CN107882678B - A kind of improved level axis wind energy conversion system and its application method, design method - Google Patents

Abstract

An improved horizontal-axis wind turbine, its use method, and design method mainly include a device for increasing the power generation of the wind turbine, and a hybrid design method using an immersed boundary method coupled with actuation theory. With the large-scale development of wind turbines, the power loss near the blade root of the wind rotor is becoming more and more obvious. By designing a diversion disk device that can move forward and backward, separate and merge, the flow field near the blade root of the wind turbine can be changed to improve the efficiency of the wind turbine. The effect of generating power; facing the aerodynamic shape and size of the device is its key design problem, if the engineering method is used, there is a disadvantage of low accuracy, if the traditional computational fluid dynamics method is used, the calculation amount is large, therefore, the present invention also aims at this For the design of the device, the numerical simulation method of the mixed actuation theory of the immersed boundary method is proposed, which can greatly improve the calculation efficiency while ensuring the calculation accuracy of the numerical simulation.

Description

An improved horizontal axis wind turbine and its use method and design method

technical field

The invention belongs to the field of wind turbines, and in particular relates to an improved horizontal axis wind turbine, its use method and design method.

Background technique

With the large-scale development of horizontal axis wind turbines, the area of the blade root is getting larger and larger. In order to meet the structural strength requirements of the blade root, the blades are basically in a nearly cylindrical shape, resulting in low wind energy utilization. Therefore, the power generation of the entire wind turbine will be reduced. . Aiming at the research on the devices for increasing the power generation of horizontal axis wind turbines, domestic and foreign scholars have carried out a lot of research work on them, such as variable leading edge devices, variable trailing edge devices, vortex generator devices, and blade tip winglet devices on the blades. Wait. These devices all need to modify the blades, which weakens the strength of the blades and increases the cost of the blades. Its supporting design method, engineering application mainly adopts the method of leaf element momentum theory, which has the characteristics of fast calculation speed but low design accuracy; at the same time, due to the problems of large calculation amount and low calculation efficiency of traditional computational fluid dynamics method, only verification and mechanism Research is difficult to apply in engineering design, especially involving aerodynamic shape optimization design. Most importantly, the engineering method of leaf element momentum theory cannot realize the design of the present invention, and the traditional CFD method has low calculation efficiency.

Contents of the invention

Aiming at the deficiencies in the prior art, the present invention provides an improved horizontal axis wind turbine, its use method and design method. The wind turbine has a deflector disc device that can actively control the function, and because the device is integrated with the wind turbine, the traditional engineering design method cannot realize its engineering design function for the overall coupling design. A high-precision and high-efficiency numerical simulation design method for the device.

To achieve the above object, the present invention adopts the following technical solutions:

An improved horizontal axis wind turbine is characterized in that it includes: a tower, a nacelle, blades, a hub, a shroud and a deflector disk, the nacelle is installed on the top of the tower, and the hub is installed on the top of the nacelle At the front end, a plurality of blades are uniformly distributed around the hub, the deflector cover is mounted on the side of the hub, and the deflector disk is telescopically mounted on the front end of the hub.

In order to optimize the above technical solutions, the specific measures taken also include:

The front end of the hub is equipped with a disc fixed base plate, and the disc fixed base plate is sequentially installed with a hydraulic pump, a telescopic oil cylinder and a telescopic piston rod fixed on the front end of the telescopic piston rod, wherein the telescopic piston rod is perpendicular to the wind wheel The plane, the disc fixed base plate and the guide disc are parallel to the plane of the wind wheel.

The guide disc includes an upper half disc, a lower half disc, a rotating mechanism and a support rod, and the support rod is fixed on the front end of the telescopic piston rod perpendicularly to the telescopic piston rod, and the upper half disc and the lower half disc The half discs are respectively installed at both ends of the support rod, and the upper half disc and the support rod, and the lower half disc and the support rod are connected by a rotating mechanism, and the rotating mechanism is used to drive the upper half disc and the lower half disc. Separation and merging of the half discs; in the merged state, the upper half disc and the lower half disc are spliced into a circle parallel to the plane of the wind wheel; in the separated state, the upper half disc and the lower half disc are parallel to each other, and both perpendicular to the plane of the rotor.

A disc fixing bracket is installed between the guide disc and the disc fixing base plate, the disc fixing bracket includes a connecting rod and a slot, the connecting rod is parallel to the supporting rod, and both ends of the connecting rod are installed There are slots, and the openings of the slots face the guide disc, so that when the guide disc is in a separated state, the upper half disc and the lower half disc can be respectively inserted backward into the slots at both ends of the connecting rod.

In addition, a method for using the improved horizontal axis wind turbine is also proposed, which is characterized in that it includes the following steps:

Step 1: When it is detected that the average wind speed for a certain period of time is less than the rated wind speed, the diversion disc is in a combined state, and the hydraulic pump and telescopic cylinder drive the telescopic piston rod to move, so that the diversion disc and the plane of the wind wheel are at the average wind speed. Optimal distance position;

Step 2: When it is detected that the average wind speed for a certain period of time is greater than or equal to the rated wind speed, the diversion disc is in a separated state, the rotating mechanism starts to work, and the upper half disc and the lower half disc rotate and separate until they are both perpendicular to the plane of the wind rotor ;

Step 3: The hydraulic pump and telescopic oil cylinder work, so that the telescopic piston rod approaches the plane of the wind wheel until the upper half disc and the lower half disc are respectively inserted into the slots at both ends of the connecting rod to realize the tightened and fixed state of the disc;

Step 4: When the average wind speed is detected to be lower than the rated wind speed, perform the above operations in reverse.

And the design method of this improved horizontal axis wind turbine, it is characterized in that, comprises the steps:

Step 1: Carry out grid division of the flow field, and perform grid refinement on the position of the diversion disk and the position of the wind wheel;

Step 2: Combine the genetic optimization algorithm to calculate the radius of the diversion disc, the distance between the diversion disc and the wind wheel;

Step 3: Calculate the aerodynamic force of the wind turbine diversion disc through the body force coupling solution of the immersion boundary and the actuation theory;

Step 4: Calculate the power coefficient of the wind turbine at the wind speed based on the aerodynamic force of the diversion disk, and judge whether the power coefficient of the wind turbine is optimal. If the optimal power coefficient of the wind turbine is not reached, change the diversion disk again The radius of the guide disc and the distance between the wind wheel;

Step 5: Perform optimization iterations. If the power coefficient of the wind turbine reaches the maximum value and the optimization has converged, then the optimal radius of the diversion disc and the optimal distance between the diversion disc and the wind wheel are obtained.

The third step specifically includes:

Propose the NS equation expression that is suitable for the numerical simulation calculation of this invention wind turbine device:

Among them, the virtual term f _i represents the external force arising from the existence of the boundary of the object, and the items on the right side of the equation except this item are comprehensively expressed as RHS; U _i and U _j are expressed as velocity tensors, and x _i and x _j represent displacements Components, i, j=1, 2, 3; t is discrete time, v represents fluid viscosity coefficient, v _t is dynamic viscosity coefficient;

The velocity of the equation coordinates is discretized into the following formula:

Among them, n and n+1 represent the relationship before and after the time step;

Through the transmission relationship between speed and force in the above formula, combined with the known speed of the surface of the object Find the magnitude of the external force:

in, Indicates the magnitude of the external force, f _AD indicates the body force of the wind rotor blade, ρ is the air density, c is the chord length of the blade element, CL and CD are the lift coefficient and drag coefficient respectively;

The obtained external force is repeatedly substituted into the momentum equation coupled with the body force of the immersed boundary and the theoretical body force of the actuation to calculate a new velocity field, and the new velocity field is updated with the external force, and so on until the result meets the accuracy requirements.

The beneficial effect of the present invention is: design the diversion disc device of the improved wind turbine with improved power generation of the wind rotor, through the diversion disc device in the upstream direction of the wind rotor, change the flow field characteristics near the blade root of the wind rotor, And even the characteristics of the flow field of the entire blade, thereby achieving the improvement of the utilization efficiency of the entire wind rotor. At the same time, for the special case of engineering design where the device is coupled with the wind rotor, a corresponding hybrid design method of immersion boundary and actuation theory is given. Due to the traditional engineering wind turbine blade element theory design method, it is unable to solve the coupling design of the guide disc and the wind turbine, and the traditional computational fluid dynamics method has a large amount of calculation, which is not suitable for the engineering design of the device. Therefore, based on the hybrid method designed in the present invention, the key parameter design problem of high precision and high efficiency of the diversion disc device is solved.

Description of drawings

Fig. 1 is a schematic diagram of the overall structure of the present invention in a combined state.

Fig. 2 is an overall front view of the present invention in a combined state.

Fig. 3 is a schematic diagram of the overall structure of the present invention in a separated state.

Fig. 4 is an overall front view of the present invention in a detached state.

5a-5d are partial schematic views of the present invention in a combined state.

6a-6d are partial schematic diagrams of the present invention in a separated state.

7a-7b are grid diagrams of the numerical simulation of the diversion disk of the present invention.

Fig. 8 is a flow chart of the design method of the diversion disk of the present invention.

Fig. 9 is a flow field contrast velocity cloud diagram of a 2.5MW wind turbine with a wind speed of 10m/s and whether a diversion disk is installed or not.

Fig. 10 is a graph of the blade axial velocity curve of the 2.5MW wind turbine blade with a wind speed of 10m/s whether or not to install a deflector disc.

Reference signs are as follows: tower 1, engine room 2, blade 3, wheel hub 4, shroud 5, diversion disk 6, disk fixed bottom plate 7, hydraulic pump 8, telescopic oil cylinder 9, telescopic piston rod 10, upper half Disc 11, lower half disc 12, rotating mechanism 13, support rod 14, disc fixed bracket 15, connecting rod 16, slot 17.

Detailed ways

The present invention is described in further detail now in conjunction with accompanying drawing.

The improved horizontal axis wind turbine shown in Figure 1 includes: a tower 1, a nacelle 2, blades 3, a hub 4, a shroud 5 and a deflector disc 6, the nacelle 2 is installed on the top of the tower 1, and the hub 4 is installed at the front end of the nacelle 2, a plurality of blades 3 are evenly distributed around the hub 4, and the shroud 5 is installed on the side of the hub 4. The front end of the wheel hub 4 is equipped with a disc fixed base plate 7, and a hydraulic pump 8, a telescopic oil cylinder 9 and a telescopic piston rod 10 are successively installed on the disc fixed base plate 7, and the hydraulic pump 8 provides power for the telescopic function of the guide disc 6, and the telescopic The piston rod 10 realizes the control of the plane distance between the guide disk 6 and the wind wheel. The guide disk 6 is fixed on the front end of the telescopic piston rod 10, wherein the telescopic piston rod 10 is perpendicular to the plane of the wind wheel, and the fixed base plate 7 of the disc and the guide disc 6 are parallel to the plane of the wind wheel.

Referring further to Fig. 2-4, the guide disc 6 includes an upper half disc 11, a lower half disc 12, a rotating mechanism 13 and a support rod 14, and the support rod 14 is fixed on the telescopic piston rod 10 perpendicular to the telescopic piston rod 10. The front end of the upper half disc 11 and the lower half disc 12 are installed on the two ends of the support rod 14 respectively, between the upper half disc 11 and the support rod 14, between the lower half disc 12 and the support rod 14, all through the rotation The mechanism 13 is connected, and the rotating mechanism 13 is used to drive the separation and merging of the upper half disc 11 and the lower half disc 12 . In the merging state shown in Fig. 1 and Fig. 2, the upper half disc 11 and the lower half disc 12 are spliced into a circle parallel to the plane of the wind rotor. In the separated state shown in Fig. 3 and Fig. 4, the upper half disc 11 and the lower half disc 12 are parallel to each other and are perpendicular to the plane of the wind wheel.

A disc fixing bracket 15 is also installed between the guide disc 6 and the disc fixing base plate 7 to realize the fixing function of separating the upper and lower half discs, so that the upper and lower half discs have better stability. Disc fixed support 15 comprises connecting rod 16 and slot 17, and connecting rod 16 is parallel with support rod 14, and the two ends of connecting rod 16 are all equipped with slot 17, and the opening of slot 17 is towards guide disc 6, makes When the guide disk 6 is in the separated state, the upper half disk 11 and the lower half disk 12 can be respectively inserted backward into the slots 17 at both ends of the connecting rod 16 .

5a-5d show views in various directions of the diversion disk 6, the disk fixing bracket 15, etc. in the merged state. 6a-6d show views in various directions of the guide disk 6, the disk fixing bracket 15, etc. in a separated state. Under the action of the telescopic piston rod 10, the diversion disk 6 can realize the front and rear horizontal distance movement of the disk; under the action of the rotating mechanism 13, the disk is divided into two halves, and the rotation of each half disk is realized, so that The disc surface is parallel to the ground.

In engineering applications, the loss of wind energy utilization at the blade roots of wind turbines in wind farms is obvious, resulting in a reduction in the overall power generation of wind farms. Therefore, for the wind energy loss of the blade root, the corresponding active control strategy of the guide disk is given, and the design method of the key parameters of the device is given.

The active control strategy is: when the average wind speed is less than the rated wind speed, the diversion disk 6 is in a closed state, and the operation of the telescopic mechanism is realized through the active control system, so that the distance between the disk and the wind wheel is in the best position; when the average wind speed is greater than or When equal to the rated wind speed, the guide disk 6 is in a separated state. The specific usage method includes the following steps:

Step 1: When the sensor detects that the average wind speed for a certain period of time is lower than the rated wind speed, the diversion discs 6 are in a merged state to realize the function of improving the utilization efficiency of wind energy at the blade root. The hydraulic pump 8 starts to provide the power source for the telescopic piston rod 10 to move, so that the guide disk 6 and the plane of the wind rotor are at the optimal distance position under the average wind speed.

Step 2: When the sensor detects that the average wind speed for a certain period of time is greater than or equal to the rated wind speed, in order to reduce the wind load brought by the disc, the diversion disc 6 is in a separated state. The rotating mechanism 13 starts to work to realize the rotation separation of the upper half disc 11 and the lower half disc 12, so that they are perpendicular to the plane of the wind wheel.

Step 3: Then, the hydraulic system starts to work, and the telescopic piston rod 10 approaches the plane of the wind rotor until the upper half disc 11 and the lower half disc 12 are respectively inserted into the disc fixing bracket 15, so that the disc is tightened and fixed, and the resistance High wind speed wind load maintains good stability.

Step 4: If the sensor detects that the average wind speed is lower than the rated wind speed again, the diversion disk 6 reverses the operations of Step 3, Step 2, and Step 1.

The numerical simulation design method of the diversion disc, that is, the design method of the immersion boundary (IB) coupling actuation theory, includes the following steps: (set the radius of the wind wheel as R, the radius of the diversion disc as CR, the diversion disc and The distance of the wind wheel is set to L, as shown in Figure 1)

Step 1: Carry out grid division of the flow field, and perform grid refinement on the position of the diversion disk and the position of the wind rotor, as shown in Figures 7a-7b.

Step 2: Combine the genetic optimization algorithm to calculate the CR and L of the diversion disc.

Step 3: The body force coupling solution of IB and actuation theory is used here to calculate the aerodynamic force of the wind turbine guide disk.

Put forward the NS equation (1):

Among them, the virtual term f _i represents the external force arising from the existence of the boundary of the object, and the items on the right side of the equation except this item are comprehensively expressed as RHS; U _i and U _j are expressed as velocity tensors, and x _i and x _j represent displacements Components, i, j=1, 2, 3; t is discrete time, v represents fluid viscosity coefficient, v _t is dynamic viscosity coefficient;

At a certain moment, the velocity of the equation coordinates can be discretized into the following formula (2):

Among them, n and n+1 represent the relationship before and after the time step;

Through the transmission relationship between speed and force in the above formula, combined with the known speed of the surface of the object The magnitude of the external force at the intermediate step can be obtained:

in, Indicates the magnitude of the external force, f _AD indicates the body force of the wind rotor blade, ρ is the air density, c is the chord length of the blade element, CL and CD are the aerodynamic data of the blade airfoil, and are respectively the lift coefficient and the drag coefficient;

The obtained external force is repeatedly substituted into the momentum equation coupled with the IB body force and the actuation theoretical body force to calculate a new velocity field, and the new velocity field is updated with the external force, and so on until the result meets the accuracy requirements.

Step 4: Calculate the wind turbine power coefficient Cp value at the wind speed, and judge whether the Cp is optimal. If the optimal Cp is not reached, then change the radius CR and distance L of the diversion disc.

Step 5: In the number of optimization iterations, if Cp reaches the maximum value and the optimization has converged, then the optimal radius of the diversion disc is CR and the distance L is obtained.

Based on MW-level wind turbines, through this method, with the power generation of wind turbines as the optimization target, a group of 4m/s, 6m/s, 8m/s, and 10m/s horizontal axis wind turbine active diversion discs are obtained. The radius CR and distance L are (0.085R, 0.14R), (0.085R, 0.17R), (0.085R, 0.18R), (0.085R, 0.2R), respectively.

The size data can be used for the control law design of the active control system of the guide disk.

Take a 2.5MW wind turbine as an example, the radius of the wind rotor is 40m, and the incoming wind speed is 10m/s. Radius of diversion disk CR=3.4m, distance L=8m. Figure 9 shows the flow field velocity cloud diagrams with and without the guide disc when the incoming wind speed is 10m/s. It can be seen from the figure that after the guide disc is added, the blade root The velocity at , and the velocity in the wake area of the wind turbine is also weakened, indicating that the efficiency of the wind rotor to absorb wind energy has increased. Fig. 10 is a curve diagram of the change of the axial velocity on the blade when the incoming wind speed is 10m/s. It can also be seen from the figure that the exit velocity of the blade root is significantly reduced, and the changes in other areas of the blade are small. Through the calculation of the 10m/s incoming wind speed condition, the power generation of the wind turbine has increased by 1.6%.

The present invention has great application prospects and can be used for land and sea horizontal axis wind turbines, especially for wind turbines in wind farms with low wind resources. Through the active control guide disk of the present invention, the wind turbine has the ability to increase power generation Therefore, it is of great significance to increase the power generation of the entire wind farm and reduce the cost of power generation.

It should be noted that terms such as "upper", "lower", "left", "right", "front", and "rear" quoted in the invention are only for clarity of description, not for Limiting the practicable scope of the present invention, and the change or adjustment of the relative relationship shall also be regarded as the practicable scope of the present invention without substantive changes in the technical content.

The above are only preferred implementations of the present invention, and the protection scope of the present invention is not limited to the above-mentioned embodiments, and all technical solutions under the idea of the present invention belong to the protection scope of the present invention. It should be pointed out that for those skilled in the art, some improvements and modifications without departing from the principle of the present invention should be regarded as the protection scope of the present invention.

Claims (5)

1. An improved horizontal axis wind turbine, comprising: the wind power generation device comprises a tower (1), a machine room (2), blades (3), a hub (4), a flow guide cover (5) and a flow guide disc (6), wherein the machine room (2) is arranged at the top end of the tower (1), the hub (4) is arranged at the front end of the machine room (2), the blades (3) are uniformly distributed around the hub (4), the flow guide cover (5) is arranged on the side surface of the hub (4), and the flow guide disc (6) is telescopically arranged at the front end of the hub (4);

a disc fixing bottom plate (7) is installed at the front end of the hub (4), a hydraulic pump (8), a telescopic oil cylinder (9) and a telescopic piston rod (10) are sequentially installed on the disc fixing bottom plate (7), a flow guide disc (6) is fixed at the front end of the telescopic piston rod (10), the telescopic piston rod (10) is perpendicular to the plane of the wind wheel, and the disc fixing bottom plate (7) and the flow guide disc (6) are parallel to the plane of the wind wheel;

the flow guide disc (6) comprises an upper half disc (11), a lower half disc (12), a rotating mechanism (13) and a supporting rod (14), the supporting rod (14) and a telescopic piston rod (10) are vertically fixed at the front end of the telescopic piston rod (10), the upper half disc (11) and the lower half disc (12) are respectively installed at two ends of the supporting rod (14), the upper half disc (11) is connected with the supporting rod (14), the lower half disc (12) is connected with the supporting rod (14) through the rotating mechanism (13), and the rotating mechanism (13) is used for driving the upper half disc (11) and the lower half disc (12) to be separated and combined; when in a combined state, the upper half disc (11) and the lower half disc (12) are spliced into a circle parallel to the plane of the wind wheel; when the wind wheel is in a separated state, the upper half disc (11) and the lower half disc (12) are parallel to each other and are both vertical to the plane of the wind wheel.

2. The improved horizontal axis wind turbine as claimed in claim 1, wherein: install disc fixed bolster (15) between water conservancy diversion disc (6) and disc PMKD (7), disc fixed bolster (15) are including connecting rod (16) and slot (17), connecting rod (16) parallel with bracing piece (14), and slot (17) are all installed at the both ends of connecting rod (16), the opening of slot (17) is towards water conservancy diversion disc (6) for water conservancy diversion disc (6) when the separation state, in slot (17) at connecting rod (16) both ends can be inserted backward respectively in first half disc (11) and lower semicircle dish (12).

3. The use method of the improved horizontal-axis wind turbine as claimed in claim 2, comprising the steps of:

the method comprises the following steps: when the average wind speed is detected to be smaller than the rated wind speed in a certain period of time, the flow guide disc (6) is in a combined state, the hydraulic pump (8) and the telescopic oil cylinder (9) drive the telescopic piston rod (10) to move, and the flow guide disc (6) and the plane of the wind wheel are located at the optimal distance position under the average wind speed;

step two: when the average wind speed in a certain period of time is detected to be greater than or equal to the rated wind speed, the diversion disc (6) is in a separated state, the rotating mechanism (13) starts to work, and the upper half disc (11) and the lower half disc (12) are rotated and separated to be perpendicular to the plane of the wind wheel;

step three: the hydraulic pump (8) and the telescopic oil cylinder (9) work to enable the telescopic piston rod (10) to approach the plane of the wind wheel until the upper half disc (11) and the lower half disc (12) are respectively inserted into the slots (17) at the two ends of the connecting rod (16), so that the discs are tightened and fixed;

step four: when the average wind speed is detected to be smaller than the rated wind speed again, the operation is performed reversely.

4. The design method of the improved horizontal axis wind turbine as claimed in claim 2, characterized by comprising the following steps:

the method comprises the following steps: dividing flow field grids, and carrying out grid encryption on the positions of the flow guide discs and the positions of the wind wheels;

step two: calculating the radius of the diversion disc and the distance between the diversion disc and the wind wheel by combining a genetic optimization algorithm;

step three: calculating aerodynamic force of a wind turbine flow guiding disc by volume force coupling solution of an immersed boundary and an actuating theory;

step four: calculating the power coefficient of the wind turbine at the wind speed based on the aerodynamic force of the guide disc, judging whether the power coefficient of the wind turbine reaches the optimum value, and if the power coefficient of the wind turbine does not reach the optimum value, changing the radius of the guide disc and the distance between the guide disc and the wind wheel again;

step five: and performing optimization iteration, and if the power coefficient of the wind turbine reaches the maximum value and the wind turbine is optimized and converged, obtaining the optimal radius of the flow guiding disc and the optimal distance between the flow guiding disc and the wind wheel.

5. The design method of claim 4, wherein: the third step specifically comprises:

providing an NS equation expression (1) suitable for numerical simulation calculation of the wind turbine:

wherein the virtual item f_iRepresenting the external force arising from the presence of the object boundary, the terms to the right of the equation other than this are collectively represented as RHS; u shape_i、U_jExpressed as the velocity tensor, x_i、x_jRepresents a displacement component, i, j ═ 1, 2, 3; t is discrete time, v represents fluid viscosity coefficient, v_tIs the kinematic viscosity coefficient;

discretizing the velocity of the equation coordinates into the following formula (2):

wherein n and n +1 represent the time step anteroposterior relationship;

the known speed of the surface of the body is combined by the transmission relation of the speed and the stress in the formulaSolving the external force:

wherein,indicating magnitude of external force, f_ADRepresenting the volume force of the wind wheel blade, wherein rho is air density, c is the chord length of the blade element, and CL and CD are respectively a lift coefficient and a drag coefficient;

and repeatedly substituting the obtained external force into a momentum equation with the coupling of the immersion boundary volume force and the actuation theory volume force, calculating a new speed field, updating the external force by the new speed field, and repeating the steps until the result meets the precision requirement.