Blisk damping ring structure vibration attenuation characteristic analysis method

Abstract

The invention discloses a blisk damping ring structure vibration attenuation characteristic analysis method, and belongs to the technical field of gas turbine engine vibration attenuation structure design. The method comprises the following steps: calculating a blisk standing wave mode; the vibration parameters under the specific vibration stress are converted; dividing a viscous area and a sliding area in the vibration process; calculating friction energy consumption of the damping ring in one period; calculating a damping ratio provided by the damping ring; and drawing a damping ratio characteristic curve. According to the method, the damping ratio of the blisk damping ring structure under different vibration stresses can be calculated only through one-time finite element modal analysis, and the calculation efficiency is improved.

Description

Technical Field

[0001] The present application belongs to the technical field of aero-engines, and in particular to a method for predicting the vibration reduction characteristics of an integral blade disk damping ring of an aero-engine. Background Art

[0002] Most modern advanced aircraft engines use an integral blade disc structure. By eliminating the tenon between the blade and the disc, the rotor mass can be greatly reduced and the air leakage between the blade edges can be eliminated. However, due to the lack of tenon tooth contact surface, the dry friction damping of the system is greatly reduced, which is prone to high cycle fatigue failure.

[0003] Dry friction damping is not sensitive to changes in the working environment and can work under harsh conditions in aircraft engines. It is a commonly used damping structure in aircraft engines. Integral blades often provide dry friction damping by installing damping rings.

[0004] Damping rings can be divided into closed rings and open rings. Closed rings are usually installed on the inner side of the outer edge of the main structure by heat assembly. The contact positive pressure drop or vibration caused by wear can easily cause it to fall out. Open rings are installed in the damping ring groove after compression, and mainly rely on centrifugal force to provide positive pressure. On the one hand, it has the potential to provide greater damping at a higher speed. On the other hand, its contact state is not sensitive to wear and is not easy to fall out of the damping ring groove.

[0005] The integral blade damping ring structure is a nonlinear system. To analyze its vibration reduction characteristics, the traditional methods are time integration method or harmonic balance method. These two methods require multiple iterative calculations, which often take several minutes to tens of minutes to analyze the vibration reduction characteristics under a certain excitation force; and it is difficult to accurately obtain the magnitude of the excitation force in engineering practice, which makes the application of the above two methods have certain limitations. Summary of the invention

[0006] The purpose of this invention is to provide an efficient method for analyzing the vibration reduction characteristics of the integral blade damping ring structure that is independent of the specific distribution of the excitation force. Figure 2 A set of superimposed beams is shown. The main structure is considered to be the neutral plane radius R g , thickness 2c g The damping ring is considered as the neutral surface radius R d , thickness 2c d The radius of the contact surface between the main structure and the damping ring is R f .

[0007] To achieve the above object, the analysis method of the present invention comprises the following steps:

[0008] Step 1: Perform modal analysis on the possible resonant modes of the integral blade disk model;

[0009] Step 2: Convert the vibration parameters according to the given vibration stress;

[0010] Step 3: Divide the sticking and slipping areas during the vibration process;

[0011] Step 4: Calculate the friction energy consumption of the entire damping ring in one cycle;

[0012] Step 5: Calculate the damping ratio provided by the damping ring;

[0013] Step 6: Repeat steps 2-5 with different vibration stresses to obtain the damping ratio characteristic curve.

[0014] Among them, in step 1, for a given integral blade disk model, commercial finite element software is used to calculate the standing wave mode of the required order of N node diameters through modal analysis. The maximum radial modal displacement B at the damping ring groove is obtained. modal , modal vibration stress of blade dangerous point σ modal and the maximum modal vibration kinetic energy of the main structure W modal .

[0015] In step 2, for a given vibration stress σ at a dangerous point, the following formula is used to calculate the maximum radial displacement B and the maximum vibration kinetic energy W at the damping ring groove: max ;

[0016]

[0017] The integral blade and damping ring are simplified as a superimposed beam model. Due to symmetry, only the 1 / 4N sector is calculated. The circumferential coordinate θ∈[0,π / 2N] is defined.

[0018] The expression of critical amplitude is:

[0019]

[0020] Among them, C is a constant defined for the convenience of calculation:

[0021]

[0022] Where, μ is the friction coefficient, P is the contact normal pressure per unit length of the damping ring, E is the elastic modulus of the damping ring material, and A d is the cross-sectional area of ​​the damping ring.

[0023] Among them, in step 3, the transition point between the sticky and slip states is θ t , when 0≤θ≤θ t When θ t When <θ≤π / 2N, the damping ring and the main structure will slide during vibration, which is called the slip zone.

[0024] When B≤B c When θ t =π / 2N; when When θ t =0; in other cases, θ t is the solution to the following equation:

[0025]

[0026] In the slip zone, the maximum relative displacement between the damping ring and the main structure is:

[0027]

[0028] Among them, in step 4, the friction energy consumption of the entire damping ring in one vibration cycle is W f is the sum of the friction energy consumption of each point on the damping ring, and its expression is:

[0029]

[0030] Among them, in step 5, the damping ratio provided by the damping ring is:

[0031]

[0032] Among them, in step 6, by selecting different dangerous point vibration stresses σ within the range that the integral blade disk can withstand, repeating steps 2-5 to calculate the damping ratio, the damping ratio-vibration stress relationship curve of the damping ring, that is, the damping ratio characteristic curve, can be obtained.

[0033] The advantages and beneficial effects of the present invention are as follows: the traditional calculation methods for the damping ratio of the integral blade disk damping ring structure are the time integration method and the harmonic balance method. The time integration method needs to be calculated with a smaller time step to obtain the steady-state response of the structure under the action of an exciting force of a given frequency; the harmonic balance method needs to be iteratively calculated in the frequency domain, and can calculate the steady-state response of the structure under a given exciting force within a certain frequency range. These two methods require the calculation of dozens of modes when the degrees of freedom are reduced; when calculating the response, each vibration stress requires several minutes of calculation time; and the magnitude and distribution of the exciting force on the integral blade disk need to be known, but it is very difficult to accurately obtain the exciting force through flow field analysis. This method only requires modal analysis of the first-order mode; it only takes a few seconds to calculate the damping ratio under dozens of vibration stresses within a certain range; and there is no need to specify the exciting force distribution. It is suitable for quickly determining the size of the damping ring in the early stages of design. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a flow chart of the vibration reduction characteristic analysis method of the integral blade damping ring structure;

[0035] Figure 2 for Figure 1 Schematic diagram of the superimposed beam model in the method shown;

[0036] Figure 3 for Figure 1 A schematic diagram of a certain level of the integral blade disk structure in the method shown;

[0037] Figure 4 for Figure 1 Schematic diagram of the damping ratio characteristic curve calculated by the method shown. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical solutions and advantages of the implementation of this application clearer, the technical solutions in the embodiments of this application will be described in more detail below in conjunction with the drawings in the embodiments of this application.

[0039] The blade finite element model is divided according to the real blade three-dimensional geometric model, such as Figure 3 As shown, the damping ring is installed below the front edge of the edge plate.

[0040] The neutral radius of the blade edge plate (the average value of the upper and lower surface radii) is R g =243.5mm, thickness 2c g =5mm; the damping ring is a rectangular cross-section open ring, the neutral surface radius R d =240mm, radial thickness 2c d =2mm, axial width b = 2mm; the contact surface radius R of the integral blade and the damping ring f =241mm, friction coefficient μ=0.3; density of damping ring is ρ=4.68g / cm 3 , the elastic modulus is E=111.6GPa.

[0041] The finite element method is used to perform modal analysis on the 10-diameter 4th-order standing wave mode. The following modal parameters can be directly read from the displacement and stress cloud diagrams: Maximum radial modal displacement B at the damping ring installation position modal =12.67mm, blade dangerous point modal vibration stress σ modal =53021MPa.

[0042] Taking ANSYS as an example, by selecting all elements and nodes, execute the command:

[0043] etable,allkene,kene

[0044] SSUM

[0045] The maximum modal vibration kinetic energy W of the entire blade can be obtained modal =1.58×10 8 mJ.

[0046] Taking the vibration stress at the dangerous point σ=115MPa as an example, it can be converted to: the maximum radial displacement of the damping ring installation position B=0.0275mm, the maximum vibration kinetic energy W max =745mJ.

[0047] Ignore the opening, preload and local non-contact of the damping ring, and assume that the speed Ω=13000r / min at resonance. The normal contact pressure per unit length provided by the centrifugal force of the damping ring can be expressed as: P=2bρR d c d Ω 2 =8.326N.

[0048] Critical amplitude B c =0.0229mm, yes By solving the equation:

[0049]

[0050] The transition point θ t =0.0543rad.

[0051] The calculated friction energy is W f =0.888mJ.

[0052] The damping ring provides a damping ratio ζ=0.00948%.

[0053] The vibration stress σ at the dangerous point is selected to range from 0 to 600 MPa, and the damping ratio characteristic curve is obtained as follows: Figure 4 shown.

Claims

1. A method for analyzing vibration reduction characteristics of an integral blade damping ring structure, characterized in that: include: Step 1: Perform modal analysis on the possible resonant modes of the integral blade disk model; Step 2: Convert the vibration parameters according to the given vibration stress; Step 3: Divide the sticking and slipping areas during the vibration process; Step 4: Calculate the friction energy consumption of the entire damping ring in one cycle; Step 5: Calculate the damping ratio provided by the damping ring; Step 6: Repeat steps 2 to 5 with different vibration stresses to obtain the damping ratio characteristic curve.

2. The vibration reduction characteristic analysis method of the blisk damping ring structure according to claim 1 is characterized by: In step 1, for a given integral blade disk model, commercial finite element software is used to calculate the standing wave mode of the required order of N node diameters through modal analysis; the maximum radial modal displacement B at the damping ring groove is obtained. modal , modal vibration stress of blade dangerous point σ modal and the maximum modal vibration kinetic energy of the main structure W modal .

3. The vibration reduction characteristic analysis method of the blisk damping ring structure according to claim 1 is characterized by: In step 2, for a given vibration stress σ at the dangerous point, the maximum radial displacement B and the maximum vibration kinetic energy W at the damping ring groove are calculated using the following formula: max ; 4. The method for analyzing vibration reduction characteristics of a blisk damping ring structure according to claim 3 is characterized in that: The integral blade and damping ring are simplified into a superimposed beam model. Due to symmetry, only the 1 / 4N sector is calculated. The circumferential coordinate θ∈[0,π / 2N] is defined. The expression of critical amplitude is: Where, μ is the friction coefficient, P is the contact normal pressure per unit length of the damping ring, E is the elastic modulus of the damping ring material, and A d is the cross-sectional area of ​​the damping ring; C is a constant.

5. The method for analyzing vibration reduction characteristics of a blisk damping ring structure according to claim 4, characterized in that: The expression of constant C is:

6. The method for analyzing vibration reduction characteristics of a blisk damping ring structure according to claim 1, characterized in that: In step 3, the transition point between stick and slip states is θ t , when 0≤θ≤θ t When θ t When <θ≤π / 2N, the damping ring and the main structure will slide during vibration, which is called the slip zone.

7. The method for analyzing vibration reduction characteristics of a blisk damping ring structure according to claim 6, characterized in that: When B≤B c When θ t =π / 2N; when When θ t =0; in other cases, θ t is the solution to the following equation: In the slip zone, the maximum relative displacement between the damping ring and the main structure is:

8. The method for analyzing vibration reduction characteristics of a blisk damping ring structure according to claim 1, characterized in that: In step 4, the friction energy W of the entire damping ring in one vibration cycle is f is the sum of the friction energy consumption of each point on the damping ring, and its expression is:

9. The method for analyzing vibration reduction characteristics of a blisk damping ring structure according to claim 1, characterized in that: In step 5, the damping ratio provided by the damping ring is:

10. The method for analyzing vibration reduction characteristics of a blisk damping ring structure according to claim 1, characterized in that: In step 6, by selecting different dangerous point vibration stresses σ within the tolerable range of the integral blade disk and repeating steps 2-5 to calculate the damping ratio, the damping ratio-vibration stress relationship curve of the damping ring, that is, the damping ratio characteristic curve, can be obtained.

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