Aero-engine gear whole machine state resonance rotating speed correction method

Abstract

This application belongs to the field of aero-engine technology, and specifically relates to a method for correcting the resonance speed of aero-engine gears in their overall state. The method involves obtaining a first resonance speed when the tooth width, spokes, and fillets are all at their lower tolerance limits; obtaining a second resonance speed when the tooth width, spokes, and fillets are all at their lower tolerance limits; obtaining a third resonance speed when the tooth width, spokes, and fillets are at their standard dimensions; and using the difference between the first and third resonance speeds as the lower limit K of the range of a first correction coefficient K. min The difference between the second and third resonant speeds will be used as the upper limit of the range of the first correction coefficient K. max The elastic modulus E of the gear material at the operating temperature t The elastic modulus E of the gear material at 20°C 20 The arithmetic square root of the quotient is used as the second correction coefficient; the third resonant speed is obtained by correcting the standard dimensions of tooth width, spokes, and fillet using the range of the first correction coefficient K and the second correction coefficient, thus obtaining a more accurate range of resonant speed for the whole machine.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of aero-engines, and particularly relates to a gear whole-machine state resonance speed correction method of an aero-engine. BACKGROUND

[0002] The gear transmission system is an important component part of the mechanical system of an aero-fan and aero-jet engine (including a central transmission device, an engine accessory case and an aircraft accessory case). The central transmission and the engine accessory case are connected through a central transmission rod, and the engine accessory case is connected with the aircraft accessory case through a flexible shaft. When the engine starts, a starter installed on the aircraft accessory case transmits output power to the high-pressure rotor of the engine through the gear system, the flexible shaft and the transmission rod and the like, so that the engine starts. When the engine normally works, each accessory installed on the aircraft accessory case and the engine accessory case extracts power from the high-pressure rotor of the engine through the aircraft accessory case, the engine accessory case and the central transmission and the like, so as to ensure normal work. The main shortcomings are as follows: the working temperature range of the gear of the aero-engine transmission system is 100-200 DEG C, the temperature causes the change of the elastic modulus of the material, directly affects the natural frequency of the gear, and thus affects the calculation result of the resonance speed; in addition, the actual machining gear has a size deviation, and the actual machining size affects the natural frequency of the gear, and also affects the calculation result of the resonance speed. The prior art scheme does not consider the influence of the temperature and the machining tolerance on the calculation of the resonance speed, so that the calculated resonance speed of the gear is greatly deviated from the actual value, and there is a risk that the resonance point still exists in the working speed range after the gear frequency modulation design is completed according to the calculation result of the resonance speed, and the gear may be resonated and fatigued in work, so as to affect the functionality and reliability of the aero-engine. We have once encountered such a problem in the design process. The calculated resonance speed of a certain vibration mode of the bevel gear of a certain engine is 2% higher than the maximum use speed after the frequency modulation design, and it is considered to meet the design requirements. However, vibration fatigue failure occurs in the use process of the field, which leads to large-area engine flight stop, and the reason is that the calculated resonance speed does not consider the temperature and the size tolerance. SUMMARY

[0003] In order to solve the above problems, the application provides a gear whole-machine state resonance speed correction method of an aero-engine, which comprises the following steps.

[0004] obtaining a first resonance speed when the tooth width, the web and the round corner are all lower limit tolerances;

[0005] obtaining a second resonance speed when the tooth width, the web and the round corner are all upper limit tolerances;

[0006] obtaining a third resonance speed when the tooth width, the web and the round corner are standard sizes;

[0007] taking the difference between the first resonance speed and the third resonance speed as the lower limit K of the value range of a first correction coefficient Kmin The difference between the second resonance speed and the third resonance speed is taken as the upper limit K of the value range of the first correction coefficient K max ;

[0008] The arithmetic square root of the quotient of the elastic modulus E of the gear material at the working temperature t and the elastic modulus E of the gear material at 20℃ 20 is taken as the second correction coefficient;

[0009] The third resonance speed when the standard dimensions of the gear width, web and round corner are corrected by the range of the first correction coefficient K and the second correction coefficient, to obtain the resonance speed range of the whole machine state.

[0010] Preferably, the third resonance speed calculation formula of the standard dimensions of the gear width, web and round corner includes:

[0011] The number of gear pitch diameters m and its static natural frequency f are analyzed by finite element method;

[0012] The dynamic natural frequency f d is calculated based on the static natural frequency;

[0013] The third resonance speed N g of the thin-web spur gear is calculated based on the dynamic natural frequency f d .

[0014] Preferably, the calculation formula of the third resonance speed N g is:

[0015] N g =60×f d / (Z±m);

[0016] Wherein, Z is the number of gear teeth.

[0017] Preferably, the calculation formula of the dynamic natural frequency f d is:

[0018]

[0019] Wherein, N is the gear shaft speed, and B is the dynamic frequency coefficient.

[0020] Preferably, when the vibration mode of the gear is forward wave, m is negative, and when the vibration mode of the gear is backward wave, m is positive.

[0021] Preferably, the resonance speed range calculation formula of the whole machine state is:

[0022]

[0023] K min =60×f dmin(Z±m)-60×f d (Z±m);

[0024] K max =60×f dmax (Z±m)-60×f d (Z±m);

[0025] f dmin is the natural frequency of the gear when the tooth width, web, and round corner are all lower limit of tolerance, Hz

[0026] f dmax is the natural frequency of the gear when the tooth width, web, and round corner are all upper limit of tolerance, Hz

[0027] The advantages of the present application include: the present application considers the influence of the working temperature in the whole machine state and the actual machining size tolerance, realizes the accurate prediction of the resonance speed range of the gear in the whole machine state which meets the drawing tolerance requirement, and based on the result, the gear frequency is adjusted, which can ensure that the gear in the whole machine state does not occur vibration fatigue damage, and improves the safety and reliability of the engine in use. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 is a preferred embodiment of the present application, an aero-engine gear whole machine state resonance speed correction method;

[0029] Figure 2 is a preferred embodiment of the present application, an aero-engine bevel gear size and tolerance chart;

[0030] Figure 3 is a curve of the elastic modulus of the wheel changing with temperature. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical scheme and advantages of the present application clearer, the technical scheme in the present application will be described in more detail below in combination with the drawings in the present application. In the drawings, the same or similar reference signs represent the same or similar elements or elements with the same or similar functions throughout. The described embodiments are part of the embodiments of the present application, not all of the embodiments. The embodiments described below by reference to the drawings are exemplary and are intended to explain the present application, and cannot be understood as limiting the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application. The embodiments of the present application will be described in detail below in combination with the drawings.

[0032] As Figure 1 shown, the present application provides an aero-engine gear whole machine state resonance speed correction method, comprising:

[0033] obtaining the first resonance speed when the tooth width, the web, and the fillet are all lower limit tolerances;

[0034] obtaining the second resonance speed when the tooth width, the web, and the fillet are all upper limit tolerances;

[0035] obtaining the third resonance speed when the tooth width, the web, and the fillet are all standard sizes;

[0036] taking the difference between the first resonance speed and the third resonance speed as the lower limit K of the value range of the first correction coefficient K min , and taking the difference between the second resonance speed and the third resonance speed as the upper limit K of the value range of the first correction coefficient K max ;

[0037] taking the arithmetic square root of the quotient of the elastic modulus E of the gear material at the working temperature t and the elastic modulus E of the gear material at 20℃ 20 as the second correction coefficient;

[0038] correcting the third resonance speed when the tooth width, the web, and the fillet are all standard sizes by the range of the first correction coefficient K and the second correction coefficient, to obtain the resonance speed range of the whole machine state.

[0039] Preferably, the calculation formula of the third resonance speed when the tooth width, the web, and the fillet are all standard sizes comprises:

[0040] analyzing the number of gear pitch diameters m and the static natural frequency f of the gear by finite element analysis;

[0041] calculating the dynamic natural frequency f d based on the static natural frequency;

[0042] calculating the third resonance speed N g of the thin-web spur gear based on the dynamic natural frequency f d .

[0043] Preferably, the calculation formula of the third resonance speed N g is:

[0044] N g = 60 x f d / (Z ± m);

[0045] wherein Z is the number of gear teeth.

[0046] Preferably, the calculation formula of the dynamic natural frequency f d is:

[0047]

[0048] wherein N is the gear shaft speed, and B is the dynamic frequency coefficient.

[0049] Preferably, m is negative when the gear mode is a traveling wave, and m is positive when the gear mode is a standing wave.

[0050] Preferably, the formula for calculating the resonance speed range of the whole machine is:

[0051]

[0052] K min = 60 x f dmin / (Z ± m) - 60 x f d / (Z ± m);

[0053] K max = 60 x f dmax / (Z ± m) - 60 x f d / (Z ± m);

[0054] f dmin is the natural frequency of the gear when the tooth width, web, and round corner are all lower limit tolerances, Hz;

[0055] f dmax is the natural frequency of the gear when the tooth width, web, and round corner are all upper limit tolerances, Hz

[0056] The advantages of the present application include: the present application takes into account the effects of the working temperature of the whole machine and the actual machining size tolerance, realizes accurate prediction of the resonance speed range of the gear in the whole machine state that meets the drawing tolerance requirements, and based on the result, the gear frequency is adjusted, which can ensure that the gear in the whole machine state does not occur vibration fatigue failure, and improves the safety and reliability of the engine

[0057] The structure of a central driven bevel gear of an aero-engine is taken as an example, as shown in Figure 2 , the web size is 8 ± 0.3 mm, and the tooth width is 21 mm (free tolerance ± 0.26 mm). The three-pitch-radius traveling wave resonance speed of the bevel gear at room temperature is 76%, and the four-pitch-radius standing wave resonance speed is 104.3%. The curve of the elastic modulus of the bevel gear with temperature is shown in Figure 3 . Through temperature correction, the three-pitch-radius traveling wave and four-pitch-radius standing wave resonance speeds at the working temperature of the whole machine of 200℃ are 74.94% and 102.8% respectively. Considering the effects of the web and tooth width tolerances, the size tolerance correction coefficients of the three-pitch-radius traveling wave and four-pitch-radius standing wave are ± 0.86% and ± 0.92% respectively. The three-pitch-radius traveling wave speed range of the bevel gear in the whole machine state is 74.08% ~ 75.8%, and the four-pitch-radius standing wave speed range is 101.88% ~ 103.72%. The measured resonance speeds of the three-pitch-radius traveling wave and four-pitch-radius standing wave are 74.95% and 102.5% respectively. The measured resonance speeds are within the calculated speed range, which proves that the present application can accurately predict the resonance speed range of the gear in the whole machine state.

[0058] Table 1 resonance speed calculation results at different temperatures

[0059] Temperature (°C) 20 70 100 170 200 Three nodal diameter forward wave resonance speed (%) 76.0 75.78 75.65 75.26 74.94 Four nodal diameter backward wave resonance speed (%) 104.3 104.0 103.8 103.3 102.8

[0060] Table 2 resonance speed correction factor calculation results based on drawing size tolerance

[0061]

[0062] Table 3 comparison results of calculated and measured resonance speeds in the whole machine state

[0063]

[0064] Compared with the traditional resonance speed calculation method, the present application considers the influence of the working temperature in the whole machine state and the actual machining size tolerance, realizes the accurate prediction of the resonance speed range of any gear in the whole machine state which meets the drawing tolerance requirements, and based on the results, the gear frequency modulation is carried out, which can ensure that the gear in the whole machine state does not occur vibration fatigue failure, and improves the safety and reliability of the engine use.

[0065] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited to this, any person skilled in the art can easily think of changes or replacements within the technical range disclosed in the present application, which should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. An aeroengine gear whole machine state resonance rotational speed correction method, characterized in that, Comprise: Obtain the first resonance speed when the tooth width, web, and round corner are all lower limit of tolerance, obtain the second resonance speed when the tooth width, web, and round corner are all upper limit of tolerance, obtain the third resonance speed when the tooth width, web, and round corner are all standard size; The difference between the first resonance rotational speed and the third resonance rotational speed is taken as the lower limit K of the value range of the first correction coefficient K min The difference between the second resonance rotational speed and the third resonance rotational speed is taken as the upper limit K of the value range of the first correction coefficient K max ; The elastic modulus E of the gear material at the working temperature t The elastic modulus E of the gear material at 20°C 20 The arithmetic square root of the quotient is used as the second correction factor; Obtain the whole machine state resonance speed range by the range of the first correction coefficient K and the second correction coefficient correction of the third resonance speed when the tooth width, web, and round corner are all standard size; The third resonance speed calculation formula when the tooth width, web, and round corner are all standard size comprises: Analyze the number of gear pitch diameter m and its static natural frequency f by finite element method; Calculating dynamic natural frequency f based on static natural frequency d ; Based on dynamic natural frequency f d Computing the third resonance rotational speed N of a thin-web straight spur gear g ; Third resonance rotational speed N g The calculation formula is: N g = 60 x f d / (Z ± m); Wherein, Z is the number of gear teeth; Dynamic natural frequency f d The formula for calculating is: Wherein, N is the gear shaft speed, B is the dynamic frequency coefficient; The whole machine state resonance speed range calculation formula is: K min = 60 x f dmin / (Z ± m) - 60 x f d / (Z ± m); K max = 60 x f dmax / (Z ± m) - 60 x f d / (Z ± m); f dmin Natural frequency of gear, Hz, for which the tooth width, web, and fillet are all lower tolerance limits. f dmax Natural frequency of gear with upper limit of tooth width, web, and round corner tolerance, Hz.

2. The method of claim 1, wherein, When the vibration mode of the gear is forward wave, m is negative, when the vibration mode of the gear is backward wave, m is positive.

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