Tip shaping method for improving blade aeroelastic stability

Abstract

The present invention discloses a tip modification method for improving the aeroelastic stability of blades. A modification scheme is designed for rotor blades with aeroelastic stability problems. The blade height modification coefficient, the tip chord length modification coefficient, and the tip leading edge deflection angle are determined through the modification scheme design to obtain the theoretically designed modified blade. The aerodynamic performance, vibration strength, and aeroelastic stability of the theoretically designed blade are calculated and evaluated respectively to obtain a theoretically designed blade whose calculation and evaluation results meet the requirements. The physical rotor blades with aeroelastic stability problems are machined and ground according to the theoretically designed blade to obtain the modified physical blades. The modified physical blades are tested on fan / compressor components to obtain physical blades that meet the aeroelastic stability requirements, thereby avoiding aeroelastic stability problems of the blades. Compared with the prior art, this solution reduces the time cost and economic cost, has strong practicability, and is suitable for wide promotion and application.

Description

Technical Field

[0001] The present invention relates to the technical field of blade processing, and in particular, to a tip shaping method for improving the aeroelastic stability of blades. Background Art

[0002] Modern aeroengines are developing towards the direction of high thrust-to-weight ratio / high power-to-weight ratio, which requires the fan / compressor to have higher performance, more compact structure and lower weight. Correspondingly, the load level of the fan / compressor is getting higher and higher, the axial distance between the rotor and the stator is getting smaller and smaller, the rotor blades adopt complex compound sweep designs, and the integral bladed disk is adopted in the structure, resulting in smaller damping of the rotor. However, these factors will all increase the aeroelastic stability risk of the fan / compressor blades.

[0003] The aeroelastic stability risks of fan / compressor blades include main problems such as flutter and asynchronous vibration. Flutter is a self-excited vibration, where the blade vibrates first and continuously obtains energy from the flow field during the vibration process, causing the vibration amplitude to become larger and larger; while asynchronous vibration is a forced vibration, which is caused by the unstable flow in the flow field exciting a certain natural frequency of the blade. The occurrence of any aeroelastic stability problem may cause the rotor and stator of the aeroengine to be damaged or even penetrated, resulting in the aircraft being unable to complete the intended mission, and even serious consequences such as damage and casualties.

[0004] For the flutter prediction and evaluation technology, currently in the preliminary design stage of the fan / compressor, the empirical method is usually used for flutter evaluation; in the detailed design stage of the fan / compressor, the unsteady numerical simulation method is usually used for flutter prediction, including the fluid-structure decoupling method and the fluid-structure coupling method. For the prediction and evaluation of asynchronous vibration, it is impossible to know which rotational speed has the risk of asynchronous vibration during the design stage. Moreover, even if the aeroelastic risk operating point of the compressor is known, the prediction simulation must adopt the fluid-structure coupling calculation simulation evaluation method of the full-ring model. Although the fluid-structure coupling calculation can largely consider the physical essence of the interaction between the three-dimensional flow field and the vibrating blade, and its calculation results are close to the real situation, its calculation amount is large, the calculation time is long and it is difficult to converge, making it difficult to carry out engineering applications. Therefore, during the preliminary design of fan / compressor blades, it is impossible to completely eliminate and avoid the aeroelastic stability risk through numerical simulation methods, and it must be verified through experiments after the blades are processed and formed.

[0005] At present, for the processed fan / compressor rotor blades, if abnormal aeroelastic stability is monitored during component tests or engine full-scale tests, the existing airfoil is generally analyzed, and then the design parameters such as the airflow angle distribution, thickness distribution, and sweep distribution of the rotor blade are readjusted to conduct the shaping design of the new blade airfoil, and the calculation and evaluation of aerodynamic performance, vibration strength, and aeroelastic stability are completed. Then, a new blank is used for full-cycle processing to manufacture a new blade to avoid aeroelastic stability risks. However, this method will lead to the redesign and reprocessing of the entire blade, greatly increasing the manufacturing cycle of the blade, with high time costs, and the original rotor blade cannot be used normally and can only be wasted. The economic cost of obtaining a qualified blade through two or even multiple processing is high. Summary of the Invention

[0006] The present invention provides a tip modification method for improving the aeroelastic stability of blades to solve the technical problems of high time cost and high economic cost in the existing methods for improving the aeroelastic stability of rotor blades.

[0007] The technical solution provided by the present invention is: a tip modification method for improving the aeroelastic stability of blades, including the following steps: S1: Starting from improving aeroelastic stability, a modification scheme is designed for the rotor blade with aeroelastic stability problems. Through the modification scheme design, the blade tip height modification coefficient, the blade tip chord length modification coefficient, and the blade tip leading edge deflection angle are determined to obtain the theoretically designed modified blade. Among them, the blade tip height modification coefficient is the ratio of the meridional projection height between the leading edge point of the blade tip of the rotor blade and the starting position of the forward sweep of the leading edge of the rotor blade to the meridional projection height between the leading edge point of the blade tip of the rotor blade and the leading edge point of the root section of the rotor blade. The blade tip chord length modification coefficient is the ratio of the length from the leading edge point of the blade tip to the modified leading edge point of the blade tip to the chord length of the blade tip section. The blade tip leading edge deflection angle is the angle at which the modified leading edge point of the blade tip deflects towards the pressure surface profile; S2: The aerodynamic performance, vibration strength, and aeroelastic stability of the theoretically designed blade are calculated and evaluated respectively. Among them, if the calculation and evaluation results do not meet the requirements, steps S1-S2 are repeated until the calculation and evaluation results meet the requirements; S3: The physical rotor blade with aeroelastic stability problems is processed and ground according to the theoretically designed blade to obtain the modified physical blade; S4: The modified physical blade is subjected to fan / compressor component tests. Among them, if the test results show that the modified physical blade does not meet the aeroelastic stability requirements, steps S1-S4 are repeated until the test results show that the modified physical blade meets the aeroelastic stability requirements.

[0008] As a further improvement of the above technical solution:

[0009] Further, in step S1, the confirmation process of the blade height modification coefficient is as follows: Find the starting position b of the forward sweep of the rotor blade leading edge through the blade leading edge line. Set the streamline section where the starting position b is located as the first section, and set the tip section where the tip leading edge point a of the rotor blade is located as the fourth section. Evenly select two intermediate section positions in the first section and the fourth section as the second section and the third section. Set the leading edge point of the root section of the rotor blade as c. That is, the blade height modification coefficient is obtained based on the following calculation formula:

[0010]

[0011] Among them, is the blade height modification coefficient, H1 is the meridional projection height from point a to point b, and H is the meridional projection height from point a to point c.

[0012] Further, in step S1, the confirmation process of the tip chord length modification coefficient is as follows: Set the modified tip leading edge point as d. That is, the tip chord length modification coefficient is obtained based on the following calculation formula:

[0013]

[0014] Among them, is the tip chord length modification coefficient, L1 is the length from the tip leading edge point a to the modified tip leading edge point d, and L is the chord length of the tip section of the blade.

[0015] Further, in step S1, the confirmation process of the tip leading edge deflection angle is as follows: The blade includes a leading edge profile, a blade body, and a trailing edge profile. The profile of the blade body is confirmed based on the mean camber line and includes a pressure side profile and a suction side profile. Set the starting point of the modification of the suction side profile as f, and set the starting point of the modification of the pressure side profile as g. Then the intersection point of the mean camber line and gf is o, and the intersection point of the mean camber line and the modified blade leading edge profile is e. That is, the tip leading edge deflection angle θ = ∠doe and it is biased towards the pressure side profile.

[0016] Further, in step S1, the specific steps to obtain the modified theoretical design blade are as follows: First, determine the positions of each section of the rotor blade before modification according to the blade height modification coefficient Then modify the fourth section according to the tip chord length modification coefficient At the same time, modify the leading edge of the blade of the second section and the third section proportionally, keep the first section unchanged. Finally, during the modification process, the leading edge of each section adopts an elliptical arc form with a local head towards the pressure side according to the tip leading edge deflection angle θ, so as to obtain the modified theoretical design blade.

[0017] Furthermore, in step S2, the process of calculating and evaluating the aerodynamic performance of the theoretically designed blade is as follows: First, the modified theoretically designed blade is used to generate structured grids through grid drawing software to obtain the structured grids of the fluid domain; then the structured grids are set for pre-calculation through CFD pre-processing software and three-dimensional simulation calculations are performed; finally, according to the calculation results, the flow rate, pressure ratio, efficiency, and margin of the fan / compressor are extracted and compared with the corresponding design indicators to determine whether it can meet the aerodynamic performance requirements.

[0018] Furthermore, in step S2, the process of calculating and evaluating the vibration strength of the theoretically designed blade is as follows: First, the modified theoretically designed blade is modeled through UG software to obtain the UG model of the rotor blade disk, and then unstructured grids are generated through grid drawing software to obtain the unstructured grids of the solid domain; then the unstructured grids are set for pre-processing of strength and vibration calculations through workbench pre-processing software and three-dimensional simulation calculations are performed; finally, according to the calculation results, the deformation, stress, frequency, vibration mode, and frequency dispersion of the theoretically designed blade are extracted and compared with the requirements of the corresponding strength and vibration design specifications to determine whether it can meet the strength and vibration requirements.

[0019] Furthermore, in step S2, the process of calculating and evaluating the aeroelastic stability of the theoretically designed blade is as follows: Calculate the natural frequency and vibration mode of the theoretically designed blade, interpolate them onto the grids of the flow field calculation, make the theoretically designed blade move according to specific frequencies, phase angles, vibration modes, and amplitudes, and judge whether flutter occurs by calculating the positive and negative work done by the fluid on the blade within one vibration cycle.

[0020] Furthermore, in step S3, the specific process of machining and grinding is as follows: First, the blade profile of the tip region of the physical rotor blade with aeroelastic stability problems is measured to provide a reference basis for subsequent machining and grinding; then, referring to the theoretically designed blade, a numerical control milling lathe is used to machine and grind the leading edge of the tip of the rotor blade; finally, the blade profile of the tip region of the rotor blade after grinding is measured again to determine whether the physical grinding meets the blade profile requirements of the modified theoretically designed blade.

[0021] Furthermore, in step S4, the specific test process of the fan / compressor component test is as follows: First, replace and assemble the physical modified blade, complete the assembly of the rectified fan / compressor component test piece, and at the same time complete the preparation work of the test bench and the test system; then, when opening the outlet throttle valve of the fan / compressor, push the speed of the component test piece to the set speed, and then continuously close the outlet throttle valve until a surge signal is detected at the outlet, then open the throttle valve to complete the performance recording at this speed; finally, push the speed of the component test piece to different speeds to complete the performance recording at different speeds, and during the test process, pay attention to the real-time changes of the tip amplitude, dynamic stress and dynamic pressure. Once the monitored parameters are abnormal, pull down the speed to stop the test, indicating that there is an aeroelastic stability problem with the physical modified blade. If the monitored parameters of the tip amplitude, dynamic stress and dynamic pressure do not show abnormalities during the whole test process, it indicates that there is no aeroelastic stability problem with the physical modified blade.

[0022] The present invention has the following beneficial effects:

[0023] The tip modification method for improving the aeroelastic stability of the blade of the present invention designs a modification scheme for the rotor blade with aeroelastic stability problems starting from improving aeroelastic stability. By designing the modification scheme, the blade height modification coefficient, the tip chord length modification coefficient and the tip leading edge deflection angle are determined to obtain the theoretically designed modified blade. During the modification process, the tip chord length of the blade can be reduced and the ratio of the root chord length to the tip chord length can be increased by the blade height modification coefficient and the tip chord length modification coefficient, and at the same time the sweep is also reduced, so as to improve the rigidity of the theoretically designed blade and improve the aeroelastic stability risk. The leading edge of the theoretically designed blade can adopt a locally deflected elliptical arc form through the tip leading edge deflection angle to minimize the influence of the tip positive angle of attack as much as possible and improve the tip flow field, so as to achieve the purpose of improving the aeroelastic stability risk at the tip to a certain extent; by calculating and evaluating the aerodynamic performance, vibration strength and aeroelastic stability of the theoretically designed blade respectively, the theoretically designed blade with the calculation and evaluation results meeting the requirements can be obtained; machining and grinding the physical rotor blade with aeroelastic stability problems according to the theoretically designed blade to obtain the physical modified blade; through the fan / compressor component test on the physical modified blade, the physical blade meeting the aeroelastic stability requirements can be obtained, thus avoiding the aeroelastic stability problem of the blade; this solution improves the aeroelastic stability of the blade by modifying the tip area of the rotor blade with aeroelastic stability problems. Compared with the prior art, this solution is simple and easy to implement, and the machining and modification are simple, greatly shortening the blade design and processing cycle, reducing the time cost. At the same time, the original physical blade can be used normally after modification, saving the materials, manpower and costs for reprocessing new blades, reducing the economic cost, and having strong practicability, being suitable for wide promotion and application.

[0024] In addition to the purposes, features, and advantages described above, the present invention has other purposes, features, and advantages. The present invention will be further described in detail below with reference to the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The drawings forming a part of this application are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings:

[0026] Figure 1 is a flowchart of a tip modification method for improving the aeroelastic stability of blades in a preferred embodiment of the present invention;

[0027] Figure 2 is a schematic diagram of the position of the tip modification section of the rotor blade in the tip modification method for improving the aeroelastic stability of blades in a preferred embodiment of the present invention;

[0028] Figure 3 is a schematic diagram of the leading edge region of the theoretically designed blade in the tip modification method for improving the aeroelastic stability of blades in a preferred embodiment of the present invention;

[0029] Figure 4 is a schematic diagram of the blade profile of a fan / compressor in the prior art;

[0030] Figure 5 is Figure 3 an enlarged schematic diagram of region M in

[0031] Figure 6 is a comparison diagram of the external flow characteristics of a fan component during a test at a certain rotational speed before and after tip modification of a certain type of fan rotor blade. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0032] The embodiments of the present invention will be described in detail below with reference to the drawings. However, the present invention can be implemented in many different ways defined and covered by the following.

[0033] As Figure 1As shown in the figure, the tip modification method for improving the aeroelastic stability of the blade in this embodiment includes the following steps: S1: Starting from improving the aeroelastic stability, a modification scheme is designed for the rotor blade with aeroelastic stability problems. Through the modification scheme design, the blade height modification coefficient, the tip chord length modification coefficient, and the tip leading edge deflection angle are determined to obtain the theoretically designed modified blade. Among them, the blade height modification coefficient is the ratio of the meridional projection height between the tip leading edge point of the rotor blade and the starting position of the leading edge sweep of the rotor blade to the meridional projection height between the tip leading edge point of the rotor blade and the leading edge point of the root section of the rotor blade. The tip chord length modification coefficient is the ratio of the length from the tip leading edge point to the modified tip leading edge point to the chord length of the blade tip section. The tip leading edge deflection angle is the angle at which the modified tip leading edge point deviates from the pressure surface profile; S2: Calculate and evaluate the aerodynamic performance, vibration strength, and aeroelastic stability of the theoretically designed blade respectively. Among them, if the calculation and evaluation results do not meet the requirements, repeat steps S1 - S2 until the calculation and evaluation results meet the requirements; S3: Process and grind the physical rotor blade with aeroelastic stability problems according to the theoretically designed blade to obtain the modified physical blade; S4: Conduct fan / compressor component tests on the modified physical blade. Among them, if the test results show that the modified physical blade does not meet the aeroelastic stability requirements, repeat steps S1 - S4 until the test results show that the modified physical blade meets the aeroelastic stability requirements.

[0034] As Figure 1As shown, specifically, for the tip modification method of improving the aeroelastic stability of blades in the present invention, starting from improving aeroelastic stability, a modification scheme is designed for rotor blades with aeroelastic stability problems. By designing the modification scheme, the blade height modification coefficient, the tip chord length modification coefficient, and the tip leading edge deflection angle are determined to obtain the theoretically designed modified blade. During the modification process, by the blade height modification coefficient and the tip chord length modification coefficient, the tip chord length of the blade can be reduced, the root chord length ratio can be increased, and at the same time, the sweep is also reduced, so as to improve the rigidity of the theoretically designed blade and improve the aeroelastic stability risk. By the tip leading edge deflection angle, the leading edge of the theoretically designed blade adopts a locally deflected elliptical arc form to minimize the influence of the tip positive angle of attack as much as possible and improve the tip flow field, so as to achieve the purpose of improving the aeroelastic stability risk at the tip to a certain extent; through the calculation and evaluation of the aerodynamic performance, vibration strength, and aeroelastic stability of the theoretically designed blade respectively, the theoretically designed blade with the calculation and evaluation results meeting the requirements is obtained; according to the theoretically designed blade, the physical rotor blade with aeroelastic stability problems is processed and ground to obtain the modified physical blade; through the fan / compressor component test on the modified physical blade, the physical blade meeting the aeroelastic stability requirements is obtained, so as to avoid the occurrence of aeroelastic stability problems of the blade; this scheme improves the aeroelastic stability of the blade by modifying the tip region of the rotor blade with aeroelastic stability problems. Compared with the prior art, this scheme is simple and easy to implement, and the processing modification is simple, greatly shortening the blade design and processing cycle, reducing the time cost. At the same time, the original physical blade can be used normally after modification, saving the materials, manpower, and expenses for reprocessing new blades, reducing the economic cost, and having strong practicability, being suitable for wide promotion and application.

[0035] It should be understood that, compared with the prior art, in this scheme, through steps S1 - S4, the airfoil is gradually corrected during the adaptation test, reducing the time and economic costs, and at the same time meeting the requirement of avoiding the aeroelastic stability risk.

[0036] It should be understood that this scheme only needs to improve the local airfoil at the tip. By confirming the blade height modification coefficient, the tip chord length modification coefficient, and the tip leading edge deflection angle, the tip chord length, the root chord length ratio, and the sweep can be changed, and a locally deflected elliptical leading edge is adopted, so as to achieve the effect of improving the aeroelastic stability of the blade and solve the problem of abnormal aeroelastic stability.

[0037] It should be understood that the processing procedure adopted in this scheme is simple, the processing cycle is short, and the fan / compressor blade disk with aeroelastic stability problems can return to normal use after modification, which can greatly reduce the time cost and economic cost.

[0038] Such as Figure 2As shown in the figure, in this embodiment, in step S1, the confirmation process of the blade height modification coefficient is as follows: Find the starting position b of the forward sweep of the rotor blade leading edge through the blade leading edge line. Set the streamline section where the starting position b is located as the first section, set the tip section where the tip leading edge point a of the rotor blade is located as the fourth section, and evenly select two intermediate section positions in the first section and the fourth section as the second section and the third section. Set the leading edge point of the root section of the rotor blade as c. That is, the blade height modification coefficient is obtained based on the following calculation formula:

[0039]

[0040] Wherein, is the blade height modification coefficient, H1 is the meridional projection height from point a to point b, and H is the meridional projection height from point a to point c.

[0041] Preferably, The selection range of is 15% - 35%, which is specifically determined by the starting position of the forward sweep of the tip of the blade rotor. Through this parameter, the rigidity of the leading edge of the blade tip can be improved, and thus the aeroelastic stability of the rotor blade can be improved.

[0042] As Figure 3 shown in the figure, in this embodiment, in step S1, the confirmation process of the tip chord length modification coefficient is as follows: Set the modified tip leading edge point as d. That is, the tip chord length modification coefficient is obtained based on the following calculation formula:

[0043]

[0044] Wherein, is the tip chord length modification coefficient, L1 is the length from the tip leading edge point a to the modified tip leading edge point d, and L is the chord length of the blade tip section.

[0045] Preferably, The selection range of is 4% - 10%, which is specifically determined by calculation evaluation and experimental verification. Through this parameter, the rigidity of the leading edge of the blade tip can also be improved, and thus the aeroelastic stability of the rotor blade can be improved.

[0046] As Figure 4 and Figure 5 shown in the figure, in this embodiment, in step S1, the confirmation process of the tip leading edge deflection angle is as follows: The blade includes a leading edge profile, a blade body, and a trailing edge profile. The profile of the blade body is confirmed based on the mean camber line and includes a pressure surface profile and a suction surface profile. Set the starting point of the modification of the suction surface profile as f, and set the starting point of the modification of the pressure surface profile as g. Then the intersection point of the mean camber line and gf is o, and the intersection point of the mean camber line and the modified leading edge profile of the blade is e. That is, the tip leading edge deflection angle θ = ∠doe and is biased towards the pressure surface profile.

[0047] Preferably, on the premise of ensuring the smoothness of the blade leading edge profile, the larger the leading edge deflection angle θ of the blade tip is, the better. By this parameter, the flow condition of the air flow in the blade passage at the blade tip can be improved, and thus the aeroelastic stability of the rotor blade can be improved.

[0048] It should be understood that Figure 5 The solid line in the figure is the theoretically designed blade after modification. Figure 5 The dashed line in the figure is the area to be modified of the rotor blade with aeroelastic stability problems.

[0049] It should be understood that as Figure 5 shown, the profile of the blade body is determined by the mean camber line. The mean camber line is a specific curve designed based on the velocity and direction of the air flow. Taking the points on the mean camber line as the centers, a series of circles (the centers are on the mean camber line of the blade profile) are generated along the mean camber line. The curves tangent to this series of circles on both sides of the mean camber line are the blade bodies.

[0050] In this embodiment, in step S1, the specific steps to obtain the theoretically designed blade after modification are as follows: Determine the positions of each cross-section of the rotor blade before modification according to the blade height modification coefficient Then modify the fourth cross-section according to the blade tip chord length modification coefficient At the same time, modify the leading edge of the blade of the second and third cross-sections proportionally, keep the first cross-section unchanged. Finally, during the modification process, the leading edge of each cross-section adopts an elliptical arc form with a local deviation towards the pressure surface according to the leading edge deflection angle θ of the blade tip, so as to obtain the theoretically designed blade after modification.

[0051] In this embodiment, in step S2, the process of calculating and evaluating the aerodynamic performance of the theoretically designed blade is as follows: First, generate a structured grid for the fluid domain by using grid drawing software for the theoretically designed blade after modification; then perform pre-processing settings for calculation through cfd pre-processing software on the structured grid and conduct three-dimensional simulation calculations; finally, according to the calculation results, extract the flow rate, pressure ratio, efficiency, and margin of the fan / compressor, and compare them with the corresponding design indicators to determine whether it can meet the aerodynamic performance requirements.

[0052] It should be understood that the flow rate, pressure ratio, efficiency, and margin of the fan / compressor are all design parameters.

[0053] It should be understood that the pre-processing settings for calculation of the cfd pre-processing software include design rotational speed, rotor-stator interface method, turbulence model, boundary conditions, etc.

[0054] In this embodiment, in step S2, the calculation and evaluation process of the vibration intensity of the theoretically designed blade is as follows: First, the above-mentioned modified theoretically designed blade is modeled by UG software to obtain the UG model of the rotor blade disk, and then unstructured meshing is generated by meshing software to obtain the unstructured mesh of the solid domain; then the unstructured mesh is subjected to preprocessing settings for strength and vibration calculations through workbench preprocessing software, and three-dimensional simulation calculations are performed; finally, according to the calculation results, the deformation, stress, frequency, vibration mode and frequency dispersion of the theoretically designed blade are extracted, and compared with the corresponding strength and vibration design specification requirements to determine whether it can meet the strength and vibration requirements.

[0055] It should be understood that the deformation, stress, frequency, vibration mode and frequency dispersion of the theoretically designed blade are all verification parameters.

[0056] It should be understood that the preprocessing settings of the workbench preprocessing software include rotational speed, temperature load, pressure load, boundary constraints, etc.

[0057] It should be understood that the meshing software, cfd preprocessing software, UG software and workbench preprocessing software are all well-known technologies to those skilled in the art, and will not be elaborated here.

[0058] In this embodiment, in step S2, the calculation and evaluation process of the aeroelastic stability of the theoretically designed blade is as follows: Calculate the natural frequency and vibration mode of the theoretically designed blade, interpolate them onto the grid of the flow field calculation, make the theoretically designed blade move according to a specific frequency, phase angle, vibration mode and amplitude, and judge whether flutter occurs by calculating the positive and negative work done by the fluid on the blade within one vibration cycle.

[0059] It should be understood that the aeroelastic stability calculation and evaluation is mainly to perform flutter evaluation based on the energy method. The energy method belongs to the fluid-structure decoupling method (also called the one-way coupling method), and estimates flutter from the perspective of energy exchange between the blade and the flow field.

[0060] In this embodiment, in step S3, the specific process of machining and grinding is as follows: First, perform leaf profile measurement on the tip region of the physical rotor blade with aeroelastic stability problems to provide a reference basis for subsequent machining and grinding; then, referring to the theoretically designed blade, use a numerical milling lathe to machine and grind the leading edge of the tip of the rotor blade; finally, perform leaf profile measurement on the tip region of the rotor blade after grinding again to determine whether the physical grinding meets the leaf profile requirements of the modified theoretically designed blade.

[0061] In this embodiment, in step S4, the specific test process of the fan / compressor component test is as follows: First, replace and assemble the physical modified blades to complete the assembly of the rectified fan / compressor component test piece, and at the same time complete the preparation work of the test bench and the test system; then, when opening the outlet throttle valve of the fan / compressor, push the speed of the component test piece to the set speed, and then continuously close the outlet throttle valve until a surge signal is detected at the outlet, and then open the throttle valve to complete the performance recording at this speed; finally, push the speed of the component test piece to different speeds to complete the performance recording at different speeds, and during the test process, pay attention to the real-time changes of the tip amplitude, dynamic stress and dynamic pressure. Once the monitored parameters are abnormal, pull down the speed to stop the test, indicating that there is an aeroelastic stability problem with the physical modified blades. If the monitored parameters of the tip amplitude, dynamic stress and dynamic pressure do not show abnormalities during the whole test process (i.e., during the process of recording the performance of the fan / compressor component at all speeds), it indicates that there is no aeroelastic stability problem with the physical modified blades.

[0062] It should be understood that for the test to verify the aeroelastic stability problem, it is necessary to conduct tests on the tip amplitude, dynamic stress and dynamic pressure during the test.

[0063] As Figure 6 shown, the fan / compressor blade tip modification method adopted by the present invention has been verified through fan component tests. From the comparison of the external characteristics lines of a certain type of fan rotor blade tip before and after modification at a certain speed in the fan component test, it can be seen that before the blade tip modification, the fan had an aeroelastic stability problem of non-synchronous vibration near the surge point in the external flow at a certain speed (see point A in Figure 6 , which is the near-surge point), while after the blade tip modification, the component test successfully completed the forced surge test at this speed (see point B in Figure 6 , which is the surge point), and no aeroelastic stability problems such as non-synchronous vibration occurred. The test results show that this method is feasible and effective.

[0064] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A tip modification method for improving the aeroelastic stability of blades, characterized in that It includes the following steps: S1: Starting from improving the aeroelastic stability, a modification scheme is designed for the rotor blade with aeroelastic stability problems. Through the modification scheme design, the blade height modification coefficient, the tip chord length modification coefficient, and the tip leading edge deflection angle are determined to obtain the theoretically designed modified blade. Among them, the blade height modification coefficient is the ratio of the meridional projection height between the tip leading edge point of the rotor blade and the starting position of the forward sweep of the rotor blade leading edge to the meridional projection height between the tip leading edge point of the rotor blade and the leading edge point of the root section of the rotor blade. The tip chord length modification coefficient is the ratio of the length from the tip leading edge point to the modified tip leading edge point to the chord length of the blade tip section. The tip leading edge deflection angle is the angle at which the modified tip leading edge point deflects towards the pressure surface profile; S2: Calculate and evaluate the aerodynamic performance, vibration strength, and aeroelastic stability of the theoretically designed blade respectively. Among them, if the calculation and evaluation results do not meet the requirements, repeat steps S1 - S2 until the calculation and evaluation results meet the requirements; S3: Machine and grind the physical rotor blade with aeroelastic stability problems according to the theoretically designed blade to obtain the modified physical blade; S4: Conduct fan / compressor component tests on the modified physical blade. Among them, if the test results show that the modified physical blade does not meet the aeroelastic stability requirements, repeat steps S1 - S4 until the test results show that the modified physical blade meets the aeroelastic stability requirements.

2. The tip modification method for improving the aeroelastic stability of blades according to claim 1, characterized in that In step S1, the confirmation process of the blade height modification coefficient is as follows: Find the starting position b of the forward sweep of the rotor blade leading edge through the blade leading edge line. Set the streamline section where the starting position b is located as the first section, set the tip section where the tip leading edge point a of the rotor blade is located as the fourth section, and evenly select two intermediate section positions as the second section and the third section in the first section and the fourth section. Set the leading edge point of the root section of the rotor blade as c. That is, the blade height modification coefficient is obtained based on the following calculation formula: ； Among them, is the blade height modification coefficient, H1 is the meridional projection height from point a to point b, and H is the meridional projection height from point a to point c.

3. The tip modification method for improving the aeroelastic stability of the blade according to claim 2, characterized in that, In step S1, the confirmation process of the tip chord length modification coefficient is as follows: Set the modified tip leading edge point as d. That is, the tip chord length modification coefficient is obtained based on the following calculation formula: ； Among them, is the tip chord modification coefficient, L1 is the length from the leading edge point a of the blade tip to the modified leading edge point d of the blade tip, and L is the chord length of the blade tip section.

4. The tip modification method for improving the aeroelastic stability of blades according to claim 3, characterized in that, In step S1, the confirmation process of the tip leading edge deflection angle is as follows: The blade includes a leading edge profile, a blade body, and a trailing edge profile. The profile of the blade body is confirmed based on the mean camber line and includes a pressure surface profile and a suction surface profile. Set the starting point of the modification of the suction surface profile as f, and set the starting point of the modification of the pressure surface profile as g. Then the intersection point of the mean camber line and gf is o, and the intersection point of the mean camber line and the modified blade leading edge profile is e. That is, the tip leading edge deflection angle θ = ∠doe and deflects towards the pressure surface profile.

5. The tip modification method for improving the aeroelastic stability of the blade according to claim 4, characterized in that, In step S1, the specific steps to obtain the modified theoretically designed blade are as follows: First, according to the blade height modification coefficient determine the positions of each cross-section of the rotor blade before modification. Then, modify the fourth cross-section according to the tip chord length modification coefficient while modifying the leading edge of the blade at the second and third cross-sections proportionally, keeping the first cross-section unchanged. Finally, during the modification process, the leading edge of each cross-section adopts an elliptical arc form with a local deflection towards the pressure surface according to the tip leading edge deflection angle θ, so as to obtain the theoretically designed blade after modification.

6. The tip modification method for improving the aeroelastic stability of the blade according to any one of claims 1-5, characterized in that, In step S2, the calculation and evaluation process of the aerodynamic performance of the theoretically designed blade is as follows: First, generate structured grids for the modified theoretically designed blade through grid drawing software to obtain the structured grids of the fluid domain; Then, the structured grids are set for calculation preprocessing through cfd preprocessing software and three - dimensional simulation calculations are performed; Finally, according to the calculation results, the flow rate, pressure ratio, efficiency, and margin of the fan / compressor are extracted and compared with the corresponding design indicators to determine whether it can meet the aerodynamic performance requirements.

7. The blade tip modification method for improving the aeroelastic stability of the blade according to any one of claims 1-5, characterized in that In step S2, the vibration strength calculation and evaluation process of the theoretically designed blade is as follows: First, the above-mentioned modified theoretically designed blade is modeled through UG software to obtain the UG model of the rotor blade disk, and then unstructured meshes of the solid domain are generated through mesh generation software. Then, the unstructured meshes are pre-processed for strength and vibration calculations through workbench pre-processing software, and three-dimensional simulation calculations are performed. Finally, according to the calculation results, the deformation, stress, frequency, vibration mode, and frequency dispersion of the theoretically designed blade are extracted and compared with the requirements of the corresponding strength and vibration design specifications to determine whether it can meet the strength and vibration requirements.

8. The tip modification method for improving the aeroelastic stability of blades according to any one of claims 1-5, characterized in that, In step S2, the aeroelastic stability calculation and evaluation process of the theoretically designed blade is as follows: Calculate the natural frequency and vibration mode of the theoretically designed blade, interpolate them onto the grids of the flow field calculation, make the theoretically designed blade move according to specific frequencies, phase angles, vibration modes, and amplitudes, and judge whether flutter occurs by calculating the positive and negative work done by the fluid on the blade within one vibration cycle.

9. The method for tip modification to improve the aeroelastic stability of the blade according to any one of claims 1-5, characterized in that In step S3, the specific process of machining and grinding is as follows: First, the blade profile of the tip region of the physical rotor blade with aeroelastic stability problems is measured to provide a reference basis for subsequent machining and grinding. Then, referring to the theoretically designed blade, the leading edge of the tip of the rotor blade is machined and ground using a numerical control milling lathe. Finally, the blade profile of the tip region of the rotor blade after grinding is measured again to determine whether the physical grinding meets the blade profile requirements of the modified theoretically designed blade.

10. The tip modification method for improving the aeroelastic stability of blades according to any one of claims 1-5, characterized in that In step S4, the specific test process of the fan / compressor component test is as follows: First, the physical modified blade is replaced and assembled to complete the assembly of the modified fan / compressor component test piece, and at the same time, the preparation work of the test bench and the test system is completed. Then, when the outlet throttle valve of the fan / compressor is opened, the speed of the component test piece is pushed to the set speed, and then the outlet throttle valve is continuously closed until a surge signal is detected at the outlet, and then the throttle valve is opened to complete the performance recording at this speed. Finally, the speed of the component test piece is pushed to different speeds to complete the performance recording at different speeds. During the test process, pay attention to the real-time changes of the tip amplitude, dynamic stress, and dynamic pressure. Once the monitored parameters are abnormal, pull down the speed to stop the test, indicating that there are aeroelastic stability problems with the physical modified blade. If the monitored parameters of the tip amplitude, dynamic stress, and dynamic pressure do not show abnormalities during the whole test process, it indicates that there are no aeroelastic stability problems with the physical modified blade.

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