A method of retrofitting a blade, a method of retrofitting an impeller and an impeller

Abstract

A blade modification method, an impeller modification method and an impeller. The blade modification method comprises obtaining a model of a reference blade, drawing 2n+1 span surface contour lines on the model, the 2n+1 span surface contour lines being arranged in sequence from a first end of the reference blade connecting a hub to a second end of the reference blade connecting a rim, wherein the first contour line is an edge line of an end surface of the first end, and the 2n+1 contour line is an edge line of an end surface of the second end; increasing the spatial angle of the 2n+1 contour line to the whole of the 2n+1 contour line in the rotation direction of the reference blade; and fitting a smooth surface using the 1st to 2n+1 contour lines, the smooth surface being used as the outer contour of the modified blade. The present application can quickly and effectively optimize the internal flow field of the impeller, and can achieve the effects of inhibiting or delaying the occurrence of rotating stall and cavitation, and improving the internal unsteady unstable flow phenomenon of the unit.

Description

Technical Field

[0001] This article relates to fluid machinery technology, and in particular to a blade modification method, an impeller modification method, and an impeller. Background Technology

[0002] Hydropower consistently ranks first in annual power generation among renewable energy sources, making the development of pumped storage, with its rapid and large-capacity regulation capabilities, an indispensable key measure in my country's energy development strategy. However, as pumped storage evolves towards larger capacities and ultra-high heads, unit safety issues caused by flow instability have become a significant obstacle to the international development of pumped storage technology.

[0003] Rotating stall and cavitation are two common unstable flow phenomena in fluid machinery. When a diffuser-equipped impeller pump operates under unbalanced conditions, the increased blade inlet angle of attack and the dynamic-static interference effect can easily induce rotating stall in the blade flow. Once stall occurs, its propagation velocity in the blade channel is much lower than the impeller rotation speed, inducing low-frequency, high-amplitude water pressure pulsations. Simultaneously, when the inlet ambient pressure decreases, cavitation flow is easily induced at the inlet and blade tip clearance, directly affecting pump performance and stable operation. In actual unit operation, the cavitation flow induced by the blade tip clearance is closely related to the rotating stall in the blade channel, exhibiting a strong intrinsic correlation.

[0004] In order to suppress the rotating stall cluster induced inside the vane pump and improve its cavitation performance, some optimization and modification methods can be sought in engineering: such as adjusting the shape of the blade inlet to improve its cavitation performance, adjusting the guide vane opening, and expanding the clearance in the bladeless zone to suppress the propagation of the rotating stall cluster.

[0005] However, a comprehensive and systematic understanding of the spatiotemporal interaction mechanism between rotating stall and cavitation flow is still lacking, particularly regarding the incomplete guidance for improving pump performance. Currently, optimization algorithms are commonly used to evaluate impeller blade parameters; however, these methods require numerous computational examples and data to improve optimization accuracy, resulting in significant time and computational cost.

[0006] To better meet the operational stability requirements of pumped storage units, it is urgent to further investigate the dynamic characteristics and formation mechanism of rotating stall and cavitation flow induced in impeller pumps, and to seek a universally applicable design optimization method to improve unstable flow. Currently, there are no universally applicable modification methods on the market that fundamentally improve rotating stall and cavitation flow in impeller pumps. Summary of the Invention

[0007] This invention, based on the mechanism of rotational stall and cavitation flow induction in impeller pumps, provides a blade modification method to suppress rotational stall between blades and improve cavitation performance. This invention can quickly and effectively optimize the internal flow field of the impeller, thereby suppressing or delaying the occurrence of rotational stall and cavitation, and improving unsteady and unstable flow phenomena within the unit. The blade modification method specifically includes:

[0008] Obtain a model of the reference blade, and draw 2n+1 spanwise contour lines on the model. The 2n+1 spanwise contour lines are arranged sequentially from the first end of the reference blade connected to the hub to the second end of the reference blade connected to the rim. The first spanwise contour line is the edge line of the end face of the first end, and the 2n+1 spanwise contour line is the edge line of the end face of the second end. 2n-1 spanwise contour lines are evenly drawn on the surface of the reference blade model between the first spanwise contour line and the 2n+1 spanwise contour lines.

[0009] The spatial angle of the entire spanwise profile from the second spanwise profile to the 2n+1 spanwise profile increases in the direction of rotation of the reference blade, and the increase in the spatial angle from the second spanwise profile to the 2n+1 spanwise profile increases sequentially.

[0010] A smooth surface is fitted using the first to the (2n+1)th spanwise contour lines, and this smooth surface serves as the outer contour of the modified blade.

[0011] In one illustrative embodiment, the increase in the spatial angle from the second spanning surface profile line to the (2n+1)th spanning surface profile line is in an arithmetic progression.

[0012] In one illustrative embodiment, the increase in the spatial angle of the 2n+1th spanning plane profile is greater than or equal to 28°.

[0013] In one illustrative embodiment, as the spatial angle of each spanning profile line is increased, the spatial angle of each point from the leading edge to the trailing edge of the spanning profile line increases uniformly.

[0014] In one illustrative embodiment, the second to the (2n-1)th spanwise contour lines divide the model of the reference blade into 2n segments in the direction from the first end to the second end.

[0015] In an illustrative embodiment, a rectangular coordinate system is established in a two-dimensional plane perpendicular to the blade's rotation axis. The intersection of the blade's rotation axis and the two-dimensional plane is the origin of the coordinate system. A horizontal axis X passing through the origin is set in the two-dimensional plane. The spatial angle of any point on the spanwise contour line is the angle between the vector of the projection from the origin to this point onto the two-dimensional plane and the horizontal axis X.

[0016] In one illustrative embodiment, the position of the first spanning surface profile remains constant.

[0017] This embodiment also proposes an impeller modification method, which includes the steps of the blade modification method described above.

[0018] This embodiment also proposes an impeller, which includes blades, the blades having a smooth curved surface as the outer contour obtained by the blade modification method described above.

[0019] This blade modification method has the following advantages:

[0020] 1. The modification method is simple. The blade model can be modified simply by adjusting the size of the leading and trailing edge space angles of different spanwise profiles of the blade. This greatly simplifies the optimization process and improves production efficiency and operational reliability.

[0021] 2. Wide applicability: Most existing flow optimization techniques make tentative modifications to the flow at the leading edge of blades or in the bladeless region, and also need to consider the interaction effects between various factors, making the process relatively complex. This application changes the spatial distribution characteristics of the flow by changing the relative position of the blades along the spanwise direction, thereby suppressing or delaying rotational stall and cavitation initiation. This blade modification method can be widely applied to flow enhancement in vane pumps with diffusers.

[0022] 3. The axial flow channel, inlet and outlet placement angles, and wrap angles of each spanwise profile of the blade itself are not changed, that is, the design operating point of the impeller itself is not changed.

[0023] Other features and advantages of this application will be set forth in the following description. Other advantages of this application can be realized and obtained through the solutions described in the description and accompanying drawings. Attached Figure Description

[0024] The accompanying drawings are used to provide an understanding of the technical solutions of this application and constitute a part of the specification. They are used together with the embodiments of this application to explain the technical solutions of this application and do not constitute a limitation on the technical solutions of this application.

[0025] Figure 1 This is a three-dimensional schematic diagram of an impeller before blade modification in an embodiment of this application;

[0026] Figure 2 This is a perspective view of an impeller before blade modification in an embodiment of this application;

[0027] Figure 3 This is a schematic diagram of the blade profile space angle;

[0028] Figure 4 This is a schematic diagram of the impeller's forward tilt angle after the blade modification;

[0029] Figure 5 This is a schematic diagram of the impeller with modified blades in an embodiment of this application. Detailed Implementation

[0030] This application describes several embodiments, but these descriptions are exemplary and not restrictive, and it will be apparent to those skilled in the art that many more embodiments and implementations are possible within the scope of the embodiments described herein. Although many possible combinations of features are shown in the drawings and discussed in the detailed description, many other combinations of the disclosed features are also possible. Unless specifically limited, any feature or element of any embodiment may be used in combination with, or may replace, any feature or element of any other embodiment.

[0031] This application includes and contemplates combinations of features and elements known to those skilled in the art. The embodiments, features, and elements disclosed in this application can also be combined with any conventional features or elements to form unique inventive solutions. Any feature or element of any embodiment can also be combined with features or elements from other inventive solutions to form another unique inventive solution. Therefore, it should be understood that any feature shown and / or discussed in this application can be implemented individually or in any suitable combination. Therefore, the embodiments are not limited except by the limitations imposed by the appended claims and their equivalents. Furthermore, various modifications and changes can be made within the scope of the appended claims.

[0032] Furthermore, in describing representative embodiments, the specification may have presented methods and / or processes as a specific sequence of steps. However, the method or process should not be limited to the specific order of steps described herein, to the extent that it does not depend on such a specific order. As will be understood by those skilled in the art, other sequences of steps are also possible. Therefore, the specific order of steps set forth in the specification should not be construed as a limitation of the claims. Moreover, the claims concerning the method and / or process should not be limited to the steps performed in the written order, and those skilled in the art will readily understand that these orders can be varied and still remain within the spirit and scope of the embodiments of this application.

[0033] A centrifugal pump includes an impeller 100 and a casing. The impeller is housed within the casing and rotatably connected to it, and can rotate around its own axis. A motor can be connected to the impeller, and the motor can drive the impeller to rotate.

[0034] like Figure 1 As shown, Figure 1This embodiment shows an impeller 100 before blade modification. The impeller 100 includes a hub 2, a rim 3, and multiple reference blades 1. The hub 2 is typically constructed as a rotating body and is located in the middle of the impeller 100. The hub 2 can be a rotating body with a gradually increasing diameter from one end to the other. The rim 3 is constructed as a generally cylindrical shape. The diameter of the rim 3 gradually increases from one end to the other. The rim 3 is fitted over the hub 2 and is coaxially arranged with the hub 2, with the smaller diameter ends of the hub 2 and the rim 3 facing the same direction. There is an annular gap between the rim 3 and the hub 2. The diameter of this annular gap is small at one end and large at the other end. The reference blades 1 are disposed within the annular gap, and multiple reference blades 1 are evenly distributed around the hub 2. The reference blades 1 extend from the hub 2 to the rim 3. The reference blades 1 are provided with a first end and a second end. The first end and the second end are set opposite to each other: the end face of the first end of the reference blade 1 is connected to the outer peripheral wall of the hub 2, and the end face of the second end of the reference blade 1 is connected to the inner peripheral wall of the rim 3.

[0035] This embodiment also proposes a blade modification method to suppress inter-blade rotational stall and improve cavitation performance. This blade modification method can improve the blades of the impeller 100 described above, and includes the following steps:

[0036] Step S1: Obtain the model of the reference blade 1, and draw 2n+1 spanwise contour lines on the model of the reference blade 1. The 2n+1 spanwise contour lines are arranged sequentially from the first end of the reference blade 1 connected to the hub 2 to the second end of the reference blade 1 connected to the rim 3. Among them, the first spanwise contour line 4 is the edge line of the end face of the first end of the reference blade 1, and the 2n+1 spanwise contour line 5 is the edge line of the end face of the second end of the reference blade 1. Draw 2n-1 spanwise contour lines evenly on the surface of the model of the reference blade 1 between the first spanwise contour line 4 and the 2n+1 spanwise contour line 5.

[0037] Reference blade 1 is the blade that needs to be modified. A model of impeller 100 can be pre-built, which includes the model of reference blade 1. The model of reference blade 1 is a virtual model, which at least includes the outer contour shape of reference blade 1.

[0038] like Figure 2As shown, 2n+1 spanwise contour lines are drawn on the model of the reference blade 1, where n is a positive integer greater than or equal to 1. The spanwise contour lines are closed loops. These 2n+1 lines are arranged side-by-side from the first end to the second end of the reference blade 1, with adjacent lines spaced apart. The first spanwise contour line 4 is the edge line of the end face of the first end of the reference blade 1, i.e., the edge line of the interface between the first end of the reference blade 1 and the hub 2. The 2n+1 spanwise contour line 5 is the edge line of the end face of the second end of the reference blade 1, i.e., the edge line of the interface between the second end of the reference blade 1 and the rim 3. The second to 2n-1 spanwise contour lines are all loops extending along the surface of the reference blade 1, extending from the leading edge of the reference blade 1 along one plate surface to the trailing edge, and then along the other plate surface to the leading edge, forming a closed loop. The leading edge of the reference blade 1 is the windward edge of the reference blade 1, and the trailing edge of the reference blade 1 is the edge of the reference blade 1 opposite to the windward edge.

[0039] The second to the (2n-1)th spanwise contour lines are located on the model surface of the reference blade 1 between the first spanwise contour line 4 and the (2n+1)th spanwise contour line 5. The second to the (2n-1)th spanwise contour lines divide the model of the reference blade 1 into 2n segments in the direction from the first end to the second end. The model of the reference blade 1 is divided into 2n-1 spanwise contour lines at equal intervals on the surface between the first spanwise contour line 4 and the (2n+1)th spanwise contour line 5.

[0040] Step S2: Increase the spatial angle of the entire spanning profile line from the second spanning surface profile line to the 2n+1 spanning surface profile line 5 in the rotation direction of the reference blade 1. The increase in the spatial angle from the second spanning surface profile line to the 2n+1 spanning surface profile line 5 increases sequentially. Proceed to step S3.

[0041] like Figure 3 As shown, a rectangular coordinate system can be pre-established in a two-dimensional plane perpendicular to the blade's rotation axis before step S2. The intersection of the blade's rotation axis and the two-dimensional plane is the origin of the coordinate system. A horizontal axis X passing through the origin is set in the two-dimensional plane. The spatial angle of any point on the spanwise contour line is the angle between the vector of the projection from the origin to this point on the two-dimensional plane and the horizontal axis X.

[0042] When a point at the leading edge of the spanning plane contour is projected onto this two-dimensional plane, it forms a leading-edge point projection. The angle between the vector from the origin to the leading-edge point projection and the horizontal axis X is the spatial angle θ at the leading edge of the spanning plane contour. 01 The points at the trailing edge of the spanning surface profile are projected onto this two-dimensional plane to form trailing edge point projections. The angle between the vector from the origin to the trailing edge point projection and the horizontal axis X is the spatial angle θ at the trailing edge of the spanning surface profile.02 .

[0043] The spatial angle of the spanwise profile line increases in the direction of rotation of the reference blade 1, which means that the translational spanwise profile line is rotated as a whole around the rotation axis of the reference blade 1 in the direction of rotation of the reference blade 1. The increase in the spatial angle from the 2nd spanwise profile line to the 2n+1th spanwise profile line 5 increases sequentially, which means that the angle of rotation of the 2nd spanwise profile line to the 2n+1th spanwise profile line 5 around the rotation axis of the reference blade 1 in the direction of rotation of the reference blade 1 is larger.

[0044] The spatial angles from the second spanning surface profile line to the (2n+1)th spanning surface profile line 5 are increased in the direction of blade rotation, with the increase in spatial angles from the second spanning surface profile line to the (2n+1)th spanning surface profile line 5 increasing sequentially. Preferably, the increase in spatial angles from the second spanning surface profile line to the (2n+1)th spanning surface profile line 5 increases in an arithmetic progression. For example, if the increase in spatial angle of the second spanning surface profile line is θ, then the increase in spatial angle of the third spanning surface profile line is 2×θ... and the increase in spatial angle of the (2n+1)th spanning surface profile line 5 is 2n×θ, where θ is greater than zero.

[0045] When the spatial angle of the second spanning surface profile line to the (2n+1)th spanning surface profile line 5 is increased, the spatial angle of each point from the leading edge to the trailing edge on any spanning surface profile line increases uniformly.

[0046] like Figure 4 As shown, the position of the first spanning profile line 4 remains unchanged. Compared to the first spanning profile line 4, the relative positions of the second to the (2n+1)th spanning profile lines in space change, with the (2n+1)th spanning profile line 5 shifting the most in space.

[0047] Step S3: Use the first to the (2n+1)th spanwise surface contour lines 5 to fit a smooth surface through spline interpolation. This smooth surface serves as the outer contour of the modified blade 1a.

[0048] A smooth surface is fitted using the unchanged first spanwise profile line 4 and the newly generated second to (2n+1)th spanwise profile lines 5. The fitted smooth surface serves as the outer contour of the modified blade 1a. Keeping the position of the first spanwise profile line 4 unchanged ensures that the blade's placement position at the hub 2 remains constant.

[0049] like Figure 4 , 5 As shown, due to the increase in the spatial angle between the second spanwise profile line and the (2n+1)th spanwise profile line 5 in the direction of blade rotation, the modified blade 1a is tilted forward as a whole in the direction of blade rotation from the hub 2 to the rim 3, forming a forward-tilted blade. Figure 4 As shown, lean angle This is the difference between the leading edge spatial angle of the impeller blade near the rim and the leading edge spatial angle of the blade near the hub. This angle reflects the overall forward tilt of the blade. When the forward tilt angle is 0°, the blade is a conventional vertical blade; the larger the forward tilt angle, the greater the forward tilt of the blade. In this invention, the spatial angle 2nθ is simultaneously increased at both the leading and trailing edges of the (2n+1)th spanwise profile. This blade modification method has the following advantages:

[0050] 1. The modification method is simple. The blade model can be modified simply by adjusting the size of the leading and trailing edge space angles of different spanwise profiles of the blade. This greatly simplifies the optimization process and improves production efficiency and operational reliability.

[0051] 2. Wide applicability: Most existing flow optimization techniques make tentative modifications to the flow at the leading edge of blades or in the bladeless region, and also need to consider the interaction effects between various factors, making the process relatively complex. This application changes the spatial distribution characteristics of the flow by changing the relative position of the blades along the spanwise direction, thereby suppressing or delaying rotational stall and cavitation initiation. This blade modification method can be widely applied to flow enhancement in vane pumps with diffusers.

[0052] 3. The axial flow channel, inlet and outlet placement angles, and wrap angles of each spanwise profile of the blade itself are not changed, that is, the design operating point of the impeller itself is not changed.

[0053] In one illustrative embodiment, in step S1, 2n+1 spanwise contour lines are drawn on the reference blade 1, where n is greater than 2.

[0054] n determines the number of spanwise profile lines, which in turn determines the precision of the blade's spanwise profile line division. The larger n is, the higher the precision of the blade's spanwise profile line division. The minimum value of n is preferably 2, meaning that the reference blade 1 should be divided into at least 5 segments along the spanwise direction, and 5 spanwise profile lines should be drawn on the reference blade 1, thereby ensuring the accuracy of the modification.

[0055] In one illustrative embodiment, in step S2, the increase in the spatial angle of the (2n+1)th spanning surface profile line 5 is greater than or equal to 28°.

[0056] The increase in the spatial angle of the 2n+1 spanwise profile line 5 is 2n×θ. When this increase of 2n×θ reaches 28°, it can significantly delay the stall and cavitation initiation point, thereby suppressing or delaying the rotational stall and cavitation occurrence point and improving the unsteady and unstable flow phenomena inside the unit.

[0057] This embodiment also proposes an impeller modification method, which includes all the steps of the blade modification method described above.

[0058] This embodiment also proposes an impeller including a modified blade 1a. The modified blade 1a uses a smooth curved surface obtained by the blade modification method described above as its outer contour.

[0059] In one illustrative embodiment, such as Figure 5 As shown, the impeller includes a hub 2, a rim 3, and multiple modified blades 1a. The hub 2 is typically constructed as a rotating body and is located in the middle of the impeller 100. The hub 2 can be a rotating body with a gradually increasing diameter from one end to the other. The rim 3 is generally cylindrical. The diameter of the rim 3 gradually increases from one end to the other. The rim 3 is fitted over the hub 2 and is coaxially arranged with the hub 2, with the smaller diameter ends of the hub 2 and rim 3 facing the same direction. There is an annular gap between the rim 3 and the hub 2. The diameter of this annular gap is smaller at one end and larger at the other end. The modified blades 1a are disposed within the annular gap, and multiple modified blades 1a are evenly distributed around the hub 2. The modified blades 1a extend from the hub 2 to the rim 3. The modified blades 1a have a first end and a second end, which are positioned opposite each other. After modification, the end face of the first end of the blade 1a is connected to the outer peripheral wall of the hub 2, and the end face of the second end of the blade 1a is connected to the inner peripheral wall of the rim 3.

[0060] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0061] Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first," "second," etc., may explicitly or implicitly include at least one of those features.

[0062] In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise expressly and specifically limited.

[0063] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "joining," "fixing," etc., should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral part; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0064] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0065] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0066] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A blade modification method for suppressing inter-blade rotational stall and improving cavitation performance, characterized in that, include: Obtain a model of the reference blade, and draw 2n+1 spanwise contour lines on the model. The 2n+1 spanwise contour lines are arranged sequentially from the first end of the reference blade connected to the hub to the second end of the reference blade connected to the rim. The first spanwise contour line is the edge line of the end face of the first end, and the 2n+1 spanwise contour line is the edge line of the end face of the second end. 2n-1 spanwise contour lines are evenly drawn on the surface of the reference blade model between the first spanwise contour line and the 2n+1 spanwise contour lines. The spatial angle of the entire spanwise profile from the second spanwise profile to the 2n+1 spanwise profile increases in the direction of rotation of the reference blade, and the increase in the spatial angle from the second spanwise profile to the 2n+1 spanwise profile increases sequentially. A smooth surface is fitted using the first to the (2n+1)th spanwise contour lines, and this smooth surface serves as the outer contour of the modified blade. The increase in the spatial angle from the second spanning surface profile line to the (2n+1)th spanning surface profile line is in the form of an arithmetic progression. The increase in the spatial angle of the 2n+1th spanning surface profile is greater than or equal to 28°.

2. The blade modification method according to claim 1, characterized in that, When the spatial angle of each spanning profile line is increased, the spatial angle of each point from the leading edge to the trailing edge of the spanning profile line increases uniformly.

3. The blade modification method according to claim 1, characterized in that, The second to the 2n-1 spanwise contour lines divide the model of the reference blade into 2n segments in the direction from the first end to the second end.

4. The blade modification method according to claim 1, characterized in that, Establish a rectangular coordinate system in a two-dimensional plane perpendicular to the blade's rotation axis. The intersection of the blade's rotation axis and this two-dimensional plane is the origin of the coordinate system. Set a horizontal axis X passing through the origin in the two-dimensional plane. The spatial angle of any point on the spanwise contour line is the angle between the vector of the projection from the origin to this point on the two-dimensional plane and the horizontal axis X.

5. The blade modification method according to claim 1, characterized in that, The position of the first spanning surface contour line remains unchanged.

6. A method for impeller modification, characterized in that, The impeller modification method includes the steps of the blade modification method as described in any one of claims 1 to 5.

7. An impeller, characterized in that, Including the modified blades; The modified blade uses a smooth curved surface obtained by the blade modification method as described in any one of claims 1 to 5 as its outer contour.

8. The impeller according to claim 7, characterized in that, The impeller also includes a hub and a rim coaxially arranged with the hub, and the two ends of the modified blade are respectively connected to the hub and the rim.

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