Method for determining key protection area of fan blade

Abstract

The invention provides a method for determining a key protection area of a fan blade, and the method comprises the following steps: S1, obtaining a blade model of a wind power motor in an actual working condition, importing the model into Ansys Fluent software, and dividing the blade model into a plurality of grids in the Ansys Fluent software; s2, acquiring environmental parameters, including environmental temperature, wind speed, humidity and rainfall, of an environment where the wind power motor is located in an actual working condition, and importing the environmental parameters into Ansys Fluent software to simulate operation of the wind power motor; s3, determining the icing thickness of each grid of the blade when the wind power motor is in simulated operation; s4, the chord length direction of the wind power motor blade is determined, and the icing thickness mean value of the multiple areas of the blade in the chord length direction is determined; s5, determining a lift coefficient and a resistance coefficient of each region of the fan blade based on the icing thickness mean value; and S6, finding out an area corresponding to the maximum lift coefficient value and the minimum resistance coefficient value as a key protection area.

Description

Technical Field

[0001] The invention relates to a method for protecting and processing fan blades, and in particular to a method for determining a key protection area of ​​a fan blade. Background Art

[0002] Wind power generation is widely used as a renewable and clean energy. With the popularization of wind power generation, the icing problem of wind turbines has become increasingly prominent.

[0003] Ice covering the blades of wind turbines will change the original aerodynamic shape, affect the aerodynamic performance of the blades, and reduce the power generation efficiency of the unit. At the same time, since ice covering different areas of the wind turbine has different effects on the aerodynamic performance of the blades, it is difficult to determine the key protection areas. Therefore, in the de-icing protection of wind turbines, comprehensive protection is generally adopted, which is a waste of resources. Another method is to determine the key protection areas based on experience, resulting in the wind turbine blades not being given targeted de-icing protection, so that the wind turbine is still damaged by ice covering.

[0004] Therefore, in order to solve the above technical problems, it is urgent to propose a new technical means. Summary of the invention

[0005] In view of this, an object of the present invention is to provide a method for determining the key protection area of ​​a wind turbine blade, by performing simulated operation through the airfoil of the actual wind turbine blade and the actual working environment of the wind turbine, and determining the key protection area through the ice mass and ice thickness in the simulated operation, thereby effectively improving the accuracy of determining the key protection area, providing an accurate reference for the de-icing protection of the wind turbine, facilitating the proposal of targeted de-icing plans, and reducing or even avoiding resource waste, and having strong adaptability.

[0006] The present invention provides a method for determining a key protection area of ​​a fan blade, comprising the following steps:

[0007] S1. Obtain a blade model of a wind turbine in actual working conditions, import the model into Ansys Fluent software, and divide the blade model into several grids in Ansys Fluent software;

[0008] S2. Obtain environmental parameters of the environment in which the wind turbine is located in actual working conditions, including ambient temperature, wind speed, humidity and rainfall, and import the environmental parameters into Ansys Fluent software to simulate the operation of the wind turbine;

[0009] S3. Determine the ice thickness of each grid of the blade of the wind turbine during the simulated operation;

[0010] S4. Determine the chord length direction of the wind turbine blade, and determine the average ice thickness of multiple regions of the blade along the chord length direction;

[0011] S5. Determine the lift coefficient and drag coefficient of each area of ​​the wind turbine blade based on the average ice thickness;

[0012] S6. Find the area corresponding to the maximum lift coefficient and the minimum drag coefficient as the key protection area.

[0013] Furthermore, the lift coefficient and drag coefficient are determined as follows:

[0014] C l = cosα(C dmax sinα+A2cotα);

[0015] C d =C dmax -cosα(C dmax cosα-B2);

[0016] Where: α represents the angle of attack, C l is the lift coefficient, C d represents the drag coefficient, C dmax is the maximum drag coefficient under the current fan blade airfoil; A2 and B2 are both coefficients;

[0017]

[0018] Where: α s is the stall angle of attack under the current blade airfoil, C ls is the stall angle of attack α s The lift coefficient under ds is the stall angle of attack α s The drag coefficient under

[0019] AR is the aspect ratio of the current grid, C ice is the average ice thickness in the chord length direction of the current grid, d i is the ice thickness of the i-th grid in the chord direction, n is the number of grids, and c is the chord length of the current wind turbine blade airfoil.

[0020] Furthermore, the ice thickness d is determined by the following method: i :

[0021]

[0022] Where: Δt is the ice cover time step, ρ ice represents the ice density, m ice is the ice mass and A is the grid length.

[0023] Furthermore, the ice density ρ ice Determined by the following formula:

[0024]

[0025] Where: V ∞ It represents the combined velocity of the incoming flow of the wind turbine; MVD is the median diameter of the water droplet;

[0026] ΔT s-f =T s -T f , T s is the fan blade surface temperature, T f The freezing temperature of water droplets.

[0027] Furthermore, the ice mass m is determined by the following method: ice :

[0028] Construct the mass balance equation within the grid:

[0029]

[0030] Where: m im is the mass of the supercooled water droplets impacting the grid, m in and m out are the water mass flowing into the grid and the water mass flowing out to the next grid, m eva is the mass of water evaporated;

[0031] m im =β·LWC·V ∞ ·A (2);

[0032] m out =(1-f)·∑m Add -m eva (3);

[0033]

[0034] Where: f is the freezing ratio of water droplets in the grid; L ew is the Lewis number, P sat-Ts and P sat-T are the blade mesh surface temperature T s The saturated water vapor pressure corresponding to the ambient temperature T;

[0035] Construct the energy balance equation within the grid:

[0036] ∑Q grid-in =Q im +Q in (5);

[0037] ∑Q Loss =Q eva +Q i +Q out +Q f +Q c (6);

[0038] ∑Q grid-in =∑Q Loss (7);

[0039] Qim is the energy brought by the supercooled water droplet hitting the grid, expressed as:

[0040]

[0041] Q in The energy brought by the water flowing into the grid is expressed as:

[0042] Q in =m in C w (T s(i-1) -T f ) (9);

[0043] Q eva The energy taken away by water evaporation is expressed as:

[0044] Q eva =m eva [C w ΔT s-f +L e ] (10);

[0045] Q out The energy taken away by the water flowing out of the grid is expressed as:

[0046] Q out =m out C w ΔT s-f (11);

[0047] Q f is the heat loss due to friction, expressed as:

[0048]

[0049] Q c is the heat removed by natural convection, expressed as:

[0050] Q c =-h c AΔT s (13);

[0051] T f is the freezing temperature of water droplets, T sis the blade surface temperature, T is the external ambient temperature, △T s-f =T s -T f ,△T s =TT s ,C a , C w , C i are the specific heats of air, water and ice respectively; L f , L e are the latent heat of melting and the latent heat of evaporation respectively; h c is the convective heat transfer coefficient. r is the recovery coefficient of dynamic heating, expressed as:

[0052] Pr is the Prandtl number. When the grid boundary layer is in the laminar region, n0=1 / 2; when it is in the turbulent region, n0=1 / 3;

[0053] Combine formula (1) and formula (13) to solve for the ice mass m ice .

[0054] The beneficial effects of the present invention are as follows: Through the present invention, simulated operation is performed through the airfoil of the actual wind turbine blade and the actual working environment of the wind turbine. In the simulated operation, the key protection area is determined by the ice mass and ice thickness, thereby effectively improving the accuracy of the key protection area determination, providing an accurate reference for the de-icing protection of the wind turbine, facilitating the proposal of targeted de-icing plans, reducing or even avoiding resource waste, and having strong adaptability. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] The present invention will be further described below in conjunction with the accompanying drawings and embodiments:

[0056] Figure 1 It is a flow chart of the present invention.

[0057] Figure 2 It is a schematic diagram of the fan blade of the present invention.

[0058] Figure 3 Schematic diagram of cell distribution. DETAILED DESCRIPTION

[0059] The present invention is further described in detail below:

[0060] The present invention provides a method for determining a key protection area of ​​a fan blade, comprising the following steps:

[0061] S1. Obtain a blade model of a wind turbine in actual working conditions, import the model into Ansys Fluent software, and divide the blade model into several grids in Ansys Fluent software;

[0062] S2. Obtain environmental parameters of the environment in which the wind turbine is located in actual working conditions, including ambient temperature, wind speed, humidity and rainfall, and import the environmental parameters into Ansys Fluent software to simulate the operation of the wind turbine;

[0063] S3. Determine the ice thickness of each grid of the blade of the wind turbine during the simulated operation;

[0064] S4. Determine the chord length direction of the wind turbine blade, and determine the average ice thickness of multiple regions of the blade along the chord length direction; Figure 2 As shown in the figure, the chord length direction and the distance from the top to the tail of the fan blade, that is, the straight line distance from the top to the root of the blade. However, some blades are not regular in shape. Therefore, when dividing the cells, a group of cells along the length of the blade are actually distributed along the curve. However, when calculating, the area is divided in the chord length direction represented by the straight line in the figure, and the result is as follows Figure 3 As shown: Figure 3 The middle is a partial schematic diagram of the blade surface after it is unfolded into a plane. Each square represents a grid. Assuming that the left side is the root of the blade and the right side is the top of the blade, then, after the actual chord length direction is unfolded, it is similar to a curve. At this time, the area corresponding to the chord length defense line is Figure 3 The area of ​​the grid through which the middle curve passes, then when calculating the average ice thickness, the average ice thickness of the grid through which the curve passes shall be used as the basis. Therefore, starting from the root of the blade to the top, there will be multiple such corresponding areas, and then corresponding calculations are performed on each area to determine the final key area.

[0065] S5. Determine the lift coefficient and drag coefficient of each area of ​​the wind turbine blade based on the average ice thickness;

[0066] S6. Find the area corresponding to the maximum lift coefficient and the minimum drag coefficient as the key protection area. Through the above method, the airfoil of the actual wind turbine blade and the actual working environment of the wind turbine are used to simulate the operation. In the simulated operation, the key protection area is determined by the ice mass and ice thickness, thereby effectively improving the accuracy of the key protection area, providing an accurate reference for the de-icing protection of the wind turbine, facilitating the proposal of targeted de-icing solutions, reducing or even avoiding resource waste, and having strong adaptability.

[0067] In this embodiment, the lift coefficient and the drag coefficient are determined by the following method:

[0068] C l = cosα(C dmax sinα+A2cotα);

[0069] Cd =C dmax -cosα(C dmax cosα-B2);

[0070] Where: α represents the angle of attack, C l is the lift coefficient, C d represents the drag coefficient, C dmax is the maximum drag coefficient under the current fan blade airfoil; A2 and B2 are both coefficients;

[0071]

[0072] Where: α s is the stall angle of attack under the current blade airfoil, C ls is the stall angle of attack α s The lift coefficient under ds is the stall angle of attack α s The drag coefficient under

[0073] AR is the aspect ratio of the current grid, C ice is the average ice thickness in the chord length direction of the current grid, d i is the ice thickness of the i-th grid in the chord direction, n is the number of grids, and c is the chord length of the current wind turbine blade airfoil.

[0074] In this embodiment, the ice thickness d is determined by the following method: i :

[0075]

[0076] Where: Δt is the ice cover time step, ρ ice represents the ice density, m ice is the ice mass and A is the grid length.

[0077] In this embodiment, the ice density ρ ice Determined by the following formula:

[0078]

[0079] Where: V ∞ It represents the combined velocity of the incoming flow of the wind turbine; MVD is the median diameter of the water droplet;

[0080] ΔT s-f =T s -T f , T s is the fan blade surface temperature, T f The freezing temperature of water droplets.

[0081] In this embodiment, the ice mass m is determined by the following method: ice :

[0082] Construct the mass balance equation within the grid:

[0083]

[0084] Where: m im is the mass of the supercooled water droplets impacting the grid, m in and m out are the water mass flowing into the grid and the water mass flowing out to the next grid, m eva is the mass of water evaporated;

[0085] m im =β·LWC·V ∞ ·A (2);

[0086] m out =(1-f)·∑m Add -m eva (3);

[0087]

[0088] Where: f is the freezing ratio of water droplets in the grid; L ew is the Lewis number, P sat-Ts and P sat-T are the blade mesh surface temperature T s The saturated water vapor pressure corresponding to the ambient temperature T;

[0089] Construct the energy balance equation within the grid:

[0090] ∑Q grid-in =Q im +Q in (5);

[0091] ∑Q Loss =Q eva +Q i +Q out +Q f +Q c (6);

[0092] ∑Q grid-in =∑Q Loss (7);

[0093] Qim is the energy brought by the supercooled water droplet hitting the grid, expressed as:

[0094]

[0095] Q inThe energy brought by the water flowing into the grid is expressed as:

[0096] Q in =m in C w (T s(i-1) -T f ) (9);

[0097] Q eva The energy taken away by water evaporation is expressed as:

[0098] Q eva =m eva [C w ΔT s-f +L e ] (10);

[0099] Q out The energy taken away by the water flowing out of the grid is expressed as:

[0100] Q out =m out C w ΔT s-f (11);

[0101] Q f is the heat loss due to friction, expressed as:

[0102]

[0103] Q c is the heat removed by natural convection, expressed as:

[0104] Q c =-h c AΔT s (13);

[0105] T f is the freezing temperature of water droplets, T s is the blade surface temperature, T is the external ambient temperature, △T s-f =T s -T f ,△T s =TT s ,C a , C w , C i are the specific heats of air, water and ice respectively; L f , L e are the latent heat of melting and the latent heat of evaporation respectively; h c is the convective heat transfer coefficient. r is the recovery coefficient of dynamic heating, expressed as:

[0106] Pr is the Prandtl number. When the grid boundary layer is in the laminar region, n0=1 / 2; when it is in the turbulent region, n0=1 / 3;

[0107] Combine formula (1) and formula (13) to solve for the ice mass m ice .

[0108] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution 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 solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A method for determining a key protection area of ​​a fan blade, characterized in that: The following steps are involved: S1. Obtain a blade model of a wind turbine in actual working conditions, import the model into Ansys Fluent software, and divide the blade model into several grids in Ansys Fluent software; S2. Obtain environmental parameters of the environment in which the wind turbine is located in actual working conditions, including ambient temperature, wind speed, humidity and rainfall, and import the environmental parameters into Ansys Fluent software to simulate the operation of the wind turbine; S3. Determine the ice thickness of each grid of the blade of the wind turbine during the simulated operation; S4. Determine the chord length direction of the wind turbine blade, and determine the average ice thickness of multiple regions of the blade along the chord length direction; S5. Determine the lift coefficient and drag coefficient of each area of ​​the wind turbine blade based on the average ice thickness; S6. Find the area corresponding to the maximum lift coefficient and the minimum drag coefficient as the key protection area.

2. The method for determining the key protection area of ​​a wind turbine blade according to claim 1, characterized in that: The lift coefficient and drag coefficient are determined as follows: C l =cosα(C dmax sinα+A2cotα); C d =C dmax -cosα(C dmax cosα-B2); Where: α represents the angle of attack, C l is the lift coefficient, C d represents the drag coefficient, C dmax is the maximum drag coefficient under the current fan blade airfoil; A2 and B2 are coefficients; Where: α s is the stall angle of attack under the current blade airfoil, C ls is the stall angle of attack α s The lift coefficient under ds is the stall angle of attack α s The drag coefficient under AR is the aspect ratio of the current grid, C ice is the average ice thickness in the chord length direction of the current grid, d i is the ice thickness of the i-th grid in the chord direction, n is the number of grids, and c is the chord length of the current wind turbine blade airfoil.

3. The method for determining the key protection area of ​​a wind turbine blade according to claim 2, characterized in that: The ice thickness d is determined by the following method i : Where: Δt is the ice cover time step, ρ ice represents the ice density, m ice is the ice mass, and A is the grid length.

4. The method for determining the key protection area of ​​a wind turbine blade according to claim 3, characterized in that: The ice density ρ ice Determined by the following formula: Where: V ∞ It represents the combined velocity of the incoming flow of the wind turbine; MVD is the median diameter of the water droplet; ΔT s-f =T s -T f , T s is the fan blade surface temperature, T f The freezing temperature of water droplets.

5. The method for determining the key protection area of ​​a wind turbine blade according to claim 3, characterized in that: The ice mass m is determined by the following method ice : Construct the mass balance equation within the grid: Where: m im is the mass of the supercooled water droplets impacting the grid, m in and m out are the water mass flowing into the grid and the water mass flowing out to the next grid, m eva is the mass of water evaporated; m im =β·LUCK·V ∞ ·A(2); m out =(1-f)·∑m Add -m eva (3); Where: f is the freezing ratio of water droplets in the grid; L ew is the Lewis number, P sat-Ts and P sat-T are the blade mesh surface temperature T s The saturated water vapor pressure corresponding to the ambient temperature T; Construct the energy balance equation within the grid: ∑Q grid-in =Q im +Q in (5); ∑Q Loss =Q eva +Q i +Q out +Q f +Q c (6); ∑Q grid-in =∑Q Loss (7); Qim is the energy brought by the supercooled water droplet hitting the grid, expressed as: Q in The energy brought by the water flowing into the grid is expressed as: Q in =m in C w (T s(i-1) -T f )(9); Q eva The energy taken away by water evaporation is expressed as: Q eva =m eva [C w ΔT s-f +L e ](10); Q out The energy taken away by the water flowing out of the grid is expressed as: Q out =m out C w ΔT s-f (11); Q f is the heat loss due to friction, expressed as: Q c is the heat removed by natural convection, expressed as: Q c =-h c AΔT s (13); T f is the freezing temperature of water droplets, T s is the blade surface temperature, T is the external ambient temperature, △T s-f =T s -T f ,△T s =TT s ,C a , C w , C i are the specific heats of air, water and ice respectively; L f , L e are the latent heat of melting and the latent heat of evaporation respectively; h c is the convective heat transfer coefficient. r is the recovery coefficient of dynamic heating, expressed as: Pr is the Prandtl number. When the grid boundary layer is in the laminar region, n0 = 1 / 2; When in the turbulent zone, n0 = 1 / 3; Combine formula (1) and formula (13) to solve for the ice mass m ice .

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