Frequency modulation method based on leaf object

Abstract

The invention discloses a frequency modulation method based on a blade object, and belongs to the technical field of moving blade frequency modulation. The method comprises the steps that the potential airflow excitation frequency of the moving blade is obtained; acquiring the actually measured inherent frequencies of multiple orders of the moving blade real object; establishing a blade three-dimensional model based on the three-coordinate measurement data of the old moving blade real object; obtaining a plurality of order theoretical inherent frequencies and corresponding vibration modes of the moving blade; identifying a failure mode of the blade, and judging a vibration mode corresponding to the failure mode of the blade; and according to the vibration mode corresponding to the blade failure mode, frequency modulation is carried out on the moving blade entity until the avoidance rate meets the design requirement. According to the frequency modulation method, the problem of inflexible or ineffective frequency modulation caused by a method for carrying out frequency modulation by an original design theoretical model when the blade profile of the moving blade is abraded or corroded and the problem of low frequency correction efficiency depending on pure experience are solved.

Description

Technical Field

[0001] The invention relates to the technical field of blade frequency modulation, and in particular to a frequency modulation method based on a blade object. Background Art

[0002] In actual operating conditions, the moving blades of TRT (blast furnace gas residual pressure turbine power generation device) are more or less subject to corrosion, erosion or wear, which causes the moving blades to become thinner to varying degrees, thereby causing changes in the natural frequency of the moving blades and inducing resonance fatigue damage of the moving blades.

[0003] In this regard, the prior art usually conducts modal analysis based on the theoretical model in the design stage to obtain the natural frequency and vibration mode of the moving blades, calculates the avoidance rate between the natural frequency of the moving blades and the airflow excitation frequency, and performs blade optimization frequency adjustment when the avoidance rate requirement is not met, and then guides the actual frequency adjustment of the moving blades in production. The above method has certain defects. Since the actual TRT moving blades deviate seriously from the theoretical model after running for a period of time, the thinning amount of different areas of the moving blades is also different. The method of frequency adjustment based on the theoretical model in the design stage will be ineffective or fail; when there is no theoretical model in the design stage, modal analysis cannot be carried out; although the frequency can be obtained by measuring the actual frequency of the blades, the vibration mode cannot be obtained. The only way to try to adjust the frequency is based on experience. The efficiency of this method of trial frequency adjustment and frequency adjustment is very low; once the adjustment is wrong, it cannot be returned, which will cause the moving blades to be scrapped and cannot be used again. Summary of the invention

[0004] The purpose of the present invention is to overcome the problems in the prior art and provide a frequency modulation method based on actual blades. The frequency modulation method of the present invention is based on actual blades, avoiding the problem of frequency modulation inefficiency or failure caused by the method of frequency modulation relying solely on the original design theoretical model. The frequency modulation method of the present invention can be used for emergency repair of old moving blades and for optimizing the design of new brake blades based on the actual old moving blades, thereby increasing the service life of the new brake blades while reducing the economic losses caused during the design and manufacture of the new brake blades.

[0005] The present invention is based on the frequency modulation method of the blade object, and based on the number of the actual static blades, obtains the potential airflow excitation frequency of the old moving blades;

[0006] Conduct physical frequency measurement on the old rotor blades to obtain the actual measured natural frequencies of multiple orders of the old rotor blades;

[0007] A three-dimensional solid model of the old moving blade is established based on the three-dimensional measurement data of the old moving blade, and a modal analysis is performed on the three-dimensional solid model of the old moving blade to obtain the theoretical natural frequencies of multiple orders of the old moving blade and the corresponding vibration shapes;

[0008] The failure mode of the blade is identified by combining the damage of the old rotor blade, the measured natural frequencies of each order of the old rotor blade, the theoretical natural frequencies of each order and their corresponding modal vibration shapes, and the vibration shape corresponding to the failure mode of the blade is determined;

[0009] The frequency of the actual moving blade is modulated according to the vibration mode corresponding to the blade failure mode and the airflow excitation frequency until the avoidance rate meets the design requirements.

[0010] As an optimized implementation method, before the physical frequency measurement of the old moving blades, the old moving blades are first inspected physically. According to the inspection results, 3-5 old moving blades without cracks or with crack lengths less than 5 mm are selected for physical frequency measurement;

[0011] As an optimized implementation method, the measured natural frequencies of at least the first 4-6 orders of the old moving blades are tested, and the average natural frequencies of multiple old moving blades at the same order are calculated;

[0012] Select at least 5 sections from the bottom of the blade upward along the blade height direction to obtain the profile data on the sections;

[0013] According to the profile data of each section obtained by three-dimensional coordinate measurement, a three-dimensional solid model of the old rotor blade is established;

[0014] The modal calculation is performed on the three-dimensional solid model of the old moving blades to obtain the modal frequencies and corresponding vibration shapes of multiple orders of each old moving blade.

[0015] As an optimized implementation method, when identifying the failure mode of the old rotor blade, the following conditions must be met at the same time:

[0016] The crack form or fracture form of the old moving blade is the same as the modal vibration mode of a certain order in the modal calculation;

[0017] Furthermore, the avoidance rate between the measured natural frequency of the corresponding order and the potential airflow excitation frequency of the moving blade is less than or equal to 12%.

[0018] As an optimized implementation method, the frequency of the old moving blades is modulated according to the order vibration mode corresponding to the failed blade mode until the avoidance rate is ≥ 12%.

[0019] As an optimized implementation method, the measured natural frequencies of at least the first 4-6 orders of the old moving blades are tested, and the average natural frequencies of multiple old moving blades at the same order are calculated; the average natural frequencies of multiple old moving blades at the same order are calculated as the measured natural frequencies corresponding to each order after returning to the factory, and the measured natural frequencies corresponding to each order of the old moving blades before leaving the factory and after returning to the factory are compared to obtain the change in the measured natural frequencies of at least the first 4-6 orders before leaving the factory and after returning to the factory;

[0020] Select N sections from the bottom of the blade upward along the blade height direction to obtain the profile data on the sections. The selected N sections are required to be exactly the same as the number and height of the blade sections when the original design model of the old rotor blade is modeled;

[0021] According to the profile data of each section obtained by three-dimensional coordinate measurement, a three-dimensional solid model of the old rotor blade is established, that is, a three-dimensional model of the old rotor blade after it is returned to the factory;

[0022] Compare and analyze the original design model of the old rotor blade before leaving the factory and the 3D model after returning to the factory to obtain the change of the blade profile line of each section;

[0023] Modal calculations were performed on the original design model of the old moving blades before leaving the factory and the three-dimensional model after returning to the factory, respectively, to obtain multiple orders of modal frequencies and corresponding vibration shapes of the old moving blades before leaving the factory and after returning to the factory.

[0024] As an optimized implementation method, when identifying the failure mode of the old rotor blade, the following conditions must be met at the same time:

[0025] The crack form or fracture form of the old moving blade is the same as the modal vibration mode of a certain order in the modal calculation;

[0026] Furthermore, the avoidance rate between the measured natural frequency of the corresponding order and the potential airflow excitation frequency of the moving blade is less than or equal to 15%.

[0027] Frequency-modulate the old moving blades according to the order vibration mode corresponding to the failed blade mode until the avoidance rate is ≥15%;

[0028] According to the changes in the theoretical natural frequencies of each order of the old moving blades before leaving the factory and after returning to the factory and the changes in the measured natural frequencies of the corresponding orders, the changes in the blade profile lines of each section of the theoretical model of the old moving blades are converted, thereby obtaining the blade profile lines of the newly designed moving blades.

[0029] As an optimized implementation method, after determining the blade profile of the newly designed moving blades, the unit performance analysis is carried out on the old moving blade profiles and the newly designed moving blade profiles to obtain the change in unit performance efficiency Δη. The standard requirement is Δη<1%. If it does not meet the standard, the frequency is adjusted again until Δη<1% is met.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] The frequency modulation method of the present invention is based on the actual static blades and moving blades of the rotor, and calculates the potential airflow excitation frequency of the moving blades through the number of actual static blades; at the same time, combined with the frequency measurement results of the actual old moving blades and the modal analysis results of the moving blade three-dimensional model established based on the actual measurement of the old moving blades, the dangerous vibration mode (vibration type) of the moving blades is compared and analyzed; then combined with the flaw detection results, modal analysis and the actual frequency measurement results of the old moving blades, the failure mode of the actual old moving blades is identified; based on the failure mode of the actual old moving blades, the actual dangerous vibration mode of the old moving blades and the potential airflow excitation frequency of the moving blades, a moving blade frequency modulation method of the corresponding order modal vibration mode is formulated. The above-mentioned frequency modulation method of the present invention avoids the problem of ineffective or malfunctioning frequency modulation caused by the original design theoretical model for frequency modulation when the actual blade shape of the moving blade is worn or corroded, as well as the problem of low efficiency of frequency repair relying on pure experience.

[0032] The present invention establishes an emergency repair plan and an optimization and improvement plan based on the above-mentioned frequency modulation method. The emergency repair plan is to perform frequency modulation and frequency repair on the old moving blades, which can help users resume production in a relatively short time and reduce economic losses; the optimization and improvement plan of the present invention is to optimize and improve the new brake blades based on the failure mode of the original old moving blades, which can achieve long-term stable operation of the TRT unit. The present invention can achieve the goal of increasing the service life of new blades while reducing the economic losses caused during the design and manufacture of new blades by combining the emergency repair plan and the optimization and improvement plan. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 The figure is a flow chart of a frequency modulation method according to an embodiment of the present invention.

[0034] Figure 2 The present invention is a flowchart of an emergency repair solution established based on the frequency modulation method of the present invention.

[0035] Figure 3 The present invention is a flowchart of a moving blade optimization and improvement program based on the frequency modulation method of the present invention. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical solution and advantages of the embodiments of the present disclosure clearer, the technical solution of the embodiments of the present disclosure will be clearly and completely described below in conjunction with the drawings of the embodiments of the present disclosure. Obviously, the described embodiments are part of the embodiments of the present disclosure, not all of the embodiments. Based on the described embodiments of the present disclosure, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present disclosure.

[0037] Unless otherwise defined, the technical terms or scientific terms used herein should be understood by people with ordinary skills in the field to which the present disclosure belongs. "First", "second" and similar words used in the present disclosure do not indicate any order, quantity or importance, but are only used to distinguish different components. "Including" or "comprising" and similar words mean that the elements or objects appearing in front of "including" or "comprising" cover the elements or objects listed after "including" or "comprising" and their equivalents, and do not exclude other elements or objects. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0038] like Figure 1 As shown, the frequency modulation method based on the blade object of the present invention includes:

[0039] Based on the number of physical static blades, the potential airflow excitation frequency of the old moving blades is obtained;

[0040] Perform physical frequency measurement on the old rotor blades to obtain the measured natural frequencies of multiple orders of the old rotor blades. As a preferred method, we at least obtain the measured natural frequencies of the first 4-6 orders;

[0041] Different from the current conventional operation, in this embodiment, the three-dimensional model for modal analysis does not directly adopt the theoretical three-dimensional model of the old moving blade in the original design stage, but establishes a three-dimensional solid model of the old moving blade based on the old blade. By performing modal analysis on the three-dimensional solid model of the old moving blade, the theoretical natural frequencies of multiple orders of the old moving blade and the corresponding vibration modes are obtained;

[0042] This embodiment also identifies the failure mode of the blade in combination with the damage of the old rotor blade, specifically the crack form or fracture form of the old rotor blade, the measured natural frequencies of each order of the old rotor blade and the theoretical natural frequencies corresponding to the modal vibration shapes, and determines the order modal vibration shape of the modal analysis corresponding to the blade failure mode;

[0043] The frequency of the actual moving blade is modulated according to the corresponding order mode vibration shape until the avoidance rate meets the design requirements.

[0044] In this embodiment, based on the above-mentioned frequency modulation method, an emergency repair plan for old moving blades and / or an optimization and improvement plan for moving blades are respectively established, wherein the emergency repair plan for old moving blades is used to repair the old moving blades in kind; and the optimization and improvement plan for moving blades is used to optimize the design of new moving blades based on the old blades in kind.

[0045] As an optimized implementation method, the old moving blades are first physically inspected before physical frequency measurement is performed on them, and then 3-5 old moving blades without cracks or with crack lengths less than 5 mm are selected for physical frequency measurement based on the inspection results; the inventors have found through long-term research that for moving blades with cracks, the results obtained when physical frequency measurement is performed on old moving blades with crack lengths less than 5 mm are relatively reliable. As a preferred method, a corresponding solution is given for the situation where all physical blades have cracks or fractures to varying degrees, and therefore it is impossible to find completely crack-free old moving blades or the number of completely crack-free old moving blades does not meet the minimum requirement for the number of old moving blades for physical frequency measurement.

[0046] When the frequency modulation method is used to establish an emergency repair plan for old moving blades, each old moving blade is tested for at least the first 4-6 orders of measured natural frequencies, and the average natural frequencies of multiple old moving blades at the same order are calculated; this embodiment selectively selects the type and quantity of old moving blades for physical frequency measurement, and after each measurement, obtains the overall situation of the old moving blades in the working environment of the rotor by taking the average value of each order.

[0047] When the frequency modulation method is used to establish an optimization and improvement plan for moving blades: the natural frequencies of at least the first 4-6 orders of each old moving blade are tested and the average natural frequencies of multiple old moving blades at the same order are calculated, and the measured natural frequencies corresponding to each order of the old moving blades before leaving the factory and after returning to the factory are compared to obtain the change in the measured natural frequencies of at least the first 4-6 orders before leaving the factory and after returning to the factory. Different from establishing an emergency repair plan for old moving blades, the optimization design of the new brake blades fully considers the change rate of the measured natural frequencies of the original old blades before and after leaving the factory, so that the newly manufactured moving blades can better adapt to the working environment in which they will be operated in the later stage.

[0048] As an optimized implementation method, when the frequency modulation method is used to establish an emergency repair plan for old rotor blades, the specific method for establishing a three-dimensional solid model of the old rotor blades is as follows:

[0049] Select at least 5 sections from the bottom of the blade upward along the blade height direction to obtain the profile data on each section;

[0050] According to the profile data of each section obtained by three-dimensional coordinate measurement, a three-dimensional solid model of the old rotor blade is established;

[0051] Perform modal calculation on the three-dimensional solid model of the old moving blades to obtain the theoretical natural frequencies of multiple orders of each old moving blade and the corresponding vibration mode;

[0052] When the frequency modulation method is used to establish a moving blade optimization improvement plan, the specific method for establishing a moving blade three-dimensional solid model is as follows:

[0053] Select N sections from the bottom of the blade upward along the blade height direction to obtain the profile data on the sections. The selected N sections are required to be exactly the same as the number and height of the blade sections when the original design model of the old blade was modeled.

[0054] According to the profile data of each section obtained by three-dimensional coordinate measurement, a three-dimensional solid model of the old rotor blade is established, that is, a three-dimensional model of the old rotor blade after it is returned to the factory;

[0055] Compare and analyze the original design model of the moving blade before leaving the factory and the 3D model after returning to the factory to obtain the blade profile change of each section;

[0056] Modal calculations were performed on the original design model of the moving blade before it left the factory and the three-dimensional model after it returned to the factory, respectively, to obtain theoretical natural frequencies and corresponding vibration modes of multiple orders of the moving blade before it left the factory and after it returned to the factory;

[0057] The theoretical natural frequencies corresponding to the modal vibration modes of each order of the moving blades before leaving the factory and after returning to the factory are compared and analyzed to obtain the theoretical natural frequency changes corresponding to the modal vibration modes of each order before leaving the factory and after returning to the factory. In this embodiment, whether it is when establishing the optimization and improvement plan for the moving blades or when establishing the emergency repair plan for the old moving blades, the establishment of the three-dimensional model is based on the actual old moving blades, and when establishing the optimization and improvement plan for the moving blades, the theoretical natural frequency changes corresponding to the modal vibration modes of each order of the moving blades before and after leaving the factory are also considered again, so that the newly designed moving blades can be optimized and adjusted again, so that the newly designed moving blades can better adapt to the working environment in which they are operated in the later stage.

[0058] As an optimized implementation method, when the frequency modulation method is used to establish a moving blade optimization improvement plan,

[0059] The frequency of the moving blade is theoretically modulated according to the order vibration mode corresponding to the failed blade mode until the avoidance rate requirement is met;

[0060] According to the theoretical natural frequency changes corresponding to the modal vibration modes of each order of the blade before leaving the factory and after returning to the factory and the changes in the measured natural frequencies of the corresponding orders, the changes in the blade profiles of each section of the theoretical model of the moving blade are converted, thereby obtaining the blade profiles of the newly designed moving blades. The simplest method in the prior art may be to directly use the design scheme of the original design stage of the old moving blades to make the moving blades, but the moving blades made in this way are relatively more versatile and can better meet the use needs of different customer groups, and have a low degree of matching with the current working environment of the moving blades. The blade profiles of the newly designed moving blades in this embodiment are based on the theoretical natural frequency changes corresponding to the modal vibration modes of each order of the blades before leaving the factory and after returning to the factory and the changes in the measured natural frequencies of the corresponding orders, so the newly designed moving blades can better adapt to the later working environment. Compared with the method of directly using the design scheme of the original design stage of the old blades to make the moving blades, the new brake blades in this embodiment have a better degree of matching with the working environment, so they have a longer service life in this working environment.

[0061] As an optimized implementation method, when the frequency modulation method is used to establish an optimization and improvement plan for moving blades, after determining the blade profile of the newly designed moving blades, a unit performance analysis is carried out on the old moving blade profiles and the newly designed moving blade profiles to obtain the change in unit performance efficiency Δη. The standard requirement is Δη<1%. If the standard is not met, the frequency is readjusted until it is met. If the standard is not met, the frequency is adjusted again until Δη<1%.

[0062] As an optimized implementation method, when identifying the failure mode of the blade, the following conditions must be met at the same time:

[0063] The crack form or fracture form of the old moving blade is the same as the modal vibration mode of a certain order in the modal calculation;

[0064] And the avoidance rate of the measured natural frequency of the corresponding order and the potential airflow excitation frequency of the moving blade meets the requirements;

[0065] The avoidance rate satisfies the requirement that: when the frequency modulation method is used to establish an emergency repair plan for old moving blades, the avoidance rate is less than or equal to 12%; when the frequency modulation method is used to establish an optimization and improvement plan for moving blades, the avoidance rate is less than 15%.

[0066] Correspondingly, when the frequency modulation method is used to establish an emergency repair plan for old moving blades, the frequency modulation target in the frequency modulation stage is an avoidance rate ≥ 12%; when the frequency modulation method is used to establish a moving blade optimization and improvement plan, the frequency modulation target in the frequency modulation stage is an avoidance rate ≥ 15%.

[0067] In this embodiment, whether establishing an emergency repair plan for old moving blades or establishing a moving blade optimization and improvement plan, the avoidance rate is designed to be higher than the industry requirement of 10%, thereby increasing the safety margin of the avoidance rate.

[0068] As an optimized implementation method, after all the old moving blades have been frequency-modulated or after the newly designed moving blades have been manufactured and tested to be qualified, the moving blades are weighed and sorted to ensure that the dynamic balance of the rotor is qualified.

[0069] TRT moving blades are core energy conversion components. Once a problem occurs, the unit will shut down due to large vibrations, causing significant economic losses. Identifying the failure mechanism of old moving blades, responding quickly to user needs, and formulating targeted emergency repair plans and optimization and improvement plans for blades are urgent topics that need to be tackled.

[0070] The method for frequency modulation based on blade objects of the present invention is described below in detail in the form of specific embodiments:

[0071] Example 1

[0072] like Figure 2 As shown, in this embodiment, the method for establishing an emergency repair plan for moving blades based on the above frequency modulation method is as follows:

[0073] (1) Physical flaw detection of old moving blades. For the sake of convenience, the old moving blades are referred to as moving blades below: When the TRT unit is shut down and the cover is opened, it is found that the moving blades are worn, corroded, eroded, etc., causing the blade angle to fall off. The moving blades on the rotor are disassembled, cleaned to meet the flaw detection requirements, and then flaw detection is performed. Usually, magnetic particle flaw detection or color flaw detection is required, and magnetic particle flaw detection is preferred;

[0074] (2) Frequency measurement of actual moving blades: Based on the flaw detection results, select 3-5 blades without cracks or with small cracks (crack length less than 5 mm) for frequency measurement, obtain at least the first 6 natural frequencies of the blades, and obtain the average value f′ of the measured natural frequencies of multiple actual moving blades at the same order. i , where i = 1, n, n ≥ 6;

[0075] (3) Three-dimensional measurement of the actual moving blade: select N sections from the bottom of the blade upward along the blade height direction to obtain the profile data on the section, N ≥ 5;

[0076] (4) 3D solid modeling of moving blades: Based on the cross-sectional profile data obtained by three-dimensional coordinate measurement, a 3D solid model of the blade is established using 3D CAD software;

[0077] (5) Finite element modal calculation of moving blades: Use finite element software to perform modal calculation on the three-dimensional solid model of the blade to obtain the theoretical natural frequency f of the blade. i and the corresponding vibration mode A i , where i = 1, n, n ≥ 6;

[0078] (6) Calculation of airflow excitation frequency of moving blades: The number of stationary blades is m, the TRT generator operating speed is 3000 r / min, the base frequency is 50 Hz, and F f =m×50=50m(Hz);

[0079] (7) Failure mode of moving blades:

[0080] 1) Observe the crack form or fracture form of the blade with obvious cracks in the flaw detection and the kth order vibration mode A in the modal calculation k Same, 1≤k≤n;

[0081] 2) Calculate f′ k With F f Avoidance rate δ k , δ k <12%;

[0082] 3) 1) and 2) are satisfied, and the failure mode of the moving blade is determined to be k-th order vibration mode vibration resonance fatigue failure.

[0083] (8) Frequency modulation scheme for moving blades: Frequency modulation is performed on the moving blades according to the kth order vibration mode, and the frequency modulation target is δ k ≥12%.

[0084] (9) Emergency repair plan: All moving blades shall be frequency-modulated according to the above-mentioned moving blade frequency modulation plan, and the moving blades after frequency modulation shall be weighed and sorted to ensure that the dynamic balance of the rotor is qualified. The rotor can be put into operation only after dynamic balancing.

[0085] Example 2

[0086] like Figure 3 As shown, in this embodiment, the method for establishing a moving blade optimization improvement plan based on the above frequency modulation method is as follows:

[0087] (1) Physical flaw detection of moving blades: When the TRT unit is shut down and the cover is opened, it is found that the moving blades are worn, corroded, eroded, etc., causing the blade angle to fall off. The moving blades on the rotor are removed and cleaned to meet the flaw detection requirements, and then flaw detection is performed. Magnetic particle flaw detection or color flaw detection is usually required, with magnetic particle flaw detection being preferred;

[0088] (2) Frequency measurement of actual moving blades: Based on the flaw detection results, select 3-5 blades without cracks or with small cracks (crack length less than 5 mm) for frequency measurement, obtain at least the first 6 natural frequencies of the blades, and obtain the average value f′ of the measured natural frequencies of multiple actual moving blades at the same order. i，j , where i=1, n, n≥6, j=1 means after returning to the factory;

[0089] (3) Comparison of the actual frequency of the moving blades before leaving the factory and after returning to the factory: Check the frequency f′ before leaving the factory i，j, where i = 1, n, n ≥ 6, j = 0 means before leaving the factory; the difference between before leaving the factory and after returning to the factory is Δf′ i ;

[0090] (4) Three-dimensional measurement of the actual moving blade: select N sections from the bottom of the blade upward along the blade height direction to obtain the profile data on the section. The number and height of the blade sections must be exactly the same as when the original design model was built.

[0091] (5) Three-dimensional solid modeling of moving blades: Based on the cross-sectional profile data obtained by three-dimensional coordinate measurement, a three-dimensional solid model of the blade is established using three-dimensional CAD software;

[0092] (6) Comparative analysis of the three-dimensional model of the moving blade before leaving the factory and after returning to the factory: Obtain the blade profile change Δh of each section i , where i = 1, N;

[0093] (7) Finite element modal calculation of moving blades: Finite element software is used to perform modal calculations on the three-dimensional models of moving blades before and after they are returned to the factory to obtain the theoretical natural frequency f of the blades. i，j and the corresponding vibration mode A i , where i=1, n, j=0, 1, n≥6, j=0 means before leaving the factory, j=1 means after returning to the factory;

[0094] (8) Comparative analysis of the theoretical natural frequency of the moving blades before leaving the factory and after returning to the factory: The change Δf before leaving the factory and after returning to the factory is obtained i , where i = 1, N;

[0095] (9) Calculation of airflow excitation frequency of moving blades: The number of stationary blades is m. Assuming that the TRT generator operates at a speed of 3000 r / min and a base frequency of 50 Hz, then F f =m×50=50m(Hz);

[0096] (10) Failure mode of moving blades:

[0097] 1) Observe the crack form or fracture form of the blade with obvious cracks in the flaw detection and the kth order vibration mode A in the modal calculation k Same, k=1,n;

[0098] 2) Calculate the average value f' of the measured natural frequency corresponding to the Kth order vibration mode k With F f The avoidance rate δ k , δ k <15%;

[0099] 3) 1) and 2) are satisfied, and the failure mode of the moving blade is determined to be k-th order vibration mode vibration resonance fatigue failure.

[0100] (11) Frequency modulation scheme of moving blades:

[0101] 1) According to the kth order vibration mode, the frequency of the moving blade is theoretically modulated, and the frequency modulation target is δ k ≥15%;

[0102] 2) Based on the change in the theoretical natural frequency of the blade before leaving the factory and after returning to the factory, Δf k and the change in the measured natural frequency of the blade Δf′ k , and calculate the change of blade profile of each section of the theoretical model of the moving blade Δh″ k , thus obtaining the new blade profile.

[0103] (12) Performance optimization: CFD is used to analyze the unit performance of the original and new blade profiles to obtain the change in unit performance efficiency Δη, and the compliance requirement is Δη < 1%;

[0104] (13) Optimization and improvement plan:

[0105] 1) According to the above-mentioned moving blade frequency modulation method, the moving blade theoretical model is frequency modulated to obtain a new blade profile;

[0106] 2) CFD simulation analysis is used to calculate the performance and the performance meets the standard;

[0107] 3) Produce blades according to the new blade shape. After passing the quality inspection and frequency measurement, they are weighed and sorted to ensure that the dynamic balance of the rotor is qualified. The rotor can only be put into operation after dynamic balancing.

[0108] The emergency repair plan in this embodiment can usually be completed within 7 working days. The emergency repair plan in this embodiment makes full use of the old blades, which can significantly shorten the production recovery cycle and reduce the economic losses of users. This emergency repair plan is particularly suitable for solving problems such as blade angle loss. The above-mentioned emergency repair method in this embodiment is applied to a TRT unit in a steel plant. The unit has been operating safely and stably for more than 5 months. Practice has shown that the emergency repair plan is feasible.

[0109] The optimization and improvement scheme of this embodiment is an optimization and improvement made on the blade profile of the old moving blades, which improves the blade frequency avoidance rate safety margin, takes into account the unit performance, and at the same time, all parts except the moving blades can be reused. It was applied to solve the problem of blade corner drop in a certain steel TRT, and the life of the moving blades was increased from the original 4-7 months to more than 2 years, successfully solving the user's moving blade failure problem. Practice shows that this optimization and improvement scheme is very effective.

[0110] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A frequency modulation method based on blade objects, characterized in that: include: Based on the number of physical static blades, the potential airflow excitation frequency of the old moving blades is obtained; Conduct physical frequency measurement on the old rotor blades to obtain the actual measured natural frequencies of multiple orders of the old rotor blades; A three-dimensional solid model of the old moving blade is established based on the three-dimensional measurement data of the old moving blade, and a modal analysis is performed on the three-dimensional solid model of the old moving blade to obtain the theoretical natural frequencies of multiple orders of the old moving blade and the corresponding vibration shapes; The failure mode of the blade is identified by combining the damage of the old rotor blade, the measured natural frequencies of each order of the old rotor blade, the theoretical natural frequencies of each order and their corresponding modal vibration shapes, and the vibration shape corresponding to the failure mode of the blade is determined; The frequency of the actual moving blade is modulated according to the vibration mode corresponding to the blade failure mode and the airflow excitation frequency until the avoidance rate meets the design requirements.

2. The frequency modulation method based on blade objects according to claim 1, characterized in that: Before performing physical frequency measurement on the old moving blades, the old moving blades are first subjected to physical flaw detection. Based on the flaw detection results, 3 to 5 old moving blades without cracks or with crack lengths less than 5 mm are selected for physical frequency measurement.

3. The frequency modulation method based on blade objects as claimed in claim 1, characterized in that: The old rotor blades are physically tested for at least the first 4-6 orders of measured natural frequencies, and the average natural frequencies of multiple old rotor blades at the same order are calculated; Select at least 5 sections from the bottom of the blade upward along the blade height direction to obtain the profile data on the sections; According to the profile data of each section obtained by three-dimensional coordinate measurement, a three-dimensional solid model of the old rotor blade is established; The modal calculation is performed on the three-dimensional solid model of the old moving blades to obtain the modal frequencies and corresponding vibration shapes of multiple orders of each old moving blade.

4. The frequency modulation method based on blade objects as claimed in claim 3 is characterized in that: When identifying the failure mode of old rotor blades, the following conditions must be met at the same time: The crack form or fracture form of the old moving blade is the same as the modal vibration mode of a certain order in the modal calculation; Furthermore, the avoidance rate between the measured natural frequency of the corresponding order and the potential airflow excitation frequency of the moving blade is less than or equal to 12%.

5. The frequency modulation method based on blade objects as claimed in claim 4, characterized in that: The frequency of the old moving blades is modulated according to the order vibration mode corresponding to the failed blade mode until the avoidance rate is ≥ 12%.

6. The frequency modulation method based on blade objects as claimed in claim 1, characterized in that: The measured natural frequencies of at least the first 4-6 orders of the old moving blades are tested, and the average natural frequencies of multiple old moving blades at the same order are calculated; the average natural frequencies of multiple old moving blades at the same order are calculated as the measured natural frequencies corresponding to each order after returning to the factory, and the measured natural frequencies corresponding to each order of the old moving blades before leaving the factory and after returning to the factory are compared to obtain the change in the measured natural frequencies of at least the first 4-6 orders before leaving the factory and after returning to the factory; Select N sections from the bottom of the blade upward along the blade height direction to obtain the profile data on the sections. The selected N sections are required to be exactly the same as the number and height of the blade sections when the original design model of the old rotor blade is modeled; According to the profile data of each section obtained by three-dimensional coordinate measurement, a three-dimensional solid model of the old rotor blade is established, that is, a three-dimensional model of the old rotor blade after it is returned to the factory; Compare and analyze the original design model of the old rotor blade before leaving the factory and the 3D model after returning to the factory to obtain the change of the blade profile line of each section; Modal calculations were performed on the original design model of the old moving blades before leaving the factory and the three-dimensional model after returning to the factory, respectively, to obtain multiple orders of modal frequencies and corresponding vibration shapes of the old moving blades before leaving the factory and after returning to the factory.

7. The frequency modulation method based on blade objects as claimed in claim 6, characterized in that: When identifying the failure mode of old rotor blades, the following conditions must be met at the same time: The crack form or fracture form of the old moving blade is the same as the modal vibration mode of a certain order in the modal calculation; Furthermore, the avoidance rate between the measured natural frequency of the corresponding order and the potential airflow excitation frequency of the moving blade is less than or equal to 15%.

8. The frequency modulation method based on blade objects as claimed in claim 7, characterized in that: Frequency-modulate the old moving blades according to the order vibration mode corresponding to the failed blade mode until the avoidance rate is ≥15%; According to the changes in the theoretical natural frequencies of each order of the old moving blades before leaving the factory and after returning to the factory and the changes in the measured natural frequencies of the corresponding orders, the changes in the blade profile lines of each section of the theoretical model of the old moving blades are converted, thereby obtaining the blade profile lines of the newly designed moving blades.

9. The frequency modulation method based on blade objects as claimed in claim 8, characterized in that: After determining the blade profile of the newly designed moving blade, the unit performance analysis is carried out on the old moving blade profile and the newly designed moving blade profile to obtain the change in unit performance efficiency Δη. The standard requirement is Δη<1%. If it does not meet the standard, the frequency is adjusted again until Δη<1% is met.

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