A calculation method for the analytical model of accelerated flow in fan tip clearance

Abstract

The present invention discloses a calculation method for an analytical model of wind turbine tip clearance acceleration flow, belonging to the technical field of wind turbine velocity field calculation. By analyzing the aerodynamic characteristics of the wind turbine wake clearance acceleration zone, the correlation between the power increase of side-by-side wind turbines and the wind turbine wake clearance acceleration zone is revealed, and an analytical model is constructed based on the self-similarity of the clearance acceleration zone and the vortex equation. This model considers the local acceleration flow caused by the rotation of adjacent rotor blade tips in the same plane. The present invention adopts the above method, and the model used has high accuracy in predicting the flow field characteristics of the blade tip wake clearance acceleration zone. The prediction effect is close to that of high-fidelity numerical simulation methods, but the computational cost is far lower than traditional CFD simulation. It shows good applicability in simulating wind farm structures such as double-headed floating wind turbines and wind turbine walls that are closely arranged along the same y-z plane, and has excellent engineering application value.

Description

Technical Field

[0001] The present invention relates to the technical field of fan wake calculation, and in particular to a calculation method of a fan blade tip clearance acceleration flow analytical model. Background Art

[0002] In the design of traditional large-scale offshore wind farms, a sparse array arrangement is often used to avoid complex aerodynamic interference between side-by-side turbines and the superposition of interference with the wakes of the rear-exhaust turbines. While this arrangement helps reduce aerodynamic interference, it consumes significant space resources, thus limiting the wind farm's power generation density per unit area and its economic efficiency. In recent years, multi-rotor wind turbines, due to their structural advantages of integrating multiple standardized rotors, have gradually become a promising technology path. Not only do these turbines offer high economic efficiency in terms of structural complexity and material usage, but their compact configuration also holds the potential to break the space dependence of traditional arrangements and enhance the intensive development of wind energy. Although multi-rotor systems offer significant advantages in terms of space efficiency, the complex aerodynamic interference mechanisms associated with their side-by-side arrangement, particularly how to identify and understand the localized acceleration that may occur in the gaps between turbine wakes within this compact arrangement, remain under investigation. Although the calculation method of the radial induction area of ​​the fan can calculate the side-by-side interaction between multi-rotor fans, only calculating the influence of the radial induction area will lead to deviations in the final power calculation results. The wake gap acceleration area between the fans dominates the power increase of the multi-rotor fan. Only by modeling and calculating it can the nonlinear interaction effect between the wakes be accurately described. Summary of the Invention

[0003] The purpose of this invention is to provide a computational method for an analytical model of wind turbine tip clearance acceleration flow. By analyzing the aerodynamic characteristics of the wind turbine wake gap acceleration zone, the correlation between the power increase of side-by-side wind turbines and the wind turbine wake gap acceleration region is revealed. An analytical model is then constructed based on the self-similarity of the gap acceleration region and the vortex equations. This model, by considering the localized acceleration flow caused by the rotation of adjacent rotor tips in the same plane, provides a physical explanation for the power increase of adjacent wind turbines and illustrates the mutual influence between adjacent rotors in a dual-rotor wind turbine. The model achieves high accuracy in predicting the flow field characteristics of the wake gap acceleration region, approaching that of high-fidelity numerical simulation methods, while achieving computational costs far lower than traditional CFD simulations. The model demonstrates excellent applicability in simulating wind farm structures closely arranged along the same yz plane, such as dual-head floating wind turbines and wind turbine walls, and demonstrates excellent engineering application value.

[0004] To achieve the above object, the present invention provides a calculation method for an analytical model of accelerated flow at the tip clearance of a fan, comprising the following steps:

[0005] Step 1: Calculate one or several wind turbines arranged side by side in the wind farm, and select one wind turbine as the target for calculation;

[0006] Step 2: Assume that the radius of the target wind turbine in the wind farm is R and the inflow wind speed is , a cylindrical coordinate system is established with the center of the target wind turbine hub as the origin, in which the vertical wind turbine blades are set to the axial direction to the downstream Positive direction, radial Direction perpendicular to direction, at this time the coordinates of any point in the wind field are given by Indicates that the fan flow field area is divided into the tail flow area , wake blockage area and the tip wake clearance acceleration region ;

[0007] Step 3: Use the Axial Velocity Induction Factor and shape functions To establish the tip wake clearance acceleration region The normalized velocity field in Expressions of

[0008] Step 4: For the normalized velocity field The expression of is converted into the axial velocity induction factor using a composite Gaussian function based on the similarity of the velocity distribution in the acceleration area of ​​the blade tip wake gap. and the expression of thrust coefficient to obtain the result of axial velocity induction factor;

[0009] Step 5: For the normalized velocity field The shape function in the figure is segmented according to the velocity consistency law at different axial positions. , and segmentally represent the changing characteristics of the velocity field at different positions in the wake gap acceleration zone to obtain the shape function the result;

[0010] Step 6: Substitute the results of steps 4 and 5 into the normalized velocity field in step 3 The acceleration area of ​​the blade tip wake gap is obtained The normalized velocity field the result;

[0011] Step 7: Repeat steps 1 to 6 until all the fans are calculated. Superimpose the calculated results of all the fans to obtain the results of the acceleration area of ​​the fan blade tip wake gap.

[0012] Preferably, in step 2, the criteria for dividing the fan flow field area are as follows:

[0013] Based on the numerical simulation of the wind turbine flow field and experimental wind field data, combined with the wind speed attenuation characteristics, turbulence intensity distribution and streamline morphology, the wind turbine flow field area is systematically divided as follows:

[0014] The area on the main axis downstream of the wind turbine where the wind speed drops significantly and the turbulence intensity increases significantly is regarded as the wake area. , the area expands in the direction of wind in a columnar shape;

[0015] The streamline deflection phenomenon and local increase in wind speed observed upstream of the wind turbine identify the fluid accumulation and lateral flow area formed by the windward resistance effect of the wind turbine, which is defined as the wake blockage area. , which is manifested as a decrease in wind speed in the center area in front of the wind turbine and an increase on both sides;

[0016] By capturing the details of the area near the trailing edge of the fan blade, the shear layer flow and vortex structure generated between the fan blade tip and the non-blade area are identified. There is a local velocity enhancement phenomenon in this area, forming an elliptical acceleration zone that diffuses radially outward from the blade tip, which is defined as the blade tip wake gap acceleration area. .

[0017] Preferably, in step 3, the specific process is as follows:

[0018] For the wake gap acceleration region , and define its velocity field as , and the clearance is normalized to obtain the velocity field of the normalized blade tip wake clearance acceleration area as follows:

[0019] ;

[0020] ;

[0021] In the above formula, Indicates the axial coordinate value after standardization, Represents the normalized radial coordinate value, represents the velocity field in normalized axial and radial coordinate values, is the axial velocity induction factor, It is the shape function that controls the velocity change trend in the gap acceleration area.

[0022] Preferably, the axial velocity induction factor is performed in step 4. The calculation process is as follows:

[0023] The mathematical expression of local acceleration flow is constructed using a composite Gaussian function, and the axial velocity induction factor is established according to the similarity of the acceleration area of ​​the blade tip wake gap. The calculation formula is as follows

[0024] ;

[0025] In the above formula, 、 and is the calculation parameter, axial velocity induction factor exist Get the maximum value , by controlling To achieve the maximum value of the control equation The curves on both sides increase and decrease slowly. It represents the maximum axial wind speed induction factor, which is calculated by a cubic polynomial in combination with blade element momentum theory. The formula is as follows:

[0026] ;

[0027] In the above formula, 、 、 、 are all calculation parameters, is the thrust coefficient, which represents the ratio of the axial thrust exerted by the wind wheel to the dynamic pressure per unit area. Calculated by the following formula:

[0028] ;

[0029] ;

[0030] In the above formula, is the total thrust on the fan disk. is the air density, is the free inflow wind speed, Indicates the swept area of ​​the wind wheel.

[0031] Preferably, in calculating the axial velocity induction factor In the process, the specific values ​​of a set of calculation parameters are selected as follows: 、 、 、 , , , .

[0032] Preferably, in step 5, the three-dimensional shape function is calculated The specific process is as follows:

[0033] Through experimental analysis of the standardized velocity distribution curves at different inflow velocities, The velocity curves in the axial region show high consistency, while The area of ​​​​shows a law that it gradually increases with the increase of inflow velocity, and the shape function is established in the form of piecewise function , the calculation formula is as follows:

[0034] ;

[0035] In the above formula, and Indicates the parameters used for calculation, is the radial correction factor, used to correct The speed change at t is mainly used to correct the deviation caused by the change in radial position and the change in inflow wind speed. The formula is as follows:

[0036] ;

[0037] In the above formula, and Indicates the parameters used for calculation, is the thrust coefficient.

[0038] Preferably, the three-dimensional shape function is calculated In the process of , one way to select the calculation parameters is as follows: 、 、 , .

[0039] Preferably, in step 7, the calculated results of all the wind turbines are superimposed. A specific implementation method is to use a linear superposition method to linearly superimpose the calculated results of different wind turbines according to regions.

[0040] Therefore, the present invention adopts the above-mentioned calculation method of the fan blade tip clearance acceleration flow analytical model, which has the following advantages:

[0041] (1) In this paper, a three-dimensional analytical model calculation method for the steady-state wind turbine tip wake gap acceleration region is proposed. When predicting the flow field of a single wind turbine hub, the velocity error is kept within 6% compared with the computational fluid dynamics simulation results under the same conditions. When two wind turbines are arranged side by side, the error of the predicted power increase and the computational fluid dynamics simulation results is controlled within 5%. Therefore, the model has high accuracy in predicting the flow field characteristics of the wake gap acceleration region.

[0042] (2) The technical solution of the present invention can demonstrate good applicability in simulating wind farm structures such as double-headed floating wind turbines and wind turbine walls that are closely arranged along the same plane. While the prediction effect is close to that of high-fidelity numerical simulation methods, the computational cost is much lower than that of traditional computational fluid dynamics simulation.

[0043] (3) In the present invention, the correlation between the power improvement of parallel fans and the local acceleration area of ​​the fan wake gap is revealed by the numerical analysis method, and the blank that the engineering wake model lacks consideration of the influence of the local acceleration area of ​​the wake gap and cannot calculate the interaction between parallel fans is filled. The technical solution of the present invention is further described in detail below through the drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 This is a flow chart of a calculation method of an analytical model for accelerated flow at the tip clearance of a fan according to the present invention;

[0045] Figure 2 Schematic diagram of a cross section of a single fan wake gap acceleration region in a calculation method of a fan blade tip clearance acceleration flow analytical model according to the present invention;

[0046] Figure 3 A top view of the acceleration region of the wake gap of a single fan in a calculation method of an analytical model of the accelerated flow of the fan blade tip clearance according to the present invention;

[0047] Figure 4 A top view of the acceleration region of the wake gap of two fans in a calculation method of an analytical model of the accelerated flow of the fan blade tip clearance according to the present invention;

[0048] Figure 5 To calculate the xy plane contrast cloud map of a single fan flow field, Figure (a) shows the flow field map calculated using the method of the present invention, and Figure (b) shows the flow field map calculated using the high-simulation computational fluid dynamics method;

[0049] Figure 6 The technical solution of the present invention is used to calculate the yz plane flow field diagram of a single fan flow field;

[0050] Figure 7 The flow field diagram of the yz plane of a single fan flow field is calculated using a high-simulation computational fluid dynamics method;

[0051] Figure 8 The technical solution of the present invention is used to calculate the flow field diagram of the xz plane of a single fan flow field;

[0052] Figure 9 The flow field diagram of the xz plane of a single fan flow field is calculated using high-simulation computational fluid dynamics methods;

[0053] Figure 10 The velocity field calculated in the embodiment predicts the curve of the power generation efficiency improvement value when the spacing between parallel fans changes. DETAILED DESCRIPTION

[0054] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. The components of the embodiments of the present invention generally described and shown in the drawings here can be arranged and designed in various different configurations. The specific model specifications need to be selected and determined based on the actual specifications of the device, etc. The specific selection calculation method adopts the existing technology in this field, so it will not be described in detail.

[0055] Example

[0056] like Figure 1-Figure 4 As shown, the present invention provides a calculation method for the analytical model of the accelerated flow of the fan blade tip clearance, comprising the following steps:

[0057] Step 1: Calculate one or several wind turbines arranged side by side in the wind farm, and select one wind turbine as the target for calculation;

[0058] Step 2: Assume that the radius of the target wind turbine in the wind farm is R and the inflow wind speed is , a cylindrical coordinate system is established with the center of the target wind turbine hub as the origin, in which the vertical wind turbine blades are set to the axial direction to the downstream Positive direction, radial Direction perpendicular to direction, at this time the coordinates of any point in the wind field are given by In engineering calculations, because The direction component is small, so it can be ignored. The main calculation is Directional component, dividing the fan flow area into the wake area , wake blockage area and the tip wake clearance acceleration region ; The standards for dividing the fan flow field area are as follows:

[0059] Based on the numerical simulation of the wind turbine flow field and experimental wind field data, combined with the wind speed attenuation characteristics, turbulence intensity distribution and streamline morphology, the wind turbine flow field area is systematically divided as follows:

[0060] The area on the main axis downstream of the wind turbine where the wind speed drops significantly and the turbulence intensity increases significantly is regarded as the wake area. , the area expands in the direction of wind in a columnar shape;

[0061] The streamline deflection phenomenon and local increase in wind speed observed upstream of the wind turbine identify the fluid accumulation and lateral flow area formed by the windward resistance effect of the wind turbine, which is defined as the wake blockage area. , which is manifested as a decrease in wind speed in the center area in front of the wind turbine and a slight increase on both sides;

[0062] By capturing the details of the area near the trailing edge of the fan blade, the shear layer flow and vortex structure generated between the fan blade tip and the non-blade area are identified. There is a local velocity enhancement phenomenon in this area, forming an elliptical acceleration zone that diffuses radially outward from the blade tip, which is defined as the blade tip wake gap acceleration area. , which can be clearly identified by the velocity vector field and vorticity contour map, and has typical three-dimensional symmetry characteristics.

[0063] Step 3: Use the Axial Velocity Induction Factor and shape functions To establish the tip wake clearance acceleration region The normalized velocity field in The specific process is as follows:

[0064] Establishing regions using axial velocity induction factors The normalized velocity field in Expressions of

[0065] For the wake gap acceleration region , and define its velocity field as , and the gap is normalized to obtain the standardized wake gap acceleration area velocity field The expression is as follows

[0066] ;

[0067] ;

[0068] In the above formula, Indicates the axial coordinate value after standardization, Represents the normalized radial coordinate value, represents the velocity field in normalized axial and radial coordinate values, is the axial velocity induction factor, It is the shape function that controls the velocity variation trend in the gap acceleration area. In the present invention, the above formula is an analytical model.

[0069] Step 4: For the velocity field of the normalized wake gap acceleration region, although the distribution of the velocity curve in the r direction under different inflow wind speed conditions has certain differences, the overall acceleration trend is consistent. In order to more systematically describe the velocity distribution characteristics of the wake gap region, a composite Gaussian function is used to construct a mathematical expression of the local acceleration flow to achieve quantitative modeling of the gap acceleration region. To this end, the axial velocity induction factor is established based on the similarity of the blade tip wake gap acceleration region. The calculation formula is as follows

[0070] The mathematical expression of local acceleration flow is constructed using a composite Gaussian function, and the axial velocity induction factor is established based on the similarity of the wake gap acceleration region. The calculation formula is as follows:

[0071] ;

[0072] In the above formula, 、 and is the calculation parameter, 、 、 , axial velocity induction factor exist Get the maximum value , by controlling To achieve the maximum value of the control equation The increasing and decreasing trends of the curves on both sides are slow and rapid;

[0073] It represents the maximum axial wind speed induction factor, which is calculated by a cubic polynomial in combination with blade element momentum theory. The formula is as follows:

[0074] ;

[0075] In the above formula, 、 、 、 are all calculation parameters, , , , , Is the thrust coefficient, which represents the ratio of the axial thrust exerted by the wind wheel to the dynamic pressure per unit area. The thrust coefficient significantly affects the acceleration intensity in the wake gap of the parallel fans, especially the most direct control effect on the maximum speed value. Therefore, it can be considered that It is the key aerodynamic parameter that controls the acceleration characteristics of the side-by-side wake flow and has important guiding significance for the subsequent velocity distribution modeling and wind turbine layout optimization. Calculated by the following formula:

[0076] ;

[0077] ;

[0078] In the above formula, is the total thrust on the fan disk. is the air density, is the free inflow wind speed, Indicates the swept area of ​​the wind wheel.

[0079] Step 5: For the normalized velocity field The shape function in the figure is segmented according to the velocity consistency law at different axial positions. , and segmentally represent the changing characteristics of the velocity field at different positions in the wake gap acceleration zone to obtain the shape function The result of ; Calculate the three-dimensional shape function The specific process is as follows:

[0080] Through experimental analysis of the standardized velocity distribution curves at different inflow velocities, The velocity curves in the axial region show high consistency, while The area of ​​​​shows a law that it gradually increases with the increase of inflow velocity, and the shape function is established in the form of piecewise function , the calculation formula is as follows:

[0081] ;

[0082] In the above formula, and Indicates the parameters used for calculation, 、 , is the radial correction factor, used to correct The speed change at t is mainly used to correct the deviation caused by the change in radial position and the change in inflow wind speed. The formula is as follows:

[0083] ;

[0084] In the above formula, and Indicates the parameters used for calculation, , , is the thrust coefficient.

[0085] Step 6: Substitute the results of steps 4 and 5 into the normalized velocity field in step 3 The acceleration area of ​​the blade tip wake gap is obtained The normalized velocity field the result;

[0086] Step 7: Repeat steps 1 to 6 until all fans are calculated. Superimpose the calculated results of all fans to obtain the results of the acceleration area of ​​the fan blade tip wake gap. One specific implementation method is to use linear superposition to linearly superimpose the calculation results of different fans according to the area.

[0087] like Figure 5-10 , the specific experimental process is as follows:

[0088] To verify the model, it was programmed and integrated into the open source wind farm simulation tool PyWake to calculate and evaluate the wind turbine flow field and power. PyWake is an open source wind farm simulation platform developed based on Python. It is widely used to study the wake interaction between wind turbines in a wind farm and its impact on the overall performance of the wind farm. This tool can perform high-precision modeling of the aerodynamic characteristics within the wind farm and output the power generated by the wind turbines under different layouts and meteorological conditions. During the model evaluation process, in order to accurately evaluate the performance of the model and eliminate the interference caused by the selection of different wake models and wake blockage models, the flow field and power output around the wind turbine were simulated without the wake model and the blockage model. During the simulation experiment, the method of this application was compared with the large eddy simulation (LES) method.

[0089] like Figure 5 (a) and (b) show the comparison of the flow field simulation diagrams of the xy section at the hub center position of a single DTU10MW wind turbine calculated by different methods under the condition of 11.4m / s flow velocity; Figure 5 (a) is a flow field diagram calculated using the method of the present invention; Figure 5 (b) is the flow field diagram obtained by LES simulation. It can be observed that for the acceleration areas on both sides of the fan, the flow velocity presents an elliptical velocity structure that diffuses from the inside to the outside along the lower part of the fan blade tip. Excluding the influence of the wake and blockage areas, the flow field morphology predicted by the model is highly consistent with the LES simulation results in structure.

[0090] like Figure 6-Figure 7 , showing that different methods can achieve the same results under the conditions of 11.4m / s inflow wind speed. yz-plane flow field diagram taken at . The velocity contours of the flow field calculated by the present invention exhibit a uniformly diffused annular structure, which is generally consistent with the LES prediction results. As the x value increases, the diffusion of the flow field distribution increases for both the model and the LES, and the magnitude of the enhancement remains largely consistent, further validating the model's predictive performance at different axial positions.

[0091] Figure 8-Figure 9 , which shows that different methods can achieve the same results along the It can be seen that the xz-plane flow field predicted by the method of the present invention has good consistency with the LES simulation results in terms of overall shape, and basically conforms to the velocity variation trend in the wake gap acceleration region.

[0092] Under the condition of an inflow wind speed of 11.4m / s, a classic wind field calculation example of two wind turbines arranged side by side was simulated. Five sets of wind field data were calculated by setting the hub center distances of the two wind turbines to 2R, 4R, 6R, 8R and 10R respectively. The data results are as follows: Figure 10As shown in the figure, these simulation results are compared with the data obtained by LES simulation under the same configuration. The power of the side-by-side fans in the model and LES simulation is improved due to the mutual influence of the wake acceleration area between the fans. The improvement value is as follows Figure 10 As shown in the figure, when the spacing between parallel fans is small (2R), the power of a single fan can be increased by 6%. However, as the spacing between parallel fans increases, the power improvement effect gradually decreases. This trend is consistent with the physical mechanism that the acceleration area of ​​the fan wake gap gradually decreases with increasing radial distance r. Figure 10 The error bars in the figure represent the ±5% error range of the LES simulated power boost results. It can be seen that the power boost predictions from the model constructed using the technical solution of the present invention are highly consistent with the LES in terms of trend, and the error of the model-predicted power boost values ​​relative to the LES results is generally controlled within 5% at all spacings. Considering that the prediction error of engineering wake models is generally above 10%, it is concluded that the wake gap acceleration region model proposed in this invention demonstrates good accuracy and practicality in predicting the power of side-by-side wind turbines.

[0093] The proposed analytical model also offers significant advantages in computational efficiency. On a single-core workstation, a single simulation of a parallel wind turbine example takes only about 2 to 3 seconds, significantly less than the computational time required for traditional high-fidelity numerical simulations. This demonstrates that the proposed model not only demonstrates excellent prediction accuracy but also offers significant advantages in computational cost, demonstrating its potential for application in large-scale wind farm layout optimization and real-time evaluation.

[0094] Therefore, the present invention adopts a calculation method for an analytical model of the accelerated flow of the wind turbine tip gap. By analyzing the aerodynamic characteristics of the wind turbine wake gap acceleration zone, the correlation between the power increase of side-by-side wind turbines and the wind turbine wake gap acceleration zone is revealed, and an analytical model is constructed based on the self-similarity and eddy flow equation of the gap acceleration zone. The model considers the local accelerated flow caused by the rotation of the adjacent rotor blade tips in the same plane, realizes the physical explanation of the power increase of adjacent wind turbines, and clarifies the mutual influence effect between adjacent rotors in a dual-rotor wind turbine. The model has high accuracy in predicting the flow field characteristics of the wake gap acceleration zone, and the prediction effect is close to the high-fidelity numerical simulation method, but the computational cost is much lower than the traditional CFD simulation. It shows good applicability in simulating wind farm structures such as double-head floating wind turbines and wind turbine walls that are closely arranged along the same yz plane, and shows good engineering application value.

[0095] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solutions of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A calculation method for an analytical model of accelerated flow at fan tip clearance, characterized by: The following steps are involved: Step 1: Calculate one or several wind turbines arranged side by side in the wind farm, and select one wind turbine as the target for calculation; Step 2: Assume that the radius of the target wind turbine in the wind farm is R and the inflow wind speed is , a cylindrical coordinate system is established with the center of the target wind turbine hub as the origin, in which the vertical wind turbine blades are set to the axial direction to the downstream Positive direction, radial Direction perpendicular to direction, at this time the coordinates of any point in the wind field are given by Indicates that the fan flow field area is divided into the tail flow area , wake blockage area and the tip wake clearance acceleration region ; Step 3: Use the Axial Velocity Induction Factor and shape functions To establish the tip wake clearance acceleration region The normalized velocity field in Expressions of Step 4: For the normalized velocity field The expression of is converted into the axial velocity induction factor using a composite Gaussian function based on the similarity of the velocity distribution in the acceleration area of ​​the blade tip wake gap. and the expression of thrust coefficient to obtain the result of axial velocity induction factor; Step 5: For the normalized velocity field The shape function in the figure is segmented according to the velocity consistency law at different axial positions. , and segmentally represent the changing characteristics of the velocity field at different positions in the wake gap acceleration zone to obtain the shape function the result; Step 6: Substitute the results of steps 4 and 5 into the normalized velocity field in step 3 The acceleration area of ​​the blade tip wake gap is obtained The normalized velocity field the result; Step 7: Repeat steps 1 to 6 until all the fans are calculated. Superimpose the calculated results of all the fans to obtain the results of the acceleration area of ​​the fan blade tip wake gap.

2. The calculation method of the fan tip clearance acceleration flow analytical model according to claim 1 is characterized by: In step 2, the criteria for dividing the fan flow field area are as follows: Based on the numerical simulation of the wind turbine flow field and experimental wind field data, combined with the wind speed attenuation characteristics, turbulence intensity distribution and streamline morphology, the wind turbine flow field area is systematically divided as follows: The area on the main axis downstream of the wind turbine where the wind speed drops significantly and the turbulence intensity increases significantly is regarded as the wake area. , the area expands in the direction of wind in a columnar shape; The streamline deflection phenomenon and local increase in wind speed observed upstream of the wind turbine identify the fluid accumulation and lateral flow area formed by the windward resistance effect of the wind turbine, which is defined as the wake blockage area. , which is manifested as a decrease in wind speed in the center area in front of the wind turbine and an increase on both sides; By capturing the details of the area near the trailing edge of the fan blade, the shear layer flow and vortex structure generated between the fan blade tip and the non-blade area are identified. There is a local velocity enhancement phenomenon in this area, forming an elliptical acceleration zone that diffuses radially outward from the blade tip, which is defined as the blade tip wake gap acceleration area. .

3. The calculation method of the fan tip clearance acceleration flow analytical model according to claim 1 is characterized by: In step 3, the specific process is as follows: For the wake gap acceleration region , and define its velocity field as , and the clearance is normalized to obtain the velocity field of the normalized blade tip wake clearance acceleration area as follows: ； ； In the above formula, Indicates the axial coordinate value after standardization, Represents the normalized radial coordinate value, represents the velocity field in normalized axial and radial coordinate values, is the axial velocity induction factor, It is the shape function that controls the velocity change trend in the gap acceleration area.

4. The calculation method of the fan tip clearance acceleration flow analytical model according to claim 1 is characterized by: In step 4, the axial velocity induction factor The calculation process is as follows: The mathematical expression of local acceleration flow is constructed using a composite Gaussian function, and the axial velocity induction factor is established according to the similarity of the acceleration area of ​​the blade tip wake gap. The calculation formula is as follows ； In the above formula, 、 and is the calculation parameter, axial velocity induction factor exist Get the maximum value , by controlling To achieve the maximum value of the control equation The curves on both sides increase and decrease slowly. It represents the maximum axial wind speed induction factor, which is calculated by a cubic polynomial in combination with blade element momentum theory. The formula is as follows: ； In the above formula, 、 、 、 are all calculation parameters, is the thrust coefficient, which represents the ratio of the axial thrust exerted by the wind wheel to the dynamic pressure per unit area. Calculated by the following formula: ； ； In the above formula, is the total thrust on the fan disk. is the air density, is the free inflow wind speed, Indicates the swept area of ​​the wind wheel.

5. The calculation method of the fan tip clearance acceleration flow analytical model according to claim 4 is characterized by: In calculating the axial velocity induction factor In the process, the specific values ​​of a set of calculation parameters are selected as follows: 、 、 、 , , , .

6. The calculation method of the fan tip clearance acceleration flow analytical model according to claim 3 is characterized by: In step 5, the shape function is calculated The specific process is as follows: Through experimental analysis of the standardized velocity distribution curves at different inflow velocities, The velocity curves in the axial region show high consistency, while The area of ​​​​shows a law that it gradually increases with the increase of inflow velocity, and the shape function is established in the form of piecewise function , the calculation formula is as follows: ； In the above formula, and Indicates the parameters used for calculation, is the radial correction factor, used to correct The speed change at t is mainly used to correct the deviation caused by the change in radial position and the change in inflow wind speed. The formula is as follows: ； In the above formula, and Indicates the parameters used for calculation, is the thrust coefficient.

7. The calculation method of the fan tip clearance acceleration flow analytical model according to claim 6, characterized in that: Calculating shape functions In the process of , one way to select the calculation parameters is as follows: 、 、 , .

8. The calculation method of the fan tip clearance acceleration flow analytical model according to claim 1 is characterized by: In step 7, the calculated results of all wind turbines are superimposed. A specific implementation method is to use a linear superposition method to linearly superimpose the calculated results of different wind turbines according to the region.

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