Helicopter engine case vibration reduction method based on vibration energy flow control

Abstract

The invention discloses a helicopter engine case vibration reduction method based on vibration energy flow control, and belongs to the technical field of structural dynamic response vibration reduction analysis. The invention aims to solve the problem of poor vibration reduction effect of the helicopter engine case in the existing method. The method comprises the steps of firstly constructing and correcting a finite element model of the helicopter engine case, then obtaining a vibration energy flow amplitude of each position on the case by calculating a vibration energy flow component and a vector of the vibration energy flow component of each position on a case surface, drawing a three-dimensional diagram of the vibration energy flow based on the vibration energy flow amplitude, and calculating the vibration energy flow of the helicopter engine case. Visualization of the distribution condition of the vibration energy flow in the cartridge receiver structure is achieved, the concentrated area of the vibration energy flow in the cartridge receiver can be accurately analyzed, finally the hanging point position of the engine is adjusted according to the distribution condition of the vibration energy flow so as to reduce the amplitude of the vibration energy flow in a specific area, then the vibration amplitude can be reduced, and the vibration reduction effect of the cartridge receiver can be improved. The method can be applied to vibration reduction of the helicopter engine case.

Description

Technical Field

[0001] The invention belongs to the technical field of structural dynamic response vibration reduction analysis, and in particular relates to a helicopter engine casing vibration reduction method based on vibration energy flow control. Background Art

[0002] The unique structure of helicopters determines their high maneuverability and flexibility, which enables them to play a wide range of roles in various fields. However, effectively controlling the vibration of helicopters has become a key issue that designers need to think about and urgently overcome.

[0003] The main reduction transmission system (including high-speed spiral bevel gear transmission components and casing) is a key core component of the helicopter. The vibration generated by the high-speed operation of the gear is transmitted to the casing through the shaft and bearings, causing the casing to vibrate and make noise, which directly affects the safety, life and comfort of the helicopter. The casing vibration is mainly caused by the impact force generated during meshing due to the manufacturing error and installation error of the gear pair, as well as the dynamic meshing force generated by the change of meshing stiffness.

[0004] The current analysis of helicopter vibration reduction issues mainly focuses on the vibration of the gears in the engine and main reduction transmission system, but does not focus on the nature of engine casing vibration, that is, the distribution of vibration energy in the engine casing structure. Therefore, the existing methods are still relatively limited in their effect on helicopter engine casing vibration reduction.

[0005] If the distribution of vibration energy in the engine casing structure can be accurately reflected, and the position of the engine's hanging point on the casing can be adjusted according to the distribution of vibration energy to control the distribution of vibration energy, then some parts of the casing can be prevented from being damaged due to excessive vibration energy. This will have important theoretical significance and engineering value for helicopter vibration analysis and vibration reduction. Summary of the invention

[0006] The purpose of the present invention is to improve the vibration reduction effect of a helicopter engine casing, and a vibration energy flow control-based helicopter engine casing vibration reduction method is proposed.

[0007] The technical solution adopted by the present invention to solve the above technical problems is: a helicopter engine casing vibration reduction method based on vibration energy flow control, the method specifically comprising the following steps:

[0008] Step 1: construct a finite element model of a helicopter engine casing, set the structural damping parameters and boundary conditions of the finite element model, and then correct the damping parameters of the finite element model through modal analysis to obtain a corrected casing finite element model;

[0009] The position of the engine attachment point on the finite element model of the casing after random initialization correction;

[0010] Step 2: Select the analysis frequency ω, and after applying the excitation load to the engine attachment point, perform steady-state dynamic analysis on the modified casing finite element model to obtain the displacement of each node in each unit;

[0011] Step 3, curve fitting is performed on the displacement of each node in each unit obtained in step 2 to obtain the displacement of each position on the casing surface, and the internal force of each position is calculated based on the displacement of each position;

[0012] Step 4: For each position on the casing surface, the vibration energy flow component in the x-axis direction and the vibration energy flow component in the y-axis direction are calculated according to the displacement and the internal force, and then the magnitude of the vibration energy flow vector at each position is calculated according to the vibration energy flow component, so as to obtain the vibration energy flow distribution on each wall surface of the casing;

[0013] Step 5, determining the vibration energy flow concentration area according to the vibration energy flow distribution on each wall surface of the casing, and then adjusting the position distribution of the engine hanging point according to the vibration energy flow concentration area;

[0014] Step 6, using the engine hanging point position adjusted in step 5, return to step 2 and end when there is no vibration energy flow concentration area on each wall surface of the casing.

[0015] The beneficial effects of the present invention are:

[0016] The present invention first constructs and corrects the finite element model of the helicopter engine casing, then obtains the vibration energy flow amplitude at each position on the casing by calculating the vibration energy flow component and its vector at each position on the casing surface, draws a three-dimensional diagram of the vibration energy flow based on the vibration energy flow amplitude, realizes the visualization of the distribution of the vibration energy flow in the casing structure, can accurately analyze the concentrated area of ​​the vibration energy flow in the casing, and finally adjusts the engine hanging point position according to the distribution of the vibration energy flow to reduce the amplitude of the vibration energy flow in the specific area, thereby reducing the vibration amplitude. The method of the present invention can avoid structural damage caused by excessive concentration of vibration energy flow in specific parts of the casing, and has important theoretical significance and engineering value for explaining the mechanism of vibration damage to the structure, optimizing the structure and controlling the vibration energy flow of the structure to improve the vibration reduction effect. At the same time, the method of the present invention can also provide a reference for vibration analysis and vibration reduction of similar structures in other fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a flow chart of a helicopter engine casing vibration reduction method based on vibration energy flow control of the present invention;

[0018] Figure 2 It is a schematic diagram of the helicopter engine casing structure of the present invention;

[0019] Figure 3Schematic diagram for adjusting the position of the front casing engine mounting points on four surfaces;

[0020] Figure 4 A three-dimensional diagram for adjusting the amplitude of vibration energy flow on each surface of the front casing;

[0021] Figure 5 To adjust the vibration amplitude diagram on each surface of the front receiver;

[0022] Figure 6 A schematic diagram of the positions of the engine hanging points on four surfaces of the rear casing after adjustment of the present invention;

[0023] Figure 7 A three-dimensional diagram of the amplitude of the vibration energy flow on each surface of the casing after adjustment of the present invention;

[0024] Figure 8 The vibration amplitude diagram on each surface of the casing after adjustment of the present invention. DETAILED DESCRIPTION

[0025] Specific implementation method 1: Combination Figure 1 and Figure 2 The present embodiment describes a helicopter engine casing vibration reduction method based on vibration energy flow control, and the method specifically comprises the following steps:

[0026] Step 1: construct a finite element model of a helicopter engine casing, set the structural damping parameters and boundary conditions of the finite element model, and then correct the damping parameters of the finite element model through modal analysis to obtain a corrected casing finite element model;

[0027] like Figure 3 As shown, the engine hanging point position on the casing finite element model after random initialization correction;

[0028] Step 2, select the analysis frequency ω, apply an excitation load to the engine hanging point (the excitation load value can be randomly selected, and the excitation load is a sinusoidal surface load perpendicular to the casing wall at the engine hanging point), and then perform a steady-state dynamic analysis on the modified casing finite element model to obtain the displacement of each node in each unit. It should be noted that the unit here is the unit obtained by using the built-in meshing module in ANSYS when establishing the finite element model;

[0029] Steady-state dynamic analysis can accurately simulate the effect of the helicopter engine on the casing during operation, which can better assist in the analysis of the casing vibration energy flow.

[0030] Step 3, curve fitting is performed on the displacement of each node in each unit obtained in step 2 to obtain the displacement of each position on the casing surface (i.e., the displacement of each node of the new grid after each surface is re-meshed), and the internal force of each position is calculated based on the displacement of each position;

[0031] Step 4: For each position on the casing surface, the vibration energy flow component in the x-axis direction and the vibration energy flow component in the y-axis direction are calculated according to the displacement and the internal force, and then the magnitude of the vibration energy flow vector at each position is calculated according to the vibration energy flow component, so as to obtain the vibration energy flow distribution on each wall surface of the casing;

[0032] Step 5, determining the vibration energy flow concentration area according to the vibration energy flow distribution on each wall surface of the casing, and then adjusting the position distribution of the engine hanging point according to the vibration energy flow concentration area;

[0033] Step 6, using the engine hanging point position adjusted in step 5, return to step 2 and end when there is no vibration energy flow concentration area on each wall surface of the casing.

[0034] The method of the present invention includes constructing a finite element model of a helicopter engine casing, and setting the damping and boundary conditions of the finite element model; determining the analysis frequency, applying an excitation load to the engine hanging point on the casing finite element model, and obtaining the node displacement; obtaining the displacement of each position on the casing surface by curve fitting the node displacement, and calculating the internal force of each position in combination with the obtained displacement; obtaining the vibration energy flow component and the vibration energy flow vector size of each position on the casing surface in the x and y directions in combination with the displacement and the internal force, and then obtaining the distribution of the vibration energy flow on the casing surface; adjusting the engine hanging point near the vibration energy flow concentration position according to the distribution of the vibration energy flow to achieve the effect of reducing the vibration energy flow size in the concentrated area. The present invention realizes the control of the vibration energy flow of the helicopter engine casing, thereby preventing structural damage caused by excessive concentration of the vibration energy flow, so as to achieve the vibration reduction effect.

[0035] Specific implementation method 2: This implementation method is different from the specific implementation method 1 in that the specific process of step 1 is as follows:

[0036] Step 11, constructing a finite element model of the helicopter engine casing to be analyzed (wherein the casing is made of uniform elastic material);

[0037] Step 12: assign structural damping parameters and boundary conditions to the constructed finite element model;

[0038] Step 13: Perform modal analysis on the finite element model after assigning structural damping parameters and boundary conditions to obtain the natural frequency f of the casing. 1 , the natural frequency obtained by modal analysis of the helicopter engine casing to be analyzed is recorded as f 2 ;

[0039] f 1 With f 2 A comparison is made, and then the structural damping parameters of the helicopter engine casing finite element model are corrected according to the comparison results, and finally a corrected helicopter engine casing finite element model is obtained.

[0040] The other steps and parameters are the same as those in the first embodiment.

[0041] It should be noted that the specific process of correcting the structural damping parameters according to the comparison results is as follows: first, compare f 1 With f 2 , if f 1 With f 2 If the absolute value of the difference between the two exceeds the set threshold, the structural damping parameters of the finite element model are randomly adjusted in one direction, and the natural frequency and f after the structural damping parameters are adjusted are calculated. 2 If the absolute value of the difference becomes larger, the structural damping parameters of the finite element model are fine-tuned in the opposite direction of the first adjustment. After each fine-tuning, the natural frequency corresponding to the finite element model is compared with the natural frequency of the actual helicopter engine casing to be analyzed. The adjustment is stopped when the natural frequency of the finite element model meets the requirements, and the final corrected finite element model is obtained. By comparing and correcting the numerical model of the casing structure to be analyzed with the experiment, the accuracy of the analysis results can be guaranteed.

[0042] Specific implementation method three: This implementation method is different from specific implementation method one or two in that the structural damping parameters in step 12 include constant damping, material damping and Rayleigh damping.

[0043] The other steps and parameters are the same as those in the first or second embodiment.

[0044] Specific implementation method 4: This implementation method is different from the specific implementation methods 1 to 3 in that the specific process of step 3 is as follows:

[0045] Step 31, re-gridding the four walls of the casing respectively;

[0046] Step 32, performing curve fitting on the displacement of each node in each unit obtained in step 2, and obtaining the displacement of each node of each grid on each wall surface according to the fitting curve, wherein the displacement on each node includes translation displacement and rotation angle;

[0047] The curve fitting process here needs to be performed for each wall separately;

[0048] Step 33: Calculate the internal force of each node based on the displacement at each node.

[0049] The other steps and parameters are the same as those in Specific Embodiments 1 to 3.

[0050] Since the built-in meshing method in ANSYS was used to establish the finite element model, the divided units and nodes are not regular, so it is necessary to divide the surface quadrilateral mesh again to facilitate the subsequent accurate description of the distribution of the amplitude of the vibration energy flow in the casing structure.

[0051] Specific implementation method five: This implementation method is different from specific implementation methods one to four in that the internal force of each node includes axial force, tangential force, shear force and bending moment.

[0052] The other steps and parameters are the same as those in Specific Embodiments 1 to 4.

[0053] Specific implementation method 6: This implementation method is different from the specific implementation methods 1 to 5 in that the specific process of step 4 is as follows:

[0054] Take any position on the receiver surface as an example

[0055] Step 41, calculate the vibration energy flow component in the x-axis direction and the vibration energy flow component in the y-axis direction:

[0056]

[0057] in, represents the longitudinal wave component of the vibration energy flow in the x-axis direction, represents the longitudinal wave component of the vibration energy flow in the y-axis direction, represents the shear wave component of the vibration energy flow in the x-axis direction, represents the shear wave component of the vibration energy flow in the y-axis direction, represents the bending wave component of the vibration energy flow in the x-axis direction, represents the bending wave component of the vibration energy flow in the y-axis direction, represents the torsional wave component of the vibration energy flow in the x-axis direction, It represents the torsional wave component of the vibration energy flow in the y-axis direction, I x represents the vibration energy flow component in the x-axis direction, I y Represents the vibration energy flow component in the y-axis direction;

[0058] Step 42: Use I x and I y Calculate the magnitude of the vibration energy flow vector.

[0059] The other steps and parameters are the same as those in Specific Implementation Methods 1 to 5.

[0060] The process of this embodiment is performed for each node position on the wall surface to obtain the magnitude of the vibration energy flow vector at each node position.

[0061] By calculating the various components of the vibration energy flow of the casing structure, it is possible to analyze the composition and contribution of the structural vibration wave and clarify the vibration wave components that dominate the structural vibration, which is of great significance for revealing the vibration mechanism.

[0062] Specific implementation method 7: This implementation method is different from any one of the specific implementation methods 1 to 6 in that the longitudinal wave component and They are:

[0063]

[0064] Among them, Im[·] represents the imaginary part of the real number, N x It represents the axial force in the x direction per unit width of the wall, N y represents the axial force in the y direction per unit width of the wall, u * represents the complex conjugate of the translational displacement in the x direction, v * represents the complex conjugate of the translational displacement in the y direction;

[0065] Shear wave component and They are:

[0066]

[0067] Among them, N xy It represents the tangential force in the x direction per unit width of the wall, N yx represents the tangential force in the y direction per unit width of the wall;

[0068] Shear wave component and They are:

[0069]

[0070] Among them, w * represents the complex conjugate of the translational displacement in the z direction, Q x represents the shear force in the x direction per unit width of the wall, Q y They represent the shear force in the y direction per unit width of the wall, M x represents the bending moment in the x direction per unit width of the wall, M y represents the bending moment in the y direction per unit width of the wall, represents the complex conjugate of the rotation angle around the x direction, represents the complex conjugate of the rotation angle around the y direction;

[0071] Shear wave component and They are:

[0072]

[0073] Among them, M xy It is the torque in the x direction per unit width of the wall, M yx It is the torque in the y direction per unit width of the wall.

[0074] The other steps and parameters are the same as those in Specific Embodiments 1 to 6.

[0075] Specific implementation eight: This implementation is different from any one of specific implementations one to seven in that the specific process of step 42 is as follows:

[0076]

[0077] Among them, P is the magnitude of the vibration energy flow vector.

[0078] The other steps and parameters are the same as those in Specific Embodiments 1 to 7.

[0079] Specific implementation method 9: This implementation method is different from specific implementation methods 1 to 8 in that the specific process of step 5 is as follows:

[0080] Step 51, drawing a three-dimensional image (using Origin software) according to the distribution of vibration energy flow on each wall surface of the casing, and determining the vibration energy flow concentration area on each wall surface through the three-dimensional image;

[0081] It should be noted that the method for determining the vibration energy flow concentration area in the present invention is: for any wall surface, after calculating the vibration energy flow vector size of each node on the wall surface, the vibration energy flow vector size of each node on the wall surface is compared with the vibration energy flow threshold of the wall surface, and the area composed of nodes with vibration energy flow vector values ​​greater than the threshold is taken as the vibration energy flow concentration area; Figure 3 For example, the vibration energy flow thresholds of the four walls are set to 1.48×10 -3 , 9.5×10 -2 , 6.82×10 -3 and 3.2×10 -2 , the specific threshold can be set according to the actual situation.

[0082] Step 52: Adjust the position distribution of the engine attachment points according to the concentrated area of ​​vibration energy flow, and adjust the attachment points of the rear casing engine as follows: Figure 6 shown.

[0083] According to the magnitude of the vibration energy flow vector of each node in the vibration energy flow concentration area, a suitable number of engine hanging points can be selected for the vibration energy flow concentration area, and the engine hanging points can be set in the vibration energy flow concentration area. The specific position and number of the engine hanging points can be designed based on experience.

[0084] The other steps and parameters are the same as those in Specific Embodiments 1 to 8.

[0085] According to the distribution of vibration energy flow, the position of the engine hanging point is adjusted to reduce the amplitude of the vibration energy flow in a specific area, so as to avoid structural damage caused by excessive concentration of vibration energy flow in a specific part of the casing. This has important theoretical significance and engineering value for explaining the mechanism of vibration damage to the structure, optimizing the structure and controlling the vibration energy flow of the structure to achieve the purpose of vibration reduction.

[0086] Example

[0087] This embodiment proposes a helicopter engine casing vibration reduction method based on vibration energy flow control, and the method specifically includes the following steps:

[0088] Step 1: construct a finite element model of a helicopter engine casing, set the structural damping parameters and boundary conditions of the finite element model, and then correct the damping parameters of the finite element model through modal analysis to obtain a corrected casing finite element model;

[0089] The specific process of step 1 is:

[0090] Step 11, constructing a finite element model of the helicopter engine casing to be analyzed (wherein the casing is made of uniform elastic material);

[0091] Step 12: assigning structural damping parameters and boundary conditions to the constructed finite element model, wherein the structural damping parameters include constant damping, material damping and Rayleigh damping;

[0092] Step 13: Perform modal analysis on the finite element model after assigning structural damping parameters and boundary conditions to obtain the natural frequency f of the casing. 1 , the natural frequency obtained by modal analysis of the helicopter engine casing to be analyzed is recorded as f 2 ;

[0093] f 1 With f 2 A comparison is made, and then the structural damping parameters of the helicopter engine casing finite element model are corrected according to the comparison results, and finally a corrected helicopter engine casing finite element model is obtained.

[0094] It should be noted that the specific process of correcting the structural damping parameters according to the comparison results is:

[0095] First, compare f 1 With f 2 , if f 1 With f 2 If the absolute value of the difference between the two exceeds the set threshold, the structural damping parameters of the finite element model are randomly adjusted in one direction, and the natural frequency and f after the structural damping parameters are adjusted are calculated.2 If the absolute value of the difference becomes larger, the structural damping parameters of the finite element model are fine-tuned in the opposite direction of the first adjustment. After each fine-tuning, the natural frequency corresponding to the finite element model is compared with the natural frequency of the actual helicopter engine casing to be analyzed. The adjustment is stopped until the natural frequency of the finite element model meets the requirements, and the final corrected finite element model is obtained.

[0096] like Figure 3 As shown, the engine hanging point position on the casing finite element model after random initialization correction;

[0097] Step 2, select the analysis frequency ω, apply an excitation load to the engine hanging point (the excitation load value can be randomly selected, and the excitation load is a sinusoidal surface load perpendicular to the casing wall at the engine hanging point), and then perform a steady-state dynamic analysis on the modified casing finite element model to obtain the displacement of each node in each unit. It should be noted that the unit here is the unit obtained by using the built-in meshing module in ANSYS when establishing the finite element model;

[0098] Step 3, curve fitting is performed on the displacement of each node in each unit obtained in step 2 to obtain the displacement of each position on the casing surface, and the internal force of each position is calculated based on the displacement of each position;

[0099] The specific process of step 3 is:

[0100] Step 31, re-gridding the four walls of the casing respectively;

[0101] Step 32, performing curve fitting on the displacement of each node in each unit obtained in step 2, and obtaining the displacement of each node of each grid on each wall surface according to the fitting curve, wherein the displacement on each node includes translation displacement and rotation angle;

[0102] The curve fitting process here needs to be performed for each wall separately;

[0103] Step 33: Calculate the internal force of each node according to the displacement at each node. The internal force of each node includes axial force, tangential force, shear force and bending moment.

[0104] Step 4: For each position on the casing surface, the vibration energy flow component in the x-axis direction and the vibration energy flow component in the y-axis direction are calculated according to the displacement and the internal force, and then the magnitude of the vibration energy flow vector at each position is calculated according to the vibration energy flow component, so as to obtain the vibration energy flow distribution on each wall surface of the casing;

[0105] The specific process of step 4 is:

[0106] Take any position on the receiver surface as an example

[0107] Step 41, calculate the vibration energy flow component in the x-axis direction and the vibration energy flow component in the y-axis direction:

[0108]

[0109] in, represents the longitudinal wave component of the vibration energy flow in the x-axis direction, represents the longitudinal wave component of the vibration energy flow in the y-axis direction, represents the shear wave component of the vibration energy flow in the x-axis direction, represents the shear wave component of the vibration energy flow in the y-axis direction, represents the bending wave component of the vibration energy flow in the x-axis direction, represents the bending wave component of the vibration energy flow in the y-axis direction, represents the torsional wave component of the vibration energy flow in the x-axis direction, It represents the torsional wave component of the vibration energy flow in the y-axis direction, I x represents the vibration energy flow component in the x-axis direction, I y Represents the vibration energy flow component in the y-axis direction;

[0110] It should be noted that the x-axis direction, y-axis direction and z-axis direction in the present invention are respectively the x-axis direction, y-axis direction and z-axis direction of a three-dimensional rectangular coordinate system.

[0111] The longitudinal wave component and They are:

[0112]

[0113] Among them, Im[·] represents the imaginary part of the real number, N x It represents the axial force in the x direction per unit width of the wall, N y represents the axial force in the y direction per unit width of the wall, u * represents the complex conjugate of the translational displacement in the x direction, v * represents the complex conjugate of the translational displacement in the y direction;

[0114] Shear wave component and They are:

[0115]

[0116] Among them, N xy It represents the tangential force in the x direction per unit width of the wall, N yx represents the tangential force in the y direction per unit width of the wall;

[0117] Shear wave component and They are:

[0118]

[0119] Among them, w * represents the complex conjugate of the translational displacement in the z direction, Q x represents the shear force in the x direction per unit width of the wall, Q y They represent the shear force in the y direction per unit width of the wall, M x represents the bending moment in the x direction per unit width of the wall, M y represents the bending moment in the y direction per unit width of the wall, represents the complex conjugate of the rotation angle around the x direction, represents the complex conjugate of the rotation angle around the y direction;

[0120] Shear wave component and They are:

[0121]

[0122] Among them, M xy It is the torque in the x direction per unit width of the wall, M yx It is the torque in the y direction per unit width of the wall.

[0123] Step 42: Use I x and I y Calculate the magnitude of vibration energy flow vector;

[0124]

[0125] Among them, P is the magnitude of the vibration energy flow vector.

[0126] Step 5, determining the vibration energy flow concentration area according to the vibration energy flow distribution on each wall surface of the casing, and then adjusting the position distribution of the engine hanging point according to the vibration energy flow concentration area;

[0127] The specific process of step 5 is:

[0128] Step 51, drawing a three-dimensional image (using Origin software) according to the distribution of vibration energy flow on each wall surface of the casing, and determining the vibration energy flow concentration area on each wall surface through the three-dimensional image;

[0129] It should be noted that the method for determining the vibration energy flow concentration area in the present invention is: for any wall surface, after calculating the vibration energy flow vector size of each node on the wall surface, the vibration energy flow vector size of each node on the wall surface is compared with the vibration energy flow threshold of the wall surface, and the area composed of nodes with vibration energy flow vector values ​​greater than the threshold is taken as the vibration energy flow concentration area; Figure 3For example, the vibration energy flow thresholds of the four walls are set to 1.48×10 -3 , 9.5×10 -2 , 6.82×10 -3 and 3.2×10 -2 , the specific threshold can be set according to the actual situation.

[0130] Step 52: Adjust the position distribution of the engine attachment points according to the concentrated area of ​​vibration energy flow, and adjust the attachment points of the rear casing engine as follows: Figure 6 shown.

[0131] According to the magnitude of the vibration energy flow vector of each node in the vibration energy flow concentration area, a suitable number of engine hanging points can be selected for the vibration energy flow concentration area, and the engine hanging points can be set in the vibration energy flow concentration area. The specific position and number of the engine hanging points can be designed based on experience.

[0132] Step 6, using the engine hanging point position adjusted in step 5, return to step 2 and end when there is no vibration energy flow concentration area on each wall surface of the casing.

[0133] Combination Figure 4 and Figure 7 It can be seen that the vibration energy flow amplitude on the casing surface was relatively large, which was significantly reduced after adjusting the engine hanging point. Figure 5 and Figure 8 It can be seen that after adjustment, the amplitude of each surface of the receiver has decreased, achieving the effect of vibration reduction.

[0134] In summary, the method of the present invention can avoid structural damage caused by excessive concentration of vibration energy flow in specific parts of the casing. It has important theoretical significance and engineering value for explaining the mechanism of vibration damage to the structure, optimizing the structure and controlling the vibration energy flow of the structure to achieve the purpose of vibration reduction. At the same time, the present invention can also provide a reference for vibration analysis and vibration reduction of similar structures in other fields.

[0135] The above calculation examples of the present invention are only used to explain the calculation model and calculation process of the present invention in detail, and are not intended to limit the implementation methods of the present invention. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is impossible to list all the implementation methods here. All obvious changes or modifications derived from the technical solution of the present invention are still within the scope of protection of the present invention.

Claims

1. A helicopter engine casing vibration reduction method based on vibration energy flow control, characterized in that: The method specifically comprises the following steps: Step 1: construct a finite element model of a helicopter engine casing, set the structural damping parameters and boundary conditions of the finite element model, and then correct the damping parameters of the finite element model through modal analysis to obtain a corrected casing finite element model; The position of the engine attachment point on the finite element model of the casing after random initialization correction; Step 2: Select the analysis frequency ω, and after applying the excitation load to the engine attachment point, perform steady-state dynamic analysis on the modified casing finite element model to obtain the displacement of each node in each unit; Step 3, curve fitting is performed on the displacement of each node in each unit obtained in step 2 to obtain the displacement of each position on the casing surface, and the internal force of each position is calculated based on the displacement of each position; Step 4: For each position on the casing surface, the vibration energy flow component in the x-axis direction and the vibration energy flow component in the y-axis direction are calculated according to the displacement and the internal force, and then the magnitude of the vibration energy flow vector at each position is calculated according to the vibration energy flow component, so as to obtain the vibration energy flow distribution on each wall surface of the casing; Step 5, determining the vibration energy flow concentration area according to the vibration energy flow distribution on each wall surface of the casing, and then adjusting the position distribution of the engine hanging point according to the vibration energy flow concentration area; Step 6, using the engine hanging point position adjusted in step 5, return to step 2 and end when there is no vibration energy flow concentration area on each wall surface of the casing.

2. A helicopter engine casing vibration reduction method based on vibration energy flow control according to claim 1, characterized in that: The specific process of step 1 is as follows: Step 11, constructing a finite element model of the helicopter engine casing to be analyzed; Step 12: assign structural damping parameters and boundary conditions to the constructed finite element model; Step 13, performing modal analysis on the finite element model after assigning structural damping parameters and boundary conditions, and obtaining the natural frequency f1 of the casing, and directly performing modal analysis on the helicopter engine casing to be analyzed to obtain the natural frequency f2; f1 is compared with f2, and the structural damping parameters of the helicopter engine casing finite element model are corrected according to the comparison results, and finally the corrected helicopter engine casing finite element model is obtained.

3. A helicopter engine casing vibration reduction method based on vibration energy flow control according to claim 2, characterized in that: The structural damping parameters in step 12 include constant damping, material damping and Rayleigh damping.

4. A helicopter engine case vibration reduction method based on vibration energy flow control according to claim 3, characterized in that: The specific process of step 3 is as follows: Step 31, re-gridding the four walls of the casing respectively; Step 32, performing curve fitting on the displacement of each node in each unit obtained in step 2, and obtaining the displacement of each node of each grid on each wall surface according to the fitting curve, wherein the displacement on each node includes translation displacement and rotation angle; Step 33: Calculate the internal force of each node based on the displacement at each node.

5. A helicopter engine case vibration reduction method based on vibration energy flow control according to claim 4, characterized in that: The internal forces of each node include axial force, tangential force, shear force and bending moment.

6. A helicopter engine case vibration reduction method based on vibration energy flow control according to claim 5, characterized in that: The specific process of step 4 is as follows: Take any position on the receiver surface as an example Step 41, calculate the vibration energy flow component in the x-axis direction and the vibration energy flow component in the y-axis direction: in, represents the longitudinal wave component of the vibration energy flow in the x-axis direction, represents the longitudinal wave component of the vibration energy flow in the y-axis direction, represents the shear wave component of the vibration energy flow in the x-axis direction, represents the shear wave component of the vibration energy flow in the y-axis direction, represents the bending wave component of the vibration energy flow in the x-axis direction, represents the bending wave component of the vibration energy flow in the y-axis direction, represents the torsional wave component of the vibration energy flow in the x-axis direction, It represents the torsional wave component of the vibration energy flow in the y-axis direction, I x represents the vibration energy flow component in the x-axis direction, I y Represents the vibration energy flow component in the y-axis direction; Step 42: Use I x and I y Calculate the magnitude of the vibration energy flow vector.

7. A helicopter engine case vibration reduction method based on vibration energy flow control according to claim 6, characterized in that: The longitudinal wave component and They are: Among them, Im[·] represents the imaginary part of the real number, N x It represents the axial force in the x direction per unit width of the wall, N y represents the axial force in the y direction per unit width of the wall, u * represents the complex conjugate of the translational displacement in the x direction, v * represents the complex conjugate of the translational displacement in the y direction; Shear wave component and They are: Among them, N xy It represents the tangential force in the x direction per unit width of the wall, N yx represents the tangential force in the y direction per unit width of the wall; Shear wave component and They are: Among them, w * represents the complex conjugate of the translational displacement in the z direction, Q x represents the shear force in the x direction per unit width of the wall, Q y They represent the shear force in the y direction per unit width of the wall, M x represents the bending moment in the x direction per unit width of the wall, M y represents the bending moment in the y direction per unit width of the wall, represents the complex conjugate of the rotation angle around the x direction, represents the complex conjugate of the rotation angle around the y direction; Shear wave component and They are: Among them, M xy It is the torque in the x direction per unit width of the wall, M yx It is the torque in the y direction per unit width of the wall.

8. A helicopter engine casing vibration reduction method based on vibration energy flow control according to claim 7, characterized in that: The specific process of step 42 is as follows: Among them, P is the magnitude of the vibration energy flow vector.

9. A helicopter engine case vibration reduction method based on vibration energy flow control according to claim 8, characterized in that: The specific process of step 5 is as follows: Step 51, drawing a three-dimensional image according to the distribution of vibration energy flow on each wall surface of the casing, and determining the vibration energy flow concentration area on each wall surface through the three-dimensional image; Step 52: Adjust the position distribution of the engine attachment points according to the vibration energy flow concentration area.

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