CN209228541U - Structure for Reducing Vortex-Induced Vibration of Fan Tower - Google Patents

Abstract

The utility model discloses a structure for reducing vortex-induced vibration of a wind turbine tower. The structure can be a sleeve structure surrounded by a single section on the top of the tower as a whole or part of the periphery. The sleeve structure includes a tail for reducing vortex-induced vibration. ; The sleeve structure is set as a flexible sleeve structure and wraps around the top periphery of the tower, or the sleeve structure is set as a rigid sleeve structure and wraps around the top periphery of the tower. In addition, the structure can also be a spiral pipe structure wound on the outer circumference of the top of the tower. An air collection port is provided in the upwind direction, and an air discharge port is provided along the spiral pipe pipe in the downwind direction. Set as the outlet for the wind to flow out of the helical duct. According to the generation mechanism and characteristics of vortex vibration, the utility model changes the flow field distribution of the cylinder wall, and then affects the vortex discharge on the surface of the cylinder wall to avoid or reduce the vortex-induced vibration, in order to reduce the vibration of the tower under the action of wind pressure and avoid the resonance phenomenon .

Description

Structure for Reducing Vortex-Induced Vibration of Fan Tower

technical field

The utility model relates to the field of wind power generation, in particular to a structure for reducing vortex-induced vibration of a wind turbine tower.

Background technique

In recent years, the problem of air quality has become an important issue related to the environment and human health. As a clean and renewable energy, wind energy is increasingly serving human production and life. There are many types of wind power generation devices, mainly horizontal-axis three-blade generators. The power generated by this type of generator is positively correlated with the diameter of the impeller. Therefore, the diameter of the impeller increases with the increase in power generation, and the greater the height, the greater the wind force. The height of wind turbines continues to increase. As shown in Figure 1, the wind turbine is mainly composed of blades, hub, nacelle, tower, transition part and bottom support structure. The tower bears the role of providing effective support for the top structure. MW-level wind turbine towers are often tens to hundreds of meters, limited by many aspects such as manufacturing, transportation, and hoisting capabilities. Towers are generally constructed and installed in sections, and the length of a single section is about 20-30m. For example, sections 01 and 02 shown in Figure 1 section and section 03, where the section 01 tower refers to the top single section or the upper section of the entire tower not exceeding 1/2 the height of the tower.

The slender tower is affected by the wind flow field, and the fluid is blocked by the tower and continues to flow around the tower. At this time, the flow field is changed by the interference of the tower, and the fluid leaves the component due to the influence of the component size, shape, wind speed, roughness, and air viscosity. It will be different from time to time, and under certain conditions, it will form a periodic unbalanced wind pressure effect, which will cause the fan to vibrate, that is, the vortex-induced vibration of the fan. When the period of the unbalanced wind pressure is close to a certain order natural period of the fan as a whole (usually the first-order natural frequency of the fan), the vortex-induced vibration of the fan will be significantly enhanced. The occurrence of vortex-induced vibration will adversely affect the reliability and safety of fan operation. With the increase of wind tower height, vortex-induced vibration has become an inevitable and urgent problem in the industry.

The mechanism and characteristics of vortex vibration are as follows:

(1) When the wind flows through the tower, asymmetrical vortex shedding will occur on both sides of the structure, causing the surface of the structure to be subjected to periodic positive and negative pressures. The frequency of the resultant force on the structure is consistent with the natural frequency of the structure at a certain wind speed , the structure undergoes vortex induced vibration.

(2) Vortex-induced vibration is a kind of simple harmonic vibration, and its vibration form usually manifests as cross-wind vibration or torsional vibration. When the amplitude of the structure is large, the movement of the structure will have a feedback effect on the flow around the gas, so that the frequency of vortex shedding is equal to the natural vibration frequency of the structure within a certain wind speed range, that is, the "locking" phenomenon of vortex induced resonance. "Locking" will increase the probability of vortex-induced vibration of the structure and enhance the correlation of vortex-induced force on the three-dimensional structure. The vortex-induced vibration is a kind of limiting vibration, which is sensitive to the mass and damping of the structure. When the structural mass and damping are small, the vortex-induced resonance amplitude may be large. In the locked region, the vortex shedding frequency no longer obeys the Strouhal relation, but remains at the value of the structural natural frequency. In the locked region, object amplitudes can reach a fraction of the across-wind dimension of the structure.

(3) The relationship between cylindrical vortex induced vibration and Re;

Reynolds number Re represents the relationship between inertial force and viscous force: Re=inertial force/viscous force=(ρ*U ² /L)/(μ*U/L ² )=ρ*U*L/μ=U*L /ν, where, ρ: air density; U wind speed; L structural characteristic scale; μ air viscosity; ν air kinematic viscosity coefficient = 1.5*10 ^-5 m ² /s;

When Re<5: the flow is not separated; when 5～15<Re<40: a pair of stable vortices appear in the wake; when 40<Re<3.0×10 ² : the vortices regularly fall off from the back of the cylinder to form a Karman vortex street; When 3.0×10 ² <Re<3.0×10 ⁵ : the vortex in the subcritical range sheds periodically with a clear frequency; when 3.0×10 ⁵ <Re<3.5×10 ⁵ : the vortex in the critical range is covered by turbulent flow, The vortex shedding is disorderly; when 3.5×10 ⁵ <Re: the vortex is re-established in the supercritical range, and the vortex shedding reappears periodically. Therefore, the shape of the flow around the different Reynolds numbers is different, so the frequency of vortex shedding and the aerodynamic force acting on the structure are also different.

(4) Vortex vibration generation condition: St=f _v *D/U; where, St: Storohal number; U: relative velocity between wind and tower; f _v : vortex shedding frequency; D: tower diameter.

(5) Locking wind speed condition: U=f _v *D/St.

(6) Vortex-induced vibration characteristics: a. It is a limited amplitude vibration that occurs in a certain wind speed area; b. It only occurs in a certain wind speed area; c. The maximum amplitude has a great dependence on structural damping; d. The cross-sectional shape The small change of is very sensitive to the response; e, vortex-induced vibration can excite bending vibration, and can also excite torsional vibration.

As a structural vibration phenomenon caused by periodic dynamic load, vortex-induced vibration will have an adverse effect on the fatigue of the welding points of the wind turbine tower. In addition, when the control strategy of the fan control system cannot be implemented, such as fan installation or shutdown, the occurrence of vortex-induced vibration of the fan will have a very adverse impact on the structural safety of the fan.

Utility model content

The purpose of this utility model is to provide a structure to reduce the vortex-induced vibration of the fan tower. According to the mechanism and characteristics of the vortex vibration, the distribution of the flow field on the wall of the tube is changed, and then the vortex discharge on the surface of the tube wall is affected to avoid or reduce the vortex-induced vibration. Reduce tower vibration under wind pressure and avoid resonance phenomenon.

In order to achieve the above purpose, the utility model provides a spiral pipeline structure for reducing the vortex-induced vibration of the fan tower. The spiral pipeline structure is wound on the outer circumference of the top of the tower. The air outlet, the air collecting opening is set as the inlet of the wind flowing into the spiral pipeline, and the air outlet is set as the outlet of the wind flowing out of the spiral pipeline.

Preferably, in the spiral pipeline structure, the diameter of the winding tube is in the range of 50 mm to 300 mm.

Preferably, in the spiral pipeline structure, the lead distance is set to be 4.5 to 5 times the diameter of the tower.

Preferably, in the spiral pipeline structure, the pitch size is set to one-third of the lead pitch size, so that three winding pipes are juxtaposed within the lead pitch size range.

Preferably, the bottom of the winding pipe is provided with a support chute for limiting the displacement of the winding pipe.

Preferably, the air discharge port is smaller than the air collection port.

Preferably, the air collecting port is in the shape of a bell mouth.

Preferably, the air collecting port is installed separately, or is integrated with the winding pipe.

Preferably, the air discharge hole is directly opened on the back of the air collecting port within a range of not more than 120 degrees, or the air discharge hole is provided on the upper and lower walls of the winding pipe.

Preferably, the diameter of the air discharge holes is smaller than the diameter of the winding pipe, the distance between the air discharge holes is not smaller than the diameter of the air discharge holes, and the sizes of the air discharge holes are equal or unequal.

Compared with the prior art, the beneficial effects of the utility model are as follows: (1) The utility model surrounds a ring sleeve on the whole or part of the periphery of the top of the tower, and the sleeve has a certain shape of the tail, which can improve the tail flow. field, thereby reducing eddy vibration. The upper and lower ends of the sleeve are designed with a specific connection form, which allows the sleeve to slide freely, and can automatically change direction under the action of the wind according to the wing theory to welcome the incoming wind. (2) The sleeve of the utility model can be used as a flexible wrap. Due to the fluid viscosity, it should not be too long. Under the action of the wind, it will automatically fit the tower in the windward direction. Tight back low-pressure area improves back flow field, thereby reducing eddy vibration. (3) The utility model wraps a single-section outer circumference of a spiral pipeline on the top of the tower. An air collection port is provided in the upwind direction, and an air discharge port is provided along the pipeline in the downwind direction to disturb the wake flow in the downwind direction of the tower tube and reduce vortex vibration. .

Description of drawings

The overall schematic diagram of the tower tube and wind turbine of Fig. 1 prior art;

Fig. 2 is a schematic diagram of the structure of the sleeve at the top of the tower in Embodiment 1 of the utility model;

Fig. 3 is a schematic diagram of the connection method of the sleeve at the top section of the tower tube in Embodiment 1 of the utility model;

Fig. 4 is a schematic diagram of the upper connection of the sleeve at the top section of the tower in Embodiment 1 of the utility model;

Fig. 5 is a schematic diagram of the connection of the lower part of the sleeve at the top section of the tower in Embodiment 1 of the utility model;

Fig. 6 is a schematic diagram of the upwind direction in the pipeline structure of the second embodiment of the utility model;

Fig. 7 is a lateral schematic diagram of the pipeline structure of Embodiment 2 of the utility model;

Fig. 7a is a partial side view of A corresponding to Fig. 7 of the present utility model;

Fig. 8 is a schematic diagram of the downwind direction in the pipeline structure of the second embodiment of the utility model;

Fig. 8a is a partial front view of B corresponding to Fig. 8 of the utility model;

Fig. 9 is a schematic diagram of the pitch and lead of the second embodiment of the utility model.

Detailed ways

The utility model discloses a structure for reducing vortex-induced vibration of a fan tower. In order to make the utility model more obvious and easy to understand, the utility model will be further described below in conjunction with the accompanying drawings and specific implementation methods.

Embodiment one:

As shown in Figure 2, the structural design method of the utility model for reducing the vortex-induced vibration of the fan tower is to surround a ring of sleeve 205 on the whole or part of the periphery of the top of the tower. The sleeve 205 has a certain tail shape, which can improve Tail flow field, thereby reducing vortex vibration. The upper and lower ends of the sleeve are designed with a specific connection form, which allows the sleeve to slide freely, and can automatically change direction under the action of the wind according to the wing theory to welcome the incoming wind.

The sleeve can be used as a flexible wrap (that is, similar to thick kraft paper and other materials with a certain degree of flexibility). Due to the fluid viscosity, it should not be too long. The shape of the model avoids the low-pressure area at the tight back, improves the flow field at the back, and reduces eddy vibration.

In this embodiment, the perimeter of the flexible wrapping layer is greater than the perimeter of the corresponding wrapping part of the tower, and its maximum longitudinal extension after any extrusion shape should be less than (1+D)m to ensure that it does not interfere with the impeller under any circumstances. Interference occurs, where D is the maximum diameter of the tower. The wrapping layer is a material with specific flexibility and toughness, and the upper and lower ends can be directly fixed by the upper and lower flanges of the top tower.

The form of the rigid sleeve is shown in Figure 2, and the sleeve is wrapped around the outer circumference of the top section of the tower. The upwind end is ring-shaped, as close as possible without touching the tower wall, and the appropriate spacing distance is determined according to conditions such as construction accuracy and material stiffness. The downwind end is provided with a certain airfoil or direct prism treatment. In the height direction, any section of the sleeve is shown as an airfoil section shape or a combination of a circle and a triangle.

The maximum projected length of the sleeve in the circumferential direction should ensure that there is no interference with the blade and a certain safety distance should be left. The largest sleeve can be wrapped as a whole or in sections. The upper and lower ends of the rigid sleeve are fixed with a certain structure, which can ensure that the rigid sleeve can rotate freely under the action of wind pressure to automatically align with the wind direction.

(1) Connection method 1 at the end of the sleeve, as follows:

In this embodiment, the upper and lower ends of the sleeve can be fixed as shown in FIG. 3 .

2 and 3, 201 is the outer wall of the tower, 202 is the connection and extension part of the tower, 203 is the connector slide rail part, 205 is the sleeve, and 206 is the connecting section at the end of the sleeve.

The connector slide rail part 203 belongs to the tower extension part, and is fastened to the tower outer wall 201 through the tower connection and the extension part 202 . The shape of the connector slide rail portion 203 can be spherical, or protruding in other shapes.

In this embodiment, the tower connection and extension part 202 and the connector slide rail part 203 form a continuous track around the tower to ensure that the sleeve 205 can slide freely through the slide rail structure under the action of wind pressure. Specifically, the tower connecting and overhanging portion 202 and the connector sliding rail portion 203 jointly constitute a sliding rail, and the two are connected by welding or can be manufactured as an integral casting. The slide rail is welded to the tower outer wall 201 through the tower connection and the overhanging part 202 , and forms a slideway through the outer surface of the connector slide rail part 203 and the sleeve end connection section 206 . The slide rails are only set on the top and bottom of the sleeve, and the top and bottom have the same structure. The position of the slide rails is shown at point P in Figure 2.

The connecting section 206 at the end of the sleeve can be continuous as the connecting part of the sleeve, or only a few pieces can be arranged relatively evenly along the circumference, so as to effectively connect and support the weight of the sleeve 205 .

The junction part 204 of the sleeve and the tower is the contact surface of the connector slide rail part 203 and the connecting section 206 at the end of the sleeve. or smooth contact. At this time, lubricate the contact surface to reduce the friction between the contact surfaces, ensure the smooth sliding of the sleeve 205 along the slideway through the connecting section 206 (ie the connector) at the end of the sleeve, and ensure that the sleeve 205 can go up under the action of wind force. The wind direction (round head part) is upwind, and the leeward direction (sharp part) is located in the wake area. In addition, the junction part 204 of the sleeve and the tower can also be used as a magnetic connection, so that the two do not need to be in contact, and the friction between the contact surfaces is reduced through the repulsion of the magnetic poles, that is, the free sliding and reliable connection of the slide rail are ensured by using gravity and magnetic repulsion. .

In this embodiment, frictional resistance and wear on materials should be reduced as much as possible, and continuous optimization and improvement can be carried out through certain materials, processing techniques, and structural optimization.

(2) Sleeve end connection method two:

The slide rail of the utility model can be used as a magnetic guide rail to minimize the friction of the slide rail. As shown in Figure 4 and Figure 5, this is another slide rail design method for the connection between the sleeve and the tower, but the utility model is not limited to this cross-sectional structure.

211 is the sleeve at the top connection shown in Figure 4; 210 is the top end of the sleeve, which is used to cooperate with the slide rail; 212 is the slide rail, one end is connected with the tower, the other end is the slide rail track, and the bottom It is supported and strengthened by reinforcing member 215 (flat iron); 213 is the outer wall of the tower tube.

The track groove of the slide rail 212 and the three surfaces matched with the top end of the sleeve 210 are made into magnetic surfaces, that is, the inner and outer surfaces and the lower end surface of the top end of the sleeve 210 in contact with the slide rail 212 are set as magnetic force surfaces, and along the tower The circumference of the barrel is continuous for one week.

The sleeve bottom end 209 is of the same structure as the sleeve top end 210 . In the same way, the three surfaces where the track groove of the slide rail 214 cooperates with the sleeve bottom end 209 are made into magnetic force surfaces, that is, the inner and outer surfaces and the upper end surface of the sleeve bottom end 209 in contact with the slide rail 214 are set as magnetic force surfaces. noodle. In this embodiment, the three magnetic surfaces at the bottom of the sleeve and the three magnetic surfaces at the top of the sleeve form three pairs of magnetic repulsion surfaces, and then the upper and lower sets of guide rails cooperate with the upper and lower end surfaces of the sleeve to form a composition as shown in Figure 4 and Figure 5 Three groups of repulsive forces: force 1 and force 1', force 2 and force 2', force 3 and force 3'.

Among them, force 1 and force 1' constitute a pair of horizontally balanced repulsive forces of equal magnitude and opposite directions; force 2 and force 2' constitute a pair of horizontally balanced repulsive forces of equal magnitude and opposite directions. Since the closer the relative distance between the magnets, the greater the repulsive force, when the distance between the repulsive force surfaces of force 1 decreases, the repulsive force will increase the distance, and when the distance between the repulsive force surfaces of force 1' decreases, the repulsive force of the contact surface of force 1' will increase The greater the repulsive force, the greater the distance, finally reaching a relatively balanced position between the two sides of the top end of the sleeve 210 and the slide rail, and a gap is always maintained to avoid friction.

Force 3 and force 3' are a pair of balanced repulsive forces in the vertical direction, but since gravity is greater than the magnetic force, the pair of contact surfaces where force 3 is located often needs to be specially treated, adding lubrication, grinding rounded corners, or increasing force 3 if conditions permit The surface repulsion force can balance the sum of the two forces of the gravity and the force 3' surface, so that the whole slide rail can slide relative to each other without friction under the action of wind force.

As shown in Fig. 3 and Fig. 4, 215 and 216 are respectively upper and lower rail structure support reinforcement members, which can be continuously welded in one circle along the circumference of the tower and distributed evenly along the outer circumference of the tower intermittently.

To sum up, in the above two sleeve end connection forms of the first embodiment (as shown in Fig. 3 and Fig. 4, 5), the track is arranged as a circular structure along the circumference of the tower (the first form passes through The tower connection and the overhanging part 202 are realized; in the second form, the top is realized by the slide rail 212 and one end of the upper rail structural support reinforcement member 215, and the bottom is realized by the track 214 and one end of the lower rail structural support reinforcement member 216) can be directly connected with the tower Tube welded connection or use the taper of the tower itself to tightly socket under the action of the sleeve's own weight, or local spot welding connection; it can also be connected by optimizing the contact position structure.

Embodiment two:

As shown in Fig. 6, Fig. 7 and Fig. 8, in the second embodiment, a spiral pipe is wound around the outer circumference of a single section on the top of the tower, and an air collection port is provided in the upwind direction, and an air discharge port is provided along the pipe in the downwind direction to disturb the tower. The wake flow in the downwind direction of the tube can reduce the vortex vibration.

Among them, the air collecting port is the entrance for wind to flow into the spiral pipe, and should have a large opening to facilitate more air to flow into the spiral pipe. The air discharge port is the outlet for the wind to flow out of the spiral pipe, and should be smaller than the air collection port, so that the air flow has a greater flow rate than the wake to rush out of the spiral pipe.

The above is an application of the Bernoulli equation, according to the Bernoulli equation:

In the formula, p is the pressure of a certain point in the fluid; v is the fluid flow velocity at this point; ρ is the fluid density; g is the acceleration of gravity; z is the height of the point; C is a constant.

Based on the above and taking the bottom pair of entrances and exits as an example and assuming that the entrance is above the exit, it can be obtained:

In the formula, ν _in is the velocity of the fluid at a certain place at the inlet; p _in is the pressure at the fluid inlet; ρ is the density of the fluid; g is the acceleration of gravity; z _in is the height of the inlet; ν _out is the velocity of the fluid at a certain place at the outlet ; p _out is the pressure at the fluid inlet; z _out is the height of the outlet.

Due to the viscosity of the wind, a boundary layer is formed on the surface of the tower when it flows along the wall of the tower, and the separation of the boundary layer at a position at a certain angle with the inflow causes turbulence and sticky vortices on the back of the tower, so the pressure on the leeward side of the tower Decrease rapidly, that is, p _in > p _out . And for the fluid, the potential energy increases and the kinetic energy is insufficient when it flows upwards, so more wind will flow to the lower place more easily, so the upper air collection port and the lower adjacent air discharge port are regarded as a pair of inlets and outlets, Z _in > Z _out , so v _out >v _in The greater velocity of the gas rushing out can disturb the wake and destroy the original flow field.

The concrete design method of present embodiment two is as follows:

The winding pipe diameter of the spiral pipeline is selected from the range of 50-300mm.

As shown in Figure 9, in the spiral pipeline, the size of the lead hw is about 4.5 to 5 times the diameter of the tower, and three winding pipes can be juxtaposed within the size range of the lead hw, so the screw pitch lw is one-third of the lead hw one.

In the second embodiment, light materials can be used to reduce the gravity, and there is a small distance between the pipe wall and the cylinder wall, and a certain method can also be used for wear-resistant treatment. The top of the winding pipe can be connected with the top cabin and rotate with the rotation of the impeller, so that the air collecting port is always in the upwind direction, and the air discharge port is in the downwind direction. A support chute can be provided at the bottom of the winding pipe to limit its displacement.

The main characteristic of the air collecting port is the shape of a bell mouth, and the opening of the bell gradually narrows toward the connection. A more effective air collection device, such as an impeller, can be arranged in the bell mouth, so that the injected wind can flow into the winding pipe more effectively. In addition, the air collecting port can be installed separately or integrated with the winding tube.

As shown in Figure 8a, the vent hole can be directly opened within a range of not more than 120 degrees on the back of the air collecting port, the diameter of the vent hole is smaller than the diameter of the winding pipe, and the distance between the vent holes is not less than the diameter of the vent hole. The number of vent holes should not be too many, and the size can be equal or not necessarily equal, and vent holes can also be set on the upper and lower walls of the winding pipe.

Although the content of the present invention has been described in detail through the above preferred embodiments, it should be recognized that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions of the present utility model will be obvious to those skilled in the art after reading the above content. Therefore, the protection scope of the present utility model should be defined by the appended claims.

Claims (10)

1. A spiral pipeline structure for reducing vortex-induced vibration of a wind turbine tower, characterized in that the spiral pipeline structure is wound around the outer circumference of the tower top, the upwind direction is provided with an air collection port, and the downwind direction is provided with a discharge outlet along the spiral pipeline. A tuyere, the air collecting opening is set as an inlet for wind to flow into the spiral pipeline, and the air outlet is set as an outlet for wind to flow out of the spiral pipeline. 2. A kind of helical pipeline structure that reduces the vortex-induced vibration of the fan tower as claimed in claim 1, characterized in that, In the spiral pipeline structure, the diameter of the coiled pipe ranges from 50mm to 300mm. 3. A kind of spiral pipeline structure that reduces the vortex-induced vibration of fan tower as claimed in claim 1 or 2, is characterized in that, In the spiral pipeline structure, the guide distance (hw) is set to be 4.5 to 5 times the diameter of the tower. 4. A kind of helical pipeline structure that reduces the vortex-induced vibration of the fan tower as claimed in claim 3, characterized in that, In the spiral pipeline structure, the pitch (lw) is set to be one-third of the size of the lead (hw), so that three winding pipes are juxtaposed within the size range of the lead (hw). 5. A kind of helical pipeline structure that reduces the vortex-induced vibration of the fan tower as claimed in claim 2, characterized in that, A supporting chute for limiting the displacement of the winding pipe is provided at the bottom of the winding pipe. 6. A spiral pipeline structure for reducing vortex-induced vibration of a wind turbine tower as claimed in claim 1, characterized in that, The air discharge port is smaller than the air collection port. 7. A kind of spiral piping structure for reducing vortex-induced vibration of fan tower as claimed in claim 1 or 6, characterized in that, The air collecting port is bell-shaped. 8. A kind of helical pipeline structure that reduces the vortex-induced vibration of the fan tower as claimed in claim 2, characterized in that, The air collecting port is installed separately, or is integrated with the winding pipe. 9. A spiral piping structure for reducing vortex-induced vibration of a wind turbine tower as claimed in claim 2, characterized in that, The air discharge port is directly set within the setting range on the back of the air collection port, or the air discharge port is arranged on the upper and lower walls of the winding pipe. 10. A spiral pipeline structure for reducing vortex-induced vibration of a wind turbine tower as claimed in claim 2 or 9, characterized in that, The diameter of the air outlet is smaller than the diameter of the winding pipe, the hole distance of the air outlet is not smaller than the diameter of the air outlet, and the sizes of the air outlets are equal or unequal.