Search

CN-121997813-A - Pneumatic characteristic calculation method for vertical axis wind turbine

CN121997813ACN 121997813 ACN121997813 ACN 121997813ACN-121997813-A

Abstract

The invention discloses a method for calculating aerodynamic characteristics of a vertical axis wind turbine, which comprises the steps of establishing a computational fluid dynamics model and a free vortex wake model, forming interaction, segmenting a blade, establishing a two-dimensional local area, initializing flow field and vortex wake parameters, calculating the induction flow velocity sum of each vortex element at the center of the local area and the far-field incoming flow velocity to be loaded to boundary nodes, enabling an airfoil to act equivalently as point vortex and dipole flow at the center of the circle, loading the induction velocities of the point vortex and the dipole flow at the boundary nodes, calculating the fluid mechanics parameters of the flow in each two-dimensional local area, integrating the airfoil surface pressure to obtain lifting force, calculating the circulation to update the point vortex intensity, and calculating the dipole flow intensity through the flow velocities of three specific observation points and updating. The invention provides the pneumatic characteristic calculation method of the vertical axis wind turbine, which has high calculation efficiency and reliable precision, and the pneumatic characteristic of the vertical axis wind turbine is accurately obtained with less calculation amount, so that powerful support is provided for structural design and optimization.

Inventors

  • HAO WENXING
  • JIN DONGLIANG
  • LUO JIAN
  • MAO QIANYU
  • TANG YI
  • CHAI YANFU
  • XU GAOLEI

Assignees

  • 嵊州市绍大机电创新研究院
  • 绍兴文理学院

Dates

Publication Date
20260508
Application Date
20260107

Claims (10)

  1. 1. The method for calculating the aerodynamic characteristics of the vertical axis wind turbine is characterized by comprising the following steps of: Step 1, establishing a computational fluid dynamics model and a free vortex trail model, forming interaction, segmenting a blade, establishing a two-dimensional local area, and initializing flow field and vortex trail parameters; step2, calculating the induction flow velocity sum of each vortex element in the center of a local area and loading the induction flow velocity sum and the far-field incoming flow velocity sum to boundary nodes; step 3, the airfoil effect is equivalent to point vortex and dipole flow at the center of a circle, and the induction speeds of the point vortex and the dipole flow at boundary nodes are loaded; step 4, calculating hydrodynamic parameters of the flow in each two-dimensional local area; step 5, integrating the airfoil surface pressure to obtain lift force, and calculating the annular quantity to update the point vortex intensity; step 6, calculating dipole flow intensity through the flow velocity of three specific observation points and updating; and 7, comparing the current airfoil ring quantity with the airfoil ring quantity in the previous iteration step, checking whether the current airfoil ring quantity reaches a convergence index, repeating the steps 3-6 if the current airfoil ring quantity does not converge, and updating the wake vortex element if the current airfoil ring quantity does not converge.
  2. 2. The method for calculating aerodynamic characteristics of a vertical axis wind turbine according to claim 1, further comprising the step of 8 judging according to time, ending calculation if the set time is reached, otherwise, entering the next time step to repeat the above steps.
  3. 3. The method for calculating aerodynamic characteristics of a vertical axis wind turbine according to claim 1, wherein in step 1, the computational fluid dynamics model is built based on a wiener-stokes equation, a two-dimensional local area is meshed, and a turbulence model is selected.
  4. 4. A method for calculating aerodynamic characteristics of a vertical axis wind turbine according to claim 3, wherein in step 1, the free vortex trail model is established based on helmholtz correlation theorem, pioshal law and kuta-ju kowski theorem.
  5. 5. The method of claim 1, wherein in step 1, the two-dimensional local area is circular, and the airfoil is centered about 0.25c from the leading edge, 1.5c is the radius, and c is the airfoil chord length.
  6. 6. The method for calculating aerodynamic characteristics of a vertical axis wind turbine according to claim 1, wherein the vortex elements comprise wake vortex elements and attached vortex elements representing blades, the intensity of point vortex is equal to the annular quantity of an airfoil, the induction speed direction of the point vortex is tangential to a boundary circle, and the induction speed of the point vortex is as follows: Γ is the point vortex intensity and R is the local area radius.
  7. 7. The method for calculating aerodynamic characteristics of a vertical axis wind turbine according to claim 1, wherein in step 3, the induced velocity of the dipole flow is calculated based on local coordinates, divided into induced velocities in x ', y' directions, The induction speed in the x' direction is : The induction speed in the y' direction is : The local origin of coordinates is located at the center of the region, and the x' axis direction is consistent with the relative flow velocity direction of the wing profile.
  8. 8. The method for calculating aerodynamic characteristics of a vertical axis wind turbine according to claim 1, wherein in step 5, the airfoil surface fluid pressure is integrated to obtain aerodynamic force Fx in x direction and aerodynamic force Fy in y direction, and the airfoil lift force calculation formula is: θ is the azimuth angle at which the airfoil is located, and φ is the inflow angle of the airfoil relative to the flow velocity.
  9. 9. The method for calculating aerodynamic characteristics of a vertical axis wind turbine according to claim 1, wherein in step 5, according to airfoil lift force, airfoil ring quantity is obtained based on kuta-schiff base theorem, and point vortex intensity Γ of a corresponding two-dimensional region is: ρ is the density of the fluid, Is the airfoil relative flow rate.
  10. 10. The method for calculating aerodynamic characteristics of a vertical axis wind turbine according to claim 1, wherein in step 7, when wake vortex elements are updated, intensity of a vortex element removed from a blade is equal to a reduction amount of a ring quantity of a blade element airfoil in a time step, and a corresponding calculation formula is as follows: for the intensity of the de-bulked vortex elements that are de-bulked at the nth time step, Equal to the corresponding airfoil ring number at the N-1 time step, And (5) corresponding airfoil ring quantity at the N time step.

Description

Pneumatic characteristic calculation method for vertical axis wind turbine Technical Field The invention relates to a vertical axis wind turbine, in particular to a method for calculating aerodynamic characteristics of a vertical axis wind turbine. Background Compared with a more common horizontal-axis wind turbine, the vertical-axis wind turbine has certain structural advantages, but has more complex aerodynamic characteristics, and unstable flow separation (namely dynamic stall) is caused mainly because the attack angle of the blades is in reciprocating change at all times in the rotating process of the wind wheel. At present, the required calculation amount is less, and the pneumatic characteristic calculation method based on an actuating disc or an actuating line-free vortex trail is widely applied to the horizontal axis wind turbine, so that the calculation accuracy in the vertical axis wind turbine is reduced due to the fact that the influence of dynamic stall cannot be accurately simulated. Therefore, accurate calculation of the aerodynamic characteristics of a vertical axis wind turbine still requires the help of a computational fluid dynamics method based on the Navier-Stokes equation that can directly simulate the flow evolution. The vertical axis wind turbine flow field has complex three-dimensional characteristics, and the computational fluid dynamics method needs to establish a three-dimensional computational domain which is large enough to meet Dirichlet boundary conditions, and meanwhile, grid encryption is carried out on the area near the blade tip so as to capture enough flow details. This results in a larger calculation for the method. Generally, for a single working condition, the Navier-Stokes equation is processed by Reynolds time, and is calculated by adopting a 64-core calculation workstation, and the calculation can be completed approximately 7-10 days. The larger calculated amount brings great difficulty to the structural design and optimization of the vertical axis wind turbine. In the prior art, ponta and other two-dimensional vertical axis wind turbine aerodynamic characteristic calculation methods are proposed, flow in a local area near an airfoil is calculated by adopting a finite element analysis method based on a potential flow Laplacian equation, wake evolution is calculated by adopting a free vortex wake theory, but the method cannot simulate flow separation and dynamic stall phenomena, the local area is rectangular, a loading mode of boundary induction speed is not defined, and the displacement effect of a blade on fluid is not considered, so that calculation accuracy is limited. There is therefore a need to propose a new solution to this problem. Disclosure of Invention The invention aims to solve the contradiction between large calculated amount and insufficient precision in the calculation of the aerodynamic characteristics of the conventional vertical axis wind turbine, provides the calculation method of the aerodynamic characteristics of the vertical axis wind turbine with high calculation efficiency and reliable precision, accurately obtains the aerodynamic characteristics of the vertical axis wind turbine with less calculated amount, and provides powerful support for structural design and optimization. In order to achieve the above purpose, the present invention adopts the following technical scheme: a method for calculating aerodynamic characteristics of a vertical axis wind turbine comprises the following steps: Step 1, establishing a computational fluid dynamics model and a free vortex trail model, forming interaction, segmenting a blade, establishing a two-dimensional local area, and initializing flow field and vortex trail parameters; step2, calculating the induction flow velocity sum of each vortex element in the center of a local area and loading the induction flow velocity sum and the far-field incoming flow velocity sum to boundary nodes; step 3, the airfoil effect is equivalent to point vortex and dipole flow at the center of a circle, and the induction speeds of the point vortex and the dipole flow at boundary nodes are loaded; step 4, calculating hydrodynamic parameters of the flow in each two-dimensional local area; step 5, integrating the airfoil surface pressure to obtain lift force, and calculating the annular quantity to update the point vortex intensity; step 6, calculating dipole flow intensity through the flow velocity of three specific observation points and updating; and 7, comparing the current airfoil ring quantity with the airfoil ring quantity in the previous iteration step, checking whether the current airfoil ring quantity reaches a convergence index, repeating the steps 3-6 if the current airfoil ring quantity does not converge, and updating the wake vortex element if the current airfoil ring quantity does not converge. The invention is further arranged to further comprise the step 8 of judging according to time, ending calculation if th