Fine modification method for rotor blade tip of turbomachinery

Abstract

The invention relates to a refined modification method for a rotor blade tip of a turbomachine, which comprises the following steps of: realizing geometric circumferential and radial blade tip modification of the rotor blade tip by changing design parameters corresponding to control points of geometric circumferential and radial modification arcs of the rotor blade tip, and realizing refined modification of the blade tip of the rotor blade tip by changing primary functions of an upper molded line and a lower molded line and coefficient values of the primary functions. According to the method, the blade tip shaping in the geometric axial direction of the rotor blade tip is achieved, the blade tip geometry step of thinning under different rotor blade tip gaps and DOE test design are obtained, and finally the blade tip thinning or winglet adding scheme for optimizing the gap effect, flow separation and loss problems caused by the gas compressor gaps is determined. By means of blade tip modification, flow separation caused by secondary flow such as blade tip leakage vortex is controlled, flow loss is reduced, rotor blade tip leakage flow is better weakened, flow blockage of the blade tip is reduced, the flow condition in a gas compressor / turbine is improved, and then the purposes of greatly improving the stall margin, efficiency and pressure ratio of the gas compressor / turbine are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of impeller machinery, and in particular to a method for fine-tuning the shape of a rotor blade tip. Background Art

[0002] The tip clearance of the rotor in an axial-flow compressor / turbine is designed to prevent collisions between the rotating rotor blades and the casing wall. The geometric dimensions of the tip clearance between the rotor blade tip and the casing are very small compared to the overall flow path. Generally speaking, the tip clearance is approximately 0.5% to 5% of the blade height. Both transient and prolonged engine operation can cause changes in the compressor / turbine rotor tip clearance. The former is due to blade shape deformation caused by changes in workload, while the latter is due to blade surface wear caused by prolonged operation. Thermal expansion of the casing can also cause changes in the clearance. Furthermore, in small-sized axial-flow compressors / turbines, the rotor tip clearance cannot be reduced as blade height decreases, resulting in a relatively large radial proportion of the tip clearance.

[0003] Tip leakage flow is caused by the pressure difference across the blades, typically existing in the form of a tip leakage vortex in the blade tip area. It affects the flow within the blade flow path, approximately 20% of the casing. The most significant impact of increased tip clearance is the increase in the range and intensity of tip leakage flows / vortices, secondary flows, and multiple leakage flows. Rotor tip leakage also significantly impacts compressor / turbine pressure rise, efficiency, stability, vibration, and noise characteristics.

[0004] According to existing literature, for every 1% increase in blade tip clearance, blade efficiency decreases by 1.5%. However, for every 1% decrease in efficiency, the fuel consumption of the aircraft engine increases by 2%. To mitigate the impact of tip leakage on compressor / turbine performance, many researchers have sought to modify the rotor tip profile through tip shaping (including tip winglets and blade thinning), and explored potential passive control methods for tip clearance leakage. However, a universally applicable rotor tip refinement method is currently lacking. Summary of the Invention

[0005] The purpose of the present invention is to avoid the shortcomings of the existing technology and provide a method for fine-tuning the blade tips of impeller machinery rotors with wide applicability, which can weaken the blade tip leakage flow of the rotor, reduce the flow blockage at the blade top, and improve the flow conditions inside the compressor / turbine through blade tip shaping.

[0006] To achieve the above-mentioned purpose, the technical solution adopted by the present invention is: a method for fine-tuning the blade tip of a turbomachinery rotor, comprising the following steps: Step 1: Using a B-spline curve as a fitting control line for the rotor blade tip modification arc, multiple control points are arranged at equal distances on the pressure side and suction side of the rotor blade along the fitting control line. At the same time, a radial starting position control point for controlling the blade tip modification is given, and the design parameters corresponding to the control point are recorded as the blade tip geometric circumferential and radial parameters of the rotor blade, thereby obtaining the rotor blade tip geometric circumferential and radial modification arcs controlled by the curve fitting; By changing the design parameters corresponding to the control points of the circumferential and radial modification arcs of the rotor blade tip geometry, the circumferential and radial modification of the rotor blade tip geometry can be achieved; Step 2: Based on the upper and lower profiles of the rotor blade tip cross-section, the basis functions of the upper and lower profiles of the rotor blade tip axial direction controlled by curve fitting are constructed based on the Hicks-Henne method. The basis functions and basis function coefficients of the upper and lower profiles are converted into design parameters of the rotor blade tip axial direction, and the thickness distribution of the profile lines is controlled by the design parameters. By changing the basis functions and basis function coefficients of the upper and lower profiles, the blade tip is modified in the axial direction of the rotor blade tip geometry, and thinned blade tip geometry is obtained under different rotor blade tip clearances. Step 3. Perform DOE experimental design based on the basis function coefficients corresponding to the thinned blade tip geometry and the control points of the circumferential and radial modification arcs of the rotor blade tip geometry to obtain the influence of the modified blade tip geometry on the blade efficiency, pressure ratio and stall margin rotor performance, and finally determine the blade tip thinning or winglet addition scheme to optimize the gap effect, flow separation and loss problems caused by the compressor clearance.

[0007] Furthermore, in step 1, three control points are arranged at equal distances on the pressure side and the suction side of the rotor blade.

[0008] Furthermore, the step 1 is specifically as follows: Step 1.1: Define the first control point of the rotor blade tip pressure surface as Span_PS1 and the first control point of the rotor blade tip suction surface as Span_SS1. Span_PS1 and Span_SS1 are the relative positions of the first control points of the rotor blade tip modification. The radial positions of the two are consistent with the prototype blade. When the initial values ​​of Span_PS1 and Span_SS1 are set to 1, it means that the circumferential positions of the first and second control points are consistent. At the same time, define the second control point of the rotor blade tip pressure surface as Span_PS2 and the second control point of the rotor blade tip suction surface as Span_SS2. Span_PS2 and Span_SS2 are the relative positions of the first control point to the second control point along the arc. When the initial values ​​of Span_PS2 and Span_SS2 are 0, it means that the circumferential positions of the second control point and the first control point are consistent. When the initial values ​​of Span_PS2 and Span_SS2 are 1, it means that the circumferential positions of the second control point and the third control point are consistent. Similarly, define the third control point of the rotor blade tip pressure surface as Span_PS3 and the third control point of the suction surface as Span_SS3. Span_PS3 and Span_PS3 are the relative positions of the second control point along the arc to the third control point. When the initial values ​​of Span_PS3 and Span_PS3 are 0, it means that the circumferential positions of the third control point and the second control point are consistent. When the initial values ​​of Span_PS3 and Span_SS3 are set to 1, it means that there is no modification of the rotor blade tip geometry. Step 1.2, define the radial starting position control point for controlling the rotor tip modification as Span_S7, and in the radial direction of the rotor tip modification, the positions of the Span_PS1 and Span_SS1 control points are consistent, the positions of the Span_PS2 and Span_SS2 control points are consistent, and the positions of the Span_PS3 and Span_SS3 control points are consistent; Thus, the geometric circumferential and radial modification arcs of the rotor blade tip controlled by seven design parameters were constructed.

[0009] Furthermore, the maximum cutting values ​​Max Span_PS1-3 and Max Span SS1-3 of the corresponding positions of the three control points Span_PS1-3 on the pressure surface of the rotor blade tip and the three control points Span_SS1-3 on the suction surface of the rotor blade tip are 1, and the minimum cutting values ​​Min Span_PS1-3 and Min Span SS1-3 are 0; Meanwhile, the minimum value of Span_S7 is 90% of the blade height, and the maximum value is 100% of the blade height.

[0010] Furthermore, the step 2 is specifically as follows: Let the upper and lower profiles of the blade tip section be y o,up and y o,low , which represent the suction side and pressure side of the rotor blade respectively; Then, based on the Hicks-Henne method, a smooth basis function is superimposed on the smooth function to ensure the geometric smoothness of the controlled blade profile. Then, the leaf shape expression is obtained as: 0≤x≤1, Where y up is the upper mold line; y low is the lower mold line; f k (x) is the kth basis function; x is the relative chord length of the blade; SS k is the basis function coefficient of the upper profile; PS k is the basis function coefficient of the lower profile; Among them, the basis function f k (x) is expressed as: , Where x k is the relative chord length corresponding to the peak value of the basis function; By changing the basis function coefficient SS of the upper mold line in the formula k , basis function coefficient PS of lower profile k , the relative chord length x corresponding to the basis function peak k The value of is the axial design parameter of the rotor blade tip, thereby realizing the control of the upper and lower profiles of the blade.

[0011] Furthermore, the basis function and basis function coefficient SS are selected according to the target requirements. k and the basis function coefficients PS of the lower profile k The number of basis functions selected is 4-9, corresponding to the basis function coefficients SS1~SS9, PS1~PS 9， A total of 8 to 18 items were selected.

[0012] Furthermore, based on the distribution of the cross-sectional twist angle of the rotor blade tip, six basis functions are iterated to parameterize and control the axial blade profile of the rotor blade tip; Assuming k = 1, 2, 3, 4, 5, 6, the relative chord length x corresponding to the basis function peak is k are 0.1, 0.3, 0.5, 0.7, 0.85 and 0.94 respectively. When x=0 or 1, f k (x) = 0, which meets the requirement that the leading and trailing edge positions of the blade remain unchanged after axial modification; At this time, the basis function coefficients of the upper profile are SS1~SS6 and the basis function coefficients of the lower profile are PS1~PS6, with a total of 12 design parameters. When a positive value is taken, a tip winglet is added, and when a negative value is taken, the tip of the blade is thinned. The parameters are selected according to the design requirements and actual conditions.

[0013] Furthermore, the axial design parameters of the rotor blade tip do not exceed 20% of the blade thickness at the corresponding position, so as to prevent excessive changes in axial thinning from causing structural problems due to the thin tip of the blade, thereby achieving unilateral, bilateral, uniform and non-uniform thinning of the blade in the circumferential, radial and axial directions.

[0014] Furthermore, the DOE experimental design is based on the design parameters corresponding to the control points of the geometric circumferential and radial modification arcs of the rotor blade tip as two-level factors, and the basis functions and basis function coefficients of the upper and lower profiles converted into the design parameters of the rotor blade tip axial direction as three-level factors, to generate a mixed level factor DOE experimental design table.

[0015] Furthermore, the design gap of the DOE experimental design is 0.2 mm to 0.6 mm.

[0016] The beneficial effects of the present invention are: based on the design concept of various types of rotor blade tip modification, the present invention aims at the lack of a universally applicable rotor blade tip parametric modification method. Through blade tip modification, the flow separation caused by secondary flows such as blade tip leakage vortex is controlled and the flow loss is reduced, so as to better weaken the blade tip leakage flow of the rotor, reduce the flow blockage of the blade top, improve the flow condition inside the compressor / turbine, and thus achieve the purpose of greatly improving the compressor / turbine stall margin and improving the compressor / turbine efficiency and compression ratio, meet the urgent needs of stable operation of the compressor / turbine, and have important significance for indicators such as the fuel consumption rate and thrust-to-weight ratio of the whole machine. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 It is a schematic diagram of the parametric design for rotor blade tip modification in the present invention; Figure 2 is a Hicks-Henne basis function distribution diagram for rotor blade tip modification in the present invention; Figure 3 This is a schematic diagram of the shape of the blade tip winglet after adopting the design method of the present invention; Figure 4 This is a schematic diagram of the axial thinning effect of a certain blade section after adopting the design method of the present invention; Figure 5 This is the technical roadmap for the research of blade tip thinning scheme based on Taguchi DOE in this invention; Figure 6 This is a diagram of the DOE experimental design table (L-36 OA) of the Taguchi mixed level factor in the research technical route of the blade tip thinning solution based on Taguchi DOE in the present invention; FIG7 is a blade profile diagram of a 100% blade height cross section of a modified rotor with blade tip thinning after adopting the design method of the present invention; Figure 8The characteristic line diagrams of the prototype and DOE thinning scheme under different blade tip clearances after adopting the design method of the present invention are shown; Figure 9 This is the static pressure distribution diagram at the position of 0.99 blade height near the stall point under the design clearance after adopting the design method of the present invention; Figure 10 This is a relative velocity distribution diagram of leakage flow near the stall point under the designed clearance after adopting the design method of the present invention; Figure 11 This is the axial velocity distribution diagram near the design point under large gap of the prototype and DOE thinning scheme after adopting the design method of the present invention; Figure 12 This is the axial velocity distribution diagram of the near-stall point under large clearance of the prototype after adopting the design method of the present invention and the DOE thinning solution; Figure 13 This is the inlet relative airflow angle distribution diagram near the stall point under large gap of the prototype after adopting the design method of the present invention and the DOE thinning solution; Figure 14 This is the relative velocity distribution diagram of the leakage flow near the stall point under large gap after the prototype and DOE thinning scheme using the design method of the present invention. DETAILED DESCRIPTION

[0017] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0018] In order to achieve the above object, the present invention provides the following specific implementation methods: Figure 1 As shown, a method for fine-tuning the blade tip of a turbomachinery rotor comprises the following steps: S01. Use the B-spline curve as the fitting control line of the rotor blade tip modification arc, and arrange three control points at equal distances on the pressure side and suction side of the rotor blade along the fitting control line. Specifically, Figure 1 As shown, the first control point of the rotor blade tip pressure surface is defined as Span_PS1 and the first control point of the rotor blade tip suction surface is defined as Span_SS1. Span_PS1 and Span_SS1 are the relative positions of the first control points of the rotor blade tip modification. The radial positions of the two are consistent with the prototype blade. When the initial values ​​of Span_PS1 and Span_SS1 are set to 1, it means that the circumferential positions of the first control point and the second control point are consistent. At the same time, define the second control point of the rotor blade tip pressure surface as Span_PS2 and the second control point of the rotor blade tip suction surface as Span_SS2. Span_PS2 and Span_SS2 are the relative positions of the first control point to the second control point along the arc. When the initial values ​​of Span_PS2 and Span_SS2 are 0, it means that the circumferential positions of the second control point and the first control point are consistent. When the initial values ​​of Span_PS2 and Span_SS2 are 1, it means that the circumferential positions of the second control point and the third control point are consistent. Similarly, define the third control point of the rotor blade tip pressure surface as Span_PS3 and the third control point of the suction surface as Span_SS3. Span_PS3 and Span_PS3 are the relative positions of the second control point along the arc to the third control point. When the initial values ​​of Span_PS3 and Span_PS3 are 0, it means that the circumferential positions of the third control point and the second control point are consistent. When the initial values ​​of Span_PS3 and Span_SS3 are set to 1, it means that there is no modification of the rotor blade tip geometry. Among them, the maximum cutting values ​​Max Span_PS1-3 and Max Span SS1-3 corresponding to the three control points Span_PS1-3 on the rotor blade tip pressure surface and the three control points Span_SS1-3 on the rotor blade tip suction surface are 1, and the minimum cutting values ​​MinSpan_PS1-3 and Min Span SS1-3 are 0.

[0019] S02. Define the radial starting position control point for controlling the rotor tip modification as Span_S7, and in the radial direction of the rotor tip modification, the positions of the Span_PS1 and Span_SS1 control points are consistent, the positions of the Span_PS2 and Span_SS2 control points are consistent, and the positions of the Span_PS3 and Span_SS3 control points are consistent; Among them, the minimum value of Span_S7 is 90% of the blade height, and the maximum value is 100% of the blade height.

[0020] Thus, the construction of the circumferential and radial modification arcs of the rotor blade tip geometry controlled by 7 design parameters is completed; by changing the design parameters corresponding to the control points of the circumferential and radial modification arcs of the rotor blade tip geometry, the circumferential and radial blade tip modification of the rotor blade tip geometry is achieved.

[0021] S03, let the upper and lower profiles of the blade tip section be y o,up and y o,low , which represent the suction side and pressure side of the rotor blade respectively; Then, based on the Hicks-Henne method, a smooth basis function is superimposed on the smooth function to ensure the geometric smoothness of the controlled blade profile. Then, the leaf shape expression is obtained as: 0≤x≤1, Where y up is the upper mold line; y low is the lower mold line; f k (x) is the kth basis function; x is the relative chord length of the blade; SS k is the basis function coefficient of the upper profile; PS k is the basis function coefficient of the lower profile; Among them, the basis function f k (x) is expressed as: , Where x k is the relative chord length corresponding to the peak value of the basis function; By changing the basis function coefficient SS of the upper mold line in the formula k , basis function coefficient PS of lower profile k , the relative chord length x corresponding to the basis function peak k The value of is the design parameter of the rotor blade tip in the axial direction, thereby realizing the control of the upper and lower profiles of the blade, that is, realizing the axial blade tip modification of the rotor blade tip geometry, and obtaining the thinned blade tip geometry under different rotor blade tip clearances.

[0022] S04. The DOE experimental design is based on the design parameters corresponding to the control points of the circumferential and radial modification arcs of the rotor blade tip geometry as two-level factors, and the design parameters of the rotor blade tip axial direction converted from the basis functions and basis function coefficients of the upper and lower profiles as three-level factors, generating a mixed-level factor DOE experimental design table. The design gap of the DOE experimental design is 0.2mm-0.6mm; The influence of modified blade tip geometry on blade efficiency, pressure ratio and stall margin rotor performance is obtained, and finally the blade tip thinning or winglet addition scheme is determined to optimize the gap effect, flow separation and loss problems caused by compressor clearance.

[0023] Example 2: Same as Example 1, except that in S03, the basis function and basis function coefficient SS are selected according to the target requirements. k and the basis function coefficients PS of the lower profile k The number of basis functions selected is 4-9, corresponding to the basis function coefficients SS1~SS9, PS1~PS 9， A total of 8 to 18 items were selected.

[0024] At the same time, the axial design parameters of the rotor blade tip do not exceed 20% of the blade thickness at the corresponding position, which is used to prevent excessive changes in axial thinning from causing structural problems due to the thin tip of the blade, thereby achieving single-sided, double-sided, uniform and non-uniform thinning of the blade in the circumferential, radial and axial directions.

[0025] like Figures 1-14 In order to further illustrate the present invention, the following specific examples are provided: Specific example 1: Preliminary research has shown that rotor tip thinning can, to a certain extent, reduce tip leakage, thereby improving the overall performance or stable operating margin of the rotor / stage. This implementation uses the rotor tip thinning method as an example.

[0026] The present invention is used to modify the rotor blade tip for reducing tip leakage flow and improving compressor / turbine blade tip flow, and constructs a rotor blade tip refinement modification method, which is specifically implemented according to the following steps: Step 1: The arc of the rotor tip modification is controlled by B-spline curve fitting. Three control points are arranged at equal distances on the pressure side and suction side of the rotor blade along the arc of the tip modification, and one control point is used to control the radial starting position of the tip modification. In this way, a rotor tip circumferential and radial parameterization method using seven design parameters is constructed. Specifically: Step 1.1: The arc of the rotor blade tip modification is controlled by B-spline curve fitting. Three control points are arranged at equal distances on the pressure side and suction side of the rotor blade along the arc of the blade tip modification. Figure 1 As shown in the figure, parameters Span_PS1 and Span_SS1 define the relative position of the first control point of the tip modification. The radial position is consistent with the prototype blade. Setting the initial value of parameters Span_PS1 and Span_SS1 to 1 means that the circumferential positions of the first and second control points are consistent. Parameters Span_PS2 and Span_SS2 are the relative positions along the arc from the first control point to the second control point. The initial value of this parameter is 1, which means that the circumferential positions of the second and third control points are consistent.

[0027] Similarly, the parameters Span_PS3 and Span_SS3 define the relative position of the second control point to the third control point along the arc. The initial values ​​of the parameters Span_PS3 and Span_SS3 are set to 1, corresponding to the rotor geometry without blade tip modification. In step 1.2, parameter Span_S7 defines the radial starting position of the tip modification, with a minimum value of 90% and a maximum value of 100% of the blade height. This constructs a circumferential and radial parameterization method for the rotor tip using seven design parameters.

[0028] Step 2: Construct a rotor blade tip axial parameterization method for the blade profile of the rotor blade tip section and control the thickness distribution of the blade profile through design parameters. Specifically: Step 2.1, parameterize the blade profile of the blade tip section and name the upper and lower profiles of the blade profile (representing the suction side and pressure side respectively) as y o,up and y o,low The Hicks-Henne and improved parameterization method is used to control the thickness distribution of the blade profile. This method superimposes a series of smooth basis functions on the original smooth function. Therefore, the improved function must be smooth when used to control the geometry.

[0029] The blade profile expression obtained by this method is shown in formula (1); 0≤x≤1(1), In formula (1), y up is the upper profile line of the modified blade; y low is the lower profile line of the modified blade; f k (x) is the kth basis function; x is the relative chord length of the blade; SS k is the basis function coefficient of the upper profile of the modified blade; PS k is the basis function coefficient of the lower profile of the modified blade; Step 2.2, the basis function is a series of smooth functions, and the basis function expression is shown in formula (2); (2), In formula (2), x k is the relative chord length corresponding to the peak value of the basis function; In step 2.3, theoretically, a greater number of basis functions will describe a more accurate blade profile. However, this will increase the number of corresponding design variables, making the calculations more complex and significantly increasing the difficulty of optimization. Typically, a range of 4 to 9 design variables per side is appropriate, meaning a total of 8 to 18 design variables for the upper and lower blade profiles.

[0030] Here, six basis functions are selected for parameterized control of blade profile, i.e., six basis functions are iterated based on the distribution of the original cross-section torsion angle. The Hicks-Henne basis function distribution is as follows: Figure 2 As shown. Assuming k=1, 2, 3, 4, 5, 6, x k are 0.1, 0.3, 0.5, 0.7, 0.85 and 0.94 respectively. When x=0 or 1, f k(x) = 0, which meets the requirement that the leading and trailing edge positions of the modified blade remain unchanged. The blade profile lines of the blade section at the radial height of the first control point (Span_PS1 and Span_SS1), the second control point (Span_PS2 and Span_SS2), and the third control point (Span_PS3 and Span_SS3) need to be parameterized identically.

[0031] There are 12 design parameters for axial modification, including SS1~SS6 and PS1~PS6. When a positive value is taken, it means adding Figure 3 The tip winglet shown in the figure has a negative value, which indicates tip thinning. The parameters are selected according to the design requirements and actual conditions. In order to prevent the axial thinning value from being too large, which may cause structural problems due to the thin tip of the blade, the design parameters of each axial thinning are limited to no more than 20% of the blade thickness at the corresponding position. The specific SS k and PS k The value range of can be seen in Table 1, where 0 means that the blade profile at this position is not thinned, thereby achieving single-side / double-side and uniform / non-uniform thinning in the directional position (circumferential, radial and axial). The value range of each design parameter for axial thinning is shown in Table 1. The axial thinning effect is shown in Figure 4 shown.

[0032] Table 1

[0033] Step 3: Modify the geometry of the rotor blade tip by changing the numerical values ​​of the design parameters. This can achieve circumferential, radial, and axial blade tip modification of the rotor blade geometry, including modification of one side of the rotor blade pressure side or suction side, modification of both sides of the rotor blade (pressure side and suction side), and partial modification only at the chord length position of the airfoil.

[0034] Tip thinning involves multiple design parameters, making it difficult to assess the impact of a single design parameter on rotor performance. Therefore, a DOE design of experiments approach was proposed to generate multiple different tip thinning methods to modify the rotor tip geometry. These included thinning of the rotor blade tip on either the pressure or suction side, thinning on both sides (pressure and suction), and thinning only on the chord length. The performance of the modified rotors was analyzed to assess the scope and extent of the impact of key parameters.

[0035] The advantages of the method of the present invention are mainly as follows: (1) Precise Control and Optimized Design: This invention uses a parameterized approach based on B-spline curve fitting and seven design parameters to achieve precise control of the rotor blade tip geometry in the circumferential, radial, and axial directions. By adjusting the design parameters, the rotor blade pressure and suction surfaces, as well as the airfoil chord length, can be flexibly modified on one or both sides, enhancing the design's precision and controllability, enabling better adaptation to varying operating conditions.

[0036] (2) Significantly improve compressor / turbine performance: By fine-tuning the blade tip, the present invention can effectively reduce rotor tip leakage flow and reduce flow blockage at the blade tip, thereby reducing flow losses and controlling flow separation. This improvement can not only significantly increase the stall margin of the compressor / turbine, but also improve the efficiency and pressure ratio of the compressor / turbine, significantly improving its overall performance.

[0037] Specific example 2: This embodiment takes the outlet stage of a ten-stage compressor as the research object. The outlet stage compressor is a subsonic axial flow compressor. Two different rotor tip clearances (0.2 mm and 0.6 mm) including the design tip clearance are selected, and the obtained tip geometry modifications of the tip thinning in different dimensions (circumferential, radial and axial) and sizes (width, length, height) are combined to carry out a study on the influence of tip thinning on rotor performance. Considering the design parameters of 3 parameters on the pressure side, 3 parameters on the suction side, 1 parameter of the starting position of the tip thinning and 12 parameters related to axial blade thinning, the Taguchi DOE method is used to study the influence characteristics of 19 design parameters under three different rotor tip clearances, and then the influence of the tip geometry modification of the tip thinning under different rotor tip clearances on the rotor performance such as efficiency, pressure ratio and stall margin is obtained, and finally the tip thinning scheme that can optimize the low clearance effect of the compressor stage is determined. The technical route is as follows Figure 5 shown.

[0038] The Taguchi DOE experimental design method prepares a new set of methods (OAs) by uniquely combining orthogonal Latin squares for various experimental situations. A mixed level design is used for the 19 blade tip thinning design parameters, where the 7 circumferential and radial design parameters are two-level factors and the 12 axial design parameters are three-level factors, generating the following: Figure 6 The DOE experimental design table for Taguchi mixed-level factors is shown.

[0039] The row numbers (A, B, C…S) represent the 19 design parameters, the column numbers (1, 2, 3…36) represent the 36 experimental designs, the numbers 1 and 2 corresponding to AG represent the minimum and maximum values ​​of the design variables, respectively, and the numbers 1, 2, and 3 corresponding to HS represent the minimum, median, and maximum values ​​of the design variables, respectively.

[0040] Generate as Figure 6 The Taguchi mixed-level factorial DOE experimental design table shown covers a variety of different types of blade tip thinning methods. In this orthogonal array, the chances of any factor level and combination appearing the same number of times are evenly distributed.

[0041] Through comparative analysis, three blade tip thinning schemes with more outstanding effects were selected from 36 DOE calculation results. The three schemes were named DOE_6, DOE_22 and DOE_24, and were evaluated and compared with the prototype scheme (ORI). Figure 7 A schematic diagram of the thinning scheme for the 100% blade height section is given. DOE_6 starts thinning evenly from 93.33% of the blade height; DOE_22 starts thinning from 96.67% of the blade height on the suction side and 98.33% of the blade height on the pressure side, with a smaller thinning on the pressure side; DOE_24 starts thinning from 96.67% of the blade height on the suction side and 98.33% of the blade height on the pressure side, with a smaller thinning on the pressure side. Figure 8 Table 2 shows the performance comparison of the three blade tip thinning schemes with the prototype. It can be seen that bilateral non-uniform thinning has a better improvement effect, improving near-design point efficiency and margin, which is consistent with the conclusions of the previous section. In particular, the near-design point efficiency at large clearances can be improved by more than 0.4%, and the overall margin can be improved by more than 1.2%. Table 2 shows the performance indicators of the prototype and DOE thinning schemes at different blade tip clearances: Table 2

[0042] DOE_6 and DOE_22 were selected for evaluation and comparison with the prototype solution. Figure 9 This is the static pressure distribution diagram at the blade height of 0.99. It can be seen that the envelope area of ​​the static pressure curve of the rotor blade tip is reduced after the blade tip is thinned, the rotor blade tip load is reduced, the work and pressure expansion capacity of the blade are also reduced, and therefore the intensity of the corresponding leakage flow is also reduced.

[0043] from Figure 10 It can be seen that the leakage rate is lower than that of the prototype from the leading edge to 56% of the chord length. In addition, when the gap increases to a large gap, the leakage rate is Figure 11 It was found that after the blade tip was thinned, the axial velocity of the airflow at the blade tip increased, and the axial momentum of the airflow flowing into the channel increased. This also shows that the blade tip thinning reduced the degree of blockage at the blade top inlet and improved the inlet flow conditions.

[0044] Above 0.1 times the blade height, the axial velocity of the airflow is high, which has a stronger effect on suppressing tip leakage flow and facilitates better airflow into the channel. After tip thinning, the axial velocity at the rotor outlet increases above 0.65 times the blade height, indicating that tip thinning improves the flow capacity within the blade tip channel.

[0045] analyze Figure 12 、 Figure 13 and Figure 14 It can be concluded that after tip thinning, the rotor outlet axial velocity increases above 0.7 times the blade height, indicating that tip thinning improves the flow capacity within the tip channel. Tip thinning reduces the degree of blockage at the tip inlet, significantly reducing the relative airflow angle at the tip inlet, making it easier for air to flow into the channel. From approximately the leading edge to 40% of the chord length, the leakage rate is lower than that of the prototype.

[0046] The present invention, namely the rotor blade tip fine shaping method, is based on the design concept of various types of rotor blade tip shaping. In view of the lack of a universally applicable rotor blade tip parameterized shaping method, the tip shaping is used to control the flow separation caused by secondary flows such as blade tip leakage vortex and reduce flow losses, so as to better weaken the rotor blade tip leakage flow, reduce the flow blockage at the blade top, improve the flow conditions inside the compressor / turbine, and thus achieve the purpose of greatly improving the compressor / turbine stall margin and improving the compressor / turbine efficiency and compression ratio, meet the urgent demand for stable operation of the compressor / turbine, and have important significance for indicators such as the fuel consumption rate and thrust-to-weight ratio of the whole machine.

[0047] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for fine-tuning the blade tip of a turbomachinery rotor, characterized in that: The following steps are involved: Step 1: Using a B-spline curve as a fitting control line for the rotor blade tip modification arc, multiple control points are arranged at equal distances on the pressure side and suction side of the rotor blade along the fitting control line. At the same time, a radial starting position control point for controlling the blade tip modification is given, and the design parameters corresponding to the control point are recorded as the blade tip geometric circumferential and radial parameters of the rotor blade, thereby obtaining the rotor blade tip geometric circumferential and radial modification arcs controlled by the curve fitting; By changing the design parameters corresponding to the control points of the circumferential and radial modification arcs of the rotor blade tip geometry, the circumferential and radial modification of the rotor blade tip geometry can be achieved; Step 2: Based on the upper and lower profiles of the rotor blade tip cross-section, the basis functions of the upper and lower profiles of the rotor blade tip axial direction controlled by curve fitting are constructed based on the Hicks-Henne method. The basis functions and basis function coefficients of the upper and lower profiles are converted into design parameters of the rotor blade tip axial direction, and the thickness distribution of the profile lines is controlled by the design parameters. By changing the basis functions and basis function coefficients of the upper and lower profiles, the blade tip is modified in the axial direction of the rotor blade tip geometry, and thinned blade tip geometry is obtained under different rotor blade tip clearances. Step 3. Perform DOE experimental design based on the basis function coefficients corresponding to the thinned blade tip geometry and the control points of the circumferential and radial modification arcs of the rotor blade tip geometry to obtain the influence of the modified blade tip geometry on the blade efficiency, pressure ratio and stall margin rotor performance, and finally determine the blade tip thinning or winglet addition scheme to optimize the gap effect, flow separation and loss problems caused by the compressor clearance.

2. The method for fine-tuning the blade tip of a turbomachinery rotor according to claim 1, characterized in that: In the step 1, three control points are arranged at equal distances on the pressure side and the suction side of the rotor blade.

3. The method for fine-tuning the blade tip of a turbomachinery rotor according to claim 2, characterized in that: The step 1 is specifically as follows: Step 1.1: Define the first control point of the rotor blade tip pressure surface as Span_PS1 and the first control point of the rotor blade tip suction surface as Span_SS1. Span_PS1 and Span_SS1 are the relative positions of the first control points of the rotor blade tip modification. The radial positions of the two are consistent with the prototype blade. When the initial values ​​of Span_PS1 and Span_SS1 are set to 1, it means that the circumferential positions of the first and second control points are consistent. At the same time, define the second control point of the rotor blade tip pressure surface as Span_PS2 and the second control point of the rotor blade tip suction surface as Span_SS2. Span_PS2 and Span_SS2 are the relative positions of the first control point to the second control point along the arc. When the initial values ​​of Span_PS2 and Span_SS2 are 0, it means that the circumferential positions of the second control point and the first control point are consistent. When the initial values ​​of Span_PS2 and Span_SS2 are 1, it means that the circumferential positions of the second control point and the third control point are consistent. Similarly, define the third control point of the rotor blade tip pressure surface as Span_PS3 and the third control point of the suction surface as Span_SS3. Span_PS3 and Span_PS3 are the relative positions of the second control point along the arc to the third control point. When the initial values ​​of Span_PS3 and Span_PS3 are 0, it means that the circumferential positions of the third control point and the second control point are consistent. When the initial values ​​of Span_PS3 and Span_SS3 are set to 1, it means that there is no modification of the rotor blade tip geometry. Step 1.2, define the radial starting position control point for controlling the rotor tip modification as Span_S7, and in the radial direction of the rotor tip modification, the positions of the Span_PS1 and Span_SS1 control points are consistent, the positions of the Span_PS2 and Span_SS2 control points are consistent, and the positions of the Span_PS3 and Span_SS3 control points are consistent; Thus, the geometric circumferential and radial modification arcs of the rotor blade tip controlled by seven design parameters were constructed.

4. The method for fine-tuning the blade tip of a turbomachinery rotor according to claim 3, characterized in that: The maximum cutting values ​​Max Span_PS1-3 and Max Span SS1-3 of the corresponding positions of the three control points Span_PS1-3 of the rotor blade tip pressure surface and the three control points Span_SS1-3 of the rotor blade tip suction surface are 1, and the minimum cutting values ​​Min Span_PS1-3 and MinSpan SS1-3 are 0; Meanwhile, the minimum value of Span_S7 is 90% of the blade height, and the maximum value is 100% of the blade height.

5. The method for fine-tuning the blade tip of a turbomachinery rotor according to claim 1, wherein: The step 2 is specifically as follows: Let the upper and lower profiles of the blade tip section be y o,up and y o,low , which represent the suction side and pressure side of the rotor blade respectively; Then, based on the Hicks-Henne method, a smooth basis function is superimposed on the smooth function to ensure the geometric smoothness of the controlled blade profile. Then, the leaf shape expression is obtained as: 0≤x≤1， Where y up is the upper mold line; y low is the lower mold line; f k (x) is the kth basis function; x is the relative chord length of the blade; SS k is the basis function coefficient of the upper profile; PS k is the basis function coefficient of the lower profile; Among them, the basis function f k (x) is expressed as: ， Where x k is the relative chord length corresponding to the peak value of the basis function; By changing the basis function coefficient SS of the upper mold line in the formula k , basis function coefficient PS of lower profile k , the relative chord length x corresponding to the basis function peak k The value of is the axial design parameter of the rotor blade tip, thereby realizing the control of the upper and lower profiles of the blade.

6. The method for fine-tuning the blade tip of a turbomachinery rotor according to claim 5, characterized in that: Select basis functions and basis function coefficients SS according to target requirements k and the basis function coefficients PS of the lower profile k The number of basis functions selected is 4-9, corresponding to the basis function coefficients SS1~SS9, PS1~PS 9， A total of 8 to 18 items were selected.

7. The method for fine-tuning the blade tip of a turbomachinery rotor according to claim 5, characterized in that: Based on the distribution of the cross-sectional twist angle of the rotor blade tip, six basis functions are iterated to parameterize and control the axial blade profile of the rotor blade tip; Assuming k = 1, 2, 3, 4, 5, 6, the relative chord length x corresponding to the basis function peak is k are 0.1, 0.3, 0.5, 0.7, 0.85 and 0.94 respectively. When x=0 or 1, f k (x) = 0, which meets the requirement that the leading and trailing edge positions of the blade remain unchanged after axial modification; At this time, the basis function coefficients of the upper profile are SS1~SS6 and the basis function coefficients of the lower profile are PS1~PS6, with a total of 12 design parameters. When a positive value is taken, a tip winglet is added, and when a negative value is taken, the tip of the blade is thinned. The parameters are selected according to the design requirements and actual conditions.

8. The method for fine-tuning the blade tip of a turbomachinery rotor according to claim 5, characterized in that: The axial design parameters of the rotor blade tip do not exceed 20% of the blade thickness at the corresponding position, which is used to prevent excessive changes in axial thinning from causing structural problems due to the thin tip of the blade, thereby achieving single-sided, double-sided, uniform and non-uniform thinning of the blade in the circumferential, radial and axial directions.

9. The method for fine-tuning the blade tip of a turbomachinery rotor according to any one of claims 1 to 8, characterized in that: The DOE experimental design is based on the design parameters corresponding to the control points of the geometric circumferential and radial modification arcs of the rotor blade tip as two-level factors, and the basis functions and basis function coefficients of the upper and lower profiles converted into the design parameters of the rotor blade tip axial direction as three-level factors, to generate a mixed level factor DOE experimental design table.

10. The method for fine-tuning the blade tip of a turbomachinery rotor according to claim 9, characterized in that: The design gap of the DOE experimental design is 0.2 mm to 0.6 mm.

Images