Nacelle wind tunnel test model for spin flutter analysis and simulation verification method

Abstract

The present application belongs to the field of wind tunnel test, and relates to a nacelle wind tunnel test model for rotary vibration analysis and a simulation verification method. The wind tunnel test model is designed according to a helicopter nacelle, and comprises a fuselage model, a wing model, a nacelle model, a rotor model, a nacelle-rotor connecting model and a nacelle-wing connecting model which are rigidly installed on a wind tunnel wall. The wing model is installed on the fuselage model. The nacelle-rotor connecting model is used to connect the rotor model and the nacelle model. The nacelle-rotor connecting model is arranged inside the nacelle model and is integrally arranged or rigidly connected with the nacelle model. The nacelle-wing connecting model is connected with the wing model through bolts. Two bearing seats for assembling rotor shafts are arranged on the nacelle-rotor connecting model, and a mass block is arranged between the two bearing seats.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of wind tunnel test, and relates to a nacelle wind tunnel test model for rotation flutter analysis and a simulation verification method. BACKGROUND

[0002] The tilt-rotor aircraft is composed of a body, a wing, a nacelle and a rotor, the rotor is installed on the nacelle at both ends of the wing, the nacelle rotates around the tilt hinge to realize dynamic conversion of the tilt-rotor aircraft between the helicopter, the fixed-wing aircraft and the tilt transition flight mode. There is an unignorable rotation flutter stability problem between the rotor installed on the nacelle, the nacelle and the elastic wing of the tilt-rotor aircraft, once the rotation flutter instability occurs, it seriously affects the safety of the tilt-rotor aircraft. At present, there is no type experience and wind tunnel test experience on the rotation flutter stability analysis of the rotor-nacelle-wing coupling system of the tilt-rotor aircraft in China.

[0003] The nacelle, as the supporting structure of the rotor, directly affects the rotation flutter stability of the rotor-nacelle-wing coupling system of the tilt-rotor aircraft due to the factors such as the connection stiffness and mass. The rotor, the main speed reducer, the engine, the tilt mechanism and other large mass equipment are installed in the nacelle at the end of the wing, which together constitute the core tilt part of the tilt-rotor aircraft. However, many large mass equipment may change the weight and center of gravity of the nacelle due to the design, processing or overall assembly of the equipment itself in various links such as scheme, design, processing, delivery and overall assembly, which directly affects the dynamic characteristics of the wing and further affects the rotation flutter stability of the rotor-nacelle-wing coupling system. Therefore, it is necessary to analyze the influence of the connection stiffness, weight and center of gravity of the nacelle on the rotation flutter stability of the tilt-rotor aircraft in the early stage of type development, and to ensure the flight safety of the type through strict verification research. SUMMARY

[0004] The present application belongs to the field of wind tunnel test, and relates to a nacelle wind tunnel test model for rotation flutter analysis and a simulation verification method.

[0005] Technical scheme:

[0006] In a first aspect, a nacelle wind tunnel test model for rotation flutter analysis is provided, according to the design of a helicopter nacelle, comprising:

[0007] A fuselage model, a wing model, a nacelle model, a rotor model, a nacelle-rotor connection model and a nacelle-wing connection model are rigidly installed on the wall of the wind tunnel.

[0008] The wing model is installed on the fuselage model, and the nacelle-rotor connection model is used to connect the rotor model and the nacelle model.

[0009] The nacelle model is internally provided with a nacelle-rotor connecting model, which is integrally arranged or rigidly connected with the nacelle model; and the nacelle-wing connecting model is connected with the wing model through bolts.

[0010] Two bearing seats for assembling rotor shafts are arranged on the nacelle-rotor connecting model, and a mass block is arranged between the two bearing seats.

[0011] Further, the gravity center of the mass block is designed to be adjustable in the axial and lateral directions, the gravity heading parameter of the nacelle is changed by moving the mass block in the axial direction of the rotor shaft between the two bearing seats, and the gravity lateral parameter of the adjustable nacelle is changed by adjusting the lateral gravity center of the mass block.

[0012] Further, the mass block is designed to be adjustable in weight or a combination of multiple mass blocks, and the weight parameter of the adjustable nacelle is changed by changing the weight of the mass block.

[0013] In a second aspect, a simulation verification method for whirl flutter analysis is provided, comprising:

[0014] Based on the adjustable requirements of key parameters such as the connecting stiffness of the nacelle and the wing, the weight and gravity center of the nacelle, the short nacelle wind tunnel test model for whirl flutter analysis is designed;

[0015] Based on the short nacelle wind tunnel test model for whirl flutter analysis, a whirl flutter simulation analysis model of the wind tunnel test model is established, and whirl flutter simulation analysis of the short nacelle wind tunnel test model for whirl flutter analysis is carried out;

[0016] Based on the short nacelle wind tunnel test model for whirl flutter analysis and the simulation analysis, the wind tunnel test working conditions are determined, the whirl flutter stability of the wind tunnel test model under different working conditions is determined through wind tunnel blowing test;

[0017] The whirl flutter stability of the wind tunnel test model under different working conditions and the simulation analysis results are compared, and the whirl flutter simulation analysis method of the rotor-nacelle-wing coupled system wind tunnel test model is verified;

[0018] Based on the whirl flutter simulation analysis method, a whirl flutter simulation analysis model of the rotor-nacelle-wing coupled system of the tiltrotor prototype is established, and whirl flutter stability analysis is carried out.

[0019] Further, the method further comprises:

[0020] The whirl flutter simulation analysis model of the rotor-nacelle-wing coupled system of the tiltrotor prototype is used to study the whirl flutter stability of the tiltrotor under different nacelle and wing connecting stiffness, nacelle weight, and gravity center.

[0021] Further, based on the nacelle wind tunnel test model for whirl flutter analysis, a whirl flutter simulation analysis model of the wind tunnel test model is established, and whirl flutter simulation analysis of the nacelle wind tunnel test model for whirl flutter analysis is carried out, including:

[0022] The whirl flutter simulation analysis model of the nacelle wind tunnel test model for whirl flutter analysis is established, and simulation analysis models of the fuselage model, wing model, nacelle model and rotor model of the wind tunnel test model are respectively established;

[0023] The multi-point constraint element RBE3 is used to simulate the connection between the mass point and the structure, the solid element is used to simulate the nacelle-wing connection model, and the multi-point constraint element RBE2 is used to simulate the bolt rigid connection. The adjustable nacelle finite element simulation analysis model is established, the element properties of the multi-point constraint element RBE3 of the simulated mass block are adjusted, the influence of the mass block on the dynamic characteristics of the test model is studied based on the modal analysis method, and the corresponding nacelle weight, wind tunnel test working condition of the center of gravity are determined;

[0024] The spring element is used to simulate the nacelle-wing connection stiffness, the spring element properties are adjusted, the influence of the nacelle-wing connection stiffness on the dynamic characteristics of the test model is studied based on the modal analysis method, and the corresponding nacelle-wing connection stiffness wind tunnel test working condition is determined;

[0025] The wing modal analysis results are input into the whirl flutter simulation analysis model, and the influence of the nacelle-wing connection stiffness, nacelle weight, center of gravity and other parameters on the whirl flutter stability of the test model is studied respectively, so as to be compared with the wind tunnel test data.

[0026] Further, based on the whirl flutter simulation analysis method, a rotor-nacelle-wing coupling system whirl flutter simulation analysis model of the tiltrotor prototype is established, and whirl flutter stability analysis is carried out, including:

[0027] Based on the size of the tiltrotor prototype and the aeroelasticity analysis method, the rotor model, wing model and aerodynamic load analysis model of the prototype are respectively established, and the rotor-nacelle-wing coupling system whirl flutter simulation analysis model of the prototype is constituted;

[0028] The whirl flutter stability of the rotor-nacelle-wing coupling system of the tiltrotor is solved by using the flutter analysis module to analyze the whirl stability of the tiltrotor;

[0029] The whirl flutter stability of the rotor-nacelle-wing coupling system of the tiltrotor is determined.

[0030] Further, the point where the modal damping ratio is equal to 0 is a critical point, the tilt rotor aircraft is in a whirling flutter critical stable state, and the corresponding forward flight speed is a whirling flutter critical speed condition of the tilt rotor aircraft, when the modal damping ratio is positive, the analyzed tilt rotor aircraft does not have the risk of whirling flutter; when the modal damping ratio is negative, the analyzed tilt rotor aircraft has the risk of whirling flutter.

[0031] Beneficial effects: The short nacelle design method for whirl flutter wind tunnel test adopted by the present application is in a blank field, a kind of adjustable short nacelle design method for whirl flutter wind tunnel test is invented based on whirl flutter stability problem of rotor-nacelle-wing coupling system and wind tunnel test thereof, for studying the influence of different short nacelle support stiffness on whirl flutter coupling characteristics between rotor and wing in wind tunnel test, avoiding the risk of increasing subsequent design state, effectively guiding the design in initial development stage, and filling the blank of wind tunnel test research in the field. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 It is a schematic diagram for the design of short nacelle wind tunnel test model.

[0033] Figure 2 It is a graph showing that damping varies with forward flight speed.

[0034] Figure 3 It is a flow chart of the simulation verification method for whirl flutter analysis. DETAILED DESCRIPTION

[0035] The present application provides a simulation verification method for whirl flutter analysis, as shown in Figure 3 , comprising:

[0036] Step 1: based on the adjustable requirements of key parameters such as short nacelle and wing connection stiffness, short nacelle weight, center of gravity, etc., carry out rotor-nacelle-wing coupling system wind tunnel test model design;

[0037] a) according to the size and dynamics scaling criteria of the tilt rotor aircraft prototype, carry out rotor-nacelle-wing coupling system wind tunnel test model suitable for tilt rotor aircraft, design the weight, center of gravity of the short nacelle of the test model, and the short nacelle and wing connection stiffness as adjustable structure;

[0038] b) the rotor-nacelle-wing coupling system wind tunnel test model includes a fuselage model, a wing model, a short nacelle model, a rotor model, a short nacelle rotor connection model and a short nacelle wing connection model rigidly mounted on the wall of the wind tunnel;

[0039] c) design a short nacelle rotor connection model inside the short nacelle, the short nacelle rotor connection model is integrated with the short nacelle or rigidly connected, and is fixedly installed inside the short nacelle;

[0040] d) Design two bearing seats on the nacelle-rotor connection model to assemble the rotor shaft, and install the mass block between the two bearing seats;

[0041] e) Design the weight of the mass block as an adjustable weight or a combination of multiple mass blocks, and change the weight of the mass block to change the weight parameters of the adjustable nacelle;

[0042] f) Design the center of gravity of the mass block to be adjustable in the axial and lateral directions, move the mass block along the axial direction of the rotor shaft between the two bearing seats to change the heading direction of the center of gravity of the nacelle, and adjust the lateral center of gravity of the mass block itself to change the lateral direction of the center of gravity of the adjustable nacelle;

[0043] g) Change the weight and center of gravity of the mass block to change the weight and center of gravity parameters of the adjustable nacelle;

[0044] h) Design the nacelle-wing connection model as one or more connection members with adjustable stiffness, and connect the nacelle-wing connection model to the wing through bolts;

[0045] i) Change the connection stiffness between the nacelle-wing connection model and the wing by adjusting the stiffness of the nacelle-wing connection model, the material or number of bolts, to change the connection stiffness between the nacelle and the wing.

[0046] Second step: Based on the designed tilt-rotor aircraft whirl flutter wind tunnel test model, establish a whirl flutter simulation analysis model of the wind tunnel test model, and carry out simulation analysis of the rotor-nacelle-wing coupled system wind tunnel test model;

[0047] a) Establish a whirl flutter simulation analysis model of the rotor-nacelle-wing coupled system wind tunnel test model, and establish simulation analysis models of the fuselage model, wing model, nacelle model, and rotor model of the wind tunnel test model respectively;

[0048] b) Simulate the connection between the mass point and the structure using multi-point constraint element RBE3, simulate the nacelle-wing connection model using solid elements, simulate the bolt rigid connection using multi-point constraint element RBE2, establish an adjustable nacelle finite element simulation analysis model, adjust the element properties of the multi-point constraint element RBE3 of the simulated mass block, and based on the modal analysis method, study the influence of the mass block on the dynamic characteristics of the test model, and determine the corresponding nacelle weight and center of gravity wind tunnel test working condition;

[0049] c) Simulate the nacelle-wing connection stiffness by spring elements, adjust the spring element properties, based on the modal analysis method, study the influence of the nacelle-wing connection stiffness on the dynamic characteristics of the test model, and determine the corresponding nacelle-wing connection stiffness wind tunnel test working condition;

[0050] d) input the wing modal analysis results into the spin flutter simulation analysis model, and respectively study the influence of the short nacelle and wing connection stiffness, short nacelle weight, center of gravity and other parameters on the spin flutter stability of the test model, so as to be compared with the wind tunnel test data.

[0051] Step 3: Based on the designed tilt-rotor aircraft spin flutter wind tunnel test model and the determined wind tunnel test conditions of the simulation analysis, carry out wind tunnel blowing test to determine the spin flutter stability of the wind tunnel test model under different conditions;

[0052] a) adjust the wind tunnel test model to respectively realize the wind tunnel test conditions of the short nacelle and wing connection stiffness, short nacelle weight, center of gravity and the like;

[0053] b) carry out wind tunnel blowing test for each test condition;

[0054] c) determine the spin flutter stability under different conditions according to the wind tunnel test results

[0055] d) compare and verify the spin flutter simulation analysis method of the tilt-rotor aircraft spin flutter wind tunnel test model with the simulation analysis results of Step 4.

[0056] Step 4: Based on the tilt-rotor aircraft prototype and the spin flutter simulation analysis method verified by the wind tunnel test, establish a spin-rotor-nacelle-wing coupled system spin flutter simulation analysis model to carry out spin flutter stability analysis;

[0057] a) based on the size of the tilt-rotor aircraft prototype and the aerodynamic elasticity mechanics analysis method, respectively establish a tilt-rotor aircraft rotor model, a wing model and an aerodynamic load analysis model to constitute a spin-rotor-nacelle-wing coupled system spin flutter simulation analysis model;

[0058] b) use the flutter analysis module to analyze the spin stability of the tilt-rotor aircraft to solve the spin flutter eigenvalue of the spin-rotor-nacelle-wing coupled system of the tilt-rotor aircraft;

[0059] c) determine the spin flutter stability of the spin-rotor-nacelle-wing coupled system of the tilt-rotor aircraft, the point where the modal damping ratio is equal to 0 is the critical point, and the corresponding forward flight speed is the spin flutter critical speed of the tilt-rotor aircraft; when the modal damping ratio is positive, the analyzed tilt-rotor aircraft does not have the risk of spin flutter; when the modal damping ratio is negative, the analyzed tilt-rotor aircraft has the risk of spin flutter;

[0060] Step 5: use the established tilt-rotor aircraft spin flutter simulation analysis model to study the spin flutter stability of the tilt-rotor aircraft with different short nacelle and wing connection stiffness, short nacelle weight, center of gravity, and correct the spin flutter simulation analysis model based on the wind tunnel test results;

[0061] a) based on the established tiltrotor aircraft turn flutter simulation analysis model in the fourth step, according to the dynamic scaling rule, the short cabin and wing connection stiffness, short cabin weight, center of gravity, etc. Data corresponding to the short cabin and wing connection stiffness, short cabin weight, center of gravity actual data are determined;

[0062] b) research the turn flutter stability of the tiltrotor aircraft under the actual data of the short cabin and wing connection stiffness, short cabin weight, center of gravity, analyze the turn flutter stability, and correct the established tiltrotor aircraft turn flutter simulation analysis model based on the wind tunnel test results;

[0063] Based on the corrected tiltrotor aircraft turn flutter simulation analysis model, in the process of type development, according to the actual situation of the short cabin and wing connection position stiffness change, the weight and center of gravity of the engine, main reducer and tilt mechanism in the short cabin, the model is iteratively updated in real time, the corresponding turn flutter stability is analyzed, the designed tiltrotor aircraft is strictly verified to be free of turn flutter instability problem in the flight envelope, and the safety of the type is ensured.

[0064] The application provides a simulation verification method for turn flutter analysis, comprising:

[0065] First step: based on the adjustable requirement of key parameters such as short cabin and wing connection stiffness, short cabin weight, center of gravity, carry out rotor-short cabin-wing coupling system wind tunnel test model design;

[0066] a) according to the size of the tiltrotor aircraft prototype and the dynamic scaling rule, the rotor-short cabin-wing coupling system wind tunnel test model suitable for the tiltrotor aircraft is carried out, the weight, center of gravity and short cabin and wing connection stiffness of the short cabin model 4 in the wind tunnel test are designed as adjustable structure;

[0067] b) Figure 1 The rotor-short cabin-wing coupling system wind tunnel test model of the tiltrotor aircraft comprises a fuselage model 2, a wing model 3, a short cabin model 4, a rotor model 5, a short cabin rotor connection model 6 and a short cabin and wing connection model 7 rigidly installed on the wind tunnel wall 1;

[0068] c) a short cabin rotor connection model 6 is designed in the short cabin 4, the short cabin rotor connection model 6 is integrated with the short cabin or rigidly connected, and is fixedly installed in the inside of the short cabin 4;

[0069] d) two bearing seats 62 are designed on the short cabin rotor connection model 6, which are used to assemble the rotor shaft 61, and a mass block 63 is installed between the two bearing seats;

[0070] e) the weight of the mass block 63 is designed as an adjustable weight or a combination of multiple mass blocks, and the weight parameter change of the adjustable short cabin is realized by changing the weight of the mass block 63;

[0071] f) The center of gravity of the mass block 63 is designed to be adjustable in the axial and lateral directions. The center of gravity of the nacelle is changed in the heading direction by moving the mass block 63 in the axial direction along the rotor shaft 61 between the two bearing seats 62, and the center of gravity of the adjustable nacelle is changed in the lateral direction by adjusting the lateral center of gravity of the mass block 63 itself;

[0072] g) The weight and center of gravity of the adjustable nacelle are changed by changing the weight and center of gravity of the mass block 63.

[0073] h) The nacelle-wing connection model 7 is designed as one or more connections with adjustable stiffness, and the nacelle-wing connection model 7 is connected to the wing through bolts 71.

[0074] i) The stiffness of the nacelle-wing connection model 7 is changed by adjusting the stiffness of the nacelle-wing connection model 7, adjusting the material or number of bolts 71, to change the stiffness of the nacelle-wing connection model 7 and the wing, to change the stiffness of the nacelle model 4 and the wing model 3.

[0075] Second step: Based on the designed tilt-rotor helicopter whirl flutter wind tunnel test model, a whirl flutter simulation analysis model of the wind tunnel test model is established, and simulation analysis of the rotor-nacelle-wing coupled system wind tunnel test model is carried out.

[0076] a) A whirl flutter simulation analysis model of the rotor-nacelle-wing coupled system wind tunnel test model is established, and simulation analysis models of the fuselage model 2, the wing model 3, the nacelle model 4, and the rotor model 5 of the wind tunnel test model are established respectively.

[0077] b) The mass points of the multi-point constraint element RBE3 are connected to the structure, the entity element simulates the nacelle-wing connection model 7, the multi-point constraint element RBE2 simulates the rigid connection of the bolt, the adjustable nacelle finite element simulation analysis model is established, the element properties of the multi-point constraint element RBE3 of the simulated mass block 63 are adjusted, the influence of the mass block 63 on the dynamic characteristics of the test model is studied based on the modal analysis method, and the corresponding nacelle weight and center of gravity wind tunnel test working condition is determined.

[0078] c) The spring element is used to simulate the nacelle-wing connection stiffness, the spring element properties are adjusted, the influence of the nacelle-wing connection stiffness on the dynamic characteristics of the test model is studied based on the modal analysis method, and the corresponding nacelle-wing connection stiffness wind tunnel test working condition is determined.

[0079] d) The wing modal analysis results are input into the whirl flutter simulation analysis model, the influences of the nacelle-wing connection stiffness, the nacelle weight, the center of gravity, etc. on the whirl flutter stability of the test model are studied respectively,

[0080] for comparison with the wind tunnel test data.

[0081] Third step: Based on the designed tiltrotor aircraft turn flutter wind tunnel test model and simulation analysis of the wind tunnel test conditions, carry out wind tunnel blowing test, determine the turn flutter stability of wind tunnel test model under different conditions;

[0082] a) Adjust the wind tunnel test model, respectively adjust the weight and center of gravity position of the nacelle and wing connection model 7 and mass block 63, complete the nacelle and wing connection stiffness, nacelle weight, center of gravity and other wind tunnel test conditions;

[0083] b) For each test condition, carry out wind tunnel blowing test and test data test;

[0084] c) According to the wind tunnel test results, judge the turn flutter stability under different conditions;

[0085] d) Compared with the simulation analysis results of the second step, verify the turn flutter simulation analysis method of the tiltrotor aircraft turn flutter wind tunnel test model.

[0086] Fourth step: Based on the turn flutter simulation analysis method of the tiltrotor aircraft prototype and wind tunnel test verification, establish the turn flutter simulation analysis model of the rotor-nacelle-wing coupling system, and carry out turn flutter stability analysis;

[0087] a) Based on the size of the tiltrotor aircraft prototype and the method of aerodynamic elasticity mechanics, respectively establish the rotor model, wing model and aerodynamic load analysis model of the tiltrotor aircraft, and constitute the turn flutter simulation analysis model of the rotor-nacelle-wing coupling system;

[0088] b) Perform turn stability analysis of the tiltrotor aircraft, and solve the turn flutter stability of the rotor-nacelle-wing coupling system of the tiltrotor aircraft;

[0089] c) Determine the turn flutter stability of the rotor-nacelle-wing coupling system of the tiltrotor aircraft. The point where the modal damping ratio is equal to 0 is the critical point. The analyzed tiltrotor aircraft is in the critical state of turn flutter. The horizontal coordinate of the critical point corresponds to the forward flight speed of the tiltrotor aircraft. When the modal damping ratio is positive, the analyzed tiltrotor aircraft does not exist the risk of turn flutter. When the modal damping ratio is negative, the analyzed tiltrotor aircraft exists the risk of turn flutter;

[0090] d) The following is an example, Figure 2With the forward flight speed increasing from 220km / h to 500km / h, the symmetric oscillation damping of the wing of the analyzed tiltrotor gradually decreases, and decreases to 0 at 460km / h, i.e. the whirling flutter boundary speed is 460km / h. At this speed, the tiltrotor is in a whirling flutter critical stable state. When the forward flight speed is lower than 460km / h, the analyzed tiltrotor will not have a whirling flutter instability problem. When the forward flight speed exceeds 460km / h, the analyzed tiltrotor will have a serious whirling flutter instability problem, endangering the type safety.

[0091] Step 5: Using the established whirling flutter simulation analysis model of the tiltrotor, the whirling flutter stability of the tiltrotor with different nacelle and wing connection stiffness, nacelle weight, and center of gravity is studied, and the whirling flutter simulation analysis model is corrected based on the wind tunnel test results.

[0092] a) Based on the whirling flutter simulation analysis model of the tiltrotor established in Step 4, the actual data of the nacelle and wing connection stiffness, nacelle weight, and center of gravity corresponding to the data of the nacelle and wing connection stiffness, nacelle weight, and center of gravity in the test are determined according to the dynamic scaling ratio criterion;

[0093] b) The whirling flutter stability of the tiltrotor with the actual data of the nacelle and wing connection stiffness, nacelle weight, and center of gravity is studied, the whirling flutter stability is analyzed, and the established whirling flutter simulation analysis model of the tiltrotor is corrected based on the wind tunnel test results;

[0094] Based on the corrected whirling flutter simulation analysis model of the tiltrotor, during the type development process, the model is iteratively updated in real time according to the actual situation, the corresponding whirling flutter stability analysis is carried out, and it is strictly verified that the designed tiltrotor does not have a whirling flutter instability problem within the flight envelope, thereby ensuring the type safety.

Claims

1. A simulation verification method for gyroscopic flutter analysis, characterized in that, include: Based on the adjustable requirements of key parameters such as nacelle and wing connection stiffness, nacelle weight, and center of gravity, a nacelle wind tunnel test model for gyroscopic flutter analysis was designed. Specifically, following a helicopter nacelle design, the model includes: a fuselage model, wing model, nacelle model, rotor model, nacelle-rotor connection model, and nacelle-wing connection model rigidly mounted on the wind tunnel wall; the wing model is mounted on the fuselage model; the nacelle-rotor connection model connects the rotor model and the nacelle model; the nacelle-rotor connection model is installed inside the nacelle model, and the nacelle-rotor connection model and the nacelle model are either integral or rigidly connected; the nacelle-wing connection model is connected to the wing model by bolts; two bearing seats for assembling the rotor shaft are installed on the nacelle-rotor connection model, and a mass block is installed between the two bearing seats. Based on the nacelle wind tunnel test model used for gyroscopic flutter analysis, a gyroscopic flutter simulation analysis model of the wind tunnel test model was established, and gyroscopic flutter simulation analysis of the nacelle wind tunnel test model for gyroscopic flutter analysis was carried out. Specifically, a gyroscopic flutter simulation analysis model of the nacelle wind tunnel test model was established, and simulation analysis models of the fuselage model, wing model, nacelle model, and rotor model of the wind tunnel test model were established respectively; multi-point constraint element RBE3 was used to simulate the connection between the mass point and the structure, solid element was used to simulate the nacelle wing connection model, and multi-point constraint element RBE2 was used to simulate the bolt rigid connection, establishing an adjustable nacelle finite element simulation analysis model. The element properties of the multi-point constrained element RBE3 simulating the mass block are analyzed. Based on modal analysis, the influence of the mass block on the dynamic characteristics of the test model is studied, and the corresponding nacelle weight and center of gravity wind tunnel test conditions are determined. The connection stiffness between the nacelle and the wing is simulated by spring elements. By adjusting the properties of the spring elements, the influence of the connection stiffness between the nacelle and the wing on the dynamic characteristics of the test model is studied, and the corresponding connection stiffness wind tunnel test conditions are determined. The wing modal analysis results are input into the slewing flutter simulation analysis model to study the influence of the connection stiffness between the nacelle and the wing, the nacelle weight, and the center of gravity parameters on the slewing flutter stability of the test model, for comparison with wind tunnel test data. Based on the nacelle wind tunnel test model used for flutter analysis and the wind tunnel test conditions determined by simulation analysis, wind tunnel blowing tests were carried out to determine the flutter stability of the wind tunnel test model under different conditions. By comparing the rotational flutter stability and simulation analysis results of the wind tunnel test model under different working conditions, the method of rotational flutter simulation analysis of the rotor-nacelle-wing coupled system wind tunnel test model is verified. Based on the gyroscopic flutter simulation analysis method, a gyroscopic flutter simulation analysis model of the rotor-nacelle-wing coupling system of a tiltrotor prototype was established, and gyroscopic flutter stability analysis was carried out.

2. The method according to claim 1, characterized in that, The center of gravity of the mass block is designed to be adjustable both axially and laterally. By moving the mass block axially between the two bearing seats along the rotor shaft, the nacelle's center of gravity heading parameters can be changed. By adjusting the lateral center of gravity of the mass block itself, the lateral center of gravity parameters of the adjustable nacelle can be changed.

3. The method according to claim 1, characterized in that, The mass block is designed as a single weight-adjustable mass block or a combination of multiple mass blocks. By changing the weight of the mass block, the weight parameters of the adjustable nacelle can be changed.

4. The method according to claim 1, characterized in that, The method further includes: A simulation analysis model of the rotor-nacelle-wing coupling system of a tiltrotor prototype was used to study the rotational flutter stability of the tiltrotor under different nacelle and wing connection stiffness, nacelle weight, and center of gravity.

5. The method according to claim 1, characterized in that, Based on the gyroscopic flutter simulation analysis method, a gyroscopic flutter simulation analysis model of the rotor-nacelle-wing coupling system of a tiltrotor aircraft prototype was established, and gyroscopic flutter stability analysis was carried out, including: Based on the dimensions and aeroelasticity analysis methods of the tiltrotor prototype, the rotor model, wing model and aerodynamic load analysis model of the prototype were established respectively, forming a simulation analysis model of the rotational flutter of the rotor-nacelle-wing coupled system of the prototype. The flutter analysis module is used to analyze the rotational stability of a tiltrotor aircraft and solve the rotational flutter stability of the rotor-nacelle-wing coupling system of the tiltrotor aircraft. Determine the rotational flutter stability of the tiltrotor rotor-nacelle-wing coupling system.

6. The method according to claim 5, characterized in that, The point where the modal damping ratio equals 0 is the critical point, and the tiltrotor is in a critical stable state of gyroscopic flutter. The corresponding forward flight speed is the critical speed of gyroscopic flutter for the tiltrotor. Under the condition that the modal damping ratio is positive, the tiltrotor analyzed does not have the risk of gyroscopic flutter; when the modal damping ratio is negative, the tiltrotor analyzed has the risk of gyroscopic flutter.

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