Turbine tip winglet design method based on water drop type function

Abstract

The invention belongs to the technical field of blade tip winglet design. The invention provides a turbine blade tip winglet design method based on a water drop type function. According to the embodiment of the invention, the blade tip blade profile is obtained along the radial rotation surface of the blade, the small airfoil profile is added by taking the suction surface or pressure surface profile of the blade profile as a reference, and the small airfoil profile is controlled by a water drop type function. The original blade is subjected to equal-height segmentation, and the height of the winglet is determined by the segmentation number of the blade and is usually 5%-10% of the radial height according to design experience. According to the control parameters, the winglets are divided into three types: suction surface winglets, pressure surface winglets and all-round winglets. The molded line of each winglet is in smooth transition with the molded line of the original blade profile, fine control over the blade tip winglets can be achieved through modeling parameters, and parameterized optimization can be carried out on the shapes of the winglets so as to obtain a good flow control effect.

Description

Technical Field

[0001] The disclosed embodiments relate to the technical field of blade tip winglet design, and more particularly to a method for designing a turbine blade tip winglet based on a droplet-shaped function. Background Art

[0002] During the operation of axial flow turbines, leakage flow will be generated due to the gap between the blades and the casing. This flow usually forms a tip leakage vortex (TLV), which is a strong three-dimensional, unsteady flow structure with high radial and circumferential velocities, low axial velocities and strong turbulent pulsation. The influence of tip leakage flow on turbine performance is significant. Studies have shown that for every 1% increase in clearance height, the efficiency of the turbine stage will decrease 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 of the blade channel. With the increase of modern axial flow turbine load, turbine front temperature and the development of low aspect ratio blades, the negative impact of tip leakage flow / vortex has become increasingly prominent, seriously hindering the further improvement of turbine performance. In order to meet this challenge, researchers have developed a variety of active and passive flow control methods to reduce the adverse effects of tip leakage flow. Tip winglets as an effective passive control method for tip leakage flow have attracted widespread attention from researchers.

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

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

[0005] It should be noted that this section is intended 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 by virtue of being included in this section. Summary of the invention

[0006] The purpose of the embodiments of the present disclosure is to provide a method for designing a turbine blade tip winglet based on a droplet-shaped function, thereby overcoming one or more problems caused by the limitations and defects of the related art at least to a certain extent.

[0007] According to an embodiment of the present disclosure, a method for designing a turbine blade tip winglet based on a droplet-shaped function is provided, the method comprising:

[0008] Acquire the blade tip profile along the radial rotation surface of the blade, and convert the blade tip profile into an initial plane two-dimensional blade profile;

[0009] Based on the initial two-dimensional blade profile, the thickness distribution of the initial two-dimensional blade profile is obtained;

[0010] According to the combined dimensionless parameter group, the starting point and the end point of the suction side winglet and the starting point and the end point of the pressure side winglet of the initial plane two-dimensional blade are determined;

[0011] According to the thickness distribution of the initial two-dimensional blade profile and the droplet shape function, the thickness distribution of the blade tip winglet is obtained;

[0012] According to the thickness distribution of the tip winglet, the starting point and the end point of the suction side winglet of the initial two-dimensional blade shape, and the starting point and the end point of the pressure side winglet, the added pressure side winglet profile line and the suction side winglet profile line are constructed to obtain the tip winglet of the target two-dimensional blade shape;

[0013] Convert the blade tip winglet of the target plane 2D blade profile into the blade tip winglet of the revolving surface.

[0014] Furthermore, the step of obtaining the blade tip profile along the radial rotation surface of the blade and converting the blade tip profile into an initial planar two-dimensional blade profile includes:

[0015] The revolving surface is determined along the radial direction of the blade, the contour curve of the revolving surface is taken as the blade tip profile, and the blade tip profile is converted into an initial plane two-dimensional blade profile.

[0016] Furthermore, the dimensionless parameter group includes:

[0017] Suction side winglet starting position W SS , suction surface winglet end position W SE 、Starting position of pressure winglet W PS and the pressure winglet end position W PE .

[0018] Furthermore, based on the initial two-dimensional blade profile, the step of obtaining the thickness distribution of the initial two-dimensional blade profile includes:

[0019] The pressure surface profile line and the suction surface profile line of the initial two-dimensional blade body are offset multiple times with equal distances to generate a plurality of intersection points; wherein the number of the intersection points is 1-2;

[0020] Arrange the point set composed of the intersection points in axial order to obtain the median camber line of the initial two-dimensional blade profile;

[0021] With the point on the mid-arc line as the center, make an inscribed circle of the blade to obtain the thickness distribution of the initial two-dimensional blade.

[0022] Further, the step of determining the starting point and the end point of the suction surface winglet and the starting point and the end point of the pressure surface winglet of the initial planar two-dimensional blade profile in combination with the dimensionless parameter group includes:

[0023] Set the starting position of the suction surface winglet multiplied by the axial chord length as the axial distance from the starting point of the suction surface winglet to the leading edge point;

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

[0025] Set the starting position of the pressure surface winglet multiplied by the axial chord length as the axial distance from the starting point of the pressure surface winglet to the leading edge point;

[0026] Set the axial distance from the end point of the pressure surface winglet to the leading edge point as the end point of the pressure surface winglet multiplied by the axial chord length;

[0027] According to the axial distance from the starting point of the suction surface winglet to the leading edge point and the axial distance from the ending point of the suction surface winglet to the leading edge point, the starting position of the suction surface winglet and the ending position of the suction surface winglet are obtained;

[0028] According to the axial distance from the starting point to the leading edge point of the pressure surface winglet and the axial distance from the end point to the leading edge point of the pressure surface winglet, the starting position and the end point of the pressure surface winglet are obtained.

[0029] Furthermore, the expression for the starting position of the suction surface winglet is:

[0030] W SS =L SS / C x

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

[0032] W SE =L SE / C x

[0033] The expression for the initial position of the pressure winglet is:

[0034] W PS =L PS / C x

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

[0036] W PE =L PE / C x

[0037] Among them, L SS L is the axial distance from the starting point of the suction winglet to the leading edge point, SE L is the axial distance from the end point of the suction surface winglet to the leading edge point, PS L is the axial distance from the starting point of the pressure winglet to the leading edge point, PE C is the axial distance from the end point of the pressure surface winglet to the leading edge point,x is the axial chord length.

[0038] Furthermore, the expression of the water droplet function is:

[0039]

[0040] Where x is the radial position of the blade tip, y is the circumferential position, θ is the azimuth angle of the discrete point, and a is the coefficient of the droplet shape function, which is a constant;

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

[0042] L i = l i ×f(x)

[0043] Among them, l i is the thickness distribution of the initial two-dimensional blade profile.

[0044] Further, according to the thickness distribution of the tip winglet, the starting point and the end point of the suction surface winglet of the initial two-dimensional blade profile, and the starting point and the end point of the pressure surface winglet, the added pressure surface winglet profile line and the suction surface winglet profile line are constructed to obtain the tip winglet of the target two-dimensional blade profile, including:

[0045] Based on the starting position of the suction winglet to the end position of the suction winglet, combined with the thickness distribution of the tip winglet, the added suction winglet profile is constructed using the mid-camber thickness superposition method;

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

[0047] According to the added suction surface airfoil line and the added pressure surface airfoil line, the tip winglet of the target plane two-dimensional blade shape is obtained.

[0048] Furthermore, the step of converting the blade tip winglet of the target plane two-dimensional blade profile into the blade tip winglet of the revolving surface includes:

[0049] Convert the blade tip winglet of the target plane two-dimensional blade shape into the blade tip winglet of the revolving surface;

[0050] The tip blade profile is replaced by the tip winglet of the revolving surface to generate a new blade.

[0051] Furthermore, the final blade tip winglet height of the rotating surface obtained by coordinate transformation is 5%-10% of the radial height of the blade.

[0052] The technical solution provided by the embodiments of the present disclosure may have the following beneficial effects:

[0053] In the embodiment of the present disclosure, through the above-mentioned turbine tip winglet design method based on the water droplet function, on the one hand, the discrete point coordinates of the tip blade profile are obtained along the radial rotation surface of the blade, and the rotation surface blade profile can be converted into a plane two-dimensional blade profile through coordinate transformation, and then the mid-camber line and thickness distribution of the two-dimensional blade profile are solved. The thickness distribution of the tip winglet is constructed using the dimensionless parameters controlling the shape of the winglet and the water droplet function, and the profile of the tip winglet can be obtained by superimposing the mid-camber line thickness. The two-dimensional blade profile after adding the tip winglet is converted into the rotation surface blade profile through the second coordinate transformation. On the other hand, the use of the water droplet function can achieve a smooth transition between the winglet profile line and the original blade profile line, meeting the engineering requirements of the tip winglet. In addition, the precise control of details such as the position and thickness of the tip winglet can be achieved through a small number of dimensionless parameters, and it is ensured that no unreasonable geometric shapes will appear. In the optimization design process, no additional constraints need to be set, thereby realizing a flexible and efficient optimization process. The method is suitable for the design process of the tip winglet of axial flow turbine blades for various purposes, and has a good control effect on the tip leakage flow of turbine blades. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] The accompanying drawings herein are incorporated into the specification and constitute a part of the specification, illustrate embodiments consistent with the present disclosure, and together with the specification are used to explain the principles of the present disclosure. Obviously, the accompanying drawings described below are only some embodiments of the present disclosure, and for ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without creative work.

[0055] Figure 1 A step diagram showing a method for designing a turbine blade tip winglet based on a droplet-shaped function in an exemplary embodiment of the present disclosure;

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

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

[0058] Figure 4 A schematic diagram showing 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 showing a suction surface winglet, a pressure surface winglet and a full-circumference winglet in an exemplary embodiment of the present disclosure;

[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 A blade geometry schematic diagram showing a turbine blade of a certain stage in an exemplary embodiment of the present disclosure, where 5% of the blade height H is intercepted along the blade tip;

[0062] Figure 8 A schematic diagram showing the control effect of a three-dimensional blade with a winglet structure added on the tip leakage flow in an exemplary embodiment of the present disclosure;

[0063] Fig. 9 A schematic structural diagram of a blade tip winglet in an exemplary embodiment of the present disclosure is shown. DETAILED DESCRIPTION

[0064] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments can be implemented in a variety of forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that the disclosure will be more comprehensive and complete and to fully convey the concepts of the example embodiments to those skilled in the art. The described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0065] In addition, the accompanying drawings are only schematic illustrations of the embodiments of the present disclosure and are not necessarily drawn to scale. The same reference numerals in the figures represent the same or similar parts, and their repeated descriptions will be omitted. Some of the block diagrams shown in the accompanying drawings are functional entities and do not necessarily correspond to physically or logically independent entities.

[0066] This example embodiment provides a turbine blade tip winglet design method based on a droplet shape function. Figure 1 As shown in , the turbine blade tip winglet design method based on the water droplet function may include: steps S101 to S106.

[0067] Step S101: Acquire the blade tip profile along the radial rotation surface of the blade, and convert the blade tip profile into an initial two-dimensional blade profile;

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

[0069] Step S103: determining the starting point and the end point of the suction side winglet and the starting point and the end point of the pressure side winglet of the initial two-dimensional blade profile according to the combined dimensionless parameter group;

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

[0071] Step S105: constructing the added pressure surface winglet profile line and suction surface winglet profile line according to the thickness distribution of the tip winglet, the starting point and end point of the suction surface winglet of the initial two-dimensional blade profile, and the starting point and end point of the pressure surface winglet, so as to obtain the tip winglet of the target two-dimensional blade profile;

[0072] Step S106: converting the blade tip winglet of the target plane two-dimensional blade profile into a blade tip winglet of the revolving surface.

[0073] Through the above-mentioned turbine tip winglet design method based on the water droplet function, on the one hand, the discrete point coordinates of the tip blade profile are obtained along the radial rotation surface of the blade, and the rotation surface blade profile can be converted into a plane two-dimensional blade profile through coordinate transformation, and then the mid-camber line and thickness distribution of the two-dimensional blade profile are solved. The thickness distribution of the tip winglet is constructed using the dimensionless parameters that control the shape of the winglet and the water droplet function, and the profile of the tip winglet can be obtained by superimposing the mid-camber line thickness. The two-dimensional blade profile after adding the tip winglet is converted into the rotation surface blade profile through the second coordinate transformation. On the other hand, the water droplet function can achieve a smooth transition between the winglet profile line and the original blade profile line, meeting the engineering requirements of the tip winglet. In addition, a small number of dimensionless parameters can be used to achieve precise control of details such as the position and thickness of the tip winglet, and ensure that no unreasonable geometric shapes will appear. In the optimization design process, no additional constraints need to be set, thereby achieving a flexible and efficient optimization process. This method is suitable for the design process of the tip winglet of axial flow turbine blades for various purposes, and has a good control effect on the tip leakage flow of turbine blades.

[0074] Next, we will refer to Figures 1 to 9 Each step of the above-mentioned method for designing a turbine blade tip winglet based on a water droplet shape function in this example embodiment is described in more detail.

[0075] In step S101, a blade tip profile is acquired along a radial rotation surface of the blade, and the blade tip profile is converted into an initial two-dimensional blade profile.

[0076] Specifically, the blade tip profile is obtained along the radial rotation surface of the blade, and the rotation surface profile (i.e., blade tip profile) is converted into a two-dimensional blade profile. Taking the cylindrical rotation surface as an example, the coordinates of the discrete points of the rotation surface profile are (x, y, z), and the coordinates of the discrete points of the two-dimensional blade profile are (r, θ, z). The coordinate transformation satisfies: θ=arctan(x / y), where x is the radial position of the blade profile on the rotating surface, y is the circumferential position, z is the axial position of the blade profile, r is the radius of the cylindrical coordinate system, and θ is the azimuth angle of the discrete point, ranging from 0 to 2π. The obtained two-dimensional blade profile on the blade tip plane can be found in Figure 2 .

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

[0078] Specifically, the mid-camber line and thickness distribution of the two-dimensional blade are solved, and the starting point and end point of the suction side and pressure side winglets are determined by four dimensionless parameters. The dimensionless parameters can be named W SS , W SE , W PS , W PE The naming rules are as follows: W is the first letter of the winglet, the first letter S is the first letter of the suction surface, P is the first letter of the pressure surface, the second letter S is the first letter of the starting point, and E is the first letter of the end point.

[0079] More specifically, the pressure surface and suction surface profiles of the two-dimensional blade are offset multiple times at equal intervals. 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, and the curve formed is the center arc of the blade. See the attached Figure 3 , with the point on the mid-arc as the center, make the inscribed circle of the blade. The thickness distribution of the two-dimensional blade can be determined by the radius of these circles. Figure 3 .

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

[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 droplet-shaped function; according to the thickness distribution of the tip winglet, the starting point and end point of the suction surface winglet of the initial planar two-dimensional blade profile, and the starting point and end point of the pressure surface winglet, the added pressure surface winglet profile line and the suction surface winglet profile line are constructed to obtain the tip winglet of the target planar two-dimensional blade profile.

[0082] Specifically, when the starting and ending positions of the winglet are determined, the water droplet-shaped function f(x) (see Figure 3 ) The thickness distribution of the winglet along the normal direction of the mid-camber line is L i (See Figure 4 ), the thickness distribution of the winglet L i Thickness distribution of the original blade i Satisfies the following relationship: L i = l i ×f(x), and then the pressure and suction airfoil profiles of the two-dimensional blade are constructed by superimposing the thickness of the mid-camber lines.

[0083] More specifically, the thickness distribution of the winglet is constructed from the starting point to the end point of the winglet. The thickness at the starting point and the end point corresponds to the thickness at the corresponding position of the original two-dimensional blade profile. The thickness distribution of the remaining winglet part is obtained by multiplying the thickness value of the corresponding range position of the original blade profile by the teardrop-shaped function. In this way, it can be ensured that the winglet profile line intersects with the original blade profile line at the starting point and the end point, and a smooth transition is achieved, thereby ensuring that the tip winglet has good aerodynamic performance.

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

[0085] In step S106, the blade tip winglet of the target plane two-dimensional blade profile (see Figure 5 ) is converted into a blade tip winglet on the rotating surface. Among them, adding a winglet only to the pressure surface is called a pressure surface winglet; adding a winglet only to the suction surface is called a suction surface winglet; adding a suction surface winglet and a pressure surface winglet to the target blade shape at the same time is called a full-circle winglet.

[0086] Specifically, the two-dimensional blade profile after adding the tip winglet is converted into a revolved surface blade profile. Taking the cylindrical revolved 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. The final result can be obtained after the second coordinate transformation.

[0087] Replace the tip blade shape of the original three-dimensional blade with the blade shape of the rotating surface after adding the blade tip winglet to generate a new blade. Figure 6 .

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

[0089] like Fig. 9 The figure shows the schematic diagram of the structure of the blade tip winglet.

[0090] Through the above-mentioned turbine tip winglet design method based on the water droplet function, on the one hand, the discrete point coordinates of the tip blade profile are obtained along the radial rotation surface of the blade, and the rotation surface blade profile can be converted into a plane two-dimensional blade profile through coordinate transformation, and then the mid-camber line and thickness distribution of the two-dimensional blade profile are solved. The thickness distribution of the tip winglet is constructed using the dimensionless parameters that control the shape of the winglet and the water droplet function, and the profile of the tip winglet can be obtained by superimposing the mid-camber line thickness. The two-dimensional blade profile after adding the tip winglet is converted into the rotation surface blade profile through the second coordinate transformation. On the other hand, the water droplet function can achieve a smooth transition between the winglet profile line and the original blade profile line, meeting the engineering requirements of the tip winglet. In addition, a small number of dimensionless parameters can be used to achieve precise control of details such as the position and thickness of the tip winglet, and ensure that no unreasonable geometric shapes will appear. In the optimization design process, no additional constraints need to be set, thereby achieving a flexible and efficient optimization process. This method is suitable for the design process of the tip winglet of axial flow turbine blades for various purposes, and has a good control effect on the tip leakage flow of turbine blades.

[0091] It should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like in the above description indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present disclosure and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the embodiments of the present disclosure.

[0092] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may 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 clearly and specifically defined.

[0093] In the embodiments of the present disclosure, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; 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 connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present disclosure can be understood according to specific circumstances.

[0094] In the embodiments of the present disclosure, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may include the first and second features not being in direct contact but being in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes the first feature being directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes the first feature being directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

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

[0096] Those skilled in the art will readily appreciate other embodiments of the present disclosure after considering the specification and practicing the invention disclosed herein. This application is intended to cover any modification, use or adaptation of the present disclosure, which follows the general principles of the present disclosure and includes common knowledge or customary techniques in the art that are not disclosed in the present disclosure. The specification and examples are intended to be exemplary only, and the true scope and spirit of the present disclosure are indicated by the appended claims.

Claims

1. A method for designing a turbine blade tip winglet based on a droplet-shaped function, characterized in that: The method includes: Acquire the blade tip profile along the radial rotation surface of the blade, and convert the blade tip profile into an initial plane two-dimensional blade profile; Based on the initial two-dimensional blade profile, the thickness distribution of the initial two-dimensional blade profile is obtained; According to the combined dimensionless parameter group, the starting point and the end point of the suction side winglet and the starting point and the end point of the pressure side winglet of the initial plane two-dimensional blade are determined; According to the thickness distribution of the initial two-dimensional blade profile and the droplet shape function, the thickness distribution of the blade tip winglet is obtained; According to the thickness distribution of the tip winglet, the starting point and the end point of the suction side winglet of the initial two-dimensional blade shape, and the starting point and the end point of the pressure side winglet, the added pressure side winglet profile line and the suction side winglet profile line are constructed to obtain the tip winglet of the target two-dimensional blade shape; Convert the blade tip winglet of the target plane 2D blade profile into the blade tip winglet of the revolving surface.

2. The method for designing a turbine blade tip winglet based on a water droplet shape function according to claim 1, characterized in that: The step of obtaining the blade tip profile along the radial rotation surface of the blade and converting the blade tip profile into an initial plane two-dimensional blade profile includes: The revolving surface is determined along the radial direction of the blade, the contour curve of the revolving surface is taken as the blade tip profile, and the blade tip profile is converted into an initial plane two-dimensional blade profile.

3. The method for designing a turbine blade tip winglet based on a water droplet shape function according to claim 1, characterized in that: The dimensionless parameter group includes: Suction side winglet starting position W SS , suction surface winglet end position W SE 、Starting position of pressure winglet W PS and the pressure winglet end position W PE .

4. The method for designing a turbine blade tip winglet based on a water droplet shape function according to claim 3, characterized in that: The step of obtaining the thickness distribution of the initial two-dimensional blade profile based on the initial two-dimensional blade profile includes: The pressure surface profile line and the suction surface profile line of the initial two-dimensional blade body are offset multiple times with equal distances to generate a plurality of intersection points; wherein the number of the intersection points is 1-2; The point set composed of the intersection points is arranged in axial order to obtain the median camber line of the initial two-dimensional blade profile; With the point on the mid-arc line as the center, make an inscribed circle of the blade to obtain the thickness distribution of the initial two-dimensional blade.

5. The method for designing a turbine blade tip winglet based on a water droplet shape function according to claim 4, characterized in that: The step of determining the starting point and the end point of the suction side winglet and the starting point and the end point of the pressure side winglet of the initial two-dimensional blade profile according to the combination of the dimensionless parameter group includes: Set the starting position of the suction surface winglet multiplied by the axial chord length as the axial distance from the starting point of the suction surface winglet to the leading edge point; Set the axial distance from the suction surface winglet end point to the leading edge point as the end point position of the suction surface winglet multiplied by the axial chord length; Set the starting position of the pressure surface winglet multiplied by the axial chord length as the axial distance from the starting point of the pressure surface winglet to the leading edge point; Set the axial distance from the end point of the pressure surface winglet to the leading edge point as the end point of the pressure surface winglet multiplied by the axial chord length; According to the axial distance from the starting point of the suction surface winglet to the leading edge point and the axial distance from the ending point of the suction surface winglet to the leading edge point, the starting position of the suction surface winglet and the ending position of the suction surface winglet are obtained; According to the axial distance from the starting point to the leading edge point of the pressure surface winglet and the axial distance from the end point to the leading edge point of the pressure surface winglet, the starting position and the end point of the pressure surface winglet are obtained.

6. The method for designing a turbine blade tip winglet based on a water droplet shape function according to claim 5, characterized in that: The expression for the starting position of the suction side winglet is: W SS =L SS / C x The expression for the end position of the suction side winglet is: W SE =L SE / C x The expression for the initial position of the pressure winglet is: W PS =L PS / C x The expression for the end position of the pressure side winglet is: W PE =L PE / C x Among them, L SS L is the axial distance from the starting point of the suction winglet to the leading edge point, SE L is the axial distance from the end point of the suction surface winglet to the leading edge point, PS L is the axial distance from the starting point of the pressure winglet to the leading edge point, PE C is the axial distance from the end point of the pressure surface winglet to the leading edge point, x is the axial chord length.

7. The method for designing a turbine blade tip winglet based on a water droplet shape function according to claim 6, characterized in that: The expression of the teardrop-shaped function is: Where x is the radial position of the blade tip, y is the circumferential position, θ is the azimuth angle of the discrete point, and a is the coefficient of the droplet shape function, which is a constant; The expression of the thickness distribution of the blade tip winglet is: L i =l i ×f(x) Among them, l i is the thickness distribution of the initial two-dimensional blade profile.

8. The method for designing a turbine blade tip winglet based on a water droplet shape function according to claim 7, characterized in that: The step of constructing an added pressure surface winglet profile line and a suction surface winglet profile line according to the thickness distribution of the tip winglet, the starting point and the end point of the suction surface winglet of the initial two-dimensional blade profile, and the starting point and the end point of the pressure surface winglet to obtain the tip winglet of the target two-dimensional blade profile includes: Based on the starting position of the suction winglet to the end position of the suction winglet, combined with the thickness distribution of the tip winglet, the added suction winglet profile is constructed using the mid-camber thickness superposition method; Based on the starting position of the pressure surface winglet to the end position of the pressure surface winglet, combined with the thickness distribution of the blade tip winglet, the added pressure surface winglet profile is obtained by using the mid-camber thickness superposition method; According to the added suction surface airfoil line and the added pressure surface airfoil line, the tip winglet of the target plane two-dimensional blade shape is obtained.

9. The method for designing a turbine blade tip winglet based on a water droplet shape function according to claim 8, characterized in that: The step of converting a blade tip winglet of a target plane two-dimensional blade profile into a blade tip winglet of a revolving surface comprises: Convert the blade tip winglet of the target plane two-dimensional blade shape into the blade tip winglet of the revolving surface; The tip blade profile is replaced by the tip winglet of the revolving surface to generate a new blade.

10. The method for designing a turbine blade tip winglet based on a water droplet shape function according to claim 9, characterized in that: The final blade tip winglet height of the rotating surface obtained by coordinate transformation is 5%-10% of the blade radial height.

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