Lift-drag hybrid airfoil blade with characteristics of lift force and resistance

Abstract

The invention discloses a lift-drag hybrid airfoil blade with both lift and drag characteristics, the hybrid blade is fixedly mounted on a fan, is used as a rotating component of the fan, and comprises a blade front end piece, a blade rear end piece, a blade window and a blade mounting and fixing piece; the blade rear end piece is composed of an outer wall and an inner wall, the outer wall and the inner wall are connected in a matched mode, and a plurality of blade windows with the same size are evenly formed in the inner wall from top to bottom. According to the blade window, the characteristics of an original lift type airfoil structure are changed, meanwhile, the blade window can absorb flowing air, so that the air generates resistance on the mixed type blade, the mixed type blade is pushed to rotate through flowing of the air, and the characteristics of a resistance type airfoil structure are shown. The double characteristics of the lift-drag wing type structure are utilized, under different fan rotating speeds, by changing the running state of the structure, the resistance type characteristic of the structure is more obvious under the low rotating speed, and the lift type characteristic of the structure is more obvious at the high speed.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of vertical wind turbine, and particularly relates to a lift-drag hybrid airfoil blade with lift and drag characteristics. BACKGROUND

[0002] In the vertical wind turbine, two kinds of airfoils are commonly used. One is the lift-type blade, which is more commonly used in medium and large wind turbines, and the other is the drag-type blade, which is more commonly used in small wind turbines. Among them, the lift-type blade is widely valued for its high efficiency, light weight, easy installation and other characteristics, and is the main reason for its more widespread application than the drag-type blade. The drag-type blade is characterized by its variety and different forms, and has been widely used in various small wind turbines. However, its low efficiency and large structure have hindered its widespread application, especially in the medium and high power segment.

[0003] The wind turbine with lift-type blades has the characteristics (also the shortcomings) of not being easy to start, and if the high efficiency characteristics of the lift-type blades are to be fully utilized, the rotational speed of the wind turbine needs to be run at a high tip speed ratio, i.e. the linear speed of the wind turbine blades is higher than the wind speed. However, the wind turbine often cannot actively increase the rotational speed to the desired speed, i.e. it cannot accelerate itself. Even after the wind turbine starts to rotate, it often rotates at a low tip speed ratio, which cannot guarantee that the wind turbine operates at an optimized speed or always operates at a high speed, so the advantages of the lift-type blades cannot be fully utilized.

[0004] The drag-type blades can start at low wind and run the wind turbine at a stable "low speed" due to their blade characteristics. However, due to the low power coefficient and large volume, the overall efficiency and cost-effectiveness of the wind turbine are not high. When running, the linear speed of the blades is always lower than the wind speed, i.e. the tip speed ratio is always less than 1.

[0005] Since people have known the characteristics of the two types of blades, many practices have installed both types of wind blades on a wind turbine, and various combinations and variations of the two types of blades have been implemented in many products, achieving good results. However, due to the coaxial arrangement of the two types of wind blades, the rotational speed of the wind turbine cannot meet the characteristics of the drag-type blades or the lift-type blades, and the efficiency and power generation of the wind turbine are lower than that of the lift-type blades alone, and the cost is higher (the cost of two types of blades), which cannot meet the needs of people. SUMMARY

[0006] Invention purposes: In order to solve the problems of the prior art, the application provides a lift-drag hybrid airfoil blade with lift and drag characteristics. On the basis of the lift blade, the airfoil of the blade is modified to have the characteristics of lift and drag airfoils (lift-drag airfoil) at the same time, but the cost is unchanged or less. In this way, a set of blades can solve the problem of starting at low speed of the fan, and at high speed of the fan, the lift blade can fully exert the high efficiency characteristics.

[0007] Technical scheme: A lift-drag hybrid airfoil blade with lift and drag characteristics, the hybrid blade is fixedly installed on a fan for rotation of the fan, comprising: a blade front end piece, a blade rear end piece, a blade window and a blade mounting fixing piece. The blade front end piece and the blade rear end piece are fixedly connected to form a lift-drag airfoil structure, the lift-drag airfoil structure has a drag type characteristic when the tip speed ratio is less than 1, and has a lift type characteristic when the tip speed ratio is greater than 1. The blade rear end piece is composed of an outer wall and an inner wall, the outer wall and the inner wall are connected to each other in a matched manner, the outer wall is a low pressure surface of an airfoil, and the inner wall is a high pressure surface of an airfoil. The inner wall is uniformly provided with a plurality of blade windows with the same size from top to bottom, the blade window can absorb the flowing air to generate resistance on the hybrid blade, and the rotation of the hybrid blade is driven by the flow of the air. The lift-drag airfoil structure is a drag type airfoil structure at the position of the blade window, and is a lift type airfoil structure at the position without the blade window.

[0008] Further improvements of the application are as follows: the blade front end piece and the blade rear end piece are processed by an integral molding process, and are processed by a stretching method or a mold opening process, the blade front end piece and the blade rear end piece are hollow, and the materials are aluminum alloy or glass steel.

[0009] Further improvements of the application are as follows: the cross-sectional shapes of the lift-drag airfoil structures at different positions of the blade front end piece and the blade rear end piece can be the same or different.

[0010] Further improvements of the application are as follows: the larger the area of the blade window is, the more obvious the drag type blade characteristics are, the number, size, shape and position of different blade windows can obtain different drag type blade characteristics, the proportion of the sum of the areas of all the blade windows to the entire blade surface area determines the lift-drag ratio, the more the areas of all the blade windows are, the more obvious the drag type characteristics are, but a part of the lift torque at the tip speed ratio greater than 1 is lost, and the more obvious the effect is when the positions of all the blade windows are at the tail end of the inner wall of the lift-drag airfoil structure.

[0011] The further improvement of the present application is as follows: the blade mounting fixture is a connecting piece for mounting the mixed blade on the fan, and the blade mounting fixture is provided with a plurality of pieces located between the upper and lower adjacent blade windows and corresponding to the blade links on the fan.

[0012] The further improvement of the present application is as follows: one end of the blade mounting fixture penetrates the inner wall of the blade rear end piece and is fixedly mounted on the outer wall and the inner wall of the blade rear end piece by welding; the other end of the blade mounting fixture is fixedly connected with the blade link on the fan by screwing or welding.

[0013] The further improvement of the present application is as follows: the mixed blade is mounted on the vertical fan, and the vertical fan comprises a fan main shaft, a fan main shaft flange, a blade pull rod fixing hole, a blade pull rod and a blade link; The fan main shaft is sleeved with a plurality of fan main shaft flanges from top to bottom, and the sidewall of each fan main shaft flange is evenly provided with a plurality of blade pull rod fixing holes; one end of the blade pull rod is fixedly connected with the blade pull rod fixing hole; and the other end of the blade pull rod is correspondingly connected with a position corresponding blade link. One end of each of the blade mounting fixtures on the mixed blade from top to bottom is fixedly connected with the position corresponding blade link by screwing or welding.

[0014] The further improvement of the present application is as follows: the attack angle of the mixed blade on the fan can be dynamically adjusted in a large range, and the attack angle changes with the change of the fan speed; when the fan speed is low, the attack angle is changed to make the blade highlight the resistance type characteristics; when the fan speed is high, the attack angle is changed to make the blade highlight the lift type characteristics; when the attack angle lags, the resistance type blade characteristics of the fan are more obvious, and when the attack angle leads, the lift type blade characteristics of the fan are more obvious; if the wind power is small and unstable, the attack angle can lag more, and if the wind power is large, the attack angle can lead more.

[0015] The further improvement of the present application is as follows: the torque characteristics of the lift-drag airfoil are converted under different tip speed ratios; at low speed, the resistance type characteristics dominate, and at high tip speed ratio, the lift type characteristics dominate; specifically as follows: At low tip speed ratio or zero, the mixed blade is between 170°-350°, which can generate effective torque to drive the fan to rotate; Under the action of the torque, the speed of the fan rises, at this time, the tip speed ratio rises, the torque of the lift type blade begins to increase, and the torque of the resistance type blade decreases; When the fan speed continues to increase, the fan runs in a high tip speed ratio condition, the drag type blade can be ignored, and the torque of the lift type blade occupies a dominant position.

[0016] Advantages: the lift-drag hybrid airfoil blade of the application has the following advantages: 1. The blade window changes the original lift type airfoil structure, and the blade window can absorb the air flowing through, so that the air generates resistance on the hybrid blade, thereby utilizing the flow of air to push the rotation of the hybrid blade, and showing the characteristics of the drag type airfoil structure.

[0017] 2. The application utilizes the dual characteristics of the lift-drag airfoil structure, automatically changes the operating state at different fan speeds, so that the drag type characteristic is more obvious at low speed, and the lift type characteristic is more obvious at high speed. Thus, a set of blades can produce the functions of two sets of blades, and both the "two sets" of functions can play their advantages in the best operating state. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 is a structure diagram of the hybrid blade of the application Figure 1 ; Figure 2 is a structure diagram of the hybrid blade of the application installed on the fan Figure 3 is a structure diagram of the hybrid blade of the application installed on the fan Figure 4 is a structure diagram of the hybrid blade of the application installed on the fan Figure 5 is a structure diagram of the hybrid blade of the application installed on the fan Figure 6 is a structure diagram of the hybrid blade of the application Figure 2 ; Figure 7 is a structure diagram of the hybrid blade of the application Figure 6 is a structure diagram of the hybrid blade of the application Figure 8 is a structure diagram of the hybrid blade of the application installed on the fan Figure 9 is a structure diagram of the hybrid blade of the application installed on the fan Figure 10 is a structure diagram of the hybrid blade of the application installed on the fan Figure 11 is a structure diagram of the hybrid blade of the application installed on the fan DETAILED DESCRIPTION

[0019] The technical solutions in the embodiments of the present invention will be clearly and completely described below, so that those skilled in the art can better understand the advantages and features of the present invention, thereby making a clearer definition of the scope of protection of the present invention. The embodiments described in this invention are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention. Example

[0020] like Figure 1 As shown, a hybrid airfoil blade exhibiting both lift and drag characteristics is mounted on a wind turbine and serves as a component for turbine rotation. The hybrid blade comprises: a blade leading edge component 1, a blade trailing edge component 2, a blade window 3, and a blade mounting fastener 4.

[0021] The blade tip member 1 and the blade rear member 2 are fixedly connected to form an integral mechanical structure with a certain lift-drag airfoil. In this integral mechanical structure, the cross-sectional shapes of the lift-drag airfoil structure at different positions can be the same or different. The lift-drag airfoil structure has drag characteristics at low speeds (tip speed ratio < 1) and lift characteristics at high speeds (tip speed ratio > 1).

[0022] The blade tip part 1 and blade rear part 2 are manufactured using a one-piece molding process, which can be achieved through stretching or die-cutting. Considering cost and application, aluminum alloy or fiberglass is used; however, any material with sufficient strength and lightweight can be used. Both the blade tip part 1 and blade rear part 2 are hollow to reduce the weight of the blade.

[0023] The blade rear end component 2 is composed of an outer wall 21 and an inner wall 22, which are connected to each other. The outer wall 21 is the low-pressure surface of the airfoil, and the inner wall 22 is the high-pressure surface of the airfoil.

[0024] The lift type airfoil used in the vertical fan, because the windward angle changes in the rotation process. The arc length of the outer wall and the inner wall can be the same (symmetrical) or different (asymmetrical) as the vertical fan selection, but the symmetrical or asymmetrical outer wall and the inner wall form the airfoil belonging to the category of lift type airfoil, and the characteristics will not produce the characteristics of the drag type airfoil. The lift and drag airfoil structure of the present application breaks the category of lift type airfoil, that is, the structure of "destroying" the inner wall (adopting the window structure), so that it weakens the characteristics of the lift type airfoil and enhances the characteristics of the drag type airfoil at a small tip speed ratio (tip speed ratio <1), and at a large tip speed ratio (tip speed ratio >1), the characteristics of the lift type airfoil are strengthened, and the characteristics of the drag type airfoil are weakened or even eliminated.

[0025] The inner wall 22 is uniformly provided with a plurality of blade windows 3 of the same size from top to bottom, the blade window 3 changes the characteristics of the original lift type airfoil structure, and at the same time, the blade window 3 can absorb the flowing air, so that the air generates resistance on the mixed type blade, thereby utilizing the flow of air to drive the rotation of the mixed type blade, and showing the characteristics of the drag type airfoil structure.

[0026] The lift and drag airfoil structure of the present application is like a drag type airfoil structure at the position of the blade window 3, and is a lift type airfoil structure at the position without the blade window 3. Therefore, the entire blade can be regarded as a mixed blade of drag type and lift type.

[0027] If the area of the blade window 3 of the present application is larger, the characteristics of the drag type blade are more obvious, therefore, by designing the number, size, shape and position of the different blade windows 3, the characteristics of the blades of different drag types can be obtained, so that the blades with optimal starting characteristics and optimal power generation efficiency at high speed and low speed for different fans can be designed.

[0028] The blade mounting and fixing part 4 is a connecting part for fixing and mounting the mixed type blade on the fan, the blade mounting and fixing part 4 is provided with a plurality of parts, located between the adjacent blade windows 3, and the position corresponds to the blade link 10 on the fan.

[0029] One end of the blade mounting and fixing part 4 penetrates the inner wall 22 of the blade rear end part 2, and is fixedly mounted on the outer wall 21 and the inner wall 22 of the blade rear end part 2 by welding. The other end of the blade mounting and fixing part 4 is fixedly connected with the blade link 10 on the fan by screwing or welding.

[0030] As Figure 2As shown, the mixed type blade of the present application is fixedly installed on the vertical type fan, which comprises a fan main shaft 6, a fan main shaft flange 7, a blade pull rod fixing hole 8, a blade pull rod 9 and a blade link 10. The fan main shaft 6 is sleeved with a plurality of fan main shaft flanges 7 from top to bottom, and the side wall of each fan main shaft flange 7 is evenly distributed with a plurality of blade pull rod fixing holes 8. One end of the blade pull rod 9 is fixedly connected with the blade pull rod fixing hole 8, and the other end of the blade pull rod 9 is correspondingly connected with a blade link 10 at a corresponding position. One end of each of the blade installation fixtures 4 of the mixed type blade from top to bottom is fixedly connected with the blade link 10 at a corresponding position by means of screwing or welding.

[0031] During the installation of the mixed type blade on the vertical type fan, the angle (which can be referred to as the attack angle) between the conventional lift type blade and the blade link is basically a right angle or only has a small range of change. The mixed type blade in the present application can adjust the attack angle in a large range through simulation and experiment, so as to obtain the best full-range effect.

[0032] The method for changing the operating state of the blade of the present application on the fan is as follows: Change the attack angle of the blade: the angle between the mixed type blade of the present application and the tangent line when the blade rotates relative to the vertical type fan is referred to as the attack angle. Figures 3-5 As shown, when the attack angle lags, the resistance type blade characteristics of the fan are more obvious, and when the attack angle leads, the lift type blade characteristics of the fan are more obvious. If in the area where the wind force is relatively small and unstable, more lagging can be considered. If in the area where the wind force is relatively large, more leading can be considered. Unlike the conventional vertical shaft fan blade, the attack angle of the lift-drag airfoil structure of the present application on the fan can be adjusted in a large range; the conventional vertical shaft fan blade has a fixed attack angle, which is fixed during installation and does not change during operation. The blade of the present application dynamically changes the attack angle, which changes with the change of the rotating speed of the fan. The purpose is to change the attack angle when the fan is at low speed, so that the blade highlights the resistance type characteristics, and to change the attack angle when the fan is at high speed, so that the blade highlights the lift type characteristics.

[0033] When the mixed type blade of the present application is installed on the vertical type fan, the following parameters can be adjusted to make the fan have good starting performance (low speed) and good lift type blade characteristics (high speed) at the same time: (1) the number of fan blades; (2) the solidity of the fan, which is reflected in the width and number of blades; (3) the radius of the fan; (4) the number, area and distribution position of the windows.

[0034] According to the structure of the fan, the annual wind resource distribution of the wind field and the power size of the fan, the size of the blade is selected, and the lift-drag ratio of the blade can be adjusted by the size, position and number of the windows.

[0035] Generally speaking, considering the strength of the blade and the complexity and cost of the process, the number of windows should not be too many. The proportion of the sum of the areas of all the windows to the entire blade surface area determines the lift-drag ratio. The more the windowed area, the more obvious the drag-type characteristics, but part of the lift torque at high tip speed ratio is lost. The position of the window at the tail end of the inner wall of the airfoil is more obvious.

[0036] As shown in Figures 6-7 , a profile is made at different positions of the blade, A is made at a position without a window, and B is made at a position with a window. It can be seen that A is a lift-type airfoil, and B is more like a variant of a drag-type airfoil, which can effectively utilize wind power to drive the fan to rotate when the tip speed ratio is less than 1, especially on the third wind receiving surface, as shown in Figure 8 .

[0037] At low or zero tip speed ratio, the torque curve generated by the blade at different angles during one revolution is as shown in Figure 9 , which is different from the ordinary lift-type blade. The blade can generate effective torque to drive the fan to rotate between 170° and 350°. (The starting point of the first wind receiving surface is the 0° position, and the fan rotates counterclockwise).

[0038] Under the action of this torque, the speed of the fan rises, and the tip speed ratio increases. The torque curve of the blade during one revolution is as shown in Figure 10 . The torque contribution of the lift-type blade begins to increase, but the torque of the drag-type blade decreases but still contributes.

[0039] The speed of the fan will continue to rise, and the fan will operate at a high tip speed ratio. The torque curve of the blade during one revolution is as shown in Figure 11 . At this time, the contribution of the drag-type blade can be ignored, and the torque of the lift-type blade dominates.

[0040] It can be seen that the torque characteristics of the lift-drag airfoil will change under different tip speed ratios. At low speed, the drag-type characteristics dominate, and at high tip speed ratio, the lift-type characteristics dominate. During the conversion process, it is a mixed type.

[0041] The present application utilizes the dual characteristics of the lift-drag airfoil structure. By changing its operating state at different fan speeds, the drag-type characteristics are more obvious at low speed, and the lift-type characteristics are more obvious at high speed. Thus, a set of blades can produce the functions of two sets of blades, and both "two sets" of functions can be in their best operating state to exert their advantages.

Claims

1. A hybrid airfoil blade exhibiting both lift and drag characteristics, wherein the hybrid blade is fixedly mounted on a wind turbine for wind turbine rotation, characterized in that: include: Blade front end component (1), blade rear end component (2), blade window (3) and blade mounting fastener (4); The blade front end part (1) and the blade rear end part (2) are fixedly connected to form a lift-drag airfoil structure. The lift-drag airfoil structure has drag characteristics when the tip speed ratio is <1 and lift characteristics when the tip speed ratio is >1. The blade rear end component (2) is composed of an outer wall (21) and an inner wall (22). The outer wall (21) and the inner wall (22) are connected to each other. The outer wall (21) is the low-pressure surface of the airfoil, and the inner wall (22) is the high-pressure surface of the airfoil. The inner wall (22) is evenly provided with several blade windows (3) of the same size from top to bottom. The blade windows (3) can absorb the flowing air, so that the air generates resistance on the hybrid blades and the flow of air drives the rotation of the hybrid blades. The airfoil structure described above is a drag type airfoil structure at the position of the blade window (3), and a lift type airfoil structure at the position where the blade window (3) is not open.

2. The lift-drag hybrid airfoil blade with both lift and drag characteristics according to claim 1, characterized in that: The blade front end part (1) and blade rear end part (2) are processed by integral molding process, by stretching method or mold opening process. The blade front end part (1) and blade rear end part (2) are hollow and are made of aluminum alloy or fiberglass.

3. The lift-drag hybrid airfoil blade with both lift and drag characteristics according to claim 1, characterized in that: The cross-sectional shapes of the lift-drag airfoil structure at different positions of the blade front end member (1) and the blade rear end member (2) can be the same or different.

4. The lift-drag hybrid airfoil blade with both lift and drag characteristics according to claim 1, characterized in that: The larger the area of ​​the blade window (3), the more obvious its drag-type blade characteristics. Different numbers, sizes, shapes and positions of blade windows (3) can result in different drag-type blade characteristics. The ratio of the sum of the areas of all blade windows (3) to the total blade surface area determines the lift-drag ratio. The more areas of all blade windows (3), the more obvious the drag-type characteristics, but a portion of the lift torque is lost when the tip speed ratio is >1. The more obvious the effect, the better the position of all blade windows (3) is at the tail end of the inner wall of the lift-drag airfoil structure.

5. The lift-drag hybrid airfoil blade with both lift and drag characteristics according to claim 1, characterized in that: The blade mounting fastener (4) is a connector for fixing the hybrid blades on the fan. There are several blade mounting fasteners (4) located between adjacent blade windows (3) and their positions correspond to the blade rings (10) on the fan.

6. The lift-drag hybrid airfoil blade with both lift and drag characteristics according to claim 1, characterized in that: One end of the blade mounting fastener (4) passes through the inner wall (22) of the blade rear end part (2) and is fixedly installed on the outer wall (21) and inner wall (22) of the blade rear end part (2) by welding; the other end of the blade mounting fastener (4) is fixedly connected to the blade ring (10) on the wind turbine by screws or welding.

7. The lift-drag hybrid airfoil blade with both lift and drag characteristics according to claim 1, characterized in that: The hybrid blades are fixedly installed on a vertical fan, which includes: a fan main shaft (6), a fan main shaft flange (7), a blade tie rod fixing hole (8), a blade tie rod (9), and a blade connecting ring (10). The main shaft (6) of the fan is fitted with several fan shaft flanges (7) from top to bottom. Several blade tie rod fixing holes (8) are evenly distributed on the side wall of each fan shaft flange (7). One end of the blade tie rod (9) is fixedly connected to the blade tie rod fixing hole (8), and the other end of the blade tie rod (9) is connected to a blade connecting ring (10) with a corresponding position. The ends of the blade mounting fasteners (4) on the hybrid blade from top to bottom are respectively fixedly connected to the blade rings (10) corresponding to the positions by screws or welding.

8. The lift-drag hybrid airfoil blade with both lift and drag characteristics according to claim 1, characterized in that: The angle of attack of the hybrid blades on the wind turbine can be dynamically adjusted over a wide range. The angle of attack changes with the wind turbine speed. At low wind turbine speeds, the angle of attack is changed to make the blades more prominent in drag characteristics, while at high wind turbine speeds, the angle of attack is changed to make the blades more prominent in lift characteristics. When the angle of attack is lagging, the drag characteristics of the wind turbine blades are more obvious, while when the angle of attack is leading, the lift characteristics of the wind turbine blades are more obvious. In areas with low and unstable winds, the angle of attack can be delayed more; in areas with high winds, the angle of attack can be advanced more.

9. The lift-drag hybrid airfoil blade with both lift and drag characteristics according to claim 1, characterized in that: The torque characteristics of the lift-drag airfoil change under different tip speed ratios. At low speeds, the drag characteristic dominates, while at high tip speed ratios, the lift characteristic dominates; specifically as follows: At low or zero tip speed ratios, the hybrid blades can generate effective torque to drive the fan to rotate between 170° and 350°. Under the action of this torque, the speed of the fan increases. At this time, the tip speed ratio increases, the torque of the lift blades begins to increase, and the torque of the drag blades decreases. As the fan speed continues to increase, operating the fan under a high tip speed ratio condition, the drag-type blades become negligible, while the torque of the lift-type blades becomes dominant.

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