Calculation method of fan blade tip gap accelerated flow analytical model

Abstract

The invention discloses a calculation method of a fan blade tip gap accelerated flow analytical model, and belongs to the technical field of fan speed field calculation. By analyzing the aerodynamic characteristics of a fan wake flow gap acceleration area, the correlation between the power increase of the side-by-side fan and the fan wake flow gap acceleration area is disclosed, and an analytical model is constructed according to the self-similarity of the gap acceleration area and an eddy current equation. According to the model, local accelerated flow caused by rotation of adjacent rotor blade tips under the same plane is considered, by adopting the method, the used model has high precision in the aspect of predicting the flow field characteristics of the blade tip wake flow gap acceleration area, the prediction effect is close to that of a high-fidelity numerical simulation method, but the calculation cost is far lower than that of traditional CFD simulation; the method is well applicable to processing and simulating wind power plant structures which are closely arranged along the y-z same plane, such as a double-head floating fan and a fan wall, and shows good engineering application value.

Description

Technical Field

[0001] The present invention relates to the technical field of wind turbine wake calculation, and in particular to a calculation method for an analytical model of accelerated flow in the tip clearance of a wind turbine. Background Art

[0002] In the design of traditional large-scale offshore wind farms, in order to avoid complex aerodynamic interference between side-by-side wind turbines and the superposition of wake interference on the rear-row wind turbines, a relatively sparse array layout is often adopted. Although this layout helps to reduce aerodynamic interference, it occupies a large amount of space and site resources, thus limiting the power generation density and economy per unit area of the wind farm. In recent years, multi-rotor wind turbines have gradually become a technically promising path due to their structural advantages of integrating multiple standardized rotors. Such wind turbines not only show high economy in terms of structural complexity and material use, but also, due to their compact configuration, are expected to break the dependence on space of traditional layouts and improve the intensification level of wind energy development. Although the multi-rotor system has obvious advantages in space utilization efficiency, the complex aerodynamic interference mechanism brought about by its side-by-side layout, especially how to identify and understand the possible local acceleration phenomenon in the wake clearance area of the wind turbine, still needs to be studied in depth. Although the calculation method for the radial induction area of the wind turbine can calculate the side-by-side interaction between multi-rotor wind turbines, simply calculating the influence of the radial induction area will lead to deviations in the final power calculation result. The wake clearance acceleration area between the wind turbines dominates the power increase of the multi-rotor wind turbine. Modeling and calculating it can accurately describe the non-linear interaction effect between the wakes. Summary of the Invention

[0003] The purpose of the present invention is to provide a calculation method for an analytical model of accelerated flow in the tip clearance of a wind turbine. By analyzing the aerodynamic characteristics of the wake clearance acceleration area of the wind turbine, the correlation between the power increase of side-by-side wind turbines and the wake clearance acceleration area of the wind turbine is revealed, and an analytical model is constructed based on the self-similarity and vorticity equation of the clearance acceleration area. This model considers the local accelerated flow caused by the rotation of the tips of adjacent rotors in the same plane, realizes a physical explanation for the power increase of adjacent wind turbines, and clarifies the mutual influence effect between adjacent rotors in a dual-rotor wind turbine. This model has high accuracy in predicting the flow field characteristics of the wake clearance acceleration area, and the prediction effect is close to that of high-fidelity numerical simulation methods, but the calculation cost is much lower than that of traditional CFD simulations. It shows good applicability in dealing with wind farm structures such as simulated twin floating wind turbines and wind turbine walls that are closely arranged in the y-z same plane, and shows good engineering application value.

[0004] To achieve the above object, the present invention provides a calculation method for an analytical model of accelerated flow in the tip clearance of a wind turbine, including the following steps: Step 1: Calculate one or several wind turbines arranged side by side in a wind farm, and select one wind turbine as the target for calculation; Step 2: Assume the radius of the target wind turbine in the wind farm is R, and the incoming flow wind speed is , establish a cylindrical coordinate system with the center of the target wind turbine hub as the origin, where the direction perpendicular to the wind turbine blade and downstream is set as the axial positive direction, and the radial direction is perpendicular to the direction. At this time, the coordinates of any point in the wind farm are all represented by . Divide the wind turbine flow field area into a wake region , a wake blockage region and a tip wake gap acceleration region ; Step 3: Use the axial velocity induction factor and the shape function to establish the expression of the normalized velocity field in the tip wake gap acceleration region [[ID=2�]] ; Step 4: For the expression of the normalized velocity field , based on the similarity of the velocity distribution in the tip wake gap acceleration region, transform it into using a composite Gaussian function to establish the expressions of the axial velocity induction factor and the thrust coefficient, and obtain the result of the axial velocity induction factor; Step 5: For the shape function in the normalized velocity field , according to the velocity consistency law at different axial positions, segment the shape function , and segmentally represent the variation characteristics of the velocity field at different positions in the wake gap acceleration region, and obtain the result of the shape function ; Step 6: Substitute the results of Step 4 and Step 5 into the normalized velocity field in Step 3 to obtain the result of the normalized velocity field of the tip wake gap acceleration region ; Step 7: Repeat Step 1 to Step 6 until all wind turbines are calculated, and superimpose the results calculated for all wind turbines to obtain the result of the tip wake gap acceleration region of the wind turbines.

[0005] Preferably, in Step 2, the criteria for dividing the wind turbine flow field area are as follows: Based on the numerical simulation of the wind turbine flow field and the experimental wind farm data, combined with the wind speed attenuation characteristics, turbulence intensity distribution and streamline morphology, systematically divide the wind turbine flow field area as follows: The area where the wind speed on the main axis downstream of the wind turbine decreases significantly and the turbulence intensity increases significantly is defined as the wake area. This area extends along the wind direction in a columnar shape. The streamline deflection phenomenon and the local wind speed increase characteristics observed upstream of the wind turbine's windward surface are used to identify the fluid accumulation and lateral flow-around area formed due to the windward resistance effect of the wind turbine, which is defined as the wake blockage area. It is manifested as a decrease in the wind speed in the central 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 wind turbine blade, the shear layer flow and vortex structure generated between the tip of the wind turbine blade and the non-blade area are identified. There is a local increase in velocity in this area, forming an elliptical acceleration band that diffuses radially outside the tip, which is defined as the tip wake gap acceleration area. .

[0006] Preferably, in step 3, the specific process is as follows: For the tip wake gap acceleration area , its velocity field is defined as , and after normalizing its gap, the velocity field of the normalized tip wake gap acceleration area is obtained as follows: ; ;

[0007] In the above formula, represents the normalized axial coordinate value, represents the normalized radial coordinate value, represents the velocity field at the normalized axial and radial coordinate values, is the axial velocity induction factor, is the shape function that controls the velocity change trend in the gap acceleration area.

[0008] Preferably, in step 4, the calculation process of the axial velocity induction factor is as follows: A mathematical expression for local accelerated flow is constructed using a composite Gaussian function, and the calculation formula for the axial velocity induction factor is established according to the similarity of the tip wake gap acceleration area as follows ;

[0009] In the above formula, , and are calculation parameters, and the axial velocity induction factor reaches the maximum value at , and by controlling to achieve the slow or rapid increasing and decreasing trends of the curves on both sides of the control equation when it reaches the maximum value The curves on both sides have slow or rapid increasing and decreasing trends, denotes the axial maximum wind speed induction factor, which is calculated by a cubic polynomial in combination with the blade element momentum theory. The formula is as follows: ;

[0010] In the above formula, , , , are all calculation parameters, is the thrust coefficient, representing the ratio of the axial thrust exerted by the wind turbine to the dynamic pressure per unit area. It is calculated by the following formula: The formula is as follows: ; ;

[0011] In the above formula, is the total thrust received by the wind turbine disk, is the air density, is the free inflow wind speed, represents the swept area of the wind turbine.

[0012] Preferably, during the process of calculating the axial velocity induction factor , the specific values of a set of calculation parameters are selected as follows: , , , , , , .

[0013] Preferably, in step 5, the specific process of calculating the three-dimensional shape function is as follows: By experimentally analyzing the standardized velocity distribution curves at different inflow velocities, the velocity curves in the axial region of show relatively high consistency, while in the region of they show a law of gradually increasing with the increase of the inflow velocity. The shape function is established in the form of a piecewise function. The calculation formula is as follows: ;

[0014] In the above formula, and represent the parameters used in the calculation, is the radial correction factor, which is used to correct the velocity change when . It mainly corrects the deviation caused by the change of the radial position and the change of the inflow wind speed. The formula is as follows: ;

[0015] In the above formula, and represent the parameters for calculation, is the thrust coefficient.

[0016] Preferably, in the process of calculating the three-dimensional shape function a method for selecting a calculation parameter is as follows: , , , .

[0017] Preferably, in step 7, the results calculated by all the fans are superimposed. A specific implementation method is to use linear superposition to linearly superimpose the calculation results of different fans according to regions.

[0018] Therefore, the calculation method of the fan tip clearance accelerated flow analysis model of the present invention has the following advantages: (1) In the present invention, an analytical model calculation method for the three-dimensional steady-state fan tip wake clearance acceleration region is proposed. The velocity error between this method and the computational fluid dynamics simulation results under the same conditions is kept within 6% when predicting the flow field of a single fan hub plane; in the case of arranging two fans side by side, the error between the predicted power increase and the computational fluid dynamics simulation results is controlled within 5%. Therefore, this model has high accuracy in predicting the flow field characteristics of the wake clearance acceleration region.

[0019] (2) The technical solution of the present invention can show good applicability in simulating wind farm structures such as double-headed floating fans and fan walls arranged closely along the same plane. While the prediction effect is close to that of the high-fidelity numerical simulation method, the calculation cost is much lower than that of the traditional computational fluid dynamics simulation.

[0020] (3) In the present invention, the correlation between the power increase of side-by-side fans and the local acceleration region of the fan wake clearance is revealed by numerical analysis methods, and it fills the gap that the engineering wake model lacks consideration of the influence of the local acceleration region of the wake clearance and cannot calculate the interaction between side-by-side fans. The following further describes the technical solution of the present invention in detail through the drawings and embodiments. Brief Description of the Drawings

[0021] Figure 1 is the flow chart of the calculation method of the fan tip clearance accelerated flow analysis model of the present invention; Figure 2 is the schematic diagram of the cross-section of the single-fan wake clearance acceleration region in the calculation method of the fan tip clearance accelerated flow analysis model of the present invention; Figure 3 This is a top view of the wake gap acceleration region of a single wind turbine in the calculation method of the analytical model for accelerating the flow of the wind turbine tip clearance according to the present invention; Figure 4 This is a top view of the wake gap acceleration region of a dual wind turbine in the calculation method of the analytical model for accelerating the flow of the wind turbine tip clearance according to the present invention; Figure 5 This is a comparison cloud map of the x-y plane of the flow field of a single wind turbine. 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-fidelity computational fluid dynamics method; Figure 6 This is the y-z plane flow field map of the flow field of a single wind turbine calculated according to the technical solution of the present invention; Figure 7 This is the flow field map of the y-z plane of the flow field of a single wind turbine calculated using the high-fidelity computational fluid dynamics method; Figure 8 This is the x-z plane flow field map of the flow field of a single wind turbine calculated according to the technical solution of the present invention; Figure 9 This is the x-z plane flow field map of the flow field of a single wind turbine calculated using the high-fidelity computational fluid dynamics method; Figure 10 This is the curve of the predicted power generation efficiency improvement value when the speed field of the parallel wind turbines changes with the distance between the wind turbines obtained by calculation in the embodiment; Detailed implementation manners

[0022] To make the objectives, 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 accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Usually, the components of the embodiments of the present invention described and shown in the accompanying drawings here can be arranged and designed in various different configurations. The specific model specifications need to be selected according to the actual specifications of the device, etc. The specific selection calculation method adopts the existing technology in the art, so it will not be elaborated in detail.

[0023] Embodiment

[0024] As Figures 1-4 shown, the present invention provides a calculation method for an analytical model of accelerating the flow of the wind turbine tip clearance, including the following steps: Step 1: Calculate one or several wind turbines arranged side by side in a 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 incoming flow velocity is , and a cylindrical coordinate system is established with the center of the hub of the target wind turbine as the origin, where the direction perpendicular to the wind turbine blade and downstream is set as the axial direction Positive direction, radial direction The direction is perpendicular to the direction. At this time, the coordinates of any point in the wind field are all represented by . In engineering calculations, because the component in the direction is relatively small, it is therefore neglected. The main calculation is the component in the direction. The wind turbine flow field area is divided into a wake region , a wake blockage region and a tip wake gap acceleration region . The criteria for dividing the wind turbine flow field area are as follows: . Based on the numerical simulation of the wind turbine flow field and the experimental wind field data, combined with the wind speed decay characteristics, turbulence intensity distribution and streamline morphology, the wind turbine flow field area is systematically divided as follows: . The region where the wind speed on the main axis downstream of the wind turbine drops significantly and the turbulence intensity increases significantly is used as the wake region . This region extends along the wind direction in a columnar shape; . The streamline deflection phenomenon observed upstream of the wind turbine's windward surface and the local wind speed increase characteristics are used to identify the fluid accumulation and lateral flow around region formed due to the windward resistance effect of the wind turbine, which is defined as the wake blockage region . It is manifested as a decrease in the wind speed in the central region in front of the wind turbine and a slight increase on both sides;

[0025] Step 3: Use the axial velocity induction factor and the shape function to establish the expression of the normalized velocity field in the tip wake gap acceleration region . The specific process is as follows: Use the axial velocity induction factor to establish the expression of the normalized velocity field in the region ; For the tip wake gap acceleration region , define its velocity field as , and perform gap standard normalization on it to obtain the normalized tip wake gap acceleration region velocity field The expression is as follows ; ;

[0026] In the above formula, represents the axial coordinate value after normalization, represents the radial coordinate value after normalization, represents the velocity field under the normalized axial and radial coordinate values, is the axial velocity induction factor, is the shape function that controls the velocity change trend in the gap acceleration region. In the present invention, the above formula is an analytical model.

[0027] Step 4: For the velocity field in 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 shows a consistent acceleration trend. In order to more systematically describe the velocity distribution characteristics in the wake gap region, a composite Gaussian function is used to construct a mathematical expression for the local accelerated flow to achieve quantitative modeling of the gap acceleration region. For this, the axial velocity induction factor is established based on the similarity of the tip wake gap acceleration region, and the calculation formula is as follows

[0028] Using a composite Gaussian function to construct a mathematical expression for the local accelerated flow, the axial velocity induction factor is established based on the similarity of the wake gap acceleration region, and the calculation formula is as follows: ;

[0029] In the above formula, , and are calculation parameters, , , , the axial velocity induction factor reaches the maximum value at , and by controlling to achieve controlling the curve increase and decrease trends on both sides of where the equation reaches the maximum value; represents the axial maximum wind speed induction factor, which is calculated by a cubic polynomial in combination with the blade element momentum theory. The formula is as follows: ;

[0030] In the above formula, , , , are all calculation parameters, , , , , is the thrust coefficient, representing the ratio of the axial thrust exerted by the wind turbine to the dynamic pressure per unit area. The thrust coefficient significantly affects the acceleration intensity in the wake gap between side-by-side wind turbines, especially having the most direct control effect on the maximum speed value. Therefore, it can be considered that is the key aerodynamic parameter that controls the acceleration characteristics of the side-by-side wake, and has important guiding significance for subsequent speed distribution modeling and wind turbine layout optimization. It is calculated by the following formula: ; ;

[0031] In the above formula, is the total thrust received by the wind turbine disk, is the air density, is the free inflow wind speed, represents the swept area of the wind turbine.

[0032] Step 5: For the shape function in the standardized velocity field According to the velocity consistency law at different axial positions, segment the shape function , and represent the variation characteristics of the velocity field at different positions in the wake gap acceleration zone in segments to obtain the result of the shape function ; The specific process of calculating the three-dimensional shape function is as follows: Analyze the standardized velocity distribution curves at different inflow velocities through experiments. In the axial region, the velocity curves show high consistency, while in the region, they show a law of gradually increasing with the increase of the inflow velocity. Establish the shape function in the form of a piecewise function, and the calculation formula is as follows: ;

[0033] In the above formula, and represent the parameters used in the calculation, 、 , is the radial correction factor, used to correct the velocity change when , mainly correcting the deviation caused by the change of the radial position and the inflow wind speed. The formula is as follows: ;

[0034] In the above formula, and represent the parameters used in the calculation, , , is the thrust coefficient.

[0035] Step 6: Substitute the results of Step 4 and Step 5 into the standardized velocity field in Step 3 to obtain the standardized velocity field of the tip wake gap acceleration region ; Result; Step 7: Repeat Step 1 to Step 6 until all the wind turbines are calculated. Superimpose the results calculated for all the wind turbines to obtain the result of the tip wake gap acceleration region of the wind turbines. One specific implementation method is to use linear superposition, and linearly superimpose the calculation results of different wind turbines according to regions.

[0036] As Figures 5-10 , the specific experimental process is as follows: To verify the model, it is programmed and integrated into the open-source wind farm simulation tool PyWake to achieve the calculation and evaluation of the flow field and power of the wind turbines. PyWake is an open-source wind farm simulation platform developed based on Python, which 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 accurately model the aerodynamic characteristics in the wind farm and output the power generation of the wind turbines under different layouts and meteorological conditions. During the evaluation process of the model, in order to accurately evaluate the performance of the model and eliminate the interference caused by selecting different wake models and wake blockage models, the flow field and power output around the wind turbines are simulated and calculated under the premise of no wake model and blockage model. During the simulation experiment, the method of this application is compared with the large eddy simulation (LES) method.

[0037] As Figure 5 in (a) and (b), it shows the comparison of the flow field simulation diagrams of the xy section at the hub center position of a single DTU10MW wind turbine under the inflow wind speed condition of 11.4m / s calculated by different methods; Figure 5 (a) in is the flow field diagram calculated by the method of the present invention; Figure 5 (b) in is the flow field diagram obtained by LES simulation. It can be observed that for the acceleration regions on both sides of the wind turbine, the flow velocity shows an elliptical velocity structure that diffuses from the inside to the outside along the lower part of the wind turbine tip. Excluding the influence of the wake and blockage regions, the flow field morphology predicted by the model is highly consistent with the LES simulation result in terms of structure.

[0038] As Figures 6-7 , it shows that under the inflow wind speed condition of 11.4m / s, along The yz-plane flow field diagram taken at this location. Among them, the flow field velocity isolines of the calculation results of the present invention show an annular structure that diffuses uniformly around, which is basically consistent with the prediction results of LES. As the value of x increases, the diffusion degree of the flow field distributions of the model and LES both increases, and the increasing amplitude basically remains the same, further verifying the prediction performance of the model at different axial positions.

[0039] Figures 8-9 , which shows the xz-plane flow field diagram taken along... under the inflow wind speed condition of 11.4 m / s for different methods. 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 the overall shape, and basically conforms to the velocity change trend in the wake gap acceleration region.

[0040] Under the inflow wind speed condition of 11.4 m / s, a simulation was carried out on a classic wind farm example with two wind turbines arranged side by side. By setting the hub center distances of the two wind turbines to be 2R, 4R, 6R, 8R, and 10R respectively, 5 groups of wind farm data were calculated. The data results are as Figure 10 shown, and these simulation results were compared and analyzed with the data obtained by LES simulation under the same configuration. The power of the side-by-side wind turbines in the model and LES simulations both increased due to the mutual influence of the wake acceleration regions of the wind turbine gaps. The increased values are as Figure 10 shown. In the case where the side-by-side wind turbine spacing is small (2R), the power increase of a single wind turbine can reach 6%. As the side-by-side wind turbine spacing increases, the wind turbine power increase effect gradually weakens, and this trend also conforms to the physical mechanism that the wake gap acceleration region of the wind turbine gradually decreases with the increase of the radial distance r. Figure 10 The error bars in... represent the ±5% error range of the LES simulation power increase results. It can be seen that the power increase prediction of the model constructed by the technical solution of the present invention is highly consistent with LES in trend, and the error of the power increase value predicted by the model relative to the LES results is basically controlled within 5% at all spacings. Considering that the prediction error of the engineering wake model is generally above 10%, it is thus judged that the wake gap acceleration region model proposed by the present invention shows good accuracy and practicability in the prediction of the power of side-by-side wind turbines.

[0041] The proposed analytical model also has significant advantages in terms of computational efficiency. On a workstation, under the condition of single-core operation, it only takes about 2 to 3 seconds to complete a single simulation of the side-by-side wind turbine example, which is significantly lower than the computational time required for traditional high-fidelity numerical simulations. It can be seen that this model not only has good performance in prediction accuracy, but also has great advantages in terms of computational cost, and has the application potential in the layout optimization and real-time evaluation of large-scale wind farms.

[0042] Therefore, the present invention adopts a calculation method of an analytical model for accelerating the flow of the tip clearance of a wind turbine. By analyzing the aerodynamic characteristics of the wake clearance acceleration region of the wind turbine, the correlation between the power increase of the side-by-side wind turbines and the wake clearance acceleration region of the wind turbine is revealed. An analytical model is constructed based on the self-similarity and vorticity equation of the clearance acceleration region. This model considers the local accelerated flow caused by the rotation of the tips of adjacent rotors in the same plane, realizes a physical explanation for the increase in the power of adjacent wind turbines, and clarifies the mutual influence effect between adjacent rotors in a dual-rotor wind turbine. This model has high accuracy in predicting the flow field characteristics of the wake clearance acceleration region, and the prediction effect is close to that of the high-fidelity numerical simulation method, but the calculation cost is much lower than that of the traditional CFD simulation. It shows good applicability in dealing with wind farm structures such as simulated dual-head floating wind turbines and wind turbine walls that are closely arranged in the y-z same plane, and shows good engineering application value.

[0043] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that they can still modify or equivalently replace the technical solutions of the present invention, and these modifications or equivalent replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A calculation method for an analytical model of accelerating the flow of the tip clearance of a fan, characterized in that: Including the following steps: Step 1: Calculate one or several wind turbines arranged side by side in a wind farm, and select one wind turbine as the target for calculation; Step 2: Set the radius of the target wind turbine in the wind farm as R, and the inflow wind speed as , and establish a cylindrical coordinate system with the center of the target wind turbine hub as the origin, where the direction perpendicular to the wind turbine blades and downstream is set as the axial positive direction, and the radial direction is perpendicular to the direction. At this time, the coordinates of any point in the wind farm are all represented by . Divide the wind turbine flow field area into a wake region , a wake blockage area and a tip wake gap acceleration region ; Step 3: Use the axial velocity induction factor and the shape function to establish the expression of the normalized velocity field in the tip wake gap acceleration region ; Step 4: For the expression of the standardized velocity field Based on the similarity of the velocity distribution in the acceleration region of the tip wake gap, it is transformed into an expression for establishing the axial velocity induction factor using a composite Gaussian function and the thrust coefficient, and the result of the axial velocity induction factor is obtained; Step 5: For the shape function in the standardized velocity field, segment the shape function according to the velocity consistency law at different axial positions, and segmentally represent the variation characteristics of the velocity fields at different positions in the wake gap acceleration region to obtain the result of the shape function; Step 6: Substitute the results of Step 4 and Step 5 into the standardized velocity field in Step 3 to obtain the standardized velocity field of the tip wake gap acceleration region and the result thereof; Step 7: Repeat Step 1 to Step 6 until the calculations for all wind turbines are completed, and superimpose the results calculated for all wind turbines to obtain the result of the accelerated region of the tip wake gap of the wind turbines.

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

3. The calculation method of an analytical model for accelerating the flow of the tip clearance of a fan according to claim 1, characterized in that: In Step 3, the specific process is as follows: For the wake gap acceleration region , its velocity field is defined as , and its gap is normalized to obtain the velocity field of the normalized tip wake gap acceleration region as follows: ； ； In the above formula, represents the normalized axial coordinate value, represents the normalized radial coordinate value, represents the velocity field at the normalized axial and radial coordinate values, is the axial velocity induction factor, is the shape function that controls the velocity change trend in the clearance acceleration region.

4. The calculation method of an analytical model for accelerating the flow of the tip clearance of a fan according to claim 1, characterized in that: In the above step 4, the calculation process of the axial velocity induction factor is as follows: Construct a mathematical expression for local accelerated flow using a composite Gaussian function, and establish a calculation formula for the axial velocity induction factor as follows ； In the above formula, , and are calculation parameters, and the axial velocity induction factor reaches the maximum value at . By controlling , the increasing and decreasing trends of the curves on both sides of the control equation at the maximum value are controlled, and represents the axial maximum wind speed induction factor, which is calculated by a cubic polynomial in combination with the blade element momentum theory. The formula is as follows: ； In the above formula, , , , are all calculation parameters, is the thrust coefficient, representing the ratio of the axial thrust exerted by the wind turbine to the dynamic pressure per unit area, is calculated by the following formula: ； ； In the above formula, is the total thrust on the fan disk surface, is the air density, is the free inflow wind speed, represents the swept area of the wind turbine rotor.

5. The calculation method of an analytical model for accelerating the flow of the fan tip clearance according to claim 4, characterized in that: In the process of calculating the axial velocity induction factor , the specific numerical values of a set of calculation parameters are selected as follows: , , , , , , .

6. The calculation method of an analytical model for accelerating the flow of the tip clearance of a fan according to claim 3, characterized in that: In step 5, the specific process of calculating the three-dimensional shape function is as follows: By experimentally analyzing the standardized velocity distribution curves at different inflow velocities, the velocity curves in the axial region of show relatively high consistency, while in the region of , it shows a law of gradually increasing with the increase of the inflow velocity. A shape function is established in the form of a piecewise function, and the calculation formula is as follows: ； In the above formula, and represent the parameters for calculation, is the radial correction factor, which is used to correct the velocity change during, mainly correcting the deviation caused by the change of radial position and the change of the incoming flow wind speed. The formula is as follows: ； In the above formula, and represent the parameters for calculation, is the thrust coefficient.

7. The calculation method of an analytical model for accelerating the flow of the tip clearance of a fan according to claim 6, wherein: Calculating the three-dimensional shape function During the process, a way to select a calculation parameter is as follows: , , , .

8. The calculation method of an analytical model for accelerating the flow of the tip clearance of a fan according to claim 1, characterized in that: In Step 7, to superimpose the results calculated for all wind turbines, a specific implementation method is to use linear superposition, and linearly superimpose the calculation results of different wind turbines according to the regions.

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