Parametric design method for archimedes wind rotor for wind turbines

Abstract

The application belongs to the technical field of wind power generation, and particularly relates to a parameter design method of an Archimedes wind wheel for a wind turbine, an aerodynamic braking method and a storage medium. The parameter design method comprises the following steps: obtaining a first design input parameter; determining a critical tip speed ratio of the Archimedes wind wheel based on a target installation angle and a critical angle of attack; determining a target wake wind speed based on a rated rotating speed, a radius of the Archimedes wind wheel and the critical tip speed ratio; determining the wake wind speed at different axial distances based on a combined wake model; and matching the target wake wind speed with the wake wind speed at different axial distances to determine a target installation distance of the Archimedes wind wheel. The method of the application can realize self-adaptive braking through spatial matching design of aerodynamic parameters.

Description

Technical Field

[0001] This application belongs to the field of wind power generation technology, specifically relating to a parameter design method, aerodynamic braking method, and storage medium for an Archimedes wind turbine. Background Technology

[0002] In wind power generation technology, braking systems are typically required to prevent damage to wind turbines under extreme wind speeds. Existing horizontal axis wind turbine braking methods mainly include mechanical brakes, pitch brakes, yaw brakes, and electric brakes. However, mechanical brakes suffer from problems such as rapid wear of friction pads, high maintenance costs, and brake force attenuation at high temperatures; pitch brake mechanisms are complex, have delayed response, and are costly; yaw brakes can lead to uneven stress on the entire turbine and excessive structural stress; and electric brakes rely on the power grid and power electronic equipment, making them prone to failure during grid failures.

[0003] Although existing technologies have proposed methods for extracting wind energy using Archimedes' wind turbines, these are typically designed for use in free-flowing environments to output positive power. They lack adaptive braking designs for the wake environment of wind turbines and cannot achieve automatic pneumatic braking during overspeed without interfering with rated power generation.

[0004] Therefore, there is an urgent need for a parameter design method that can accurately match aerodynamic parameters based on wake characteristics to achieve passive, wear-free, and adaptive braking. Summary of the Invention

[0005] The purpose of this application is to provide a parameter design method, aerodynamic braking method and storage medium for Archimedes rotors used in wind turbines, to solve the problems of complex braking system structure, mechanical wear or reliance on external energy leading to low reliability in the prior art, and to achieve an adaptive aerodynamic braking effect that does not interfere with power generation under rated operating conditions and automatically brakes under overspeed conditions.

[0006] In a first aspect, embodiments of this application provide a parameter design method for an Archimedes wind turbine, wherein the wind turbine includes a main rotor and a nacelle, and the Archimedes wind turbine is disposed in the combined wake region of the main rotor and the nacelle, and is coaxially and fixedly connected to the main rotor; the parameter design method includes: Obtain the first design input parameters, which include the rated speed of the main wind turbine, the radius of the Archimedes wind turbine, the target installation angle, and the critical angle of attack; Based on the target installation angle and the critical angle of attack, the critical tip speed ratio of the Archimedes wind turbine is determined; The target wake wind speed is determined based on the rated rotational speed, the radius of the Archimedes wind turbine, and the critical tip speed ratio. Based on the combined wake model, the wake wind speed at different axial distances is determined. The combined wake model characterizes the superposition relationship between the main wake of the main wind turbine and the local wake of the nacelle. The target wake velocity is matched with the wake velocity at different axial distances to determine the target installation distance of the Archimedes wind turbine.

[0007] Optionally, matching the target wake velocity with the wake velocities at different axial distances to determine the target installation distance of the Archimedes wind turbine includes: Based on the wake wind speed at the different axial distances, a mapping table between axial distance and wake wind speed is constructed. In the mapping table, find the wake speed whose difference from the target wake speed meets the preset condition; The axial distance corresponding to the found wake wind speed is determined as the target installation distance.

[0008] Secondly, embodiments of this application provide another parameter design method for an Archimedes wind turbine, wherein the wind turbine includes a main rotor and a nacelle, and the Archimedes wind turbine is disposed in the combined wake region of the main rotor and the nacelle, and is coaxially and fixedly connected to the main rotor; the parameter design method includes: Obtain the second design input parameters, which include the rated speed of the main wind turbine, the radius of the Archimedes wind turbine, the target installation distance, and the critical angle of attack; Based on the combined wake model, the target wake wind speed at the target installation distance is determined. The combined wake model represents the superposition relationship between the main wake of the main wind turbine and the local wake of the nacelle. Based on the rated rotational speed, the radius of the Archimedes wind turbine, and the target wake velocity, the critical tip speed ratio is determined. Based on the critical tip speed ratio and the critical angle of attack, the target installation angle of the Archimedes wind turbine is determined.

[0009] Optionally, the second design input parameters also include the number of blades and the solidity of the Archimedes wind turbine, and after determining the target installation angle of the Archimedes wind turbine, the following is also included: The target pitch of the Archimedes wind turbine is determined based on the target installation angle, the radius of the Archimedes wind turbine, the number of blades, and the solidity.

[0010] Optionally, in the first and second aspects, the target installation angle, the critical angle of attack, and the critical tip speed ratio satisfy the following relationship:

[0011] in, Install the target angle. The critical tip speed ratio is given. The critical angle of attack is denoted as .

[0012] Optionally, in the first and second aspects, the range of the critical angle of attack is: 8°~ 5°.

[0013] Optionally, in the first and second aspects, the critical tip speed ratio satisfies the following relationship with the rated rotational speed, the radius of the Archimedes wind turbine, and the target wake velocity:

[0014] in, The critical tip speed ratio is given. The rated speed, Let the radius of the Archimedes wind turbine be _____. Let be the target wake velocity.

[0015] Optionally, in the first and second aspects, the combined wake model includes a main wake model and a local wake model, and the wake wind speed output by the combined wake model satisfies the following relationship:

[0016] in, The axial distance output by the combined wake model The wake wind speed at the location, The axial distance output by the main wake model The main wake wind speed at the location, The central velocity deficit coefficient, The axial distance is [the distance between the two points]. To recover the feature length of the velocity, For free-flowing wind speed, The main wind turbine thrust coefficient, The wake expansion coefficient is... The radius of the main wind turbine is given.

[0017] Thirdly, embodiments of this application provide an aerodynamic braking method for a wind turbine, the wind turbine including a main rotor and a nacelle, an Archimedes wind turbine being provided in the combined wake region of the main rotor and the nacelle, the Archimedes wind turbine being coaxially and fixedly connected to the main rotor, the parameters of the Archimedes wind turbine being determined based on the parameter design method described in any of the foregoing claims, and the aerodynamic braking method including: When the operating speed of the main wind turbine is lower than its rated speed, the Archimedes wind turbine is in a positive torque state to assist acceleration. When the operating speed is equal to the rated speed, the Archimedes wind turbine is in a zero-torque critical state; When the operating speed is greater than the rated speed, the Archimedes windmill is in a negative torque state to perform pneumatic braking.

[0018] Fourthly, embodiments of this application provide a computer storage medium storing instructions or programs that, when executed by at least one processor, cause the at least one processor to perform the method described in the first or second aspect above.

[0019] This application provides a parameter design method for an Archimedes rotor for wind turbines, which has the following advantages: First, the Archimedes rotor is positioned in the combined wake region of the main rotor and the nacelle, allowing the Archimedes rotor, which is much smaller than the radius of the main rotor, to reach a critical state at the same rated speed. Second, a combined wake model is established, and based on the characteristic of the wake wind speed changing with axial distance in the combined wake model, the geometric parameters that enable the Archimedes rotor to reach the critical tip speed ratio are determined. Based on this parameter design method and the special arrangement of the Archimedes rotor in the wind turbine, when the main rotor is at its rated speed, the wake wind speed at the location of the Archimedes rotor puts it in a state of zero torque, thereby avoiding aerodynamic interference to normal power generation. When the main rotor overspeeds, because the increase in tip tangential velocity is greater than the change in wake wind speed, the Archimedes rotor automatically enters the negative angle of attack region to generate negative torque, achieving passive aerodynamic braking. The method of this application does not require additional sensors, actuators or external energy sources. It can achieve adaptive braking simply by designing the spatial matching of aerodynamic parameters. This effectively solves the problems of complex structure, high wear and low reliability of existing braking systems, while ensuring power generation efficiency under rated operating conditions. Attached Figure Description

[0020] Figure 1 A schematic diagram of a wind turbine equipped with an Archimedes rotor is provided for an embodiment of this application; Figure 2 A flowchart illustrating a parameter design method for an Archimedes wind turbine provided in this application embodiment; Figure 3 A flowchart illustrating another parameter design method for an Archimedes wind turbine provided in this application embodiment; Figure 4 A schematic diagram of the velocity field distribution in the combined wake region of the main rotor and nacelle provided in this embodiment of the application; Figure 5 The geometric parameter definition diagram of the Archimedes wind turbine provided in the embodiments of this application; Figure 6The simulation comparison diagram of braking effect provided for the embodiments of this application. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0022] Please refer to Figure 1 , Figure 1 A schematic diagram of a wind turbine equipped with an Archimedes rotor, provided for an embodiment of this application. Figure 1 As shown, the wind turbine includes a main rotor and a nacelle. The Archimedes rotor is located in the downstream wake region of the main rotor and the nacelle and is coaxially and fixedly connected to the main rotor. As an optional implementation, the coaxial fixed connection means that the Archimedes rotor is fixedly connected to the rotating shaft of the main rotor by means of coupling, flange, or direct welding, so that the axis lines of the two are completely overlapped and the two cannot move relative to each other.

[0023] Specifically, the wind turbine is a horizontal axis wind turbine. This coaxial fixed connection structure ensures that the Archimedes rotor and the main rotor have the same rotational angular velocity, directly coupling its aerodynamic state to the operating conditions of the main rotor. This lays the mechanical foundation for subsequent passive braking through spatial position adjustment. Because the radius of the Archimedes rotor is much smaller than that of the main rotor, its tip tangential velocity is very low at the same rated speed. If placed in a wind field with high wind speeds, its actual tip speed ratio will always be less than the critical tip speed ratio (see description below), thus keeping it in a "positive torque" state and unable to achieve braking. However, by placing the Archimedes rotor downstream of the main rotor and nacelle in the wake region, the nacelle, a large blunt body, creates a "velocity deficit zone" directly behind it, further reducing the incoming wind speed at the Archimedes rotor's location. This allows its actual tip speed ratio to reach the critical tip speed ratio, thereby achieving adaptive braking of the wind turbine.

[0024] Please refer to Figure 2 , Figure 2 This is a flowchart illustrating a parameter design method for an Archimedes rotor used in a wind turbine, provided as an embodiment of this application. The wind turbine is... Figure 1 The wind turbine shown uses a forward design paradigm that establishes a known installation angle and then determines the installation distance. For example... Figure 2 As shown, the parameter design method specifically includes the following steps S201 to S205.

[0025] Step S201: Obtain the first design input parameters, which include the rated speed of the main wind turbine, the radius of the Archimedes wind turbine, the target installation angle, and the critical angle of attack.

[0026] The rated speed of the main rotor is typically determined by downstream electrical components such as generators, power grids, or energy storage systems, and is a predetermined input for the system design. The radius of the Archimedes rotor is usually limited by the space at the rear of the nacelle during design, and is generally set to be equal to or slightly smaller than the nacelle radius. The target installation angle refers to the geometric angle of the Archimedes propeller blade relative to the plane of rotation. In this embodiment, it is a preset fixed parameter, typically ranging from 20° to 40°. This angle determines the basic aerodynamic characteristic curve shape of the Archimedes rotor. The critical angle of attack refers to the specific angle of the airflow relative to the blade chord when the Archimedes rotor is in a "zero torque critical state." By obtaining these basic parameters, the initial boundary conditions for the parameter design are constructed.

[0027] Step S202: Determine the critical tip speed ratio of the Archimedes wind turbine based on the target installation angle and critical angle of attack.

[0028] The critical tip speed ratio is an inherent tip speed ratio of the Archimedes wind turbine, determined by its angle of installation and critical angle of attack, which places the Archimedes wind turbine at the "positive / negative torque dividing point." It is essentially a physical "comparator" installed on the Archimedes wind turbine. In actual operation, if the actual tip speed ratio is the same as the critical tip speed ratio, the Archimedes wind turbine is in a zero-torque state, causing no aerodynamic interference to normal power generation. If the actual tip speed ratio exceeds the critical tip speed ratio, the Archimedes wind turbine automatically enters the negative angle of attack region, generating negative torque to achieve passive aerodynamic braking. If the actual tip speed ratio is less than the critical tip speed ratio, the Archimedes wind turbine automatically enters a positive torque state, achieving auxiliary acceleration.

[0029] Geometrically, the target installation angle defines the angle between the blade chord and the plane of rotation (e.g., ...). Figure 5 As shown in the figure, the critical angle of attack defines the angle between the incoming flow direction and the blade chord line. The geometric sum of the two determines the angle between the incoming flow direction and the plane of rotation, thus uniquely determining the ratio of the tip velocity to the incoming wind speed in this critical state. Based on the velocity triangle geometry of the Archimedes propeller blade in the critical state, the following relationship can be obtained between the target installation angle, the critical angle of attack, and the critical tip velocity ratio: (1) in, Install the angle for the target. This is the critical tip speed ratio. The critical angle of attack, This refers to the axial distance (i.e., the axial distance between the leading edge of the Archimedes wind turbine and the tail end face of the nacelle). This refers to the rated speed of the main wind turbine.

[0030] It should be pointed out that, and The value of and axial distance and the rated speed of the main wind turbine Correlation, that is, at a given axial distance and the rated speed of the main wind turbine Under these conditions, there exists a corresponding target installation angle that enables the Archimedes windmill to reach a critical state of zero torque at its rated speed. When axial distance Or the rated speed of the main wind turbine When changes occur, the target installation angle... It will also change. Similarly, at a given axial distance... and the rated speed of the main wind turbine Under these conditions, there exists a corresponding critical tip speed ratio that enables the Archimedes wind turbine to reach a zero-torque critical state at its rated speed. When axial distance Or the rated speed of the main wind turbine When changes occur, the critical tip speed ratio... Things will also change.

[0031] In equation (1), This represents the angle between the relative incoming velocity (i.e., wake velocity) and the plane of rotation at the critical tip speed ratio (i.e., the incoming angle). The incoming angle is calculated by subtracting the critical angle of attack from the incoming angle. This yields the target installation angle of the blade chord relative to the plane of rotation. The establishment of this mathematical relationship enables designers to accurately transform abstract aerodynamic critical states into manufacturable physical geometric parameters, thereby achieving decoupled design of the wind turbine's aerodynamic characteristics and the main wind turbine's operating conditions.

[0032] As a specific implementation method, when determining the critical tip speed ratio according to equation (1) in step S202, equation (1) is first rearranged to obtain the calculation formula for the critical tip speed ratio: Substitute the target installation angle and critical angle of attack into the formula to calculate the critical tip speed ratio.

[0033] As one specific implementation method, the range of the critical angle of attack is: 8°~ 5°. Archimedes wind turbines typically employ flat or slightly curved airfoils, whose aerodynamic characteristics differ significantly from those of traditional lift-type wind turbine blades. The selection of a negative critical angle of attack range is based on the stall characteristics of this type of airfoil under low Reynolds number and complex wake environments. When the critical angle of attack is [value missing]... At 5°, the critical angle of attack typically corresponds to the initial position of the blade transitioning from zero lift to negative lift under laminar boundary conditions or low turbulence environments. At this point, the Archimedes rotor is in a critical equilibrium state of zero torque or slightly positive torque. When the critical angle of attack is -8°, it corresponds to the condition in a high turbulence wake environment where the airflow separation point moves forward, causing negative lift to be generated earlier. Limiting the critical angle of attack within this range ensures that the Archimedes rotor remains stably in a "zero torque" state at the rated speed of the main rotor, avoiding parasitic drag that reduces power generation efficiency due to an excessively large angle of attack, or premature braking intervention due to an excessively small angle of attack.

[0034] Step S203: Determine the target wake wind speed based on the rated rotational speed, the radius of the Archimedes wind turbine, and the critical tip speed ratio.

[0035] Since the Archimedes rotor is coaxially and fixedly connected to the main rotor, the tip tangential velocity of the Archimedes rotor is also determined when the main rotor is at its rated speed (calculated from the rated speed and radius). Using the critical tip speed ratio determined in step S202, a specific incoming wind speed value, i.e., the target wake wind speed, can be calculated based on this tip tangential velocity. The physical meaning of this target wake wind speed is: if the actual wind speed at the location of the Archimedes rotor is equal to the target wake wind speed, the Archimedes rotor will be in a critical aerodynamic state (such as a zero torque state); if the actual wind speed deviates from the target wake wind speed, the Archimedes rotor will automatically enter an auxiliary acceleration or braking state.

[0036] As a specific implementation method, the critical tip speed ratio satisfies the following relationship with the rated speed, the radius of the Archimedes wind turbine, and the target wake wind speed: (2) in, Let the radius of Archimedes' wind turbine be . The target wake wind speed.

[0037] In equation (2), the first part ( This converts the rated speed of the main wind turbine (in revolutions per minute) into the tip tangential velocity of the Archimedes wind turbine (in m / s), utilizing the physical constraint that the angular velocities of both are equal under coaxial fixed connection conditions. Part Two This is the actual incoming wind speed (i.e., the target wake wind speed) at the location of the Archimedes rotor. The ratio of the two is the critical tip speed ratio. This formula defines a threshold: when the actual tip speed ratio equals the critical tip speed ratio, the Archimedes rotor is exactly at the aerodynamic torque conversion point. Through equation (2), the rated operating parameters of the main rotor ( ) and the geometric dimensions of the wind turbine itself ( This is mapped to specific requirements of the flow field environment, thereby guiding subsequent installation distance matching or installation angle reverse design.

[0038] As a specific implementation method, when determining the target wake velocity according to equation (2) in step S202, equation (2) is first rearranged to obtain the calculation formula for the target wake velocity: Then, by substituting the rated speed, the radius of the Archimedes wind turbine, and the critical tip speed ratio into the formula, the target wake wind speed can be calculated.

[0039] Step S204: Based on the combined wake model, determine the wake wind speed at different axial distances. The combined wake model characterizes the superposition relationship between the main wake of the main rotor and the local wake of the nacelle.

[0040] like Figure 4 As shown, in the near-wake region behind the main rotor, the airflow velocity distribution is neither uniform nor monotonically changing. On one hand, after the main rotor extracts wind energy, it forms a large-scale velocity deficit region, i.e., the main wake, whose wind speed recovery follows a certain expansion law; on the other hand, the nacelle, as a bluff body obstacle, forms a local low-speed recirculation region or strong shear region directly behind it, i.e., a local wake. The combined wake model used in this embodiment, by superimposing and correcting the velocity distribution of the main wake with the central velocity deficit caused by the nacelle, can accurately describe the continuous velocity gradient change from the nacelle surface to the far-field wake.

[0041] As a specific implementation method, the combined wake model includes a main wake model and a local wake model. The wake wind speed output by the combined wake model satisfies the following relationship: (3) in, Axial distance output by the combined wake model The wake wind speed at the location, The axial distance output by the main wake model The main wake wind speed at the location, The central velocity deficit coefficient, This is the axial distance. To recover the feature length of the velocity, For free-flowing wind speed, The main wind turbine thrust coefficient, The wake expansion coefficient is... The radius of the main wind turbine. It should be noted that, except for the axial distance d, all other parameters in equation (3) are design input parameters.

[0042] Specifically, in equation (3) The classic Jensen top-hat model or its variants are employed to describe the velocity deficit of the large-scale main wake formed after the main rotor extracts energy and its diffusion recovery with distance. In the region immediately behind the nacelle, the airflow is also strongly influenced by the flow around the nacelle bluff body, forming a local wake region with extremely low central velocity and gradually recovering outwards. Therefore, this application introduces a correction factor. This is used to characterize the superposition effect of local wakes. The center velocity deficit coefficient C reflects the maximum velocity deficit along the axis directly behind the nacelle, and can be taken as approximately 0.9. The velocity recovery characteristic length L characterizes how quickly the nacelle wake recovers to the level of the main wake; its value is related to the nacelle diameter and surface roughness, and can be experimentally calibrated to 0.15 m. (Exponential term) The model accurately depicts the physical law of the exponential decay of the local wake with increasing axial distance. Through this superposition modeling method, the joint wake model can accurately describe the continuous velocity gradient change from the nacelle surface to the far-field wake, providing reliable flow field data support for the accurate matching of the Archimedes wind turbine installation distance.

[0043] As a specific implementation method, determining the wake wind speed at different axial distances based on the combined wake model includes: first calculating the main wake model at that axial distance based on a given axial distance d. The main wake velocity at the location; then multiply the main wake velocity by the correction factor. The wake velocity of the combined wake model at the given axial distance d is calculated. Similarly, the wake velocity of the combined wake model at different axial distances can be obtained.

[0044] Step S205: Match the target wake velocity with the wake velocity at different axial distances to determine the target installation distance of the Archimedes wind turbine.

[0045] As an optional implementation, step S205 specifically includes: constructing a mapping table between axial distance and wake velocity based on the wake velocity at different axial distances determined in step S204; finding a wake velocity in the mapping table whose difference from the target wake velocity meets a preset condition; and determining the axial distance corresponding to the found wake velocity as the target installation distance. The preset condition can be set according to actual needs (e.g., set to the minimum absolute value of the difference, or the minimum absolute value of the difference and the absolute value of the difference being less than a preset difference threshold). Its purpose is to find a wake velocity that is the same as or close to the target wake velocity. For example, if the calculated target wake velocity is 2.0 m / s, and in the combined wake model, the wind velocity at a distance of 0.06 m from the rear of the nacelle is exactly 2.0 m / s, then 0.06 m is the desired target installation distance.

[0046] In this way, this embodiment can "anchor" the aerodynamic critical point of the Archimedes rotor to a specific spatial position corresponding to the rated speed of the main rotor during the design phase. The technical advantage lies in the fact that, without any active control mechanism, this passive space-aerodynamic parameter coupling design alone ensures that the Archimedes rotor does not generate parasitic drag (i.e., zero torque) under rated operating conditions, while automatically generating negative torque braking under overspeed conditions due to the mismatch between the wake wind speed and the tip speed ratio. This achieves a simple, rapid-response, and wear-free adaptive braking function.

[0047] In practical engineering design, the axial space at the tail of the nacelle is often strictly limited by the generator length, yaw mechanism layout, or tower connection flange position, making the installation distance of the Archimedes rotor a rigid boundary condition that is difficult to adjust. In this case, if the following is still adopted... Figure 2 The method in the embodiments may calculate an installation distance that exceeds the limits allowed by physical space. Therefore, this application provides another parameter design method for an Archimedes rotor of a wind turbine, using the installation distance as a preset input to deduce the required blade installation angle, thereby meeting the compactness requirements of the structural space while ensuring braking performance. This embodiment is similar to... Figure 2 The embodiments together constitute a two-way complementary parameter design protection system.

[0048] Please refer to Figure 3 , Figure 3 This is a flowchart illustrating another parameter design method for an Archimedes rotor used in a wind turbine, provided as an embodiment of this application. The wind turbine is... Figure 1 The wind turbine shown, and Figure 2 Unlike the forward design paradigm of determining the installation distance from a known installation angle in the previous embodiment, this embodiment establishes a reverse design paradigm of determining the installation angle from a known installation distance to adapt to specific engineering constraints. For example... Figure 3 As shown, the parameter design method specifically includes the following steps S301 to S305.

[0049] Step S301: Obtain the second design parameters, which include the rated speed of the main wind turbine, the radius of the Archimedes wind turbine, the target installation distance, and the critical angle of attack.

[0050] Specifically, the target installation distance is a fixed value predetermined based on the available space at the rear of the nacelle or the existing support structure. For example, limited by the distance from the rear end cover of the nacelle to the hub of the main rotor, this value may be limited to between 0.05m and 0.15m. The physical meaning of the radius of the Archimedes rotor, the rated speed of the main rotor, and the critical angle of attack are related to... Figure 2 The implementation method is the same and will not be repeated here. Using these parameters as the starting boundary for reverse design ensures that subsequent calculation results can be directly adapted to the established mechanical interface.

[0051] Step S302: Based on the combined wake model, determine the target wake wind speed at the target installation distance. The combined wake model characterizes the superposition relationship between the main wake of the main rotor and the local wake of the nacelle.

[0052] Since the target installation distance is known, this step no longer requires... Figure 2 Instead of performing a wind speed matching search as in the previous embodiment, the target installation distance is directly substituted into the combined wake model (3) for forward calculation to obtain the airflow velocity at that specific location. For example, if the target installation distance is set to 0.057m, the wake wind speed at that location can be calculated using the combined wake model to be approximately 1.97m / s. This value is the target wake wind speed that the Archimedes wind turbine must match to achieve the critical state at that installation location.

[0053] Step S303: Determine the critical tip speed ratio based on the rated speed, the radius of the Archimedes wind turbine, and the target wake wind speed.

[0054] When the main wind turbine rotates at its rated speed, the tip tangential velocity of the coaxially fixed Archimedes wind turbine is ( The ratio of the tip tangential velocity to the target wake velocity is determined by equation (2). The critical tip velocity ratio required to achieve the zero torque critical state at the current installation distance can be obtained by calculating the ratio of the tip tangential velocity to the target wake velocity. Its physical essence is that the spatial position locks the target wake velocity. In order to achieve aerodynamic criticality, the kinematic parameters (tip velocity ratio) of the Archimedes wind turbine itself must be passively adapted to this target wake velocity.

[0055] Step S304: Determine the target installation angle of the Archimedes wind turbine based on the critical tip speed ratio and critical angle of attack.

[0056] Specifically, by substituting the critical tip speed ratio obtained in step S303 and the preset critical angle of attack into equation (1), the target installation angle can be calculated. For example, if the calculated critical tip speed ratio is 2.1445 and the critical angle of attack is -5°, then the target installation angle is approximately 30°. This target installation angle is the theoretical tilt angle of the Archimedes propeller blade relative to the plane of rotation, ensuring that the Archimedes rotor is precisely at the critical point of positive and negative torque conversion at a specified installation distance. Through this reverse derivation, designers can adapt to limited installation space by adjusting the blade angle without altering the nacelle structure, while simultaneously ensuring precise triggering of the braking function.

[0057] As one implementation, the second design parameters also include the number of blades and solidity of the Archimedes wind turbine; after determining the target installation angle of the Archimedes wind turbine, the parameters also include: determining the target pitch of the Archimedes wind turbine based on the target installation angle, the radius of the Archimedes wind turbine, the number of blades and solidity.

[0058] according to Figure 5 It can be seen that the three-dimensional geometry of the Archimedes wind turbine depends not only on the installation angle. It also depends on the pitch P. Based solely on the mounting angle... Only the inclination of the blade chord can be determined, but the axial extension density of the helix cannot be uniquely determined. The formula for determining the target pitch can be expressed as: (4) in, For the degree of reality, Let B be the radius of the Archimedes wind turbine, and B be the number of blades. Install the angle for the target. Specifically, the degree of realism. This represents the ratio of the total projected area of ​​the blades to the swept area, reflecting the Archimedes wind turbine's ability to obstruct airflow; the number of blades B is usually set to 3 to ensure dynamic balance. For example, when the target installation angle is determined to be 30°, the radius is 0.115m, the number of blades is 3, and the solidity is selected as 1.3, the calculated target pitch is approximately 0.1565m.

[0059] Furthermore, the helix equation of the Archimedes windmill can be expressed in cylindrical coordinates as follows: (5) in, Let be the radial distance from a point on the Archimedes propeller blade to the axis of rotation. The polar angle through which the Archimedes propeller blade rotates about its central axis of rotation. This represents the axial position of a point on an Archimedes propeller blade.

[0060] As can be seen from equation (5), the geometric parameters of the Archimedes wind turbine can be determined by the installation angle (the radius, solidity, and number of blades of the Archimedes wind turbine are generally design input parameters), and the target installation angle that makes the Archimedes wind turbine reach the zero torque critical state at the rated speed is related to the installation distance and the rated speed. Therefore, the geometric parameters of the Archimedes wind turbine that make it reach the zero torque critical state at the rated speed can be determined by the installation angle, the installation distance, and the rated speed. In actual design, for convenience, the installation angle is generally fixed, that is, the Archimedes wind turbine body remains unchanged, while the installation distance is adjusted with the rated speed (i.e., Figure 2 Example). To adapt to specific installation environments and meet the requirements of structural space compactness, the installation distance can be fixed first. That is, without changing the nacelle structure, the installation angle can be adjusted to adapt to the limited installation space, so as to ensure the precise triggering of the braking function (i.e., Figure 3 Example (Example).

[0061] This application also provides an aerodynamic braking method for a wind turbine. This method is a practical application process that transforms the static geometric parameters determined in the foregoing embodiments into dynamic operational behavior. The wind turbine includes a main rotor and a nacelle. An Archimedes wind turbine is disposed in the combined wake region of the main rotor and the nacelle. The Archimedes wind turbine is coaxially and fixedly connected to the main rotor, and the parameters of the Archimedes wind turbine are determined based on the parameter design method described in the foregoing embodiments.

[0062] Specifically, this coaxial fixed connection structure ensures that the Archimedes rotor's rotational angular velocity is strictly synchronized with the main rotor, while the wake velocity at its location is uniquely determined by the combined wake model. It is this precise coupling of kinematic synchronization and spatial distribution of the flow field that allows this braking method to achieve adaptive state switching without any external sensors, controllers, or actuators, relying solely on the interaction forces between the fluid and the solid.

[0063] In this aerodynamic braking method, when the main rotor's operating speed is lower than its rated speed, the Archimedes rotor operates in a positive torque state to assist acceleration. Specifically, when the wind turbine is in the startup phase or operating in a low wind speed range, the main rotor's speed is low, resulting in the Archimedes rotor's tip speed ratio being less than the designed critical tip speed ratio. According to the velocity triangle relationship, the inflow angle of attack of the airflow relative to the blades is greater than the critical angle of attack, falling within the positive lift coefficient range of the blade airfoil. Therefore, the airflow passing through the blades generates tangential aerodynamic force in the same direction as the main rotor's rotation, forming a positive driving torque. This state not only does not generate drag on the main rotor but also utilizes the residual kinetic energy in the wake to provide additional starting torque, effectively improving the wind turbine's startup performance and acceleration response characteristics in low wind speed areas.

[0064] In this aerodynamic braking method, when the operating speed equals the rated speed, the Archimedes rotor is in a zero-torque critical state. Specifically, this is the "aerodynamic anchor point" pursued by the parameter design method of this application. When the main rotor reaches the rated speed, the tip speed ratio of the Archimedes rotor is exactly equal to the critical tip speed ratio, and the corresponding inflow angle of attack is also exactly equal to the critical angle of attack (e.g., between -5° and -8°). In this state, the pressure distribution on the blade surface makes the tangential component of the aerodynamic resultant force approach zero, that is, the rotor neither outputs driving force nor generates braking force. Figure 6 As shown in the simulation curves, the braking power of the Archimedes rotor approaches zero near the rated speed. This zero-torque state ensures that, under normal power generation conditions, the Archimedes rotor will not reduce the aerodynamic efficiency of the main rotor or increase the generator load due to parasitic drag, thus guaranteeing that the rated output power of the system remains unaffected.

[0065] In this aerodynamic braking method, when the operating speed exceeds the rated speed, the Archimedes rotor operates under negative torque to perform aerodynamic braking. Specifically, when a sudden increase in ambient wind speed or load unloading causes the main rotor to tend to overspeed, its rotational speed increases accordingly. Since the Archimedes rotor is coaxially and fixedly connected to the main rotor, its tip tangential velocity increases linearly; however, simultaneously, the wake velocity at its location is constrained by the physical limitations of the combined wake model and does not increase proportionally with the increase in rotational speed. This causes the actual operating tip speed ratio to rapidly exceed the critical tip speed ratio, and the inflow angle of attack decreases, entering the negative region or deep stall region. At this point, the airflow exerts a tangential force on the blades opposite to the direction of rotation, forming a significant negative torque. Figure 6 As shown, as the rotational speed further exceeds the rated value, the absolute value of the negative torque exhibits a non-linear and rapid growth trend. This braking effect is entirely passive and instantaneous, and the magnitude of the braking torque is automatically matched to the degree of overspeed: the more severe the overspeed, the greater the negative torque generated. Compared to traditional mechanical brakes or pitch mechanisms, this method eliminates response delay and the risk of mechanical wear, and can still operate independently and reliably when a power grid failure causes electrical braking to fail, providing a final intrinsic safety line for wind turbines.

[0066] To further illustrate the feasibility and engineering application value of the technical solution of this application, based on the aforementioned embodiments, a specific numerical verification process, optional enhanced structural implementation methods, and the application architecture of the system in off-grid energy environments are provided.

[0067] First, to verify the effectiveness of the aforementioned parameter design method, this embodiment provides a set of specific design examples. The design conditions are set as follows: the radius of the main wind turbine... =0.6m, cabin radius = 0.115m, free-flowing wind speed =15m / s. The preset geometric parameters of the Archimedes wind turbine are: radius... =0.115m (equal to the nacelle radius to maximize the use of the wake core area), number of blades B=3, target installation angle =30°, real degree =1.3. The pitch under this configuration can be calculated using formula (4) from the aforementioned embodiment. ≈0.1565m, critical tip speed ratio ≈2.1445.

[0068] Specifically, the verification process includes the following three key steps. The first step is to calculate the matching wake velocity based on the rated rotational speed. According to formula (2), when the main rotor's rated rotational speed... At 350 RPM, the target wake wind speed required for the Archimedes wind turbine to reach the zero-torque critical state can be calculated by reverse calculation. The speed is approximately 1.97 m / s. Similarly, if the rated speeds are 400, 450, 500, 550, and 600 RPM, the corresponding target wake velocities are 2.25, 2.53, 2.81, 3.09, and 3.37 m / s, respectively. The second step is to establish the mapping relationship between axial distance and wake velocity. Using the aforementioned combined wake model, the actual wind speed at different downstream distances d is calculated. For example, at d=0.01m, the composite wind speed after considering the local wake effect of the nacelle is only 0.79 m / s; while at d=0.10m, the wind speed recovers to 2.81 m / s. The third step is to perform parameter matching. Comparing the target wake velocity obtained in the first step with the mapping data from the second step, it was found that when the rated speed is 350 RPM, the target wake velocity of 1.97 m / s corresponds exactly to an axial distance d = 0.057 m; when the rated speed is 500 RPM, the target wake velocity of 2.81 m / s corresponds to an axial distance d = 0.10 m. This numerical verification result shows that the parameter design method provided in this application can accurately establish a quantitative coupling relationship between the rated speed and the installation distance, ensuring that the wind turbine accurately achieves the preset passive braking function under the design conditions.

[0069] This application also provides a non-volatile computer-readable storage medium storing computer-executable instructions that are executed by one or more processors, for example, to perform the parameter design method steps of the Archimedes windmill described above.

[0070] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them; under the concept of this application, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of different aspects of this application as described above, which are not provided in detail for the sake of brevity; although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or make equivalent substitutions for some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A parameter design method for an Archimedes wind turbine, characterized in that, The wind turbine includes a main rotor and a nacelle. The Archimedes rotor is located in the combined wake region of the main rotor and the nacelle and is coaxially and fixedly connected to the main rotor. The parameter design method includes: Obtain the first design input parameters, which include the rated speed of the main wind turbine, the radius of the Archimedes wind turbine, the target installation angle, and the critical angle of attack; Based on the target installation angle and the critical angle of attack, the critical tip speed ratio of the Archimedes wind turbine is determined; The target wake wind speed is determined based on the rated rotational speed, the radius of the Archimedes wind turbine, and the critical tip speed ratio. Based on the combined wake model, the wake wind speed at different axial distances is determined. The combined wake model characterizes the superposition relationship between the main wake of the main wind turbine and the local wake of the nacelle. The combined wake model includes a main wake model and a local wake model. The main wake model is used to describe the velocity distribution of the main wake formed after the main wind turbine extracts energy, and the local wake model is used to describe the center velocity loss caused by the nacelle. The target wake velocity is matched with the wake velocity at different axial distances to determine the target installation distance of the Archimedes wind turbine.

2. The parameter design method according to claim 1, characterized in that, The step of matching the target wake velocity with the wake velocities at different axial distances to determine the target installation distance of the Archimedes wind turbine includes: Based on the wake wind speed at the different axial distances, a mapping table between axial distance and wake wind speed is constructed. In the mapping table, find the wake speed whose difference from the target wake speed meets the preset condition; The axial distance corresponding to the found wake wind speed is determined as the target installation distance.

3. The parameter design method according to claim 1 or 2, characterized in that, The target installation angle, the critical angle of attack, and the critical tip speed ratio satisfy the following relationship: in, Install the target angle. The critical tip speed ratio is given. The critical angle of attack is denoted as .

4. The parameter design method according to claim 3, characterized in that, The critical angle of attack ranges from -8° to -5°.

5. The parameter design method according to claim 1 or 2, characterized in that, The critical tip speed ratio satisfies the following relationship with the rated rotational speed, the radius of the Archimedes wind turbine, and the target wake speed: in, The critical tip speed ratio is given. The rated speed, Let the radius of the Archimedes wind turbine be _____. Let be the target wake velocity.

6. The parameter design method according to claim 1 or 2, characterized in that, The wake wind speed output by the combined wake model satisfies the following relationship: in, The axial distance output by the combined wake model The wake wind speed at the location, The axial distance output by the main wake model The main wake wind speed at the location, The central velocity deficit coefficient, The axial distance is [the distance between the two points]. To recover the feature length of the velocity, For free-flowing wind speed, The main wind turbine thrust coefficient, The wake expansion coefficient is... The radius of the main wind turbine is given.

7. A parameter design method for an Archimedes wind turbine, characterized in that, The wind turbine includes a main rotor and a nacelle. The Archimedes rotor is located in the combined wake region of the main rotor and the nacelle and is coaxially and fixedly connected to the main rotor. The parameter design method includes: Obtain the second design input parameters, which include the rated speed of the main wind turbine, the radius of the Archimedes wind turbine, the target installation distance, and the critical angle of attack; Based on the combined wake model, the target wake wind speed at the target installation distance is determined. The combined wake model characterizes the superposition relationship between the main wake of the main wind turbine and the local wake of the nacelle. The combined wake model includes a main wake model and a local wake model. The main wake model is used to describe the velocity distribution of the main wake formed after the main wind turbine extracts energy, and the local wake model is used to describe the center velocity loss caused by the nacelle. Based on the rated rotational speed, the radius of the Archimedes wind turbine, and the target wake velocity, the critical tip speed ratio is determined. Based on the critical tip speed ratio and the critical angle of attack, the target installation angle of the Archimedes wind turbine is determined.

8. The parameter design method according to claim 7, characterized in that, The second design input parameters also include the number of blades and the solidity of the Archimedes wind turbine. After determining the target installation angle of the Archimedes wind turbine, the following is also included: The target pitch of the Archimedes wind turbine is determined based on the target installation angle, the radius of the Archimedes wind turbine, the number of blades, and the solidity.

9. The parameter design method according to claim 7 or 8, characterized in that, The target installation angle, the critical angle of attack, and the critical tip speed ratio satisfy the following relationship: in, Install the target angle. The critical tip speed ratio is given. The critical angle of attack is denoted as .

10. The parameter design method according to claim 9, characterized in that, The critical angle of attack ranges from -8° to -5°.

11. The parameter design method according to claim 7 or 8, characterized in that, The critical tip speed ratio satisfies the following relationship with the rated rotational speed, the radius of the Archimedes wind turbine, and the target wake speed: in, The critical tip speed ratio is given. The rated speed, Let the radius of the Archimedes wind turbine be _____. Let be the target wake velocity.

12. The parameter design method according to claim 7 or 8, characterized in that, The wake wind speed output by the combined wake model satisfies the following relationship: in, The axial distance output by the combined wake model The wake wind speed at the location, The axial distance output by the main wake model The main wake wind speed at the location, The central velocity deficit coefficient, The axial distance is [the distance between the two points]. To recover the feature length of the velocity, For free-flowing wind speed, The main wind turbine thrust coefficient, The wake expansion coefficient is... The radius of the main wind turbine is given.

13. An aerodynamic braking method for a wind turbine, characterized in that, The wind turbine includes a main rotor and a nacelle. An Archimedes wind turbine is provided in the combined wake region of the main rotor and the nacelle. The Archimedes wind turbine is coaxially and fixedly connected to the main rotor. The parameters of the Archimedes wind turbine are determined based on the parameter design method of any one of claims 1 to 12. The aerodynamic braking method includes: When the operating speed of the main wind turbine is lower than its rated speed, the Archimedes wind turbine is in a positive torque state to assist acceleration. When the operating speed is equal to the rated speed, the Archimedes wind turbine is in a zero-torque critical state; When the operating speed is greater than the rated speed, the Archimedes windmill is in a negative torque state to perform pneumatic braking.

14. A computer storage medium, characterized in that, The computer storage medium stores instructions or programs that, when executed by at least one processor, cause the at least one processor to perform the method as described in any one of claims 1 to 12.

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