Fan blade water drop three-dimensional freezing coefficient calculation method and system

Abstract

The invention discloses a fan blade water drop three-dimensional freezing coefficient calculation method and system, and relates to the technical field of wind power generation blade icing simulation, and the method comprises the steps: drawing a surface grid for a target region, and obtaining related data; solving an external flow field of the three-dimensional blade based on related data to obtain airflow and water drop speed distribution, and further calculating a collision coefficient of water drops on the surface of the blade; and in combination with environmental parameters, the supercooling water yield of each unit is calculated, and various heat energy changes of water drops in collision, capture and freezing processes are deeply solved. Accurately solving a water drop freezing coefficient of each unit on the surface of the fan blade by establishing a heat balance equation; carrying out rationality correction on the calculated freezing coefficient; according to the method, the water drop freezing coefficient is calculated through the mass balance and the heat balance of the water drops in the three-dimensional surface domain, convenience is provided for simulation and further updating of the icing form of the fan blade, the icing prediction precision can be effectively improved, the fan design is optimized, and a powerful basis is provided for the anti-icing technology.

Description

Technical Field

[0001] The present invention relates to the technical field of wind power generation blade ice coating simulation, and in particular to a method and system for calculating a three-dimensional freezing coefficient of water droplets on a wind turbine blade. Background Art

[0002] In recent years, wind power generation has become an important part of global renewable energy. Wind power generation technology is constantly improving and innovating, such as increasing the height of wind turbines, improving wind turbine efficiency, reducing costs, and providing reliable safety. According to the China Wind Energy Industry Association, icing is one of the main problems facing wind power generation, and it causes great losses every year. In order to solve this problem, many researchers at home and abroad have carried out relevant technical research and application, such as developing anti-icing fluids and heating devices. In addition, China is also strengthening the construction of monitoring and early warning systems to timely predict and respond to possible icing weather to reduce losses.

[0003] Wind turbines have special operating conditions, and the monitoring and early warning mechanism for blade icing is imperfect. Simulating its growth form and rate based on environmental conditions is an important means. Currently, the most widely used method is to use CFD fluid mechanics simulation software to simulate the flow field analysis, water droplet collision and freezing involved in wind turbine icing. However, the process is relatively complicated, and the wind turbines are large in size and have a large number of grids, which has certain requirements on computer performance and calculation time. This has restricted the application of this technology to icing prediction and early warning in wind turbine projects to a certain extent. Summary of the invention

[0004] In view of the above-mentioned problems, the present invention is proposed.

[0005] Therefore, the technical problem solved by the present invention is: how to provide a fast, simple and accurate method for simulating icing of wind turbines, so as to realize the rapid calculation of ice thickness of wind turbine blades and the iteration of ice morphology, thereby providing technical support for wind turbine icing simulation.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0007] In a first aspect, an embodiment of the present invention provides a method for calculating a three-dimensional freezing coefficient of a water droplet on a fan blade, comprising:

[0008] Drawing a surface mesh for the first target area to obtain a meshed data structure;

[0009] Based on the grid data structure, the external flow field of the three-dimensional blade is solved to obtain the external airflow velocity distribution and water droplet velocity distribution of the three-dimensional blade. The collision coefficient of the water droplet on the three-dimensional blade surface is calculated based on the force analysis and trajectory tracking of the water droplet.

[0010] Calculating the amount of supercooled water captured by each unit according to the collision coefficient and the first environmental parameter;

[0011] Combined with the captured amount of supercooled water, the heat energy involved in the collision, capture and freezing of water droplets is solved, and the gain and loss values ​​of various heat energies are calculated;

[0012] Based on the various heat energy gain and loss values, the heat balance equation in the control unit is established to solve the water drop freezing coefficient of each unit on the surface of the fan blade;

[0013] Correct unreasonable values ​​in the calculated water drop freezing coefficient.

[0014] As a preferred solution for the calculation method of the three-dimensional freezing coefficient of water droplets on fan blades,

[0015] The first target area is a cross section or an entire area of ​​a target wind turbine blade.

[0016] As a preferred solution for the calculation method of the three-dimensional freezing coefficient of water droplets on fan blades,

[0017] The calculation of the collision coefficient of water droplets on the three-dimensional blade surface includes:

[0018] The boundary processing method is used to solve the external flow field of the three-dimensional blade, and the distribution of the airflow velocity u and the water droplet velocity v of the three-dimensional blade are obtained. The collision coefficient of the water droplet on the three-dimensional blade surface is obtained based on the force analysis and trajectory tracking of the water droplet.

[0019] As a preferred solution for the calculation method of the three-dimensional freezing coefficient of water droplets on fan blades,

[0020] The calculation of the supercooled water capture amount of each unit includes:

[0021] The first environmental parameters include the water drop collision coefficient β1, wind speed U, liquid water content in the air w (kg / m 3 ) and water drop movement position information;

[0022] Calculate the supercooled water capture of each unit, the water droplet capture M of unit i d It is expressed as:

[0023] (M d ) i =wU(β1) i (S1) i ,i=1,2,3...n

[0024] Among them, U represents wind speed and w represents the liquid water content in the air.

[0025] As a preferred solution for the calculation method of the three-dimensional freezing coefficient of water droplets on fan blades,

[0026] The calculation of various heat energy gain and loss values ​​includes:

[0027] Solve the convective heat transfer q involved in the collision, capture, and freezing of water droplets c , the heat carried away by evaporating water q e , the heat required to heat the supercooled water droplets q w , heat loss due to radiation q r 、The kinetic energy of water drop collision is converted into heat q m and freezing release latent heat q f , expressed as:

[0028] q c =S j ·h c (T w -T)

[0029] Among them, S j is the area of ​​the fan surface control unit, in m 2 ;h c is the convective heat transfer coefficient, in W / (m 2 ℃); T w and T are the fan blade surface temperature and ambient temperature, respectively, in K;

[0030]

[0031] Where χ is the evaporation coefficient, the unit is J / (m 2 ·kPa); e(T) is the saturated water vapor pressure on the fan blade surface at temperature T, in kPa; L e The temperature is T w The latent heat of vaporization or sublimation at the time of evaporation is expressed in J / kg; C a is the specific heat of air, measured in J / (kg·℃); P is the atmospheric pressure, measured in kPa.

[0032] q w =S j β1VwC w (T w -T)

[0033] q r =4εσ R T 3 S j ·(T w -T)

[0034]

[0035] q f =β3·M d ·Lf

[0036] Among them, C w is the specific heat of water, in J / (kg·℃); V is the water droplet impact velocity, in m / s; emissivity ε=0.95; σ R is the Stefan-Boltzmann constant; β3 is the water drop freezing coefficient of the control unit; L f is the latent heat of melting of ice, in J / kg.

[0037] As a preferred solution for the calculation method of the three-dimensional freezing coefficient of water droplets on fan blades,

[0038] The heat balance equation in the control unit is expressed as:

[0039]

[0040] As a preferred solution for the calculation method of the three-dimensional freezing coefficient of water droplets on fan blades,

[0041] The correction of the unreasonable value in the calculated water drop freezing coefficient includes:

[0042] If the calculated water drop freezing coefficient is greater than or equal to 1, it means that the water droplets are completely frozen in the control unit and the unit has a freezing capacity greater than the current amount of water droplets obtained, and it is corrected to 1; if the calculated water drop freezing coefficient is less than 0, it is corrected to 0.

[0043] In a second aspect, an embodiment of the present invention provides a system for calculating a three-dimensional freezing coefficient of water droplets on a wind turbine blade, comprising:

[0044] A data structure acquisition module, used for drawing a surface mesh for the first target area to obtain a meshed data structure;

[0045] The collision coefficient acquisition module is used to solve the external flow field of the three-dimensional blade based on the grid data structure, obtain the external airflow velocity distribution and water droplet velocity distribution of the three-dimensional blade, and calculate the collision coefficient of the water droplet on the three-dimensional blade surface based on the force analysis and trajectory tracking of the water droplet;

[0046] A supercooled water capture amount acquisition module, used to calculate the supercooled water capture amount of each unit according to the collision coefficient and the first environmental parameter;

[0047] A thermal energy calculation module is used for capturing the supercooled water, solving the thermal energy involved in the collision, capture and freezing of water droplets, and calculating various thermal energy gain and loss values;

[0048] The freezing coefficient calculation module is used to establish the heat balance equation in the control unit based on the various heat energy gain and loss values, and solve the water drop freezing coefficient of each unit on the surface of the fan blade;

[0049] The correction module is used to correct the unreasonable value of the calculated water drop freezing coefficient.

[0050] In a third aspect, an embodiment of the present invention provides a computing device, including:

[0051] Memory and processor;

[0052] The memory is used to store computer executable instructions, and the processor is used to execute the computer executable instructions. When the one or more programs are executed by the one or more processors, the one or more processors implement the method for calculating the three-dimensional freezing coefficient of water droplets on wind blades as described in any embodiment of the present invention.

[0053] In a fourth aspect, an embodiment of the present invention provides a computer-readable storage medium storing computer-executable instructions, which, when executed by a processor, implement the method for calculating the three-dimensional freezing coefficient of water droplets on wind turbine blades.

[0054] Beneficial effects of the invention: The invention provides a method for calculating the local three-dimensional freezing coefficient of water droplets in the icing process of wind turbine blades. The method calculates the freezing coefficient of water droplets through the mass balance and thermal balance of water droplets in a three-dimensional surface area, which facilitates the simulation and further updating of the icing morphology of wind turbine blades. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative labor.

[0056] Figure 1 It is an overall flow chart of the method for calculating the three-dimensional freezing coefficient of water droplets on fan blades according to the first embodiment of the present invention;

[0057] Figure 2 is a schematic diagram of a mesh surface of a fan blade in a simulation example of a method for calculating a three-dimensional freezing coefficient of a water droplet on a fan blade according to a second embodiment of the present invention;

[0058] Figure 3 It is a schematic diagram of a method for calculating a local water droplet collision coefficient on a fan blade surface in a simulation example of a method for calculating a three-dimensional freezing coefficient of water droplets on a fan blade according to a second embodiment of the present invention;

[0059] Figure 4It is a distribution diagram of the freezing coefficient of water droplets on the surface of a fan blade in a simulation example of a method for calculating the three-dimensional freezing coefficient of water droplets on a fan blade described in the second embodiment of the present invention. DETAILED DESCRIPTION

[0060] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the drawings of the specification. Obviously, the described embodiments are part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary persons in the art without creative work should fall within the scope of protection of the present invention.

[0061] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0062] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0063] Example 1

[0064] Reference Figure 1 , which is the first embodiment of the present invention, provides a method for calculating the three-dimensional freezing coefficient of water droplets on fan blades, comprising:

[0065] S1: Draw a surface mesh for the first target area to obtain a gridded data structure;

[0066] S2: Based on the grid data structure, solve the external flow field of the three-dimensional blade to obtain the external airflow velocity distribution and water droplet velocity distribution of the three-dimensional blade. Calculate the collision coefficient of the water droplet on the three-dimensional blade surface based on the force analysis and trajectory tracking of the water droplet;

[0067] S3: calculating the amount of supercooled water captured by each unit according to the collision coefficient and the first environmental parameter;

[0068] S4: Based on the captured amount of supercooled water, the heat energy involved in the collision, capture and freezing of water droplets is solved, and the gain and loss values ​​of various heat energies are calculated;

[0069] S5: Based on various heat energy gain and loss values, a heat balance equation is established in the control unit to solve the water drop freezing coefficient of each unit on the surface of the fan blade;

[0070] S6: Correct unreasonable values ​​in the calculated water drop freezing coefficient.

[0071] In the embodiment of the present application, the above step S1 includes the following sub-steps A1-A2;

[0072] In A1: the first target area is selected as the target wind turbine blade cross section or the entire area.

[0073] In A2: the gridded data structure is a three-dimensional surface mesh data set, each surface mesh unit is a triangle, and the three-dimensional surface mesh data set is a data structure composed of vertices, edges, faces and face normal vectors.

[0074] In another possible implementation, the meshing data structure may use a polygonal mesh in addition to a triangular mesh to improve calculation accuracy;

[0075] In another possible implementation, the gridded data structure may also be an adaptive grid: the grid density is dynamically adjusted according to flow field characteristics to improve computational efficiency and accuracy.

[0076] In another possible implementation, the gridded data structure may also be an unstructured grid: an unstructured grid is used to accommodate blades with complex geometric shapes.

[0077] In the embodiment of the present application, the above step S2 includes the following sub-steps B1-B2;

[0078] In B1: the boundary processing method is used to solve the external flow field of the three-dimensional blade, and the distribution of the airflow velocity u and the water droplet velocity v of the three-dimensional blade are obtained;

[0079] In the embodiment of the present application, the boundary processing method used is the boundary element method;

[0080] In another possible implementation, solving the three-dimensional blade external flow field may also be achieved by a computational fluid dynamics (CFD) method: by solving the Navier-Stokes equations to simulate the movement of the fluid in the three-dimensional blade external flow field.

[0081] Exemplarily, the fluid domain is divided into discrete control volumes by the finite volume method (FVM), and the fluid motion equations in each control volume are solved; the fluid domain is divided into discrete finite elements by the finite element method (FEM), and the fluid motion equations in each finite element are solved; the flow field is solved by discretizing partial differential equations using the finite difference method (FDM).

[0082] It should be noted that this method is able to handle complex geometries and flow conditions and is applicable to high-speed and high-Reynolds number flows.

[0083] In another possible implementation, solving the external flow field of the three-dimensional blade can also be achieved by the Lagrangian particle tracking method: by tracking the motion trajectory of the water droplet particles in the flow field, the velocity and position of the water droplet are calculated.

[0084] Exemplary, Explicit Euler Method: Tracing the trajectory of a water droplet by explicitly computing the particle position and velocity at each time step.

[0085] Implicit method: Improves computational stability by implicitly solving the equations of motion for the particles.

[0086] It should be noted that this method can directly track the motion trajectory of water droplets and is suitable for studying the motion characteristics and collision behavior of water droplets.

[0087] In another possible implementation, solving the external flow field of the three-dimensional blade can also be achieved through the lattice Boltzmann method (LBM): solving the macroscopic flow field by simulating the microscopic particle motion of the fluid.

[0088] Exemplarily, the single relaxation time method (BGK model) simulates the collision and movement of particles through relaxation time; the multiple relaxation time method improves the accuracy and stability of the simulation through multiple relaxation times.

[0089] It should be noted that this method is applicable to complex geometries and multiphase flow problems, and has high computational efficiency.

[0090] In another possible implementation, solving the external flow field of the three-dimensional blade may also be achieved by using a vortex particle method: solving the flow field by simulating vortex particles in the fluid.

[0091] Exemplarily, vortex particle distribution: distribute the vortex energy in the fluid to discrete vortex particles, and simulate the flow field by solving the motion of each vortex particle; vortex particle weighting: calculate the motion of vortex particles and vortex intensity through a weighting function.

[0092] It should be noted that this method is applicable to problems with high Reynolds number flows and complex vortex structures.

[0093] In B2: The collision coefficient of the water droplet on the three-dimensional blade surface is obtained based on the force analysis and trajectory tracking of the water droplet.

[0094] Specifically, the collision coefficient calculation formula is:

[0095]

[0096] Among them, U is the wind speed, V1~V3 are the collision velocities of the three adjacent colliding water droplets, respectively, in m / s; S0 and S1 are the areas of the triangle connecting the coordinates of the initial positions of the three water droplets and the areas of the triangle connecting the collision points, respectively, in m 2 .

[0097] In the embodiment of the present application, the above step S3 includes the following sub-steps C1-C2;

[0098] In C1: the first environmental parameters are selected including the water droplet collision coefficient β1, wind speed U, liquid water content in the air w (kg / m 3 ) and water drop movement position information;

[0099] In C2: Calculate the supercooled water capture of each unit, the water droplet capture M of unit i d It is expressed as:

[0100] (M d ) i =wU(β1) i (S1) i ,i=1,2,3...n

[0101] Among them, U represents wind speed and w represents the liquid water content in the air.

[0102] In the embodiment of the present application, the above step S4 calculates the various heat energy gain and loss values, specifically: solving the convective heat transfer q involved in the collision, capture, and freezing process of the water droplets c , the heat carried away by evaporating water q e , the heat required to heat the supercooled water droplets q w , heat loss due to radiation q r 、The kinetic energy of water drop collision is converted into heat q m and freezing release latent heat q f , expressed as:

[0103] q c =S j ·h c (T w -T)

[0104] Among them, S j is the area of ​​the fan surface control unit, in m 2 ;h c is the convective heat transfer coefficient, in W / (m 2 ℃); T w and T are the fan blade surface temperature and ambient temperature, respectively, in K;

[0105]

[0106] Where χ is the evaporation coefficient, the unit is J / (m 2 ·kPa); e(T) is the saturated water vapor pressure on the fan blade surface at temperature T, in kPa; L e The temperature is T w The latent heat of vaporization or sublimation at the time of evaporation is expressed in J / kg; C a is the specific heat of air, measured in J / (kg·℃); P is the atmospheric pressure, measured in kPa.

[0107] q w =S j β1VwC w (T w -T)

[0108] q r =4εσ R T 3 S j ·(T w -T)

[0109]

[0110] q f =β3·M d ·L f

[0111] Among them, C w is the specific heat of water, in J / (kg·℃); V is the water droplet impact velocity, in m / s; emissivity ε=0.95; σ R is the Stefan-Boltzmann constant; β3 is the water drop freezing coefficient of the control unit; L f is the latent heat of melting of ice, in J / kg.

[0112] In the embodiment of the present application, the heat balance equation in the control unit in the above step S5 is expressed as:

[0113]

[0114] In the embodiment of the present application, in the above step S6, correcting the unreasonable value of the calculated water drop freezing coefficient includes:

[0115] If the calculated water drop freezing coefficient is greater than or equal to 1, it means that the water droplets are completely frozen in the control unit and the unit has a freezing capacity greater than the current amount of water droplets obtained, and it is corrected to 1; if the calculated water drop freezing coefficient is less than 0, it is corrected to 0.

[0116] The above is a schematic scheme of the method for calculating the three-dimensional freezing coefficient of water droplets on the fan blades of this embodiment. It should be noted that the technical scheme of the three-dimensional freezing coefficient calculation system of water droplets on the fan blades and the technical scheme of the three-dimensional freezing coefficient calculation method of water droplets on the fan blades belong to the same concept. For details not described in detail in the technical scheme of the three-dimensional freezing coefficient calculation system of water droplets on the fan blades of this embodiment, please refer to the description of the technical scheme of the three-dimensional freezing coefficient calculation method of water droplets on the fan blades.

[0117] The fan blade water droplet three-dimensional freezing coefficient calculation system in this embodiment includes:

[0118] A data structure acquisition module, used for drawing a surface mesh for the first target area to obtain a meshed data structure;

[0119] The collision coefficient acquisition module is used to solve the external flow field of the three-dimensional blade based on the grid data structure, obtain the external airflow velocity distribution and water droplet velocity distribution of the three-dimensional blade, and calculate the collision coefficient of the water droplet on the three-dimensional blade surface based on the force analysis and trajectory tracking of the water droplet;

[0120] A supercooled water capture amount acquisition module, used to calculate the supercooled water capture amount of each unit according to the collision coefficient and the first environmental parameter;

[0121] A thermal energy calculation module is used for capturing the supercooled water, solving the thermal energy involved in the collision, capture and freezing of water droplets, and calculating various thermal energy gain and loss values;

[0122] The freezing coefficient calculation module is used to establish the heat balance equation in the control unit based on the various heat energy gain and loss values, and solve the water drop freezing coefficient of each unit on the surface of the fan blade;

[0123] The correction module is used to correct the unreasonable value of the calculated water drop freezing coefficient.

[0124] This embodiment further provides a computing device, which is applicable to the case of a method for calculating a three-dimensional freezing coefficient of water droplets on a fan blade, and includes:

[0125] Memory and processor; the memory is used to store computer executable instructions, and the processor is used to execute computer executable instructions to implement the method for calculating the three-dimensional freezing coefficient of water droplets on wind turbine blades as proposed in the above embodiment.

[0126] This embodiment also provides a storage medium on which a computer program is stored. When the program is executed by a processor, the method for calculating the three-dimensional freezing coefficient of water droplets on wind turbine blades as proposed in the above embodiment is implemented.

[0127] The storage medium proposed in this embodiment and the method for calculating the three-dimensional freezing coefficient of water droplets on wind blades proposed in the above embodiment belong to the same inventive concept. The technical details not fully described in this embodiment can be referred to the above embodiment, and this embodiment has the same beneficial effects as the above embodiment.

[0128] Example 2

[0129] Reference Figure 2-Figure 4 , which is an embodiment of the present invention, provides a method for calculating the three-dimensional freezing coefficient of water droplets on fan blades. In order to verify the beneficial effects of the present invention, scientific demonstration is carried out through simulation experiments.

[0130] Step 1: Draw a surface mesh for the target wind turbine blade cross section or the entire area to obtain a three-dimensional surface mesh data set A. Each surface mesh unit is a triangle, such as Figure 2 As shown, set A is a data structure consisting of vertices, edges, faces, and face normal vectors;

[0131] Step 2: Use the boundary element method to solve the external flow field of the three-dimensional blade, obtain the distribution of the three-dimensional blade external airflow velocity u and the water droplet velocity v, and obtain the collision coefficient of the water droplet on the three-dimensional blade surface based on the force analysis and trajectory tracking of the water droplet. The collision coefficient calculation formula is:

[0132]

[0133] like Figure 3 As shown in the figure, U is the wind speed, V1~V3 are the collision velocities of the three adjacent colliding water droplets, m / s; S0 and S1 are the areas of the triangles connecting the initial position coordinates (A, B, C) of the three water droplets and the areas of the triangles connecting the collision points (A1, B1, C1), m 2 .

[0134] Step 3: According to the water drop collision coefficient β1, wind speed U, liquid water content in the air w (kg / m 3 ) and other environmental parameters to calculate the supercooled water capture of each unit, the water droplet capture M of unit i d It can be calculated by the following formula:

[0135] (M d ) i =wU(β1) i (S1) i ,i=1,2,3...n

[0136] Step 4: Solve the convective heat transfer q involved in the collision, capture, and freezing process of water droplets c , the heat carried away by evaporating water q e , the heat required to heat the supercooled water droplets q w , heat loss due to radiation qr 、The kinetic energy of water drop collision is converted into heat q m and freezing release latent heat q f The values ​​of heat gain and loss etc.

[0137] q c =S j ·h c (T w -T)

[0138] Among them, S j is the area of ​​the fan surface control unit, m 2 ;h c is the convective heat transfer coefficient, W / (m 2 ℃); T w and T are the fan blade surface temperature and ambient temperature, K, respectively;

[0139]

[0140] Where χ is the evaporation coefficient, J / (m 2 ·kPa); e(T) is the saturated water vapor pressure on the fan blade surface at temperature T, kPa; L e The temperature is T w Latent heat of evaporation or sublimation, J / kg; C a is the specific heat of air, J / (kg·℃); P is the atmospheric pressure, kPa.

[0141] q w =S j β1VwC w (T w -T)

[0142] q r =4εσ R T 3 S j ·(T w -T)

[0143]

[0144] q f =β3·M d ·L f

[0145] Among them, C w is the specific heat of water, J / (kg·℃); V is the water droplet impact velocity, m / s; emissivity ε=0.95; σ R is the Stefan-Boltzmann constant. β3 is the water drop freezing coefficient of the control unit; L f is the latent heat of melting of ice, J / kg.

[0146] Step 5: Establish the heat balance equation in the control unit and solve the water drop freezing coefficient of each unit on the surface of the fan blade. The heat balance equation can be expressed as:

[0147] q c +q e +q w +q r =q m +q f

[0148]

[0149] Step 6: Correct the unreasonable value of the water drop freezing coefficient calculation. If the calculated β3 is greater than or equal to 1, it means that the water droplets are completely frozen in the control unit, and the unit has a freezing capacity greater than the current amount of water droplets obtained, and β3 is corrected to 1; if β3 is less than 0, it is corrected to 0.

[0150] like Figure 4 As shown in the figure, it is a distribution diagram of the freezing coefficient of water droplets on the surface of the wind turbine blade, which intuitively shows the distribution of the freezing coefficient of water droplets on the surface of the blade, and provides an intuitive basis for the simulation and design optimization of the ice covering morphology of the blade.

[0151] In summary, the method for calculating the three-dimensional freezing coefficient of water droplets on wind turbine blades provided by the present invention can effectively improve the accuracy of ice prediction, optimize wind turbine design, and provide a strong basis for anti-icing technology, with significant beneficial effects.

[0152] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for calculating the three-dimensional freezing coefficient of water droplets on fan blades, characterized in that: include: Drawing a surface mesh for the first target area to obtain a meshed data structure; Based on the grid data structure, the external flow field of the three-dimensional blade is solved to obtain the external airflow velocity distribution and water droplet velocity distribution of the three-dimensional blade. The collision coefficient of the water droplet on the three-dimensional blade surface is calculated based on the force analysis and trajectory tracking of the water droplet. Calculating the amount of supercooled water captured by each unit according to the collision coefficient and the first environmental parameter; Combined with the captured amount of supercooled water, the heat energy involved in the collision, capture and freezing of water droplets is solved, and the gain and loss values ​​of various heat energies are calculated; Based on the various heat energy gain and loss values, the heat balance equation in the control unit is established to solve the water drop freezing coefficient of each unit on the surface of the fan blade; Correct unreasonable values ​​in the calculated water drop freezing coefficient.

2. The method for calculating the three-dimensional freezing coefficient of water droplets on fan blades according to claim 1, characterized in that: The first target area is a cross section or an entire area of ​​a target wind turbine blade.

3. The method for calculating the three-dimensional freezing coefficient of water droplets on fan blades according to claim 2, characterized in that: The calculation of the collision coefficient of water droplets on the three-dimensional blade surface includes: The boundary processing method is used to solve the external flow field of the three-dimensional blade, and the distribution of the airflow velocity u and the water droplet velocity v of the three-dimensional blade are obtained. The collision coefficient of the water droplet on the three-dimensional blade surface is obtained based on the force analysis and trajectory tracking of the water droplet.

4. The method for calculating the three-dimensional freezing coefficient of water droplets on fan blades according to claim 3, characterized in that: The calculation of the supercooled water capture amount of each unit includes: The first environmental parameters include the water drop collision coefficient β1, wind speed U, liquid water content in the air w (kg / m 3 ) and water drop movement position information; Calculate the supercooled water capture of each unit, the water droplet capture M of unit i d It is expressed as: (M d ) i =wU(β1) i (S1) i ,i=1,2,3...n Among them, U represents wind speed and w represents the liquid water content in the air.

5. The method for calculating the three-dimensional freezing coefficient of water droplets on fan blades according to claim 4, characterized in that: The calculation of various heat energy gain and loss values ​​includes: Solve the convective heat transfer q involved in the collision, capture, and freezing of water droplets c , the heat carried away by evaporating water q e , the heat required to heat the supercooled water droplets q w , heat loss due to radiation q r 、The kinetic energy of water drop collision is converted into heat q m and freezing release latent heat q f , expressed as: q c =S j ·h c (T w -T) Among them, S j is the area of ​​the fan surface control unit, in m 2 ;h c is the convective heat transfer coefficient, in W / (m 2 ℃); T w and T are the fan blade surface temperature and ambient temperature, respectively, in K; Where χ is the evaporation coefficient, the unit is J / (m 2 ·kPa); e(T) is the saturated water vapor pressure on the fan blade surface at temperature T, in kPa; L e The temperature is T w The latent heat of vaporization or sublimation at the time of evaporation is expressed in J / kg; C a is the specific heat of air, measured in J / (kg·℃); P is the atmospheric pressure, measured in kPa. q w =S j ·β1VwC w (T w -T) q r =4εσ R T 3 S j ·(T w -T) q f =β3·M d ·L f Among them, C w is the specific heat of water, in J / (kg·℃); V is the water droplet impact velocity, in m / s; emissivity ε=0.95; σ R is the Stefan-Boltzmann constant; β3 is the water drop freezing coefficient of the control unit; L f is the latent heat of melting of ice, in J / kg.

6. The method for calculating the three-dimensional freezing coefficient of water droplets on fan blades according to claim 5, characterized in that: The heat balance equation in the control unit is expressed as:

7. The method for calculating the three-dimensional freezing coefficient of water droplets on fan blades according to claim 6, characterized in that: The correction of the unreasonable value in the calculated water drop freezing coefficient includes: If the calculated water drop freezing coefficient is greater than or equal to 1, it means that the water droplets are completely frozen in the control unit and the unit has a freezing capacity greater than the current amount of water droplets obtained, and it is corrected to 1; if the calculated water drop freezing coefficient is less than 0, it is corrected to 0.

8. A system using the method for calculating the three-dimensional freezing coefficient of water droplets on a fan blade according to any one of claims 1 to 7, characterized in that: include: A data structure acquisition module, used for drawing a surface mesh for the first target area to obtain a meshed data structure; The collision coefficient acquisition module is used to solve the external flow field of the three-dimensional blade based on the grid data structure, obtain the external airflow velocity distribution and water droplet velocity distribution of the three-dimensional blade, and calculate the collision coefficient of the water droplet on the three-dimensional blade surface based on the force analysis and trajectory tracking of the water droplet; A supercooled water capture amount acquisition module, used to calculate the supercooled water capture amount of each unit according to the collision coefficient and the first environmental parameter; A thermal energy calculation module is used for capturing the supercooled water, solving the thermal energy involved in the collision, capture and freezing of water droplets, and calculating various thermal energy gain and loss values; The freezing coefficient calculation module is used to establish the heat balance equation in the control unit based on the various heat energy gain and loss values, and solve the water drop freezing coefficient of each unit on the surface of the fan blade; The correction module is used to correct the unreasonable value of the calculated water drop freezing coefficient.

9. A computing device comprising: Memory and processor; The memory is used to store computer executable instructions, and the processor is used to execute the computer executable instructions. When the computer executable instructions are executed by the processor, the steps of the method for calculating the three-dimensional freezing coefficient of water droplets on wind blades described in any one of claims 1 to 7 are implemented.

10. A computer-readable storage medium storing computer-executable instructions, which, when executed by a processor, implement the steps of the method for calculating the three-dimensional freezing coefficient of water droplets on wind turbine blades as described in any one of claims 1 to 7.

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