Blade reconstruction method of floating vertical axis fan model for scaling test

Abstract

The invention relates to a blade reconstruction method of a floating vertical axis fan model for a scaling test, aerodynamic parameters of a real-scale fan comprise an actual thrust coefficient and an actual lateral force coefficient, and the blade reconstruction method comprises the following steps: determining a scaling proportion of the fan model according to test conditions; the initial blade chord length c0 and the torsional angle beta0 of the fan model are obtained through calculation according to the Froude similarity law; calculating to obtain a Reynolds number of a fan model blade, and selecting a low Reynolds number airfoil; determining a thrust coefficient calculation expression CT (c, beta) and a lateral force coefficient calculation expression CS (c, beta) of the fan model; performing expansion processing on CT (c, beta) and CS (c, beta) at (c0, beta0) by adopting a Taylor expansion formula, taking an actual thrust coefficient and an actual lateral force coefficient as target values, and substituting the target values into an expression subjected to expansion processing to obtain a binary linear equation set; the target chord length and the target torsion angle of the fan model blade are solved, effective blade reconstruction is achieved, and the two-degree-of-freedom aerodynamic load borne by the fan is accurately simulated.

Description

Technical Field

[0001] The invention relates to the technical field of wind power generation, in particular to a blade reconstruction method of a floating vertical axis wind turbine model used for scaled-down tests. Background Art

[0002] The offshore wind resources of many countries are located in waters with a depth of more than 50m. The cost of using fixed wind turbines in such water depths is too high, and floating wind power generation technology is attracting more and more attention. According to the different directions of the wind turbine's rotating axis, 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, vertical axis wind turbines have broad prospects in terms of large-scale, large-scale, and economical. In recent years, vertical axis wind turbines have become a research hotspot in academia and engineering. In recent years, with the rapid development of the wind power industry, many new concepts and new forms of vertical axis wind turbines have been designed continuously. Before putting the floating vertical axis wind turbine into production and use, it is of great significance to understand the wind turbine's aerodynamic load, power generation, motion state, etc. to ensure the future safety and economy of the floating vertical axis wind turbine.

[0003] Wind turbine model tests (including water tank tests and wind tunnel tests) are considered to be the most accurate, reliable and economically feasible methods for studying the dynamics of floating wind turbines and verifying numerical calculation tools. Among them, water tank model tests pay more attention to the hydrodynamic problems of floating platforms and mooring systems, and Froude's similarity law should be given priority; however, under Froude's similarity law, the Reynolds number will drop by several orders of magnitude, which makes the aerodynamic load of the model wind turbine drop 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 correlated with air viscosity. In theory, the Reynolds number similarity criterion should be adopted for the scale reduction of the wind wheel model in the model test. However, due to the limitation of wind tunnel size, the model scale geometric dimensions of the wind turbine often need to be reduced by 1-2 orders of magnitude compared with the actual scale geometric dimensions; due to the wind tunnel wind speed range, the model wind speed can often only be at the same order of magnitude as the actual scale wind speed and cannot be enlarged by 1-2 orders of magnitude. In this case, the Reynolds number in the wind tunnel scale model test will drop by several orders of magnitude, which will cause the aerodynamic load coefficient and power generation coefficient of the model-scale wind turbine to drop significantly compared with the actual scale values. This is also called the scale effect.

[0004] The aerodynamic load of the wind turbine is an important excitation force that affects the movement of the floating wind turbine. Inaccurate aerodynamic load will inevitably lead to inaccurate evaluation of the floating wind turbine's motion performance and power generation. 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 the accurate aerodynamic load of the wind turbine will become one of the key issues.

[0005] Different from horizontal axis fans, the aerodynamic loads on vertical axis fans will change dramatically during one rotation, and vertical axis fans will be subjected to not only large aerodynamic thrust but also large lateral force. Therefore, the simulation of aerodynamic loads on the blade model of vertical axis fans is very complicated. At present, there is no effective blade reconstruction method for accurately simulating the two-degree-of-freedom aerodynamic loads of vertical axis fans, which affects the technical development of vertical axis fans. Summary of the invention

[0006] In response to the shortcomings in the above-mentioned existing production technologies, the applicant provides a blade reconstruction method for a floating vertical axis wind turbine model for scaled-down testing, thereby achieving effective blade reconstruction of the vertical axis wind turbine, accurately simulating the double-degree-of-freedom aerodynamic loads on the wind turbine, ensuring the accuracy of the vertical axis wind turbine test, and promoting the development of vertical axis wind turbine technology.

[0007] The technical solution adopted by the present invention is as follows:

[0008] A blade reconstruction method for a floating vertical axis wind turbine model for scaled-down testing. The aerodynamic parameters of the full-scale wind turbine include the actual thrust coefficient C Tp and the actual lateral force coefficient C Sp ;

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

[0010] S1: Determine the scale ratio λ of the fan model according to the test conditions;

[0011] S2: Calculate the initial blade chord length c0 and initial blade twist angle β0 of the fan model according to Froude's similarity law;

[0012] S3: The Reynolds number Re of the fan model blade is calculated according to Froude's similarity law m , according to the Reynolds number Re of the fan model blade m Choose a low Reynolds number airfoil;

[0013] 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 calculation expression of the lateral force coefficient of the wind turbine model is C S (c, β);

[0014] S5: At (c0, β0), use the Taylor expansion formula to calculate C T (c, β) and C S (c, β) is expanded to obtain:

[0015]

[0016] The actual thrust coefficient C Tpand the actual lateral force coefficient C Sp As the target value, we substitute the above formula to obtain a system of two-variable linear equations:

[0017]

[0018] In the two-variable linear equation system, c is the target chord length of the fan model blade, β is the target twist angle of the fan model blade, and both c and β are unknowns;

[0019] S6: Solve the two-variable linear equation group to obtain the target chord length c of the fan model blade and the target twist angle β of the fan model blade, and complete the blade reconstruction.

[0020] λ=L m / L p

[0021] Among them, L m is the linear scale parameter of the wind turbine model, L p is the line scale parameter of the real scale fan.

[0022] c0=c p ×λ,

[0023] β0=β p ,

[0024] Among them, c p is the chord length of the real-scale blade, β p is the twist angle of the real-scale blade.

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

[0026] In the thrust coefficient calculation expression C T (c, β) and the lateral force coefficient calculation expression C S (c, β), set the value of β to β0,

[0027] The thrust coefficient C is fitted using the least squares method. T The slope of the first relationship curve with respect to c at c=c0 is

[0028] The lateral force coefficient C is fitted using the least squares method. S The second relationship curve about c has a slope of c=c0 on the second relationship curve.

[0029] In the thrust coefficient calculation expression C T(c, β) and the lateral force coefficient calculation expression C S (c, β), set the value of c to c0,

[0030] The thrust coefficient C is fitted using the least squares method. T Regarding the third relationship curve of β, the slope at β=β0 on the third relationship curve is

[0031] The lateral force coefficient C is fitted using the least squares method. S Regarding the fourth relationship curve of 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 to determine the calculation expressions of thrust coefficient and side force coefficient of the fan model is:

[0034]

[0035]

[0036] In the above formulas (1) and (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 The expression of (θ) is as follows (3) (4);

[0037]

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

[0039] B is the number of blades in the fan model equal to the number of blades in the full-scale fan.

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

[0041] V is the inflow velocity, which is calculated according to Froude's 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 acting on the local element of the blade perpendicular to the chord length, F tis the force parallel to the chord length acting on the local element of the blade,

[0044] in,

[0045] F n =L cos(θ)+D sin(θ) (5)

[0046] F t =L sin(θ)-D cos(θ) (6)

[0047]

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

[0049] ρ is the air density,

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

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

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

[0053] α is the angle of attack and can represent a variable that is only associated with β,

[0054] Re represents the Reynolds number, which is Re m .

[0055] The actual thrust coefficient C Tp and the actual lateral force coefficient C Sp Calculated by numerical calculation software.

[0056] The numerical calculation software is QBlade.

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

[0058] The invention has a compact and reasonable structure and is easy to operate. After the fan is scaled down according to Froude's similarity law, a low Reynolds number airfoil is reselected. Based on the thrust coefficient calculation expression and the lateral force coefficient calculation expression of the fan model, the key factors affecting the aerodynamic load of the blade are comprehensively considered. A binary linear equation about the chord length and the torsion angle is formed with the actual thrust coefficient and the lateral force coefficient as the target values. The reconstruction parameters of the fan model are solved at one time, and the fan model is effectively matched with the required aerodynamic load without violating other similarity criteria, thereby realizing effective blade reconstruction of the vertical axis fan, accurately simulating the aerodynamic load on the fan, ensuring the accuracy of the vertical axis fan test, and promoting the development of the vertical axis fan technology.

[0059] At the same time, the present invention also has the following advantages:

[0060] The blade reconstruction method can be used for water tank model tests as well as wind tunnel tests, and has strong universality. The reconstruction method simultaneously considers the reconstruction of the blade airfoil, blade chord length, and blade twist angle to optimize the model-scale blade with the best performance. The reconstruction method is easy to execute, making it convenient for relevant researchers to refer to and efficiently reconstruct the blades of the floating vertical axis wind turbine model. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Figure 1 The present invention is a flow chart of a blade reconstruction method for a floating vertical axis wind turbine model used for scaled-down testing.

[0062] Figure 2 The normal and tangential forces acting on the actuating column model of the vertical axis fan, as well as the force analysis of the vertical axis fan blade unit.

[0063] Figure 3 Comparison of thrust coefficient means of a reconstructed blade and a full-scale blade at different tip speed ratios (TSR) in one embodiment of the present invention.

[0064] Figure 4 The thrust coefficient of the reconstructed blade at all angles under rated conditions in one embodiment of the present invention is compared with the thrust coefficient of the actual blade at high Reynolds number.

[0065] Figure 5 The side force coefficient of the reconstructed blade at all azimuth angles under rated working conditions in one embodiment of the present invention is compared with the side force coefficient of the actual blade at high Reynolds number. DETAILED DESCRIPTION

[0066] The specific implementation of the present invention will be described below in conjunction with the accompanying drawings.

[0067] Embodiment 1:

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

[0069] like Figure 1 As shown, the blade reconstruction method comprises the following steps:

[0070] S1: Determine the scale ratio λ of the fan model according to the test conditions;

[0071] S2: Calculate the initial blade chord length c0 and initial blade twist angle β0 of the fan model according to Froude's similarity law;

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

[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 calculation expression of the lateral force coefficient of the wind turbine model is C S (c, β),

[0074] According to the calculation expressions of thrust coefficient and lateral force coefficient, the initial thrust coefficient C of the fan model under the conditions of initial blade chord length c0 and initial blade torsion angle β0 is calculated. T (c0, β0) and initial lateral force coefficient C S (c0, β0);

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

[0076]

[0077] The actual thrust coefficient C Tp and the actual lateral force coefficient C Sp As the target value, we substitute the above formula to obtain a system of two-variable linear equations:

[0078]

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

[0080] For a full-scale wind turbine, once the structure, size and wind parameters are determined, the thrust coefficient and lateral force coefficient of the wind turbine are constants and can be calculated.

[0081] Specific, full-scale fan aerodynamic parameters - actual thrust coefficient C Tp and the actual lateral force coefficient C Sp The calculation was done using numerical calculation software QBlade.

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

[0083] Of course, the actual thrust coefficient CTp and the actual lateral force coefficient C Sp It can also be obtained through manual calculation.

[0084] Unlike horizontal-axis fans, vertical-axis fans are subject to dramatic changes in aerodynamic loads during one rotation. The aerodynamic parameters of a full-scale fan include the actual thrust coefficient and the actual side force coefficient, and both the actual thrust coefficient and the actual side force coefficient are affected by the blade structure size and wind parameters. Therefore, it is very complicated to simulate the aerodynamic loads of both degrees of freedom while making the relevant parameters of the fan model meet the test conditions.

[0085] The blade reconstruction method of the floating vertical axis wind turbine model used for scaled-down testing in the embodiment of the present application scales down the wind turbine according to Froude's similarity law, reselects a low Reynolds number airfoil, and comprehensively considers the key factors affecting the aerodynamic load of the blade based on the thrust coefficient calculation expression and the side force coefficient calculation expression of the wind turbine model. A binary linear equation about the chord length and the torsion angle is formed with the actual thrust coefficient and the side force coefficient as the target values, and the reconstruction parameters of the wind turbine model are solved at one time to achieve effective matching of the wind turbine model with the required aerodynamic load without violating other similarity criteria, thereby achieving effective blade reconstruction of the vertical axis wind turbine, accurately simulating the aerodynamic load on the wind turbine, ensuring the accuracy of the vertical axis wind turbine test, and promoting the development of vertical axis wind turbine technology.

[0086] The blade reconstruction method mentioned above simultaneously performs matching calculations of the aerodynamic parameters of the real-scale fan from the two degrees of freedom of thrust and lateral force of the vertical axis fan, and the results are accurate and efficient.

[0087] Embodiment 2:

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

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

[0090] S1: Determine the scale ratio λ of the fan model according to the test conditions;

[0091] λ=L m / L p

[0092] Among them, L m is the linear scale parameter of the wind turbine model, L p is the line scale parameter of the real scale fan.

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

[0094] The line scale parameters in step S1 include length, draft, center of gravity and buoyancy, water depth, wave height, etc. These parameters must meet the scale ratio. The determination of the scale ratio λ is related to factors such as the actual scale of the wind turbine and laboratory conditions. All factors must be considered comprehensively to determine the most reasonable scale ratio.

[0095] S2: Calculate the initial blade chord length c0 and initial blade twist angle β0 of the fan model according to Froude's similarity law;

[0096] c0=c p ×λ,

[0097] β0=β p ,

[0098] Among them, c p is the chord length of the real-scale blade, β p is the twist angle of the real-scale blade.

[0099] S3: The Reynolds number Re of the fan model blade is calculated according to Froude's similarity law m , according to the Reynolds number Re of the fan model blade m Choose a low Reynolds number airfoil;

[0100] In step S3, the Reynolds number Re of the fan model blade m =Re p ·λ 1.5 , where Re p is the Reynolds number of the real-scale fan blade.

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

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

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

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

[0105] In step S4, the method for determining the calculation expressions of the thrust coefficient and the lateral force coefficient of the wind turbine model is as follows. Figure 2 (a):

[0106]

[0107] In the above formulas (1) and (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 The expression of (θ) is as follows (3)(4);

[0108]

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

[0110] B is the number of blades in the fan model equal to the number of blades in the full-scale fan.

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

[0112] V is the inflow velocity, which is calculated according to Froude's 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 parallel to the chord length on the local element of the blade, which can be referred to Figure 2 (b)

[0115] in,

[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 the unit blade length, and D is the drag acting on the unit blade length.

[0120] ρ is the air density,

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

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

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

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

[0125] Re represents the Reynolds number, which is Re m .

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

[0127] Based on the low Reynolds number airfoil and the scaled-down calculation, the thrust coefficient and lateral force coefficient calculation expressions of the wind turbine model are formed by comprehensively considering various influencing factors and taking the chord length and twist angle as variables.

[0128] According to formula (7), the method of making the model-scale blade generate a larger aerodynamic lift may include:

[0129] 1) Increase the density ρ and replace the air with another medium with higher density. However, the feasibility of this method in wind tunnel tests and water tank tests is too low.

[0130] 2) Increase the wind speed V and use a wind speed greater than the Froude scale wind speed. However, the increase in wind speed will make the tip speed ratio similarity criterion unable to be met. In addition, the increased wind speed will act on the tower and platform, which will also significantly increase the wind load on the floating wind turbine system and produce a huge error.

[0131] 3) Increase the Reynolds number Re and conduct the test in a high-pressure environment of a dedicated wind tunnel. However, most test sites are normal wind tunnel laboratories or wave tank laboratories, and it is difficult to achieve a high Reynolds number.

[0132] 4) Increase lift coefficient C L , replacing the original blade airfoil with other airfoils suitable for low Reynolds number conditions. This method essentially changes the dependence of lift and drag coefficients on the angle of attack.

[0133] 5) Increase the chord length c, and the aerodynamic load increases linearly with the chord length. However, this significant increase in 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 and fail to meet the Froude similarity criterion.

[0134] 6) Changing the blade twist angle β, and then changing the angle of attack α, makes the blade operate at a larger lift coefficient. This method can improve the impeller thrust to a certain extent, but the desired value cannot be achieved by simply redesigning the blade twist angle.

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

[0136] S5: At (c0, β0), use the Taylor expansion formula to calculate C T (c, β) and C S (c, β) is expanded to obtain:

[0137]

[0138] Substituting c0 and β0 into the thrust coefficient and lateral force coefficient calculation expressions, we can get C T (c0, β0) and C S (c0, β0), the initial thrust coefficient and initial side force coefficient of the wind turbine model under the conditions of initial blade chord length c0 and initial blade twist angle β0, respectively;

[0139] The actual thrust coefficient C Tp and the actual lateral force coefficient C Sp As the target value, we substitute the above formula to obtain a system of two-variable linear equations:

[0140]

[0141] In the two-variable linear equation system, c is the target chord length of the fan model blade, β is the target twist angle of the fan model blade, and both c and β are unknown.

[0142] The method for solving the coefficients of the Taylor expansion terms in the above system of equations is as follows:

[0143] In the thrust coefficient calculation expression C T (c, β) and the lateral force coefficient calculation expression C S (c, β), set the value of β to β0,

[0144] The thrust coefficient C is fitted using the least squares method. T The slope of the first relationship curve with respect to c at c=c0 is

[0145] The lateral force coefficient C is fitted using the least squares method.S The second relationship curve about c has a slope of c=c0 on the second relationship curve.

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

[0147] The thrust coefficient C is fitted using the least squares method. T Regarding the third relationship curve of β, the slope at β=β0 on the third relationship curve is

[0148] The lateral force coefficient C is fitted using the least squares method. S Regarding the fourth relationship curve of β, the slope of the fourth relationship curve at β=β0 is

[0149] S6: Solve the two-variable linear equation group to obtain the target chord length c of the fan model blade and the target twist angle β of the fan model blade, and complete the blade reconstruction.

[0150] The following takes the blade reconstruction of a vertical axis fan model with a specific structural size as an example to illustrate the accuracy of the blade reconstruction method of the present application, wherein the scale ratio is 1 / 60, and the comparison between the scaled fan model parameters and the actual scale fan parameters is shown in Table 1.

[0151] Table 1 Comparison table of relevant structures and operating conditions of real-scale fans and fan models

[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 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 mean thrust coefficients of the reconstructed blades of this embodiment at different tip speed ratios are as follows: Figure 3 As shown in the figure, within the range of tip speed ratio (TSR) (1.37-3.97) covered during the operation of the fan, the mean values ​​of the thrust coefficients match well. Since the mean value of the side force coefficient is 0, no comparison is made. The tip speed ratio (TSR) range of 1.37-3.97 can meet the test of conventional working conditions. Therefore, the fan model obtained by the blade reconstruction method of this embodiment can accurately simulate the aerodynamic load on the fan, ensure the accuracy of the vertical axis fan test, and improve the accuracy and feasibility of the test.

[0154] The consistency of the lateral force coefficient of the reconstructed blade is also good. Figure 4 , Figure 5 A specific working condition under all-round angles is given, where Figure 4 The thrust coefficient of the reconstructed blade at all angles in rated conditions is compared with the thrust coefficient of the actual blade at high Reynolds number. Figure 5The side force coefficients of the reconstructed blades at all azimuth angles in rated conditions are compared with those of the actual blades at high Reynolds numbers.

[0155] The blade reconstruction method of this embodiment can be used for water tank model tests and wind tunnel tests, and has strong universality. The reconstruction method simultaneously considers the reconstruction of the blade airfoil, blade chord length, and blade twist angle, and optimizes the model-scale blade with the best performance. The reconstruction method is easy to execute, which is convenient for relevant researchers to refer to and conveniently and efficiently reconstruct the blades of the floating vertical axis wind turbine model.

[0156] The above description is an explanation of the present invention, not a limitation of the present invention. The scope of the present invention is defined in the claims. Any form of modification may be made within the scope of protection of the present invention.

Claims

1. A blade reconstruction method for a floating vertical axis wind turbine model for scaled-down testing, characterized in that: The aerodynamic parameters of the full-scale fan include the actual thrust coefficient C Tp and the actual lateral force coefficient C Sp ; The blade reconstruction method comprises the following steps: S1: Determine the scale ratio λ of the fan model according to the test conditions; S2: Calculate the initial blade chord length c0 and initial blade twist angle β0 of the fan model according to Froude's similarity law; S3: The Reynolds number Re of the fan model blade is calculated according to Froude's similarity law m , according to the Reynolds number Re of the fan model blade m Choose a low Reynolds number airfoil; 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 calculation expression of the lateral force coefficient of the wind turbine model is C S (c, β); S5: At (c0, β0), use the Taylor expansion formula to calculate C T (c, β) and C S (c, β) is expanded to obtain: The actual thrust coefficient C Tp and the actual lateral force coefficient C Sp As the target value, we substitute the above formula to obtain a system of two-variable linear equations: In the two-variable linear equation system, c is the target chord length of the fan model blade, β is the target twist angle of the fan model blade, and both c and β are unknowns; S6: Solve the two-variable linear equation group to obtain the target chord length c of the fan model blade and the target twist angle β of the fan model blade, and complete the blade reconstruction.

2. The blade reconstruction method of a floating vertical axis wind turbine model for scaled-down testing according to claim 1, characterized in that: λ=L m / L p Among them, L m is the linear scale parameter of the wind turbine model, L p is the line scale parameter of the real scale fan.

3. The blade reconstruction method of a floating vertical axis wind turbine model for scaled-down testing according to claim 1, characterized in that: c0=c p ×λ, β0＝β p ， Among them, c p is the chord length of the real-scale blade, β p is the twist angle of the real-scale blade.

4. The blade reconstruction method of a floating vertical axis wind turbine model for scaled-down testing according to claim 1, characterized in that: Reynolds number of the fan model blade m =Re p ·λ 1.5 , where Re p is the Reynolds number of the real-scale fan blade.

5. The blade reconstruction method of a floating vertical axis wind turbine model for scaled-down testing according to claim 1, characterized in that: In the thrust coefficient calculation expression C T (c, β) and the lateral force coefficient calculation expression C S (c, β), set the value of β to β0, The thrust coefficient C is fitted using the least squares method. T The slope of the first relationship curve with respect to c at c=c0 is The lateral force coefficient C is fitted using the least squares method. S The second relationship curve about c has a slope of c=c0 on the second relationship curve.

6. The blade reconstruction method of a floating vertical axis wind turbine model for scaled-down testing according to claim 1, characterized in that: In the thrust coefficient calculation expression C T (c, β) and the lateral force coefficient calculation expression C S (c, β), set the value of c to c0, The thrust coefficient C is fitted using the least squares method. T Regarding the third relationship curve of β, the slope at β=β0 on the third relationship curve is The lateral force coefficient C is fitted using the least squares method. S Regarding the fourth relationship curve of β, the slope of the fourth relationship curve at β=β0 is 7. The blade reconstruction method of a floating vertical axis wind turbine model for scaled-down testing according to claim 1, characterized in that: The low Reynolds number airfoil is an AG455 airfoil.

8. The blade reconstruction method of a floating vertical axis wind turbine model for scaled-down testing according to claim 1, characterized in that: The method to determine the calculation expressions of thrust coefficient and side force coefficient of the fan model is: In the above formulas (1) and (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 The expression of (θ) is as follows (3)(4); In formula (3) and (4), B is the number of blades in the fan model equal to the number of blades in the full-scale fan. R is the impeller radius of the fan model, which is calculated according to Froude's similarity law. V is the inflow velocity, which is calculated according to Froude's similarity law. β is the target twist angle of the fan model blade; 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 parallel to the chord length acting on the local element of the blade, in, F n =L cos(θ)+D sin(θ) (5) F t =L sin(θ)-D cos(θ) (6) In the above equations (5) to (8), L is the lift acting on the unit blade length, and D is the drag acting on the unit blade length. ρ is the air density, c is the target chord length of the fan model blade, C L is the lift coefficient, is a known parameter of the low Reynolds number airfoil, C D is the drag coefficient, is a known parameter of the low Reynolds number airfoil, α is the angle of attack and can represent a variable that is only associated with β, Re represents the Reynolds number, which is Re m .

9. The blade reconstruction method of a floating vertical axis wind turbine model for scaled-down testing according to claim 1, characterized in that: The actual thrust coefficient C Tp and the actual lateral force coefficient C Sp Calculated by numerical calculation software.

10. The blade reconstruction method of a floating vertical axis wind turbine model for scaled-down testing according to claim 9, characterized in that: The numerical calculation software is QBlade.

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