A gas piston assembly for an ultrahigh-pressure liquid-drive piston compressor

Abstract

The application relates to the technical field of compressors and discloses a gas piston assembly for an ultrahigh-pressure liquid-drive piston compressor, which comprises a gas piston body, a sealing element and a connecting element; the gas piston body comprises oppositely arranged first and second body parts, a cylindrical protruding part is arranged at the center of the end face of one side of the first body part, and the second body part is provided with a positioning insertion hole matched with the cylindrical protruding part at the center of the end face opposite to one side of the first body part; the sealing element comprises a plurality of first piston rings and a plurality of second piston rings, the plurality of first piston rings and the plurality of second piston rings are all sleeved on the cylindrical protruding part and are alternately arranged, and the first piston rings are arranged close to the end face of the first body part; the connecting element is used for connecting the first body part and the second body part together after the cylindrical protruding part is inserted into the positioning insertion hole; the combined piston ring is used for replacing the traditional pan piston structure for sealing, and can solve the sealing problem caused by the extremely high pressure and temperature under the ultrahigh-pressure working condition.

Description

Technical Field

[0001] This invention relates to the field of compressor technology, specifically a gas piston assembly for an ultra-high pressure hydraulically driven piston compressor. Background Technology

[0002] Hot isostatic pressing (HIP) is a process technology that integrates high temperature and high pressure. The heating temperature is typically 1000℃-2000℃, and the working pressure can reach 200MPa using high-temperature, high-pressure argon gas in a sealed container as the pressure transmission medium. Under the combined action of high temperature and high pressure, the workpiece is subjected to uniform pressure in all directions. Therefore, the processed products have high density, good uniformity, and excellent performance. This technology also features short production cycles, fewer processes, low energy consumption, and minimal material loss. HIP equipment mainly consists of a high-pressure vessel, a heating furnace, an ultra-high-pressure compressor, a vacuum pump, a cooling system, and a computer control system. The ultra-high-pressure compressor, which provides ultra-high-pressure argon gas, is the key component of the entire system. Traditional HIP equipment typically uses a non-oil-injected electro-hydraulic compressor with overpressure protection, shock absorption devices, and automatic adjustment components, capable of providing high-pressure gas up to 200MPa for HIP. Ultra-high pressure polyethylene (UHPE), also known as high-pressure low-density polyethylene, is produced by combining ethylene and low-pressure circulating gas in a pre-stage turbo compressor to 25-30 MPa, followed by compression to the reaction pressure (250 MPa-320 MPa) in a subsequent reciprocating UHPE compressor. The initiator (catalyst) is also preheated. The heat generated by the polymerization reaction can raise the temperature to a maximum of 330°C. In the UHPE production process, the UHPE reciprocating compressor is the core component, requiring it to achieve ultra-high exhaust pressure while ensuring the purity of the compressed medium to prevent contamination.

[0003] With the booming development of the hydrogen refueling station industry, liquid-driven piston compressors used in hydrogen refueling stations have received much attention. They use oil-free lubrication to ensure that the gas is not contaminated when compressed. They also have advantages such as simple structure, large pressure ratio, adaptability to high temperature and high pressure, frequent start-stop capability and convenient maintenance. They can be used as ultra-high pressure compressors in various industrial scenarios.

[0004] A hydraulically driven piston compressor is a new type of compression compressor where hydraulic oil drives a piston to move left and right, replacing the crank and connecting rod of a traditional reciprocating piston compressor. Currently, it is most commonly used in hydrogen refueling stations. Depending on the specifications of the refueling station, it can be divided into two discharge pressure levels: 45MPa and 90MPa. Its piston structure is usually designed for pressures below 100MPa, and the discharge temperature typically does not exceed 150℃. Figure 1As shown, the traditional hydraulically driven piston compressor piston assembly consists of a piston body (a), a support ring (b), a metal washer (c), a piston plug (d), a dirt-collecting ring (e), a dirt-collecting ring groove (f), and a retaining ring (g). In this design, the support ring maintains the piston's alignment with the cylinder's central axis, preventing tilting and increased friction. The piston plug is an annular structure with a V-groove containing a spring. During operation, high-pressure gas enters the V-groove and acts on the spring, causing it to expand radially. The spring force simultaneously presses the inner and outer walls of the piston plug against the surfaces of the piston and cylinder, achieving a seal through an interference fit. The dirt-collecting ring, installed in the dirt-collecting ring groove, collects impurities scraped from the cylinder surface, preventing contamination of the compressed gas. The retaining ring, located at the piston's front end, ensures that subsequent components do not shift axially.

[0005] If a liquid-driven piston compressor is to be used as an ultra-high pressure boosting device above 200MPa, facing extremely high exhaust pressures and exhaust temperatures of 200℃ or even 300℃, the traditional liquid-driven piston compressor's piston assembly has the following defects that prevent it from meeting the operating requirements. Firstly, the use of a one-piece machined piston body means that the size of the groove for installing the seal is completely fixed and cannot be adjusted. This fails to consider the thermal expansion caused by the high temperature under ultra-high pressure conditions; the seal will be squeezed by the groove due to thermal expansion, significantly affecting its service life. Secondly, the plug structure used cannot meet the ultra-high pressure of 200MPa. Excessive gas force will damage the plug and its metal gasket, failing to meet the sealing requirements. Thirdly, if... Figure 2 As shown, since axial positioning is achieved through a retaining ring, for a reciprocating piston compressor, there is still an expansion process after the gas is compressed. At this time, the pressure inside the cylinder drops sharply, while there may still be some high-pressure gas at the piston. For an ultra-high pressure hydraulically driven piston compressor, if a structure with a retaining ring is used, there will be a huge pressure difference between its two ends, which may break the retaining ring and cause a major risk. Summary of the Invention

[0006] The purpose of this invention is to provide a gas piston assembly for an ultra-high pressure hydraulically driven piston compressor, so as to solve the problem that the current gas piston assembly structure of hydraulically driven piston compressors cannot meet the sealing requirements caused by the extremely high pressure and temperature under ultra-high pressure conditions.

[0007] The technical solution of this invention is:

[0008] A gas piston assembly for an ultra-high pressure hydraulically driven piston compressor includes a gas piston body, a seal, and a connector. The gas piston body includes a first main body portion and a second main body portion disposed opposite to each other. A cylindrical protrusion is provided at the center of one end face of the first main body portion, and a positioning insertion hole matching the cylindrical protrusion is provided at the center of the end face of the second main body portion opposite to the first main body portion. The seal includes multiple first piston rings and multiple second piston rings, all of which are sleeved on the cylindrical protrusion. The multiple first piston rings and multiple second piston rings are arranged alternately. The first piston ring is disposed near the end face of the first main body. The outer diameter of the first piston ring matches the inner diameter of the cylinder. The inner diameter of the first piston ring is larger than the diameter of the cylindrical protrusion. The outer diameter of the second piston ring is smaller than the outer diameter of the first piston ring. The inner diameter of the second piston ring matches the diameter of the cylindrical protrusion. The connector is used to connect the first main body and the second main body together after the cylindrical protrusion is inserted into the positioning hole, and the axial distance between the facing end faces of the first main body and the second main body is greater than the overall length of the seal formed by the plurality of first piston rings and the plurality of second piston rings.

[0009] Preferably, as a further improvement of the present invention, the connecting member includes a gas piston connecting bolt, the end of the second main body facing away from the groove is provided with a threaded through hole penetrating the groove, the end of the cylindrical protrusion facing the threaded through hole is provided with a threaded blind hole, and the gas piston connecting bolt is threadedly connected between the threaded through hole and the threaded blind hole.

[0010] Preferably, as a further improvement of the present invention, a metal washer is fitted onto the cylindrical protrusion, and the metal washer is disposed between the first main body and the first piston ring closest to the first main body.

[0011] Preferably, as a further improvement of the present invention, the end face of the metal washer facing the first body is a plane, the other end face of the metal washer is an inclined plane, the end face of the first piston ring facing the metal washer is an inclined plane, and the other end face of the first piston ring is a plane.

[0012] Preferably, as a further improvement of the present invention, the degree of the obtuse angle formed by the inclined surface of the metal washer and the cylindrical protrusion is less than the degree of the obtuse angle formed by the inclined surface of the first piston ring and the cylindrical protrusion.

[0013] Preferably, as a further improvement of the present invention, support rings are provided on the outer walls of both the first main body and the second main body.

[0014] Preferably, as a further improvement of the present invention, the material of each of the first piston rings and the material of the second piston rings are both high-temperature resistant and wear-resistant organic polymer materials.

[0015] Compared with the prior art, the beneficial effects of the present invention are:

[0016] 0. The traditional one-piece piston body is designed as a separable first body part and second body part. The two body parts are assembled with concave and convex parts to form an annular mounting space. The annular mounting space is equipped with a sealing element composed of multiple first piston rings and multiple second piston rings. The sealing element composed of multiple first piston rings and multiple second piston rings replaces the traditional piston structure for sealing. It can be used in ultra-high pressure hydraulically driven piston compressors with temperatures of 200℃-300℃ and pressures exceeding 200MPa. The sealing element composed of first piston rings and second piston rings with different diameters can simultaneously seal the inner wall of the cylinder and the outer wall of the piston.

[0017] 1. The connecting parts are designed to provide a certain space for the seal after the first main body and the second main body are connected as a whole, so as to prevent the seal composed of multiple first piston rings and multiple second piston rings from being damaged due to thermal expansion at high temperature.

[0018] 2. The new piston does not require a retaining ring for axial positioning, thus avoiding the problem of the retaining ring breaking. Attached Figure Description

[0019] Figure 1 This is a structural diagram of the gas piston assembly in a liquid-driven piston compressor in an existing technical solution.

[0020] Figure 2 This is a schematic diagram of the force applied to the retaining ring during the expansion process of gas inside the cylinder in the existing technical solution.

[0021] Figure 3 This is a schematic diagram of the structure of a gas piston assembly for an ultra-high pressure hydraulically driven piston compressor according to the present invention.

[0022] Figure 4 for Figure 3 A magnified view of part A in the diagram.

[0023] Figure 5 This is a schematic diagram of the installation of a gas piston assembly for an ultra-high pressure hydraulically driven piston compressor according to the present invention.

[0024] Figure 6 This is a schematic diagram of the sealing process in the gas piston assembly of an ultra-high pressure hydraulically driven piston compressor according to the present invention. Detailed Implementation

[0025] The following is in conjunction with the appendix Figure 3 To the attached Figure 6The specific embodiments of the present invention will be described in detail below. In the description of the invention, it should be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0026] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature; in the description of the invention, unless otherwise stated, "a plurality of" means two or more.

[0027] Example

[0028] like Figures 3 to 6 As shown, this embodiment of the invention provides a gas piston assembly for an ultra-high pressure hydraulically driven piston compressor, including a gas piston body, a seal, and a connector. The gas piston body includes a first main body portion 1 and a second main body portion 2 disposed opposite to each other. A cylindrical protrusion 11 is provided at the center of one end face of the first main body portion 1, and a positioning insertion hole 21 matching the cylindrical protrusion 11 is provided at the center of the end face of the second main body portion 2 opposite to the first main body portion 1. The seal includes a plurality of first piston rings 3 and a plurality of second piston rings 4, all of which are sleeved on the cylindrical protrusion 11. The plurality of first piston rings 3 and the plurality of second piston rings 4 interlock. The piston rings are arranged in a staggered pattern, with the first piston ring 3 positioned close to the end face of the first main body 1. The outer diameter of the first piston ring 3 matches the inner diameter of the cylinder, and the inner diameter of the first piston ring 3 is larger than the diameter of the cylindrical protrusion 11. The outer diameter of the second piston ring 4 is smaller than the outer diameter of the first piston ring 3, and the inner diameter of the second piston ring 4 matches the diameter of the cylindrical protrusion 11. A connector is used to connect the first main body 1 and the second main body 2 together after the cylindrical protrusion 11 is inserted into the positioning hole 21, and the axial distance between the opposite end faces of the first main body 1 and the second main body 2 is greater than the overall length of the seal formed by the plurality of first piston rings 3 and the plurality of second piston rings 4.

[0029] In this embodiment, the traditional one-piece piston body is designed as a separable first main body 1 and second main body 2. The two main body parts are fitted together with concave and convex joints to form an annular mounting space. A sealing element composed of multiple first piston rings 3 and multiple second piston rings 4 is installed in the annular mounting space. By setting the outer diameter of the first piston ring 3 to match the inner diameter of the cylinder, and setting the inner diameter of the first piston ring 3 to be larger than the diameter of the cylindrical protrusion 11, during operation, due to thermal expansion, the outer wall surface of the first piston ring 3 forms an interference fit with the inner wall surface of the cylinder to achieve a seal. By setting the outer diameter of the second piston ring 4 to be smaller than the outer diameter of the first piston ring 3, and setting the inner diameter of the second piston ring 4 to match the diameter of the cylindrical protrusion 11, during operation, due to thermal expansion, the second piston ring 4 forms an interference fit with the inner wall surface of the cylinder to achieve a seal. The inner wall surface of ring 4 and the outer wall surface of the cylindrical protrusion 11 of the first main body 1 form an interference fit to achieve sealing. Multiple first piston rings 3 and multiple second piston rings 4 are arranged alternately in the direction away from the end face of the first main body 1, with the first piston ring 3 followed by the second piston ring 4, so that each pair forms a sealing pair, which can simultaneously achieve sealing of the inner wall surface of the cylinder and the outer wall surface of the piston. Considering the reasons for seal failure, the present invention adopts multiple sealing pairs. After the previous sealing pair fails, the subsequent sealing pair can continue to work, which greatly improves the service life of the seal and reduces the operation and maintenance cost of the compressor. The connecting parts can reserve a certain space for the seal after the first main body and the second main body are connected into one, so as to prevent the combined piston ring from being damaged by thermal expansion at high temperature.

[0030] Specifically, the connector includes a gas piston connecting bolt 5. The end of the second main body 2 facing away from the groove has a threaded through hole penetrating the groove, and the end of the cylindrical protrusion facing the threaded through hole has a threaded blind hole. The gas piston connecting bolt 5 is threaded between the threaded through hole and the threaded blind hole. By adjusting the depth of the gas piston connecting bolt 5 screwed into the threaded blind hole of the first main body 1 when connecting the first main body 1 and the second main body 2, the axial distance between the end faces of the first main body 1 and the second main body 2 can be adjusted accordingly, thus reserving the required space.

[0031] Furthermore, in order to prevent the first piston ring 3 from contacting the end face of the first main body 1 and causing damage, a metal washer 6 is fitted on the cylindrical protrusion 11. The metal washer 6 is located between the first main body 1 and the first piston ring 3 closest to the first main body 1. The outer diameter of the metal washer 6 is the same as the outer diameter of the second piston ring 4, forming a gap between it and the cylinder wall at room temperature.

[0032] In another embodiment of the present invention, in order to improve the pressure bearing capacity, the end face of the metal washer 6 facing the first body 1 is set as a plane, and the other end face of the metal washer 6 is set as a slope. The end face of the first piston ring 3 facing the metal washer 6 is set as a slope, and the other end face of the first piston ring 3 is set as a plane. Through the above settings, the surfaces in contact with the metal washer 6 and the first piston ring 3 are all designed with slopes. The function of the slope is to increase the force-bearing area and improve the pressure bearing capacity.

[0033] Furthermore, the degree of the obtuse angle formed by the inclined surface of the metal washer 6 and the cylindrical protrusion 11 is less than the degree of the obtuse angle formed by the inclined surface of the first piston ring 3 and the cylindrical protrusion 11. This setting makes the inclined surface angle of the metal washer 6 slightly smaller than the inclined surface angle of the first piston ring 3. In specific implementation, the two angles differ by 1°. Through the above setting, it is convenient to automatically align the center and ensure that the central axes of the two coincide, preventing the cylinder inner wall or piston outer wall from being squeezed due to the deviation of the central axis.

[0034] In another embodiment of the present invention, support rings 7 are provided on the outer walls of the first main body 1 and the second main body 2. The two support rings 7 can ensure that the piston is kept horizontal in the cylinder, and prevent it from tilting, which would lead to increased friction and reduced service life.

[0035] In another embodiment of the present invention, each of the first piston ring 3 and the second piston ring 4 is made of a high-temperature resistant and wear-resistant organic polymer material.

[0036] Among them, PTFE (polytetrafluoroethylene) can be selected as the wear-resistant organic polymer material, which has the advantages of high temperature resistance, low coefficient of friction, good weather resistance, long aging life and non-adhesion.

[0037] Among them, wear-resistant organic polymer materials can also be selected from PEEK (polyether ether ketone), which has the advantages of high temperature resistance, excellent mechanical properties, rigidity and flexibility, self-lubrication, low coefficient of friction, excellent fatigue resistance under alternating stress, flame retardancy (self-extinguishing) and easy processing.

[0038] Among them, wear-resistant organic polymer materials can also be selected from PI (polyimide), which has the advantages of high temperature resistance, excellent thermal stability, excellent mechanical properties, and self-extinguishing properties.

[0039] In specific applications, PEEK (polyether ether ketone) is preferred as the processing material for the first piston ring 3 and the second piston ring 4. This is because the piston rings in the ultra-high pressure hydraulic piston compressor are subjected to alternating load conditions of high temperature and high pressure, which places high demands on the material's high temperature resistance, mechanical properties, and fatigue resistance under alternating stress. At the same time, its low friction and self-lubricating properties can effectively improve service life, its easy processing facilitates product manufacturing, and its flame retardancy makes it suitable for use in environments with dangerous gases such as hydrogen.

[0040] The assembly process of the gas piston assembly of the present invention is as follows: Figure 5 As shown, during assembly, firstly, the metal washer 6 is fitted onto the cylindrical protrusion 11, with its beveled end facing away from the first main body 1. Then, the first piston ring 3 with its beveled surface is fitted onto the cylindrical protrusion 11, forming a fit with the beveled surface of the metal washer 6. Next, the second piston ring 4 is fitted. Then, four sets are installed sequentially in the order of first piston ring 3 followed by second piston ring 4 to form piston ring seals. After the piston ring seals are installed, the second main body 2 is installed. The cylindrical protrusion 11 is inserted into the insert 21, and the piston connecting bolt 5 is tightened to connect the first main body 1 and the second main body 2 together. Finally, the support rings 7 are installed on the annular grooves on the outer walls of the first main body 1 and the second main body 2, respectively, completing the overall installation of the piston assembly. After installation, the assembly is as follows: Figure 3 As shown, the axial distance between the two end faces of the first main body 1 and the second main body 2 can be adjusted by adjusting the depth of the piston connecting bolt 5 screwed into the threaded blind hole, so that a certain gap is still left after the piston ring seal is installed. The reason is that: due to the high pressure ratio during operation of the ultra-high pressure hydraulic piston compressor, the gas will generate a lot of heat when compressed to high pressure. At the same time, in order to withstand extremely high pressure, the cylinder wall of the ultra-high pressure hydraulic piston compressor is very thick, resulting in weak thermal conductivity. Therefore, the temperature inside the cylinder during operation is much higher than that under normal operating conditions. In order to address the above problems, this invention abandons the traditional piston structure and uses a special piston ring structure designed with high-temperature resistant organic polymer materials. The first piston ring adopts a metal washer with a beveled fit, which can withstand higher pressure. Then, multiple piston rings in succession form a seal, which can ensure that the first piston ring can still play a sealing role when it fails. At the same time, the piston ring and the metal washer will thermally expand under high-temperature conditions. Therefore, the piston connecting bolt 5 needs to be adjusted to leave a certain gap between the piston body and the piston ring seal to allow space for thermal expansion and prevent damage. Because the piston ring assembly undergoes thermal expansion within the cylinder, its radial dimension is constrained by the cylinder inner wall and the piston outer wall. Therefore, the expansion can be considered as linear axial expansion, when the temperature change is Δ. T Hourly expansion Δ L Calculate according to the following formula:

[0041] .

[0042] In the formula, Δ L It is a linear expansion amount. is the average linear expansion coefficient of metallic materials. is the average linear expansion coefficient of the piston ring material. L 1 represents the initial axial length of the inclined metal washer 6. L 2 represents the initial axial length of the remaining piston ring assembly.

[0043] Based on the above calculations, the actual parameters can be substituted to obtain the value of thermal expansion. During installation, the corresponding space can be reserved by adjusting the connecting bolt 5 of the air piston.

[0044] The above-disclosed embodiments are merely preferred embodiments of the present invention. However, the embodiments of the present invention are not limited thereto, and any variations that can be conceived by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. A gas piston assembly for an ultra-high pressure hydraulically driven piston compressor, characterized in that, include: The air piston body includes a first main body (1) and a second main body (2) arranged opposite to each other. A cylindrical protrusion (11) is provided at the center of one side end face of the first main body (1), and a positioning hole (21) matching the cylindrical protrusion (11) is provided at the center of the end face of the second main body (2) facing the first main body (1). The sealing element includes multiple first piston rings (3) and multiple second piston rings (4). The multiple first piston rings (3) and multiple second piston rings (4) are all sleeved on the cylindrical protrusion (11). The multiple first piston rings (3) and multiple second piston rings (4) are arranged alternately. The first piston rings (3) are located close to the end face of the first main body (1). The outer diameter of the first piston ring (3) matches the inner diameter of the cylinder. The inner diameter of the first piston ring (3) is larger than the diameter of the cylindrical protrusion (11). The outer diameter of the second piston ring (4) is smaller than the outer diameter of the first piston ring (3). The inner diameter of the second piston ring (4) matches the diameter of the cylindrical protrusion (11). A connector is used to connect the first main body (1) and the second main body (2) together after the cylindrical protrusion (11) is inserted into the positioning hole (21), and to make the axial distance between the opposite end faces of the first main body (1) and the second main body (2) greater than the overall length of the seal formed by the plurality of first piston rings (3) and the plurality of second piston rings (4).

2. The gas piston assembly for an ultra-high pressure hydraulically driven piston compressor according to claim 1, characterized in that, The connector includes a gas piston connecting bolt (5), the second main body (2) has a threaded through hole through the groove at the end opposite to the groove, the cylindrical protrusion has a threaded blind hole at the end opposite to the threaded through hole, and the gas piston connecting bolt (5) is threaded between the threaded through hole and the threaded blind hole.

3. The gas piston assembly for an ultra-high pressure hydraulically driven piston compressor according to claim 1, characterized in that, A metal washer (6) is fitted on the cylindrical protrusion (11), and the metal washer (6) is disposed between the first main body (1) and the first piston ring (3) closest to the first main body (1).

4. The gas piston assembly for an ultra-high pressure hydraulically driven piston compressor according to claim 3, characterized in that, The end face of the metal washer (6) facing the first main body (1) is a plane, and the other end face of the metal washer (6) is an inclined plane. The end face of the first piston ring (3) facing the metal washer (6) is an inclined plane, and the other end face of the first piston ring (3) is a plane.

5. The gas piston assembly for an ultra-high pressure hydraulically driven piston compressor according to claim 4, characterized in that, The degree of the obtuse angle formed by the inclined surface of the metal washer (6) and the cylindrical protrusion (11) is less than the degree of the obtuse angle formed by the inclined surface of the first piston ring (3) and the cylindrical protrusion (11).

6. The gas piston assembly for an ultra-high pressure hydraulically driven piston compressor according to claim 1, characterized in that, Support rings (7) are provided on the outer walls of the first main body (1) and the second main body (2).

7. The gas piston assembly for an ultra-high pressure hydraulically driven piston compressor according to any one of claims 2-6, characterized in that, The materials of the first piston ring (3) and the second piston ring (4) are both high-temperature resistant and wear-resistant organic polymer materials.

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