Method for dynamic balancing of an engine flexible rotor system across cells

Abstract

This invention relates to a dynamic balancing method for a flexible rotor system in an engine, belonging to the technical field of mechanical rotor dynamic balancing. It is applicable to the dynamic balancing of low-pressure rotors or power turbine rotors in turbofan engines when using flexible rotors. The turbofan engine includes a compressor blade disk and a hollow connecting long shaft. The dynamic balancing method includes: S1, inspection of the manufacturing process; S2, dynamic balancing tests on the connecting long shaft and blade disk respectively; S3, assembly and testing of the connecting long shaft and blade disk bearing the first identification on the test bench of the dynamic balancing device according to design requirements; S4, checking whether the dynamic indicators meet the standards; S5, full-range speed vibration testing of the connecting long shaft and blade disk as a whole on the platform of a rotor dynamics experimental apparatus; and S6, verification of the repeatability of assembly parameters and dynamic balancing, thus improving the efficiency of dynamic balancing.

Description

Technical Field

[0001] This invention belongs to the technical field of dynamic balancing of mechanical rotors, and particularly relates to a dynamic balancing method for a flexible rotor system of an engine across unit cells. Background Technology

[0002] As a core component of aircraft, the performance and reliability of aero engines directly affect flight safety and efficiency. The rotor system of an aero engine endures high speeds, complex loads, and extreme operating conditions during operation, placing stringent requirements on its dynamic stability. Vibration failure statistics show that rotor imbalance is one of the key factors causing engine vibration. The resulting vibration directly affects the lifespan of engine components, the structural integrity of critical components, seriously impacting engine performance, and even threatening flight safety. Currently, the more mature dynamic balancing methods are mainly modal balancing, influence coefficient balancing, and holographic balancing.

[0003] Modal balancing requires experimental measurement or numerical calculation to obtain the rotor's modal parameters, which is relatively complex. When the system damping has a large influence, the mode shape is not easy to measure accurately, and it is not easy to obtain a single mode shape. Furthermore, the judgment of critical speed, nodes, and principal mode shape will affect the dynamic balancing results.

[0004] The improvement of the influence coefficient method mainly focuses on optimizing the mass of the test weight added during rotor balancing and the residual vibration after adding the test weight. In order to obtain an accurate influence coefficient, it is necessary to start and stop multiple times, resulting in low balancing efficiency and inconvenience to practical application. In addition, it has low sensitivity to high-order arrays.

[0005] When applying the holographic balancing method to actual field balancing, it still faces many challenges, such as high cost, long balancing cycle due to multiple start-ups, high test requirements and safety levels, and inability to achieve field dynamic balancing, field replacement and rapid replacement.

[0006] In summary, traditional methods require combined dynamic balancing of rotor systems. However, combined dynamic balancing of flexible rotors places high demands on operators, and it is also impossible to perform combined dynamic balancing in the field. The overall process is time-consuming and complex, resulting in low efficiency of dynamic balancing methods. Summary of the Invention

[0007] The dynamic balancing method for a flexible rotor system across multiple units in an engine provided by this invention solves the technical problem of low efficiency in existing dynamic balancing methods. The technical solution of this invention has many beneficial effects, as described below:

[0008] A dynamic balancing method for a flexible rotor system of an engine across unit cells is disclosed, applicable to the dynamic balancing of the low-pressure rotor or power turbine rotor of a turbofan engine using a flexible rotor. The turbofan engine includes a compressor blade disk and a hollow connecting long shaft. The blade disk includes a compressor disk, a fan disk, and a turbine disk. The dynamic balancing method includes...

[0009] S1: Inspection of the manufacturing process to ensure the fit of the connecting long shaft and blade disk after assembly at the factory;

[0010] S2: The connecting long shaft and blade disk are subjected to dynamic balancing tests to eliminate vibrations caused by imbalance. The connecting long shaft and blade disk that pass the test are marked with the first identification mark.

[0011] S3: The connecting shaft and blade disk with the first mark are assembled on the bench of the dynamic balancing test device according to the design requirements for assembly and testing to eliminate the new imbalance. After the assembly and testing are qualified, the second mark is marked.

[0012] S4: The connecting long shaft and blade disk with the second mark are removed from the stand and placed on the platform of the rotor dynamics tester for dynamic testing to check whether the dynamic indicators meet the standards.

[0013] S5: The entire connection shaft and blade disk are subjected to full-range speed vibration testing on the platform of the rotor dynamics tester. Specifically, the vibration response of the entire connection shaft and blade disk in multiple speed ranges defined by the engine specifications is tested to see if they meet the standard vibration response. If yes, it is marked as qualified; otherwise, it is marked as unqualified, and the process returns to step S3 to adjust the parameters until the standard vibration response is met.

[0014] S6: Repeatability verification of assembly parameters and dynamic balance. The connecting long shaft and blade disk are disassembled and re-inspected according to steps S2 to S5. If the inspection results of each step meet the standards, it is marked as finally qualified. If the inspection results of any step S2 to S5 do not meet the standards, return to step S2 to adjust the parameters and re-inspect until the inspection results of each step meet the standards.

[0015] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects:

[0016] This method can solve the problems of poor adaptability of flexible rotor dynamic balancing to the external field, dependence on combined dynamic balancing, and low dynamic balancing efficiency. Based on the design concept of "precise prefabrication, distributed verification, dynamic monitoring and repeatability verification", it reduces the requirements for operators, can perform combined dynamic balancing in the field, is simple to operate, and reduces the requirement for high precision in the dynamic balancing process. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a flowchart of the method of the present invention. Detailed Implementation

[0019] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0020] It should be noted that various aspects of embodiments within the scope of the appended claims are described below. It will be apparent that the aspects described herein can be embodied in a wide variety of forms, and any particular structure and / or function described herein is merely illustrative. Based on this invention, those skilled in the art will understand that one aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number of aspects set forth herein can be used to implement the device and / or practice the method. Additionally, this device and / or method can be implemented using structures and / or functionalities other than one or more of the aspects set forth herein.

[0021] It should also be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. The drawings only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0022] Furthermore, specific details are provided in the following description to facilitate a thorough understanding of the examples. However, those skilled in the art will understand that aspects can be practiced without these specific details. To enable those skilled in the art to better understand the invention, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined as "first" and "second" may explicitly or implicitly include one or more of that feature. In the description of the invention, unless otherwise stated, "a plurality of" means two or more.

[0023] like Figure 1 The dynamic balancing method for the engine flexible rotor system shown is applicable to the dynamic balancing of the low-pressure rotor or power turbine rotor of a turbofan engine when using a flexible rotor. The turbofan engine includes a compressor blade disk and a hollow connecting long shaft. The blade disk includes a compressor disk, a fan disk, and a turbine disk. The connecting long shaft can be simply referred to as a "shaft," and the blade disk can be simply referred to as a "disk." The dynamic balancing method includes...

[0024] S1: Manufacturing process inspection to ensure the fit of the connecting long shaft and blade disk after assembly at the factory. This aims to control key geometric parameter errors from the source, reduce the fundamental causes of initial imbalance, and provide a qualified component foundation for subsequent dynamic balancing operations. Specifically...

[0025] The S11 connecting shaft undergoes tolerance inspection at the factory to ensure the uniformity of wall thickness at different cross-sections of the shaft. This is to prevent the disc and shaft end faces from not fitting tightly during subsequent assembly, which could result in assembly gaps or misalignment and introduce additional imbalance.

[0026] S12: The axial mating surfaces of the journal connecting the long shaft and the blade disk are tested for axial runout during the factory through an end face runout process to ensure the fit of the assembly. The runout value is determined according to the product model and engine specifications. The purpose is to ensure that the disk body is accurately positioned during the assembly process and to avoid the disk body assembly position shift due to positioning surface errors, which would disrupt the symmetry of the overall mass distribution of the rotor.

[0027] S2: The connecting long shaft and blade disk undergo dynamic balancing tests to eliminate vibrations caused by imbalance. The qualified connecting long shaft and blade disk are marked with the first identification mark. Specifically...

[0028] S21: The symmetry error of the "remaining mass moment" of the connecting long shaft and blade disk in the dynamic balancing test is controlled to a preset value by adjusting the counterweight. This ensures that the remaining mass moment of the connecting long shaft and blade disk is symmetrical in circumferential distribution, avoiding periodic vibration fluctuations when the components rotate due to uneven mass moment distribution. The preset value is determined according to the engine specifications, such as the ISO G0.4 standard.

[0029] S22: During the dynamic balancing test, the phase deviation of the remaining mass moment of the connecting long shaft and the blade disk is controlled within the standard deviation range. The standard deviation range is determined according to the engine specifications, such as the ISO G0.4 standard, to ensure that the balance phase of the connecting long shaft and the blade disk can be accurately matched during subsequent assembly. The purpose is to ensure that the remaining mass moment of the disk and shaft is symmetrical in circumferential distribution by adjusting the counterweight, so as to avoid periodic vibration fluctuations when the components rotate due to uneven mass moment distribution.

[0030] S23: Control the phase difference of the unbalance at the end face of the connecting long shaft and blade disk in the dynamic balancing test within the standard phase difference range. The standard phase difference range is determined according to the engine specifications, such as the ISO G0.4 standard. The purpose is to avoid the accumulation of multi-plane unbalance at a specific phase, which would lead to an increase in the local vibration amplitude of the component.

[0031] S3: The connecting shaft and blade disk, marked with the first identifier, are assembled and tested on the bench of the dynamic balancing test device according to design requirements. During assembly, any new imbalance is eliminated simultaneously to avoid the cumulative imbalance after assembling multiple components. After the assembly test is passed, the second identifier is applied. Specifically...

[0032] S31: Detect the axial positioning error between the connecting long shaft and the test bench within the preset accuracy range. The preset accuracy range is determined according to the engine specifications, for example, according to the ISO G0.4 standard. Use a special positioning tool to ensure that the axial installation position of each component meets the design requirements and avoid uneven axial distribution of the rotor's center of gravity due to axial offset.

[0033] S32: Detects that the clearance between the splined teeth of the fan disc and the connecting long shaft is within a preset range. The preset range is determined according to the engine specifications, for example, according to the ISO G0.4 standard. The purpose is to prevent the relative displacement of components due to excessive clearance during rotor rotation, which would disrupt their balance.

[0034] S33: Detects the overall center of gravity offset of the rotor blade disk after assembly onto the connecting long shaft, ensuring it remains within a preset offset range. This guarantees that the overall center of gravity remains aligned with the rotation axis of the connecting long shaft after assembly. The preset offset range is determined according to engine specifications. Real-time monitoring tools monitor the rotor's overall center of gravity position during assembly, ensuring it remains aligned with the rotation axis. This prevents additional unbalanced forces introduced by center of gravity offset and avoids the failure of the initial balance state due to adjustments to assembled components, simplifying the balancing process and reducing time consumption.

[0035] S34: The connecting long shaft is assembled with the compressor disk and / or fan disk and / or turbine disk using an interference fit method. The turbine disk is assembled with the compressor disk and / or fan disk using an interference fit method. The interference fit is within the preset interference fit range, which is determined according to the engine specifications to prevent parts from loosening and to ensure the design requirements of coaxiality.

[0036] S4: The connecting long shaft and blade disk with the second identifier are removed from the test bench and placed on the platform of the rotor dynamics experimental apparatus for dynamic testing. The dynamic indicators are checked to ensure they meet the standards. Modal feature identification verifies that after complete assembly, the rotor-bearing system's dynamic characteristics and equilibrium state under constrained modes ensure no dynamic risks and prevent rotor flexibility deformation from exceeding low-speed balance compensation capabilities. Specifically...

[0037] S41: Check whether the amplification factor (AF) of the connecting long shaft and blade disk as a whole in the resonant frequency band is greater than the design threshold. If yes, mark it as unqualified and return to step S2 or step S3 to adjust the parameters and start again until qualified. If no, mark it as qualified. The design threshold is determined according to the engine model and is used to prevent vibration damage to the connecting long shaft and blade disk. The purpose is to prevent the vibration amplitude from exceeding the design threshold when resonating due to excessively high AF value, thereby causing component damage.

[0038] S42: Check whether the difference between the critical speed of the connecting long shaft and the blade disk as a whole and the rotor operating speed is greater than ±20% of the operating speed. If yes, mark it as qualified; if no, mark it as unqualified and return to step S2 or S3 to adjust the parameters until it is greater than ±20% of the operating speed. The purpose is to clarify the percentage difference between the actual operating speed and the critical speed of the rotor and ensure that the operating speed and the critical speed are kept at a safe interval.

[0039] S43: Check whether the actual strain energy of the connecting long shaft and blade disk as a whole at the critical speed is less than the strain energy corresponding to the shaft's low-speed balance compensation capability. If yes, mark it as qualified; if no, mark it as unqualified and return to step S2 or S3 to adjust the parameters until it is less than the strain energy corresponding to the shaft's low-speed balance compensation capability. The purpose is: if the strain energy is too high, it indicates that the rotor's flexible deformation exceeds the compensation capability of the previous low-speed balance, and the assembly accuracy and balance parameters need to be adjusted retrospectively. At the same time, the phase state of the remaining unbalance of the rotor after assembly is detected to ensure that it is randomly distributed, so as to avoid the superposition of the remaining unbalance of multiple components in a specific phase, which would damage the dynamic balance effect.

[0040] S5: The assembled unit, including the connecting long shaft and blade disk, undergoes full-range speed vibration testing on the rotor dynamics experimental platform to confirm its vibration stability under actual operating conditions. Simultaneously, it ensures the rotor system meets requirements. Specifically, the vibration response of the connecting long shaft and blade disk assembly across multiple speed ranges defined in the engine specifications is tested to ensure it meets the standard vibration response. If yes, it is marked as qualified; otherwise, it is marked as unqualified, and the process returns to step S3 to adjust parameters until the standard vibration response is met. For example, during monitoring, the speed range is set to 103% of the rotor's maximum speed, covering the speed range under normal operation and extreme conditions, comprehensively capturing vibration responses at different speed stages. Vibration indicators must be strictly constrained according to the vibration requirements for different power levels in the ISO 10816 standard. Specific threshold values ​​for vibration amplitude and other indicators are determined based on the differences in unit power to ensure that the monitoring results comply with industry-standard safe operation.

[0041] Furthermore, if monitoring reveals that the vibration data does not meet the requirements of the ISO 10816 standard, it is necessary to return to previous steps, such as assembly process, checking axial positioning accuracy, spline fit clearance, shaft alignment, etc., adjust parameters and retest until the vibration index fully meets the ISO 10816 standard and design requirements.

[0042] S6: Repeatability verification of assembly parameters and dynamic balance. This involves disassembling the connecting long shaft and blade disk, and re-inspecting according to steps S2 to S5. If the inspection results of each step meet the standards, it is marked as finally qualified. If the inspection result of any step S2 to S5 fails to meet the standards, return to step S2 to adjust the parameters and re-inspect until the inspection results of each step meet the standards. Specifically...

[0043] S61: If the axial positioning error between the connecting long shaft and the frame is within the preset accuracy range, record the axial positioning error data between the connecting long shaft and the frame. If the axial positioning error between the connecting long shaft and the frame is not within the preset accuracy range, adjust the assembly process of the positioning error until the axial positioning error after repeated assembly is within the preset accuracy range, and archive the assembly process parameters. The assembly process includes stacked assembly process, detachable connection assembly process and movable connection assembly process, etc. The purpose is to avoid uneven axial distribution of the rotor's centroid due to axial offset.

[0044] S62: If the clearance between the spline sleeve teeth of the fan disc and the connecting long shaft is within the preset range, record the clearance data between the spline sleeve teeth of the fan disc and the connecting long shaft. If the clearance between the spline sleeve teeth of the fan disc and the connecting long shaft is not within the preset range, return to step S2 to adjust the parameters and re-test until the clearance is within the preset range. This is to prevent the relative displacement of components due to excessive clearance during rotor rotation, which would disrupt their balance. The purpose is to strictly control the clearance between the spline and sleeve teeth connecting components to prevent the relative displacement of components due to excessive clearance during rotor rotation, which would disrupt their balance.

[0045] S63: If the overall center of mass offset of the blade disk after being assembled on the connecting long shaft is within the preset offset range and can be kept consistent with the rotation axis of the connecting long shaft, record the position of the blade disk assembled on the connecting long shaft; if the overall center of mass offset of the blade disk after being assembled on the connecting long shaft is not within the preset offset range, return to step S2 to adjust the parameters and re-detect until the center of mass offset is within the preset offset range, and record it. The purpose is to avoid introducing additional unbalanced forces due to center of mass offset and to avoid the failure of the previous balance state due to adjustment of the assembled parts, simplify the balancing process and reduce time consumption.

[0046] This article uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the core ideas of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made to the invention without departing from the principles of the invention, and these improvements and modifications also fall within the protection scope of the invention claims.

Claims

1. A dynamic balancing method for a flexible rotor system of an engine across unit cells, applicable to the dynamic balancing of the low-pressure rotor or power turbine rotor of a turbofan engine using a flexible rotor, wherein the turbofan engine includes a compressor blade disk and a hollow connecting long shaft, the blade disk including a compressor disk, a fan disk, and a turbine disk, characterized in that, The dynamic balancing method includes, S1: Manufacturing process inspection to ensure the fit of the connecting long shaft and blade disk after assembly at the factory. Specifically, the connecting long shaft is inspected at the factory through a tolerance inspection process to ensure the uniformity of wall thickness at different cross-sections of the shaft body; the axial mating surfaces of the journal of the connecting long shaft and the blade disk are inspected at the factory through an end face runout process to ensure the fit of the assembly. S2: The connecting long shaft and blade disk undergo dynamic balancing tests to eliminate vibrations caused by imbalance. The qualified connecting long shaft and blade disk are marked with a first identification mark. The symmetry error of the remaining mass moment of the connecting long shaft and blade disk in the dynamic balancing test is controlled to a preset value by adjusting the counterweight, so that the remaining mass moment of the connecting long shaft and blade disk is symmetrical in circumferential distribution. The preset value is determined according to the engine specification. During the dynamic balancing test, the phase deviation of the remaining mass moment of the connecting long shaft and the blade disk was controlled within the standard deviation range. The standard deviation range was determined according to the engine specifications to ensure that the balance phase of the connecting long shaft and the blade disk could be accurately matched during subsequent assembly. During the dynamic balancing test, the phase difference of the unbalance at the end faces of the connecting long shaft and blade disk is controlled within the standard phase difference range, which is determined according to the engine specifications. S3: The connecting shaft and blade disk with the first mark are assembled on the bench of the dynamic balancing test device according to the design requirements for assembly and testing to eliminate the new imbalance. After the assembly and testing are qualified, the second mark is marked. S4: The connecting long shaft and blade disk with the second mark are removed from the stand and placed on the platform of the rotor dynamics tester for dynamic testing to check whether the dynamic indicators meet the standards. S5: The entire connection shaft and blade disk are subjected to full-range speed vibration testing on the platform of the rotor dynamics tester. Specifically, the vibration response of the entire connection shaft and blade disk in multiple speed ranges defined by the engine specifications is tested to see if they meet the standard vibration response. If yes, it is marked as qualified; otherwise, it is marked as unqualified, and the process returns to step S3 to adjust the parameters until the standard vibration response is met. S6: Repeatability verification of assembly parameters and dynamic balance. The connecting long shaft and blade disk are disassembled and re-inspected according to steps S2 to S5. If the inspection results of each step meet the standards, it is marked as finally qualified. If the inspection results of any step S2 to S5 do not meet the standards, return to step S2 to adjust the parameters and re-inspect until the inspection results of each step meet the standards.

2. The dynamic balancing method according to claim 1, characterized in that, The connecting shaft and blade disk marked with the first identifier in S3 are assembled and tested on the bench of the dynamic balancing test device according to design requirements. The axial positioning error between the connecting long shaft and the test bench is checked and found to be within the preset accuracy range, which is determined according to the engine specifications. The clearance between the splined teeth of the fan disc and the connecting long shaft is checked and found to be within a preset range, which is determined according to the engine specifications. The overall center of gravity offset of the blade disk after assembly with the connecting long shaft is within the preset offset range, so that the center of gravity of the assembly is always consistent with the rotation axis of the connecting long shaft. The preset offset range is determined according to the engine specifications. The long shaft is connected to the compressor disc and / or fan disc and / or turbine disc by an interference fit. The turbine disc is connected to the compressor disc and / or fan disc by an interference fit. The interference fit is within a preset interference fit range, which is determined according to the engine specifications.

3. The dynamic balancing method according to claim 2, characterized in that, The dynamic experiments conducted on the platform of the rotor dynamics experimental apparatus in S4 include, The system detects whether the amplification factor of the connecting long shaft and blade disk as a whole in the resonant frequency band is greater than the design threshold. If so, it is marked as unqualified and returns to step S2 or step S3 to adjust the parameters until it is qualified. If not, it is marked as qualified. The design threshold is determined according to the engine model and is used to prevent vibration damage to the connecting long shaft and blade disk. Check whether the difference between the critical speed of the connecting long shaft and the blade disk as a whole and the rotor operating speed is greater than ±20% of the operating speed. If yes, mark it as qualified; if no, mark it as unqualified and return to step S2 or S3 to adjust the parameters until it is greater than ±20% of the operating speed. Check whether the actual strain energy of the connecting long shaft and the blade disk as a whole at the critical speed is less than the strain energy corresponding to the shaft's low-speed balance compensation capability. If yes, mark it as qualified; if no, mark it as unqualified, and return to step S2 or S3 to adjust the parameters until it is less than the strain energy corresponding to the shaft's low-speed balance compensation capability.

4. The dynamic balancing method according to claim 3, characterized in that, The repeatability verification of assembly parameters and dynamic balance in S6 includes, If the axial positioning error between the connecting long shaft and the stand is within the preset accuracy range, record the axial positioning error data between the connecting long shaft and the stand; if the axial positioning error between the connecting long shaft and the stand is not within the preset accuracy range, adjust the assembly process of the positioning error until the axial positioning error after repeated assembly is within the preset accuracy range, and archive the assembly process parameters. The assembly process includes stacked assembly process, detachable connection assembly process and movable connection assembly process. If the clearance between the splined teeth of the fan disc and the connecting long shaft is within the preset range, record the clearance data between the splined teeth of the fan disc and the connecting long shaft. If the clearance between the splined teeth of the fan disc and the connecting long shaft is not within the preset range, return to step S2 to adjust the parameters and retest until the clearance is within the preset range. If the overall centroid offset of the blade disk after being assembled on the connecting long shaft is within the preset offset range and can be kept consistent with the rotation axis of the connecting long shaft, record the position of the blade disk assembled on the connecting long shaft; if the overall centroid offset of the blade disk after being assembled on the connecting long shaft is not within the preset offset range, return to step S2 to adjust the parameters and re-detect until the centroid offset is within the preset offset range, and record it.

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