Air-heat deicing system for fan blade

Abstract

The invention discloses a fan blade gas heat deicing system which comprises a heater and an air blower which are installed in a blade, an air inlet of the heater is connected with an air outlet of the air blower, an air outlet of the heater is communicated with an air inlet of an air guide pipe, an air outlet of the air guide pipe points to the blade tip direction, and a hard air pipe is adopted at the front end of the air guide pipe. The rear end of the air guide pipe is provided with a soft air pipe, an air inlet of the hard air pipe is communicated with an air outlet of the heater, an air outlet of the hard air pipe is communicated with an air inlet of the soft air pipe, the soft air pipe is arranged in a blade front edge cavity, a plurality of air guide holes are formed in the position, facing the blade front edge, of the soft air pipe, and when no hot air exists, the air guide holes are communicated with the hard air pipe. And when hot air exists, the flexible air pipe is stretched to be close to the blade tip or the blocked position of the blade tip. The air guide pipe can extend to the blade tip, the deicing effect of the blade tip is enhanced, a new hot air backflow channel can be constructed in the blade blocked by the blade tip, and the air heat deicing effect is achieved.

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 on the blades: since there is no effective means to remove the ice from the blades, they can only wait for the weather to warm up and the ice to melt naturally, 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, causing safety hazards to surrounding people, livestock, and equipment, and impacting the stable operation of the power grid, exacerbating the contradiction between electricity consumption and power generation during the ice period.

[0003] Gas-heat deicing is a relatively mature method for deicing blades of wind turbines. It can be used for both 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 designed air duct 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 deicing effect can be achieved. When designing specifically, such as Figure 1 , Figure 2 As shown, the heater 1 and the blower 2 are installed in the manhole baffle at the root 14 of the blade. 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 blade leading edge cavity 7 is too narrow to construct the air duct 3, 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 blade leading edge cavity 7 to the direction of the blade tip 5, and then flow back through the process holes set at the blade tip 5 through the web cavity 6 and the blade trailing edge cavity 11 into the air inlet of the blower 2 to form a hot air circulation channel.

[0004] After the blades are frozen, the ice changes the shape of the blades, destroys the original lifting body structure of the blades, and sharply reduces the wind-catching ability of the blades. In addition, the ice also increases the weight of the blades and increases the wind resistance, making it difficult for the blades to reach the theoretical speed, causing the wind turbine's power generation capacity to drop sharply or even shut down. The part that has the greatest impact on the lifting body structure is the leading edge 10 of the blade facing the wind, because the closer the ice is to the blade tip, the greater the moment of inertia, and the greater the impact on the blade. Therefore, the de-icing must first remove the ice from the leading edge 10 of the blade, and the closer the leading edge 10 of the blade is to the blade tip 5, the more priority it needs to be given to de-icing. In order to achieve a better gas-heat deicing effect and reduce the self-consumption of electricity, it is necessary to consider that the heat of the heater 1 is used preferentially at the position of the blade leading edge cavity 7 near the blade tip 5 during design. To this end, the gas-heat deicing system uses the air duct 3 to send hot air to the blade tip 5 along the blade belly 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 blades, the workers often cannot move forward to the place where the blade is one-third of the blade length away from the blade root (at the baffle 4), so the air duct 3 can only be arranged here; second, the hot air comes out from the heater 1 to the blade tip 5, and the further forward the heat is, the smaller the cross-sectional area is. The less, the lower the temperature, the worse the deicing 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 deicing function fails. The current method of repairing blades with blocked blade tips is to open a skylight at the blade tip 5, use a drilling machine to forcibly punch holes 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 blade 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 air thermal deicing system for fan blades cannot deliver hot air to a position close to the blade tip, the present invention provides an air thermal deicing system for fan blades which 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 thermal 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 thermal deicing after the blade tip is blocked.

[0007] In order to solve the above technical problems, the present invention adopts the following technical solutions: A fan blade air heating deicing system comprises a heater and a blower installed in the blade, 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 the air guide pipe, the air outlet of the air guide pipe points to the direction of the blade tip, and the hot air blown out of the air guide pipe blows toward the blade tip and then enters the air inlet of the blower through a hot air return channel. The structural features are: The front end of the air guide duct adopts a hard air duct, and the rear end of the air guide duct adopts 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 arranged in the leading edge cavity of the blade, and a plurality of air guide holes are provided 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.

[0008] Preferably, the size and density of the air guide holes on the flexible air duct are considered according to the heat required for deicing at that position. Generally, the closer the air guide holes on the flexible air duct are to the blade tips, the larger the caliber and density are.

[0009] Preferably, the cross-sectional area of ​​the flexible air duct becomes smaller as it approaches the blade tip, so as to maintain sufficient wind pressure to push the hot air flow toward the blade tip.

[0010] Preferably, the rigid air duct is installed on the blade web, and a baffle is installed between the blade web and the blade leading edge, and the air outlet of the rigid air duct passes through the baffle.

[0011] Preferably, when the blade tip is blocked, a plurality of hot air return holes are provided on the baffle plate to form a return air duct between the blade web and the blade leading edge.

[0012] Preferably, the diameter of the hot air return hole is smaller than the diameter of the soft air duct.

[0013] Preferably, the connection between the soft air duct and the hard air duct is fixed by a clamp.

[0014] Preferably, the flexible air duct is an air distribution duct.

[0015] Principle of the design method of the present invention: 1) With the characteristics of the soft air duct, it shrinks when there is no wind and stretches out to the tip of the blade when there is wind, and can automatically send hot air to the tip of the blade; 2) Open air guide holes on the soft air duct as needed (the closer the air guide holes are to the blade tip, the larger the diameter and density of the air guide holes), control the heat distribution along the soft air duct during heating, so as to heat the leading edge of the blade as needed, that is, distribute the heat required for de-icing the leading edge of the blade as needed; 3) Send the most heat to the blade tip (the closer to the blade tip, the larger the diameter and density of the air guide holes on the soft air duct), and give priority to removing ice from the blade tip; 4) Because there is always air loss along the way in the soft air duct, in order to maintain sufficient wind pressure and push the hot air flow to the blade tip, the cross-sectional area of ​​the soft air duct becomes smaller as it gets closer to the blade tip; 5) For blades with blocked blade 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 circulation air duct. Figure 3 .

[0016] Compared with the prior art, the present invention has the following beneficial effects: 1) The present invention adds a soft air duct design at the outlet of the last section of the hard air duct. When there is hot air, the soft air duct stretches out, which not only extends the transportation channel of wind resources 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, so that the hot air resources can be accurately distributed to the deicing position required by the blade; 2) The soft air duct of the present invention is provided with an air guide hole at a position toward the leading edge of the blade, so as to guide the hot air to blow directly 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; 3) The diameter and number of the air guide holes on the flexible air duct of the present invention are designed along its length direction according to the heat required for deicing the leading edge of the blades at different positions. The closer to the blade tip, the higher the priority level (the closer to the blade tip, the larger the diameter and density of the air guide holes). This allows the total heat of the deicing system to be scientifically distributed, giving priority to ensuring that the blade tip position that most needs deicing has sufficient heat. This not only has a good deicing effect, but also greatly improves the heat utilization efficiency, reduces the total power of the heater and the overall self-consumption of the deicing system; 4) The cross-sectional area of ​​the soft air duct of the present invention is smaller as it approaches the blade tip, so that although there are air guide holes along the soft air duct and there is always air loss, it can still maintain sufficient wind pressure to push the hot air flow to the blade tip; 5) When the blade tip is blocked and a normal deicing hot air return duct cannot be formed, the present invention reconstructs a new hot air circulation duct by constructing a return duct in the leading edge cavity of the blade outside the soft air duct, thereby solving the problem that the blade tip is blocked and the gas-heat deicing cannot be achieved. Moreover, the newly constructed hot air circulation duct enables the hot air to return from the outlet of the soft air duct close to the blade tip. The closer to the blade tip, the higher the temperature and the more heat. This fully complies with the principle that the closer to the blade tip, the higher the priority level of deicing heat distribution, and the better the deicing effect. 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 a hot air return duct in the leading edge cavity of the blade outside the soft air duct by opening a hot air return hole on the baffle plate. 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 plate 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

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. 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 creative work.

[0018] Figure 1 This is a schematic diagram of the installation structure of the existing wind turbine blade internal gas thermal deicing system.

[0019] Figure 2 Schematic diagram of the blade ice coverage state.

[0020] Figure 3 It is a schematic diagram of the structure of the present invention.

[0021] Figure 4 This is a schematic diagram of the connection between soft air duct and hard air duct.

[0022] Figure 5 This is a schematic diagram of the length of the soft air duct when the blade tip is not blocked.

[0023] Figure 6 This is a diagram showing the distribution of air guide holes on the flexible air duct.

[0024] Figure 7 It is a schematic diagram of the structure of the present invention when the blade tip is blocked.

[0025] Figure 8 Schematic diagram of the length of the soft air duct when the blade tip is blocked.

[0026] Fig. 9 This is a structural diagram of the baffle in front view.

[0027] Fig.10 The diagram shows the baffle preventing the flexible air duct from hanging upside down.

[0028] Fig.11 This is a diagram of the temperature changes of each blade after the de-icing system is turned on for half an hour.

[0029] Fig.12 This is a diagram of the temperature changes of each blade after the de-icing system is turned on for two hours.

[0030] In the figure: 1. heater; 2. blower; 3. air guide duct; 4. baffle; 5. blade tip; 6. belly plate cavity; 7. blade leading edge cavity; 8. blade tip blockage; 9. blade belly plate; 10. blade leading edge; 11. blade trailing edge cavity; 12. clamp; 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

[0031] The present invention is further described below in conjunction with specific preferred embodiments, but the protection scope of the present invention is not limited thereby.

[0032] In the description of the present invention, it should be noted that the terms "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0033] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0034] See also Figure 3-Figure 6 The first embodiment of the air-heat deicing system for fan blades of the present invention comprises 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, 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, and the hot air sent out by the air duct 3 blows toward the blade tip and then enters the air inlet of the blower 2 through the hot air reflux channel 13.

[0035] 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 a position close to the blade tip 5, so that the hot air is blown toward the blade leading edge 10 and the blade tip 5, and then 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.

[0036] The hard air duct 31 is installed on the blade web 9 , and a baffle 4 is installed between the blade web 9 and the blade leading edge 10 , and an air outlet of the hard air duct 31 passes through the baffle 4 .

[0037] When implementing: 1. The baffle 4 is installed in the blade leading edge cavity 7, or the outlet of the last section of the hard air duct 31 is fixed with a clamp 12 to fix the soft air duct 32, such as the air distribution duct, see Figure 4 ; 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, see Figure 5 ; 3. The soft air duct 32 is provided with air guide holes 321 at the position toward the leading edge 10 of the blade as required. The size and density of the air guide holes 321 are considered according to the heat required for deicing the leading edge 10 of the corresponding blade. The overall principle is that the closer to the blade tip 5, the higher the priority level, that is, the closer to the blade tip 5, the larger the diameter and density of the air guide holes 321. Figure 6 ; 4. The cross-sectional area of ​​the soft air duct 32 becomes smaller as it gets closer to the blade tip, so as to maintain sufficient wind pressure to push the hot air flow toward the blade tip 5.

[0038] See also Figure 7-10 The 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 reflow 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 a new hot air reflow channel 13 formed by the hot air reflow 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.

[0039] Due to the blockage 8 of the blade tip, considering the cross-sectional area of ​​the hot air return channel 13, the length S2' of the soft air duct 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 is closer to the blockage 8 of the blade tip, and the length S1' of the soft air duct that needs to be shortened in order 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 S2' of the soft air duct = S-S1-S1', see Figure 8 A plurality of hot air return holes 41 (such as Fig. 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 figure).

[0040] 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, Fig.10 .

[0041] 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. Fig.11 , Fig.12 The experimental results shown in Fig.11 This is the temperature change state diagram of each blade after the de-icing system is turned on for half an hour. Fig.12 This is a diagram of the temperature changes of each blade after the de-icing system is turned on for two hours.

[0042] Depend on Fig.11 It can be seen that more heat is concentrated at the outlet of the hard air duct of the second and third blades, while due to the installation of the soft air duct (air duct) on the first blade, part of the heat that should have been concentrated at the outlet of the hard air duct is transported to the middle and tip of the blade, and because the soft air duct (air duct) is provided with an air guide hole 321 toward the leading edge 10 of the blade, the heat is mainly used to heat the leading edge 10 of the blade. Therefore, the temperature after the outlet of the hard air duct of the first blade rises quickly, which is significantly higher than the temperature at the corresponding position on the second and third blades, and the distribution is relatively uniform. Since 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.

[0043] Depend on Fig.12It can be seen that as the de-icing system is turned on for an increased time, the outer surface temperatures of the three blades all rise, but the temperature distribution of the first blade is more balanced than that of the second and third blades, with smaller fluctuations. The peak temperature of the first blade is 35.6°C, the trough temperature is 31.0°C, and the temperature difference is 4.6°C; the peak temperature of the second blade is 39.7°C, the trough temperature is 31.8°C, and the temperature difference is 7.9°C; the peak temperature of the third blade is 41.2°C, the trough temperature is 26.6°C, and the temperature difference is 14.6°C. It can be seen that after the first blade is installed with the air distribution duct, the temperature difference is the smallest and the heat distribution is the most uniform, which is conducive to further improving the energy efficiency ratio of the de-icing system.

[0044] The above is only a specific implementation scheme of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the art can make many possible changes and modifications to the technical scheme of the present invention by using the technical content disclosed above without departing from the scope of the technical scheme of the present invention, or modify it into an equivalent embodiment of equivalent changes. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical scheme of the present invention should fall within the protection scope of the technical scheme of the present invention.

Claims

1. A fan blade air heating deicing system, comprising 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 blade tip direction, and the hot air blown out of the air duct is connected to the air inlet of the blower through a hot air return channel, characterized in that: The front end of the air guide duct adopts a hard air duct, and the rear end of the air guide duct adopts 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 arranged in the leading edge cavity of the blade, and a plurality of air guide holes are provided 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 air-heat deicing system according to claim 1, characterized in that: The closer the air guide holes on the soft air duct are to the blade tips, the larger the caliber and density of the air guide holes are.

3. The fan blade air-heat 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 air-heat 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, and the air outlet of the hard air duct passes through the baffle and is connected to the soft air duct.

5. The fan blade air-heat deicing system according to claim 4, characterized in that: When the blade tip is blocked, a plurality of hot air reflow holes are provided on the baffle plate, and a new hot air reflow channel is formed on the periphery of the air guide duct between the blade web and the blade leading edge.

6. The fan blade air-heat 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 air-heat 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.

8. The fan blade air-heat deicing system according to any one of claims 1 to 6, characterized in that: The soft air duct is an air distribution duct.

Images