CN103291540B - The vertical axis windmill that prismatic blade camber line overlaps with wind wheel running orbit - Google Patents

Abstract

The invention discloses the vertical axis windmill that a kind of prismatic blade camber line overlaps with wind wheel running orbit, arc bending line and the wind wheel of vane airfoil profile run circular trace and overlap, and blade upper and lower blade tip place aerofoil profile chord length reduces gradually; Every root blade is connected by two struts with between wind energy conversion system main shaft, makes blade and main axis parallel and can around main axis.Blade of vertical axis wind turbine of the present invention compared with traditional prismatic blade, torque peak and wind energy utilization high, down wind pneumatic thrust reduce.The application of the type wind energy conversion system and popularization, the electric energy being conducive to promoting unit wind energy conversion system exports and increases the service life.

Description

Vertical axis wind turbine with straight blade airfoil camber line coincident with the running track of the wind rotor

technical field

The invention relates to a blade of a vertical axis wind power generator, which adjusts the airfoil and geometric shape of the blade to increase the utilization rate of wind energy of the blade, slow down the aerodynamic thrust in the downwind direction, and prolong the service life of the wind power machine, belonging to the technical field of wind power generation equipment.

Background technique

Vertical axis wind turbines are divided into drag type and lift type. The resistance type wind turbine mainly uses the pressure difference formed by the airflow between the front and back of the blade to drive the impeller to work, such as the wind cup type wind wheel. This type of wind turbine is symmetrically installed on both sides of the rotating shaft by two hemispherical surfaces, and the directions of the spherical surfaces are opposite. When subjected to horizontal wind, the wind resistance of the concave surface is 3 to 4 times greater than that of the convex surface, and the torque difference on both sides is the output torque of the wind turbine. However, the maximum linear speed of this type of wind turbine is close to the wind speed, the tip speed ratio λ is usually less than 1, and the reverse torque generated by the blades in the upwind area reduces the total torque of the rotating shaft, so the utilization rate of wind energy is low.

In the lift-type wind turbine represented by the Φ-type Darrieus wind turbine, the blade section is introduced into the lift-shaped airfoil, which ensures that the airflow in the downwind area is also blown to the leading edge of the airfoil during high-speed rotation, generating sufficient lift to maintain power output. Usually, the optimum tip speed ratio of this type of wind turbine is maintained at about 4, and the wind energy utilization rate is 0.3. In recent years, the Darrieus wind turbine with linear blades, that is, the H-type wind turbine has attracted more and more attention in the international wind energy field. Compared with the Φ-type, the H-type wind turbine has the characteristics of large starting torque and high wind energy utilization. Therefore, countries such as Europe, America, Canada and Japan are actively researching and promoting this kind of wind turbine.

Through the retrieval of research literature on vertical axis wind turbines at home and abroad, most of the H-type wind turbine blades currently adopt the classic aviation airfoil, and the cross-sectional shape of the blades is consistent. However, the running track of the vertical axis wind turbine rotor is circular. If the straight airfoil is not trimmed, its operation effect is equivalent to that in the advection airflow, the tail of the airfoil is warped upwards, and the effective aerodynamic effect of the airfoil cannot be exerted. And the attached vortex on the blade surface moves to the blade tip and extends downstream. The blade tip vortex is one of the main reasons for the decrease of blade efficiency and the increase of fatigue load.

A literature search of the prior art found that there is no public report on improving the camber and tip of the airfoil of the vertical axis wind turbine to increase the wind energy output of the wind turbine and reduce the aerodynamic load.

Contents of the invention

technical problem to be solved

The technical problem to be solved by the present invention is to adjust the camber line of the straight blade airfoil of the vertical axis wind turbine so that it coincides with the running track of the wind rotor, and to modify the chord length of the blade tip airfoil, thereby increasing the peak torque output of the blade during operation , increase the utilization rate of wind energy, reduce the aerodynamic load in the downwind direction, reduce the fatigue load of key parts of the wind turbine, and prolong the service life.

Technical solutions

The present invention adopts following technical scheme in order to realize above-mentioned invention object:

According to the chord length of the blade airfoil and the rotation radius of the wind rotor, adjust the camber of the airfoil so that the camber line of the airfoil coincides completely with the running track of the wind rotor. At the same time, the relative thickness of the airfoil and the appropriateness of the rotor are kept consistent with the original blade. That is, the arc camber line of the blade airfoil coincides with the circular trajectory of the wind rotor, and the chord length of the airfoil at the upper and lower blade tips of the blade gradually decreases; each blade is connected to the main shaft of the wind turbine by two support rods, so that the blade and the main shaft Parallel and rotatable around the main axis.

The chord length of the airfoil at both ends of the blade gradually decreases to the blade tip, and the decreasing trend shows a curve change characteristic.

At the 1/10 cross-section at both ends of the blade, the chord length of the airfoil gradually decreases until it reaches the blade tip.

The longitudinal 1/3 and 2/3 interfaces of the blade are respectively rigidly connected with a support rod, and the connection is at the aerodynamic center of the 1/4 chord length of the blade airfoil.

The support rod is connected with the main shaft of the wind turbine through a bearing.

The camber adjustment of the airfoil is determined by the chord length of the airfoil and the rotating diameter of the rotor.

The relative thickness of the adjusted airfoil and the solidity of the impeller remain unchanged.

The airfoil with reduced chord length is consistent with the shape of the airfoil in the middle of the straight blade, and the aerodynamic center is on the same straight line.

Beneficial effect

The beneficial effects of the present invention are:

The invention adjusts the camber line of the blade airfoil to make it consistent with the running track of the wind rotor, while keeping the relative thickness of the airfoil and the solidity of the wind rotor unchanged, so that the airfoil can exert the aerodynamic force of the original straight airfoil in the advection flow effect. Correcting the chord length of the blade tip airfoil can reduce the vortex intensity dragged by the blade tip. From the perspective of aerodynamics, the overall optimized blade improves the peak torque output of the blade, improves the utilization rate of wind energy, and at the same time slows down the aerodynamic thrust in the downwind direction, reduces the fatigue load of key components, and prolongs the service life of the wind turbine.

Description of drawings:

Figure 1 isometric view of the vertical axis wind turbine where the camber line of the straight blade airfoil coincides with the running track;

Figure 2 is a comparison of the airfoil with the camber line coincident with the trajectory and the initial NACA0015 airfoil;

Fig. 3 is a schematic diagram of the airfoil position arrangement in the middle of the airfoil blade at the blade tip;

Figure 4 is a front view of the blade where the camber line of the airfoil coincides with the running track.

Detailed ways:

The specific embodiment of the present invention will be further described below in conjunction with the accompanying drawings.

Embodiment 1: The present invention takes a vertical axis wind turbine with a rated power of 3.5kw as an example. The vertical axis wind turbine includes a foundation 5, a main shaft 3 standing on the foundation, two bearings 4 arranged separately on the main shaft, and the bearing 4 Two layers of four horizontal support rods 2 are distributed at right angles, and four straight blades 1 are fixedly connected with two support rods in the same direction, see Figure 1.

Foundation 5 is a reinforced concrete structure with a built-in generator. When the wind turbine is installed, the foundation platform is required to be parallel to the horizontal plane.

The main shaft 3 is a stainless steel pipe, the bottom end of which is welded to the foundation 5, the steel pipe is hollow inside, and the built-in rotor connects the wind wheel and the generator in the foundation.

One end of the wind turbine support rod 2 is connected to the bearing 4 on the main shaft, and the other end is rigidly connected to the blade 1 . The connecting position with the blade is 1/3 and 2/3 of the longitudinal length of the blade, and the diameter of the wind wheel formed in this embodiment is 2500 mm. The connection position between the support rod 2 and the blade 1 is at the aerodynamic center of the 1/4 chord length of the section airfoil. The support rod 2 is made of oval stainless steel.

Specific implementation mode 2: In this embodiment, the standard airfoil NACA0015 of American Airlines is selected as the initial airfoil as an example, and the chord length of the airfoil is set to 400mm. The camber line of the airfoil is the line between the midpoints of the distance between the upper and lower arcs perpendicular to the chord line, adjust the camber of the airfoil (the maximum vertical distance from the camber line to the chord line), so that the camber line coincides with the running circle of the aerodynamic center of the blade airfoil, while ensuring that the relative thickness and chord length of the airfoil remain unchanged, see Figure 2.

Specific embodiment three: set the length of the straight blade to 3000mm. The position where the chord length of the airfoil is reduced is within the range of 150 mm in length at both ends of the blade, and the chord length of the airfoil at the blade tip is 20 mm. Attached Figure 3.

Combining numerical simulation and experimentation, the chord length of the airfoil at both ends of the above-mentioned blades is constantly adjusted, as shown in Figure 4, to reduce the vorticity intensity of the tip of the running blade and optimize the aerodynamic performance of the wind turbine.

Claims (8)

1. the vertical axis windmill that overlaps with wind wheel running orbit of prismatic blade camber line, it is characterized in that, arc bending line and the wind wheel of vane airfoil profile run circular trace and overlap, and blade upper and lower blade tip place aerofoil profile chord length reduces gradually; Every root blade is connected by two struts with between wind energy conversion system main shaft, makes blade and main axis parallel and can around main axis.

2. the vertical axis windmill that overlaps with wind wheel running orbit of prismatic blade camber line according to claim 1, is characterized in that: the chord length of blade two ends taper aerofoil profile is reduced to blade tip gradually, reduces the curved variation characteristic of trend.

3. the vertical axis windmill that overlaps with wind wheel running orbit of prismatic blade camber line according to claim 1 and 2, is characterized in that: at blade two ends taper 1/10 section, the chord length of aerofoil profile reduces gradually, until blade tip.

4. the vertical axis windmill that overlaps with wind wheel running orbit of prismatic blade camber line according to claim 1, it is characterized in that: in longitudinally 1/3 and 2/3 interface of blade, be rigidly connected with a strut respectively, and joint is in the aerodynamic center at 1/4 chord length place of vane airfoil profile.

5. the vertical axis windmill that overlaps with wind wheel running orbit of prismatic blade camber line according to claim 1, is characterized in that: described strut is connected by bearing with wind energy conversion system main shaft.

6. the vertical axis windmill that overlaps with wind wheel running orbit of prismatic blade camber line according to claim 2, is characterized in that: the camber adjustment of aerofoil profile is determined by aerofoil profile chord length and wind wheel rotating diameter.

7. the vertical axis windmill that overlaps with wind wheel running orbit of prismatic blade camber line according to claim 2, is characterized in that: the relative thickness of airfoil after adjustment and impeller solidity remain unchanged.

8. the vertical axis windmill that overlaps with wind wheel running orbit of prismatic blade camber line according to claim 3, is characterized in that: the aerofoil profile that chord length reduces is consistent with air foil shape in the middle part of prismatic blade, and aerodynamic center is on same straight line.