A visual test piece of an aircraft landing gear buffer

Abstract

The present invention discloses a visual test piece for an aircraft landing gear buffer, which is used to study the gas-liquid two-phase flow at the damping holes inside the landing gear buffer and simultaneously reveal the influence of insufficient flow on the performance of the buffer; the test piece includes a transparent window, an outer cylinder, a connecting pipe, a liquid level transmitter, a sensor, a damping hole, a piston rod and a plunger rod. The transparent window is made of aviation-grade plexiglass and is used to observe the flow condition of the internal medium; the connecting pipe connects the upper and lower cavities, and the flow mode of the internal liquid medium of the buffer test piece can be changed by opening and closing; the liquid level transmitter is installed at the top of the test piece and is used to monitor the internal liquid level height in real time. The structure of this buffer test piece is simple and easy to operate. When paired with a test bench, it can simulate the filling flow of the internal medium under real working conditions, monitor various indicators, and guide the design of the landing gear buffer.

Description

Technical Field

[0001] The present invention relates to a visual test piece for an aircraft landing gear buffer, and particularly to an experiment on the internal medium flow characteristics of an aircraft landing gear buffer, belonging to the field of design of a type of aircraft landing gear test piece. Background Art

[0002] During the design process of an aircraft landing gear buffer, the gas-liquid two-phase flow of the internal medium of the buffer at the damping hole during the retraction and extension of the landing gear is usually ignored, and the time for the oil in the damping hole to be filled by its own weight has not been quantitatively analyzed. At present, the design mainly relies on experience to ensure that the internal medium of the buffer can complete the filling action on time, which greatly reduces the reliability of the design of the aircraft landing gear buffer. Especially for military aircraft performing emergency landings, it is particularly dangerous. Verifying the test piece after it is manufactured has low efficiency and high cost, and is likely to cause significant economic losses. Summary of the Invention

[0003] Aiming at the gap in the relevant tests on the gas-liquid two-phase flow of the internal medium of the buffer during the design process of the aircraft landing gear buffer, the present invention provides a visual test piece for an aircraft landing gear buffer, which is used to carry out the experiment on the filling flow characteristics of the internal medium of the buffer.

[0004] To solve the above technical problems, the present invention adopts the following technical solutions:

[0005] A visual test piece for an aircraft landing gear buffer mainly includes structures such as an outer cylinder, a plunger rod, a piston rod, and a connecting pipe. The outer cylinder and the piston rod, as well as the plunger rod and the piston rod, are nested with each other and sealed by O-ring seals; rectangular windows are opened on both sides of the outer cylinder and closed with aviation-grade plexiglass.

[0006] The damping hole is connected to the plunger rod through a damping hole fixing seat to form an integral structure, which can be disassembled and replaced at any time; four long strip-shaped grooves are opened on the plunger wall to ensure the connectivity of the upper cavity, and it is fixed to the outer cylinder through radial screws.

[0007] The connecting pipe is connected to the tops of the upper and lower cavities of the buffer test piece through a direct vent nozzle, and a switch air valve is installed at each end, and it is connected by pipe threads.

[0008] The end cap is connected to the outer cylinder through a flange. Threaded holes are opened on the top of the end cap, and a capacitive liquid level sensor and a temperature and pressure integrated sensor are respectively installed, and the capacitive liquid level sensor is located at the central position.

[0009] The aviation plexiglass plate is fastened to the window of the outer cylinder through a circle of screws, and is sealed with a nitrile rubber sheet in the middle.

[0010] The outer circle of the damping hole fixing seat is grooved for placing an O-ring seal.

[0011] This test piece can measure the internal pressure and the temperature of the medium in real time during the test, which is beneficial to the study of the internal medium filling index of the buffer under different pressure conditions and temperature conditions.

[0012] The outer cylinder is provided with rectangular windows on both sides, which are closed by aviation plexiglass. It can provide a visual window while ensuring strength, facilitating the testers to directly observe the filling and flow of the internal medium of the buffer test piece.

[0013] Both ends of the connecting pipe are connected with switch air valves. When opened, the gases in the upper and lower chambers are in a connected state, and this model is the orifice outflow model of liquid under the action of self-weight in an open space; when the two switches are closed, the nitrogen and hydraulic oil in the upper and lower chambers pass through the damping holes simultaneously, which belongs to the model of gas-liquid two-phase flow and is consistent with the real model; by comparing the two models, the formula of single-hole gas-liquid two-phase flow in a closed state can be deduced.

[0014] The damping small holes with different length-diameter ratios and flow coefficients can be replaced to adapt to different types of aircraft landing gear buffers.

[0015] The liquid level sensor can feedback the oil level in the upper chamber of the buffer test piece in real time, forming an H-T curve, which is convenient for the quantitative study of the oil flow velocity at the damping small hole.

[0016] Aviation hydraulic oil is added to the inside of the buffer test piece through the hole at the plug, and the plug and the ED sealing ring are used for sealing.

[0017] Advantageous effects: Compared with the existing buffer test pieces, the significant advantage of the present invention is that it can test the filling and flow of the medium at the damping holes inside the buffer in various states of the landing gear. The present invention focuses on testing the gas-liquid two-phase flow of the internal medium of the buffer under the action of pure gravity. This test piece can simulate the filling of the buffer medium in any state before the real aircraft lands, can provide test references during the buffer design process, ensure that the filling and flow of the internal medium of the buffer meet the relevant regulations, is simple to operate, has a compact structure, a high degree of visualization, and a wide application range. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a schematic diagram of the overall structure of a visual aircraft landing gear buffer test piece;

[0019] Figure 2 is a schematic diagram of the visual window structure of the outer cylinder of a visual aircraft landing gear buffer test piece;

[0020] Figure 3 is a schematic diagram of the damping hole connection structure of a visual aircraft landing gear buffer test piece;

[0021] Figure 4It is a schematic diagram of the overall internal medium filling and flowing test device for an aircraft landing gear buffer;

[0022] Each label in the figure represents: 1. Temperature and pressure integrated sensor; 2. End cover; 3. Screw; 4. O-ring seal; 5. Piston rod; 6. Plug; 7. Check valve; 8. Bolt; 9. Direct vent nozzle; 10. Connecting pipe; 11. Screw; 12. Capacitive liquid level sensor; 13. Switching valve; 33. Outer cylinder; 34. Aviation plexiglass; 35. Screw; 41. Damping hole; 42. Damping hole fixing seat; 43. Plunger rod; 51. Frame; 52. Base; 53. Special fixture; 54. Power traction component. Detailed implementation method

[0023] To clearly illustrate the technical features of this invention patent, the following will elaborate on this patent through specific implementation cases and in combination with its attached drawings.

[0024] Implementation case 1

[0025] The described visual aircraft landing gear buffer test piece is mainly used for experimental verification and exploration of the flow characteristics of the internal filling medium of a real aircraft landing gear buffer. Its main structure includes an outer cylinder (33), a plunger rod (43), a piston rod (5), and a connecting pipe (10).

[0026] Determine the size of the damping hole of the buffer of the test object, select a damping hole (41) of an appropriate size, and install it at the bottom of the plunger rod (43) as shown in Figure 2 and install the buffer test piece as shown in Figure 1 The switching valve (13) is in the closed state. At this time, the intersection channel between the upper and lower cavities inside the test piece is only the damping hole (41); open the plug (6) at the bottom of the test piece, fill a certain amount of aviation hydraulic oil into the test piece, and screw on the plug (6).

[0027] Fill nitrogen into the test piece through the check valve (7), and select the inflation pressure according to the specific model, generally 2 - 3 Mpa.

[0028] Figure 4 It is a schematic diagram of the installation of the buffer test piece. The test piece is installed on the special fixture (53). The special fixture (53) is connected to the frame (51) and is driven by the power traction component (54) to complete the rotational motion around the axis, which is used to simulate the retraction and extension processes of a real aircraft landing gear.

[0029] The capacitive liquid level sensor (12) is used to measure the height change of the liquid level in the upper cavity. It is installed at the central position to ensure that the internal liquid level height can be accurately represented in various postures of the test piece, and a liquid level height - time curve can be made as the test progresses.

[0030] A temperature and pressure integrated sensor (1) is used to monitor the temperature and pressure of the upper chamber and the lower chamber in real time, and summarize the data to form a pressure-time curve.

[0031] According to the obtained liquid level height-time curve and the upper and lower chamber pressure-time curves, it is possible to analyze the flow rate of the medium at the damping hole (41) inside the test piece, as well as the hindering effect of gas-liquid exchange on the oil flow.

[0032] The aviation plexiglass (34) has high transparency, and the visualization window of the outer cylinder can help the testers directly observe the flow of the internal medium. A high-speed camera can be placed to observe the microscopic characteristics of the oil filling flow at the damping hole (41), such as the bubble size, the bubble generation speed, and the streamline.

[0033] Implementation Case 2

[0034] The described visual aircraft landing gear buffer test piece can be extended to complete the small hole outflow test in the open state, and can form a comparison with the Implementation Case 1 to quantitatively characterize the influence on the hydraulic oil filling flow caused by the gas-liquid two-phase flow at the damping hole (41) of the buffer.

[0035] On the basis of Implementation Case 1, the switch gas valve (13) is opened. At this time, the nitrogen in the upper chamber of the buffer is connected to the lower chamber, and at this time, no gas-liquid two-phase flow occurs at the damping hole (41). The pressure difference caused by the flow of the hydraulic oil is compensated through the connecting pipe (10).

[0036] Furthermore, according to the small hole outflow equation in the open state, influence factors can be added to form an empirical formula for the gas-liquid two-phase flow inside the buffer in the closed state.

[0037] Implementation Case 3

[0038] The described visual aircraft landing gear buffer test piece can study the filling flow of the internal medium of the buffer under different temperature environments.

[0039] Specifically, on the basis of Implementation Case 1, the entire test platform (52) is placed in a closed chamber at different temperatures to simulate the environment that the aircraft experiences at different temperatures. After the values of the temperature sensors are stable, the test is carried out, and the results are compared with those of Case 1 to determine the influence of temperature.

Claims

1. A visual test piece of an aircraft landing gear buffer, characterized in that, It includes an outer cylinder (33) with rectangular windows opened on both sides. An aircraft plexiglass plate (34) is fixed on the windows by screws (35); a damping hole fixing seat (42) fixes a damping hole (41) on a plunger rod (43) by a radial screw (3); a piston rod (5) is connected to the outer cylinder (33) through a flange, and O-ring seals (4) are used for sealing between the piston rod (5) and the outer cylinder (33) as well as between the piston rod (5) and the plunger rod (43); an end cover (2) is connected to the outer cylinder (33) through a flange; a connecting pipe (10) connects the upper part of the upper chamber and the upper part of the lower chamber, and the on-off of the gas in the upper and lower chambers is controlled by a switching air valve (13) on the connecting pipe (10).

2. The visualized aircraft landing gear buffer test piece according to claim 1, characterized in that, Two rectangular windows are opened on both sides of the outer cylinder (33), and the windows are closed by an aircraft plexiglass plate (34).

3. The visualized aircraft landing gear buffer test piece according to claim 1, characterized in that The connecting pipe (10) connects the upper and lower chambers through two direct air nozzles (9).

4. The visualized aircraft landing gear buffer test piece according to claim 1, characterized in that, The test piece belongs to a split structure, and the main body is composed of an outer cylinder (33), a piston rod (5) and a plunger rod (43), and they are sealed with each other by an O-ring seal (4).

5. The visualized aircraft landing gear buffer test piece according to claim 1, characterized in that, Threaded holes are opened on the end cover (2) for installing a temperature and pressure integrated sensor (1) and a capacitive liquid level sensor (12). The liquid level sensor (12) is installed at the center of the end cover (2) and is parallel to the outer cylinder of the test piece.

6. The visualized aircraft landing gear buffer test piece according to claim 1, wherein A temperature and pressure integrated sensor and a plug (6) are installed at the bottom of the piston rod (5).

7. The visualized aircraft landing gear buffer test piece according to claim 3, characterized in that A switching air valve (13) is installed at each end of the connecting pipe (10) near the direct air nozzle (9), and they are connected to each other by pipe threads and sealed with a sealant.

8. The visualized aircraft landing gear buffer test piece according to claim 4, characterized in that, A plug (6) and a temperature and pressure integrated sensor are installed at the lower end of the piston rod (5); a radial threaded hole is drilled at the lower end of the plunger rod (43), and a damping hole fixing seat (42) and a damping hole (41) are connected.

9. The visualized aircraft landing gear buffer test piece according to claim 8, wherein The damping hole (41) at the lower end of the plunger rod is fixed between the damping hole fixing seat (42) and the plunger rod (43). A boss is designed on the end face of the damping hole (41), and a replacement space for damping holes (41) with different inner diameters and length-diameter ratios is reserved.

10. An internal medium filling and flowing test device for an aircraft landing gear buffer, characterized in that, It includes a visual test piece of an aircraft landing gear buffer as described in any one of claims 1-9. The internal medium filling and flowing test device of the aircraft landing gear buffer further includes a test bench (52), a frame (51), a fixture (53) and a power traction assembly (54). The frame (51) and the power traction assembly (54) are installed on the test bench (52), the fixture (53) is installed on the frame (51), and the visual test piece of the aircraft landing gear buffer is installed on the fixture (53) and makes a rotational motion around the left end shaft under the traction force of the power traction assembly (54) to simulate the positions of the buffer at each stage of the real aircraft landing gear retraction and extension.

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