Ultra-large wind turbine generator thin-wall blade tip eddy current characteristic calculation method

Abstract

The invention relates to the field of wind turbine generator eddy current characteristic calculation, in particular to an ultra-large wind turbine generator thin-wall blade tip eddy current characteristic calculation method, which comprises the following steps: constructing an ultra-large wind turbine generator thin-wall blade surface model; jumping an inner-layer virtual grid through an interface grid eight-node search and interpolation scheme, searching for a gas grid closest to the virtual grid, constructing an interpolation region, and applying a boundary condition; modeling near wall surface flow, and reconstructing an air domain variable of a virtual grid through a wall surface model; and an auxiliary Lagrangian grid is introduced, normal and tangential reconstruction formats are constructed in combination with a turbulence wall surface model, and the vortex characteristics of the thin-wall blade tip of the ultra-large wind turbine generator are simulated. According to the method, through thin-wall blade surface model construction, thin-wall blade tip structure grid attribute recognition and wall surface analytic function combined large vortex simulation method, ultra-large wind turbine generator thin-wall blade tip vortex characteristics can be accurately captured.

Description

Technical Field

[0001] The invention relates to the field of eddy current characteristic calculation of wind turbines, and in particular to a method for calculating eddy current characteristic at the tip of a thin-walled blade of a super-large wind turbine. Background Art

[0002] The vortex characteristics of the tip of the thin-walled blade of a wind turbine refer to the airflow movement characteristics at the tip of the wind turbine blade. In the design and operation of wind turbines, the tip of the blade is an important area because it involves flow separation and vortex formation. These flow phenomena have an important impact on wind energy conversion efficiency and wind turbine load.

[0003] When the airflow encounters the tip of the blade, due to the sudden change in geometry, the airflow may separate and form vortices. These vortices will cause changes in the pressure distribution on the blade surface, which in turn affects the wind energy conversion efficiency. At the same time, the intensity and rotation direction of the vortex will also affect the load distribution of the blade. If not handled properly, it may cause excessive vibration or fatigue loads, affecting the stability and life of the wind turbine.

[0004] Therefore, it is necessary to calculate the vortex characteristics at the tip of thin-walled blades of wind turbines. In the process of large-scale development of wind turbines, the nonlinear characteristics of the vortex at the tip of blades are significantly enhanced as the blade size increases, accompanied by a certain amount of flow-induced noise, resulting in a decrease in the calculation accuracy of the vortex characteristics at the tip of thin-walled blades of super-large wind turbines. Summary of the invention

[0005] In order to solve the above problems, the present invention provides a method for calculating the vortex characteristics at the tip of a thin-walled blade of a super-large wind turbine generator set, which is used to accurately capture the vortex characteristics at the tip of a thin-walled blade of a super-large wind turbine generator set.

[0006] In order to achieve the above object, the technical solution of the present invention is as follows: A method for calculating the vortex characteristics at the tip of a thin-walled blade of a super-large wind turbine generator comprises the following steps:

[0007] Construct a thin-walled blade surface model for a super-large wind turbine, mesh the thin-walled blade surface model, track arbitrary deformation interfaces, identify virtual grids, gas grids, and solid grids through wind turbine blade isosurface functions, and reconstruct the air domain variable values ​​of the background virtual grid;

[0008] Through the eight-node search and interpolation scheme of the interface grid, the inner virtual grid is skipped, the gas grid closest to the virtual grid is searched, the interpolation area is constructed, and the object surface boundary conditions are applied;

[0009] The near-wall flow is further simulated by setting boundary conditions and wall functions, the air domain variables of the virtual grid are reconstructed using the wall model, and the slip velocity boundary conditions and shear stress boundary conditions are applied.

[0010] An auxiliary Lagrangian grid is introduced, and the normal and tangential reconstruction formats are constructed in combination with the turbulent wall model to impose slip velocity and shear stress boundary conditions near the wall, so as to provide the correct wall shear stress and zero normal flux boundary conditions for the large eddy simulation model and simulate the vortex characteristics at the tip of thin-walled blades of ultra-large wind turbines.

[0011] Furthermore, the thin-walled blade surface model of a super-large wind turbine is constructed by an adaptive radial basis function; and the thin-walled blade surface model is meshed by a virtual grid method.

[0012] Furthermore, the near-wall flow is accurately captured by constructing a wall analytical function based on the object surface boundary conditions.

[0013] Furthermore, the large eddy simulation turbulence model is solved in the entire field to obtain the large eddy viscosity at the center of all grid cells; an auxiliary Lagrangian grid is introduced into the fluid domain at a preset position away from the wall, and the variables of the Lagrangian points are calculated according to the eight-node interpolation template reconstruction format.

[0014] Furthermore, the variables at the Lagrangian point include velocity, pressure and large eddy viscosity.

[0015] Furthermore, the velocity of the Lagrangian point is decomposed into the tangential velocity and normal velocity along the wall. According to the tangential velocity and large eddy viscosity of the Lagrangian point, the wall shear stress and friction velocity are obtained by solving the wall function.

[0016] According to the normal velocity of the Lagrangian point, the impenetrable condition of the normal velocity is imposed on the wall, and according to the wall shear stress, the slip boundary condition of the wall is imposed, and the normal and tangential velocities of the virtual grid are calculated respectively;

[0017] The virtual grid pressure is calculated according to the Neumann boundary condition of the wall, and its large eddy viscosity is set equal to the large eddy viscosity of the Lagrangian point;

[0018] The Navier-Stokes equations are solved in the entire field to take into account the influence of severe turbulent flow near the wall.

[0019] Furthermore, the wall shear stress and friction velocity are obtained by solving the wall function through the projection method.

[0020] The above scheme has the following beneficial effects:

[0021] 1. The present invention simulates the vortex characteristics of the thin-walled blade tip of a super-large wind turbine by constructing a thin-walled blade surface model, identifying the thin-walled blade tip structure grid attributes, and combining the wall analytical function with the large eddy simulation method. It can accurately capture the vortex characteristics of the thin-walled blade tip of a super-large wind turbine, and solve the problem in the prior art that the blade tip vortex significantly enhances its nonlinear characteristics as the blade size increases, accompanied by certain flow-induced noise, resulting in a decrease in the calculation accuracy of the vortex characteristics of the thin-walled blade tip of a super-large wind turbine. The method for calculating the vortex characteristics of the thin-walled blade tip of a super-large wind turbine of the present invention can accurately simulate and predict the vortex characteristics of the tip of the wind turbine blade, including the size, shape, intensity and distribution of the vortex. Through this calculation method, the vortex characteristics of the tip of the wind turbine blade can be obtained, which has important reference value for optimizing the design of wind turbine blades, improving the efficiency and stability of wind turbines, and reducing noise and vibration.

[0022] 2. This solution, by using the wall analytical function to simulate the near-wall flow, can be used specifically to deal with complex fluid dynamics problems in the boundary layer, especially when dealing with flows with complex geometries (such as near the tip of a wind turbine blade). This method shows its unique advantages and application value. It solves the accuracy problem in current technology and further accurately simulates the flow near the wall through the large eddy simulation wall analytical function method, which can more accurately predict the behavior of the vortex.

[0023] 3. This solution introduces an auxiliary Lagrangian grid and constructs normal and tangential reconstruction formats in combination with the turbulent wall model to impose the slip velocity and shear stress boundary conditions near the wall. The characteristic is that the resolution of the near-wall flow is improved without significantly increasing the complexity of the Euler grid (main fluid grid). The present invention provides an innovative solution to the deficiencies of the prior art in accurately simulating the boundary layer. Through this new method, the turbulence effects in the boundary layer are more accurately simulated. Combined with the normal and tangential reconstruction formats, the present invention can more accurately simulate the behavior of the fluid near the wall, including the velocity distribution and the shear stress distribution, thereby improving the accuracy and reliability of the simulation.

[0024] Additional aspects and advantages of the present invention will be presented in the following description, some of which will be presented directly and others will become apparent in the course of a deeper understanding of the present invention or through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a flow chart of an embodiment of a method for calculating vortex characteristics at the tip of a thin-walled blade of a super-large wind turbine generator set according to the present invention;

[0026] Figure 2A schematic diagram of mesh identification at the tip of a super-large flexible thin-walled blade according to an embodiment of a method for calculating vortex characteristics at the tip of a super-large wind turbine thin-walled blade of the present invention;

[0027] Figure 3 A schematic diagram of the interface reconstruction format of an eight-node interpolation template of an embodiment of a method for calculating vortex characteristics at the tip of a thin-walled blade of a super-large wind turbine generator system according to the present invention;

[0028] Figure 4 It is a schematic diagram of a two-dimensional interface reconstruction method of a virtual grid method in an embodiment of a method for calculating vortex characteristics at the tip of a thin-walled blade of a super-large wind turbine generator set of the present invention. DETAILED DESCRIPTION

[0029] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are partial embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] The following is further described in detail through specific implementation methods:

[0031] Implementation example Figure 1 As shown: The calculation method of the vortex characteristics at the tip of the thin-walled blade of a super-large wind turbine includes the following steps:

[0032] The surface model of the thin-walled blade of a super-large wind turbine is constructed, the surface model of the thin-walled blade is meshed, the arbitrary deformation interface is tracked, and the virtual grid (GC), gas grid (AC) and solid grid (SC) are identified through the isosurface function. Figure 2 As shown, the air domain variable values ​​of the background virtual grid are reconstructed;

[0033] Specifically, the thin-walled blade surface model of a super-large wind turbine is constructed through an adaptive radial basis function. The thin-walled blade surface model of a super-large wind turbine can be used for aerodynamic performance analysis. By performing aerodynamic performance analysis on the thin-walled blade surface model, the performance of the wind turbine under different wind speeds and wind directions can be evaluated. This helps to optimize the blade design to improve the efficiency and energy output of the wind turbine.

[0034] The thin-walled blade surface model is meshed by the virtual mesh method. By dividing the thin-walled blade surface into small mesh units, the flow of fluid around the blade can be numerically simulated to understand the aerodynamic performance and pressure distribution. Secondly, through detailed meshing, the details of the geometric shape can be captured more accurately, improving the accuracy of the numerical simulation.

[0035] For thin-walled blade tip structures, special treatment is required. This method solves the problem of virtual grid points corresponding to multiple fluid variable values ​​or grid phase attribute identification errors based on background grid solution. Figure 2 Assuming that the slender thin-walled structure ABC, the surface points on the edges AB and AC can calculate the existence of two gas variable values ​​at the virtual grid point 2. The above problems will lead to incorrect application of thin-wall boundary conditions, resulting in reduced solution accuracy and even calculation divergence.

[0036] To solve the above problems, an eight-node search and interpolation scheme for interface mesh is proposed (see attached). Figure 3 , Attached Figure 3 In the figure, (a) the eight template points are all fluid grid points, and (b) the two interpolation template points are virtual grid points. Through the interface grid eight-node search and interpolation scheme, the inner virtual grid is skipped, the gas grid closest to the virtual grid is searched, the interpolation region is constructed, and the boundary conditions are imposed.

[0037] Then, the near-wall flow is accurately captured by constructing a wall analytical function on the object surface boundary condition, and the air domain variables of the virtual grid are reconstructed using the wall model. The slip velocity boundary condition and the shear stress boundary condition are applied, as shown in the attached figure. Figure 4 As shown, (a) linear interpolation, (b) analytical function modeling.

[0038] Finally, an auxiliary Lagrangian grid is introduced, and the normal and tangential reconstruction formats are constructed in combination with the turbulent wall model to impose slip velocity and shear stress boundary conditions near the wall, so as to provide the correct wall shear stress and zero normal flux boundary conditions for the large eddy simulation model and simulate the vortex characteristics at the tip of thin-walled blades of ultra-large wind turbines.

[0039] The specific implementation process is as follows:

[0040] The large eddy viscosity at the center of all grid cells is obtained by solving the large eddy simulation turbulence model in the whole field.

[0041] An auxiliary Lagrangian grid is introduced into the fluid domain at a preset distance from the wall, and the variables of the Lagrangian point (LP) are calculated according to the eight-node interpolation template reconstruction format; the variables of the Lagrangian point include velocity, pressure and large eddy viscosity.

[0042] The velocity at the Lagrangian point is decomposed into the tangential velocity and normal velocity along the wall. According to the tangential velocity and large eddy viscosity of the Lagrangian point, the wall shear stress and friction velocity are obtained by solving the wall function through the iterative method.

[0043] According to the normal velocity of the Lagrangian point, the impenetrable condition of the normal velocity is imposed on the wall, and according to the wall shear stress, the slip boundary condition of the wall is imposed, and the normal and tangential velocities of the virtual grid are calculated respectively;

[0044] The virtual grid pressure is calculated according to the Neumann boundary condition at the wall, and its large eddy viscosity is set equal to the large eddy viscosity of the Lagrangian point.

[0045] According to the surface characteristics of the airfoil, some pressure terms are ignored, and only the influence of velocity and other non-pressure terms (such as viscosity and external forces) are considered to obtain a predicted velocity field. This predicted velocity field is projected onto a velocity field that satisfies the divergence condition (i.e., sourceless and sinkless) through the projection method to construct a projection model, and then projected onto a velocity field that satisfies the divergence condition (i.e., sourceless and sinkless) to obtain a corrected velocity field. The Poisson equation is determined by the divergence condition and the predicted velocity field, and its solution is the pressure field that needs to be captured at the tip of the thin-walled blade. The pressure field obtained above is used to correct the predicted velocity field to obtain a velocity field that satisfies the Navier-Stokes equation. Finally, the Navier-Stokes equation is solved in the entire field to consider the influence of violent turbulent flow near the wall.

[0046] Through the above thin-walled blade surface model construction, thin-walled blade tip structure grid attribute identification, and wall analytical function combined with large eddy simulation method, the vortex characteristics of the thin-walled blade tip of the ultra-large wind turbine can be accurately simulated. Obviously, the above embodiments are intended to provide clear illustrative examples, rather than limitations on the implementation methods. For ordinary technicians in the field, based on the above description, other various forms of changes or adjustments can also be derived. Here, it is neither necessary nor practical to exhaust all possible implementation methods. Therefore, obvious changes or adjustments derived from the present invention are still within the scope of protection of the invention.

Claims

1. A method for calculating the vortex characteristics at the tip of thin-walled blades of ultra-large wind turbines, characterized in that: The steps include: Construct a thin-walled blade surface model for a super-large wind turbine, mesh the thin-walled blade surface model, track arbitrary deformation interfaces, identify virtual grids, gas grids, and solid grids through wind turbine blade isosurface functions, and reconstruct the air domain variable values ​​of the background virtual grid; Through the eight-node search and interpolation scheme of the interface grid, the inner virtual grid is skipped, the gas grid closest to the virtual grid is searched, the interpolation area is constructed, and the object surface boundary conditions are applied; The near-wall flow is further simulated by setting boundary conditions and wall functions, the air domain variables of the virtual grid are reconstructed using the wall model, and the slip velocity boundary conditions and shear stress boundary conditions are applied. An auxiliary Lagrangian grid is introduced, and the normal and tangential reconstruction formats are constructed in combination with the turbulent wall model to impose slip velocity and shear stress boundary conditions near the wall, so as to provide the correct wall shear stress and zero normal flux boundary conditions for the large eddy simulation model and simulate the vortex characteristics at the tip of thin-walled blades of ultra-large wind turbines.

2. The method for calculating the vortex characteristics of the thin-walled blade tip of a super-large wind turbine according to claim 1 is characterized in that: The surface model of thin-walled blades of super-large wind turbines is constructed by adaptive radial basis function; the surface model of thin-walled blades is meshed by virtual grid method.

3. The method for calculating the vortex characteristics of the thin-walled blade tip of a super-large wind turbine according to claim 1 is characterized in that: The near-wall flow is accurately captured by constructing a wall analytical function based on the object surface boundary conditions.

4. The method for calculating the vortex characteristics of the thin-walled blade tip of a super-large wind turbine according to claim 1 is characterized in that: The large eddy simulation turbulence model is solved in the whole field to obtain the large eddy viscosity at the center of all grid units; an auxiliary Lagrangian grid is introduced into the fluid domain at a preset position away from the wall, and the variables of the Lagrangian points are calculated according to the eight-node interpolation template reconstruction format.

5. The method for calculating the vortex characteristics of the thin-walled blade tip of a super-large wind turbine according to claim 4 is characterized in that: The variables at the Lagrangian point include velocity, pressure, and large eddy viscosity.

6. The method for calculating the vortex characteristics of the thin-walled blade tip of a super-large wind turbine according to claim 5 is characterized in that: The velocity of the Lagrangian point is decomposed into the tangential velocity and normal velocity along the wall. According to the tangential velocity and large eddy viscosity of the Lagrangian point, the wall shear stress and friction velocity are obtained by solving the wall function. According to the normal velocity of the Lagrangian point, the impenetrable condition of the normal velocity is imposed on the wall, and according to the wall shear stress, the slip boundary condition of the wall is imposed, and the normal and tangential velocities of the virtual grid are calculated respectively; The virtual grid pressure is calculated according to the Neumann boundary condition of the wall, and its large eddy viscosity is set equal to the large eddy viscosity of the Lagrangian point; The Navier-Stokes equations are solved in the entire field to take into account the influence of severe turbulent flow near the wall.

7. The method for calculating the vortex characteristics of the thin-walled blade tip of a super-large wind turbine according to claim 6 is characterized in that: The wall shear stress and friction velocity are obtained by solving the wall function through the projection method.

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