Buffer filling medium flow characteristic testing device and testing method

Abstract

The application discloses a kind of buffer filling medium flow characteristic testing device and testing method, the device includes base, inner cylinder, outer cylinder, plunger, damping component, end cover, liquid level sensor and control module;Inner cylinder is fixed on base, outer cylinder is arranged outside inner cylinder and is coaxial with inner cylinder;Plunger is arranged in outer cylinder and is coaxial with outer cylinder;Damping component is provided at the bottom of plunger, and damping component is located in inner cylinder;End cover is provided at the top of outer cylinder, and oil hole is formed in end cover;One end of liquid level sensor is provided on end cover, and the other end is located in plunger, and control module is electrically connected with liquid level sensor.The application obtains liquid level height in plunger in real time using liquid level sensor, obtains the curve of liquid level height with time change, thereby obtains the time required for liquid medium to fill inner cylinder, realizes the test of shortest recovery time, provides basis for verification and correction of flow characteristic empirical formula.

Description

Technical Field

[0001] This invention belongs to the field of aircraft landing gear design technology, and in particular relates to a testing device and method for testing the flow characteristics of the filling medium of aircraft landing gear buffers. Background Technology

[0002] Buffers are essential components of all modern landing gear, and their proper functioning is crucial for the safety of aircraft takeoff and landing. Most modern aircraft use oil-gas buffers, which work by dissipating energy through the flow of oil and storing energy through the compression of gas.

[0003] The function of the damper is to dissipate the kinetic energy of the aircraft during landing and taxiing by relying on the friction of the fluid flowing through the damping orifice. When designing the internal structure of the aircraft landing gear damper strut, the flow characteristics of the medium between its internal cavities should be fully considered. Clause 3.2.2.2(e) of GJB3063A-2008 "General Specification for Aircraft Landing Gear Systems" stipulates that after the landing gear is lowered, the damper should complete the flow of the fluid medium between its internal cavities within 2 minutes to achieve the required function. This requires that the flow characteristics of the medium between the two cavities inside the damper meet the minimum recovery time requirement. Therefore, it is necessary to analyze and verify the flowability of the damper filling medium during the landing gear lowering process. Summary of the Invention

[0004] The purpose of this invention is to provide a device and method for testing the flow characteristics of buffer filling media, so as to solve the problem that there is currently no device for testing the flowability of buffer filling media, which makes it impossible to analyze and verify the flowability of buffer filling media and to evaluate whether the flow characteristics of the media meet the specifications.

[0005] This invention solves the above-mentioned technical problems through the following technical solution: a device for testing the flow characteristics of a buffer filling medium, comprising:

[0006] Base;

[0007] The inner cylinder is provided on the base;

[0008] An outer cylinder is disposed outside the inner cylinder and coaxially arranged with the inner cylinder. The length of the outer cylinder is greater than the length of the inner cylinder, and the outer cylinder and the inner cylinder are sealed together.

[0009] A plunger is disposed inside the outer cylinder and coaxially arranged with the outer cylinder. The lower end of the plunger extends into the inner cylinder, and the plunger and the inner cylinder are sealed together. A damping assembly is provided at the bottom of the plunger, and the damping assembly is located inside the inner cylinder. A first inner cavity is formed by the gap between the outer cylinder and the plunger and the gap inside the plunger, and a second inner cavity is formed by the gap inside the inner cylinder.

[0010] An end cap located at the top of the outer cylinder has an oil injection hole.

[0011] A liquid level sensor with one end mounted on the end cap and the other end located inside the plunger;

[0012] And a control module electrically connected to the liquid level sensor.

[0013] Furthermore, the outer cylinder is made of PMMA material.

[0014] Furthermore, the size and structural shape of the damping component are consistent with the size and structural shape of the damping component of the buffer under test.

[0015] Furthermore, the damping component is a damping hole seat, which is mounted on the bottom of the plunger by a first bolt.

[0016] Furthermore, the damping assembly includes a damping hole seat and an oil needle. The damping hole seat is mounted on the bottom of the plunger by a first bolt. One end of the oil needle is located inside the damping hole seat, and the other end is threadedly connected to the base.

[0017] Furthermore, the oil needle is a triangular oil needle, a cross-shaped oil needle, or a straight oil needle.

[0018] Furthermore, the base, inner cylinder, outer cylinder, plunger, and end cap are connected by a second bolt.

[0019] Furthermore, the device also includes a high-speed camera for capturing the dynamic microscopic features of the liquid medium during the test.

[0020] Based on the same concept, the present invention also provides a method for testing the flow characteristics of a buffer filling medium using the buffer filling medium flow characteristic testing device described above, comprising the following steps:

[0021] The testing device is placed horizontally, and a liquid medium is injected through the oil injection hole on the end cap, followed by nitrogen gas.

[0022] After the testing device stabilizes, quickly adjust the testing device to a vertical position, and then use a liquid level sensor to collect the initial height of the liquid level inside the plunger.

[0023] According to the sampling period, the liquid level sensor continuously collects the height of the liquid level in the plunger until the liquid medium fills the inner cylinder or the liquid level in the plunger remains unchanged, thus obtaining a curve of the liquid level height changing over time.

[0024] The time required for the liquid medium to fill the inner cylinder is determined based on the curve.

[0025] Furthermore, the liquid medium is hydraulic oil.

[0026] Beneficial effects

[0027] Compared with the prior art, the advantages of the present invention are as follows:

[0028] This invention provides a device and method for testing the flow characteristics of a buffer filling medium. During the simulated landing gear lowering process, a liquid level sensor is used to acquire the liquid level height inside the plunger in real time, obtaining a curve showing the change in liquid level height over time. This yields the time required for the liquid medium to fill the inner cylinder, enabling testing of the shortest recovery time. The time obtained from the test can be used to verify the empirical formula for the flow characteristics of the buffer filling medium. Based on the verification results, the empirical formula can be corrected to ensure its accuracy and provide effective support for buffer design.

[0029] The device of this invention has a simple structure, and the connection between the damping component and the base and plunger is simple, which facilitates the quick replacement of test pieces with other parameters for testing and verification. Attached Figure Description

[0030] To more clearly illustrate the technical solution of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only one embodiment of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is a schematic diagram of the structure of the buffer filling medium flow characteristic testing device in an embodiment of the present invention;

[0032] Figure 2 This is a schematic diagram of the flow characteristic testing device for a damping assembly with an oil needle in an embodiment of the present invention.

[0033] Figure 3 This is a schematic diagram of the triangular oil needle in an embodiment of the present invention;

[0034] Figure 4 This is a schematic diagram of the cross-shaped oil needle structure in an embodiment of the present invention;

[0035] Figure 5 This is a schematic diagram of the structure of the single-line oil needle in an embodiment of the present invention;

[0036] Figure 6 This is a schematic diagram of dynamic microscopic feature observation in an embodiment of the present invention.

[0037] Among them, 1-base, 2-outer cylinder, 3-inner cylinder, 4-damping assembly, 41-damping hole seat, 42-oil needle, 5-plunger, 51-oil passage hole, 6-liquid level sensor, 7-end cap, 71-oil injection hole, 8-first inner cavity, 9-second inner cavity, 10-air bubble. Detailed Implementation

[0038] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] The technical solutions of this application will be described in detail below with specific embodiments. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments.

[0040] For oil-gas mixed-type buffers, a test device was designed to verify the flow characteristics of the buffer filling medium during the aircraft landing gear deployment process. For example... Figure 1 As shown in the figure, the buffer filling medium flow characteristic testing device provided in this embodiment of the invention includes a base 1, an inner cylinder 3, an outer cylinder 2, a plunger 5, a damping assembly 4, an end cap 7, a liquid level sensor 6, and a control module. The inner cylinder 3 is fixedly mounted on the base 1; the outer cylinder 2 is located outside the inner cylinder 3 and is coaxially arranged with the inner cylinder 3. The length of the outer cylinder 2 is greater than the length of the inner cylinder 3, and the outer cylinder 2 and the inner cylinder 3 are sealed together to prevent the liquid medium from flowing out through the gap between the outer cylinder 2 and the inner cylinder 3. The plunger 5 is located inside the outer cylinder 2 and is coaxially arranged with the outer cylinder 2. One end of the plunger 5 is fixed to the outer cylinder 2, and the other end extends into the inner cylinder 3. The plunger 5 and the inner cylinder 3 are sealed together to prevent the liquid medium from flowing into the inner cylinder 3 through the gap between the plunger 5 and the inner cylinder 3. A damping assembly 4 is provided at the bottom of the plunger 5, and the damping assembly 4 is located inside the inner cylinder 3; an end cap 7 is provided at the top of the outer cylinder 2, and an oil filling hole 8 is opened on the end cap 7; a first sealed inner cavity 8 is formed by the gap between the outer cylinder 2 and the plunger 5, the gap inside the plunger 5, and the end cap 7, and a second sealed inner cavity 9 is formed by the gap inside the inner cylinder 3. The first inner cavity 8 and the second inner cavity 9 are connected by the damping assembly 4. One end of the liquid level sensor 6 is provided on the end cap 7, and the other end is located inside the plunger 5. The control module is electrically connected to the liquid level sensor 6.

[0041] In one specific embodiment of the present invention, the outer cylinder 2 is made of PMMA (i.e., plexiglass). PMMA has a yield strength of 60 MPa, a density of 1.16 kg / m3, and a relatively high specific strength. Furthermore, PMMA has a light transmittance of 92%, which allows for clear observation of the flow of the liquid medium inside the device through the outer cylinder 2. It also facilitates the use of a high-speed camera to capture the microscopic features of the interaction between the liquid medium and nitrogen at the damping orifice seat 41.

[0042] The damping orifice is a flow channel for liquid medium and nitrogen gas in the upper and lower chambers (i.e., the first inner chamber 8 and the second inner chamber 9) inside the buffer. During the aircraft's landing buffering process, the liquid medium rapidly passes through the damping assembly 4, playing a damping role and dissipating the vertical kinetic energy of the entire aircraft. The damping assembly 4 in the test device should be as similar as possible to the damping assembly 4 of the real aircraft landing gear buffer, maintaining consistency in size and structural shape. At the same time, in order to facilitate the disassembly and assembly of the damping assembly 4 of the test device, so that damping assemblies 4 of different sizes and structural shapes (i.e., different parameters) can be quickly replaced during the test to study the influence of the orifice diameter, cross-section, length-to-diameter ratio, and flow coefficient of the damping assembly 4 on the flow characteristics, the damping assembly 4 is set at the bottom of the plunger 5 using the first bolt. When replacing the damping assembly 4 with different parameters, the damping orifice seat 41 and the plunger 5 are disassembled and assembled as a whole.

[0043] In one specific embodiment of the present invention, the damping component 4 is a damping hole seat 41 (i.e., a fixed damping hole), and the damping hole seat 41 is disposed at the bottom of the plunger 5 by a first bolt, such as... Figure 1 As shown.

[0044] In another specific embodiment of the present invention, the damping assembly 4 includes a damping hole seat 41 and an oil needle 42 (i.e., a variable damping hole). The damping hole seat 41 is mounted on the bottom of the plunger 5 by a first bolt. One end of the oil needle 42 is located inside the damping hole seat 41, and the other end is threadedly connected to the base 1. Figure 2 As shown.

[0045] The oil needle 42 is an important component in the aircraft landing gear buffer. During landing, the vertical distance of the oil needle 42 changes with the change of the buffer stroke, which can change the size of the flow area at the damping hole seat 41, thereby changing the damping capacity of the entire test device or buffer.

[0046] In this embodiment, as Figures 3-5 As shown, the oil needle 42 is a triangular oil needle 42, a cross oil needle 42, or a slotted oil needle 42 with a circular cross section. The lower end of the oil needle 42 is connected to the base 1 by a thread, ensuring that different types of oil needles 42 can be replaced. At the same time, the depth of the oil needle 42 in the base 1 can be adjusted by the thread, and the amount of the oil needle 42 protruding through the damping hole seat 41 can be adjusted, thereby changing the size of the flow area at the damping hole seat 41, so as to change the damping capacity of the entire testing device.

[0047] like Figure 1 and 2As shown, the outer cylinder 2 and the inner cylinder 3, as well as the outer cylinder 2 and the end cap 7, are all connected together by flanges. The plunger 5 is connected to the outer cylinder 2 by transverse screws, and the damping hole seat 41 is installed at the bottom of the plunger 5. The difference between the variable damping hole seat 41 (including the oil needle 42) and the fixed damping hole seat 41 is that the outer cylinder 2, the inner cylinder 3, and the base 1 are connected together by flanges, and the oil needle 42 is connected to the base 1 by threads.

[0048] In this embodiment, the liquid level sensor 6 is a capacitive liquid level sensor 6. The liquid level sensor 6 sends the liquid level height in the plunger 5 to the control module in real time through the communication interface. The control module obtains the curve of the liquid level height changing with time based on the liquid level height collected by the liquid level sensor 6, and then determines the time required for the liquid medium to fill the inner cylinder 3. This time is compared with the result calculated by the empirical formula of flow characteristics. The empirical formula of flow characteristics is corrected based on the comparison result to ensure the accuracy of the empirical formula of flow characteristics. This can form a method for analyzing, calculating and verifying the flowability of the buffer filling medium during the landing gear lowering process, providing effective support for product development.

[0049] The testing device of this invention mainly simulates the flow characteristics of the medium filling the buffer during the landing gear lowering process of an aircraft. By testing, the relationship curve of the liquid level height inside the buffer changing with time is obtained, and then the time required for the liquid medium to fill the lower cavity (i.e., the second inner cavity) of the buffer is determined, providing a basis for verifying and correcting the empirical formula of flow characteristics.

[0050] The test time can be used to verify and correct the empirical formula for flow characteristics, in order to derive a more accurate empirical formula for the flow characteristics of the medium filling the buffer during the aircraft landing gear lowering process. Depending on the type of test, there are four different types: routine verification test, high and low pressure verification test, ideal state vs. actual state comparison test, and low temperature equivalent test.

[0051] Based on the same concept, embodiments of the present invention also provide a method for testing the flow characteristics of a buffer filling medium using the buffer filling medium flow characteristic testing device described above, comprising the following steps:

[0052] Step 1: Place the test device horizontally, inject liquid medium through the oil injection hole on the end cap, and then inject nitrogen gas.

[0053] The liquid medium is injected in such a manner that, when the test device is placed vertically, the liquid medium fills the inner cylinder completely, and the liquid level in the plunger reaches the oil passage 51 at the bottom of the plunger. After the liquid medium and nitrogen are injected into the device, the oil filling hole is sealed, for example, by using bolts to seal the oil filling hole.

[0054] Step 2: After the testing device stabilizes, quickly adjust the testing device to a vertical position. At this time, use the liquid level sensor to collect the initial height of the liquid level in the plunger.

[0055] The stability of the testing device means that both the first and second inner chambers contain liquid media and nitrogen gas, and the liquid levels are stable. The testing device should be quickly adjusted to a vertical position to minimize the time before testing, preventing the liquid media in the first inner chamber from flowing into the second inner chamber.

[0056] Step 3: According to the sampling period, the liquid level sensor continuously collects the height of the liquid level inside the plunger until the liquid medium fills the inner cylinder or the liquid level inside the plunger remains unchanged, thus obtaining a curve of the liquid level height changing over time.

[0057] Step 4: Determine the time required for the liquid medium to fill the inner cylinder based on the curve of liquid level change over time.

[0058] The time from the initial height of the sample to when the liquid level no longer changes is the time required for the liquid medium to fill the inner cylinder.

[0059] During testing, a small amount of phosphor was added to the liquid medium, and a high-speed camera was placed on the side of the testing device to observe the dynamic microscopic characteristics of the liquid medium flow and the formation and rise of bubbles 10 within the device. The microscopic effect of the bubbles on the outflow of the liquid medium as they pass through the damping component was qualitatively analyzed. Figure 6 As shown. Figure 6 In the diagram, H represents the test height (the distance between the liquid level inside the plunger and the end cap), h represents the liquid level height, L represents the installation height (the distance between the end cap and the damping assembly), and B represents the test blind zone.

[0060] The above description only discloses specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or modifications that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A device for testing the flow characteristics of a buffer filling medium, characterized in that, The testing apparatus includes: Base; The inner cylinder is provided on the base; An outer cylinder is disposed outside the inner cylinder and coaxially arranged with the inner cylinder. The length of the outer cylinder is greater than the length of the inner cylinder, and the outer cylinder and the inner cylinder are sealed together. A plunger is disposed inside the outer cylinder and coaxially arranged with the outer cylinder. The lower end of the plunger extends into the inner cylinder, and the plunger and the inner cylinder are sealed together. A damping assembly is provided at the bottom of the plunger, and the damping assembly is located inside the inner cylinder. A first inner cavity is formed by the gap between the outer cylinder and the plunger and the gap inside the plunger, and a second inner cavity is formed by the gap inside the inner cylinder. An end cap located at the top of the outer cylinder has an oil injection hole. A liquid level sensor with one end mounted on the end cap and the other end located inside the plunger; And a control module electrically connected to the liquid level sensor; When the testing device is placed horizontally, liquid medium is injected through the oil injection hole, followed by nitrogen gas. After the testing device stabilizes, it is quickly adjusted to a vertical position. At this time, the initial height of the liquid level inside the plunger is collected using a liquid level sensor. In the vertical position, the height of the liquid level inside the plunger is continuously collected according to the sampling period until the liquid medium fills the inner cylinder or the liquid level inside the plunger remains constant. The control module obtains a curve of the liquid level changing over time based on the liquid level data collected by the liquid level sensor, and determines the time required for the liquid medium to fill the inner cylinder based on the curve.

2. The buffer filling medium flow characteristic testing device according to claim 1, characterized in that: The outer cylinder is made of PMMA material.

3. The device for testing the flow characteristics of the buffer filling medium according to claim 1, characterized in that: The size and structural shape of the damping component are consistent with the size and structural shape of the damping component of the buffer under test.

4. The buffer filling medium flow characteristic testing device according to claim 3, characterized in that: The damping component is a damping hole seat, which is mounted on the bottom of the plunger by a first bolt.

5. The buffer filling medium flow characteristic testing device according to claim 3, characterized in that: The damping assembly includes a damping hole seat and an oil needle. The damping hole seat is mounted on the bottom of the plunger by a first bolt. One end of the oil needle is located inside the damping hole seat, and the other end is threaded to the base.

6. The buffer filling medium flow characteristic testing device according to claim 5, characterized in that: The oil needle is a triangular oil needle, a cross-shaped oil needle, or a straight oil needle.

7. The buffer filling medium flow characteristic testing device according to claim 1, characterized in that: The base, inner cylinder, outer cylinder, plunger, and end cap are connected by a second bolt.

8. The buffer filling medium flow characteristic testing device according to claim 1, characterized in that: The device also includes a high-speed camera for capturing the dynamic microscopic features of the liquid medium during the test.

9. A method for testing the flow characteristics of a buffer filling medium using the buffer filling medium flow characteristic testing device as described in any one of claims 1 to 8, characterized in that, Includes the following steps: The testing device is placed horizontally, and a liquid medium is injected through the oil injection hole on the end cap, followed by nitrogen gas. After the testing device stabilizes, quickly adjust the testing device to a vertical position, and then use a liquid level sensor to collect the initial height of the liquid level inside the plunger. According to the sampling period, the liquid level sensor continuously collects the height of the liquid level in the plunger until the liquid medium fills the inner cylinder or the liquid level in the plunger remains unchanged, thus obtaining a curve of the liquid level height changing over time. The time required for the liquid medium to fill the inner cylinder is determined based on the curve.

10. The method according to claim 9, characterized in that: The liquid medium is hydraulic oil.

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