CN118934437A

CN118934437A - A U-shaped vertical axis wind wheel, wind turbine and wind power generation system

Info

Publication number: CN118934437A
Application number: CN202411174734.1A
Authority: CN
Inventors: 姜宜辰; 韩林岑; 宗智
Original assignee: Dalian University of Technology
Current assignee: Dalian University of Technology
Priority date: 2024-08-26
Filing date: 2024-08-26
Publication date: 2024-11-12

Abstract

The present invention discloses a U-shaped vertical axis wind wheel, a wind turbine and a wind power generation system. The U-shaped vertical axis wind wheel comprises variable cross-section blades, a main shaft, a horizontal cross brace and a rotating base; the main shaft is vertically mounted on the rotating base; a plurality of variable cross-section blades are symmetrically arranged along the circumference of the main shaft, and the variable cross-section blades include equal cross-section vertical blades located at the upper part and extending parallel to the main shaft and variable cross-section curved blades located at the lower part gradually approaching and finally connected to the main shaft; the equal cross-section vertical blades are connected to the main shaft from top to bottom by a plurality of horizontal cross braces; the variable cross-section blades are connected to the main shaft through a truss, and the variable cross-section blades, the main shaft and the horizontal cross brace rotate synchronously. The present invention adopts variable cross-section blades to allow the wind turbine base to bear the blade weight, reduce the horizontal cross brace load, and realize the large-scale vertical axis wind turbine while saving the construction cost of the vertical axis wind turbine.

Description

U-shaped vertical axis wind wheel, wind turbine and wind power generation system

Technical Field

The invention relates to the technical field of wind power generation, in particular to a vertical axis wind power generation device, and specifically relates to a U-shaped vertical axis wind wheel, a wind turbine and a wind power generation system.

Background

Wind energy is a renewable clean energy source and is favored because of its large reserves. Compared with onshore wind energy, offshore wind power in most sea areas in China has high efficiency and good quality; the offshore wind farm is far away from the land, is not influenced by urban planning, and does not need to worry about the influence of noise, electromagnetic waves and the like on residents. The offshore wind farm has the advantages of high wind speed, less static period, low turbulence intensity, no land occupation, and convenience in conveying high-power and large-diameter fans through water transportation. Non-fossil energy sources are being developed greatly. The construction of the offshore wind power base is encouraged, and the offshore wind power is propelled to be distributed to deep water offshore areas. The offshore wind power cluster development in the coastal areas of southeast is actively promoted. The method mainly comprises the steps of building offshore wind power bases such as Guangdong, fujian, zhejiang, jiangsu, shandong and the like. The wind power generation in the sea is actively developed in the Yue harbor Australian area and the surrounding areas. The development and demonstration application of the technology such as the development of offshore wind power in deep sea areas are promoted. Besides the natural advantages of rich resources and the like, the offshore wind power is close to the eastern load center, so that the construction pressure of a 'western electric eastern transmission' channel can be reduced, the defect that energy sources in China are distributed in an economic development area in an unbalanced manner can be overcome, and sufficient and low-cost clean energy sources are provided for coastal areas.

The wind turbine can be divided into a horizontal axis wind turbine and a vertical axis wind turbine according to the included angle between the axis and the ground. The floating wind turbines which are put into use at present are all horizontal axis wind turbines because the land horizontal axis wind turbines in the past decades are vigorously developed, and the technology of manufacturing, transporting, installing and the like is mature. However, floating horizontal axis wind turbines also expose a number of problems during high power development: the floating horizontal axis wind turbine is positioned at the top of the tower, and the safety of the platform in stormy waves is seriously reduced due to overhigh integral gravity center of the fan and the platform along with the increase of the single power generation of the horizontal axis wind turbine; the height of the tower is too high, so that the floating horizontal axis wind turbine is more difficult to install and work, the daily maintenance cost is higher and higher, the industrialization critical cost is greatly increased, and an industrial technology bottleneck is formed; the circulating gravity load stress can be generated in the rotating process of the horizontal-axis wind turbine, and is larger and larger along with the increase of the size of the wind turbine, so that the expansion of the horizontal-axis wind turbine is difficult in the design stage; the horizontal axis wind turbine has extremely high requirements on wind direction, and an additional yaw device is required to be installed to ensure that the wind wheel is always perpendicular to the incoming flow direction of wind; the horizontal axis wind turbine wake has an adverse effect, and the average efficiency of clustered fans is significantly lower than that of single fans.

Compared with a horizontal axis fan, the vertical axis fan has the following advantages: the rotating shaft of the vertical shaft fan is vertical to the ground, and equipment such as a generator cabin and the like can be arranged at a position close to the platform, so that the gravity center of the whole fan is lowered, and the stability of the platform is improved; the lower cabin position is convenient for daily maintenance; the blades of the vertical axis fan are kept vertical to the ground all the time in the running process, and do not bear severe gravity load change; the vertical axis wind turbine is capable of capturing wind energy from all directions, thus eliminating the need for yaw wind turbine devices, thereby simplifying the design and maintenance of the wind turbine system. Given these characteristics of a vertical axis wind turbine, it is considered a potential competitor for future offshore wind resource development and utilization. Related report researches show that the vertical axis fan structure is reliable, cost-effective and easy to manufacture the rotor on the scale of 10-20MW, and compared with the current shallow water horizontal axis wind turbine system, the deep water floating vertical axis fan system can reduce the cost by more than 20%. Therefore, in the offshore wind power deep water open sea process of China, the development of the vertical axis fan is an important means for breaking through the development bottleneck.

The weather is complex and changeable in the tropical and subtropical areas at most sea areas in China, and is a disaster area with heavy disasters such as typhoons, heavy rain, strong convection and the like, and the floating wind turbine is also required to have higher wind and wave resistance. The floating horizontal axis fan adopts a floating platform as a base, and swings under the combined action of factors such as sea surface wind, wave and current to drive a fan tower and a wind wheel to move greatly, and the gravity center of the horizontal axis fan is higher, so that accidents such as overturning and structural fracture are easy to occur. The vertical axis fan has the characteristics of low gravity center, low noise, no yaw, low vibration, convenient maintenance and the like, and has strong adaptability to the offshore extreme sea conditions.

The vertical axis wind turbine can be divided into a resistance type vertical axis wind turbine and a lift type vertical axis wind turbine according to the working principle, and compared with the resistance type vertical axis wind turbine, the lift type vertical axis wind turbine has higher power generation efficiency, so that the lift type vertical axis wind turbine is the development direction of the future floating type vertical axis wind turbine. The lift type vertical axis wind turbine can be classified into a Darrieus type vertical axis wind turbine and an H type vertical axis wind turbine according to the external shape. The Darrieus type vertical axis wind turbine blade is elliptical, and the upper end and the lower end of the blade are both connected with the main shaft, so that the gravity of the blade is mainly borne by the main shaft, and the Darrieus type vertical axis wind turbine blade is also the reason for the large-scale of the Darrieus type vertical axis wind turbine. However, the oval blade of the Darrieus type vertical axis wind turbine has smaller wind sweeping area, and under the condition of the same power generation, the Darrieus type vertical axis wind turbine needs larger size, and the disadvantage leads to the gradual elimination of the Darrieus type vertical axis wind turbine. Compared with Darrieus type vertical axis wind turbines, the H-type vertical axis wind turbine has larger wind sweeping area, which is also the reason why the H-type vertical axis wind turbine becomes the main stream in recent years. However, the weight of the H-shaped vertical axis wind turbine blade is borne by the horizontal cross brace, the horizontal cross brace is similar to a cantilever beam, and the blade is equivalent to adding a load at one suspended end of the cantilever beam, so that the H-shaped vertical axis wind turbine has extremely high requirements on the strength of the horizontal cross brace, and the structural strength of the horizontal cross brace also becomes an important factor for restricting the development of the H-shaped vertical axis wind turbine.

The existing two types of vertical-axis wind turbines have respective defects, so that a vertical-axis wind turbine with larger wind sweeping area and independent of horizontal cross braces for bearing the weight of blades is urgently needed to be designed, and the development needs of the offshore floating type vertical-axis wind turbine are met.

Disclosure of Invention

In view of the defects in the prior art, the invention provides a U-shaped vertical axis wind turbine, a wind turbine and a wind power generation system. The variable cross-section blade is adopted, so that the main shaft of the wind turbine bears the gravity of the blade, the horizontal transverse support load is reduced, the construction cost of the vertical axis wind turbine is saved, and the large-scale vertical axis wind turbine is realized.

The invention adopts the following technical means:

In one aspect, the invention discloses a U-shaped vertical axis wind turbine comprising: variable cross-section blade, main shaft, horizontal cross brace and rotating base; a main shaft is vertically arranged on the rotating base; a plurality of variable cross-section blades are symmetrically arranged along the circumferential direction of the main shaft, and each variable cross-section blade comprises a constant cross-section vertical blade and a variable cross-section bending blade from top to bottom in sequence; the constant cross section vertical blades are arranged in parallel with the main shaft, and the bottoms of the variable cross section bending blades are connected with the main shaft; the constant cross section vertical blades are connected with the main shaft through horizontal cross braces, the variable cross section blades are connected with the main shaft through trusses, and the variable cross section blades, the main shaft and the horizontal cross braces synchronously rotate.

Further, the chord length and the width of the blade of the constant-section vertical blade are unchanged from top to bottom, the ratio of the chord length to the radius of the wind wheel is smaller than 0.2, and the ratio of the width to the chord length is 0.12-0.25.

Further, the chord length of the variable-section curved blade increases from top to bottom in equal proportion: when the height of the blade is reduced by 10% of the radius of the wind wheel, the chord length of the blade is increased by 1.05-1.2 times of the previous chord length, and the ratio of the width of the blade to the chord length is kept unchanged.

Further, the constant section vertical blades are connected with the main shaft through a plurality of horizontal cross braces, and all the horizontal cross braces of the blades arranged at the same level are on the same horizontal line.

Further, the main shaft comprises a blade connecting shaft and a transmission shaft, the transmission shaft is connected with the blade connecting shaft through a shaft end flange, one end of the blade connecting shaft is connected with the upper end of the variable cross-section blade through a horizontal transverse support, and the other end of the blade connecting shaft is connected with the lower end of the variable cross-section blade through a truss.

Further, the upper end of the transmission shaft of the main shaft is connected with the lower end of the blade connecting shaft, and torque generated by the blades is transmitted; the connection transmits the gravity of the upper end part to the rotating base through the bearing.

Further, one end of the horizontal cross brace, which is close to the main shaft, is connected with the main shaft by an upper truss.

Further, the main shaft is connected with the uniform-section vertical blade through a plurality of steel cables, and at least one steel cable is connected between the top of the uniform-section vertical blade and the main shaft.

Further, the steel cables are connected with the main shaft and the blades through hanging rings, and each hanging ring is connected with 1-2 steel cables according to the structural strength requirement of the fan.

Further, the vertical blades with the equal cross sections of the blades and the variable cross section bending blades are connected through flanges, and the connecting part is provided with a horizontal cross support connecting main shaft, so that the structure of the connecting part is enhanced.

Further, the two ends of the variable-section blade and the horizontal cross brace are embedded with metal structural members for ensuring the overall strength, the connection flange and the installation of steel ropes thereof.

On the one hand, the invention also discloses a U-shaped vertical axis wind turbine, which comprises a motor and the U-shaped vertical axis wind turbine as described in any one of the above.

Further, the motor is located between the variable-section blade and the rotating base.

Further, the transmission shaft is connected with a generator rotor through a coupler; when the generator works, the variable cross-section blades, the main shaft and the horizontal cross brace are used as rotors, and the generator shell is used as a stator to generate electricity.

On the other hand, the invention also discloses a wind power generation system which comprises a plurality of U-shaped vertical axis wind turbines, wherein the U-shaped vertical axis wind turbines are connected in a grid-connected mode.

Compared with the prior art, the invention has the following advantages:

The invention discloses a U-shaped wind wheel with a large wind sweeping area and high generating capacity. Under the condition that the product of the height and the diameter of the wind wheel is the same, the wind sweeping area of the U-shaped vertical axis wind turbine adopting the U-shaped wind wheel is increased by 37.37 percent compared with the wind sweeping area of the Darrieus-type vertical axis wind turbine, and is reduced by 10.8 percent compared with the wind sweeping area of the H-type vertical axis wind turbine. Under the condition that the chord lengths of the blades are consistent, the power generation efficiency of the U-shaped vertical axis wind turbine is approximately equal to that of the Darrieus type vertical axis wind turbine, and compared with that of the H-shaped vertical axis wind turbine, the power generation efficiency of the U-shaped vertical axis wind turbine is improved by 4.96%.

Meanwhile, the U-shaped variable cross-section blade shape is adopted, the gravity of the blade is transferred to the main shaft through the variable cross-section bent blade, and the main shaft bears the gravity of the blade, so that the horizontal cross brace only needs to bear the centrifugal force of the blade. The use of the steel cable further reduces the load of the horizontal cross brace, so that the horizontal cross brace can be designed in a lightweight manner, the construction cost of the horizontal cross brace is reduced, and the resistance generated when the horizontal cross brace rotates at a high speed of a fan is reduced.

In addition, the chord length and the width of the variable-section bent blade are synchronously increased along with the reduction of the height, so that the aerodynamic performance of the blade can be improved, the power generation efficiency of the wind turbine is improved, the structural strength of the variable-section bent blade can be increased, and the large-sized blade can bear the gravity of the blade.

Based on the reasons, the invention can be widely popularized in the fields of wind power generation and the like.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings may be obtained according to the drawings without inventive effort to a person skilled in the art.

FIG. 1 is an oblique view of a U-shaped vertical axis wind turbine of the present invention.

FIG. 2 is a partial view of the top end of the main shaft of a U-shaped vertical axis wind turbine of the present invention.

FIG. 3 is a partial view of the central portion of the main shaft of a U-shaped vertical axis wind turbine of the present invention.

FIG. 4 is a partial view of a constant section vertical blade tip of a U-shaped vertical axis wind turbine of the present invention.

FIG. 5 is a partial view of the connection of a horizontal cross brace and a blade of a U-shaped vertical axis wind turbine of the present invention.

FIG. 6 is a partial view of the connection of a variable cross section curved blade and a main shaft of a U-shaped vertical axis wind turbine of the present invention.

FIG. 7 is a diagram illustrating the internal structure of a rotating base of a U-shaped vertical axis wind turbine according to the present invention.

FIG. 8 is a schematic view of a pre-buried metallic structural member within a U-shaped vertical axis wind turbine blade of the present invention.

FIG. 9 is a schematic view of the chord length and radius of a wind wheel of a U-shaped vertical axis wind turbine of the present invention.

FIG. 10 is a schematic view of an endless blade and blade with five different sized end plates installed in an embodiment of the invention.

In the figure: 1a, vertical blades with equal cross sections; 1b, variable cross-section curved blades; 2. a horizontal cross brace; 3a, a blade connecting shaft; 3b a transmission shaft; 4. a wire rope; 5. an upper truss; 6. a lower truss; 7. rotating the base; 8. a generator; 9. a bottom flange; 10. a bearing; 11. a bolt connection pair; 12. a horizontal connecting flange; 13. a hanging ring; 14. an end plate; 15. a vertical connecting flange; 16. pre-burying a metal plate; 17. and embedding the metal rod.

Detailed Description

In order that those skilled in the art will better understand the present invention, a technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in which it is apparent that the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the present invention without making any inventive effort, shall fall within the scope of the present invention.

Example 1

As shown in fig. 1, a U-shaped vertical axis wind turbine mainly comprises a rotating base 7, a main shaft 3 is mounted on the rotating base 7, the main shaft 3 is divided into a blade connecting shaft 3a and a transmission shaft 3b, a plurality of variable cross-section blades 1 are symmetrically arranged in the circumferential direction of the main shaft, and the variable cross-section blades 1 comprise equal cross-section vertical blades 1a positioned at the upper part and variable cross-section bent blades 1b positioned at the lower part.

As a preferred embodiment of the invention, the chord length (the length of the blade in the horizontal plane) and the width of the uniform section vertical blade 1a are unchanged from top to bottom, a lift type blade is adopted, the chord length of the part of the blade is related to the diameter of the wind turbine and is the optimal chord length under the working rotating speed, specifically, the ratio of the chord length to the radius of the wind wheel (the distance between the centroid of the blade in the horizontal plane and the centroid of the main shaft) is smaller than 0.2, and the ratio of the width to the chord length is 0.12-0.25. As a preferred embodiment of the invention, the ratio of chord length to diameter of the wind wheel in this example is 0.04775, and the ratio of width to chord length is 0.18.

As shown in fig. 4, an end plate 14 is attached to the tip of the vertical blade 1a having a uniform cross section, and is a structure having a size larger than that of the blade, and positioned at the tip of the blade. The existence of the end plate can effectively inhibit the tip vortex at the top end of the blade, so that the aerodynamic performance of the blade is improved by 10% at most. As shown in fig. 10, there is a schematic view of an endless blade with five different sized end plates mounted thereto. Where Δ is the distance between the outer edge of the end plate and the outer edge of the blade, c is the chord length of the blade, and the end plate thickness is 0.2c. In numerical simulations, total torque, blade torque, and end plate torque were monitored separately. The work of the blade for the six size end plates was calculated from the torque data as shown in the following figures. The work W is represented by a dimensionless quantity W0, and the total work includes end plate work and blade work. As can be seen from the figure, the blade work tends to increase as the end plate size increases. However, the larger the end plate size, the greater the resistance. The trend of the increase of the total work starts to slow down after the corresponding point of delta=0.35c, and delta=0.35c is taken as the preferred size. At this time, the total work was increased by 4.25% compared to the blade without the end plate.

In order to improve the strength of the uniform-section vertical blade 1a, the uniform-section vertical blade 1a is provided to be connected to the blade connecting shaft 3a through a plurality of horizontal cross braces 2 provided from top to bottom. The connection mode of the horizontal cross brace 2 and the blade connecting shaft 3a is as shown in fig. 2-3, the horizontal cross brace 2 is connected with the horizontal connecting flange 12 through the upper truss 5, and the horizontal connecting flange 12 is fixed on the blade connecting shaft 3a through the bolt connecting pair 11. As shown in fig. 5, the horizontal cross brace 2 is connected to the uniform-section vertical blade 1a by a vertical connection flange 15, and the vertical connection flange 15 is fixed to the uniform-section vertical blade 1a by a bolt connection pair 11. For stabilization, a plurality of equidistant horizontal crossbars can be provided, in particular, a plurality of horizontal crossbars 2 can be provided with various roles including: can provide pulling force to prevent the variable-section blade 1 from collapsing; the displacement of the variable-section blade 1 can be limited when the wind turbine rotates at a high speed, so that the variable-section blade 1 is prevented from being damaged due to the excessively high rotating speed; the maximum bending stress acting on the variable-section blade 1 is reduced, and the strength of the variable-section blade 1 is improved. The horizontal cross brace 2 does not bear the gravity of the variable-section blade 1 and only bears the gravity of the horizontal cross brace and the centrifugal force of the variable-section blade 1, so that the horizontal cross brace can be designed in a lightweight manner, and the construction cost is reduced. As shown in fig. 2 and 4, the main shaft 3 and the variable-section blade 1 are connected by adopting a steel cable 4 besides the connection part of the horizontal cross brace 2, and the steel cable 4 is respectively fixed on the main shaft 3 and the variable-section blade 1 through a hanging ring 13. The steel cable 4 can effectively limit the displacement of the variable cross-section blade 1, share the centrifugal force of the variable cross-section blade 1 born by the horizontal cross-brace 2, and play a role in protecting the horizontal cross-brace 2 and the variable cross-section blade 1.

The connection part of the constant-section vertical blade 1a and the variable-section bent blade 1b is provided with protruding flanges as shown in fig. 5, and the flanges can inhibit the flow separation of air at the connection part of the blades, so that the power generation efficiency of the wind turbine is improved. The two flanges are connected by a bolt connection pair 11.

As a further preferred embodiment of the present invention, the chord length of the variable-section curved blade 1b is increased from top to bottom in equal proportion, and the ratio of the blade width to the chord length is kept constant at 0.18 for every 10% of the wind wheel radius decrease in the blade height, the chord length of the blade is increased by 1.1 times the previous chord length. The structure that the chord length of the variable-section blade is continuously increased from top to bottom can effectively improve the power generation efficiency of the variable-section bent blade 1b, and the power generation efficiency of the optimized blade can be improved by 11.89% under the rated rotation speed after calculation. In addition, such a structure can also enhance the structural strength of the variable-section curved blade 1 b.

The horizontal distance between the variable cross-section bent blade 1b and the main shaft 3 is reduced from top to bottom. As shown in fig. 7, the bottom of the variable-section bending blade 1b is connected with a bottom flange 9 by adopting a lower truss 6, and the bottom flange 9 is fixed on the main shaft 3 through a bolt connection pair 11. The bottom of the variable cross-section bent blade 1b adopts the mode that the lower truss 6 is connected with the bottom flange 9, so that the problem that the variable cross-section bent blade 1b is overlarge in bottom and difficult to install due to the fact that the variable cross-section bent blade is directly connected with the bottom flange 9 can be avoided, and the weight of a rotating part of a fan can be reduced under the condition that the requirement of structural strength is met.

Example 2

On the basis of the embodiment 1, the embodiment 2 provides a U-shaped vertical axis wind turbine adopting a U-shaped vertical axis wind turbine. The U-shaped vertical axis wind turbine comprises a U-shaped vertical axis wind turbine and a motor. The generator is positioned between the variable cross-section blade and the rotating base.

As shown in fig. 7, the lower end of the blade connecting shaft 3a is connected with the upper end of the transmission shaft 3b through a flange, and is fixed by using a bolt connection pair 11. The drive shaft 3b transmits the torque generated by the variable-section blades 1 to the generator 8 to generate electricity. The connection between the two transmits the gravity of the upper end part to the rotating base 7 through the bearing 10. In order to ensure the overall strength of the wind turbine, facilitate the connection of the flange plates and the installation of the steel ropes, the two ends and the inside of the variable-section blade 1 and the horizontal cross brace 2 are embedded with metal structural members.

In order to simplify the lifting process of the vertical axis wind turbine and avoid the difficulty in installing a fan caused by coaxiality errors, in the U-shaped vertical axis wind turbine of the embodiment, the variable cross-section blade 1, the horizontal cross-brace 2 and the main shaft 3 are preferably arranged into an integrated structure, and the structure synchronously rotates when the wind turbine generates power. The radius of the variable-section bent blade 1b is gradually reduced, so that the radius of the root of the U-shaped vertical axis wind turbine is smaller, the requirement of the U-shaped vertical axis wind turbine on the installation height is reduced, and the distance between the root of the blade and the ground during installation is only reserved for the height of the generator.

As shown in FIG. 7, the generator 8 is located between the blades and the rotating base, so that the gravity center of the U-shaped vertical axis wind turbine can be lowered, and the overturning moment generated by the gravity of the U-shaped vertical axis wind turbine when the U-shaped vertical axis wind turbine tilts can be reduced. The generator is not used as a stress piece and is only used as transmission connection; the total weight of the U-shaped vertical axis wind turbine is borne by the bearing 10 of the rotating base. The transmission shaft 3b is connected with the generator rotor through a coupler; the variable-section blade 1, the horizontal cross brace 2 and the main shaft 3 serve as rotors, and the generator shell serves as a stator to generate electricity.

As a preferred embodiment of the invention, the main shaft 3 can be directly inserted into the rotating base bearing 10 and can be fixed in position by means of the gravity of the U-shaped vertical axis wind turbine.

The scheme and effects of the application are further described below by comparing the working effects of the existing wind turbine with those of the wind turbine disclosed by the application. Specifically, the working performance of the fan is evaluated through the generated energy of the fan, wherein the calculation formula of the generated energy of the fan is as follows:

Wherein p is the power generated by the fan, ρ is the air density, A is the wind sweeping area, V is the wind speed C _P and is the wind energy utilization coefficient.

Darrieus type vertical axis fan wind sweeping area calculation formula

S＝H*D*0.657

H-shaped vertical axis fan wind sweeping area calculation formula

S＝H*D

Formula for calculating wind sweeping area of U-shaped vertical axis fan

S＝D*R*0.657+D*(H-R)

Wherein S is the wind sweeping area D of the fan, R is the wind wheel diameter, H is the wind wheel height.

Under the conditions that the product of the wind wheel diameter and the wind wheel height of the vertical axis fan is 25m & lt 2 & gt, the wind speed is 12m/s, and the air density is 1.225kg/m ³, numerical simulation is carried out on three different types of vertical axis fans of Darrieus type, H type and U type, and the power generation power of the three types of vertical axis fans is compared according to the result of the numerical simulation. Wherein Darrieus type and H type vertical axes ratio of height to diameter of fan wind wheel U-shaped vertical axis fan with ratio of 1:1 the ratio of the height to the diameter of the wind wheel is 16:9. As shown in table 1, the parameters of the vertical axis fans of three different types, namely Darrieus type, H type and U type, were used.

Table 1 three fan parameters

As can be seen from Table 1, under the condition that the product of the height and the diameter of the wind wheel is the same, the wind sweeping area of the U-shaped vertical axis wind turbine adopting the U-shaped wind wheel is increased by 37.37% compared with the wind sweeping area of the Darrieus-type vertical axis wind turbine, and is reduced by 10.8% compared with the wind sweeping area of the H-type vertical axis wind turbine. Under the condition that the chord lengths of the blades are consistent, the power generation efficiency of the U-shaped vertical axis wind turbine is approximately equal to that of the Darrieus type vertical axis wind turbine, and compared with that of the H-shaped vertical axis wind turbine, the power generation efficiency of the U-shaped vertical axis wind turbine is improved by 4.96%.

Example 3

Based on embodiment 2, embodiment 3 provides a wind power generation system, which comprises a plurality of U-shaped vertical axis wind turbines as provided in embodiment 2, and each U-shaped vertical axis wind turbine is connected in a grid-connected mode. For embodiment 3 of the present invention, since it corresponds to the technical content in the above embodiment, the description is relatively simple, and the relevant similarities will be found in the description of the above embodiment, and will not be described in detail here.

Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and not for limiting the same; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some or all of the technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the invention.

Claims

1. A U-shaped vertical axis wind turbine, comprising: variable cross-section blade, main shaft, horizontal cross brace and rotating base; a main shaft is vertically arranged on the rotating base; a plurality of variable cross-section blades are symmetrically arranged along the circumferential direction of the main shaft, and each variable cross-section blade comprises a constant cross-section vertical blade and a variable cross-section bending blade from top to bottom in sequence; the constant cross section vertical blades are arranged in parallel with the main shaft, and the bottoms of the variable cross section bending blades are connected with the main shaft; the constant cross section vertical blades are connected with the main shaft through horizontal cross braces, the variable cross section blades are connected with the main shaft through trusses, and the variable cross section blades, the main shaft and the horizontal cross braces synchronously rotate.

2. The U-shaped vertical axis wind turbine of claim 1 wherein the chord length and width of the constant section vertical blades are constant from top to bottom, the ratio of the chord length to the radius of the wind turbine is less than 0.2, and the ratio of the width to the chord length is 0.12-0.25.

3. A U-shaped vertical axis wind turbine as claimed in claim 1 wherein the variable cross section curved blade has a blade chord length which increases from top to bottom in equal ratio: when the height of the blade is reduced by 10% of the radius of the wind wheel, the chord length of the blade is increased by 1.05-1.2 times of the previous chord length, and the ratio of the width of the blade to the chord length is kept unchanged.

4. The U-shaped vertical axis wind turbine of claim 1 wherein the vertical blades of uniform cross section are connected to the main shaft by a plurality of horizontal braces, and wherein all horizontal braces of the same level of blades are on a single horizontal line.

5. The U-shaped vertical axis wind turbine of claim 1 wherein the main shaft comprises a blade connecting shaft and a transmission shaft, the transmission shaft is connected with the blade connecting shaft through a shaft end flange, one end of the blade connecting shaft is connected with the upper end of the variable cross-section blade through a horizontal cross brace, and the other end is connected with the lower end of the variable cross-section blade through a truss.

6. The U-shaped vertical axis wind turbine of claim 4 wherein the upper end of the drive shaft of the main shaft is connected to the lower end of the blade connecting shaft to transmit torque generated by the blades; the connection transmits the gravity of the upper end part to the rotating base through the bearing.

7. The U-shaped vertical axis wind turbine of claim 1 wherein said horizontal cross brace is connected to said main shaft by an upper truss at an end thereof adjacent said main shaft.

8. A U-shaped vertical axis wind turbine as claimed in claim 1 wherein the main shaft is connected to the vertical blades of constant cross section by a plurality of cables, at least one cable being connected between the top of the vertical blades of constant cross section and the main shaft.

9. The U-shaped vertical axis wind turbine of claim 8 wherein the cables are connected to the main shaft and the blades by slings, each slings being connected to 1-2 cables depending on the structural strength requirements of the wind turbine.

10. The U-shaped vertical axis wind turbine of claim 1 wherein the blades are connected with the constant section vertical blades and the variable section curved blades by flanges, and the connection is provided with a horizontal cross brace connecting spindle, so as to strengthen the structure of the connection.

11. The U-shaped vertical axis wind turbine of claim 1 wherein the metal structural members are embedded at both ends of the variable section blades and horizontal cross braces for ensuring overall strength, attachment of the flange and its cables.

12. A U-shaped vertical axis wind turbine comprising a motor and a U-shaped vertical axis wind turbine as claimed in any one of claims 1 to 11.

13. The U-shaped vertical axis wind turbine of claim 12 wherein said motor is located between the variable section blades and the rotating base.

14. The U-shaped vertical axis wind turbine of claim 12 wherein the drive shaft is coupled to the generator rotor by a coupling; when the generator works, the variable cross-section blades, the main shaft and the horizontal cross brace are used as rotors, and the generator shell is used as a stator to generate electricity.

15. A wind power generation system comprising a plurality of U-shaped vertical axis wind turbines according to any of claims 10-12, each of said U-shaped vertical axis wind turbines being connected in a grid-connected relationship.