A fan blade air-heat deicing system

Abstract

The present invention discloses a fan blade air-heat deicing system, which includes a heater and a blower installed in the blade, wherein the air inlet of the heater is connected to the air outlet of the blower, the air outlet of the heater is connected to the air inlet of an air duct, the air outlet of the air duct points to the direction of the blade tip, the front end of the air duct adopts a hard air duct, and the rear end of the air duct adopts a soft air duct, the air inlet of the hard air duct is connected to the air outlet of the heater, the air outlet of the hard air duct is connected to the air inlet of the soft air duct, the soft air duct is arranged in the blade leading edge cavity, and the soft air duct is provided with a plurality of air guide holes at the position toward the blade leading edge. When there is no hot air, the soft air duct shrinks, and when there is hot air, the soft air duct extends to the blade tip or the blade tip is blocked. The present invention can extend the air duct to the blade tip, thereby enhancing the deicing effect of the blade tip, and can also construct a new hot air return channel in the blade with blade tip blockage to achieve the air-heat deicing effect.

Description

Technical Field

[0001] The invention relates to deicing of blades of a wind turbine generator set, and in particular to an air-heat deicing system for fan blades. Background Art

[0002] At present, wind turbines located in mountainous areas in the north and south are faced with the problem of being unable to generate electricity in winter due to ice covering the blades: since there is no effective means to remove the ice after the blades are covered, they can only wait for the ice to melt naturally when the weather warms up, resulting in huge losses in power generation. The ice also has a serious impact on the safety, service life and maintenance costs of the units, poses a safety hazard to surrounding people, livestock and equipment, and has an impact on the stable operation of the power grid, exacerbating the contradiction between electricity consumption and power generation during the freezing period.

[0003] Gas-heat deicing is a relatively mature method for de-icing blades of wind turbines. It can be used for the modification of existing wind turbines and the installation of new wind turbines. It has a long service life, is easy to maintain, will not attract lightning, and has a certain anti-icing ability. The principle of gas-heat deicing is: the inside of the blade is a closed cavity, and a blower and a heater are installed in the blade cavity. The heater heats the cold air in the blade, and then the blower sends the heated hot air out, which circulates along the air duct designed in the blade. The hot air heats the inner surface of the blade, and the heat is transferred from the inner surface of the blade to the outer surface of the blade. When the temperature of the outer surface of the blade exceeds zero degrees, the anti-icing and de-icing effect can be achieved. When designing specifically, if Figure 1 、 Figure 2 As shown, the heater 1 and the blower 2 are installed in the manhole baffle at the root of the blade 14. The air outlet of the heater 1 sends the hot air to a place about one-third of the blade length away from the blade root through the air duct 3. Because the space of the leading edge cavity 7 of the blade further forward is narrow, the air duct 3 cannot be constructed, and a baffle 4 is installed here so that the hot air flowing out of the air duct 3 is blocked by the baffle 4 and cannot flow back. It can only move from the leading edge cavity 7 of the blade to the tip 5, and then flow back through the process hole set at the tip 5 through the web cavity 6 and the trailing edge cavity 11 of the blade into the air inlet of the blower 2 to form a hot air circulation channel.

[0004] When ice accumulates on blades, the blade's shape is altered, disrupting the blade's original lifting body structure. This significantly reduces the blade's wind-catching ability. Furthermore, ice accumulation increases blade weight and wind resistance, making it difficult for the blade to reach its theoretical rotational speed, leading to a sharp drop in wind turbine power generation and even shutdown. The leading edge 10, facing the wind, is most significantly impacted by the lifting body structure. Because the closer to the blade tip, the greater the moment of inertia of ice accumulation, the greater the impact on the blade. Therefore, de-icing should prioritize the leading edge 10, with de-icing being more important the closer the leading edge 10 is to the blade tip 5. In order to achieve better air-heat deicing effect and reduce self-consumption of electricity, it is necessary to consider that the heat of the heater 1 is used first to the position of the blade leading edge cavity 7 near the blade tip 5 during design. To this end, the air-heat deicing system uses the air duct 3 to send hot air to the blade tip 5 along the blade web 9 of the blade leading edge cavity 7. However: First, because the closer the blade leading edge cavity 7 is to the blade tip 5, the smaller the cross-sectional area is, when constructing on the existing fan blade, the workers often cannot move forward to the position where the blade is one-third of the blade length away from the blade root (at the baffle 4), and the air duct 3 can only be arranged here; second, the hot air comes out of the heater 1 to the blade tip 5, and the further forward it is, the less heat is generated. The less, the lower the temperature, the worse the de-icing effect, which is exactly the opposite of the actual need; thirdly, the blade tips of some blades are blocked, and the hot air cannot flow from the blade tip process hole to the blade trailing edge cavity 11 and the web cavity 6 between the two webs, that is, a hot air circulation channel cannot be formed, and the hot air cannot circulate, resulting in the heat of the heater 1 cannot be delivered, and the de-icing function fails. The current method to repair blades with blocked blade tips is to open a skylight at the blade tip 5, forcibly punch a hole with a drill to form a hot air circulation channel, and then seal the skylight. This is not only time-consuming and labor-intensive, but also the blade factory and the owner are worried that the blades will be damaged due to the immature skylight technology. Summary of the Invention

[0005] One of the technical problems to be solved by the present invention is that, in view of the deficiency that the air duct in the existing fan blade air thermal deicing system cannot deliver hot air to a position close to the blade tip, the present invention provides a fan blade air thermal deicing system that can extend the air duct to the blade tip to enhance the deicing effect of the blade tip.

[0006] The second technical problem to be solved by the present invention is that, for blades with blocked blade tips, the present invention provides a fan blade air-heat deicing system that can form a new hot air flow circulation channel in the blade leading edge cavity to solve the problem of interruption of the hot air flow circulation channel for air-heat deicing after the blade tip is blocked.

[0007] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0008] A fan blade air heating deicing system includes a heater installed in the blade and a blower. The air inlet of the heater is connected to the air outlet of the blower, and the air outlet of the heater is connected to the air inlet of an air duct. The air outlet of the air duct points toward the blade tip. The hot air blown out of the air duct is blown toward the blade tip and then enters the air inlet of the blower through a hot air return channel. The structural features of the system are as follows:

[0009] The front end of the air duct is a hard air duct, and the rear end of the air duct is a soft air duct. The air inlet of the hard air duct is connected to the air outlet of the heater, and the air outlet of the hard air duct is connected to the air inlet of the soft air duct.

[0010] The inner cavity of the blade is divided by the blade web into a blade leading edge cavity facing the windward side of the blade and a blade trailing edge cavity facing the leeward side of the blade;

[0011] The soft air duct is arranged in the leading edge cavity of the blade, and a plurality of air guide holes are opened on the side of the soft air duct facing the windward side of the blade. When there is no hot air, the soft air duct shrinks, and when there is hot air, the soft air duct extends to near the tip of the blade.

[0012] Preferably, the size and density of the air guide holes on the flexible air duct are determined based on the heat required for de-icing at that location. Generally, the closer the air guide holes on the flexible air duct are to the blade tips, the larger their diameter and density.

[0013] Preferably, the cross-sectional area of ​​the flexible air duct becomes smaller as it gets closer to the blade tip, so as to maintain sufficient wind pressure and push the hot air flow toward the blade tip.

[0014] Preferably, the rigid air duct is mounted on the blade web, and a baffle is mounted between the blade web and the blade leading edge, and the air outlet of the rigid air duct passes through the baffle.

[0015] Preferably, when the blade tip is blocked, a plurality of hot air return holes are provided on the baffle to form a return air duct between the blade web and the blade leading edge.

[0016] Preferably, the diameter of the hot air return hole is smaller than the diameter of the soft air duct.

[0017] Preferably, the connection between the soft air duct and the hard air duct is fixed with a clamp.

[0018] Preferably, the flexible air duct is an air distribution duct.

[0019] Principle of the design method of the present invention:

[0020] 1) With the characteristics of the soft air duct, it shrinks when there is no wind and stretches out towards the blade tip when there is wind, which can automatically send hot air to the blade tip;

[0021] 2) Open air guide holes on the flexible air duct as needed (the closer to the blade tip, the larger the diameter and density of the air guide holes). Control the heat distribution along the flexible air duct during heating, thereby heating the leading edge of the blade on demand, that is, distributing the heat required for de-icing the leading edge of the blade as needed.

[0022] 3) Deliver the most heat to the blade tips (the closer to the blade tips, the larger the diameter and density of the air guide holes on the flexible air duct), giving priority to removing ice from the blade tips;

[0023] 4) Because there is always air loss along the flexible air duct, in order to maintain sufficient air pressure and push the hot air flow to the blade tip, the cross-sectional area of ​​the flexible air duct becomes smaller as it approaches the blade tip;

[0024] 5) For blades with blocked tips, the hot air blown out of the soft air duct can flow back to the root of the blade through the blade leading edge cavity outside the soft air duct and the hot air return hole on the baffle, and then be sucked in by the blower, blown into the heater, and after reheating, blown to the blade tip through the air guide pipe to form a stable circulating air duct. Figure 3 .

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1) The present invention adds a soft air duct design at the outlet of the last section of the rigid air duct. When hot air is available, the soft air duct extends outward, which not only extends the wind resource transportation channel and solves the construction problem of extending the air guide duct, but also enables the hot air to reach the blade tip first, ensuring the deicing effect of the blade tip and allowing the hot air resource to be accurately distributed to the blade where deicing is required;

[0027] 2) The flexible air duct of the present invention is provided with air guide holes at the position facing the leading edge of the blade, guiding the hot air directly to blow toward the leading edge of the blade, which not only improves the heat utilization efficiency, but also improves the deicing speed and deicing capacity of the leading edge of the blade;

[0028] 3) The diameter and number of air guide holes along the length of the flexible air duct of the present invention are designed according to the heat required for de-icing at different blade leading edge locations. The closer to the blade tip, the higher the priority (the larger the diameter and density of the air guide holes), so that the total heat of the de-icing system is scientifically distributed, prioritizing sufficient heat at the blade tip where de-icing is most needed. This not only improves the de-icing effect, but also significantly improves heat utilization efficiency, reducing the total power of the heater and the overall power consumption of the de-icing system.

[0029] 4) The cross-sectional area of ​​the flexible air duct of the present invention decreases as it approaches the blade tip. This allows the flexible air duct to maintain sufficient air pressure to push the hot air toward the blade tip, even though there are air guide holes along the way and there is air loss.

[0030] 5) When the blade tip is blocked and a normal de-icing hot air return duct cannot be formed, the present invention reconstructs a new hot air circulation duct by constructing a return duct in the blade leading edge cavity outside the soft air duct, thus solving the problem of air-heat de-icing being unable to be achieved due to blade tip blockage. In addition, the newly constructed hot air circulation duct allows hot air to return from the outlet of the soft air duct near the blade tip. The closer to the blade tip, the higher the temperature and the more heat. This fully complies with the principle of higher priority in allocating de-icing heat closer to the blade tip, resulting in better de-icing effect.

[0031] 6) In the case that the blade tip is blocked and a normal de-icing hot air return duct cannot be formed, the present invention newly constructs the hot air return duct of the leading edge cavity of the blade outside the soft air duct by opening a hot air return hole on the baffle. This can not only reduce the hot air return wind resistance and improve the de-icing performance of the system by making the total cross-sectional area of ​​the hot air return hole as large as possible, but also take into account the use of the baffle to support the soft air duct when there is no wind, so as to prevent the soft air duct from hanging upside down and ensure that the soft air duct can extend normally when there is wind. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0033] Figure 1 This is a schematic diagram of the installation structure of the existing wind turbine blade internal gas thermal deicing system.

[0034] Figure 2 Schematic diagram of the blade ice coverage state.

[0035] Figure 3 It is a structural schematic diagram of the present invention.

[0036] Figure 4 This is a schematic diagram of the connection between soft air duct and hard air duct.

[0037] Figure 5 This is a schematic diagram of the length of the soft air duct when the blade tip is not blocked.

[0038] Figure 6 This is a diagram of the distribution of air guide holes on the flexible air duct.

[0039] Figure 7 It is a schematic diagram of the structure of the present invention when the blade tip is blocked.

[0040] Figure 8 Schematic diagram of the flexible duct length when the blade tip is blocked.

[0041] Figure 9 This is the front view of the baffle structure.

[0042] Figure 10 The diagram shows the baffle preventing the flexible air duct from hanging upside down.

[0043] Figure 11 This is a diagram of the temperature changes of each blade after the de-icing system is turned on for half an hour.

[0044] Figure 12 This is a diagram of the temperature changes of each blade after the de-icing system is turned on for two hours.

[0045] In the figure: 1. Heater; 2. Blower; 3. Air guide duct; 4. Baffle; 5. Blade tip; 6. Web cavity; 7. Blade leading edge cavity; 8. Blade tip blockage; 9. Blade web; 10. Blade leading edge; 11. Blade trailing edge cavity; 12. Hoop; 13. Hot air return channel; 14. Blade root; 31. Hard air duct; 32. Soft air duct; 41. Hot air return hole; 42. Hard air duct perforation; 321. Air guide hole. DETAILED DESCRIPTION

[0046] The present invention will be further described below in conjunction with specific preferred embodiments, but the scope of protection of the present invention is not limited thereby.

[0047] In the description of the present invention, it should be noted that the terms "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate the description of the present invention and simplify the description. They are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation, and therefore should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0048] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; they may refer to mechanical connections; they may refer to direct connections, indirect connections through an intermediate medium, or internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0049] See also Figure 3-Figure 6 The first embodiment of the air-heating deicing system for fan blades of the present invention includes a heater 1 and a blower 2 installed in a manhole baffle at the root 14 of the blade. The air inlet of the heater 1 is connected to the air outlet of the blower 2, and the air outlet of the heater 1 is connected to the air inlet of the air duct 3. The air outlet of the air duct 3 points to the direction of the blade tip 5. The hot air sent out by the air duct 3 is blown toward the blade tip and then enters the air inlet of the blower 2 through the hot air return channel 13.

[0050] The front end of the air guide duct 3 adopts a conventional hard air duct 31, and the rear end of the air guide duct 3 adopts a soft air duct 32. The air inlet of the hard air duct 31 is connected with the air outlet of the heater 1, and the air outlet of the hard air duct 31 is connected with the air inlet of the soft air duct 32, and the soft air duct 32 is arranged in the blade leading edge cavity 7. The soft air duct 32 is provided with a plurality of air guide holes 321 at the position facing the blade leading edge 10 (that is, the side of the blade facing the windward side of the blade). When there is no hot air, the soft air duct 32 shrinks. When there is hot air, the soft air duct 32 extends to near the blade tip 5, so that the hot air blows toward the blade leading edge 10 and the blade tip 5, enters the web cavity 6 and the blade trailing edge cavity 11 through the process hole of the blade tip 5, and finally flows into the air inlet of the blower 2 located at the blade root 14 to form a hot air circulation channel.

[0051] The rigid air duct 31 is mounted on the blade web 9 , and a baffle 4 is mounted between the blade web 9 and the blade leading edge 10 , and an air outlet of the rigid air duct 31 passes through the baffle 4 .

[0052] When implementing:

[0053] 1. Fix the soft air duct 32, such as the air distribution duct, by the clamp 12 at the place where the baffle 4 is installed in the leading edge cavity 7 of the blade, or at the outlet of the last section of the hard air duct 31. Figure 4 ;

[0054] 2. The length of the soft air duct S2 is based on the distance S from the outlet of the last section of the hard air duct to the blade tip, minus the blade length S1 that the soft air duct 32 cannot pass because the cross-sectional area of ​​the blade leading edge cavity 7 is smaller as it approaches the blade tip 5. That is, the length of the soft air duct S2 = S - S1. Figure 5 ;

[0055] 3. As needed, air guide holes 321 are provided on the flexible air duct 32 towards the leading edge 10 of the blade. The size and density of the air guide holes 321 are determined based on the heat required for de-icing the leading edge 10 of the corresponding blade. The overall principle is that the closer to the blade tip 5, the higher the priority. That is, the closer to the blade tip 5, the larger the diameter and density of the air guide holes 321. Figure 6 ;

[0056] 4. The cross-sectional area of ​​the flexible air duct 32 becomes smaller as it gets closer to the blade tip, so as to maintain sufficient wind pressure and push the hot air flow toward the blade tip 5.

[0057] See also Figure 7-10The second embodiment of the air-heat deicing system for fan blades of the present invention is roughly the same as the first embodiment, except that the tip of the fan blade is blocked 8, and a plurality of hot air return holes 41 are opened on the baffle 4. After the hot air in the soft air duct 32 is blown out, it is blocked by the tip blockage 8 and cannot reach the web cavity 6 and the blade trailing edge cavity 11. It can only return through the new hot air return channel 13 formed by the hot air return holes 41 on the periphery of the air guide duct 3 in the blade leading edge cavity 7 and enter the air inlet of the blower 2 located at the blade root 14 to form a new hot air circulation channel.

[0058] Due to the blockage 8 of the blade tip, taking into account the cross-sectional area of ​​the hot air return channel 13, the length of the soft air duct S2' is based on the distance S from the outlet of the last section of the hard air duct to the blade tip, minus the blade length S1 that the soft air duct 32 cannot pass because the cross-sectional area of ​​the blade leading edge cavity 7 is smaller as it approaches the blockage 8 of the blade tip, and the length of the soft air duct S1' that needs to be shortened to ensure the cross-sectional area of ​​the hot air return channel 13, so that the cross-sectional area of ​​the blade leading edge cavity at the outlet of the soft air duct = the cross-sectional area of ​​the soft air duct + the cross-sectional area of ​​the newly formed hot air return channel 13, and the length of the soft air duct S2' = S - S1 - S1', see Figure 8 A plurality of hot air return holes 41 (such as Figure 9 ), so that a new hot air return channel 13 is formed on the periphery of the air guide duct 3 in the blade leading edge cavity 7 between the blade web 9 and the blade leading edge 10 (see Figure 3 right-pointing arrow in the middle).

[0059] In order to take into account the contraction of the soft air duct 32 when there is no wind, the baffle 4 can be used to block the soft air duct 32 so that it does not hang upside down. Even if the diameter of the hot air return hole 41 is smaller than the diameter of the soft air duct 32, Figure 10 .

[0060] The external temperature changes of the first blade with a soft air duct (air distribution duct) and the second and third blades without a soft air duct (air distribution duct) were recorded by using a drone and an infrared camera. Figure 11 、 Figure 12 The experimental results shown in Figure 11 This is the temperature change state diagram of each blade after the de-icing system is turned on for half an hour. Figure 12 This is a diagram of the temperature changes of each blade after the de-icing system is turned on for two hours.

[0061] Depend on Figure 11It can be seen that a greater amount of heat is concentrated at the rigid air duct outlet of the second and third blades. However, due to the installation of the flexible air duct (air distribution duct) on the first blade, some of the heat that would have been concentrated at the rigid air duct outlet is instead transported to the middle and tip of the blade. Furthermore, because the flexible air duct (air distribution duct) has air guide holes 321 located toward the leading edge 10 of the blade, the heat is primarily used to heat the leading edge 10 of the blade. Therefore, the temperature after the rigid air duct outlet of the first blade rises rapidly, significantly higher than the temperature at the corresponding locations on the second and third blades, and the temperature distribution is more even. Because the second blade is fixed in an upward direction and is exposed to a larger area of ​​sunlight, its temperature is higher than that of the third blade.

[0062] Depend on Figure 12 As can be seen, as the de-icing system's activation time increases, the outer surface temperature of all three blades increases. However, the temperature distribution of the first blade is more evenly distributed, with less fluctuation, than that of the second and third blades. The first blade's peak temperature is 35.6°C, the trough temperature is 31.0°C, and the temperature difference is 4.6°C. The second blade's peak temperature is 39.7°C, the trough temperature is 31.8°C, and the temperature difference is 7.9°C. The third blade's peak temperature is 41.2°C, the trough temperature is 26.6°C, and the temperature difference is 14.6°C. This indicates that installing the air distribution duct on the first blade minimizes the temperature difference and achieves the most uniform heat distribution, which is conducive to further improving the energy efficiency of the de-icing system.

[0063] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can, without departing from the scope of the technical solution of the present invention, make many possible changes and modifications to the technical solution of the present invention using the technical content disclosed above, or modify it into an equivalent embodiment with equivalent changes. Therefore, any simple modification, equivalent change, and modification made to the above embodiment in accordance with the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the scope of protection of the technical solution of the present invention.

Claims

1. A fan blade air heating deicing system, comprising a heater mounted within the blade and a blower, wherein the heater's air inlet is connected to the blower's air outlet, the heater's air outlet is connected to the air inlet of an air duct, the air outlet of the air duct pointing toward the blade tip, and the hot air blown out of the duct is connected to the blower's air inlet via a hot air return channel. The system is characterized by: The front end of the air duct is a hard air duct, and the rear end of the air duct is a soft air duct. The air inlet of the hard air duct is connected to the air outlet of the heater, and the air outlet of the hard air duct is connected to the air inlet of the soft air duct. The inner cavity of the blade is divided by the blade web into a blade leading edge cavity facing the windward side of the blade and a blade trailing edge cavity facing the leeward side of the blade; The soft air duct is an air distribution duct; The soft air duct is arranged in the leading edge cavity of the blade, and a plurality of air guide holes are opened on the side of the soft air duct facing the windward side of the blade. When there is no hot air, the soft air duct shrinks, and when there is hot air, the soft air duct extends to near the tip of the blade.

2. The fan blade gas thermal deicing system according to claim 1, characterized in that: The closer the air guide holes on the flexible air duct are to the blade tips, the larger the caliber and density of the air guide holes are.

3. The fan blade gas thermal deicing system according to claim 1, characterized in that: The cross-sectional area of ​​the flexible air duct becomes smaller as it approaches the blade tip.

4. The fan blade gas thermal deicing system according to claim 1, characterized in that: The hard air duct is installed on the blade web, and a baffle is installed between the blade web and the blade leading edge. The air outlet of the hard air duct passes through the baffle and is connected to the soft air duct.

5. The fan blade gas heating deicing system according to claim 4, characterized in that: When the blade tip is blocked, a plurality of hot air return holes are opened on the baffle, and a new hot air return channel is formed on the periphery of the air guide pipe between the blade web and the blade leading edge.

6. The fan blade gas thermal deicing system according to claim 5, characterized in that: The diameter of the hot air return hole is smaller than the diameter of the soft air duct.

7. The fan blade gas thermal deicing system according to any one of claims 1 to 6, characterized in that: The connection between the soft air duct and the hard air duct is fixed by a clamp.

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