A model support device for releasing two rigid body degrees of freedom of a wind tunnel test model

Abstract

The invention discloses a model support device for releasing two rigid body degrees of freedom of a wind tunnel test model, comprising an upper and lower airfoil, two guide rail mounting seats, upper and lower hydraulic dampers, a guide rail, a pitch limit structure, a motion realization mechanism, and a grating ruler. The upper end of the lower airfoil is connected to the lower end of the guide rail through the guide rail mounting seat, the lower end of the upper airfoil is connected to the upper end of the guide rail through the guide rail mounting seat, the upper end and the lower end of the guide rail are respectively installed with upper and lower hydraulic dampers, the motion realization mechanism passes through the guide rail and is slidably connected to the guide rail, the test model is connected to the motion realization mechanism, and a pitch limit structure is installed on the motion realization mechanism to limit the pitch angle of the test model. The support device has the advantages of strong practicality, ingenious structure, and easy disassembly and assembly, avoids the coupling problem of the motion frequency of the gust generator, the vibration frequency of the model and the natural frequency of the support device, and reduces the problems of large blockage of the model support device, weak strength, improper model protection measures, etc. in the gust test.

Description

Technical Field

[0001] The invention relates to a model supporting device for releasing two rigid body degrees of freedom of a wind tunnel test model. Background Art

[0002] Gusts, also known as gusts or atmospheric turbulence, are a deterministic wind disturbance with a relatively high intensity in the atmosphere. When an aircraft encounters a gust, the fuselage will generate additional unsteady aerodynamic forces and moments, which will have an adverse effect on the flight performance of the aircraft. Modern civil aircraft, such as large passenger aircraft, emphasize economy, comfort, safety, and reliability, and require high aerodynamic efficiency and low structural weight. They usually use large aspect ratio wings and use a large amount of composite materials in structural materials. The aircraft wings have greater flexibility, so the aircraft is more sensitive to gust response. Gust loads, especially vertical discrete gust loads, often become the most serious flight loads, which have a serious impact on the comfort, safety, economy, and reliability of large passenger aircraft. When an aircraft encounters unsteady aerodynamic loads caused by medium or low-intensity gusts, it will cause turbulence in the aircraft, make passengers nervous, reduce the comfort of civil aircraft, and even cause personal injury to passengers; when an aircraft encounters high-intensity unsteady aerodynamic loads, the local overload of the aircraft can reach more than 2.5g, which will damage the aircraft structure or cause fatigue cracks, affecting the service life of the aircraft and having a great impact on the safety and reliability of the aircraft. For example, in 2016, the Il-18 passenger plane encountered strong gusts when landing in Yakutia. Since this type of aircraft was not equipped with a gust mitigation system, the severe turbulence and hard landing impact caused 16 serious injuries and serious damage to the fuselage structure. Civil aircraft are extremely sensitive to fatigue damage caused by gust loads, and the gust load spectrum is an important scientific basis for the design of aircraft structure life reliability. Due to the gust load problem, in order to ensure the strength of the aircraft, the aircraft structure needs to be strengthened, resulting in an increase in the weight of the aircraft, which in turn affects the economy of the aircraft.

[0003] Domestic and foreign civil aircraft airworthiness regulations have made clear provisions for gust loads. Both China's transport aircraft airworthiness standards (CCAR-25-R4) and the U.S. Aviation Administration Regulations (FAR-25) have given corresponding provisions for gust load design criteria. Accurate prediction of gust loads is an important task that must be carried out during the aircraft design phase. The development of large civil aircraft in my country has put forward an urgent need for the development of advanced large-scale high and low speed wind tunnel gust test technology. In addition to the gust load prediction requirements required for aircraft strength design, gust load mitigation technology also needs to be verified.

[0004] In gust tests, the model support device is one of the key technologies that affect the test results. In full-model gust tests, it is required to simulate the free flight state of the real aircraft as much as possible, thereby providing the model with more degrees of freedom. For example, some gust forms may be caused by the coupling of rigid body motion modes and structural elastic modes. The dynamic characteristics of such gust forms will be affected by the constraint load of the support system, resulting in serious deviations in the gust test results. Therefore, in gust tests, the rigid body freedom of the model in the two directions of sinking and pitching must be fully considered, and a model support device that can realize the two rigid body freedoms of the model in sinking and pitching needs to be designed. Summary of the invention

[0005] In order to solve the above problems, the purpose of the present invention is to provide a model support device that releases two rigid degrees of freedom of the wind tunnel test model. The present invention effectively solves the drawbacks that the full-model support device of the wind tunnel gust test cannot release the two rigid degrees of freedom of the model's buoyancy and pitch; avoids the coupling problem between the gust generator's motion frequency, the model's vibration frequency and the support device's natural frequency; and reduces the problems of large blockage, weak strength, and improper model protection measures of the model support device in the gust test.

[0006] The present invention is mainly realized through the following technical scheme: a model support device for releasing two rigid body degrees of freedom of a wind tunnel test model, comprising an upper airfoil, two guide rail mounting seats, an upper hydraulic damper, a guide rail, a pitch limiting structure, a motion realization mechanism, a grating ruler, a lower hydraulic damper and a lower airfoil, wherein the lower end of the lower airfoil is connected to the lower wall of the wind tunnel, the upper end of the lower airfoil is connected to the lower end of the guide rail through the guide rail mounting seat, the upper end of the upper airfoil is connected to the upper wall of the wind tunnel, the lower end of the upper airfoil is connected to the upper end of the guide rail through the guide rail mounting seat, the upper end and the lower end of the guide rail are respectively equipped with an upper hydraulic damper and a lower hydraulic damper, the motion realization mechanism passes through the guide rail and is slidably connected to the guide rail, the test model is connected to the motion realization mechanism, the motion realization mechanism is equipped with a pitch limiting structure to limit the pitch angle of the test model, and the guide rail is equipped with a grating ruler.

[0007] The present invention also has the following technical features:

[0008] 1. The motion realization mechanism includes a model connecting piece, two turntable bearings, an adapter frame, two impact blocks and a rolling bearing group. The inner wall of the model connecting piece is rotatably connected to the outer wall of the adapter frame through two turntable bearings. A circle of rolling bearing groups is installed on the inner wall of the adapter frame, and is connected to the guide rail through the rolling bearing group. Two impact blocks are also installed on the inner wall of the adapter frame, and their positions correspond to the upper hydraulic damper and the lower hydraulic damper.

[0009] 2. The model connecting piece is provided with a pitch angle limiting hole.

[0010] Advantages and beneficial effects of the present invention: The supporting device has the advantages of strong practicality, ingenious structure, easy disassembly and assembly, etc. The motion implementation mechanism of the model supporting method of the two rigid body degrees of freedom of the test model is located on the guide rail, thereby avoiding the coupling problem between the motion frequency of the gust generator, the vibration frequency of the model and the natural frequency of the supporting device, and reducing the problems of large blockage, weak strength, improper model protection measures and the like of the model supporting device in the gust test. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a schematic diagram of the overall structure of the model supporting device of the present invention.

[0012] Figure 2 A cross-sectional diagram of the mechanism that implements the device motion.

[0013] Figure 3 It is a side view of the rolling bearing group.

[0014] Among them, 1. upper wing profile, 2. guide rail mounting seat, 3. upper hydraulic damper, 4. guide rail, 5. test model, 6. pitch limit structure, 7. motion realization mechanism, 8. grating scale, 9. lower hydraulic damper, 10. lower wing profile, 21. model connector, 22. turntable bearing, 23. adapter frame, 24. impact stopper, 25. rolling bearing group, 31. disc spring, 32. pulley seat, 33. angular contact bearing. DETAILED DESCRIPTION

[0015] The present invention is further described below with reference to the accompanying drawings:

[0016] Example 1

[0017] like Figure 1-3As shown, a model support device for releasing two rigid body degrees of freedom of a wind tunnel test model comprises an upper airfoil 1, two guide rail mounting seats 2, an upper hydraulic damper 3, a guide rail 4, a pitch limiting structure 6, a motion realization mechanism 7, a grating ruler 8, a lower hydraulic damper 9, and a lower airfoil 10. The lower end of the lower airfoil 10 is connected to the lower wall of the wind tunnel, the upper end of the lower airfoil 10 is connected to the lower end of the guide rail 4 through the guide rail mounting seat 2, the upper end of the upper airfoil 1 is connected to the upper wall of the wind tunnel, the lower end of the upper airfoil 1 is connected to the upper end of the guide rail 4 through the guide rail mounting seat 2, the upper end and the lower end of the guide rail 4 are respectively installed with an upper hydraulic damper 3 and a lower hydraulic damper 9, the motion realization mechanism 7 passes through the guide rail 4 and is slidably connected to the guide rail 4, the test model 5 is connected to the motion realization mechanism 7, the motion realization mechanism 7 is installed with a pitch limiting structure 6 to limit the pitch angle of the test model 5, and the guide rail 4 is installed with a grating ruler 8. The motion realization mechanism 7 includes a model connection member 21, two turntable bearings 22, an adapter frame 23, two impact blocks 24 and a rolling bearing group 25. The inner wall of the model connection member 21 is rotatably connected to the outer wall of the adapter frame 23 through the two turntable bearings 22. The inner wall of the adapter frame 23 is equipped with a circle of rolling bearing group 25, and is connected to the guide rail 4 through the rolling bearing group 25. The inner wall of the adapter frame 23 is also equipped with two impact blocks 24, and their positions correspond to the upper hydraulic damper 3 and the lower hydraulic damper 9. The model connection member 21 is provided with a pitch angle limit hole, which can achieve a pitch angle change of -30° to 30°.

[0018] like Figure 1 As shown, during the test, the lower airfoil is first connected to the lower wall of the wind tunnel, the guide rail is installed on the lower airfoil, the motion realization mechanism 7 is passed through the guide rail 4, and then the test model 5 is connected to the motion realization mechanism 7 through the model connector 21, and the upper airfoil 1 is connected to the guide rail 4, and finally the upper airfoil 1 is fixed to the upper wall of the wind tunnel. The airfoil design of the supporting device is carried out to reduce the blockage; the strength analysis is carried out to ensure that the strength of the device meets the test requirements, and the model protection problem is solved by installing hydraulic dampers at the upper and lower ends.

[0019] like Figure 2-Figure 3As shown, the rolling bearing group 25 and the turntable bearing 22 release the two rigid body degrees of freedom of the test model 5, namely, sinking and pitching, respectively, to realize the free movement of the test model 5 in the sinking and pitching directions. The rolling bearing group 25 and the adapter frame 23 are connected by a bolt group to realize the sinking and floating movement of the test model 5 along the guide rail 4; the inner ring of the turntable bearing 22 is connected to the model connector 21 by a bolt group, and the model connector 21 has a pitch angle limiting hole, which can realize the change of the pitch angle from -30° to 30°. The outer wall of the adapter frame 23 is connected to the outer ring 22 of the turntable bearing by a bolt group, and the relative rotation of the turntable bearing 22 and the linear motion of the rolling bearing group 25 along the guide rail 4 are combined on the test model 5, realizing the free movement of the test model 5 in the direction of sinking and pitching. In the later test, the fluid-solid coupling analysis of the device was carried out, and the device was partially strengthened according to the analysis results to ensure that the movement frequency of the gust generator, the vibration frequency of the model and the natural frequency of the support device do not overlap and cannot produce resonance; the airfoil design of the support device was carried out to reduce the blockage; the strength analysis was carried out to ensure that the strength of the device meets the test requirements; the pitch angle limit mechanism and the hydraulic damper for sinking and floating motion were used to solve the model protection problem. The support device has the advantages of strong practicality, ingenious structure, and easy disassembly and assembly.

Claims

1. A model support device for releasing two rigid body degrees of freedom of a wind tunnel test model, comprising an upper airfoil (1), two guide rail mounting seats (2), an upper hydraulic damper (3), a guide rail (4), a pitch limit structure (6), a motion realization mechanism (7), a grating ruler (8), a lower hydraulic damper (9) and a lower airfoil (10), characterized in that: The lower end of the lower airfoil (10) is connected to the lower wall of the wind tunnel, the upper end of the lower airfoil (10) is connected to the lower end of the guide rail (4) through a guide rail mounting seat (2), the upper end of the upper airfoil (1) is connected to the upper wall of the wind tunnel, the lower end of the upper airfoil (1) is connected to the upper end of the guide rail (4) through a guide rail mounting seat (2), the upper end and the lower end of the guide rail (4) are respectively installed with an upper hydraulic damper (3) and a lower hydraulic damper (9), the motion realization mechanism (7) passes through the guide rail (4) and is slidably connected to the guide rail (4), the test model (5) is connected to the motion realization mechanism (7), and a pitch limiting structure (6) is installed on the motion realization mechanism (7) to limit the pitch of the test model (5). The guide rail (4) is provided with a grating ruler (8) at an elevation angle; the motion realization mechanism (7) comprises a model connecting member (21), two turntable bearings (22), an adapter frame (23), two impact blocks (24) and a rolling bearing group (25); the inner wall of the model connecting member (21) is rotatably connected to the outer wall of the adapter frame (23) through the two turntable bearings (22); the inner wall of the adapter frame (23) is provided with a circle of rolling bearing groups (25) and is connected to the guide rail (4) through the rolling bearing groups (25); the inner wall of the adapter frame (23) is also provided with two impact blocks (24), and the positions of the impact blocks (24) correspond to the upper hydraulic damper (3) and the lower hydraulic damper (9).

2. A model support device for releasing two rigid degrees of freedom of a wind tunnel test model according to claim 1, characterized in that: The model connecting piece (21) is provided with a pitch angle limiting hole.

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