Double-rotor pipeline vibration margin evaluation method and system and medium

Abstract

The invention relates to a double-rotor pipeline vibration margin evaluation method and system and a medium. The evaluation method comprises the steps that S1, the inherent frequency of a pipeline is obtained; s2, uncertainty parameters of pipeline evaluation are determined, and according to the uncertainty parameters, vibration frequency probability box distribution under the mixed uncertainty condition considering random uncertainty and cognitive uncertainty is obtained; and S3, based on probability box distribution, the uncertainty and allowance of the pipeline vibration frequency are quantified through the QMU technology, and confidence factors of the high-pressure and low-pressure double rotors under the two dangerous frequency working conditions are obtained.

Description

Technical Field

[0001] The present invention belongs to the field of engines, and in particular relates to a pipeline vibration margin assessment method, system and computer-readable medium for dual-rotors of an aero-engine. Background Art

[0002] The aircraft engine piping system realizes the connection of the aircraft engine's power unit, valve control unit, and actuator, and is an important part of the engine to ensure the transmission of fuel, lubricating oil, and bleed air. During the service of aircraft engines, the "leakage" caused by the vibration failure of the piping system directly restricts the reliability and safety of aircraft engines. Therefore, during the design process, the high-amplitude resonance caused by the coupling of the natural frequency of the piping system and the engine rotor speed should be avoided.

[0003] At present, in the design process of aircraft engine piping systems, the finite element analysis method is usually used to analyze the natural frequency of the pipeline. Its material properties and geometric parameters usually refer to the design values ​​and engineering standards, and fixed values ​​are selected for simulation. The natural frequency is calculated based on a deterministic model, and it is required that the natural frequency should avoid a margin of 20% or even 25% of the rotor speed. For pipelines that do not meet the requirements, adjustments or additional brackets are required for frequency modulation. However, in the actual service process, the processing and manufacturing process, service environment, assembly errors, etc. may bring uncertainty to the material properties, geometric dimensions, and boundary conditions of the pipeline, which directly leads to changes in the natural frequency of the pipeline. Failure to fully consider uncertainty in the design process and using a unified design margin for all pipelines may cause the following two problems:

[0004] 1. Pipeline failure caused by insufficient margin;

[0005] 2. Excessive margin leads to overly conservative pipeline design, increasing costs in manufacturing, weight and other aspects.

[0006] QMU (quantification of margins and uncertainties) is a new method proposed by the National Nuclear Security Administration under the U.S. Department of Energy in 2001 in conjunction with the three major national laboratories of Los Alamos, Lawrence Livermore and Sandia (Pilch M, Trucano TG, Helton J C. Ideas underlying quantification of margins and uncertainties (QMU): a white paper [J]. Unlimited Release SAND2006-5001, Sandia National Laboratory, Albuquerque, New Mexico, 2006, 87185: 2.). The QMU method was first used to evaluate the reliability and safety of stockpiled nuclear weapons when experimental data was insufficient. This method is based on the fault physics model and margin design. It is believed that in order for the system to maintain normal operation and a certain reliability, it is necessary to reserve sufficient design margins for the system for known potential failure modes. However, when calculating the margin M, it is usually affected by a variety of uncertain factors. Once the combined value of these uncertainties is greater than the margin M, the product may fail. The QMU method uses the confidence factor CR as the calibration criterion, that is, the ratio of the performance margin M to the uncertainty U to characterize the relationship between the performance margin and the uncertainty. When CR>1, it means that the system is safe in the QMU method.

[0007] Therefore, this field needs a QMU-based vibration margin assessment method for aircraft engine piping systems, which can perform a safety assessment of the resonance margin under mixed uncertainty conditions of the piping system as a theoretical basis for optimizing the margin boundary. Summary of the invention

[0008] An object of the present invention is to provide a method for evaluating the pipeline vibration margin of a dual-rotor.

[0009] An object of the present invention is to provide a piping vibration margin evaluation system for a dual-rotor.

[0010] An object of the present invention is to provide a computer readable medium.

[0011] A pipeline vibration margin assessment method according to one aspect of the present invention comprises:

[0012] S1. Obtain the natural frequency of the pipeline;

[0013] S2. Determine the uncertainty parameter of pipeline evaluation, and obtain the probability box distribution of vibration frequency under mixed uncertainty conditions considering random uncertainty and epistemic uncertainty according to the uncertainty parameter;

[0014] S3. Based on the probability box distribution, the uncertainty and margin of the pipeline vibration frequency are quantified by QMU technology, and the confidence factor of the high- and low-pressure dual rotors under two dangerous frequency conditions is obtained.

[0015] According to another aspect of the present invention, an aircraft engine piping vibration margin assessment system includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the above assessment method when executing the computer program.

[0016] According to another aspect of the present invention, a computer readable medium has a computer program thereon, and the program is executed by a processor to implement the steps in the above-mentioned evaluation method that can be implemented by the computer program.

[0017] In summary, the evaluation method, evaluation system, and computer-readable medium described in the above embodiments are aimed at the disadvantages that in the design process of existing aircraft engine pipelines, a unified margin boundary is used for all pipelines, which is not conducive to weight reduction or cost reduction, and at the same time cannot completely avoid the risk of failure. The QMU evaluation method is introduced to consider various mixed uncertainties, and its beneficial effects include but are not limited to:

[0018] 1. The probability box method is used to describe the results of the mixed effects of random uncertainty and cognitive uncertainty, and a concise and intuitive frequency distribution quantification is given to facilitate designers to judge uncertainty;

[0019] 2. The confidence factors of the high-pressure and low-pressure dual rotors under two dangerous frequency conditions are considered simultaneously to provide a reference for margin evaluation under multiple boundaries.

[0020] 3. The QMU method is introduced for vibration margin assessment, providing valuable guidance and reference for the setting of vibration margin of aircraft engine pipelines. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The above and other features, properties and advantages of the present invention will become more apparent through the following description in conjunction with the accompanying drawings and embodiments. It should be noted that the drawings are only examples and are not drawn to scale, and should not be used as a limitation on the actual scope of protection required by the present invention, wherein:

[0022] Figure 1 It is the finite element model of the pipeline.

[0023] Figure 2 It is the probability box distribution of pipeline vibration frequency under mixed uncertainty.

[0024] Figure 3 It is a pipeline resonance QMU considering mixed uncertainty.

[0025] Figure 4 It is a flow chart of a dual-rotor pipeline vibration margin assessment method according to an embodiment. DETAILED DESCRIPTION

[0026] The following discloses various different implementation methods or embodiments of the subject technical solution. To simplify the disclosure, specific examples of various elements and arrangements are described below. Of course, these are only examples and are not intended to limit the scope of protection of the present invention.

[0027] At the same time, the present application uses specific words to describe the embodiments of the present application. For example, "one embodiment", "an embodiment", and / or "some embodiments" refer to a certain feature, structure or characteristic related to at least one embodiment of the present application. Therefore, it should be emphasized and noted that "one embodiment" or "an embodiment" or "an alternative embodiment" mentioned twice or more in different positions in this specification does not necessarily refer to the same embodiment. In addition, some features, structures or characteristics in one or more embodiments of the present application can be appropriately combined.

[0028] It is understood that flow charts are used in the present application to illustrate the operations performed by the system according to the embodiments of the present application. It should be understood that, according to the actual situation, the previous or following operations are not necessarily performed precisely in order. Other operations may also be added to these processes, or one or more operations may be removed from these processes.

[0029] The design of existing aircraft engine piping systems generally uses a unified design margin for all pipelines. The inventors have found that this is not conducive to weight reduction or cost reduction, and also cannot completely avoid the disadvantage of failure risk.

[0030] Therefore, the inventor invented a QMU-based twin-rotor aircraft engine piping vibration margin assessment method to overcome the shortcomings of the prior art.

[0031] refer to Figure 4 As shown, in some embodiments, a dual-rotor piping vibration margin assessment method may include:

[0032] S1. Obtain the natural frequency of the pipeline.

[0033] Specifically, it may include: establishing a pipeline finite element analysis model, and obtaining the natural frequency of the pipeline according to the material properties, pipe wall thickness and boundary conditions. For example, using hypermesh to establish a pipeline finite element analysis model, and inputting the necessary conditions such as material properties, pipe wall thickness and boundary to set up the natural frequency solution.

[0034] S2. Determine the uncertainty parameter of pipeline evaluation, and based on the uncertainty parameter, obtain the probability box distribution of vibration frequency under mixed uncertainty conditions considering random uncertainty and epistemic uncertainty.

[0035] Specifically, the density, elastic modulus, and Poisson's ratio of the pipeline can be regarded as random variables that obey the normal distribution, and the pipeline wall thickness and the moment of the pipeline installation boundary can be regarded as interval-distributed variables. Sample points are extracted by the Monte Carlo sampling method, and the natural frequencies of the sample points are calculated to obtain the probability box distribution of vibration frequency under mixed uncertainty conditions based on random uncertainty and epistemic uncertainty. That is, the uncertainty parameters to be considered in the pipeline system are determined: density, elastic modulus, and Poisson's ratio are usually random uncertainties, which can be considered as random variables that obey the normal distribution, and the pipeline wall thickness and the moment of the pipeline installation boundary are usually epistemic uncertainties, which can be considered as interval-distributed variables. Then, sample points are extracted by the Monte Carlo sampling method, and the natural frequencies of the sample points are calculated to obtain the probability box distribution of vibration frequency under mixed uncertainty conditions considering random uncertainty and epistemic uncertainty.

[0036] S3. Based on the probability box distribution, the uncertainty and margin of the pipeline vibration frequency are quantified by QMU technology, and the confidence factor of the high- and low-pressure dual rotors under two dangerous frequency conditions is obtained.

[0037] Specifically, based on the probability box distribution, the uncertainty and margin of the pipeline vibration frequency are quantified by QMU technology, and the confidence factor CR is obtained. The specific method as the basis for resonance safety assessment is as follows:

[0038] (1) Quantification of uncertainty:

[0039] The mixed uncertainty of the pipeline vibration frequency is represented by a probability box. For a twin-rotor engine with high and low pressure rotor speeds, the uncertainty is:

[0040]

[0041]

[0042] Among them, U 1 Quantify the uncertainty of the pipeline for the low-pressure rotor margin, U 2 Quantify the uncertainty of the pipeline for the high pressure rotor margin. maxrepresents the right boundary of the pipeline vibration frequency probability box distribution, f min It represents the left boundary of the probability box distribution of pipeline vibration frequency, p represents the probability, and β represents a certain confidence level, which is generally 0.95.

[0043] (2) Quantification of margin: For a twin-rotor aircraft engine with high and low pressure rotor speeds, the margin is the safe distance between the probability box distribution of the pipeline resonance frequency and the high and low pressure rotor frequencies. The calculation equation is:

[0044] M 1 =(f mim ) p＝0.5 -f N1

[0045] M 2 =f N2 -f max ) p＝0.5

[0046] (3) Solving the confidence factor is used to determine the flutter margin safety. The confidence factor calculation equation is:

[0047]

[0048] In QMU technology, when CR is greater than 1, the system is considered safe, and the designed piping system has sufficient margin to cover the uncertainty, which can be used as a criterion for piping resonance safety assessment.

[0049] The vibration margin evaluation method of the present application is further illustrated below through specific data. The method may include the following steps.

[0050] Step 1: Use finite element modeling software hypermesh to create a pipeline simulation model. Figure 1 As shown, the pipeline material parameters, pipeline outer diameter, inner diameter, and installation torque are shown in Table 1. The natural frequency under deterministic parameters is calculated.

[0051] Table 1 Finite element model parameters

[0052]

[0053] Step 2: Set the uncertainty parameters as shown in Table 2.

[0054] Table 2 SPCD card definition

[0055] parameter distributed Uncertainty Type Elastic modulus E Normal random Material density D Normal random Poisson's ratio Normal random Pipe outer diameter Interval Cognition Pipe inner diameter Interval Cognition Installation torque Interval Cognition

[0056] Step 3: Use Monte Carlo nested loop 500×1000 sampling, with 500 samplings for epistemic uncertainty in the outer layer and 1000 samplings for random uncertainty in the inner layer. Finally, the cumulative distribution function of the natural frequency of the pipeline can be obtained, which consists of Figure 2 Probability box distribution of natural frequencies.

[0057] Step 4: Set the boundaries of the engine high and low pressure rotor speeds on the probability box distribution, such as Figure 3 shown.

[0058] And follow

[0059]

[0060]

[0061] To calculate the uncertainty,

[0062] according to

[0063] M 1 =(f mim ) p＝0.5 -f N1

[0064] M 2 =f N2 -(f max ) p＝0.5

[0065] Calculate the margin;

[0066] according to

[0067]

[0068] The confidence factor CR is calculated.

[0069] When CR>1, it is considered that the current vibration margin can guarantee the uncertainty under the current uncertainty level, and a safety criterion is given.

[0070] It can be understood that the above embodiments can also be implemented in a system, that is, the present application also provides a dual-rotor aircraft engine pipeline vibration margin assessment system, including a memory for storing instructions executable by a processor; a processor for executing the instructions to implement the assessment method as described in the above embodiments.

[0071] It should be noted that the above-mentioned memory, processor, and database are not limited to a specific memory, processor, or database. For example, in some cases, both the memory and the processor can have a distributed structure. For example, they can include a memory and a processor located on the test device side and the backend cloud, respectively, and the test device side and the backend cloud jointly implement the above-mentioned evaluation method. Furthermore, in an embodiment adopting a distributed structure, each step can adjust the specific execution terminal according to actual conditions, and the specific scheme of each step implemented in a specific terminal should not limit the scope of protection of the present invention.

[0072] Another aspect of the present application further provides a computer-readable storage medium storing a computer program. When the computer program is executed by a processor, the steps of the evaluation method described in the above embodiment are implemented. Please refer to the above description for details, which will not be repeated here.

[0073] In addition, it can be understood that the above-mentioned computer-readable storage medium can also be in a system form, that is, it includes multiple computer-readable storage sub-media, so as to jointly implement the steps of the evaluation method described above through multiple computer-readable storage media.

[0074] In summary, the evaluation method, evaluation system, and computer-readable medium described in the above embodiments are aimed at the disadvantages that in the design process of existing aircraft engine pipelines, a unified margin boundary is used for all pipelines, which is not conducive to weight reduction or cost reduction, and at the same time cannot completely avoid the risk of failure. The QMU evaluation method is introduced to consider various mixed uncertainties, and its beneficial effects include but are not limited to:

[0075] 1. The probability box method is used to describe the results of the mixed effects of random uncertainty and cognitive uncertainty, and a concise and intuitive frequency distribution quantification is given to facilitate designers to judge uncertainty;

[0076] 2. The confidence factors of the high-pressure and low-pressure dual rotors under two dangerous frequency conditions are considered simultaneously to provide a reference for margin evaluation under multiple boundaries.

[0077] 3. The QMU method is introduced for vibration margin assessment, providing valuable guidance and reference for the setting of vibration margin of aircraft engine pipelines.

[0078] The various illustrative logic modules and circuits described in conjunction with the embodiments disclosed herein may be implemented or executed with a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. The processor may also be implemented as a combination of computing devices, such as a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in cooperation with a DSP core, or any other such configuration.

[0079] The steps of the method or algorithm described in conjunction with the embodiments disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. The software module may reside in a RAM memory, a flash memory, a ROM memory, an EPROM memory, an EEPROM memory, a register, a hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. An exemplary storage medium is coupled to a processor so that the processor can read and write information from / to the storage medium. In an alternative, a storage medium may be integrated into a processor. The processor and the storage medium may reside in an ASIC. The ASIC may reside in a user terminal. In an alternative, the processor and the storage medium may reside in a user terminal as discrete components.

[0080] In one or more exemplary embodiments, the functions described may be implemented in hardware, software, firmware, or any combination thereof. If implemented as a computer program product in software, each function may be stored on or transmitted by a computer-readable medium as one or more instructions or codes. Computer-readable media include both computer storage media and communication media, including any media that facilitates the transfer of a computer program from one place to another. Storage media may be any available media that can be accessed by a computer. As an example and not limitation, such a computer-readable medium may include RAM, ROM, EEPROM, CD-ROM or other optical disk storage, disk storage or other magnetic storage device, or any other medium that can be used to carry or store the desired program code in the form of an instruction or data structure and can be accessed by a computer. Any connection is also properly referred to as a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwaves, the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwaves are included in the definition of the medium. Disk and disc as used herein include compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk and Blu-ray disc, wherein disk often reproduces data magnetically, while disc reproduces data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media.

[0081] Although the present invention is disclosed as above in terms of preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications without departing from the spirit and scope of the present invention. Therefore, any modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the scope of protection defined by the claims of the present invention.

Claims

1. A dual-rotor pipeline vibration margin assessment method, It is characterized in that include: S1. Obtain the natural frequency of the pipeline; S2. Determine the uncertainty parameter of pipeline evaluation, and obtain the probability box distribution of vibration frequency under mixed uncertainty conditions considering random uncertainty and epistemic uncertainty according to the uncertainty parameter; S3. Based on the probability box distribution, the uncertainty and margin of the pipeline vibration frequency are quantified by QMU technology, and the confidence factor of the high- and low-pressure dual rotors under two dangerous frequency conditions is obtained.

2. The vibration margin evaluation method according to claim 1, It is characterized in that The step S3 includes: representing the mixed uncertainty of the pipeline vibration frequency by a probability box, and for a dual-rotor engine with high and low pressure rotor speeds, the uncertainty is: Among them, U 1 Quantify the uncertainty of the pipeline for the low-pressure rotor margin, U 2 Quantify the uncertainty of the pipeline for the high pressure rotor margin; f max represents the right boundary of the pipeline vibration frequency probability box distribution, f min It represents the left boundary of the probability box distribution of pipeline vibration frequency, p represents the probability, and β represents a certain confidence level, which is generally 0.

95.

3. The vibration margin evaluation method according to claim 2, It is characterized in that The step of S3 further includes: For a twin-rotor aircraft engine with high and low pressure rotor speeds, the margin is the safe distance between the probability box distribution of the pipeline resonance frequency and the high and low pressure rotor frequency, and its calculation equation is: M 1 =(f min ) p＝0.5 -f N1 M 2 =f N2 -(f max ) p＝0.5 。 4. The vibration margin evaluation method according to claim 3, It is characterized in that The step of S3 further includes: Solving the confidence factor is used to determine the safety of the vibration margin. The calculation equation of the confidence factor is: In QMU technology, when CR is greater than 1, the system is considered safe, and the designed piping system has sufficient margin to cover the uncertainty.

5. The vibration margin evaluation method according to claim 1, It is characterized in that In S2, the density, elastic modulus and Poisson's ratio of the pipeline are regarded as random variables obeying normal distribution, and the pipeline wall thickness and the moment of the pipeline installation boundary are regarded as variables with interval distribution.

6. The vibration margin evaluation method according to claim 1, It is characterized in that In S2, sample points are extracted by Monte Carlo sampling method, and the natural frequencies of the sample points are calculated to obtain the probability box distribution of vibration frequency under mixed uncertainty conditions based on random uncertainty and cognitive uncertainty.

7. The vibration margin evaluation method according to claim 1, It is characterized in that The step S1 includes: establishing a pipeline finite element analysis model, and obtaining the natural frequency of the pipeline according to the material properties, pipe wall thickness and boundary conditions.

8. A dual-rotor pipeline vibration margin assessment system for an aircraft engine. It is characterized in that include: a memory for storing instructions executable by a processor; A processor, configured to execute the instructions to implement the evaluation method according to any one of claims 1 to 7.

9. A computer readable medium having a computer program thereon, It is characterized in that The program is executed by a processor to implement the steps in the evaluation method according to any one of claims 1 to 7 that can be implemented by a computer program.

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