A rarefaction wave elimination device

Abstract

The present invention discloses a rarefaction wave elimination device, which comprises a motor, a shock tube, a first housing, a second housing and blades. The shock tube is connected to the first housing. The second housing is concentric with the first housing and is movably connected to the first housing. A communicating channel is formed at the centers of the shock tube, the first housing and the second housing. The blades are located between the first housing and the second housing. The number of the blades is multiple and they are circumferentially distributed around the axis of the second housing. The motor can drive the second housing to rotate around its own axis, and the rotation of the second housing drives all the blades to gather towards the center or move away from the center. When all the blades gather towards the center, the channel area where the blades are located gradually decreases until it is completely closed. When all the blades move away from the center, the channel area where the blades are located gradually increases. The present invention can effectively reduce the influence of rarefaction waves on shock waves, and has the advantages of simple structure, low cost and convenient assembly.

Description

Technical Field

[0001] The present invention relates to the technical field of explosion shock wave effect simulation, and particularly to a rarefaction wave elimination device. Background Art

[0002] The Large Blast / Thermal Simulator (hereinafter referred to as LB / TS) is used to detect the performance of civilian equipment (such as trucks, civilian helicopters, etc.) under large blast shock loads and thermal loads. The LB / TS is essentially a large shock tube. In the shock tube, compressed gas is rapidly released from the drive vessel, forming a shock wave that enters the extended part of the LB / TS. By changing the volume and initial pressure of the drive vessel, the explosions of different types of weapons can be simulated. When the shock wave reaches the end of the extended part of the LB / TS and contacts the atmosphere, a rarefaction wave with reverse flow will be generated. This rarefaction wave enters the extended part of the LB / TS and will have a devastating impact on the characteristics of the simulated shock wave.

[0003] To eliminate the influence of the rarefaction wave, an obvious method is to extend the length of the extended part of the LB / TS to be long enough so that the rarefaction wave is difficult to reach the test section. However, for an LB / TS with an extended part cross-sectional area of 163 m² and a length of 160 m, theoretically calculated, when the length of the extended part is extended to 1500 m, the influence of the rarefaction wave on the simulation device can be completely eliminated. Obviously, the cost of building such a long LB / TS is unacceptable. Summary of the Invention

[0004] The object of the present invention is to overcome the deficiencies of the above-mentioned prior art and provide a rarefaction wave elimination device. A rarefaction wave elimination device (Rarefaction Wave Eliminator, hereinafter referred to as RWE) - a mechanical iris mechanism (the housing one can be called the mechanical iris lower housing, the housing two can be called the mechanical iris upper housing, and the blade can be called the mechanical iris blade) is installed at the end of the extended part of the LB / TS. It is a "nozzle" whose cross-sectional area can be adjusted with time. When the air flow passes through the RWE, the reduced cross-sectional area accelerates the air flow. When one of the two conditions that its static pressure is reduced to equal the atmospheric pressure or its Mach number equals 1 is achieved, the rarefaction wave will not be generated. When the motor operates according to the program, the gear starts to rotate, and then drives the housing two to rotate around its axis. The blade slides in the housing one guide part of the housing one. During the sliding process of the 8 blades, the area bearing the shock wave becomes larger, so that the cross-sectional area ratio changes according to the requirements. With the change of the air flow, the "nozzle" cross-sectional area of the RWE continuously changes to meet the continuously changing air flow. Finally, the air flow is accelerated to the target value, and the rarefaction wave will not be generated.

[0005] To achieve the above object, the technical solution of the present invention is:

[0006] A rarefaction wave elimination device, comprising a motor, a shock tube, a first housing, a second housing, and blades. The shock tube is connected to the first housing. The second housing is concentric with the first housing and is movably connected to the first housing. A communication channel is formed at the centers of the shock tube, the first housing, and the second housing. The blades are located between the first housing and the second housing. The number of blades is multiple and they are circumferentially distributed around the axis of the second housing. The motor can drive the second housing to rotate around its own axis, and the rotation of the second housing drives all the blades to gather towards the center or move away from the center. When all the blades gather towards the center, the channel area where the blades are located gradually decreases until it is completely closed. When all the blades move away from the center, the channel area where the blades are located gradually increases.

[0007] The output end of the motor is connected to a gear, and teeth meshing with the gear are provided on the outer wall of the second housing. Through the cooperation of the gear and the teeth, the motor can drive the second housing to rotate around its own axis.

[0008] A shock tube through hole is provided at the center of the shock tube, a first housing through hole is provided at the center of the first housing, and a second housing through hole is provided at the center of the second housing. The shock tube through hole, the first housing through hole, and the second housing through hole are communicated to form a channel.

[0009] A connecting block extending towards the second housing is provided on one end face of the first housing facing the second housing. The connecting block includes a first block and a second block. The second housing includes a notch. The first block passes through the notch, and the second block is located on the end face of the second housing away from the first housing and at least part of the second block extends beyond the contour range of the notch.

[0010] A second housing guiding portion is provided on the end face of the second housing close to the first housing. A second blade guiding portion is provided on the end face of the blade close to the second housing. When the second housing rotates around its own axis, the second housing guiding portion moves along the second blade guiding portion and drives all the blades to gather towards the center or move away from the center.

[0011] The second housing guiding portion is a protruding portion extending towards the blade, and the second blade guiding portion is a strip-shaped groove. The protruding portion is inserted into the strip-shaped groove.

[0012] A first blade guiding portion is provided on the end face of the blade close to the first housing. A first housing guiding portion is provided on the end face of the first housing close to the blade. When the blade is in a moving state, the first blade guiding portion moves along the first housing guiding portion.

[0013] The first blade guiding portion is a convex block extending towards the first housing, and the first housing guiding portion is a groove. The convex block is inserted into the groove.

[0014] The blade includes a first surface and a second surface. Among adjacent two blades, at least part of the second surface of one blade is in contact with the first surface of the other blade.

[0015] It further includes a workbench, on the upper end surface of which there are installed a motor bracket and a shock tube bracket. The motor is installed on the motor bracket, and the shock tube is installed on the shock tube bracket. The two ends of the shock tube are respectively a connecting part one and a connecting part two, and the connecting part two is fixedly connected to the housing one.

[0016] The beneficial effects of the present invention are as follows:

[0017] First, it has a small floor area, low cost and good shock wave elimination effect, which can ensure the validity of test results.

[0018] Second, with the shock tube, the motor, and the mechanical iris structure (housing one, blades, housing two), the rarefaction wave can be effectively weakened, and the existence time of the stable air flow available for explosion research can be increased. The structure is simple, the operation is very convenient, the experimental cost is low, and the efficiency is high.

[0019] Third, there is no need to increase the length of the shock tube, saving costs.

[0020] Fourth, by using the shock wave reflected by the closed blades to interfere with the rarefaction wave generated by the reflection at the entrance of the shock tube end face, the attenuation effect of the rarefaction wave on the incident shock wave is weakened, thereby prolonging the steady flow time of the incident shock wave, that is, increasing the experimental time. Description of the Drawings

[0021] Figure 1 It is a perspective view of the first angle of the present invention (blade open state);

[0022] Figure 2 It is a perspective view of the second angle of the present invention (blade open state);

[0023] Figure 3 It is a partial perspective view of the present invention (blade closed state);

[0024] Figure 4 It is a partial explosion view of the present invention;

[0025] Figure 5 It is a top view of the present invention (removing the workbench);

[0026] Figure 6 It is a perspective view of the housing one of the present invention;

[0027] Figure 7 It is a perspective view of the blade of the present invention;

[0028] Figure 8 It is a perspective view of the housing two of the present invention;

[0029] Figure 9 It is a perspective view of the blade cooperating with the housing one of the present invention;

[0030] Figure 10 It is a schematic plan view of a shock tube with a diameter of 25.40 cm.

[0031] In the figure: gear 1, workbench 2, motor 3, shock tube 4, shock tube through-hole 41, connecting part 1 42, connecting part 2 43, shock tube support 44, housing 1 5, housing 1 guiding part 51, end face 1 511, end face 2 512, connecting block 52, block 1 521, block 2 522, housing 1 through-hole 53, housing 2 6, notch 61, housing 2 guiding part 62, tooth 63, housing 2 through-hole 64, blade 7, blade guiding part 1 71, side face 1 711, side face 2 712, blade guiding part 2 72, face 1 73, face 2 74, motor support 8. Specific implementation manner

[0032] The technical solution of the present invention will be further described below through embodiments in conjunction with the accompanying drawings.

[0033] As Figures 1 - 10 shown, a rarefaction wave elimination device includes a motor 3, a shock tube 4, a housing 1 5, a housing 2 6, a blade 7, and a workbench 2, and the workbench 2 plays a fixing role.

[0034] An upper end face of the workbench 2 is provided with a motor support 8 and a shock tube support 44. The motor 3 is installed on the motor support 8, and the shock tube 4 is installed on the shock tube support 44. The motor support 8 provides a supporting effect for the motor 3, and the motor 3 is a servo motor. The motor 3 and the motor support 8 are connected by a flange, and the motor support 8 and the workbench 2 are connected by bolts.

[0035] The shock tube 4 and the shock tube support 44 can be integrally formed or detachably connected.

[0036] An output end of the motor 3 is connected to the gear 1, and teeth 63 meshing with the gear 1 are provided on an outer wall of the housing 2 6. Through the cooperation of the gear 1 and the teeth 63, the motor 3 can drive the housing 2 6 to rotate around its own axis. The teeth 63 are not distributed over the entire outer wall of the housing 2 6.

[0037] The shock tube 4 is a straight tube structure with both ends open. Two ends of the shock tube 4 are respectively a connecting part 1 42 and a connecting part 2 43. A shock tube through-hole 41 is provided in a center of the shock tube 4. The connecting part 1 42 is an explosive gas inlet, and the connecting part 2 43 is connected to a mechanical iris mechanism (i.e., the housing 1 5, the housing 2 6, and the blade 7). The shock tube 4, the housing 1 5, the housing 2 6, and the blade 7 are coaxially distributed. Such a structure ensures that when the shock wave reaches an outlet of the shock tube 4 (i.e., the connecting part 2 43 end), each blade 7 starts to close under the drive of the housing 2 6, ensuring that shock waves in all directions are accelerated, thereby reducing the influence brought by rarefaction waves.

[0038] The shock tube 4 is connected to the first housing 5, and the second connecting part 43 is fixedly connected to the first housing 5. Specifically, the second connecting part 43 and the first housing 5 are connected by screws.

[0039] The second housing 6 is movably connected to the first housing 5. One end face of the first housing 5 facing the second housing 6 is provided with connecting blocks 52 extending towards the second housing 6. The number of connecting blocks 52 is two and they are symmetrically distributed. Each connecting block 52 includes a first block 521 and a second block 522. The second housing 6 includes two symmetrically distributed notches 61. The notches 61 are arc-shaped grooves. The first block 521 passes through the notch 61. When the second housing 6 rotates around its own axis, the first block 521 abuts against both ends of the notch 61, which are the two rotation limit positions of the second housing 6. The range of the teeth 63 is equivalent to the range of the notch 61. When the gear 1 is located at one end of the teeth 63, the first block 521 is located at one end of the notch 61. When the gear 1 is located at the other end of the teeth 63, the first block 521 is located at the other end of the notch 61. The range of the teeth 63 is the angle required for the blade 7 to be fully opened and fully closed.

[0040] The blade 7 is located between the first housing 5 and the second housing 6. One end face of the first housing 5 is in contact with one end face of the blade 7, and the other end face of the blade 7 is in contact with the second housing 6.

[0041] The second block 522 is located on the end face of the second housing 6 away from the first housing 5 and at least part of the second block 522 extends beyond the contour range of the notch 61. One end face of the second block 522 is in contact with the end face of the second housing 6. The second block 522 is located outside the first block 521, so the second block 522 is also located outside the notch 61. Since one end face of the second housing 6 is in contact with the blade 7 and the other end face of the second housing 6 is in contact with the second block 522, the axial displacement of the second housing 6 is restricted, and the second housing 6 can only rotate around its own axis.

[0042] The centers of the shock tube 4, the first housing 5, and the second housing 6 form a connected channel, which is the explosion gas channel. A through hole 53 of the first housing is provided at the center of the first housing 5. A through hole 64 of the second housing is provided at the center of the second housing 6. The through hole 41 of the shock tube, the through hole 53 of the first housing, and the through hole 64 of the second housing are connected to form a channel.

[0043] The number of blades 7 is multiple and they are circumferentially distributed around the axis of the second housing 6.

[0044] The motor 3 can drive the second housing 6 to rotate around the axis of the second housing 6 itself, and the rotation of the second housing 6 drives all the blades 7 to gather towards the center or move away from the center. When all the blades 7 gather towards the center, the channel area where the blades 7 are located gradually decreases until it is completely closed, that is, the blades 7 cut off the channel.

[0045] When all the blades 7 move away from the center, the channel area where the blades 7 are located gradually increases. The maximum can reach 100% opening, that is, the through hole 53 of the first housing is fully opened.

[0046] The flow rate of the passing air can be controlled by adjusting the closing degree of the blade 7, that is, the cross-sectional area ratio, and stepless adjustment can be achieved.

[0047] The motor 3, the shock tube 4, and the axis of the mechanical iris structure are in the same horizontal plane. During the operation of the motor 3, the angle sensor of the control system can collect the currently opened angle of the mechanical iris structure to adjust the next rotation speed.

[0048] One end surface of the second housing 6 close to the first housing 5 is provided with a second housing guiding part 62. One end surface of the blade 7 close to the second housing 6 is provided with a second blade guiding part 72. When the second housing 6 rotates around its own axis, the second housing guiding part 62 moves along the second blade guiding part 72 and drives all the blades 7 to gather towards the center or move away from it. The second housing guiding part 62 is a protruding part extending towards the blade 7, and the second blade guiding part 72 is a strip-shaped groove. The protruding part is inserted into the strip-shaped groove. A slide rail adapted to the blade 7 is arranged in the second housing 6 to provide a moving space for the blade 7 to slide and can limit the movement range of the blade 7 so that it is in a fully opened and fully closed state respectively at the beginning and end of the movement, that is, the blade 7 can be fully closed when gathering towards the center, and the blade 7 can be fully opened when moving away from the center.

[0049] One end surface of the blade 7 close to the first housing 5 is provided with a first blade guiding part 71. One end surface of the first housing 5 close to the blade 7 is provided with a first housing guiding part 51. When the blade 7 is in a moving state, the first blade guiding part 71 moves along the first housing guiding part 51. The first blade guiding part 71 is a convex block extending towards the first housing 5, and the first housing guiding part 51 is a groove. The convex block is inserted into the groove. A slide rail adapted to the blade 7 is arranged in the first housing 5 to provide a moving space for the blade 7 to slide and can limit the movement range of the blade 7 so that it is in a fully opened and fully closed state respectively at the beginning and end of the movement, that is, the blade 7 can be fully closed when gathering towards the center, and the blade 7 can be fully opened when moving away from the center.

[0050] Both ends of the first housing guiding part 51 are respectively an end surface one 511 and an end surface two 512. Among them, the end surface one 511 is an inclined end surface. Both ends of the first blade guiding part 71 are respectively a side surface one 711 and a side surface two 712. The side surface one 711 is an inclined end surface and matches the shape of the end surface one 511. During installation, it can be installed by aligning the side surface one 711 with the end surface one 511. When the blade 7 is in one of the limit positions, the side surface one 711 abuts against the end surface one 511.

[0051] The blade 7 includes a surface one 73 and a surface two 74. Among two adjacent blades 7, the surface two 74 of one blade 7 and the surface one 73 of the other blade 7 are at least partially attached. Among them, the length of the surface two 74 is less than the length of the surface one 73, so as to Figure 3In the state where, at this time, the second surface 74 of one blade 7 is completely attached to the first surface 73 of another blade 7, but there is still an unfilled part on the first surface 73 that has not been attached. Figure 3 The contour formed by all the blades 7 in this state can completely cover the through-hole 53 of the housing one.

[0052] Working principle of execution: Taking Figure 1 as a reference, when the shock wave reaches the end of the shock tube 4, the motor 3 starts to drive the gear 1 to rotate clockwise under the drive of a pre-set program. The housing two 6 rotates around its axis under the drive of the gear 1. When the housing two 6 rotates, it drives the blade 7 to slide. The blade 7 slides on the guiding part 51 of the housing one of the housing one 5, and the blade 7 has a movement along the tangential direction of the inner circle. During this process, each blade 7 approaches the center of the inner circle, and the cross-sectional area (i.e., the channel) enclosed by all the blades 7 continuously shrinks, that is, the RWE cross-sectional area ratio (blade opening area / shock tube cross-sectional area) continuously becomes smaller. When the RWE continuously becomes smaller, the air flow passing through this cross-sectional area is continuously accelerated, and during this process, the RWE is always maintained to change according to a pre-calculated target value. With the change of the air flow, the RWE continuously changes to meet the continuously changing air flow. When the air flow is accelerated to the target value, the rarefaction wave will no longer be generated.

[0053] Principle of using RWE: The purpose of using RWE is to eliminate or suppress the wave generated when the shock wave leaves the downstream end of the shock tube. It will not be used to deliberately generate shock waves or rarefaction waves to adjust the air flow in the test section.

[0054] To simplify the analysis, we made the following assumptions:

[0055] 1. Assume that the RWE is a convergent nozzle with an exit plane cross-sectional area that changes with time, and this convergent nozzle is installed at Figure 10 the end of the LB / TS extension part of Figure 10 the right end of (not shown in the figure).

[0056] 2. The flow will be considered one-dimensional.

[0057] 3. The interaction between the flow after the shock wave and the RWE is assumed to be isentropic. Entropy is generated when the gas is processed by the front shock wave, but the flow after the shock wave can be reasonably simulated as isentropic. Since shock waves appear during the explosion process, there is a very thin wave front separating the compressed fluid and the uncompressed fluid. There is a sudden jump in pressure from before the wave front to after the wave front. The flow after the shock wave refers to the flow of the gas behind the wave front, whose pressure, density, and flow velocity have changed; the front shock wave refers to the gas in front of the wave front, whose physical properties have not changed at this time and have not been affected yet.

[0058] 4. Assume that the flow is inviscid.

[0059] 5. Assume that the gas involved has the state equation of an ideal gas.

[0060] 6. Only consider the period when the gas flow leaves the shock tube; this analysis does not consider the case of the gas flowing back from the atmosphere into the shock tube.

[0061] The static pressure sensor is installed at Figure 10 the LB / TS extension part, specifically at the entrance of the RWE (not shown in the figure). The static pressure sensor is used to measure the pressure in the driver (the driver is installed at Figure 10 the driving end). Triggering the recording sequence and the RWE means recording the experimental time and the static pressure parameter at the entrance of the RWE.

[0062] Take the atmospheric pressure (P ∞ ) = 101.325 KPa, the specific heat ratio (γ) = 1.400. Equation (1) gives the method for calculating the shock wave Mach number M from the pressures before and after the wave front, where p i is the static pressure of the shock wave at the entrance of the RWE, p ∞ is the atmospheric pressure, and γ is the specific heat ratio.

[0063]

[0064] From the shock wave Mach number M, the Mach number M i of the gas flow behind the wave at the entrance of the RWE can be further obtained, and there is:

[0065]

[0066] Using the static pressure p i of the shock wave and the Mach number M i of the gas flow behind the wave to calculate the stagnation pressure, there is

[0067]

[0068] For the gas flow flowing into the RWE at subsonic speed, the critical pressure ratio shown in Equation (4) is given (where P 0i is the stagnation pressure, p ∞ is the atmospheric pressure, and γ is the specific heat ratio):

[0069]

[0070] When the specific heat ratio is 1.4, this critical value is 0.528282. To eliminate the rarefaction wave at the pipe orifice, the following two cases need to be considered: (1) If the pressure ratio of the flow is greater than the critical value, then adjust the RWE so that the static pressure of the gas flow when it flows out of the RWE is equal to the atmospheric pressure. At this time, the gas flow behind the wave can still remain subsonic, and its Mach number M e is given by Equation (5); (2) If the pressure ratio is less than the critical value, then adjust the RWE so that the flow becomes sonic (M e = 1) at the exit of the RWE.

[0071]

[0072] RWE cross-section ratio with Mach number M i is shown in Equation (6).

[0073]

[0074] For the simulation of the decaying blast wave, the static pressure and stagnation pressure at the RWE inlet vary with time. As long as these pressure histories are known, the RWE opening area history can be found by performing iterative calculations using Equations 2, 5, and 6.

[0075] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A rarefaction wave elimination device, characterized in that: It includes a motor (3), a shock tube (4), a first housing (5), a second housing (6), and blades (7). The shock tube (4) is connected to the first housing (5). The second housing (6) is concentrically distributed with the first housing (5) and the second housing (6) is movably connected to the first housing (5). A communicating channel is formed at the centers of the shock tube (4), the first housing (5), and the second housing (6). The blades (7) are located between the first housing (5) and the second housing (6). The number of blades (7) is multiple and they are circumferentially distributed around the axis of the second housing (6). The motor (3) can drive the second housing (6) to rotate around its own axis, and the rotation of the second housing (6) drives all the blades (7) to gather towards the center or move away from the center. When all the blades (7) gather towards the center, the channel area where the blades (7) are located gradually decreases until it is completely closed. When all the blades (7) move away from the center, the channel area where the blades (7) are located gradually increases.

2. The rarefaction wave elimination device according to claim 1, characterized in that: The output end of the motor (3) is connected to a gear (1). The outer wall of the second housing (6) is provided with teeth (63) meshing with the gear (1). Through the cooperation of the gear (1) and the teeth (63), the motor (3) can drive the second housing (6) to rotate around its own axis.

3. The rarefaction wave elimination device according to claim 1, characterized in that: A shock tube through hole (41) is provided at the center of the shock tube (4). A first housing through hole (53) is provided at the center of the first housing (5). A second housing through hole (64) is provided at the center of the second housing (6). The shock tube through hole (41), the first housing through hole (53), and the second housing through hole (64) communicate to form a channel.

4. The rarefaction wave elimination device according to claim 1, characterized in that: One end face of the first housing (5) facing the second housing (6) is provided with a connecting block (52) extending towards the second housing (6). The connecting block (52) includes a first block (521) and a second block (522). The second housing (6) includes a notch (61). The first block (521) passes through the notch (61). The second block (522) is located on one end face of the second housing (6) away from the first housing (5) and at least part of the second block (522) extends beyond the contour range of the notch (61).

5. The rarefaction wave elimination device according to claim 1, characterized in that: One end face of the second housing (6) close to the first housing (5) is provided with a second housing guiding part (62). One end face of the blade (7) close to the second housing (6) is provided with a second blade guiding part (72). When the second housing (6) rotates around its own axis, the second housing guiding part (62) moves along the second blade guiding part (72) and drives all the blades (7) to gather towards the center or move away from the center.

6. The rarefaction wave elimination device according to claim 5, characterized in that: The second housing guiding part (62) is a protruding part extending towards the blade (7). The second blade guiding part (72) is a strip-shaped groove. The protruding part is inserted into the strip-shaped groove.

7. The sparse wave elimination device according to claim 1, characterized in that: one end face of the blade (7) close to the first housing (5) is provided with a first blade guiding portion (71), one end face of the first housing (5) close to the blade (7) is provided with a first housing guiding portion (51), and when the blade (7) is in a moving state, the first blade guiding portion (71) moves along the first housing guiding portion (51).

8. The sparse wave elimination device according to claim 7, characterized in that: the first blade guiding portion (71) is a convex block extending towards the first housing (5), the first housing guiding portion (51) is a groove, and the convex block is inserted into the groove.

9. The sparse wave elimination device according to claim 1, characterized in that: the blade (7) includes a first surface (73) and a second surface (74), and in two adjacent blades (7), at least a part of the second surface (74) of one blade (7) is attached to the first surface (73) of the other blade (7).

10. The sparse wave elimination device according to claim 1, characterized in that: it further includes a workbench (2), a motor bracket (8) and a shock tube bracket (44) are installed on the upper end face of the workbench (2), the motor (3) is installed on the motor bracket (8), the shock tube (4) is installed on the shock tube bracket (44), two ends of the shock tube (4) are respectively a first connecting portion (42) and a second connecting portion (43), and the second connecting portion (43) is fixedly connected to the first housing (5).

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