GB2610281A - Method for identifying early frictional instability faults of a spline joint structure - Google Patents
Method for identifying early frictional instability faults of a spline joint structure Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
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- G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- G01M1/00—Testing static or dynamic balance of machines or structures
- G01M1/14—Determining imbalance
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Abstract
The invention provides a method for identifying early friction instability faults of a spline joint structure. The critical rotation speed of a rotor system with a spline joint structure is determined first, wherein the critical rotation speed of the rotor system can be calculated by using a finite element method, and a characteristic frequency band of early frictional instability faults of the spline joint structure is determined. In practice, the first order critical rotation speed of the rotor system can be obtained by experimental methods or commercial software calculation methods. The vibration signals of the rotor system is collected and the rotation speed is collected, it is further determined whether the rotation speed is slightly higher than first order critical rotation speed, the vibration signals in the characteristic frequency band is collected, a characteristic value of the early frictional instability faults of the spline joint structure is calculated, and it is determined according to the characteristic value whether the early frictional instability faults of the spline joint structure occur. The method can effectively avoid the occurrence of major loss caused by instability faults, has simple identification process and small amount of calculation, has millisecond-level response time under a mainstream computing platform, is quick in response. This method may be applied to aero engine fault diagnosis.
Description
Method for Identifying Early Frictional instability Faults of a Spline Joint Structure
Technical Field
The present invention relates to the field of aero engine fault diagnosis, specifically a method for identifying early frictional instability faults of a spline joint structure due to spline surface friction.
Background Art
At present, the rotor system of an aero engine often adopts a two-rotor structure, in which the low-pressure rotor span is relatively long, so the connection is often made by a spline joint structure. The spline joint structure is one of the most common coupling structures in aero engines it is mainly used in the low-pressure rotor of an aero engine to connect a turbine shaft and a fan shaft, so that the two shafts rotate synchronously, while playing a role in transmitting torque and axial force. The structure has the advantages of strong load carrying capacity, high centering accuracy and compact structure, and has the advantages of simple structure, easy installation, and transmission of large torque and axial load. Unlike spline connections used in ground rotating machinery, aero engine rotor systems with spline joint structures generally operate at critical rotation speeds and therefore carry the risk of frictional instability. When slipping occurs at the spline surface of the spline joint structure, the friction force of the spline surface will affect the stability of the rotor system, and once the rotor system is unstable, the result is often very serious. In engineering practice, the vibration problems of the aero engine caused by the instability of the spline joint structure often cause serious consequences. During the commissioning process of a certain type of engine, due to the friction force generated by the friction of the spline surface of the spline joint structure, the cantilever low-pressure turbine rotor in the supercritical working state produces self-excitation, which makes the engine vibrate gre.atiy. When the rotor system enters the instability zone, it is difficult to control the vibration state and it is extremely dangerous, therefore it is necessary to find a way to identify early frictional instability faults of the spline joint structure when the rotor system has not entered a complete instability state, so as to improve the safety and reliability of the aero engine operation.
Most of the current researches focus on the design of the spline joint structure, the strength of the spline and the dynamic characteristics of the rotor with a spline joint structure: CHEN Zhiying el al. in the paper "Robustness Optimization of Dynamic Assembly Parameters for Aero-Engine Spline Structure (CHEN allying, LIU Honglei, ZHOU Ping. Robustness Optimization of Dynamic Assembly Parameters for Aero-Engine Spline Structure M. JOURNAL OF PROPULSION TECHNOLOGY, 2018,39(O1):160168) studied the motion characteristics and coordination relationship of the aero engine spline joint structure in the case of inclination angle misalignment, and derived the calculation formula of the tooth side gap of the spline joint structure containing inclination angle misalignment and the characteristic value of the spline joint structure related to it, and calculated and analyzed the shaft diameter of the compressor spline joint structure of a certain type of ac-ro engine, and on this basis, considering the randomness of the parameters; the drosophila optimization algorithm was applied to optimize the robustness of the tooth side gap of the spline joint structure. LI Junhui et at in the paper "Dynamic Design Method of Spline Joint Structure for Rotor System" (LI Junhui, MA Yanhong, HONG Jie. Dynamic Design Method of Spline Joint Structure for Rotor System [J]. JOURNAL OF AEROENGINE, 2009,3504): 36-39) used the contact finite element method to establish a computational analysis model of the spline joint structure of the rotor system, and studied the structural parameters such as the spacing of the positioning surface, the tightness of the positioning surface fitting and the contact area, as well as the influence law of the load on the connection stiffness and contact state of the spline joint structure. On this basis; the dynamic design method of the spline joint structure was proposed, including the design method of connection stiffness and the design method of contact state. LIAO Zhongkun et at in the paper "Effects of Gear Coupling on Aero-engine Vibration on Characteristics" (LIAO Zhongkun; CHEN G110, WANG Haifei. Effects of Gear Coupling on Aero-engine Vibration on Characteristics [J]. JOURNAL OF China Mechanical Engineering, 2015, 26(10):1312-1319.) developed the connection stiffness of the aero-engine gear coupling (spline coupling), derived the calculation model of the dynamic engagement force of the spline, analysed the engagement force of the spline and engagement stiffness of the spline which changed with torque, spline misalignment and dynamic relative displacement, and established the three-pivot rotor dynamic model with the spline joint structure according to the sera engine spline joint structure, analysed the influence of the stiffness of the spline joint structure on the frequency response characteristics of the system, and analysed, considering the angle misalignment between the rotation shafts; the influence law of the stiffness of the spline joint structure on the misalignment response of the system. C. P. Roger Ku et at in the paper "Dynamic Coefficients of Axial Spline Couplings in High-Speed Rotating Machinery "(Ku C. P. Roger, Walton J. F, Lund U. W. Dynamic Coefficients of Axial Spline Couplings in High-Speed Rotating Machinery [J]. Journal of Vibration and Acoustics, 1994, 116(3)) showed that the internal friction between the splines is the main cause of the uncoordinated instability of the rotor, with the instability speed above the 1st order critical, but the instability frequency approximately equal to the 1st order frequency.
The invention published as CN110630646A proposed a new type of spline joint structure, wherein the structure was connected with two shafts through the elastic mold coupling and torque transmission spline, to achieve highspeed torque transmission between the two shafts, and the spline joint adopted involute spline shape, so that thwugh the reasonable design of the spline space, the inner and outer spline joints were easy to assemble, and that through the requirements of high spline accuracy and installation accuracy, the spline joints were uniformly stressed and had stable transmission and small vibration. This invention solved the problem of excessive centrifugal force at high rotation speed and heavy working conditions, and too large stress at where the spline coupling was connected, but it is still impossible to completely avoid the instability of the spline joint caused by friction. The invention published as CN204716783U proposed an idea to reduce the easy wear phenomenon of the spline side of the spline; so that the spline device needed to be replaced only when the spline in the spline shaft was worn out, instead of the entire spline shaft needing to be replaced, which improved the life of the spline shaft, and reduced the maintenance cost of the spline shaft. But the invention is to replace the spline only when the spline surface of the spline is worn, which cannot solve the practical problem of monitoring the instability of the spline caused by friction. In the event of an instability failure, these improved spline joint structures cannot guarantee the safe and reliable operation of the aero engine.
WANG Tong in the paper "Stability Analysis of Rotor with Spline Coupling" (WANG Tong, WANG Li, LIAO Mingfu. Stability Analysis of Rotor with Spline Coupling [j]. JOURNAL OF AEROENGINE, 2021,47(03):66-71) introduced the fault mechanism of the instability of the spline joint structure; and explained the rotor vibration response of the rotor with the spline joint structure under the internal damping c; obtained through theoretical derivation that the friction force of the spline surface of the spline joint structure will bring the anti-symmetry cross stiffness to the rotor, this anti--symmetry cross stiffness causing rotor instability, and proposed that the rotor with the spline joint structure will be unstable due to the instability caused by the friction of the spline joint structure, wherein there will be an intermediate state of transition from the stable state to the severe instability state, the intermediate state being called the early frictional instability state, but there is no more in-depth study on how to monitor the early frictional instability state of the rotor with the spline joint structure. As shown in Figure 1, when the rotor is in an early frictional instability state, the spline structure has started to fail, but the vibration amplitude of the rotor does not generate a surge like the severe instability state, which is easily confused with the stable state. If the early frictional instability is not removed in time, as the rotation speed increases, it will develop into serious instability and serious damage to the operation safety of engine. Therefore, monitoring the early frictional instability faults of the rotor with spline joint structure and stopping in time when being in the early frictional instability state can avoid the further development of the engine state into serious instability, which can effectively reduce the damage caused by the instability faults to the engine, check the fault situation in time, perform replacement and repair in time, and further ensure the safe and reliable operation of the equipment. How to identify the early instability fault requires a specific corresponding method and process, but there is no relevant patent research to conduct in-depth analysis of this.
Summary
In order to overcome the deficiency of lacking a simple and effective method to identify the early frictional instability faults of spline joint structures in the prior art, the present invention proposes a method for identifying early frictional instability faults of a spline joint structure of an aero engine.
The specific steps of the method of identifying early frictional instability faults of a spline joint structure proposed by the present invention includes: Step 1: determining the critical rotation speed of the rotor system with a spline joint structure.
Based on the previous researches, it can be seen that the rotation speed when the early instability faults of the spline joint structure occur is above the first order critical rotation speed; and simultaneously, the frequency of the instability vibration is equal to the frequency of the first order critical rotation speed. Therefore, the first order critical rotation speed of the rotor system with the spline joint structure needs to be determined.
There are many methods to determine the critical rotation speed of the rotor with the spline joint structure, for example, the critical rotation speed is determined by experimental methods, calculated by finite element methods or calculated by commercial software. In the present application; the calculation is performed by taking the finite element method as an example.
The process of simplifying the determined rotor system structure with the spline joint structure to a finite element model includes: simplifying a low-pressure shaft to a combination of several low-pressure shaft-beam units, simplifying a high-pressure shaft to a combination of several high-pressure shaft-beam units, simplifying a low-pressure fan to a flexible low-pressure fan disc unit, simplifying a low-pressure turbine to a rigid low-pressure turbine disc unit, simplifying a fan front rolling bearing to a fan front rolling bearing unit, simplifying a low-pressure turbine rear rolling bearing to a low-pressure turbine rear bearing unit, simplifying the high-pressure compressor to a rigid high-pressure compressor disc unit, simplifying a high-pressure turbine to a rigid high-pressure turbine disc unit, simplifying the high-pressure compressor front rolling bearing to a high-pressure compressor front rolling bearing unit, simplifying the intermediate roiling bearing to an intermediate rolling bearing unit, simplifying the spline joint structure to spline joint structure unit, and simplifying a receiver to a massless receiver unit.
The finite element model parameters include: an elastic modulus, a shear modulus, a material density, a high-pressure shaft-beam unit diameter, a low-pressure shaft-beam unit inner diameter, a low-pressure shaft-beam unit outer diameter, damping, flexible low-pressure fan disc unit mass, rigid high-pressure compressor disc unit mass, rigid high-pressure turbine disc unit mass, rigid low-pressure turbine disc unit mass, flexible low-pressure fan disc unit rotational inertia, rigid high-pressure compressor disc unit rotational inertia, rigid high-pressure turbine disc unit rotational inertia, rigid low-pressure turbine disc unit rotational inertia, spline joint structure unit stiffness, spline joint structure unit damping, minimum clearance value, an intermediate rolling bearing unit position, a flexible fan low-pressure disc unit position, a low-pressure turbine disc unit position, a fan front rolling bearing unit position, a low-pressure turbine rear bearing unit position, a high-pressure compressor front rolling bearing unit position, a rigid high-pressure compressor disc unit position, a rigid high-pressure turbine disc unit position, and a spline joint structure unit position.
After determining the above finite element models and each finite element model parameter; the finite element method of rotor dynamics is used to program a finite element calculation program to calculate the model, and the critical rotation speed "ler of the rotor system with the spline joint structure is obtained.
Step 2: determining the characteristic frequency band of the early frictional instability faults of the spline joint structure.
Since when instability occurs, the spline joint structure will undergo certain wear; so that the firs: order critical rotation speed will be reduced compared with a design value, and therefore the defined characteristic frequency band of the early frictional instability faults of the spline joint structure is slightly lower than the first order critical rotation speed licr 5 and the first order critical rotation speed of the rotor after wear is reduced within 5%, so the instability fault characteristics are: [0.95/ii, (1) Step 3: acquiring vibration data of the rotor system with the spline joint structure.
For the determined rotor system with the spline joint structure, the vibration data during acceleration is acquired. The vibration data and rotation speed at every moment is recorded.
Because the instability threshold rotation speed of the rotor system with the spline joint structure is above the first order critical rotation speed, early instability is an early sign of failure and needs to be detected early, if the whole process is measured, the amount of calculation is large; so 0.9 "'if is selected as the indicator, which can reduce the amount of calculation. if the current rotation speed is greater than or equal to 0.9 tirr, the subsequent process steps are carried out, and if the current rotation speed is less than 0.9Plc' the rotation speed is continued to be increased and the vibration data of the rotor system continues to be collected.
Step 4: acquiring the vibration signal in the characteristic frequency band of the early frictional instability faults of the spline joint structure.
After determining that the rotation speed at current moment in step 3 is greater than 0.9, the data obtained in step 3 is collected and recorded, and then the collected data is divided per second, and the vibration signal of the first few cycles (such as 16 cycles) before each second is selected for fast Fourier transform, to obtain the frequency domain components of the vibration signal. Then the signal of the characteristic frequency band of the early frictional instability faults of the spline joint structure is identified and used in the subsequent determination process.
Step 5, calculating the characteristic value of the early frictional instability faults of the spline joint structure.
The characteristic value of the early frictional instability faults of he spline joint structure is defined as r: (2) In the above formula 0 is the rotation speed at the current moment, " " I represents the root mean square value of the amplitudes of all frequency component vibration signals in the characteristic frequency band of the early frictional instability faults of the spline joint structure, and represents the root mean square value of the amplitudes of all frequency component vibration signals in this frequency band 0.95c1,1 05K).
Step 6, determining, according to the characteristic value, whether the early frictional instability faults of the spline joint structure occur.
By summarizing the experimental results of the early frictional instability faults of the spline joint structure, according to the test results and engineering experience, the critical value of the characteristic value of the early frictional instability faults of the spline joint structure defined is recommended as 0.25, and by comparing the characteristic value of the faults calculated in step 5 to 0.25, whether the early frictional instability faults of the spline joint structure occur is determined. If the calculated value sis less than 0.25, no early frictional instability faults of the spline joint structure occur at this time, and it is returned to step 3, at which time the rotation speed can continue to be increased and the vibration data of the rotor system can continue to be s collected, if the calculated value " c is greater than or equal to 0.25, at this time, the early frictional instability faults of the spline joint structure occur, and it is necessary to issue an alarm and stop the rotor system, and check the wear of the spline surface and the positioning surface of the spline joint structure.
At this point, the identification of the early frictional instability faults of the spline joint structure is completed.
Figure 3 shows a schematic diagram of a specific procedure of the present invention.
The present invention can simply and effectively identify the early frictional instability faults of the spline joint structure. The present invention compensates for the absence of the identification of the early frictional instability faults of the spline joint structure in the art, proposes the characteristic energy band of the early frictional instability faults of the spline joint structure, proposes the characteristic value and identification criterion of the early frictional instability faults of the spline joint structure, and proposes the identification process of the early frictional instability faults of the spline joint structure.
The present invention first determines the critical rotation speed of the rotor system with the spline joint structure, wherein the critical rotation speed of the rotor system may be calculated by using the finite element method, and the characteristic frequency band of the early frictional instability faults of the spline joint structure is determined. In practice, the first order critical rotation speed of the rotor system can be obtained by experimental methods or commercial software calculation methods. The vibration signal of the rotor system is collected and the rotation speed is collected, and it is further determined whether the rotation speed is slightly higher than the 'first order critical rotation speed, and the vibration signal in the characteristic frequency band is collected, the characteristic value of the early frictional instability faults of the spline joint structure is calculated; and whether the early frictional instability faults of the spline joint structure occur is determined according to the characteristic value.
Beneficial effects The present invention focuses on the early failure before the occurrence of severe instability failure and issues an early warning, wherein the alarm is set off and the equipment is stopped before the early instability turns into serious instability, which can effectively avoid the occurrence of major losses caused by instability failure. At the same time, the early instability fault identification process proposed by the present invention is simple, the amount of calculation is small, the response time under the current mainstream computing platform is in the millisecond level, the response is rapid; and it can be extended to the airborne equipment; which has high engineering application value.
Additional aspects and advantages of the present invention will partially be given in the following description, and partially become apparent from the following description, or learned through the practice of the present invention.
Brief Description of Drawings
The above and/or additional aspects and advantages of the present invention will become apparent and easy to understand from the description of the embodiments in conjunction with the following drawings, wherein: Figure 1 is a vibration spectrum of early frictional instability faults of a rotor with a spline joint structure; Figure 2 shows the experimental data processing results of the early frictional instability faults of the spline joint structure; Figure 3 is a schematic diagram of a specific procedure of the present invention; and Figure 4 is a schematic diagram of the specific finite element node division of the design experimental device in an embodiment.
Detailed Description of Embodiments
Embodiments of the present invention are described in detail below, examples of said embodiments being shown in the accompanying drawings, wherein the same or similar designations from beginning to end indicate the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention and are not to be understood as limiting the present invention.
The present embodiment is a method for identifying early frictional instability faults of a spline joint structure of a rotor with the spline joint structure of a certain type of aero engine, including the specific process as follows.
Premise: determining the initial structural characteristics of the rotor system with the spline joint structure.
The present embodiment is used for a power turbine shaft of a turboshaft engine. A small single-disc cantilever rotor experimental device with a spline joint structure after a geometrically and dynamically similar design is made. The initial structural characteristics of the rotor system with the spline joint structure that need to be determined mainly refers to its rotor structure parameters, spline joint structure parameters and other parameters.
The rotor structure parameters include the length, radius, density, modulus of elasticity and Poisson's ratio of each shaft segment, and the mass, the axis rotational inertia and the diameter rotational inertia of the cantilever disc, the process of determination of each of which includes that: the length and radius of each shaft segment are determined by the engineering drawings of the small single-disc cantilever rotor experimental device with a spline joint structure, and the density, modulus of elasticity and Poisson's ratio of each shaft segment are determined by consulting the Metal Materials Manual.
In the present embodiment, the initial design parameters of the small single disc cantilever rotor experimental device with a spline joint structure are shown in Table 1. Figure 4 is a schematic diagram of the specific node division of the experimental device of this design, -Fable 1 Shaft segment design parameters for the small single-disc cantilever rotor experimental device with a spline joint structure Shaft parameters 1 Shaft i Length/n m Outer Inner Densit y Modulus of Poisson 's ratio i segmen diameterim m diameterim m kg/m 3 elasticity/ 1 ts i Pa* L1 25 30 18 7850 201*1e9 0.3 L2 10 30 0 7850 201*1 e9 0.3 L3 15 25 0 7850 201'169 0.3 L4 30 22.5 0 7850 201"169 0.3 L5 40 22.5 0 7850 201*169 0.3 L6 15 22.5 0 7850 201+1 e9 0.3 L7 15 20 0 7850 201*1 e9 0.3 L8 15 18.5 0 7850 2011e9 0.3
_
L9 25 10 0 7850 201*169 0.3 L10 25 10 0 7850 201*1e9 0.3 Ll 1 25 10 0 7850 201*169 0.3 L12 25 10 0 7850 201"'l e9 0.3 L13 25 10 0 7850 201*1e9 0.3 L14 25 10 0 7850 201*1e9 0.3 L15 25 10 0 7850 201*1 e9 0.3 L16 25 10 0 7850 201*1 e9 0.3 L17 25 10 0 7850 201*1e9 0.3 L18 25 10 0 7850 2011e9 0.3 L19 25 10 0 7850 201*1 e9 0.3 n r 10 0 7850 201*1e9 0.3 4.c., 1 121 25 10 0 7850 201*1e9 0.3 [
I
1 L22 25 10 0 7850 201*1 e9 0.3 1 123 25 10 0 7850 201"1e9 0.3 1 L24 25 10 0 7850 201*1e9 0.3 i 1 L25 95 10 0 7850 2011 e9 0.3 i 1_26 25 10 0 7850 201"1e9 0.3 11 L27 25 10 0 7850 201*1e9 0.3
I
1 1_28 ne 10 0 7850 201*-1e9 0.3 1 4.c., 1 L29 25 10 0 7850 201*1e9 0.3 1 L30 25 10 0 7850 201*1e9 0.3 i 1 L31 25 10 0 7850 201"1e9 0.3 i ! 1 L32 18 20 0 7850 201*1e9 0.3 1 L33 6 18 0 7850 201"1e9 0.3 1i L34 18 18 0 7850 201*1e9 0.3
I
1 L35 5 18 0 7850 201*1e9 0.3 11 L36 10 18 0 7850 201'1 e9 0.3 1 L37 15 15 0 7850 201"1e9 0.3 i 1 L38 10 14 0 7850 201"1e9 0.3 11 L39 25 14 0 7850 201*1e9 0.3 1 L40 5 14 0 7850 201*1e9 0.3
I
1 L41 10 50 0 7850 201*1e9 0.3 The mass, the axis rotational inertia and the diameter rotational inertia of the cantilever disc are determined by calculation, the specific steps are as follows: determining, according to the design drawings of the cantilever disc, the geometric dimensions of the disc, including the disc radius R, the disc thickness h, and the material of the cantilever disc; determining the density of the cantilever disc by consulting the Metal Materials Manual; and obtaining the mass m of the cantilever disc by formula (3), obtaining the axis rotational inertia lp of the cantilever disc by formula (4), and obtaining the diameter rotational inertia Id of the cantilever disc by formula (5).
rn = p;71-12h (3) 1= 2 (4) mR-ttilt 4 (5) where R is the radius of the cantilever disc, and h is the thickness of the cantilever disc.
The mass, the axis rotational inertia and the diameter rotational inertia of the cantilever disc obtained in the present embodiment are shown in Table 2.
Table 2 Cantilever disc parameters for the small single-disc cantilever rotor experimental device with a spline joint structure Cantilever disc parameter Mass /kg Axis rotational inertia /kg * m2 Diameter rotational inertia licg* m2 13.8 0.58 0.29 The design parameters of the spline joint structure used in the embodiment are determined by the engineering drawings and the spline joint structure parameters of the small single-disc cantilever rotor experimental device with a spline joint structure. The other parameters of the rotor system with the spline joint structure refer to the working rotation speed range of the rotor system. The working rotation speed range of the engine rotor system is selected by consulting the Hero Engine Design Manual.
The working rotation speed range of the rotor system determined in the present embodiment is (.0 e tor I min, 5500r /m in) Step 1: calculating the critical rotation speed of the rotor system with the spline joint structure.
According to the rotor structure parameters of the rotor system with spline joint structure determined in the present embodiment, the system structure is simplified to a finite element model.
In the present embodiment, the process of simplifying the rotor system structure with the spline joint structure determined in the present embodiment to a finite element model includes: simplifying the rotor shaft to a rotor shaft beam unit, simplifying the cantilever disc to a rigid cantilever disc unit, simplifying the power turbine rear rolling bearing to a power turbine rear rolling bearing unit, and simplifying the spline joint structure to a spline joint structure unit. The finite element model parameters are given by the structural parameters determined in step 1.
After determining the above finite element model and each finite element model parameter, the rotor dynamic finite element method is used to program the finite element calculation program to calculate the model. The critical rotation speed of each order of the rotor system with the spline joint structure in the present embodiment is shown in Table 3.
Table 3 Critical rotation speed distribution Critical rotation speed First order (r/min)i Second order (rImin) Third order (r/min 1986 4192 8118 Step 2: determining the characteristic frequency band of the early frictional instability faults of the spline joint structure.
The characteristic frequency band of the early frictional instability faults /1".
defined by Formula (1) is * , where cr is the first order critical rotation speed of the rotor system. According to the critical rotation speed determined in step 2, it may be determined that the characteristic frequency band of the early frictional instability faults of the spline joint structure in the present embodiment is [1886.7r/ in:11,1986d min], i.e. [31.4 Hz,33.1HzI.
Step 3: collecting a sample of the vibration data of the rotor system with the spline joint structure.
In the present embodiment, the rotor system is flexibly connected to the motor through a flange plate, and the frequency converter controls the motor rotation speed to drive the rotor system. In the course of the experiment, two vibration displacement sensors collect the vibration signals of the cantilever disc in the horizontal and vertical directions, and a photoelectric sensor collects the real-time rotation speed of the rotor system. Controlling the frequency converter enables the rotor system to continuously accelerate from 300 Rpm, and vibration data during the acceleration process is collected, wherein the vibration signal and rotation speed signal at each moment is recorded.
Existing studies have shown that the instability threshold rotation speed of the rotor system with a spline joint structure is above the first order critical rotation speed. and in order to monitor the early instability faults in advance, 0.911cr is defined as a determining indicator. In the experimental process of the present embodiment, the collected rotation speed signal of the rotor system is determined in real time, wherein if the current rotation speed is greater than 0.9 c't, the subsequent process steps are carried out, and if the current rotation speed is less than 0.97C, the rotation speed is continued to be increased and the vibration data of the rotor system is continued to be collected.
Step 4: collecting the vibration signal of the characteristic frequency band of the early frictional instability faults of the spline joint structure.
In the present embodiment, after the current rotation speed reaches defined n * the signal 1-31-41{L'33'11-1zi in the characteristic frequency band of early frictional instability faults of the spline joint structure determined in step 2 is collected and recorded for the subsequent determination process.
Step 5, calculating the characteristic value of the early frictional instability faults of the spline joint structure.
The characteristic value of the early frictional instability faults of the spline s = " joint structure E is defined as * c; and -In the formula, 0 is the rotation speed of the current moment, 1"-gl'ilc'n'll represents the root mean square value of the amplitudes of all frequency component vibration signals in the characteristic frequency band of the early frictional instability
E
faults of the spline joint structure, and [SoS represents the root mean square value of the amplitudes of all frequency component vibration signals in 0.95c2,1.05c21 this frequency band Step 6, determining, according to the characteristic value, whether the early frictional instability faults of the spline joint structure occur.
The critical value of the characteristic value of the early frictional instability faults of the spline joint structure is defined as 0.25; and the characteristic value of the faults calculated in step 5 is compared to 0.25 to determine whether the early frictional instability faults of the spline joint structure occur. If the calculated value 5" is less than 0.25, no early frictional instability faults of the spline joint structure occur at this time, and it is returned to step 4; at which point the rotation speed can continue to be increased and the rotor system vibration data can continue to be collected. If the calculated value -is greater than 0.25, the early frictional instability faults of the spline joint structure occur at this time, and it is necessary to set off an alarm and stop the rotor system; and check the wear of the spline surface and the positioning surface of the spline joint structure.
According to the statistical experimental results; the frequency band range [0.95n '&..,] of instability is determined as, and the critical value of the characteristic value of instability faults is determined to be 0.25. The experimental results are summarized as seen in the following table: 1. i Characteristic value of 1 No. 1 1 instability faults 1 Instability 1 Ratio instability frequency 2.06 1 1 frequency i to critical rotation speed 1 98.8% 32.8Hz 1 2 31.6Hz 95.2% 0.46 1 3 1 1.88 32 2Hz 1 97.6% 4 31.9Hz 1 96.1% 0.36 The results of experimental data processing of the early frictional instability faults of the spline joint structure are shown in Figure 2.
In the present embodiment, the rotation speed of the rotor system continuously increases, and the characteristic value of faults at the current moment is calculated in real time. It is found that when the rotation speed of the rotor system is raised to 4043r/min, the fault characteristics calculated at
S
this time as -= 0,46 is greater than 0.25, and it is determined that the early frictional instability faults of the spline joint structure occur, the alarm is set off and the rotor system is stopped in time, and the wear of the spline joint structure is checked after the slopping. After the checking, it is found that the fault characteristics are in line with the early instability, indicating that the method of the present invention can effectively detect and determine the early frictional instability faults of the spline joint structure, and can avoid the harm caused by the transformation from early instability into serious instability.
So far, the whole process of the identification method of early frictional instability faults of the spline joint structure proposed in the present invention has been completed.
Although embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are exemplary and cannot be construed as limitations of the present invention, those of ordinary skill in the art may change, modify, replace and vary the above embodiments within the scope of the present invention without departing from the principles and purposes of the present invention.
Claims (7)
- What is claimed is: 1. A method for identifying early frictional instability faults of spline joint structure; comprising following steps of: step 1. determining a critical rotation speed n''' of a rotor system with the spline joint structure; 9511 n",1 step 2: determining a characteristic frequency band "" ' of the early frictional instability faults of the spline joint structure; step 3: acquiring vibration data of the rotor system with the spline joint structure: wherein when a rotation speed of the rotor system is greater than or equal to a set rotation speed, subsequent process steps are earned out, otherwise the vibration data of the rotor system is continued to be collected; step 4: processing the vibration data of the rotor system obtained in step 3 after the rotation speed of the rotor system is greater than or equal to the set rotation speed, to obtain frequency domain components of the vibration data; step 5: calculating a characteristic value Sc of the early frictional instability faults of the spline joint structure based on the frequency domain components of the vibration data obtained in step 4, by using a formula, [0 95 f2,1,0512j where is a rotation speed of the rotor system at a current moment; represents, in the frequency domain components of the vibration data obtained in step 4, a root mean square value of amplitudes of all the vibration data in the characteristic frequency band of the early frictional instability faults of the spline joint structure; represents, in the frequency domain components of the vibration data obtained in step 4: a root mean square value of amplitudes of all the 0.9.50,1.050 vibration data in a frequency band; and step 6, determining according to the characteristic value obtained in step 5 whether the early frictional instability faults of the spline jointSstructure occur, wherein if the calculated value "c is less than 0.25, it is determined that no early frictional instability faults of the spline joint structure occur at this time, and it is returned to step 3 to continue to collect the vibration data of the rotor system; and if the calculated value is greater than or equal to 0.25, it is determined that the early frictional instability faults of the spline joint structure occur at this time.
- 2 The method for identifying early frictional instability faults of a spline joint structure according to claim 1, wherein in step 1, a finite element method is used to calculate the critical rotation speed of the rotor system with the spline joint structure.
- 3. The method for identifying early frictional instability faults of a spline joint structure according to claim 2, wherein in step 1, when using the finite element method for calculation, a process of simplifying the rotor system with the spline joint structure to a finite element model includes: simplifying a low-pressure shaft to a combination of several low-pressure shaft-beam units, simplifying a high-pressure shaft to a combination of several high-pressure shaft-beam units, simplifying a low-pressure fan to a flexible low-pressure fan disc unit, simplifying a low-pressure turbine to a rigid low-pressure turbine disc unit, simplifying a fan front rolling bearing to a fan front rolling bearing unit, simplifying a low-pressure turbine rear rolling bearing to a low-pressure turbine rear bearing unit, simplifying a high-pressure compressor to a rigid high-pressure compressor disc unit; simplifying a high-pressure turbine to a rigid high-pressure turbine disc unit, simplifying a high-pressure compressor front rolling bearing to a high-pressure compressor front rolling bearing unit, simplifying an intermediate rolling bearing to an intermediate rolling bearing unit, simplifying the spline joint structure to a spline joint structure unit, and simplifying a receiver to a massless receiver unit.
- 4. The method for identifying early frictional instability faults of a spline joint structure according to claim 2, wherein in step 1, when using the finite element method for calculation, finite element model parameters comprise: an elastic modulus, a shear modulus, a material density, a high-pressure shaft-beam unit diameter, a low-pressure shaft-beam unit inner diameter, a low-pressure shaft-beam unit outer diameter; damping, flexible low-pressure fan disc unit mass, rigid high-pressure compressor disc unit mass, rigid high-pressure turbine disc unit mass, rigid low-pressure turbine disc unit mass, flexible low-pressure fan disc unit rotational inertia, rigid high-pressure compressor disc unit rotational inertia; rigid high-pressure turbine disc unit rotational inertia, rigid low-pressure turbine disc unit rotational inertia, spline joint structure unit stiffness; spline joint structure unit damping; minimum clearance value; an intermediate rolling bearing unit position, a flexible fan low-pressure disc unit position, a low-pressure turbine disc unit position, a fan front rolling bearing unit position, a low-pressure turbine rear bearing unit position, a high-pressure compressor front rolling bearing unit position, a rigid high-pressure compressor disc unit position, a rigid high-pressure turbine disc unit position, and a spline joint structure unit position.
- The method for identifying early frictional instability faults of a spline joint structure according to claim 1, wherein in step 3, said set speed is 0.9 licY
- 6. The method for identifying early frictional instability faults of a spline joint structure according to claim 1, wherein in step 4, the vibration data of the rotor system collected in step 3 after the rotation speed of the rotor system is greater than or equal to the set rotation speed is divided per second; and the vibration data of first few cycles before each second is selected for fast Fourier transform; to obtain frequency domain components of the vibration data.
- 7. The method for identifying early frictional instability faults of a spline joint structure according to claim 6, wherein in step 4, the vibration data of first 16 cycles before each second is selected for fast Fourier transform.
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| JP2003344150A (en) * | 2002-05-24 | 2003-12-03 | Kawasaki Heavy Ind Ltd | Condition diagnosing method and apparatus therefor by analyzing shaft vibration of rotating machine |
| AU2015201595A1 (en) * | 2015-03-27 | 2016-10-13 | Tensor Systems Pty Ltd | Vibration measurement and analysis |
| CN110082103A (en) * | 2018-04-26 | 2019-08-02 | 广东电网有限责任公司 | A kind of nozzle of steam turbine cut-off shaft system unstability fault early warning method |
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| CN110131193B (en) * | 2018-02-02 | 2020-09-08 | 中国航发商用航空发动机有限责任公司 | Method and system for monitoring surge fault of aircraft engine |
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| JP2003344150A (en) * | 2002-05-24 | 2003-12-03 | Kawasaki Heavy Ind Ltd | Condition diagnosing method and apparatus therefor by analyzing shaft vibration of rotating machine |
| AU2015201595A1 (en) * | 2015-03-27 | 2016-10-13 | Tensor Systems Pty Ltd | Vibration measurement and analysis |
| CN110082103A (en) * | 2018-04-26 | 2019-08-02 | 广东电网有限责任公司 | A kind of nozzle of steam turbine cut-off shaft system unstability fault early warning method |
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