A turbine tip winglet design method based on water-drop function

Abstract

The application belongs to the technical field of tip winglet design. The application provides a turbine tip winglet design method based on a water droplet function. In the embodiment of the disclosure, a tip blade profile is obtained along a blade radial rotary surface, a winglet profile is added to the suction surface or pressure surface profile of the blade profile, and the winglet profile is controlled by a water droplet function. The original blade is equally divided, and the height of the winglet is determined by the number of divisions of the blade, which is usually 5%-10% of the radial height according to design experience. The winglet is divided into three categories according to control parameters: a suction surface winglet, a pressure surface winglet and a full-circumferential winglet. The profile of each winglet is smoothly connected to the profile of the original blade profile, and the winglet tip can be precisely controlled through modeling parameters. In addition, the shape of the winglet can be parameterized and optimized to obtain good flow control effect.

Description

TECHNICAL FIELD

[0001] The embodiment of the present disclosure relates to the technical field of tip winglet design, and in particular to a turbine tip winglet design method based on a water-drop function. BACKGROUND

[0002] During the operation of an axial turbine, due to the gap between the blade and the casing, a leakage flow is generated, which usually forms a tip leakage vortex (TLV). The TLV is a strong three-dimensional and unsteady flow structure, with high radial and circumferential component velocities, low axial component velocity and strong turbulent fluctuations. The tip leakage flow has a significant impact on turbine performance. Studies have shown that for every 1% increase in gap height, turbine stage efficiency decreases by 1% to 2%. In addition, tip leakage flow not only causes blade blockage and reduces flow capacity, but also brings high entropy increase through mixing, accounting for 30% of the total aerodynamic loss in the blade passage. With the development of modern axial turbine load, turbine pre-temperature and low aspect ratio blades, the negative impact of tip leakage flow / vortex is increasingly prominent, seriously hindering the further improvement of turbine performance. To address this challenge, researchers have developed various active and passive flow control methods to reduce the adverse effects of tip leakage flow. Tip winglets have been widely studied as an effective passive control method for tip leakage flow.

[0003] However, the tip winglet structure generated by the existing design method cannot achieve smooth transition with the original blade, and this discontinuity may cause airflow separation and performance loss, thereby affecting the overall efficiency of the turbine. In addition, it is an urgent problem to be solved to achieve fine control of the winglet geometry by adjusting a small number of parameters.

[0004] Therefore, it is necessary to improve one or more problems in the related technical solutions described above.

[0005] It should be noted that this section aims to provide background or context for the technical solutions of the present disclosure stated in the claims. The description herein is not admitted to be prior art merely because it is included in this section. SUMMARY

[0006] The purpose of the embodiment of the present disclosure is to provide a turbine tip winglet design method based on a water-drop function, thereby at least partially overcoming one or more problems caused by the limitations and defects of the related art.

[0007] According to the embodiment of the present disclosure, a turbine tip winglet design method based on a water-drop function is provided, which comprises:

[0008] Obtaining a tip blade profile along a blade radial revolution surface, and converting the tip blade profile into an initial planar two-dimensional blade profile;

[0009] obtaining a thickness distribution of the initial planar two-dimensional blade profile based on the initial planar two-dimensional blade profile;

[0010] determining a start point and an end point of a suction side winglet and a start point and an end point of a pressure side winglet of the initial planar two-dimensional blade profile according to the combination of the dimensionless parameter group;

[0011] obtaining a thickness distribution of the tip winglet according to the thickness distribution of the initial planar two-dimensional blade profile and the water drop function;

[0012] constructing an added pressure side winglet profile line and a suction side winglet profile line according to the thickness distribution of the tip winglet, the start point and the end point of the suction side winglet, and the start point and the end point of the pressure side winglet of the initial planar two-dimensional blade profile, so as to obtain a tip winglet of a target planar two-dimensional blade profile;

[0013] converting the tip winglet of the target planar two-dimensional blade profile into a tip winglet of a revolution surface.

[0014] Further, in the step of obtaining a tip blade profile along the blade radial revolution surface and converting the tip blade profile into the initial planar two-dimensional blade profile, the step comprises:

[0015] determining a revolution surface along the blade radial direction, taking a profile curve of the revolution surface as the tip blade profile, and converting the tip blade profile into the initial planar two-dimensional blade profile.

[0016] Further, the dimensionless parameter group comprises:

[0017] a suction side winglet start position W SS , a suction side winglet end position W SE , a pressure side winglet start position W PS , and a pressure side winglet end position W PE .

[0018] Further, in the step of obtaining a thickness distribution of the initial planar two-dimensional blade profile based on the initial planar two-dimensional blade profile, the step comprises:

[0019] offsetting a pressure side profile line and a suction side profile line of the initial two-dimensional blade profile blade body multiple times at equal intervals to generate a plurality of intersection points; wherein the number of intersection points is 1-2;

[0020] sequentially arranging the point set composed of the intersection points in an axial order to obtain a mean camber line of the initial planar two-dimensional blade profile;

[0021] taking a point on the mean camber line as a center to inscribe a circle of the blade profile to obtain a thickness distribution of the initial planar two-dimensional blade profile.

[0022] Further, in the step of determining a start point and an end point of a suction side winglet and a start point and an end point of a pressure side winglet of the initial planar two-dimensional blade profile according to the combination of the dimensionless parameter group, the step comprises:

[0023] The suction surface winglet start position multiplied by the axial chord length is set as the axial distance from the suction surface winglet start point to the leading edge point;

[0024] The suction surface winglet end position multiplied by the axial chord length is set as the axial distance from the suction surface winglet end point to the leading edge point;

[0025] The pressure surface winglet start position multiplied by the axial chord length is set as the axial distance from the pressure surface winglet start point to the leading edge point;

[0026] The pressure surface winglet end position multiplied by the axial chord length is set as the axial distance from the pressure surface winglet end point to the leading edge point;

[0027] The suction surface winglet start position and the suction surface winglet end position are obtained according to the axial distance from the suction surface winglet start point to the leading edge point and the axial distance from the suction surface winglet end point to the leading edge point;

[0028] The pressure surface winglet start position and the pressure surface winglet end position are obtained according to the axial distance from the pressure surface winglet start point to the leading edge point and the axial distance from the pressure surface winglet end point to the leading edge point.

[0029] Further, the expression of the suction surface winglet start position is:

[0030] W SS = L SS / C x

[0031] The expression of the suction surface winglet end position is:

[0032] W SE = L SE / C x

[0033] The expression of the pressure surface winglet start position is:

[0034] W PS = L PS / C x

[0035] The expression of the pressure surface winglet end position is:

[0036] W PE = L PE / C x

[0037] Wherein, L SS is the axial distance from the suction surface winglet start point to the leading edge point, L SE is the axial distance from the suction surface winglet end point to the leading edge point, L PS is the axial distance from the pressure surface winglet start point to the leading edge point, L PE is the axial distance from the pressure surface winglet end point to the leading edge point, and Cx is the axial chord length.

[0038] Further, the expression of the water-drop function is:

[0039]

[0040] wherein x is the radial position of the tip profile, y is the circumferential position, theta is the azimuth angle of the discrete point, a is the coefficient of the water-drop function, and is a constant;

[0041] The expression of the thickness distribution of the tip winglet is:

[0042] L i = l i x f(x)

[0043] wherein l i is the thickness distribution of the initial planar two-dimensional profile.

[0044] Further, in the step of constructing the added pressure surface winglet profile and suction surface winglet profile based on the thickness distribution of the tip winglet, the start point and the end point of the suction surface winglet of the initial planar two-dimensional profile, and the start point and the end point of the pressure surface winglet, comprises:

[0045] Based on the suction surface winglet start position to the suction surface winglet end position, combined with the thickness distribution of the tip winglet, the added suction surface winglet profile is constructed by using the thickness superposition method of the camber line;

[0046] Based on the pressure surface winglet start position to the pressure surface winglet end position, combined with the thickness distribution of the tip winglet, the added pressure surface winglet profile is obtained by using the thickness superposition method of the camber line;

[0047] According to the added suction surface winglet profile and the added pressure surface winglet profile, the tip winglet of the target planar two-dimensional profile is obtained.

[0048] Further, in the step of converting the tip winglet of the target planar two-dimensional profile into the tip winglet of the revolved surface, comprises:

[0049] Converting the tip winglet of the target planar two-dimensional profile into the tip winglet of the revolved surface;

[0050] Replacing the tip profile with the tip winglet of the revolved surface to generate a new blade.

[0051] Further, through coordinate transformation, the height of the final tip winglet of the revolved surface is 5%-10% of the radial height of the blade.

[0052] The technical scheme provided by the embodiments of the present disclosure can include the following beneficial effects:

[0053] In the embodiments of the present disclosure, by the above turbine blade tip winglet design method based on water droplet function, on the one hand, the discrete point coordinates of the blade tip profile along the blade radial revolving surface are obtained, the revolving surface blade profile is converted into a two-dimensional blade profile through coordinate transformation, and then the camber line and thickness distribution of the two-dimensional blade profile are solved. The thickness distribution of the blade tip winglet is constructed by using the dimensionless parameter for controlling the winglet shape and the water droplet function, and the profile of the blade tip winglet is obtained through the thickness superposition of the camber line. The two-dimensional blade profile after adding the blade tip winglet is converted into a revolving surface blade profile through a second coordinate transformation. On the other hand, the smooth transition of the winglet profile and the original blade profile can be realized by using the water droplet function, and the engineering requirements of the blade tip winglet are met. In addition, the position and thickness of the blade tip winglet and other details can be accurately controlled by a small number of dimensionless parameters, and unreasonable geometric shapes are ensured not to appear. In the optimization design process, no additional constraint conditions are required, so that a flexible and efficient optimization process is realized. The method is suitable for the design process of blade tip winglets of axial flow turbine blades for various purposes, and has a good regulating effect on the turbine blade tip leakage flow. BRIEF DESCRIPTION OF DRAWINGS

[0054] The accompanying drawings, which are incorporated into and form a part of the specification, illustrate one embodiment consistent with the present disclosure and, together with the description, serve to explain the principles of the disclosure. Obviously, the drawings in the following description are only some embodiments of the present disclosure, and other drawings can be obtained from these drawings without creative labor for those skilled in the art.

[0055] Figure 1 A step diagram of a turbine blade tip winglet design method based on a water droplet function in an exemplary embodiment of the present disclosure is shown;

[0056] Figure 2 A schematic diagram of a two-dimensional blade profile and a camber line obtained by coordinate transformation of a blade tip revolving surface profile in an exemplary embodiment of the present disclosure is shown;

[0057] Figure 3 A schematic diagram of a water droplet function curve in an exemplary embodiment of the present disclosure is shown;

[0058] Figure 4 A schematic diagram of the thickness distribution of an initial two-dimensional blade profile and the thickness distribution of a blade tip winglet in an exemplary embodiment of the present disclosure is shown;

[0059] Figure 5 A schematic diagram of a suction surface winglet, a pressure surface winglet and a full-circumferential winglet in an exemplary embodiment of the present disclosure is shown;

[0060] Figure 6 A schematic diagram of a three-dimensional blade with a winglet structure added in an exemplary embodiment of the present disclosure is shown;

[0061] Figure 7 Fig. 5 shows a schematic diagram of a blade geometry of a turbine rotor blade at 5% blade height H along a blade tip in an example embodiment of the present disclosure;

[0062] Figure 8 Fig. 6 shows a schematic diagram of a control effect of a three-dimensional blade with added winglet structure on tip leakage flow in an example embodiment of the present disclosure;

[0063] Figure 9 Fig. 7 shows a schematic diagram of a structure of a blade tip winglet in an example embodiment of the present disclosure. DETAILED DESCRIPTION

[0064] Example implementations will now be described more fully with reference to the accompanying drawings. Example implementations can be implemented in any

[0065] In addition, the drawings are only schematic and the dimensions of certain features are chosen for convenience of discussion only. Same reference numerals may

[0066] A turbine blade tip winglet design method based on a water droplet function is provided in the present example implementation. Referring to Fig. 1, the turbine blade tip winglet design method based on the water droplet function can include steps S101-S106. Figure 1

[0067] Step S101: Obtain a tip blade profile along a blade radial turning surface, and convert the tip blade profile into an initial planar two-dimensional blade profile;

[0068] Step S102: Obtain a thickness distribution of the initial planar two-dimensional blade profile based on the initial planar two-dimensional blade profile;

[0069] Step S103: Determine a starting point and an ending point of a suction surface winglet and a starting point and an ending point of a pressure surface winglet of the initial planar two-dimensional blade profile according to a combination of dimensionless parameter groups;

[0070] Step S104: Obtain a thickness distribution of the blade tip winglet according to the thickness distribution of the initial planar two-dimensional blade profile and a water droplet function;

[0071] ​Step S105: constructing the added pressure surface winglet profile and suction surface winglet profile according to the thickness distribution of the winglet, the start point and end point of the suction surface winglet of the initial planar two-dimensional blade profile, and the start point and end point of the pressure surface winglet, to obtain the winglet of the target planar two-dimensional blade profile;

[0072] Step S106: converting the winglet of the target planar two-dimensional blade profile into the winglet of the revolution surface.

[0073] Through the above turbine winglet design method based on the water droplet function, on the one hand, the discrete point coordinates of the winglet of the blade radial revolution surface are obtained, the revolution surface blade profile is converted into a planar two-dimensional blade profile through coordinate transformation, and then the mean camber line and thickness distribution of the two-dimensional blade profile are solved. The thickness distribution of the winglet is constructed by using the dimensionless parameter for controlling the shape of the winglet and the water droplet function, and the profile of the winglet is obtained through the thickness superposition of the mean camber line. The two-dimensional blade profile after adding the winglet is converted into a revolution surface blade profile through a second coordinate transformation. On the other hand, the water droplet function can realize the smooth transition of the winglet profile and the original blade profile, and meet the engineering requirements of the winglet. In addition, the position and thickness of the winglet and other details can be accurately controlled by a small number of dimensionless parameters, and unreasonable geometric shapes are ensured not to appear. In the optimization design process, no additional constraint conditions are needed, so that a flexible and efficient optimization process is realized. The method is suitable for the design process of the winglet of the turbine blade of various purposes, and has a good regulating effect on the turbine blade tip leakage flow.

[0074] In the following, reference will be made to Figures 1 to 9 The above turbine winglet design method based on the water droplet function in the present example embodiment will be described in more detail.

[0075] In step S101, the winglet of the blade radial revolution surface is obtained, and the winglet is converted into an initial planar two-dimensional blade profile.

[0076] Specifically, the winglet of the blade radial revolution surface is obtained, and the revolution surface blade profile (i.e. the winglet) is converted into a planar two-dimensional blade profile. Taking a cylindrical revolution surface as an example, the discrete point coordinates of the revolution surface blade profile are (x, y, z), the discrete point coordinates of the two-dimensional blade profile are (r, θ, z), and the coordinate transformation satisfies: θ = arctan (x / y), wherein x is the radial position of the revolution surface blade profile, y is the circumferential position, z is the axial position of the blade profile, r is the radius of the cylindrical coordinate system, θ is the azimuth angle of the discrete point, and the value range is 0-2π. The obtained winglet of the planar two-dimensional blade profile is shown in Figure 2 .

[0077] In step S102 and step S103, based on the initial planar two-dimensional blade profile, the thickness distribution of the initial planar two-dimensional blade profile is obtained; and according to the dimensionless parameter group, the start point and the end point of the suction surface winglet of the initial planar two-dimensional blade profile are determined, and the start point and the end point of the pressure surface winglet are determined.

[0078] Specifically, the camber line and the thickness distribution of the two-dimensional blade profile are solved, and the start point and the end point of the suction surface winglet and the pressure surface winglet are determined by four dimensionless parameters, which can be named as W SS , W SE , W PS , and W PE . The naming rules are as follows: W is the first letter of the English word Winglet, the subscript S is the first letter of the English word Suction, P is the first letter of the English word Pressure, the subscript S is the first letter of the English word Start, and E is the first letter of the English word End.

[0079] More specifically, the pressure surface and the suction surface profiles of the two-dimensional blade profile are offset multiple times at equal intervals, and the offset distance needs to be set to ensure that 1-2 intersection points are generated after each offset. The point set composed of these intersection points is arranged in axial order in turn, and the curve composed of the point set is the camber line of the blade profile. See FIG. 2. Figure 3 The inner tangent circle of the blade profile is made with the points on the camber line as the center, and the radius of the circle determines the thickness distribution of the two-dimensional blade profile. See FIG. 3. Figure 3 .

[0080] The dimensionless parameter multiplied by the axial chord length C x of the control winglet start point is the axial distance L Start from the winglet start point to the leading edge point. End Similarly, the dimensionless parameter multiplied by the axial chord length of the control winglet end point is the axial distance L SS from the winglet end point to the leading edge point. SS The axial distances obtained above can be used to determine the specific positions of the winglet start point and the winglet end point on the suction surface profile and the pressure surface profile of the two-dimensional blade profile. The mathematical expression of the dimensionless parameter is: W x = L SE / C SE , W x = L PS / C PS , W x = L PE / C PE , and W x = L .

[0081] In step S104 and step S105, the thickness distribution of the tip winglet is obtained according to the thickness distribution of the initial planar two-dimensional blade profile and the water-drop function; the thickness distribution of the tip winglet, the start point and the end point of the suction surface winglet of the initial planar two-dimensional blade profile, and the start point and the end point of the pressure surface winglet are used to construct the added pressure surface winglet profile and the suction surface winglet profile, so as to obtain the tip winglet of the target planar two-dimensional blade profile.

[0082] Specifically, when the start point and the end point positions of the winglet are determined, the water-drop function f(x) (see Figure 3 ) is used to construct the thickness distribution L i of the winglet along the normal direction of the camber line (see Figure 4 ). The thickness distribution L i of the winglet and the thickness distribution l i of the original blade profile satisfy the following relationship: L i = l i ×f(x), and then the pressure surface winglet profile and the suction surface winglet profile of the two-dimensional blade profile are constructed by using the camber line thickness superposition method.

[0083] More specifically, the thickness distribution of the winglet is constructed from the start point to the end point of the winglet. The thicknesses at the start point and the end point positions correspond to the thicknesses of the corresponding positions of the original two-dimensional blade profile. The thickness distribution of the remaining winglet part is obtained by multiplying the thickness values of the corresponding positions of the original blade profile by the water-drop function. In this way, it can be ensured that the winglet profile intersects with the original blade profile at the start point and the end point positions, and a smooth transition is achieved, thereby ensuring that the tip winglet has good aerodynamic performance.

[0084] The two-dimensional blade profile after adding the tip winglet is composed of three parts: the original blade profile between the leading edge point and the start point of the winglet, the winglet profile, and the original blade profile between the end point of the winglet and the trailing edge point.

[0085] In step S106, the tip winglet (see Figure 5 ) of the target planar two-dimensional blade profile is converted into a tip winglet of a revolution surface. Among them, the winglet added to the pressure surface is called pressure surface winglet; the winglet added to the suction surface is called suction surface winglet; and the winglet added to both the suction surface and the pressure surface of the target blade profile is called full-circumference winglet.

[0086] Specifically, the two-dimensional blade profile after adding the tip winglet is converted into a revolution surface blade profile. Taking the cylindrical revolution surface as an example, the discrete point coordinates (r, θ, z) of the two-dimensional blade profile after adding the winglet are converted into (x, y, z) coordinates. The coordinate transformation satisfies: x = rsinθ, y = rcosθ. After the second coordinate transformation, the final result is obtained.

[0087] The revolution surface blade profile after adding the tip winglet is used to replace the tip blade profile of the original three-dimensional blade, to generate a new blade, see Figure 6 .

[0088] In one specific embodiment, a portion of 5% of the radial height of the original blade is extracted (see Figure 7 ) for the addition of the winglet structure, which can be adjusted according to actual needs. The three-dimensional blade after adding the winglet is continuously smooth from the blade tip to the blade root, and has a good regulating effect on the tip leakage flow, see Figure 8 .

[0089] As shown in Figure 9 , it is a schematic diagram of the tip winglet structure.

[0090] Through the above turbine tip winglet design method based on the water droplet function, on the one hand, the discrete point coordinates of the tip blade profile along the blade radial revolving surface are obtained, and the revolving surface blade profile can be converted into a two-dimensional blade profile through coordinate transformation, and then the mean camber line and thickness distribution of the two-dimensional blade profile are solved. The thickness distribution of the tip winglet is constructed by using the dimensionless parameter for controlling the shape of the winglet and the water droplet function, and the profile of the tip winglet is obtained through the thickness superposition of the mean camber line. The two-dimensional blade profile after adding the tip winglet is converted into a revolving surface blade profile through a second coordinate transformation. On the other hand, the water droplet function can realize the smooth transition of the winglet profile and the original blade profile, and meet the engineering requirements of the tip winglet. In addition, the position and thickness of the tip winglet and other details can be accurately controlled by a small number of dimensionless parameters, and unreasonable geometric shapes are ensured not to appear. In the optimization design process, no additional constraint conditions are required, so that a flexible and efficient optimization process is realized. The method is suitable for the design process of tip winglets of axial turbine blades for various purposes, and has a good regulating effect on the turbine blade tip leakage flow.

[0091] It should be understood that the orientations or positional relationships indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise" and the like in the above description are based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the embodiments of the present disclosure and simplifying the description, and therefore cannot be understood as indicating or implying that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the embodiments of the present disclosure.

[0092] In addition, the terms "first" and "second" are only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined as "first" and "second" can explicitly or implicitly include one or more of the features. In the description of the embodiments of the present disclosure, the meaning of "multiple" is two or more, unless otherwise explicitly specified.

[0093] In the embodiments of the present disclosure, unless specifically defined and limited otherwise, the terms "mount", "connect", "connection", "fixed", and the like should be understood broadly, for example, can be fixed connection, can also be detachable connection, or integrated; can be mechanical connection, can also be electrical connection; can be direct connection, can also be indirect connection through an intermediate medium, can be internal communication of two elements or interaction relationship between two elements. For those skilled in the art, the specific meanings of the above terms in the present disclosure can be understood according to the specific circumstances.

[0094] In the embodiments of the present disclosure, unless specifically defined and limited otherwise, the first feature "on" or "under" the second feature can include that the first and second features are in direct contact, or that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, the first feature "on", "above" and "over" the second feature includes that the first feature is directly above and obliquely above the second feature, or only indicates that the horizontal height of the first feature is higher than that of the second feature. The first feature "under", "below" and "under" the second feature includes that the first feature is directly below and obliquely below the second feature, or only indicates that the horizontal height of the first feature is less than that of the second feature.

[0095] In the description of the specification, the description of the terms "one embodiment", "some embodiments", "example", "specific example" or "some examples" and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present disclosure. In the specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in the specification.

[0096] Other embodiments of the present disclosure will be apparent to those skilled in the art upon consideration of the specification and practice of the application disclosed herein. The present application is intended to cover any variations, uses or adaptive changes of the present disclosure that follow the general principles of the present disclosure and include known or customary practices in the art not disclosed in the present disclosure. The specification and examples are only considered as exemplary, and the true scope and spirit of the present disclosure are indicated by the appended claims.

Claims

1. A method for designing a turbine tip wing based on a water-drop function, characterized in that, The method comprises: obtaining a blade tip profile along a radial surface of revolution of the blade, and converting the blade tip profile into an initial planar two-dimensional blade profile; obtaining a thickness distribution of the initial planar two-dimensional blade profile based on the initial planar two-dimensional blade profile; determining a starting point and an ending point of a suction surface winglet and a starting point and an ending point of a pressure surface winglet of the initial planar two-dimensional blade profile according to a combination of dimensionless parameters; obtaining a thickness distribution of the blade tip winglet according to the thickness distribution of the initial planar two-dimensional blade profile and a water droplet function; constructing an added pressure surface winglet profile and a suction surface winglet profile according to the thickness distribution of the blade tip winglet, the starting point and the ending point of the suction surface winglet of the initial planar two-dimensional blade profile, and the starting point and the ending point of the pressure surface winglet, to obtain a blade tip winglet of a target planar two-dimensional blade profile; converting the blade tip winglet of the target planar two-dimensional blade profile into a blade tip winglet of a surface of revolution.

2. The method of designing a turbine tip winglet based on water droplet function according to claim 1, wherein, In the step of obtaining a blade tip profile along a radial surface of revolution of the blade, and converting the blade tip profile into an initial planar two-dimensional blade profile, the step comprises: determining the surface of revolution along a radial direction of the blade, taking a profile curve of the surface of revolution as the blade tip profile, and converting the blade tip profile into the initial planar two-dimensional blade profile.

3. The method of designing a turbine tip winglet based on water droplet function as claimed in claim 1, wherein, The combination of dimensionless parameters comprises: Suction side winglet start position W SS Suction side winglet end position W SE Pressure side winglet start position W PS Pressure side winglet end position W PE .

4. The method of designing a turbine tip winglet based on water droplet function according to claim 3, wherein, In the step of obtaining a thickness distribution of the initial planar two-dimensional blade profile based on the initial planar two-dimensional blade profile, the step comprises: offsetting a pressure surface profile and a suction surface profile of the initial two-dimensional blade profile body multiple times at equal intervals to generate a plurality of intersection points; wherein the number of intersection points is 1-2; sequentially arranging a point set composed of the intersection points in an axial order to obtain a mean camber line of the initial planar two-dimensional blade profile; taking a point on the mean camber line as a center to inscribe a circle of the blade profile to obtain the thickness distribution of the initial planar two-dimensional blade profile.

5. The method of designing a turbine tip winglet based on water droplet function according to claim 4, wherein, In the step of determining a starting point and an ending point of a suction surface winglet and a starting point and an ending point of a pressure surface winglet of the initial planar two-dimensional blade profile according to a combination of dimensionless parameters, the step comprises: setting a suction surface winglet starting position multiplied by an axial chord length as an axial distance from the suction surface winglet starting point to a leading edge point; setting a suction surface winglet ending position multiplied by the axial chord length as an axial distance from the suction surface winglet ending point to the leading edge point; setting a pressure surface winglet starting position multiplied by the axial chord length as an axial distance from the pressure surface winglet starting point to the leading edge point; setting a pressure surface winglet ending position multiplied by the axial chord length as an axial distance from the pressure surface winglet ending point to the leading edge point; obtaining the suction surface winglet starting position and the suction surface winglet ending position according to the axial distance from the suction surface winglet starting point to the leading edge point and the axial distance from the suction surface winglet ending point to the leading edge point; obtaining the pressure surface winglet starting position and the pressure surface winglet ending position according to the axial distance from the pressure surface winglet starting point to the leading edge point and the axial distance from the pressure surface winglet ending point to the leading edge point.

6. The method of designing a turbine tip winglet based on water droplet function according to claim 5, wherein, An expression of the suction surface winglet starting position is: W SS = L SS / C x An expression of the suction surface winglet ending position is: W SE = L SE / C x An expression of the pressure surface winglet starting position is: W PS = L PS / C x An expression of the pressure surface winglet ending position is: W PE = L PE / C x where Ls SS is the axial distance from the suction surface winglet start point to the leading edge point, Ls SE is the axial distance from the suction surface winglet end point to the leading edge point, Ls PS is the axial distance from the pressure surface winglet start point to the leading edge point, Lp PE is the axial distance from the pressure surface winglet end point to the leading edge point, C x is the axial chord length.

7. The method of designing a turbine tip winglet based on water droplet function according to claim 6, wherein, An expression of the water droplet function is: wherein x is a radial position of the blade tip profile, y is a circumferential position, θ is an azimuth angle of a discrete point, and a is a coefficient of the water droplet function and is a constant; An expression of the thickness distribution of the blade tip winglet is: L i = l i x f(x) wherein l i is the thickness distribution of the initial planar two-dimensional airfoil.

8. The method of designing a turbine tip winglet based on water droplet function according to claim 7, wherein, The step of constructing the added pressure surface wing profile and the added suction surface wing profile to obtain the tip wing of the target planar two-dimensional blade profile according to the thickness distribution of the tip wing, the start point and the end point of the suction surface wing of the initial planar two-dimensional blade profile, and the start point and the end point of the pressure surface wing comprises: Based on the suction surface wing start position to the suction surface wing end position, combining the thickness distribution of the tip wing, the added suction surface wing profile is constructed by using the thickness superposition method of the mean camber line; Based on the pressure surface wing start position to the pressure surface wing end position, combining the thickness distribution of the tip wing, the added pressure surface wing profile is obtained by using the thickness superposition method of the mean camber line; According to the added suction surface wing profile and the added pressure surface wing profile, the tip wing of the target planar two-dimensional blade profile is obtained.

9. The method of designing a turbine tip winglet based on a water droplet function according to claim 8, wherein, The step of converting the tip wing of the target planar two-dimensional blade profile into the tip wing of the rotary surface comprises: Converting the tip wing of the target planar two-dimensional blade profile into the tip wing of the rotary surface; Using the tip wing of the rotary surface to replace the tip blade profile to generate a new blade.

10. The method of designing a turbine tip winglet based on a water droplet function according to claim 9, wherein, Through coordinate transformation, the height of the final tip wing of the rotary surface is 5%-10% of the radial height of the blade.

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