Shock tube sparse wave eliminating device capable of weakening self-reflected wave

Abstract

The utility model relates to an auxiliary device for simulating a shock tube by explosive waves, in particular to a shock tube sparse wave eliminating device capable of weakening self-reflected waves, and aims to solve the problem of inaccurate experimental data caused by the fact that sparse waves generated at the orifice of a shock tube are transmitted back to the upstream during an experiment. The device comprises a circular wave absorbing plate arranged at a tube opening of an explosive wave simulation shock tube; a central wave absorbing hole and at least three edge wave absorbing holes are formed in the wave absorbing plate; the central wave absorbing hole is located in the center of the wave absorbing plate, and the at least three edge wave absorbing holes are evenly distributed around the circumference of the central wave absorbing hole. The utility model can effectively weaken the peak value of the backflow reflection wave of the shock wave in the experiment and improve the experiment precision.

Description

Technical Field

[0001] This utility model relates to an auxiliary device for simulating an explosion wave shock tube, specifically a rarefaction wave elimination device for a shock tube that can reduce its own reflected waves. Background Technology

[0002] The explosion wave simulation shock tube is an important experimental platform for simulating explosion shock waves. It is widely used in many fields such as the evaluation of the explosion shock resistance performance of bridges, buildings, and vehicles, and the study of biological shock injuries. The peak pressure and the duration of the positive pressure of the shock wave it generates are key indicators for evaluating the simulation effect.

[0003] For shock tubes used to simulate the environment of an explosion wave, the overpressure generated within the tube decays over time. When the overpressure decays to below a certain value, the airflow behind the shock wave changes from supersonic to subsonic. At this point, the shock wave, after passing through the shock tube inlet, will generate a rarefaction wave that propagates in the opposite direction into the shock tube. During experiments, this rarefaction wave disrupts the flow field environment within the expansion section of the shock tube, affecting the shock wave pressure history within the test section and leading to inaccurate experimental data. Utility Model Content

[0004] The purpose of this invention is to solve the problem that the rarefaction wave generated at the outlet of the shock tube during the experiment propagates upstream, resulting in inaccurate experimental data. The invention provides a rarefaction wave elimination device for shock tubes that can reduce the reflected wave.

[0005] To achieve the above objectives, the technical solution provided by this utility model is as follows:

[0006] A rarefaction wave elimination device for a shock tube that can reduce its own reflected waves is characterized by: a circular wave-damping plate disposed at the inlet of a simulated shock tube for an explosion wave; the wave-damping plate is provided with a central wave-damping hole and X edge wave-damping holes; X = 0 or X ≥ 2, where X is a positive integer; the central wave-damping hole is located at the center of the wave-damping plate, and when X ≥ 2, the X edge wave-damping holes are evenly arranged around the circumference of the central wave-damping hole.

[0007] Furthermore, the inner wall surfaces of the central and edge wave-damping holes are configured with annular protrusions with a circular arc cross-section along the circumference, forming an arc-shaped transition, and the diameter of the arc is the same as the thickness of the wave-damping plate.

[0008] Furthermore, the outlet of the explosion wave simulation shock tube is provided with a connecting flange; the outer edge of the wave-damping plate is provided with a transition flange of the same size as the connecting flange; the connecting flange and the transition flange are connected by bolts.

[0009] Furthermore, if the inner diameter of the central wave-damping hole is defined as d2 and the inner diameter of the edge wave-damping hole is defined as d3, then 1.2≤d2 / d3≤1.5.

[0010] Furthermore, the number of edge damping holes is eight.

[0011] Compared with the prior art, the beneficial effects of this utility model are:

[0012] 1. The present invention provides a rarefaction wave elimination device for shock tubes that can reduce their own reflected waves. It is provided with a central wave-damping hole and zero or more edge wave-damping holes, which can effectively reduce the peak value of the shock wave backflow reflection wave during the experiment and improve the experimental accuracy.

[0013] 2. The present invention provides a rarefaction wave elimination device for shock tubes that can reduce their own reflected waves. The inner wall surfaces of the central wave-eliminating hole and the edge wave-eliminating hole are set as annular protrusions with a circular arc cross-section along the circumference, forming an arc-shaped transition. This can prevent the jet contraction effect when the shock wave airflow passes through, thereby improving the rarefaction wave elimination efficiency. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of an embodiment of a shock tube rarefaction wave elimination device that can reduce its own reflected waves according to the present invention.

[0015] Figure 2 This is a cross-sectional view of an embodiment of a shock tube rarefaction wave elimination device that can reduce its own reflected waves according to this utility model.

[0016] Figure 3 This is an embodiment of the rarefaction wave elimination device of the shock tube that can reduce its own reflected wave and an assembly diagram of the explosion wave simulation shock tube of this utility model.

[0017] Figure 4 This is a partial schematic diagram of the assembly of a shock tube rarefaction wave elimination device that can reduce its own reflected waves and an explosion wave simulation shock tube according to an embodiment of the present invention.

[0018] Explanation of reference numerals in the attached figures:

[0019] 1-Bell damping plate, 2-Central bell damping hole, 3-Edge bell damping hole, 4-Transition flange, 5-Fixing bolt hole, 6-Connecting flange, 7-Explosion wave simulation shock tube, 8-Bolt. Detailed Implementation

[0020] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0021] A rarefaction wave cancellation device for shock tubes that can reduce their own reflected waves, see [link to relevant documentation]. Figures 1-4The system includes a circular wave-damping plate 1 installed at the inlet of the explosion wave simulation shock tube 7; the wave-damping plate 1 is provided with a central wave-damping hole 2 and eight edge wave-damping holes 3 evenly distributed around the central wave-damping hole 2; the function of providing a central wave-damping hole 2 and eight edge wave-damping holes 3 is as follows: after the shock wave acts on the shielding part of the outlet of the explosion wave simulation shock tube 7, although the reduction of the outflow area can suppress the formation of rarefaction waves, it will also form a backflow reflection wave, introducing new interference factors into the pressure environment within the test section of the explosion wave simulation shock tube 7. The use of a perforated plate can approximately discretize the "interaction between the shock wave and the plate" into multiple sets of "interaction between the shock wave and the rod", which can effectively reduce the peak value of the backflow reflection wave.

[0022] The inner walls of the central wave-damping hole 2 and the edge wave-damping holes 3 are circumferentially designed with annular protrusions of circular arc cross-section, forming an arc-shaped transition. The diameter of the arc is the same as the thickness of the wave-damping plate 1. This is because when the shock wave airflow exits the central wave-damping hole 2 and the edge wave-damping hole 3, a jet contraction phenomenon occurs, meaning the actual outflow area is smaller than the opening area. The degree of jet contraction is related to the shape of the hole and the edge shape. For example, for a shock wave with an overpressure of 50 kPa, when passing through a rectangular slit without any rounded corner treatment, its actual outflow area will only reach about 60% of the total area of ​​the pipe opening. Assuming this opening form is adopted, the working effect of the rarefaction wave elimination device will be unpredictable and deviate significantly from the expected indicators; at the same time, due to the excessively low outflow area, a blockage phenomenon will occur, generating a backflow compression wave, causing greater interference to the test section environment. According to the subsonic airflow jet theory, when the airflow flows through a circular hole with a perfectly smooth edge, no jet contraction effect will occur. Therefore, this embodiment can minimize the impact of the aperture structure on the rarefaction wave elimination effect.

[0023] To increase the connection strength, the outlet of the explosion wave simulation shock tube 7 is provided with a connecting flange 6; the outer edge of the wave damping plate 1 is provided with a connecting flange 6 of the same size as the connecting flange 6; both the connecting flange 6 and the connecting flange 4 are provided with sixteen circumferentially distributed fixing bolt holes 5, and the connecting flange 6 and the transition flange 4 are connected by sixteen bolts 8 passing through the fixing bolt holes 5 respectively.

[0024] Let the inner diameter of the central wave-damping hole 2 be d2, and the inner diameter of the edge wave-damping hole 3 be d3, then d2 / d3 = 1.3.

[0025] Table 1. Relationship between shock wave overpressure and pipe orifice area ratio

[0026]

[0027] In actual working conditions, the total number of edge damping holes 3 can be determined based on the total area of ​​the through holes required for the actual shock wave overpressure. The relationship between the shock wave overpressure and the cross-sectional area can be found in Table 1.

Claims

1. A rarefaction wave elimination device for a shock tube capable of reducing its own reflected waves, characterized in that: Includes a circular shock-absorbing plate (1) installed at the inlet of the explosion wave simulation shock tube (7); The wave-damping plate (1) is provided with a central wave-damping hole (2) and X edge wave-damping holes (3); X = 0 or X ≥ 2, where X is a positive integer; The central wave-damping hole (2) is located at the center of the wave-damping plate (1). When X ≥ 2, X edge wave-damping holes (3) are evenly arranged around the circumference of the central wave-damping hole (2).

2. The rarefaction wave elimination device for shock tubes that can reduce self-reflected waves according to claim 1, characterized in that: The inner wall surfaces of the central wave-damping hole (2) and the edge wave-damping hole (3) are set as annular protrusions with a circular arc cross-section along the circumference, forming an arc-shaped transition. The diameter of the arc is the same as the thickness of the wave-damping plate (1).

3. The rarefaction wave elimination device for shock tubes that can reduce self-reflected waves according to claim 2, characterized in that: The explosion wave simulation shock tube (7) is provided with a connecting flange (6) at its port; the outer edge of the wave-damping plate (1) is provided with a transition flange (4) of the same size as the connecting flange (6); the connecting flange (6) and the transition flange (4) are connected by bolts (8).

4. The rarefaction wave elimination device for shock tubes that can reduce self-reflected waves according to claim 3, characterized in that: Define the inner diameter of the central wave-damping hole (2) as d2 and the inner diameter of the edge wave-damping hole (3) as d3, then 1.2≤d2 / d3≤1.

5.

5. A rarefaction wave elimination device for a shock tube capable of reducing its own reflected waves according to any one of claims 1 to 4, characterized in that: The number of edge damping holes (3) is eight.

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