A technical design method capable of improving fan blade wind driving efficiency

Abstract

The application discloses a technical design method capable of improving fan blade wind driving efficiency, and belongs to the technical field of fan blade design. The method comprises the following steps: obtaining a current blade parameter set of a fan blade, which comprises a blade leading edge windward area value, a blade trailing edge outflow angle value, a blade surface roughness value and a blade mass distribution value; constructing a flow field segmentation mapping relationship of the fan blade in a rotating state, dividing the fan blade radially into a low-speed section, a transition section and a high-speed section and correlating an airflow inertia coefficient; generating an airflow residence point coordinate sequence of multiple arc segment positions of the fan blade surface according to the airflow inertia coefficients of the low-speed section and the high-speed section; determining a friction resistance deviation direction and adjusting the blade trailing edge outflow angle value to form a corrected outflow angle distribution; and coupling the outflow angle distribution with the blade mass distribution value to calculate a driving torque transmission coefficient of each arc segment. The method can adjust the blade trailing edge outflow angle and optimize arc segment driving torque distribution in a targeted manner, and improve the aerodynamic performance of the fan blade.

Description

Technical Field

[0001] This invention relates to the field of fan blade design technology, specifically a technical design method that can improve the wind-driving efficiency of fan blades. Background Technology

[0002] The wind-driving efficiency of fan blades directly affects the overall energy consumption and airflow delivery capacity of the fan. During blade rotation, the airflow velocity varies significantly at different radial positions on the blade surface, and the flow field experienced by the blade root and tip is fundamentally different. Existing fan blade design methods typically optimize the blade as a uniform aerodynamic profile along the radial direction, using a uniform distribution of the windward and outward angles, without fully considering the impact of segmented radial flow field characteristics on airflow adhesion and detachment behavior. This monolithic design makes it difficult for different sections of the blade to simultaneously achieve optimal airflow operating conditions. Areas on the blade surface are prone to premature airflow separation or abnormally increased frictional resistance, limiting the improvement of overall blade wind-driving efficiency. Simultaneously, the lack of coordination between the blade's mass distribution and aerodynamic load distribution results in an uneven contribution of driving torque generated by different segments of the blade during rotation. Some segments bear excessive loads while others fail to fully utilize their wind-driving capacity, leading to impaired torque transmission efficiency. To address the above issues, it is necessary to solve the problems of how to quantify the airflow retention characteristics on the blade surface based on the radial flow field differences in current fan blade designs, and to adjust the outlet angle in a targeted manner to balance the distribution of frictional resistance, as well as how to couple the blade mass distribution with the local outlet angle to analyze the differences in torque contribution of each arc segment, thereby identifying the arc segment positions where aerodynamic loads need to be strengthened or weakened. Summary of the Invention

[0003] This invention provides a technical design method to improve the wind-driving efficiency of fan blades, aiming to solve the problems in the prior art that do not consider the segmented characteristics of the radial flow field of the fan blades, resulting in uneven distribution of frictional resistance and impaired transmission efficiency of driving torque.

[0004] To achieve the above objectives, the present invention provides the following technical solution: The present invention provides a technical design method for improving the wind-driving efficiency of fan blades, the method comprising: acquiring a current blade shape parameter set, the current blade shape parameter set including the leading edge windward area value, the trailing edge airflow angle value, the blade surface roughness value, and the blade mass distribution value; constructing a segmented flow field mapping relationship of the fan blade in a rotating state based on the current blade shape parameter set, the segmented flow field mapping relationship dividing the fan blade radially into a low-speed section, a transition section, and a high-speed section, and associating the airflow inertia coefficient corresponding to each section respectively; and based on the airflow inertia coefficient of the low-speed section and the airflow in the high-speed section... The inertia coefficient is used to generate a sequence of airflow dwell point coordinates for multiple arc segments on the blade surface. Based on the coordinate sequences of each airflow dwell point, the direction of frictional resistance deviation for the corresponding arc segment on the blade surface is determined. The direction of frictional resistance deviation is used to adjust the trailing edge airflow angle value of the blade, forming a corrected airflow angle distribution. The corrected airflow angle distribution is coupled with the blade mass distribution value to calculate the driving torque transmission coefficient for each arc segment. The arc segment with the highest driving torque transmission coefficient is selected as the main driving arc segment, and the arc segment with the lowest driving torque transmission coefficient is selected as the auxiliary driving arc segment. The blade profile revision scheme is then output. This method establishes a segmented flow field mapping to make the radial airflow inertial differences of the fan blades explicit, and locates the airflow residence point accordingly, thereby achieving a precise characterization of the blade surface friction resistance distribution. Then, the trailing edge outlet angle is adjusted in a targeted manner to suppress airflow separation. At the same time, aerodynamic correction and mass distribution are coupled to evaluate torque transmission efficiency, thereby accurately identifying the arc region that contributes the most to the wind drive efficiency, achieving the effect of improving the overall wind drive efficiency without significantly increasing the fan blade mass or complexity.

[0005] As a preferred embodiment of the present invention, the acquisition of the current blade profile parameter set includes: using a contact profilometer to collect the upper and lower surface profiles of the blade cross-section from the blade root to the blade tip along the radial direction of the blade at a preset radial interval; performing a closing process on the upper and lower surface profiles to generate closed cross-sectional profiles at each radial position; calculating the coordinates of the blade leading edge and trailing edge points based on the closed cross-sectional profiles; and then calculating the blade chord length at each radial position. The blade chord lengths at each radial position are then integrated into a chord length radial distribution curve, which is used as a component of the current blade profile parameter set. In this way, the chord length distribution curve constructed from the measured profiles accurately reflects the geometric characteristics of the blade, providing a high-precision data foundation for subsequent flow field segmentation.

[0006] As a further preferred embodiment of the present invention, the construction of the flow field segmentation mapping relationship of the fan blade in the rotating state includes: extracting the abrupt change position of the chord length change rate as a segment boundary marker based on the radial distribution curve of the chord length; dividing the fan blade radially into the low-speed segment, the transition segment, and the high-speed segment using the segment boundary marker as the boundary; calculating the average chord length in each segment; and substituting each average chord length into a preset airflow inertia coefficient mapping table to obtain the corresponding airflow inertia coefficient for each segment. By dividing the segment by the abrupt change position of the chord length change rate, the radial position where the airflow inertia changes significantly can be captured based on the natural transition characteristics of the blade shape, making the flow field segmentation mapping result more consistent with the actual airflow behavior in the rotating state.

[0007] In another preferred embodiment of the present invention, generating a sequence of airflow dwell point coordinates for multiple arc segments on the blade surface includes: comparing the airflow inertia coefficient of the low-speed segment with that of the high-speed segment to obtain a segment inertia difference factor; determining the number of dwell points along the arc length direction of the blade surface based on this difference factor; starting from the leading edge of the blade, equidistantly arranging initial dwell point positions along the arc length direction according to the number of dwell points; for each initial dwell point position, extracting the local radius of curvature of the blade cross section at that location, and performing offset correction on the initial dwell point position based on the local radius of curvature to obtain a sequence of coordinates for each airflow dwell point. The dwell point positions, combined with local curvature correction, can more accurately mark the actual adhesion boundaries of the airflow in different arc segments, providing a reliable basis for frictional resistance deviation analysis.

[0008] In this invention, the process of forming the corrected air outlet angle distribution includes: calculating the angle between the normal direction and the rotational tangential direction of each airflow dwell point; comparing the angle with a preset standard angle; marking dwell points with angles greater than the preset standard angle as high-friction dwell points and marking dwell points with angles less than or equal to the preset standard angle as low-friction dwell points; connecting adjacent high-friction dwell points to form a high-friction arc segment and connecting adjacent low-friction dwell points to form a low-friction arc segment; based on the projection position of the high-friction arc segment on the trailing edge of the blade, decreasing the air outlet angle value of the corresponding area on the trailing edge of the blade by one adjustment step; and based on the projection position of the low-friction arc segment on the trailing edge of the blade, increasing the air outlet angle value of the corresponding area on the trailing edge of the blade by one adjustment step, thereby forming the corrected air outlet angle distribution. By using the geometric relationship between the normal and tangential directions at the dwell point to determine the direction of frictional resistance deviation, it is possible to directly correlate the influence of the local blade morphology on airflow deflection. By adjusting the trailing edge outlet angle in segments, the airflow accumulation in the high friction zone and the premature separation in the low friction zone can be effectively reduced, thus homogenizing the trailing edge outlet flow.

[0009] Furthermore, the coupling calculation of the driving torque transmission coefficient for each arc segment by the modified air outlet angle distribution and the blade mass distribution value includes: decomposing the modified air outlet angle distribution according to the arc segment position to obtain the local air outlet angle corresponding to each arc segment, and obtaining the local mass value corresponding to each arc segment obtained by integrating the blade mass distribution value on the corresponding arc segment; taking the arc segment as a unit, determining the basic torque value of the arc segment by multiplying the sine value of the local air outlet angle of each arc segment with the local mass value, and then dividing the basic torque value of each arc segment by the sum of the basic torque values ​​of all arc segments to obtain the driving torque transmission coefficient of each arc segment. This coupling method quantifies the aerodynamic correction effect and the blade's own mass distribution into a unified torque transmission contribution, avoiding the one-sidedness of judging the arc segment contribution solely by aerodynamics or solely by mass, and making the division of the main driving area and the auxiliary driving area more accurate.

[0010] Preferably, the output fan blade shape revision scheme includes: extracting the first leading edge radius and the first trailing edge radius of the blade cross-section of the main drive arc segment as the target, and extracting the second leading edge radius and the second trailing edge radius of the blade cross-section of the auxiliary drive arc segment as the target; calculating the leading edge radius difference between the first and second leading edge radii, and the trailing edge radius difference between the first and second trailing edge radii; and generating leading edge thickening and trailing edge thinning commands at the main drive arc segment, and leading edge thinning and trailing edge thickening commands at the auxiliary drive arc segment, respectively, based on the leading edge radius difference and trailing edge radius difference. By directionally transferring the mass from the auxiliary drive arc segment with lower torque contribution to the main drive arc segment with higher torque contribution, the concentration of driving torque is increased without changing the overall fan blade mass, thereby further improving wind driving efficiency.

[0011] Regarding offset correction, the process of offset correction for the initial dwell point position is as follows: Calculate the ratio of the local radius of curvature of the blade section to the reference radius of curvature at each initial dwell point position; multiply the ratio by a preset offset coefficient to obtain the offset correction amount; move the initial dwell point position along the blade surface normal direction according to the offset correction amount, thereby adapting the dwell point position to the boundary layer development differences caused by changes in blade surface curvature. Regarding the determination of the frictional drag deviation direction, at each airflow dwell point, the difference between the angle between the normal direction and the rotational tangential direction and a preset standard angle is used as a direction determination factor. When the direction determination factor is positive, the frictional drag deviation direction points towards the trailing edge of the blade; when the direction determination factor is negative, the frictional drag deviation direction points towards the leading edge, thus achieving quantitative judgment of the deviation direction. For the value of the adjustment step, the arc length and width of the high-friction arc segment and the low-friction arc segment on the trailing edge of the blade are obtained. The arc length and width are multiplied by the preset angle change benchmark value and then divided by the total arc length and width of the entire trailing edge of the blade to obtain the adjustment step, so that the air outlet angle adjustment amount is related to the arc segment range, avoiding local over-adjustment that may cause new airflow disturbance.

[0012] Furthermore, the present invention also includes a fan blade structure that can improve the wind-driving efficiency of the fan blade, which is implemented by the above-mentioned technical design method for improving the wind-driving efficiency of the fan blade. The structure is characterized by including a blade body, wherein the blade body is provided with a low-speed section, a transition section and a high-speed section in sequence along the radial direction. The blade body has a leading edge and a trailing edge. The trailing edge of the blade is provided with a plurality of spaced arc-shaped tooth structures along the radial direction of the blade body. An arc-shaped notch is formed between adjacent arc-shaped tooth structures. The plurality of arc-shaped tooth structures extend from the low-speed section of the blade body to the high-speed section, and the extension direction of the arc-shaped tooth structures intersects with the rotation direction of the blade body, so that the trailing edge of the blade forms a trailing edge contour structure that varies in the radial direction.

[0013] The technical effects and advantages provided by the present invention in the above technical solution are as follows: This approach generates a sequence of airflow dwell point coordinates across multiple arc segments of the fan blade surface based on the airflow inertia coefficients of the low-speed and high-speed sections. The trailing edge airflow angle distribution is then adjusted based on the frictional resistance deviation direction at each dwell point. Unlike traditional uniform airflow angle designs, this method directly maps the radial airflow inertia differences to discrete dwell points on the blade surface. The angle between the normal direction and the rotational tangential direction at each dwell point distinguishes between high-friction and low-friction arc segments. For high-friction arc segments, the corresponding trailing edge airflow angle is reduced to alter the airflow's detachment direction at the trailing edge, alleviating the concentration of frictional resistance in that segment. For low-friction arc segments, the corresponding trailing edge airflow angle is increased to moderately enhance the airflow's work-doping capacity. This results in a non-uniform airflow angle distribution at the blade's trailing edge, allowing the entire fan blade to match local flow field characteristics at different radial positions. This reduces energy dissipation caused by local frictional resistance deviations, improves the persistence of airflow adhesion along the blade surface and the consistency of the airflow direction, and enhances the overall aerodynamic performance of the blade. By coupling the corrected outlet angle distribution with the blade mass distribution value, the driving torque transmission coefficient of each arc segment is calculated, and the main drive arc segment and auxiliary drive arc segment are selected according to the driving torque transmission coefficient to output the blade shape revision scheme. This scheme introduces a joint analysis of mass distribution and local aerodynamic angle in the blade design. The product of the sine value of the local outlet angle of the arc segment and the local mass value is used to represent the basic torque value, and the driving torque transmission coefficient ranking result is obtained after normalization. The arc segment with the highest driving torque transmission coefficient is revised as the main drive arc segment, and the leading edge is thickened and the trailing edge is thinned at its cross-section to enhance the aerodynamic load. The arc segment with the lowest driving torque transmission coefficient is revised as the auxiliary drive arc segment, and the leading edge is thinned and the trailing edge is thickened at its cross-section to reduce the aerodynamic load. By revising the blade shape, the material distribution is concentrated in the arc segment with a prominent driving torque contribution, and the material redundancy in the arc segment with a weak driving torque contribution is reduced. This makes the blade mass distribution and aerodynamic load distribution more coordinated, reduces the energy loss caused by uneven torque transmission during blade rotation, and improves the overall blade wind drive efficiency. Attached Figure Description

[0014] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this invention. For those skilled in the art, other drawings can be obtained based on these drawings.

[0015] Figure 1 This is a flowchart of the technical design method for improving the wind drive efficiency of fan blades; Figure 2 This is a flowchart of the method for generating a sequence of airflow residence point coordinates; Figure 3 It is a mapping diagram of the radial chord length distribution of the fan blades, the flow field segmentation, and the airflow inertia coefficient; Figure 4 It is a diagram showing the outline of the suction surface of the fan blade, the location of the airflow residence point, and the distribution of local radii of curvature. Figure 5 It is a diagram showing the distribution of airflow residence points and air outlet angles on the fan blade surface, as well as the division of friction arc segments; Figure 6 It is a curve comparing the original and revised values ​​of the leading and trailing edge radii of the main drive arc segment and the auxiliary drive arc segment of the fan blade; Figure 7 This is a diagram of the toothed structure at the trailing edge of the fan blade; Figure 8 This is a schematic diagram of the partitioned structure at the trailing edge of the fan blade. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0017] See Figure 1 This invention provides a technical design method to improve the wind-driving efficiency of fan blades. The method includes: acquiring a current set of blade shape parameters, wherein the current set of blade shape parameters includes the leading edge windward area value, the trailing edge airflow angle value, the blade surface roughness value, and the blade mass distribution value; constructing a segmented flow field mapping relationship for the fan blade in a rotating state based on the current set of blade shape parameters, wherein the segmented flow field mapping relationship is used to divide the fan blade radially into a low-speed segment, a transition segment, and a high-speed segment, and associates each segment with its corresponding airflow inertia coefficient; and based on the airflow inertia coefficients of the low-speed segment and the high-speed segment in the segmented flow field mapping relationship... The process involves generating a sequence of airflow stagnation point coordinates for multiple arc segments on the blade surface; determining the frictional resistance deviation direction for the corresponding arc segment on the blade surface based on the airflow stagnation point coordinate sequence; adjusting the trailing edge airflow angle value of the blade using the frictional resistance deviation direction to form a corrected airflow angle distribution; coupling the corrected airflow angle distribution with the blade mass distribution value to calculate the driving torque transmission coefficient for each arc segment; sorting the driving torque transmission coefficients from high to low, selecting the arc segment with the highest driving torque transmission coefficient as the main driving arc segment, and selecting the arc segment with the lowest driving torque transmission coefficient as the auxiliary driving arc segment, and outputting the blade profile revision scheme.

[0018] In practice, the current blade profile parameter set is acquired, which includes the leading edge windward area, trailing edge airflow angle, surface roughness, and mass distribution of the blade. A contact profilometer is used to collect the upper and lower surface profiles of the blade cross-section at preset radial intervals, from the blade root to the blade tip. The preset radial interval is set according to the spanwise length of the blade and the required accuracy. One possible setting method is to divide the total spanwise length of the blade into 20 to 50 equal intervals, with the length of each interval being the preset radial interval. The probe of the contact profilometer moves against the blade surface with a constant contact force, recording the coordinate sequence of the probe in the direction perpendicular to the plane of rotation and along the chord direction, thus obtaining the upper and lower surface profiles.

[0019] The acquired upper and lower surface contour lines are closed to generate a closed cross-sectional contour at each radial position. The closure is achieved by connecting the starting points of the upper and lower surface contour lines with straight line segments, and connecting the ending points of the upper and lower surface contour lines with straight line segments, forming a closed curve. This closed curve is the closed cross-sectional contour. The plane containing the closed cross-sectional contour is perpendicular to the radial axis of the fan blade.

[0020] Calculate the leading and trailing edge coordinates of the blade at each radial position based on the closed cross-sectional profile. Determine the blade's rotation direction, which is the direction of the tangent to the circle the blade rotates around its axis of rotation during operation. Among all coordinate points on the closed cross-sectional profile, determine the point furthest along the rotation direction as the leading edge coordinate, and the point furthest along the rotation direction as the trailing edge coordinate. Both the leading and trailing edge coordinates are recorded in three-dimensional spatial coordinates.

[0021] Based on the coordinates of the leading and trailing edges of the blade at each radial position, the chord length of the blade at each radial position is calculated. The chord length is calculated by determining the Euclidean distance between the coordinates of the leading and trailing edges; this Euclidean distance is the chord length at that radial position. Using the chord length at each radial position as the dependent variable and the span from the blade root at each radial position as the independent variable, a radial distribution curve of chord length is formed. This curve, with span as the horizontal axis and chord length as the vertical axis, illustrates the variation of the chord length from the blade root to the blade tip. The radial distribution curve of chord length is a component of the current blade shape parameter set.

[0022] Based on the current blade profile parameter set, a piecewise mapping relationship of the flow field under rotational conditions is constructed for the fan blade. The locations of abrupt changes in the chord length rate of change are extracted based on the radial distribution curve of the chord length. The chord length rate of change is obtained by calculating the first derivative of the radial distribution curve of the chord length, which is then calculated point-by-point using the central difference method. The calculation span of the central difference method is... The formula for the rate of change of the chord length at point is:

[0023] in, Indicates the span is Rate of change of chord length at point Indicates the span is The length of the blade chord at that point, Indicates the span is The length of the blade chord at that point, The radial span sampling interval. The value is the difference between the span values ​​of two adjacent radial positions, which is determined by the preset radial spacing during the step of obtaining the current blade shape parameter set. After calculating the distribution of the chord length change rate along the span, the second-order difference quotient is obtained. The span positions where the absolute value of the second-order difference quotient exceeds the preset abrupt change threshold are marked as abrupt change positions of the chord length change rate. The preset abrupt change threshold is set according to the magnitude and variation characteristics of the blade chord length; a typical setting is one-third of the maximum change amplitude of the chord length change rate between adjacent span intervals.

[0024] The extracted locations of abrupt changes in chord length change rate are used as segment boundary markers. Two segment boundary markers are used, designated as the first segment boundary marker and the second segment boundary marker, with the first segment boundary marker being closer to the leaf root than the second segment boundary marker. Using these segment boundary markers as boundaries, the fan blade is radially divided into a low-speed segment, a transition segment, and a high-speed segment. The radial range from the leaf root to the first segment boundary marker is designated as the low-speed segment; the radial range from the first segment boundary marker to the second segment boundary marker is designated as the transition segment; and the radial range from the second segment boundary marker to the leaf tip is designated as the high-speed segment.

[0025] Calculate the average chord length in the low-speed, transition, and high-speed sections respectively. The average chord length in the low-speed section is the arithmetic mean of the blade chord lengths corresponding to all radial positions within the low-speed section. The average chord length in the transition section is the arithmetic mean of the blade chord lengths corresponding to all radial positions within the transition section. The average chord length in the high-speed section is the arithmetic mean of the blade chord lengths corresponding to all radial positions within the high-speed section.

[0026] The average chord length of the low-speed section is substituted into a pre-defined airflow inertia coefficient mapping table to obtain the corresponding airflow inertia coefficient. The average chord length of the transition section is substituted into the same table to obtain the corresponding airflow inertia coefficient. Similarly, the average chord length of the high-speed section is substituted into the same table to obtain the corresponding airflow inertia coefficient. The pre-defined airflow inertia coefficient mapping table is a set of discrete data tables, pre-obtained through numerical simulations or experimental calibrations of fan blades with different average chord lengths in a rotating flow field. This table stores a one-to-one correspondence between average chord length values ​​and airflow inertia coefficient values. During the table lookup process, if the average chord length value of the low-speed section does not directly fall into a node of the discrete data table, linear interpolation is used to obtain the corresponding airflow inertia coefficient; the same applies to the transition and high-speed sections. After completing the association of the airflow inertia coefficients, the segmented mapping relationship of the flow field is constructed.

[0027] See Figure 3 In the figure, the horizontal axis represents the normalized radial span, the left side of the vertical axis represents the blade chord length (in meters), and the right side represents the airflow inertia coefficient. The blue solid curve represents the variation trend of the blade chord length along the radial span. The curve generally shows a fluctuating pattern of first rising and then falling. The chord length at the starting point is about 0.15 meters, reaching a maximum of about 0.5 meters at about 0.5 normalized radial spans, and then gradually decreasing to about 0.05 meters at the blade tip. The two gray dashed lines in the figure mark the locations of abrupt changes in the chord length change rate, located at about 0.33 and 0.68 normalized radial spans, respectively, dividing the blade radial segment into three sections: the light blue area on the left corresponds to the low-speed section, the light green area in the middle corresponds to the transition section, and the light red area on the right corresponds to the high-speed section.

[0028] The orange diamonds in the figure represent the airflow inertia coefficients for the corresponding sections, with their values ​​corresponding to the scale on the right-hand vertical axis. The airflow inertia coefficient in the low-speed section is approximately 0.60, the inertia coefficient in the transition section is approximately 0.65 (the highest value), and the inertia coefficient in the high-speed section decreases to approximately 0.51.

[0029] In specific implementation, please refer to Figure 2 When generating the coordinate sequence of airflow residence points at multiple arc segments on the fan blade surface, the airflow inertia coefficients of the low-speed and high-speed segments, already associated in the flow field segmentation mapping relationship, are used. The ratio of the airflow inertia coefficients of the low-speed and high-speed segments is calculated to obtain the segment inertia difference factor. The value of the segment inertia difference factor is equal to the quotient obtained by dividing the airflow inertia coefficient of the low-speed segment by the airflow inertia coefficient of the high-speed segment.

[0030] The number of dwelling points along the blade arc length is determined based on the segment inertia difference factor. The segment inertia difference factor is multiplied by a preset dwelling point density factor, and the product is rounded up to obtain an integer value, which is used as the number of dwelling points. The preset dwelling point density factor is related to the blade spanwise length and the spatial resolution requirements of the flow field analysis, and its value ranges from 10 to 30. If the segment inertia difference factor is large, it indicates a significant difference in airflow inertia between the low-speed and high-speed segments, requiring more dwelling points along the blade arc length to capture changes in airflow state, thus increasing the number of dwelling points accordingly. If the segment inertia difference factor is close to 1, it indicates that the airflow inertia between the low-speed and high-speed segments is similar, and the number of dwelling points tends towards the preset dwelling point density factor value.

[0031] Starting from the leading edge of the blade, initial dwell point positions are evenly spaced along the arc length direction of the blade surface according to the number of dwell points. The arc length direction of the blade surface refers to the path direction extending from the leading edge of the blade along the arc of the suction or pressure surface to the trailing edge of the blade. A representative blade section located at the boundary between the low-speed section and the transition section in the radial position of the blade is selected, and the suction surface contour line of this representative blade section is extracted. The total arc length of the suction surface contour line from the leading edge to the trailing edge of the blade is calculated. The total arc length of the curve is divided by the difference between the number of dwell points and one to calculate the arc length interval between adjacent initial dwell points. On the suction surface contour line, the coordinates of the leading edge of the blade are used as the first initial dwell point position. Then, a new initial dwell point position is determined for each additional arc length interval along the arc length direction until the trailing edge of the blade is covered, completing the layout of all initial dwell point positions.

[0032] For each initial dwell point location, the local radius of curvature of the blade cross-section at that location is extracted. The extraction method is as follows: on the closed cross-sectional profile, select three points with the initial dwell point as the midpoint, and one adjacent point before and after the initial dwell point along the arc length. The radius of an arc is determined by these three points, and this arc radius is used as the local radius of curvature for that initial dwell point location. If an initial dwell point is located near the leading or trailing edge of the blade, and it is not possible to obtain adjacent points before and after it, the local radius of curvature is calculated using the arc formed by the initial dwell point and the two nearest points on the same side along the arc length.

[0033] Obtain the reference radius of curvature. The reference radius of curvature is obtained by calculating the arithmetic mean of the local radii of curvature corresponding to all initial dwell point positions, and using the calculated arithmetic mean as the reference radius of curvature.

[0034] The initial dwell point positions are offset and corrected based on the local radius of curvature to obtain the airflow dwell point coordinate sequence. The offset correction process includes: calculating the ratio of the local radius of curvature of the blade section at each initial dwell point position to the reference radius of curvature, and multiplying this ratio by a preset offset coefficient to obtain the offset correction amount. The preset offset coefficient is pre-calibrated based on the interaction between the blade surface material properties and the inertial effect of the flow field. The preset offset coefficient ranges from 0.1 to 0.3. The calibration process is based on a standard fan blade model, using the airflow boundary layer separation point position obtained from numerical simulation as a reference, and adjusting the preset offset coefficient to minimize the standard deviation between the offset-corrected airflow dwell point position and the separation point position. The calibration results are stored in a parameter table for later use. The formula for calculating the offset correction amount is expressed as:

[0035] in, This indicates the offset correction amount, in millimeters. This indicates the preset offset coefficient, in millimeters; The local radius of curvature at the initial residence point is expressed in millimeters. This represents the reference radius of curvature, in millimeters.

[0036] After calculating the offset correction, the initial dwelling point is moved a distance equal to the offset correction along the normal direction of the blade surface where the initial dwelling point is located, with the movement direction pointing outwards from the blade surface. The resulting three-dimensional spatial coordinates constitute the airflow dwelling point coordinates corresponding to the initial dwelling point position. All airflow dwelling point coordinates are arranged in order of arc length from the leading edge to the trailing edge to generate an airflow dwelling point coordinate sequence.

[0037] See Figure 4 In the figure, the horizontal axis represents the arc length position on the blade suction surface profile, in millimeters, ranging from 0 to 100 millimeters; the left vertical axis represents the normal offset of the suction surface profile, in millimeters; and the right vertical axis represents the local radius of curvature, in millimeters. The blue solid curve represents the trend of the normal offset of the blade suction surface profile, showing that the micro-geometry of the blade suction surface profile fluctuates along the arc length direction, reaching two obvious peaks at approximately 20 mm and 80 mm. The peak normal offset of the suction surface profile is approximately 0.025 mm to 0.028 mm, reflecting the local convex characteristics of the blade suction surface. The purple dashed curve represents the distribution of the local radius of curvature of the blade suction surface. The local radius of curvature shows two peak areas on the entire arc length curve, concentrated in the ranges of approximately 15 to 25 mm and 65 to 80 mm, respectively. The maximum peak radius of curvature is approximately 13 mm, and the local radius of curvature corresponds to the peak and valley positions of the suction surface profile normal offset curve, indicating that the curvature change of the blade shape has a significant impact on the profile morphology.

[0038] The initial dwell point positions, marked with red squares in the figure, are evenly distributed along the arc length direction, with a total of multiple sampling points covering the entire suction surface contour of the blade. The green dots represent the coordinates of the airflow dwell point obtained after local curvature radius offset correction. Compared to the initial dwell point, the airflow dwell point shows a significant offset along the normal direction in the peak region. The degree of offset is related to the local curvature radius at the corresponding position, reflecting the technical feature of offset correction of the dwell point based on the local curvature radius and preset offset coefficient in this embodiment.

[0039] In practice, the process of forming the corrected air outlet angle distribution starts with the coordinate sequence of airflow stagnation points. In the three-dimensional model of the blade, each airflow stagnation point has a definite spatial coordinate position. For each airflow stagnation point in the coordinate sequence, the normal direction is calculated. The normal direction is calculated as follows: on the blade cross-sectional profile where the airflow stagnation point is located, extract one adjacent airflow stagnation point before and after the airflow stagnation point along the arc length direction. Construct a chord vector through the two adjacent airflow stagnation points, rotate the chord vector by 90 degrees and normalize it to obtain the normal direction of the airflow stagnation point. The normal direction points outward from the blade surface.

[0040] Obtain the rotational tangential direction, which is the direction of the circumferential velocity at the location of the airflow stagnation point when the fan blade rotates around the rotation axis. The rotational tangential direction is perpendicular to the radial plane formed by the airflow stagnation point and the rotation axis. Calculate the angle between the normal direction and the rotational tangential direction at the airflow stagnation point. The calculation process is as follows: calculate the dot product of the normal direction vector and the rotational tangential direction vector, divide the dot product by the product of the magnitudes of the normal direction vector and the rotational tangential direction vector, and perform an inverse cosine operation on the quotient. The result is the angle between the normal direction and the rotational tangential direction, in degrees.

[0041] The included angle at each airflow stagnation point is compared with a preset standard angle. The preset standard angle ranges from 85 to 90 degrees, and this range is predetermined based on the angular relationship between the ideal airflow direction and the normal direction of the blade surface in the rotating flow field of the fan blade. When comparing angles, if the included angle is greater than the preset standard angle, the airflow stagnation point is marked as a high-friction stagnation point; if the included angle is less than or equal to the preset standard angle, the airflow stagnation point is marked as a low-friction stagnation point.

[0042] Within the same arc segment region, adjacent airflow residence points that are both high-friction residence points are connected sequentially to form a continuous arc segment, which is marked as a high-friction arc segment. Similarly, adjacent airflow residence points that are both low-friction residence points are connected sequentially to form a continuous arc segment, which is marked as a low-friction arc segment. The connection method uses cubic spline curve interpolation, with the interpolation nodes being the spatial coordinates of the corresponding category of airflow residence points, resulting in a smooth arc segment curve.

[0043] The determination of the direction of frictional drag deviation is carried out simultaneously with the determination of high-friction and low-friction residence points. At each airflow residence point, the included angle is subtracted from the preset standard angle, and the difference is used as the direction determination factor. When the direction determination factor is positive, the direction of frictional drag deviation points towards the trailing edge of the blade; when the direction determination factor is negative, the direction of frictional drag deviation points towards the leading edge of the blade.

[0044] The projection position of the high-friction arc segment on the trailing edge of the blade is determined. This projection position is obtained by projecting the coordinates of the airflow stagnation points on the high-friction arc segment onto the trailing edge profile of the blade along the airflow direction. The trailing edge profile is formed by connecting the coordinates of the trailing edge points at various radial positions. Based on the radial interval of the blade corresponding to the projection position of the high-friction arc segment on the trailing edge, the current trailing edge outlet angle value is obtained at multiple radial sampling points within the interval corresponding to the projection position on the trailing edge. This value is then reduced by one adjustment step to obtain a decreased outlet angle value. Similarly, the projection position of the low-friction arc segment on the trailing edge is determined. The current trailing edge outlet angle value is obtained at multiple radial sampling points within the interval corresponding to the projection position on the trailing edge. This value is then increased by one adjustment step to obtain an increased outlet angle value. Finally, the outlet angle values ​​at all radial sampling points, after reduction or increase processing, are integrated and used to replace the original trailing edge outlet angle value, resulting in a corrected outlet angle distribution.

[0045] The adjustment step size is determined as follows: The arc length and width of the high-friction arc segment on the trailing edge of the blade are obtained. The arc length and width are calculated by measuring the curve length corresponding to the projected position of the high-friction arc segment along the trailing edge contour line of the blade. If the object being processed is a low-friction arc segment, the arc length and width of the low-friction arc segment on the trailing edge of the blade are obtained. The total arc length and width of the entire trailing edge of the blade are obtained, which is the complete curve length of the trailing edge contour line from the blade root to the blade tip. The arc length and width are multiplied by a preset angle change benchmark value, and the product is divided by the total arc length and width of the entire trailing edge of the blade to calculate the adjustment step size. The preset angle change benchmark value ranges from 0.5 degrees to 2 degrees, and this range is preset based on engineering experience in adjusting the trailing edge angle of the fan blade and the fan blade size level. The adjustment step size is calculated using the following formula:

[0046] in, This indicates the adjustment step size, in degrees; This indicates the arc length and width of the high-friction arc segment on the trailing edge of the blade, or the arc length and width of the low-friction arc segment on the trailing edge of the blade, in millimeters. This represents the preset angle change baseline value, in degrees. This represents the total arc length and width of the entire trailing edge of the blade, in millimeters. When dealing with high-friction arc segments... The value is determined by the arc length and width of the high-friction arc segment on the trailing edge of the blade; when dealing with the low-friction arc segment... The value is the arc length and width of the low-friction arc segment on the trailing edge of the blade.

[0047] See Figure 5 In the figure, the horizontal axis represents the radial span of the fan blades, which has been normalized and ranges from 0 to 1. The vertical axis represents the outlet angle value, in degrees. The blue solid curve in the figure represents the outlet angle distribution at the current blade trailing edge, and the red dashed curve represents the corrected outlet angle distribution calculated and adjusted based on the airflow residence point coordinate sequence in this embodiment. In the legend, the light orange area marks the high-friction arc segment, and the light blue area marks the low-friction arc segment.

[0048] As shown in the figure, the outlet angle value generally shows a trend of first increasing and then decreasing. In the light orange high-friction arc segment regions with radial spans of approximately 0.35 to 0.48 and 0.65 to 0.75, the current outlet angle value fluctuates significantly and remains at a relatively high level. The corrected outlet angle distribution is slightly lower than the current value, as indicated by the red dashed line deviating from the blue solid line and adjusting downwards in this region, consistent with the step of reducing the outlet angle value of the high-friction arc segment in this embodiment. In the light blue low-friction arc segment regions, located in the radial spans of approximately 0.15 to 0.25 and 0.82 to 0.92 respectively, the current outlet angle value is relatively low and relatively flat. The corrected outlet angle distribution in this region shows a slight increase compared to the current value, with the red dashed line slightly higher than the blue solid line, reflecting the adjustment to increase the outlet angle value of the low-friction arc segment.

[0049] The overall corrected air outlet angle distribution curve closely matches the current air outlet angle value, and the adjustment range is limited. This indicates that the correction of the air outlet angle is based on reasonable fine-tuning of the direction of frictional resistance deviation at the airflow residence point, ensuring the continuity and smoothness of the airflow outlet angle at the trailing edge of the blade along the radial direction.

[0050] In practice, the corrected outlet angle distribution is coupled with the blade mass distribution value to calculate the driving torque transmission coefficient for each arc segment. The fan blade arc segments have already been divided in previous steps based on the direction of frictional resistance deviation, including high-friction and low-friction arc segments. The corrected outlet angle distribution is a set of outlet angle values ​​at multiple radial sampling points corresponding to the projection positions of each arc segment on the trailing edge of the blade. The corrected outlet angle distribution is decomposed according to the arc segment positions to obtain the local outlet angle corresponding to each arc segment. The decomposition process is as follows: traverse each divided high-friction and low-friction arc segment, determine the projection interval of that arc segment on the trailing edge of the blade, extract the outlet angle values ​​at all radial sampling points within that projection interval; calculate the arithmetic mean of these outlet angle values, and use the arithmetic mean as the local outlet angle corresponding to that arc segment.

[0051] The local mass value corresponding to each arc segment is obtained by integrating the blade mass distribution value over the corresponding arc segment. The blade mass distribution value is a function of the mass density per unit area in the spanwise and chordwise directions of the blade. This function uses the spanwise span and chordwise arc length percentages as independent variables, and its value is obtained by fitting the mass attributes of each surface element extracted from the finite element mesh of the 3D model of the blade. For each arc segment, a closed arc segment region is formed on the suction or pressure surface of the blade, bounded by the boundary curve of the arc segment and the leading and trailing edges of the blade. The blade mass distribution value is double-integrated within this arc segment region, with the integration variables being the spanwise span variable and the chordwise arc length variable, respectively. The integration result is the local mass value of that arc segment. On an arc segment basis, the sine value of the local air outlet angle corresponding to each arc segment is multiplied by the local mass value corresponding to that arc segment, and the product is used as the basic torque value of that arc segment. The calculation of the basic torque value is performed separately on all high-friction and low-friction arc segments, and each arc segment obtains a basic torque value.

[0052] Add up the basic torque values ​​corresponding to all arc segments to obtain the total basic torque value. For each arc segment, divide its basic torque value by the total basic torque value; the quotient is the driving torque transmission coefficient for that arc segment. The driving torque transmission coefficient represents the proportion of the total driving torque transmitted by that arc segment. The driving torque transmission coefficient is calculated using the following formula:

[0053] in, Indicates the first The driving torque transmission coefficient of each arc segment; Indicates the first The local mass value of each arc segment, in kilograms; Indicates the first The local air outlet angle of each arc segment, in degrees; Indicates the first The sine value of the local air outlet angle of each arc segment; This represents the total number of all high-friction and low-friction arc segments; Indicates the first The local mass value of each arc segment, in kilograms; Indicates the first The local air outlet angle of each arc segment, in degrees; This represents the sum of the basic torque values ​​for all arc segments. The sum of the driving torque transmission coefficients for all arc segments equals 1.

[0054] In practical implementation, when outputting the fan blade profile revision scheme, the driving torque transmission coefficients for all arc segments have already been calculated. The driving torque transmission coefficients are sorted from highest to lowest; these coefficients are dimensionless values ​​obtained in previous steps by comparing the base torque value with the sum of the base torque values. From the sorted results, the arc segment with the highest driving torque transmission coefficient is selected as the primary driving arc segment, and the arc segment with the lowest driving torque transmission coefficient is selected as the secondary driving arc segment.

[0055] Using the main drive arc segment as the target arc segment, extract the first leading edge radius and the first trailing edge radius of the blade cross-section corresponding to the main drive arc segment. The blade cross-section corresponding to the main drive arc segment is determined by a representative radial position within the radial position range of the main drive arc segment, with the radial coordinates at the midpoint of the main drive arc segment selected as the representative radial position. At this representative radial position, obtain the closed cross-sectional profile. On the closed cross-sectional profile, with the blade leading edge point as the center, two auxiliary points are respectively intercepted along the closed cross-sectional profile to the front edge, with an arc length of 2% of the local chord length at the leading edge point. A fitting circle is determined by the blade leading edge point and the two auxiliary points, and the radius of the fitting circle is the first leading edge radius. On the closed cross-sectional profile, with the blade trailing edge point as the center, two auxiliary points are respectively intercepted along the closed cross-sectional profile to the trailing edge, with an arc length of 2% of the local chord length at the trailing edge point. A fitting circle is determined by the blade trailing edge point and the two auxiliary points, and the radius of the fitting circle is the first trailing edge radius.

[0056] Using the auxiliary drive arc segment as the target arc segment, the second leading edge radius and the second trailing edge radius of the blade cross-section corresponding to the auxiliary drive arc segment are extracted. The blade cross-section corresponding to the auxiliary drive arc segment is determined by a representative radial position within the radial position range of the auxiliary drive arc segment, with the radial coordinates at the midpoint of the auxiliary drive arc segment selected as the representative radial position. At this representative radial position, a closed cross-sectional profile is obtained. On the closed cross-sectional profile, with the blade leading edge point as the center, two auxiliary points are respectively intercepted along the closed cross-sectional profile to the front edge, with an arc length equal to 2% of the local chord length at the leading edge point. A fitting circle is determined by the blade leading edge point and the two auxiliary points, and the radius of the fitting circle is the second leading edge radius. On the closed cross-sectional profile, with the blade trailing edge point as the center, two auxiliary points are respectively intercepted along the closed cross-sectional profile to the trailing edge, with an arc length equal to 2% of the local chord length at the trailing edge point. A fitting circle is determined by the blade trailing edge point and the two auxiliary points, and the radius of the fitting circle is the second trailing edge radius.

[0057] The difference between the first and second leading edge radii is calculated by subtracting the second leading edge radius from the first leading edge radius. Similarly, the difference between the first and second trailing edge radii is calculated by subtracting the second trailing edge radius from the first trailing edge radius.

[0058] Based on the differences in leading and trailing radii, leading edge thickening and trailing edge thinning commands are generated for the main drive segment, and leading edge thinning and trailing edge thickening commands are generated for the auxiliary drive segment. The leading edge thickening command increases the leading edge radius of all blades at all radial positions within the radial range of the main drive segment, within the absolute value of the leading edge radius difference. The increase is linearly decreasing with the distance of each radial position from the midpoint of the main drive segment. At the midpoint of the main drive segment, the increase is the absolute value of the leading edge radius difference, and at the boundary of the main drive segment, the increase is zero. The trailing edge thinning command decreases the trailing edge radius of all blades at all radial positions within the radial range of the main drive segment, within the absolute value of the trailing edge radius difference. The decrease is linearly decreasing with the distance of each radial position from the midpoint of the main drive segment. At the midpoint of the main drive segment, the decrease is the absolute value of the trailing edge radius difference, and at the boundary of the main drive segment, the decrease is zero. The leading edge thinning command reduces the leading edge radius of the blades at all radial positions within the radial range of the auxiliary drive arc segment, within the absolute value of the leading edge radius difference. The reduction amount decreases linearly with the distance of each radial position from the midpoint of the auxiliary drive arc segment. At the midpoint of the auxiliary drive arc segment, the reduction amount is the absolute value of the leading edge radius difference, and at the boundary of the auxiliary drive arc segment, the reduction amount is zero. The trailing edge thickening command increases the trailing edge radius of the blades at all radial positions within the radial range of the auxiliary drive arc segment, within the absolute value of the trailing edge radius difference. The increase amount decreases linearly with the distance of each radial position from the midpoint of the auxiliary drive arc segment. At the midpoint of the auxiliary drive arc segment, the increase amount is the absolute value of the trailing edge radius difference, and at the boundary of the auxiliary drive arc segment, the increase amount is zero.

[0059] The fan blade shape revision scheme includes leading edge thickening instructions, trailing edge thinning instructions, and trailing edge thickening instructions. The fan blade shape revision scheme is output in a structured data format, including the instruction type, the radial range of the instruction's effect, and the leading and trailing edge radius adjustments at each radial position. The output results can be directly read and executed by fan blade 3D model reconstruction or CNC machining centers.

[0060] See Figure 6 In the figure, the horizontal axis represents the normalized value of the radial span of the fan blade, ranging from 0 to 1, indicating the relative position from the blade root to the blade tip; the vertical axis represents the leading and trailing radii of the blade, in millimeters. The solid curves represent the original distribution of the leading and trailing radii of the fan blade, respectively, while the dashed curves represent the distribution of the leading and trailing radii after adjustment according to the blade shape revision scheme described in this embodiment.

[0061] In terms of leading edge radius, the original radius curve generally shows a trend of first increasing and then decreasing, reaching a peak of nearly 3.0 mm in the middle radial position (approximately 0.45 to 0.7 normalized span). The radius in the leaf root region (0 to 0.2) is approximately 2.0 mm, and the radius in the leaf tip region (0.8 to 1.0) is close to 1.8 mm. After revision, the leading edge radius shows a local increase in the middle high value range, with the peak value increasing from approximately 2.85 mm to nearly 3.0 mm. The changes in the leaf root and leaf tip regions are relatively small, showing the characteristic of thickening of the leading edge at the main driving arc segment.

[0062] The original curve for the trailing edge radius showed an overall decreasing trend, gradually decreasing from approximately 1.7 mm at the leaf root to nearly 0.8 mm at the leaf tip. The revised trailing edge radius significantly increased in the intermediate radial section, especially in the normalized span of approximately 0.4 to 0.7, where the revised curve was noticeably higher than the original curve, with the trailing edge radius increasing from the original minimum of 0.8 mm to nearly 1.0 mm, demonstrating the effect of thickening the trailing edge at the auxiliary drive arc segment. The revisions at the leaf root and leaf tip regions showed smaller changes, maintaining the overall decreasing trend.

[0063] See Figure 7 and Figure 8 In a specific implementation, the fan blade structure that improves the wind-driving efficiency of the fan blade includes a blade body. The blade body is made of a material with certain rigidity and fatigue resistance. The blade body has a leading edge and a trailing edge. The leading edge is the edge that first contacts the surrounding air during the fan blade's rotation, and the trailing edge is the edge where the airflow leaves the blade surface during the fan blade's rotation. The blade body extends from the blade root to the blade tip, and its overall shape is arc-shaped or has a continuously torsional spatial curved surface structure to adapt to changes in airflow velocity at different radial positions during the fan blade's rotation.

[0064] In practical implementation, based on the different rotation radii of the blades, the blade body is divided into a low-speed section, a transition section, and a high-speed section along the radial direction. The low-speed section is located near the blade root, the high-speed section is located near the blade tip, and the transition section is located between the low-speed and high-speed sections. There are no obvious step-like height changes between the low-speed, transition, and high-speed sections; instead, the transitions are gradual through the curvature, chord length, and torsion angle of the blade body itself, allowing the structural changes at the trailing edge of the blade to be continuously distributed along the radial direction.

[0065] In a specific implementation, multiple spaced-apart arc-shaped tooth-like structures are provided on the trailing edge of the blade body. These arc-shaped tooth-like structures are arranged sequentially along the trailing edge of the blade, each having a connecting end that connects to the blade body and a free end extending outwards from the trailing edge. An arc-shaped notch is formed between adjacent arc-shaped tooth-like structures, so that the trailing edge of the blade no longer forms a continuous straight edge or a continuous smooth curved edge, but rather a segmented trailing edge profile composed of multiple arc-shaped tooth-like structures and multiple arc-shaped notches.

[0066] The number of arc-shaped tooth structures is determined based on the radial length of the blade body, the trailing edge length of the blade, and the operating speed of the blade. Multiple arc-shaped tooth structures are arranged sequentially along the radial direction of the blade body, with a preset spacing between adjacent arc-shaped tooth structures. The width of the arc-shaped notch can be adjusted according to the trailing edge width of the blade at the corresponding radial position, preventing the arc-shaped tooth structures from forming an overly concentrated structural abrupt change at the trailing edge of the blade. The extension direction of the arc-shaped tooth structure intersects with the rotation direction of the blade body, so that the arc-shaped tooth structure does not simply extend along the trailing edge direction, but forms a trailing edge protrusion structure with a certain tilt angle. The free end of the arc-shaped tooth structure extends towards the outer side of the trailing edge of the blade, forming an interlaced edge profile with adjacent arc-shaped tooth structures. When the blade body rotates, the air on the blade surface moves along the blade body towards the trailing edge, forming different local flow regions when passing through the arc-shaped tooth structures and the arc-shaped notches.

[0067] In practice, the arc-shaped tooth structure is integrally formed with the blade body. During blade body manufacturing, the leading edge, trailing edge, and surface are formed according to a predetermined blade cross-sectional profile, and multiple arc-shaped tooth structures are simultaneously formed at corresponding positions on the trailing edge. There is no independently assembled connection interface between the arc-shaped tooth structure and the blade body to avoid changes in the structural state of the trailing edge due to loosening of the connection during long-term blade rotation.

[0068] When machining the blade body, the root and tip positions are first determined, and the distribution ranges of the low-speed, transition, and high-speed sections are determined based on the radial length of the blade body. Then, the arrangement of the arc-shaped tooth structures is determined according to the blade chord length, blade thickness, and trailing edge curvature at each radial position, creating a gradually changing distribution along the trailing edge of the blade. The arc-shaped tooth structures in the low-speed section have a gentler arc profile, providing a larger transition area with the blade body; the arc-shaped tooth structures in the transition section gradually change their curvature and extension direction according to the trailing edge profile; the arc-shaped tooth structures in the high-speed section are set according to the trailing edge shape of the blade in the high-speed rotation region, ensuring a continuous spatial transition between the arc-shaped tooth structures in the high-speed section and the trailing edge. Through this arrangement, the multiple arc-shaped tooth structures are not identical repetitive structures, but rather form a continuously changing trailing edge structure with varying radial positions of the blade.

[0069] In practical implementation, when processing the arc-shaped notches between adjacent arc-shaped tooth structures, the notches are made to have smooth transition edges, avoiding the formation of sharp inner angles at the root of the notches. The arc-shaped notches are defined by the sides of adjacent arc-shaped tooth structures, and their opening direction faces outwards towards the trailing edge of the blade. When air passes over the trailing edge of the blade, part of the airflow moves along the outer edge of the arc-shaped tooth structure, while another part passes through the arc-shaped notches between adjacent arc-shaped tooth structures, thus forming multiple spaced local airflow channels at the trailing edge of the blade.

[0070] In practical implementation, the thickness of the arc-shaped toothed structure changes continuously with the thickness of the corresponding position on the blade body, ensuring no significant abrupt change in thickness between the arc-shaped toothed structure and the blade body. The outer surface of the arc-shaped toothed structure remains continuously connected to the blade surface of the blade body, forming a corresponding spatial curved surface according to the curved shape of the blade body. Through this structure, the arc-shaped toothed structure can rotate synchronously with the blade body, while simultaneously providing a segmented spatial structure for the airflow at the trailing edge of the blade.

[0071] When installing the blade body, the blade root is fixed to the fan hub, and multiple blade bodies are installed on the hub at circumferential intervals. After installation, the leading edge of each blade body faces the windward direction of the fan blade, and the trailing edge faces the direction of airflow departure. By adjusting the installation angle between the blade body and the hub, each blade body maintains a preset windward posture during rotation.

[0072] A low-speed rotation test was conducted on the installed fan blades to obtain the airflow motion state at different radial positions on the blade body, and the airflow distribution in the low-speed, transition, and high-speed sections was observed. When the airflow passes over the blade body surface and moves towards the trailing edge, the arc-shaped tooth structure segments the continuous airflow at the trailing edge, creating multiple localized separation zones from the airflow that would otherwise separate along the continuous trailing edge. Intermittent airflow channels are created between adjacent localized separation zones through arc-shaped notches. The arc, length, spacing, and extension direction of the arc-shaped tooth structure are adjusted according to the airflow state at different radial positions on the blade body. When the airflow in the low-speed section passes the trailing edge, the distribution density of the arc-shaped tooth structure is determined based on the corresponding airflow state in the low-speed section; when the airflow enters the transition section, the structural parameters of the arc-shaped tooth structure gradually change; when the airflow enters the high-speed section, the extension direction of the arc-shaped tooth structure is adapted to the blade surface profile of the high-speed rotating region of the blade body.

[0073] In specific implementation, the arc-shaped toothed structure is configured as multiple structural units arranged sequentially along the trailing edge of the blade, each structural unit having an independent arc-shaped outer contour. Adjacent structural units are separated by the arc-shaped notches, allowing each structural unit to form a local disturbance region under the action of airflow. Multiple local disturbance regions are arranged sequentially along the trailing edge of the blade, causing the airflow at the trailing edge of the blade to change from a continuous separation state to a segmented separation state.

[0074] As the blades rotate, the blades themselves push the surrounding air along their surface. The airflow enters the blade surface from the leading edge and moves along the blade surface towards the trailing edge. After reaching the trailing edge, the airflow generates localized motions in different directions under the influence of the arc-shaped toothed structure. Some of the airflow moves along the arc-shaped surface of the toothed structure, while some passes through the arc-shaped gaps between adjacent toothed structures, thus creating multiple localized airflow regions with different motion states at the trailing edge of the blade.

[0075] By adjusting the radial distribution of the arc-shaped toothed structure, the low-speed section, transition section, and high-speed section of the blade body each have corresponding trailing edge structures. The trailing edge structure of the low-speed section is used to adapt to the lower relative airflow velocity at the blade root; the trailing edge structure of the transition section is used to achieve a structural transition between the low-speed and high-speed sections; and the trailing edge structure of the high-speed section is used to adapt to the higher relative airflow velocity at the blade tip. This results in a segmented structure at the entire blade trailing edge that matches the radial airflow changes of the fan blade. The arc-shaped toothed structure undergoes a structural strength check, focusing on the connection points between the arc-shaped toothed structure and the blade body, as well as the location of the arc-shaped notch at the root. Areas with obvious sharp corners are rounded, and the spacing between adjacent arc-shaped toothed structures is checked for consistency, ensuring that each arc-shaped toothed structure maintains a stable spatial position during fan blade rotation.

[0076] In practice, a comparative test was conducted between a blade body with multiple arc-shaped toothed structures and a continuous trailing edge blade body without such structures. Under the same hub, number of blades, installation angle, and rotational speed, both types of blade bodies were rotated, and the airflow motion near the trailing edge of the blades was recorded. By comparing the airflow distribution at the trailing edge of the two types of blades, the number, spacing, curvature, and extension direction of the arc-shaped toothed structures were further adjusted.

[0077] In practice, if the airflow separation point at the trailing edge of the blade in the high-speed section is found to be too concentrated, the number of arc-shaped tooth structure segments in the corresponding area is increased or the width of the arc-shaped gap between adjacent arc-shaped tooth structures is adjusted. If a large local stagnation area is found at the trailing edge of the blade in the low-speed section, the extension length and curvature of the arc-shaped tooth structure in the low-speed section are adjusted to allow the airflow to form continuous segmented motion along the arc-shaped tooth structure and the arc-shaped gap. After adjusting the parameters of the arc-shaped tooth structure, the blade body is finally machined, and the leading edge, trailing edge, arc-shaped tooth structure, and arc-shaped gap are surface treated to ensure that the edges of each structure remain continuous and smooth. Subsequently, the quality consistency of each blade body is checked to ensure that multiple blade bodies installed on the same hub have consistent structural dimensions and mass distribution, and after dynamic balancing correction, they are installed into the fan blade drive device.

[0078] In practical implementation, during the rotation of the fan blade formed by the above structure, the airflow enters the blade surface from the leading edge of the blade and moves towards the trailing edge of the blade. The multiple arc-shaped tooth structures and arc-shaped notches at the trailing edge of the blade guide the airflow in segments, so that multiple mutually spaced local airflow separation areas are formed at the trailing edge of the blade. At the same time, by making the arc-shaped tooth structures radially varied along the low-speed section, transition section and high-speed section, the trailing edge structure of the blade is adapted to the airflow state at different radial positions of the fan blade, thereby forming a fan blade with a segmented trailing edge structure.

[0079] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application.

Claims

1. A technical design method for improving the wind-driving efficiency of fan blades, characterized in that, The method includes: Obtain the current blade shape parameter set, which includes the blade leading edge windward area value, the blade trailing edge air outlet angle value, the blade surface roughness value, and the blade mass distribution value; Based on the current blade profile parameter set, a segmented flow field mapping relationship is constructed for the fan blade in the rotating state. The segmented flow field mapping relationship is used to divide the fan blade radially into a low-speed section, a transition section, and a high-speed section, and associate each section with the corresponding airflow inertia coefficient. Based on the airflow inertia coefficients of the low-speed section and the high-speed section in the flow field segment mapping relationship, a sequence of airflow stagnation point coordinates at multiple arc segments on the fan blade surface is generated. Based on the coordinate sequence of each airflow residence point, the direction of frictional resistance deviation of the corresponding arc segment on the blade surface is determined, and the air outlet angle value of the trailing edge of the blade is adjusted using the direction of frictional resistance deviation to form a corrected air outlet angle distribution. The corrected air outlet angle distribution is coupled with the blade mass distribution value to calculate the driving torque transmission coefficient for each arc segment; According to the driving torque transmission coefficient sorted from high to low, the arc segment with the highest driving torque transmission coefficient is selected as the main driving arc segment, and the arc segment with the lowest driving torque transmission coefficient is selected as the auxiliary driving arc segment, and the fan blade profile revision scheme is output.

2. The technical design method for improving the wind-driving efficiency of fan blades according to claim 1, characterized in that, The process of obtaining the current blade shape parameter set includes: A contact profilometer is used to collect the upper and lower surface profiles of the blade cross section at preset radial intervals from the blade root to the blade tip along the radial direction of the blade. The upper surface contour line and the lower surface contour line are closed to generate a closed cross-sectional contour at each radial position; The coordinates of the leading edge point and the trailing edge point of the blade at each radial position are calculated based on the closed cross-sectional profile. The coordinates of the leading edge point are the coordinates of the point at the foremost end of the closed cross-sectional profile along the rotation direction, and the coordinates of the trailing edge point are the coordinates of the point at the very end of the closed cross-sectional profile along the rotation direction. Calculate the blade chord length at each radial position based on the coordinates of the blade leading edge point and the blade trailing edge point at each radial position; The blade chord lengths at each radial position are integrated into a chord length radial distribution curve, and the chord length radial distribution curve is used as a component of the current blade shape parameter set.

3. The technical design method for improving the wind-driving efficiency of fan blades according to claim 2, characterized in that, The step of constructing a segmented flow field mapping relationship for the fan blade in a rotating state based on the current blade profile parameter set includes: Based on the radial distribution curve of the chord length, the locations of abrupt changes in the rate of change of the chord length are extracted, and these locations are used as segment boundary markers. Using the section boundary marker as the boundary, the fan blades are radially divided into the low-speed section, the transition section, and the high-speed section; Calculate the average chord length in the low-speed section, the transition section, and the high-speed section respectively; Substitute each of the average chord lengths into a preset airflow inertia coefficient mapping table, and look up the corresponding airflow inertia coefficients for the low-speed section, the transition section, and the high-speed section to complete the construction of the flow field segment mapping relationship.

4. The technical design method for improving the wind-driving efficiency of fan blades according to claim 3, characterized in that, The sequence of coordinates of airflow stagnation points at multiple arc segments on the blade surface includes: The airflow inertia coefficient of the low-speed section is compared with that of the airflow inertia coefficient of the high-speed section to obtain the section inertia difference factor. Based on the segment inertia difference factor, determine the number of dwell points along the arc length direction of the fan blade surface; Starting from the leading edge of the fan blade, the initial dwelling point positions are arranged at equal intervals along the arc length direction of the fan blade surface according to the number of dwelling points mentioned above. For each initial dwell point location, the local radius of curvature of the blade section at that location is extracted, and the initial dwell point location is offset and corrected based on the local radius of curvature to obtain the coordinate sequence of each airflow dwell point.

5. The technical design method for improving the wind-driving efficiency of fan blades according to claim 4, characterized in that, The formation of the corrected air outlet angle distribution includes: For each stagnation point in each of the airflow stagnation point coordinate sequences, calculate the angle between the normal direction and the rotational tangential direction of that stagnation point; Each of the included angles is compared with a preset standard included angle. Dwelling points with included angles greater than the preset standard included angle are marked as high friction dwelling points, and dwelling points with included angles less than or equal to the preset standard included angle are marked as low friction dwelling points. Connecting adjacent high-friction dwelling points forms a high-friction arc segment, and connecting adjacent low-friction dwelling points forms a low-friction arc segment; Based on the projection position of the high-friction arc segment on the trailing edge of the blade, the air outlet angle value corresponding to the high-friction arc segment on the trailing edge of the blade is reduced by one adjustment step. Based on the projection position of the low-friction arc segment on the trailing edge of the blade, the air outlet angle value corresponding to the low-friction arc segment on the trailing edge of the blade is increased by one adjustment step, thus forming the corrected air outlet angle distribution.

6. The technical design method for improving the wind-driving efficiency of fan blades according to claim 5, characterized in that, The corrected outlet angle distribution is coupled with the blade mass distribution value to calculate the driving torque transmission coefficient for each arc segment, including: The corrected air outlet angle distribution is decomposed according to the arc segment position to obtain the local air outlet angle corresponding to each arc segment; Obtain the local mass value corresponding to each arc segment, wherein the local mass value is obtained by integrating the blade mass distribution value over the corresponding arc segment; Using an arc segment as a unit, multiply the sine value of the local air outlet angle of each arc segment by the local mass value of that arc segment to obtain the basic torque value of that arc segment; The driving torque transmission coefficient of each arc segment is obtained by dividing the basic torque value of each arc segment by the sum of the basic torque values ​​of all arc segments.

7. The technical design method for improving the wind-driving efficiency of fan blades according to claim 6, characterized in that, The output fan blade profile revision scheme includes: Using the main drive arc segment as the target arc segment, extract the first leading edge radius and the first trailing edge radius of the blade section corresponding to the main drive arc segment; Using the auxiliary drive arc segment as the target arc segment, extract the second leading edge radius and the second trailing edge radius of the blade section corresponding to the auxiliary drive arc segment; The difference between the first leading edge radius and the second leading edge radius is used to obtain the leading edge radius difference; the difference between the first trailing edge radius and the second trailing edge radius is used to obtain the trailing edge radius difference. Based on the leading edge radius difference and the trailing edge radius difference, a leading edge thickening command and a trailing edge thinning command are generated at the main drive arc segment, and a leading edge thinning command and a trailing edge thickening command are generated at the auxiliary drive arc segment. The fan blade shape revision scheme includes the leading edge thickening command, the trailing edge thinning command, the leading edge thinning command, and the trailing edge thickening command.

8. The technical design method for improving the wind-driving efficiency of fan blades according to claim 4, characterized in that, The process of offset correction of the initial dwell point position includes: calculating the ratio of the local radius of curvature of the blade section to the reference radius of curvature at each initial dwell point position, multiplying the ratio by a preset offset coefficient to obtain the offset correction amount, and moving the initial dwell point position along the blade surface normal direction according to the offset correction amount.

9. The technical design method for improving the wind-driving efficiency of fan blades according to claim 5, characterized in that, The method for determining the direction of frictional resistance deviation includes: at each airflow dwell point, the difference between the included angle and the preset standard included angle is used as a direction determination factor. When the direction determination factor is positive, the direction of frictional resistance deviation points to the trailing edge of the blade, and when the direction determination factor is negative, the direction of frictional resistance deviation points to the leading edge.

10. A fan blade structure that can improve the wind-driving efficiency of fan blades, implemented by the technical design method for improving the wind-driving efficiency of fan blades as described in any one of claims 1 to 9, characterized in that, The blade body includes a low-speed section, a transition section and a high-speed section arranged sequentially along the radial direction. The blade body has a leading edge and a trailing edge. The trailing edge of the blade is provided with a plurality of spaced arc-shaped tooth structures along the radial direction of the blade body. An arc-shaped notch is formed between adjacent arc-shaped tooth structures. The plurality of arc-shaped tooth structures extend from the low-speed section of the blade body to the high-speed section, and the extension direction of the arc-shaped tooth structures intersects with the rotation direction of the blade body, so that the trailing edge of the blade forms a trailing edge contour structure that varies in the radial direction.

Images