna structure design: The horn part is in the shape of a cone, which gradually expands outward from the opening of the waveguide. The waveguide size is first determined according to the operating frequency and gain. Combined with simulation calculations, the design size of the pyramidal horn antenna is given. The larger the horn mouth, the higher the gain and the narrower the beam.

[0018] 3.2 Rod antenna structure design: The rod antenna radiates signals uniformly 360 degrees in the horizontal direction. The design dimensions of the rod antenna are given based on the operating frequency and combined with simulation calculations.

[0019] The fourth step is antenna layout design: according to the icing conditions in different areas of the blade and the size of the inner cavity, a high-power horn antenna is arranged at the root of the blade, and 2-4 rod-shaped dielectric antennas are arranged at the leading edge of the blade. Under the pre-layout of the antenna, the coupling degree between the antennas is analyzed to ensure that multiple antennas do not interfere with each other.

[0020] Furthermore, the specific operations for ensuring that multiple antennas do not interfere with each other in step 4 are as follows:

[0021] After the antenna types in each area are determined, a large number of antennas are placed in sequence while ensuring good isolation between antennas. According to the requirements of electromagnetic compatibility design, multiple antennas placed in the same blade cavity must have strong compatibility to prevent interference. The basic requirement is that the coupling between antennas is less than -15dB.

[0022] Furthermore, the radiating antenna is arranged at the root of the blade and 30% of the leading edge of the blade, and is led out through a high-power cable to receive and transmit microwave energy in a directionally manner.

[0023] The present invention realizes the design and arrangement method of microwave radiation antenna in the inner cavity of fan blades. The high-power horn pyramid antenna ensures the microwave radiation coverage of the middle and rear areas of the blades. The rod antenna with omnidirectional radiation capability is placed on the leading edge of the blades. 2-4 rod antennas focus on covering the leading edge area with severe icing, realizing directional radiation of microwave energy. The silicon carbide / graphite / polyurethane composite absorbing coating absorbs microwave energy and converts it into heat energy, realizing efficient deicing of the blades.

[0024] The advantages of the present invention include but are not limited to:

[0025] 1. Adaptability: The antenna layout of the present invention is flexible and can be adjusted according to the different spatial characteristics of the blade cavity. It is suitable for a variety of application scenarios and has wide adaptability.

[0026] 2. Miniaturization: Structural design of the antenna to achieve miniaturization of the microwave radiation antenna.

[0027] 3. High efficiency: Through the reasonable layout of microwave radiation antennas, efficient directional radiation of microwave energy is achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a flow chart of the design and arrangement method of microwave radiation antenna in blade cavity;

[0029] Figure 2 This is the front view of the size and structure of the pyramidal horn antenna;

[0030] Figure 3 This is the side view of the dimensions and structure of the pyramidal horn antenna;

[0031] Figure 4 is the standing wave ratio of the pyramidal horn antenna;

[0032] Figure 5 is the far-field pattern of the pyramidal horn antenna;

[0033] Figure 6 This is the front view of the size and structure of the rod antenna;

[0034] Figure 7 This is a side view of the dimensions and structure of the rod antenna;

[0035] Figure 8 is the standing wave ratio of the rod antenna;

[0036] Fig. 9 is the directional pattern of the rod antenna;

[0037] Fig.10 Schematic diagram of radiating antenna isolation

[0038] Fig.11 It is a schematic diagram of the radiating antenna arrangement. DETAILED DESCRIPTION

[0039] In order to make the purpose, technology and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and examples.

[0040] Taking a 40m long wind turbine blade as an example, the following is the specific implementation process:

[0041] 1. Give the technical specifications of antenna design (including frequency, gain and polarization) and working principle

[0042] (1) Technical indicators

[0043] In order to avoid interference with communications, the International Radio Regulatory Committee stipulates that the frequencies used for industrial microwave heating are 915MHz and 2.45GHz, with 915MHz allocated to North and South America and 2.45GHz being universal worldwide. The corresponding wavelength is 122mm.

[0044] At a frequency of 2.45GHz, the gain of the pyramidal horn antenna can reach 10-20dB, the power capacity is 1kW, the polarization is linear polarization, and the standing wave ratio is ≤1.5; the gain of the rod antenna is smaller, generally 5-8dB, the power capacity is up to 500W, the polarization is linear polarization, and the standing wave ratio is ≤1.5.

[0045] (2) Working principle

[0046] Working principle of antenna: Microwave radiation antenna converts electrical signals into electromagnetic waves for radiation (transmission), or converts received electromagnetic waves into electrical signals. When current passes through the antenna, an electromagnetic field is formed around the antenna. This electromagnetic field propagates at the speed of light in space, forming electromagnetic waves. The antenna converts the electromagnetic field into electromagnetic waves with specific directionality and intensity for radiation according to the designed frequency.

[0047] Horn antenna: The electrical signal enters the waveguide from the feeding system. The electromagnetic waves in the waveguide are usually TE mode or TM mode, propagating in the waveguide. The waveguide effectively guides the electromagnetic waves to the horn part and controls its propagation mode and phase distribution. The electromagnetic waves are radiated into the free space through the opening of the horn. As the horn gradually expands, the radiated electromagnetic waves have a certain directionality and are concentrated in the direction of the horn opening, forming a high-gain radiation mode.

[0048] Rod-shaped dielectric antenna: A circular dielectric resonator is loaded around the monopole antenna, and the feeding method adopts the back feeding of the coaxial line. The size of the monopole oscillator and the circular dielectric resonator is adjusted to match the input impedance of the antenna. The electrical signal is fed into the bottom of the antenna through the feeder (such as the coaxial cable), and the current flows on the metal conductor (the oscillator of the rod-shaped dielectric antenna), generating a corresponding electromagnetic field. The antenna will radiate in the vertical direction and has omnidirectional radiation characteristics in the horizontal direction.

[0049] 2. Select the most suitable antenna type based on the antenna's technical specifications and the spatial characteristics of different locations in the blade cavity.

[0050] (1) Selection of antenna type for the blade root area:

[0051] The blade root area has a large space, and the icing phenomenon is slight, the aerodynamic efficiency is low, and the antenna gain at the blade root is not less than 15dB. The pyramid horn antenna is selected. The horn antenna has a simple structure, high gain, and large power capacity. The emitted electromagnetic waves can cover most of the icing area. The pyramid horn antenna is formed by gradually unfolding the feeding waveguide at a certain angle. The gradual expansion of the waveguide mouth improves the matching between the waveguide and the free space, making the reflection coefficient smaller and the gain higher.

[0052] (2) Selection of antenna type for the leading edge of the blade:

[0053] The space at the leading edge of the blade is long and narrow, and icing is more serious. The gain of the antenna placed at the leading edge of the blade is not less than 5dB. A rod antenna is chosen, that is, a vertical rod antenna with a length of generally 1 / 4 or 1 / 2 the center wavelength. It has omnidirectional radiation performance and can cover 360 degrees of the icing area along the longitudinal direction. It has a simple structure and low manufacturing cost, but low gain.

[0054] 3. Based on the antenna selection and combined with simulation calculations, the antenna structure is designed to meet technical requirements such as miniaturization and high power.

[0055] 3.1 Design of pyramidal horn antenna: The waveguide is a structure that connects the feed source and the horn part. It transmits electromagnetic waves and provides the initial propagation mode. The size of the waveguide is usually related to the operating frequency. According to the center frequency of 2.45GHz and the gain requirement of more than 15dB, first select a suitable waveguide. The shape of the horn part is pyramidal (i.e., a quadrangular pyramid), which gradually expands outward from the opening of the waveguide. First determine the size of the waveguide according to the operating frequency and gain. The shape and size of the horn determine the radiation characteristics of the antenna. It is the radiation outlet of the electromagnetic wave and directly affects the gain and beam width of the antenna. The larger the horn mouth, the higher the gain and the narrower the beam. According to the waveguide size, operating frequency and gain requirements, design the aperture size and horn length of the rectangular horn.

[0056] 3.2 Use the three-dimensional electromagnetic field simulation software CST2021 version to obtain the final size, such as Figure 2 , Figure 3 As shown, the standing wave ratio and directivity diagram are as follows Figure 4 , Figure 5 As shown, the standing wave ratio is <1.5 and the gain is 16dB.

[0057] 3.3 Rod antenna structure design: Rod dielectric antenna is a vertically polarized antenna, which radiates electromagnetic waves to the surrounding space through the current distribution formed by standing waves on the conductor. Rod antennas usually have omnidirectional radiation characteristics, that is, they radiate signals uniformly 360 degrees in the horizontal direction, and the gain is generally 3-6dB. According to the center frequency of 2.45GHz, the dielectric material is glass fiber reinforced plastic with a dielectric constant of 4.

[0058] 3.4 Use the 3D electromagnetic field simulation software CST2021 to optimize the final size as shown in the front view Figure 6 and side view Figure 7 As shown, the length is 645mm, the diameter is 20mm, and the standing wave is Figure 8 As shown, at 2.45GHz the standing wave ratio is 1.3, and the radiation pattern is as follows Fig. 9 As shown, 360-degree omnidirectional radiation is basically achieved, and the peak gain is 6.93dB.

[0059] 4. Antenna layout design

[0060] 4.1 According to the icing conditions in different areas of the blade and the size of the inner cavity, a high-power horn antenna is arranged at the root of the blade, and 2-4 rod antennas are arranged at the leading edge of the blade. Under the pre-arrangement of the antenna, the coupling degree between the antennas is analyzed to ensure that multiple antennas do not interfere with each other.

[0061] 4.2 The microwave source is arranged at the root of the blade, and the power supply is provided by modifying the blade slip ring. A 3kW pyramidal horn antenna is arranged at the root of the blade, and is directly connected to the magnetron microwave source through a waveguide. At 30% of the leading edge of the blade, that is, 30 meters away from the blade root, 2-4 rod-shaped dielectric antennas are arranged, and connected to the microwave source at the root of the blade through high-power cables, waveguide coaxial conversion and high-power power distributors.

[0062] 4.3 According to the requirements of electromagnetic compatibility of antennas, ensure that multiple antennas placed on the same blade have strong compatibility to prevent interference. The basic requirement is that the antenna coupling degree is ≤-15dB. In engineering, the requirement can be met by a distance of about 0.5-1 wavelength.

[0063] 4.4 The spacing of the leading edge rod antenna is 80 mm, which is greater than 1 / 2 wavelength. The coupling degree of the antenna layout is obtained using the three-dimensional electromagnetic field simulation software CST2021. Fig.10 , the coupling degree between the rod-shaped dielectric antennas is -24.5dB, which meets the requirement of <-15dB at 2.45GHz; when the actual distance between the horn antenna and the rod-shaped dielectric antenna is ≥10m, the coupling degree is -156.8dB, which means there is basically no coupling. The layout method is as follows Fig.11 shown.

[0064] The design and arrangement method of the blade cavity microwave radiation antenna of the present invention can be widely used in wind farms to effectively solve the icing problem of wind turbine blades in cold climate conditions. By rationally arranging the microwave heating system and the radiation antenna in the blade cavity, the microwave energy can fully cover the blade surface, and cooperate with the microwave absorbing coating to heat up, achieving a comprehensive anti-icing and de-icing effect.

Claims

1. A method for designing and arranging a blade cavity microwave radiation antenna, characterized in that: Here are the steps: The first step is to give the technical indicators and working principle of the antenna design; the technical indicators include operating frequency, gain and polarization mode; The second step is to select the most suitable antenna type based on the antenna's technical specifications and the spatial characteristics of different locations in the blade cavity; (2.1) Selection of antenna type for blade root area: The blade root area has a large space and light icing. The antenna gain at the blade root is not less than 15dB, so a pyramidal horn antenna is chosen. (2.2) Selection of antenna type for the leading edge of the blade: The leading edge of the blade has a long and narrow space and severe icing. The gain of the antenna placed on the leading edge of the blade should not be less than 5dB. Therefore, a rod antenna, i.e. a vertical rod-shaped dielectric antenna, is chosen. The third step is to design the antenna structure based on the antenna selection and combined with simulation calculation; (3.1) Pyramidal horn antenna structure design: The horn part is in the shape of a cone, which gradually expands outward from the opening of the waveguide. The waveguide size is first determined based on the operating frequency and gain. The design size of the pyramidal horn antenna is given in combination with simulation calculations. The larger the horn mouth, the higher the gain and the narrower the beam. (3.2) Rod antenna structure design: The rod antenna radiates signals uniformly 360 degrees in the horizontal direction. The design dimensions of the rod antenna are given according to the operating frequency and combined with simulation calculations; The fourth step is antenna layout design: according to the icing conditions in different areas of the blade and the size of the inner cavity, a high-power horn antenna is arranged at the root of the blade, and 2-4 rod-shaped dielectric antennas are arranged at the leading edge of the blade. Under the pre-layout of the antenna, the coupling degree between the antennas is analyzed to ensure that multiple antennas do not interfere with each other.

2. The method for designing and arranging a blade cavity microwave radiation antenna according to claim 1, characterized in that: In the second step, the length of the rod antenna is 1 / 4 or 1 / 2 of the central wavelength, and it has omnidirectional radiation performance and can cover the 360-degree icing area in the longitudinal direction.

3. The method for designing and arranging a blade cavity microwave radiation antenna according to claim 1, characterized in that: The specific operations for ensuring that multiple antennas do not interfere with each other in step 4 are as follows: After the antenna types in each area are determined, a large number of antennas are placed in sequence while ensuring good isolation between antennas; according to the requirements of electromagnetic compatibility design, multiple antennas placed in the same blade cavity are ensured to have strong compatibility to prevent interference; The basic requirement is that the coupling between antennas is less than -15dB.

4. The method for designing and arranging a blade cavity microwave radiation antenna according to claim 1, characterized in that: In the fourth step, the radiating antenna is arranged at the root of the blade and 30% of the leading edge of the blade; it is led out through a high-power cable to receive and directionally transmit microwave energy.

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