阅读说明：本技术 一种防分离自由活塞 (Separation-preventing free piston ) 是由 廖振洋 钟涌 李理 张扣立 吕治国 常雨 孔荣宗 于 2019-12-04 设计创作，主要内容包括：本发明公开了一种防分离自由活塞。该防分离自由活塞的活塞本体是一个上游端面开口下游端面封闭的圆筒,圆筒的上游端和下游端分别加工有环形台阶轴,环形台阶轴内安装支撑环；支撑环与压缩管之间间隙配合；侧挡板分别安装在支撑环的外侧,通过螺钉固定在活塞本体上；缓冲头整体为台阶轴状,通过双头螺柱和螺母安装在安装活塞本体的下游端面；缓冲头的上游与压缩管之间为间隙配合,还加工有钩形槽组；缓冲头的下游外径与压缩管之间具有较大间隙；通过密封圈实现活塞本体与支撑环之间,支撑环与压缩管之间,活塞本体与缓冲头之间的密封。该防分离自由活塞结构简单,运行可靠,拆装方便,适用于活塞驱动的激波风洞、炮风洞和膨胀风洞。(The invention discloses a separation-preventing free piston. The piston body of the separation-preventing free piston is a cylinder with an opening on the upstream end surface and a closed downstream end surface, the upstream end and the downstream end of the cylinder are respectively processed with an annular step shaft, and a support ring is arranged in the annular step shaft; the support ring is in clearance fit with the compression pipe; the side baffles are respectively arranged on the outer sides of the support rings and are fixed on the piston body through screws; the buffer head is integrally in a step shaft shape and is arranged on the downstream end surface of the piston body through a stud and a nut; the upstream of the buffer head is in clearance fit with the compression pipe, and a hook-shaped groove group is also processed; a larger gap is formed between the downstream outer diameter of the buffer head and the compression pipe; sealing between the piston body and the support ring, between the support ring and the compression pipe, and between the piston body and the buffer head is realized through the sealing ring. The separation-preventing free piston is simple in structure, reliable in operation, convenient to disassemble and assemble and suitable for shock tunnels, cannon tunnels and expansion tunnels driven by pistons.)

1. The separation-preventing free piston is characterized by comprising a piston body (1), a sealing ring I (2), a support ring (3), a sealing ring II (4), a side baffle (5), a buffer head (6), a sealing ring III (7), a nut (8) and a stud (9);

piston body (1): the piston is a piston main body and is a cylinder with an upstream end surface opening and a downstream end surface being closed, the diameter of the cylinder is smaller than the inner diameter of the compression pipe, an annular step shaft is respectively processed at the upstream end and the downstream end of the cylinder, and a support ring (3) is arranged in the annular step shaft;

support ring (3): the number of the piston bodies is 2, the piston bodies are annular and are respectively arranged in annular step shafts at the upstream end and the downstream end of the piston body (1), and the support rings (3) are in clearance fit with the compression pipe and are used for supporting and positioning the piston body (1) and preventing the piston body (1) moving at high speed from directly contacting with the inner wall of the compression pipe;

side baffle (5): 2, the supporting rings are annular and are respectively arranged on the outer sides of the 2 supporting rings (3) and fixed on the piston body (1) through screws for preventing the supporting rings (3) from falling off;

buffer head (6): the whole body is in a step shaft shape and is arranged on the downstream end surface of the piston body (1) through a double-end stud (9) and a nut (8); the upstream of the buffer head (6) is in clearance fit with the compression pipe, and a hook-shaped groove group is also processed; the height of a gap between the downstream outer diameter of the buffer head (6) and the compression pipe is 2-10% of the diameter of the compression pipe;

seal ring i (2): 2, respectively arranged at the upstream of the piston body (1) and the downstream of the piston body (1) and used for sealing between the piston body (1) and the support ring (3);

seal ring ii (4): 2 support rings (3) are respectively arranged on the 2 support rings for sealing between the support rings (3) and the compression pipe;

seal ring iii (7): the number of the piston is 1, the piston is arranged on the downstream end face of the piston body (1) and used for sealing between the piston body (1) and the buffer head (6);

stud (9): 1, the buffer head (6) is arranged on the downstream end face of the piston body (1);

nut (8): the number of the buffer heads is 1, and the buffer heads (6) are matched with the double-end studs (9) and fixed on the downstream end surface of the piston body (1).

2. Anti-separation free piston according to claim 1, characterized in that the material of the piston body (1) is aluminium or alloy steel.

3. The separation-preventing free piston as claimed in claim 1, characterized in that the main body of the piston body (1) is provided with screw holes for hoisting the piston body (1); the upstream end face of the piston body (1) is provided with a screw hole for taking out the piston body (1) from the upstream end of the compression pipe in the case of failure.

4. Anti-separation free piston according to claim 1, characterised in that the material of the support ring (3) is a copper alloy.

5. The separation-preventing free piston as claimed in claim 1, wherein the material of the sealing rings I (2), II (4) and III (7) is rubber, carbon fiber or copper alloy.

6. Anti-separation free piston according to claim 1, characterized in that the stud (9) protrudes beyond the cushion head (6) for removal of the piston body (1) from the downstream end of the compression tube.

7. Anti-separation free piston according to claim 1, characterized in that the material of the damping head (6) is polyurethane.

8. The separation-preventing free piston as claimed in claim 1, wherein the set of hook-shaped grooves is a series of hook-shaped grooves distributed along the axis of the cushion head (6) upstream of the cushion head (6), the width of the bottom of the hook-shaped grooves is greater than the height of the hook-shaped grooves, the angle of the hook-shaped grooves is 45 ° to 80 °, the number of the hook-shaped grooves is n, and n is greater than or equal to 1.

Technical Field

The invention belongs to the technical field of hypersonic test equipment, and particularly relates to a separation-preventing free piston.

Background

In the operation process of impulse type wind tunnels with piston drivers, such as shock tunnels, cannon tunnels, expansion tunnels and the like driven by pistons, free pistons are generally accelerated, sharply decelerated, stopped and then accelerated in a compression pipe after being launched, and finally impact the bottom of the compression pipe at a certain speed to stop. In order to buffer the huge impact force generated by the free piston impacting the bottom of the compression pipe, an impact-resistant buffer material is arranged at the head of the free piston, and the buffer material is a common mode for absorbing the energy during collision. The buffering material is generally made of a super-elastic damping material, and because the physical property difference between the material of the piston body and the buffering material is huge, reliable connection is difficult to carry out, and the buffering material is very easy to separate from the piston body and fall off in the free piston motion process, particularly in the processes of rapid deceleration and rebound, so that test failure and even safety accidents are caused.

Disclosure of Invention

The invention aims to solve the technical problem of providing a separation-preventing free piston.

The separation-preventing free piston is characterized by comprising a piston body, a sealing ring I, a support ring, a sealing ring II, a side baffle, a buffer head, a sealing ring III, a nut and a stud;

a piston body: the piston is a piston main body and is a cylinder with an upstream end surface opening and a downstream end surface being closed, the diameter of the cylinder is smaller than the inner diameter of the compression pipe, an annular step shaft is respectively processed at the upstream end and the downstream end of the cylinder, and a support ring is arranged in the annular step shaft;

supporting the ring: the number of the piston bodies is 2, the piston bodies are annular and are respectively arranged in annular step shafts at the upstream end and the downstream end of the piston body, and the support rings are in clearance fit with the compression pipe and used for supporting and positioning the piston bodies and preventing the piston bodies moving at high speed from directly contacting with the inner wall of the compression pipe;

side baffle: 2 supporting rings are annular and are respectively arranged on the outer sides of the 2 supporting rings and fixed on the piston body through screws for preventing the supporting rings from falling off;

buffering head: the whole body is in a step shaft shape and is arranged on the downstream end surface of the piston body through a double-end stud and a nut; the upstream of the buffer head is in clearance fit with the compression pipe, and a hook-shaped groove group is also processed; the height of the gap between the downstream outer diameter of the buffer head and the compression pipe is 2-10% of the diameter of the compression pipe;

sealing washer I: 2, respectively arranged at the upstream of the piston body and the downstream of the piston body, and used for sealing between the piston body and the support ring;

and a sealing ring II: 2 support rings are respectively arranged on the 2 support rings and used for sealing between the support rings and the compression pipe;

and (3) sealing ring III: the number of the piston bodies is 1, the piston bodies are arranged on the downstream end face of the piston body and used for sealing between the piston body and the buffer head;

stud bolt: 1, mounting the buffer head on the downstream end surface of the piston body;

nut: and the number of the buffer heads is 1, and the buffer heads are matched with the double-end studs and fixed on the downstream end surface of the piston body.

The piston body is made of aluminum or alloy steel.

The main body of the piston body is provided with a screw hole for hoisting the piston body; the upstream end face of the piston body is provided with a screw hole for taking out the piston body from the upstream end of the compression pipe in case of a failure.

The material of the support ring is copper alloy.

The sealing ring I, the sealing ring II and the sealing ring III are made of rubber, carbon fiber or copper alloy.

The stud extends out of the cushion head for removal of the piston body from the downstream end of the compression tube.

The buffer head is made of polyurethane.

The hook-shaped groove group is a series of hook-shaped grooves distributed along the axis of the buffer head at the upstream of the buffer head, the width of the bottom of each hook-shaped groove is greater than the height of the hook-shaped groove, the angle of each hook-shaped groove is 45-80 degrees, the number of the hook-shaped grooves is n, and n is greater than or equal to 1.

The separation-preventing free piston is arranged in the compression pipe, before launching, a gas storage tank at the upstream of the free piston is filled with high-pressure driving gas, and a low-pressure compressed gas is filled at the downstream of the free piston. After the valve of the air storage tank at the upstream of the free piston is opened, high-pressure driving air in the air storage tank pushes the free piston to move in an accelerated way from the upstream to the downstream. As the free piston moves, the volume downstream of the free piston decreases, the pressure and temperature begin to increase, and the volume upstream of the free piston increases, and the pressure and temperature begin to decrease. When the downstream gas pressure of the free piston exceeds the upstream gas pressure, the free piston starts to decelerate sharply, but the downstream pressure of the free piston continues to rise, if the diaphragm positioned at the downstream of the compression pipe is broken normally, the gas at the downstream of the compression pipe flows out, the free piston impacts the bottom of the compression pipe at a certain speed, if the downstream diaphragm is not broken normally, the free piston decelerates to 0, reverses and accelerates sharply towards the upstream of the compression pipe, and then the free piston vibrates back and forth to dissipate energy. In the process that the free piston accelerates towards the downstream of the compression pipe, the piston body pushes the buffer head to move, and the separation trend does not exist between the piston body and the buffer head. When the free piston starts to decelerate, the pressure at the downstream of the free piston is higher, under the action of the pressure, the hook-shaped groove group at the upstream of the buffer head is opened, the self-tightening sealing between the buffer head and the inner wall of the compression pipe is realized, and meanwhile, the step at the downstream of the buffer head is expanded in the radial direction, so that the hook-shaped groove group is prevented from excessively deforming under the action of high pressure. The self-tightening seal between the buffer head and the inner wall of the compression pipe prevents high-temperature high-pressure gas at the downstream of the free piston from entering between the piston body and the buffer head, so that the free piston can always keep a compressed state between the piston body and the buffer head when rebounding at rapid deceleration and rapid acceleration, and the buffer head cannot fall off. When the free piston impacts the bottom of the compression pipe, the downstream of the buffering head is extruded and deformed to absorb the impact kinetic energy.

The piston body in the separation-preventing free piston is internally provided with the cavity, so that materials can be removed as required, and parameters such as the mass, the mass center and the like of the free piston can be adjusted.

The sealing ring II in the separation-preventing free piston is directly arranged on the support ring, so that the diameter of the piston body can be much smaller than the inner diameter of the compression pipe without influencing the sealing effect, and the piston body can be effectively prevented from scratching the inner wall of the compression pipe when the free piston moves at high speed and is violently impacted.

The buffer head in the separation-preventing free piston adopts a stepped shaft structure, the step at the upstream of the buffer head is matched with the inner wall of the compression pipe by adopting a small gap, high-pressure sealing is realized, a larger gap is reserved between the step at the downstream of the buffer head and the inner wall of the compression pipe, the buffer head is ensured to elastically deform after impacting the bottom of the compression pipe, the impact of the free piston on the bottom of the compression pipe is buffered, and the kinetic energy of the free piston is absorbed.

The hook-shaped groove group in the separation-preventing free piston can realize self-tightening sealing in a large pressure range.

The separation-preventing free piston has the advantages of simple structure, reliable operation and convenient assembly and disassembly, is suitable for the conditions of high speed of the free piston and high gas pressure after the free piston is compressed, and is particularly suitable for shock tunnels, cannon tunnels and expansion tunnels driven by the piston.

Drawings

Fig. 1 is a schematic view of the structure of the separation prevention free piston of the present invention.

In the figure, 1, a piston body 2, a sealing ring I3, a supporting ring 4, a sealing ring II 5, a side baffle 6, a buffer head 7, a sealing ring III 8, a nut 9 and a stud bolt.

Detailed Description

The present invention will be described in detail below with reference to the accompanying drawings and examples. The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention.