Blade reconstruction method for scaled model of floating vertical axis wind turbine

Abstract

The application relates to a blade reconstruction method of a floating vertical axis fan model for a scale-down test, the aerodynamic parameters of a full-scale fan including an actual thrust coefficient and an actual side force coefficient, and the blade reconstruction method comprising the steps of: determining a scale-down ratio of the fan model according to test conditions; calculating initial blade chord length c0 and torsion angle beta0 of the fan model according to the Froude similarity law; calculating a Reynolds number of the fan model blade, and selecting a low Reynolds number airfoil; determining a thrust coefficient calculation expression C T (c, beta) of the fan model and a side force coefficient calculation expression C S (c, beta) of the fan model; at (c0, beta0), Taylor expansion formulae are used to expand C T (c, beta) and C S (c, beta) to obtain a binary first-order equation group by taking the actual thrust coefficient and the actual side force coefficient as target values and inputting the expanded expressions; and target chord length and target torsion angle of the fan model blade are solved to realize effective blade reconstruction and accurately simulate double-degree-of-freedom aerodynamic loads suffered by the fan.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of wind power generation, and in particular to a blade reconstruction method for a scaled-down test of a floating vertical axis wind turbine model. BACKGROUND

[0002] Offshore wind resources in many countries are located in waters with a water depth of more than 50 m. The use of fixed wind turbines in such water depths is too costly, and floating wind power generation technology is attracting more and more attention. According to the direction of the rotating shaft of the wind turbine, floating wind turbines are mainly divided into two categories: horizontal axis floating wind turbines and vertical axis floating wind turbines. Compared with the horizontal axis form, the vertical axis wind turbine has broad prospects in terms of large-scale, scale, and economy. In recent years, the vertical axis wind turbine has become a research hotspot in the academic and engineering fields. In recent years, with the rapid development of the wind power industry, many new concepts and forms of vertical axis wind turbines have been designed. Before the floating vertical axis wind turbine is put into production and use, it is of great significance to understand the aerodynamic load, power generation, and motion state of the wind turbine to ensure the safety and economy of the floating vertical axis wind turbine in the future.

[0003] Wind turbine model test (including pool test and wind tunnel test) is considered the most accurate, reliable, and economically feasible method for studying the dynamics of floating wind turbines and verifying numerical calculation tools. Among them, the pool model test pays more attention to the hydrodynamics of the floating platform and the mooring system, and the Froude similarity law should be given priority. However, under the Froude similarity law, the Reynolds number will decrease by several orders of magnitude, which will cause the aerodynamic load of the model wind turbine to decrease significantly compared with the theoretical value, which is called the scale effect. For wind tunnel tests, the aerodynamic performance of the wind turbine is highly related to air viscosity. The model wind turbine model needs to use the Reynolds number similarity criterion in theory. However, due to the limitations of the size of the wind tunnel, the geometric size of the model wind turbine is often reduced by 1-2 orders of magnitude compared with the actual size. Due to the influence of the wind speed range of the wind tunnel, the model wind speed is often only in the same order of magnitude as the actual size, and cannot be enlarged by 1-2 orders of magnitude. In this case, the Reynolds number in the wind tunnel scaled-down model test will decrease by several orders of magnitude, which will cause the aerodynamic load coefficient and power generation coefficient of the model size wind turbine to decrease significantly compared with the actual size, which is also called the scale effect.

[0004] The wind turbine aerodynamic load is an important excitation force that affects the motion of the floating wind turbine. Inaccurate aerodynamic load will lead to inaccurate evaluation of the motion performance and power generation of the floating wind turbine. Under the influence of the scale effect of the wind turbine model test, how to reconstruct the blade model in the pool test or wind tunnel test to simulate accurate wind turbine aerodynamic load will become one of the key problems.

[0005] Unlike horizontal axis wind turbine, the aerodynamic load of vertical axis wind turbine will change dramatically during a rotation, and the vertical axis wind turbine will not only suffer a large aerodynamic thrust, but also suffer a large lateral force. Therefore, the simulation of the aerodynamic load of the vertical axis wind turbine blade model is very complex, and there is no effective blade reconstruction method for the accurate simulation of the two-degree-of-freedom aerodynamic load of the vertical axis wind turbine, which affects the development of the vertical axis wind turbine technology. SUMMARY

[0006] The applicant provides a blade reconstruction method for a floating vertical axis wind turbine model for scale test, so as to realize effective blade reconstruction of the vertical axis wind turbine, accurately simulate the two-degree-of-freedom aerodynamic load suffered by the wind turbine, ensure the accuracy of the vertical axis wind turbine test, and help the development of the vertical axis wind turbine technology.

[0007] The technical scheme adopted by the application is as follows:

[0008] A blade reconstruction method for a floating vertical axis wind turbine model for scale test, the aerodynamic parameters of the full-scale wind turbine include actual thrust coefficient C Tp And actual lateral force coefficient C Sp .

[0009] The blade reconstruction method comprises the following steps:

[0010] S1: determining the scale ratio λ of the wind turbine model according to the test conditions;

[0011] S2: calculating the initial blade chord length c0 and the initial blade torsion angle β0 of the wind turbine model according to the Froude similarity law;

[0012] S3: calculating the Reynolds number Re m of the wind turbine model blade according to the Froude similarity law, and selecting a low Reynolds number airfoil according to the Reynolds number Re m of the wind turbine model blade;

[0013] S4: determining the thrust coefficient calculation expression C T (c, β) of the wind turbine model and the lateral force coefficient calculation expression C S (c, β) of the wind turbine model based on the low Reynolds number airfoil;

[0014] S5: at (c0, β0), the Taylor expansion formula is used to expand C T (c, β) and C S (c, β) to obtain:

[0015]

[0016] The actual thrust coefficient C Tpand the actual side force coefficient C Sp As the target value, the above formula is brought in to obtain a binary linear equation group:

[0017]

[0018] In the binary linear equation group, c is the target chord length of the fan model blade, and β is the target torsion angle of the fan model blade, both of which are unknown numbers;

[0019] S6: solving the binary linear equation group to obtain the target chord length c of the fan model blade and the target torsion angle β of the fan model blade, and completing the blade reconstruction.

[0020] λ = L m / L p

[0021] Wherein, L m is the linear scale parameter of the fan model, and L p is the linear scale parameter of the real scale fan.

[0022] c0 = c p × λ,

[0023] β0 = β p ,

[0024] Wherein, c p is the chord length of the real scale blade, and β p is the torsion angle of the real scale blade.

[0025] The Reynolds number Re m of the fan model blade is Re p · λ 1.5 , wherein Re p is the Reynolds number of the real scale fan blade.

[0026] On the basis of the thrust coefficient calculation expression C T (c, β) and the side force coefficient calculation expression C S (c, β), the value of β is set as β0,

[0027] The thrust coefficient C T about the first relationship curve of c, the slope of c = c0 on the first relationship curve is

[0028] The side force coefficient C S about the second relationship curve of c, the slope of c = c0 on the second relationship curve is

[0029] The thrust coefficient calculation expression C T(c, β) and the lateral force coefficient calculation expression C S (c, β) and the lateral force coefficient calculation expression C

[0030] The thrust coefficient C T The third relationship curve about β, the slope of the third relationship curve at β = β0 is

[0031] The lateral force coefficient C S The fourth relationship curve about β, the slope of the fourth relationship curve at β = β0 is

[0032] The low Reynolds number airfoil is an AG455 airfoil.

[0033] The method for determining the thrust coefficient and the lateral force coefficient calculation expression of the fan model is:

[0034]

[0035]

[0036] In the above formula (1) (2), θ is the circumferential angle of impeller rotation, Q n (θ) is the dimensionless normal force acting on the impeller actuating column of the fan model, Q t (θ) is the dimensionless tangential force acting on the impeller actuating column of the fan model, Q n (θ), Q t The expressions of (θ) and (θ) are as follows formula (3) (4);

[0037]

[0038] In formula (3) (4),

[0039] B is the number of blades of the fan model and the number of blades of the full-scale fan,

[0040] R is the radius of the impeller of the fan model, which is calculated according to the Froude similarity law,

[0041] V is the inflow wind speed, which is calculated according to the Froude similarity law,

[0042] β is the target twist angle of the fan model blade;

[0043] F nB is the normal force acting on the impeller cylindrical surface, F tB is the tangential force acting on the impeller cylindrical surface, F n is the force perpendicular to the chord length acting on the local element of the blade, F tfor a force parallel to the chord length on a local element of the blade,

[0044] wherein,

[0045] F n = L cos (theta) + D sin (theta) (5)

[0046] F t = L sin (theta) - D cos (theta) (6)

[0047]

[0048] In the above equations (5) to (8), L is the lift force acting on a unit blade length, D is the drag force acting on a unit blade length,

[0049] rho is the air density,

[0050] c is the target chord length of the fan model blade,

[0051] C L is the lift coefficient, which is a known parameter for a low Reynolds number airfoil,

[0052] C D is the drag coefficient, which is a known parameter for a low Reynolds number airfoil,

[0053] alpha is the angle of attack and can represent a variable associated only with beta,

[0054] Re represents the Reynolds number, which takes a value of Re m .

[0055] The actual thrust coefficient C Tp and the actual side force coefficient C Sp are calculated by numerical calculation software.

[0056] The numerical calculation software is QBlade.

[0057] The beneficial effects of the present application are as follows:

[0058] The present application has the advantages of compact and reasonable structure, convenient operation, reselecting a low Reynolds number airfoil after scaling down the fan according to the Froude similarity law, forming a binary first-order equation about the chord length and the twist angle with the actual thrust coefficient and the side force coefficient as the target values based on the thrust coefficient calculation expression and the side force coefficient calculation expression of the fan model, comprehensively considering the key factors affecting the blade aerodynamic load, one-time solving the reconstruction parameters of the fan model, realizing the effective blade reconstruction of the vertical axis fan, accurately simulating the aerodynamic load received by the fan, ensuring the accuracy of the vertical axis fan test, and assisting the development of vertical axis fan technology.

[0059] Meanwhile, the application also has the following advantages:

[0060] The blade reconstruction method can be used for pool model test and wind tunnel test, has strong universality, and simultaneously considers the reconstruction of blade airfoils, blade chord lengths and blade twist angles, optimizes the model scale blades with optimal performance, and is simple to execute, so that relevant researchers can conveniently and efficiently perform blade reconstruction of the floating vertical axis wind turbine model. BRIEF DESCRIPTION OF DRAWINGS

[0061] Figure 1 A flowchart of the blade reconstruction method for the floating vertical axis wind turbine model for scale-down test of the application.

[0062] Figure 2 The normal force and tangential force borne by the actuating column model of the vertical axis wind turbine and the force analysis of the vertical axis wind turbine blade unit.

[0063] Figure 3 In an embodiment of the application, the average thrust coefficient of the reconstructed blade and the full-scale blade at different tip speed ratios (TSR) is compared.

[0064] Figure 4 In an embodiment of the application, the thrust coefficient of the reconstructed blade at all azimuth angles under the rated operating condition is compared with the thrust coefficient of the actual blade at high Reynolds number.

[0065] Figure 5 In an embodiment of the application, the lateral force coefficient of the reconstructed blade at all azimuth angles under the rated operating condition is compared with the lateral force coefficient of the actual blade at high Reynolds number. DETAILED DESCRIPTION

[0066] The specific embodiments of the application will be described below with reference to the accompanying drawings.

[0067] Embodiment One:

[0068] In the blade reconstruction method for the floating vertical axis wind turbine model for scale-down test of the embodiment, the aerodynamic parameters of the full-scale wind turbine include actual thrust coefficient C Tp and actual lateral force coefficient C Sp .

[0069] As shown in the figure, the blade reconstruction method includes the following steps: Figure 1

[0070] S1: determining the scale-down ratio λ of the wind turbine model according to the test conditions;

[0071] S2: calculating the initial blade chord length c0 and the initial blade twist angle β0 of the wind turbine model according to the Froude similarity law;

[0072] ​S3: The Reynolds number Re of the fan model blade is calculated according to the Froude similarity law m , the Reynolds number Re of the fan model blade is calculated according to the Froude similarity law m , and a low Reynolds number airfoil is selected;

[0073] S4: Based on the low Reynolds number airfoil, the thrust coefficient calculation expression of the fan model is determined as C T (c, β), and the lateral force coefficient calculation expression of the fan model is determined as C S (c, β),

[0074] The initial thrust coefficient C T (c0, β0) and the initial lateral force coefficient C S (c0, β0) of the fan model under the initial blade chord length c0 and the initial blade twist angle β0 are calculated according to the thrust coefficient and lateral force coefficient calculation expressions;

[0075] S5: At (c0, β0), the Taylor expansion formula is used to expand C T (c, β) and C S (c, β) to obtain:

[0076]

[0077] The actual thrust coefficient C Tp and the actual lateral force coefficient C Sp are taken as target values, and the above formula is obtained:

[0078]

[0079] In the binary linear equation set, c is the target chord length of the fan model blade, β is the target twist angle of the fan model blade, and c and β are both unknowns;

[0080] For a full-scale fan, the thrust coefficient and the lateral force coefficient of the fan are constant values that can be calculated after the structure, size, and wind power parameters are determined.

[0081] Specifically, the aerodynamic parameters of the full-scale fan, the actual thrust coefficient C Tp and the actual lateral force coefficient C Sp are calculated by numerical calculation software. The numerical calculation software is QBlade.

[0082] When the blade shape, airfoil lift and drag coefficients, air density, and inflow wind speed are known, the actual thrust coefficient C Tp and the actual lateral force coefficient C Sp of the full-scale fan blade under the actual Reynolds number can be calculated.

[0083] Of course, the actual thrust coefficient CTp and actual side force coefficient C Sp It can also be obtained by artificial calculation method.

[0084] Unlike horizontal axis wind turbine, the aerodynamic load of vertical axis wind turbine will change dramatically during a rotation, the aerodynamic parameters of full-scale wind turbine include actual thrust coefficient and actual side force coefficient, and both of them are affected by blade structure size and wind parameters, so it is very complex to make the related parameters of wind turbine model meet the test conditions while considering the simulation of two-degree-of-freedom aerodynamic load.

[0085] The blade reconstruction method for the floating vertical axis wind turbine model used in the scale test in the embodiment of the application, according to the Froude similarity law, the wind turbine is scaled, a low Reynolds number airfoil is reselected, based on the thrust coefficient calculation expression and the side force coefficient calculation expression of the wind turbine model, the key factors affecting the blade aerodynamic load are comprehensively considered, the actual thrust coefficient and the side force coefficient are taken as the target values to form a binary first-order equation about chord length and torsion angle, the reconstruction parameters of the wind turbine model are solved at one time, the required aerodynamic load of the wind turbine model is effectively matched without violating other similarity criteria, so that the effective blade reconstruction of the vertical axis wind turbine is realized, the aerodynamic load received by the wind turbine is accurately simulated, the accuracy of the vertical axis wind turbine test is ensured, and the development of the vertical axis wind turbine technology is promoted.

[0086] The blade reconstruction method described above simultaneously performs matching calculation of the aerodynamic parameters of the full-scale wind turbine from the two-degree-of-freedom directions of thrust and side force of the vertical axis wind turbine, and the result is accurate and efficient.

[0087] Embodiment two:

[0088] In the blade reconstruction method for the floating vertical axis wind turbine model used in the scale test in the embodiment of the application, the wind turbine is a vertical axis wind turbine, the aerodynamic parameters of the full-scale wind turbine include actual thrust coefficient C Tp and actual side force coefficient C Sp .

[0089] The blade reconstruction method includes the following steps:

[0090] S1: determining the scale ratio λ of the wind turbine model according to the test conditions;

[0091] λ = L m / L p

[0092] Wherein, L m is the linear dimension parameter of the wind turbine model, and L p is the linear dimension parameter of the full-scale wind turbine.

[0093] In the embodiment, the subscript m represents the model scale, and the subscript p represents the actual scale.

[0094] The line dimension parameters in step S1 include length, draft, barycentric position of the center of buoyancy, water depth, wave height, etc., which all need to meet the scale ratio. The determination of the scale ratio λ is related to the full scale of the fan, the laboratory conditions, etc., and needs to consider all factors to determine the most reasonable scale ratio.

[0095] S2: The initial blade chord length c0 and the initial blade torsion angle β0 of the fan model are calculated according to the Froude similarity law;

[0096] c0=c p ×λ,

[0097] β0=β p ,

[0098] wherein c p is the chord length of the full scale blade, and β p is the torsion angle of the full scale blade.

[0099] S3: The Reynolds number Re m of the fan model blade is calculated according to the Froude similarity law, and a low Reynolds number airfoil is selected according to the Reynolds number Re m of the fan model blade.

[0100] In step S3, the Reynolds number Re m of the fan model blade is Re p · λ 1.5 , wherein Re p is the Reynolds number of the full scale fan blade.

[0101] When designing the fan model, it is necessary to replace the blade airfoil to effectively match the required impeller thrust, so that the selected airfoil has superior aerodynamic performance at low Reynolds number. In addition, the selected airfoil should be relatively thin, which is beneficial to the weight control of blade manufacturing.

[0102] The low Reynolds number airfoil is an AG455 airfoil.

[0103] According to the geometric shapes of the AG455 and NACA0018 airfoils, it can be known that the ratio of the thickness to the chord length of the AG455 airfoil is smaller; according to the comparison of the aerodynamic lift coefficients of the AG455 airfoil and the NACA0018 airfoil at low Reynolds number, it can be known that the lift coefficient of the AG455 airfoil at low Reynolds number is much higher than that of the NACA0018 airfoil. Therefore, the AG455 airfoil is very suitable as the airfoil of the fan model blade.

[0104] S4: On the basis of the above low Reynolds number airfoil, the thrust coefficient calculation expression C T (c, β) of the fan model is determined, and the lateral force coefficient calculation expression C S(c, β).

[0105] In step S4, the method for determining the thrust coefficient and the lateral force coefficient calculation expression of the fan model is as follows, which can be referred to Figure 2 (a):

[0106]

[0107] In the above formula (1) (2), θ is the circumferential angle of the impeller rotation, Q n (θ) is the dimensionless normal force acting on the impeller actuator column of the fan model, Q t (θ) is the dimensionless tangential force acting on the impeller actuator column of the fan model, Q n (θ), Q t (θ) are expressed as the following formula (3) (4);

[0108]

[0109] In formula (3) (4),

[0110] B is the number of blades of the fan model and the number of blades of the full-scale fan,

[0111] R is the radius of the impeller of the fan model, which is calculated according to the Froude similarity law,

[0112] V is the inflow wind speed, which is calculated according to the Froude similarity law,

[0113] β is the target twist angle of the fan model blade;

[0114] F nB is the normal force acting on the impeller cylindrical surface, F tB is the tangential force acting on the impeller cylindrical surface, F n is the force acting on the local element of the blade perpendicular to the chord length, F t is the force acting on the local element of the blade parallel to the chord length, which can be referred to Figure 2 (b),

[0115] wherein,

[0116] F n = L cos(θ) + D sin(θ) (5)

[0117] F t = L sin(θ) - D cos(θ) (6)

[0118]

[0119] In the above equations (5) to (8), L is the lift acting on a unit blade length, and D is the drag acting on a unit blade length,

[0120] p is the air density,

[0121] c is the target chord length of the fan model blade,

[0122] C L is the lift coefficient, and is a known parameter of a low Reynolds number airfoil,

[0123] C D is the drag coefficient, and is a known parameter of a low Reynolds number airfoil,

[0124] a is the angle of attack and can represent a variable associated with β only,

[0125] Re represents the Reynolds number, and is given by Re m .

[0126] The expressions for calculating the thrust coefficient and the side force coefficient of the fan model are obtained based on the above equations (1) to (8).

[0127] Based on the low Reynolds number airfoil, the scaled calculation is obtained based on the fan structure parameters and the wind power parameters, and the chord length and the twist angle are taken as variables to form the expressions for calculating the thrust coefficient and the side force coefficient of the fan model.

[0128] According to equation (7), the method for generating greater aerodynamic lift of the model scale blade can include:

[0129] 1) increasing the density p by replacing air with another medium having a greater density. However, this method is too low in implementability in wind tunnel tests and pool tests.

[0130] 2) increasing the wind speed V by using a wind speed greater than the Froude scale wind speed. However, the increase in the wind speed makes it impossible to satisfy the tip speed ratio similarity criterion, and in addition, the increased wind speed acting on the tower and the platform also significantly increases the wind load on the floating wind turbine system, resulting in a great error.

[0131] 3) increasing the Reynolds number Re by performing tests in a high-pressure environment of a special wind tunnel. However, the test site is mostly a normal wind tunnel laboratory or a wave tank laboratory, and it is difficult to achieve a high Reynolds number.

[0132] 4) increasing the lift coefficient C L by replacing the original blade airfoil with another airfoil suitable for a low Reynolds number condition, which essentially changes the dependence of the lift and drag coefficients on the angle of attack.

[0133] 5) Increase the chord length c, the aerodynamic load increases linearly with the chord length. However, this significantly increased chord length will significantly increase the mass of the rotor, which will make the center of gravity of the floating wind turbine model too high to meet the Froude similarity criterion.

[0134] 6) Change the blade twist angle β, and thus the angle of attack α, so that the blade operates at a larger lift coefficient. This way can improve the impeller thrust to some extent, but it is impossible to achieve the desired value by redesigning the blade twist angle alone.

[0135] From the above analysis, there is no single method that can significantly improve the blade lift, and airfoil, chord length and twist angle are key factors.

[0136] S5: At (c0, β0), the Taylor expansion formula is used to expand C T (c, β) and C S (c, β) is obtained:

[0137]

[0138] Bring c0 and β0 into the thrust coefficient and side force coefficient calculation expression to get C T (c0, β0) and C S (c0, β0), respectively, are the initial thrust coefficient and the initial side force coefficient of the wind turbine model under the initial blade chord length c0 and the initial blade twist angle β0 conditions;

[0139] Take the actual thrust coefficient C Tp and the actual side force coefficient C Sp as the target value, and bring them into the above formula to get a binary linear equation group:

[0140]

[0141] In the binary linear equation group, c is the target chord length of the wind turbine model blade, β is the target twist angle of the wind turbine model blade, and c and β are both unknown numbers.

[0142] The coefficient solving method of the Taylor expansion term in the above equation group is as follows:

[0143] Based on the thrust coefficient calculation expression C T (c, β) and the side force coefficient calculation expression C S (c, β), set the value of β as β0,

[0144] The least squares method is used to fit the thrust coefficient C T The first relationship curve about c, the slope of the first relationship curve at c=c0 is

[0145] The least squares method is used to fit the side force coefficient CS For the second relationship curve of c, the slope at c=c0 on the second relationship curve is

[0146] In the thrust coefficient calculation expression C T (c, β) and the lateral force coefficient calculation expression C S (c, β), the value of c is set as c0,

[0147] The thrust coefficient C T For the third relationship curve of β, the slope at β=β0 on the third relationship curve is

[0148] The lateral force coefficient C S For the fourth relationship curve of β, the slope at β=β0 on the fourth relationship curve is

[0149] S6: solving the binary linear equation set to obtain the target chord length c of the fan model blade and the target torsion angle β of the fan model blade, and completing the blade reconstruction.

[0150] Next, taking the blade reconstruction of a vertical axis fan model with a specific structure size as an example, the accuracy of the blade reconstruction method of the application is illustrated, wherein the scale ratio is 1 / 60, and the fan model parameters after scaling and the full-scale fan parameters are compared in Table 1.

[0151] Table 1 Comparison of relevant structures and working conditions of full-scale fan and fan model

[0152] Parameter name Full scale fan Fan model Number of blades 3 3 Impeller radius 39.0[m] 0.65[m] Blade length 80.0[m] 1.33[m] Blade airfoil NACA0018 AG455 Blade chord length 2.7[m] 0.0675[m] Blade twist angle 0[°] 2.5[°] Wind speed range 5.0-25.0 [m / s] 0.65-3.23 [m / s] Impeller rotational speed 0.50-0.88 [rad / s] 36.98-65.09 [rad / s] Tip speed ratio (TSR) range 1.37-3.97 1.37-3.97

[0153] The average thrust coefficient of the reconstructed blade of the embodiment at different tip speed ratios is as shown in Figure 3 The average thrust coefficient is well matched in the tip speed ratio (TSR) range (1.37-3.97) covered during the operation of the fan, and since the average lateral force coefficient is 0, it is not compared. The tip speed ratio (TSR) range 1.37-3.97 can meet the test conditions of conventional working conditions, therefore, the fan model obtained by the blade reconstruction method of the embodiment can accurately simulate the aerodynamic load received by the fan, ensure the accuracy of the vertical axis fan test, and improve the accuracy and implementability of the test.

[0154] The lateral force coefficient of the reconstructed blade is also well matched, Figure 4 , Figure 5 A specific working condition is given under the full azimuth angle, wherein, Figure 4 The thrust coefficient of the reconstructed blade under the full azimuth angle in the rated working condition is compared with the thrust coefficient of the actual blade at high Reynolds number, Figure 5The lateral force coefficients of the reconstructed blades at all azimuth angles in the rated operating condition are compared with the lateral force coefficients of the actual blades at high Reynolds number.

[0155] The blade reconstruction method of the embodiment can be used for pool model test and wind tunnel test, and has strong universality; the reconstruction method simultaneously considers the reconstruction of blade airfoils, blade chord lengths and blade twist angles, optimizes the model scale blades with optimal performance, and is simple to execute, so that researchers can conveniently and efficiently reconstruct the blades of the floating vertical axis wind turbine model.

[0156] The above description is an explanation of the present application, not a limitation of the present application, and the scope defined by the present application is referred to the claims, and any form of modification within the protection scope of the present application can be made.

Claims

1. A blade reconstruction method for a floating vertical axis wind turbine model used in scale-down tests, characterized in that: The aerodynamic parameters of a real-scale wind turbine include the actual thrust coefficient C. Tp And the actual lateral force coefficient C Sp ; The blade reconfiguration method includes the following steps: S1: Determine the scale λ of the wind turbine model based on the test conditions; S2: The initial blade chord length c0 and initial blade twist angle β0 of the wind turbine model are calculated according to the similarity law of Froude; S3: The Reynolds number Re of the wind turbine model blades is calculated based on Froude's similarity law. m Based on the Reynolds number Re of the wind turbine model blades m Choose a low Reynolds number airfoil; S4: Based on the aforementioned low Reynolds number airfoil, the thrust coefficient calculation expression for the wind turbine model is determined to be C. T (c, β), and the expression for calculating the lateral force coefficient of the wind turbine model is C. S (c, β); S5: At (c0, β0), apply the Taylor expansion formula to C. T (c, β) and C S Expanding (c, β) yields: With actual thrust coefficient C Tp And the actual lateral force coefficient C Sp Substituting the target value into the above equation yields a system of two linear equations in two variables: In the system of two linear equations, c is the target chord length of the wind turbine model blade, β is the target twist angle of the wind turbine model blade, and both c and β are unknowns. S6: Solve the system of two linear equations to obtain the target chord length c and the target twist angle β of the wind turbine model blade, thus completing the blade reconstruction.

2. The blade reconstruction method for a floating vertical axis wind turbine model used in scale-down tests as described in claim 1, characterized in that: λ=L m / L p Among them, L m L represents the line-scale parameter of the wind turbine model. p These are the linear dimension parameters of a real-scale fan.

3. The blade reconstruction method for a floating vertical axis wind turbine model used in scale-down tests as described in claim 1, characterized in that: c0=c p ×λ, β0＝β p ， Among them, c p For the chord length of the real-scale blade, β p This refers to the twist angle of the blade at actual dimensions.

4. The blade reconstruction method for a floating vertical axis wind turbine model used in scale-down tests as described in claim 1, characterized in that: Reynolds number Re of wind turbine model blades m =Re p ·λ 1.5 , among which, Re p This represents the Reynolds number of a real-scale wind turbine blade.

5. The blade reconstruction method for a floating vertical axis wind turbine model used in scale-down tests as described in claim 1, characterized in that: In the thrust coefficient calculation expression C T (c, β) and the formula for calculating the lateral force coefficient C S Based on (c, β), let the value of β be β0. The thrust coefficient C was obtained by fitting using the least squares method. T The first relationship curve with respect to c, the slope of the first relationship curve at c = c0 is... The lateral force coefficient C was obtained by fitting using the least squares method. S Regarding the second relationship curve for c, the slope of the second relationship curve at c = c0 is...

6. The blade reconstruction method for a floating vertical axis wind turbine model used in scale-down tests as described in claim 1, characterized in that: In the thrust coefficient calculation expression C T (c, β) and the formula for calculating the lateral force coefficient C S Based on (c, β), let the value of c be c0. The thrust coefficient C was obtained by fitting using the least squares method. T Regarding the third relationship curve for β, the slope of the third relationship curve at β = β0 is... The lateral force coefficient C was obtained by fitting using the least squares method. S The fourth relationship curve for β has a slope at β = β0 as follows:

7. The blade reconstruction method for a floating vertical axis wind turbine model used in scale-down tests as described in claim 1, characterized in that: The low Reynolds number airfoil is the AG455 airfoil.

8. The blade reconstruction method for a floating vertical axis wind turbine model used in scale-down tests as described in claim 1, characterized in that: The method for determining the calculation expressions for the thrust coefficient and lateral force coefficient of the wind turbine model is as follows: In equations (1) and (2) above, θ is the circumferential angle of the impeller rotation, and Q n (θ) represents the dimensionless normal force Q acting on the impeller actuation column of the wind turbine model. t (θ) represents the dimensionless tangential force Q acting on the impeller actuation column of the wind turbine model. n (θ), Q t The expression for (θ) is as follows (3)(4); In equations (3) and (4), B means that the number of blades in the wind turbine model is equal to the number of blades in the full-scale wind turbine. R is the impeller radius of the wind turbine model, calculated according to Froude's similarity law. V is the inflow wind speed, calculated using Froude's similarity law. β is the target twist angle of the wind turbine model blade; F nB F is the normal force acting on the cylindrical surface of the impeller. tB F is the tangential force acting on the cylindrical surface of the impeller. n F is the force perpendicular to the chord length acting on a local unit of the blade. t The force is parallel to the chord length and acts on a local unit of the blade. in, F n =L cos(θ)+D sin(θ) (5) F t =L sin(θ)-D cos(θ) (6) In equations (5) to (8) above, L is the lift force acting on a unit blade length, and D is the drag force acting on a unit blade length. ρ is the air density. c represents the target chord length of the wind turbine model blade. C L Let be the lift coefficient, and be a known parameter for low Reynolds number airfoils. C D is the drag coefficient, and is a known parameter for low Reynolds number airfoils. α is the angle of attack and can represent a variable that is only related to β. Re represents the Reynolds number, which takes the value Re. m .

9. The blade reconstruction method for a floating vertical axis wind turbine model used in scale-down tests as described in claim 1, characterized in that: The actual thrust coefficient C Tp And the actual lateral force coefficient C Sp Calculated using numerical calculation software.

10. The blade reconstruction method for a floating vertical axis wind turbine model used in scale-down tests as described in claim 9, characterized in that: The numerical calculation software is QBlade.

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