High-pressure heavy-load piston compressor for supercritical carbon dioxide and working method thereof

Abstract

The invention relates to a high-pressure heavy-load piston compressor for supercritical carbon dioxide and a working method of the high-pressure heavy-load piston compressor. The high-pressure heavy-load piston compressor comprises a compressor body, a driving motor and a compressor shell. The compressor body comprises a plurality of air cylinders, each air cylinder comprises an air cylinder body and an air cylinder cover which are sequentially arranged from bottom to top, a compression chamber is arranged in each air cylinder body, a piston is arranged in each compression chamber, an exhaust cavity located at the top of each compression chamber is formed in each air cylinder cover, and each piston comprises a main piston matched with the corresponding compression chamber to work. The upper end of the main piston is provided with an auxiliary piston which protrudes upwards and can stretch into the exhaust cavity when the piston moves to the upper dead center, and the auxiliary piston is of a smooth curved surface structure. By optimizing the auxiliary piston, the motion resistance of the piston is reduced, the efficiency of the compressor is improved, and the failure risk of the auxiliary piston is reduced; the larger width of the bearing bush can stably transmit larger piston force, and abrasion of a connecting pair can be reduced, so that the service life of the bearing bush is prolonged, the capacity of the connecting rod for resisting toppling moment is improved, and an air cylinder operates more stably.

Description

Technical Field

[0001] The invention relates to the field of gas compressors, in particular to a high-pressure heavy-load piston compressor for supercritical carbon dioxide and a working method thereof. Background Art

[0002] Supercritical carbon dioxide is the state of carbon dioxide gas after its temperature and pressure exceed the critical value after high-pressure compression. Due to its physical properties such as high density and low viscosity, which are completely different from conventional fluids, supercritical carbon dioxide has become an ideal heat exchange medium for advanced refrigeration, heat pumps, hot water and other systems. In order to compress carbon dioxide to a supercritical state, the compressor faces the test of high pressure, high temperature and heavy load, and an efficient and highly reliable high-pressure and heavy-load piston compressor is indispensable.

[0003] There is an exhaust cavity between the exhaust valve and the top surface of the cylinder of the piston compressor, which reduces the compression ratio of the compressor. For high-pressure and heavy-load compressors, the exhaust cavity will cause a large efficiency loss. The current improvement method is to set a protrusion structure on the top of the piston to reduce the compression efficiency loss, but under high pressure and high temperature conditions, it will cause greater flow resistance and concentration of temperature and stress fields, affecting the efficiency and life of the compressor.

[0004] The piston in a high-pressure, heavy-load compressor is subjected to large forces and complex stress states. To ensure the stable operation of the piston, a reliable connection between the connecting rod and the crankshaft is essential. The rotary connection between the connecting rod and the crankshaft not only bears huge piston forces, but also needs to resist the tipping torque caused by the unbalanced force on the piston. The traditional low-journal rotary connection is difficult to suppress the swing of the connecting rod and piston under high pressure and heavy load, which can easily cause compressor vibration and affect the working efficiency and service life of the compressor.

[0005] The pressure of the cylinder of a high-pressure, heavy-duty compressor is extremely high, and the inner wall of the cylinder is under tremendous pressure and friction, which leads to severe wear. In traditional piston compressors, the inner wall of the cylinder and the cylinder body are an integrated structure. When wear occurs, this structure means that the entire cylinder structure needs to be replaced, which increases the complexity and cost of maintenance. On the other hand, in order to reduce the wear on the inner wall of the cylinder, more wear-resistant materials are needed, which increases the manufacturing cost of the traditional integrated cylinder structure. Therefore, when designing and manufacturing high-pressure, heavy-duty compressors, how to ensure the durability of the cylinder while controlling costs has become a problem that needs to be solved urgently. Summary of the invention

[0006] In view of this, the object of the present invention is to provide a high-pressure, heavy-duty piston compressor for supercritical carbon dioxide and a working method thereof, so as to reduce the resistance of piston movement, improve the efficiency of the compressor, and achieve high-pressure, high-temperature, high-efficiency and stable gas compression.

[0007] The present invention is implemented by the following scheme: a high-pressure heavy-load piston compressor for supercritical carbon dioxide, including a compressor body, a drive motor and a compressor housing; the compressor body includes a plurality of cylinders, the cylinders include a cylinder body and a cylinder head arranged in sequence from bottom to top, a compression chamber is provided in the cylinder body, a piston is provided in the compression chamber, an exhaust cavity located at the top of the compression chamber is provided on the cylinder head, the piston includes a main piston working in cooperation with the compression chamber, an auxiliary piston is provided at the upper end of the main piston, which protrudes upward and can extend into the exhaust cavity when the piston runs to the top dead center, and the auxiliary piston is a smooth curved surface structure.

[0008] Furthermore, the upper end of the auxiliary piston is provided with an upwardly raised curved top, and the lower peripheral side of the auxiliary piston is provided with a neck portion, and the curved top and the neck portion are transitionally connected by an arc-shaped drum portion.

[0009] Furthermore, the vertical cross-sectional contour line of the attached piston is a curve, including a top windward section, side necking sections on both sides and side transition sections on both sides, and the top windward section, side necking section and side transition section are connected in sequence from top to bottom.

[0010] Furthermore, the upper end of the vertical section contour line of the main piston has a top surface flat section located on both sides of the vertical section contour line of the auxiliary piston, the inner end point of the top surface flat section is connected to the lower end point of the side transition section, and the outer end point of the top surface flat section is connected to the upper edge line of the side of the main piston.

[0011] Furthermore, a cylinder sleeve is detachably sleeved in the compression chamber, the main piston of the piston is slidably matched with the cylinder sleeve, an annular groove is provided on the periphery of the main piston, and a sealing ring is provided in the annular groove.

[0012] Furthermore, a flange portion is provided on the outer peripheral side of the upper end of the cylinder sleeve, and an annular mounting groove matching the flange portion is provided on the peripheral side of the upper end of the compression chamber.

[0013] Furthermore, the main shaft of the driving motor is coaxially connected to the crankshaft through a coupling; a connecting rod assembly is provided under the piston, and the connecting rod assembly includes a connecting rod body whose small head end is hinged to the main piston of the piston through a piston pin, and a seat sleeve fixedly connected to the large head end of the connecting rod body, and a bearing bushing that rotatably cooperates with the connecting rod journal on the crankshaft is nested in the seat sleeve.

[0014] Furthermore, the axial width of the seat sleeve is consistent with the axial width of the bearing shell, the axial width of the bearing shell is 2 to 8 times the thickness of the connecting rod body, and the axial width of the bearing shell is greater than the diameter of the bearing shell.

[0015] Furthermore, the cylinder head is provided with an air inlet located at the top of the compression chamber, the air inlet is provided with an air inlet valve, an air inlet pipe connected to the air inlet and an exhaust pipe connected to the exhaust cavity are provided above the cylinder, and an exhaust valve is provided at the upper opening of the exhaust cavity.

[0016] Another technical solution of the present invention: a working method of a high-pressure heavy-load piston compressor for supercritical carbon dioxide as described above, when the main piston is at the top dead center position, the exhaust valve is closed and the intake valve is opened, and then during the main piston running from the top dead center to the bottom dead center, the volume of the compression chamber gradually increases, and carbon dioxide gas enters the compression chamber from the air inlet, and when the main piston runs to the bottom dead center position, the intake valve is closed to complete the intake process; the main piston moves from the bottom dead center to the top dead center, the volume of the compression chamber becomes smaller, and the compression process is completed, the carbon dioxide gas is compressed in the compression chamber, and the exhaust valve is opened after reaching a certain pressure, and the compressed carbon dioxide gas is discharged from the compression chamber to the exhaust pipe, and then the exhaust valve is closed to complete the exhaust process.

[0017] Compared with the prior art, the present invention has the following beneficial effects: (1) By optimizing the attached piston and designing it into a smooth curved surface structure, on the one hand, the resistance of piston movement is reduced and the efficiency of the compressor is improved; on the other hand, the temperature concentration and stress concentration on the top of the piston under high temperature and high pressure conditions are alleviated, reducing the failure risk of the attached piston; (2) The larger bearing width increases the contact area between the connecting rod and the crankshaft, and reduces the contact pressure between the connecting rod and the crankshaft. It can not only stably transmit a larger piston force, but also reduce the wear of the connecting pair, thereby increasing the bearing life, improving the ability of the connecting rod to resist the tipping torque, making the cylinder run more smoothly, thereby reducing the vibration of the compressor and improving the dynamic performance of the compressor; (3) The removable and replaceable cylinder liner improves the wear resistance of the cylinder inner surface and reduces maintenance costs.

[0018] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below through specific embodiments and related drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a cross-sectional view of a compressor according to an embodiment of the present invention; Figure 2 is a schematic diagram of a connecting rod assembly according to an embodiment of the present invention; Figure 3 is a schematic diagram of a cylinder liner according to an embodiment of the present invention; Figure 4 is a three-dimensional diagram of a piston with the piston located at the center in an embodiment of the present invention; Figure 5 is a graph of the contour of the auxiliary piston in the embodiment of the present invention, in which the auxiliary piston is located at the center; Figure 6 is a graph of the contour of the attached piston of an embodiment of the present invention when the attached piston is off-center; Figure 7is a piston profile curve diagram of an embodiment of the present invention in which the piston cross section is non-circular; DETAILED DESCRIPTION

[0020] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0021] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0022] like Figures 1 to 7 As shown, a high-pressure heavy-duty piston compressor for supercritical carbon dioxide includes a compressor body 10, a drive motor 20 and a compressor housing 30; the compressor body 10 includes a plurality of cylinders, the cylinders include a cylinder body 104 and a cylinder head 106 arranged in sequence from bottom to top, wherein the cylinder body 25 is the main structure of the cylinder and is an integral structure with the compressor housing; a compression chamber is provided in the cylinder body 110, a piston 110 is provided in the compression chamber, an exhaust cavity 121 located at the top of the compression chamber is provided on the cylinder head 106, the piston 104 includes a main piston 111 that cooperates with the compression chamber, an auxiliary piston 112 that protrudes upward at the upper end of the main piston and can extend into the exhaust cavity when the piston runs to the top dead center, and the auxiliary piston 112 is a smooth curved surface structure. The center line of the auxiliary piston can be consistent with the center line of the main piston, or it can be inconsistent with the center line of the main piston, that is, it deviates from the center position. When the piston runs to the top dead center, the auxiliary piston extends into the exhaust cavity formed by the bottom surface of the cylinder head and the exhaust valve, thereby improving the compression efficiency of the compressor. The attached piston 112 is a complete smooth curved surface. On the one hand, the smooth windward surface structure reduces the resistance of the piston movement and improves the efficiency of the compressor; on the other hand, the smooth curved surface reduces the temperature concentration and stress concentration at the top of the piston under high temperature and high pressure conditions, reduces the failure risk of the attached piston 112, and extends the service life of the piston to achieve high-pressure, high-temperature, high-efficiency, and stable gas compression. The compressor can be used for gas compression of different displacements, and can be used in high-efficiency refrigeration, heat pumps, and hot water systems. The number of cylinders included in the compressor body is an integer greater than or equal to 1, and the number of cylinders in this embodiment is 3.

[0023] The cross-sectional shape (i.e., the cross section) in the direction perpendicular to the center line of the attached piston can be circular (e.g. Figure 4 ) or other closed figures, such as an ellipse or parallelogram (as shown in Figure 7 ). The crank-connecting rod-piston mechanism and the intake-exhaust mechanism of the piston compressor are often asymmetric structures. When facing the stringent requirements of structural stress and exhaust gas flow, the curved surface of the attached piston 112 can be designed as a closed surface with a non-circular cross section. The aerodynamic force generated by the curved surface of the attached piston 112 during movement can improve the dynamic characteristics of the piston and reduce the vibration of the compressor. The curved surface of the attached piston 112 can also improve the flow state of the exhaust gas flow.

[0024] In this embodiment, the vertical cross-sectional contour line of the attached piston 112 is a curve, including a top windward section 14, side necking sections 15 on both sides, and side transition sections 16 on both sides. The top windward section 14, the side necking section 15, and the side transition section 16 are connected in sequence from top to bottom; that is, the upper end point of the side transition section 16 is connected to the lower end point of the side necking section 15, and the lower end points on both sides of the top windward section 14 are respectively connected to the upper end points of the side necking sections 15 on both sides. The curves of the attached piston 11 are connected to each other to form a complete curve contour.

[0025] The cross-sectional area of ​​the windward section 14 of the top surface in a direction orthogonal to the center line 13 of the top surface decreases upward along the extension direction of the center line of the top surface to a value close to zero; the cross-sectional area of ​​the side necking section 15 in a direction orthogonal to the center line 13 of the top surface (the center line of the main piston 111 is defined as the center line 13 of the top surface) decreases slowly downward along the extension direction of the center line of the top surface, forming a curved surface with a small cross-sectional area and a smooth transition along the direction of the center line of the top surface; the cross-sectional area of ​​the side transition section 16 in a direction orthogonal to the center line of the top surface decreases from the cross-sectional area at the upper end point of the top surface flat section to the cross-sectional area at the lower end point of the side necking section.

[0026] The top windward section 14 is located at the top of the auxiliary piston 112. The curved surface formed by the top windward section 14 directly faces the gas in the compression process. As the compression process proceeds, the gas pressure, temperature and density increase, and the gas resistance faced by the curved surface of the top windward section 14 increases sharply. In order to reduce the piston running resistance, the cross-sectional area of ​​the top windward section 14 (i.e., the top of the curved surface) of the auxiliary piston 112 corresponding to the top windward section 14 is reduced to a small value close to zero along the cross-sectional height direction to prevent high-pressure and high-temperature gas from accumulating above the top windward section 14 and reduce the aerodynamic resistance during piston movement. Since the accumulation of high-pressure and high-temperature gas above the top windward section 14 is prevented, the maximum temperature of the auxiliary piston 112 is also reduced. The side necking section 15 is a smoothly transitioned curve. The curved surface formed there enables the auxiliary piston 112 to extend into the exhaust cavity, so that the gas in the exhaust cavity participates in the compression, thereby reducing the compression ratio loss. The lower edge of the curved surface of the windward section 14 of the top surface is smoothly connected with the upper edge of the curved surface of the side necking section 15, so that the high-pressure airflow can flow smoothly and reduce the gas resistance when the piston moves. The top surface flat section 17 is connected to the upper edge of the side of the main piston 111, so that the auxiliary piston 112 becomes the upper end surface of the main piston 111. The top surface flat section 17 is a curved surface that coincides with the top horizontal surface 12 or is gently raised. The top surface flat section 17 is the main compression surface of the main piston 111. The side transition section 16 is a transition surface between the side necking section 15 and the top flat section 17. The upper edge line of the curved surface of the side transition section 16 is connected to the lower edge line of the curved surface of the side necking section 15, and the lower edge line of the curved surface of the side transition section 16 is connected to the inner edge line of the curved surface of the top flat section. The side transition section 16 prevents high-temperature and high-pressure gas from accumulating between the side necking section 15 and the top flat section 17, further reducing the resistance to piston movement and reducing the concentration of temperature field and stress field.

[0027] In this embodiment, the top windward section 14 is in a semi-elliptical arc shape, the side necking section 15 is in an S-shape, and the side transition section 16 is in a circular arc shape.

[0028] In this embodiment, the upper end of the vertical cross-sectional contour line of the main piston 111 has a top surface flat section 17 located on both sides of the vertical cross-sectional contour line of the auxiliary piston, the inner end point of the top surface flat section 17 is connected to the lower end point of the side transition section, and the outer end point of the top surface flat section 17 is connected to the upper edge line of the side of the main piston 21.

[0029] In this embodiment, the top surface flat section 17 may coincide with the top surface horizontal plane 12 (the plane enclosed by the upper edge line of the side surface of the main piston 111 is defined as the top surface horizontal plane 12 ), or may be a flat curve higher than the top surface horizontal plane 12 .

[0030] In this embodiment, a removable sleeve is provided in the compression chamber. The main piston 111 of the piston 110 is slidably matched with the cylinder sleeve 105. An annular groove is provided around the main piston, and a sealing ring is provided in the annular groove. Each cylinder is provided with a replaceable cylinder sleeve 105 which is independently installed in the cylinder body. The piston is installed in the replaceable cylinder sleeve 105 and can perform reciprocating linear motion in the cylinder sleeve 105. When the cylinder sleeve 105 is severely worn, each cylinder sleeve can be replaced separately, avoiding the problem that multiple cylinders must be replaced in the traditional integrated cylinder structure, thereby reducing maintenance costs. In addition, the cylinder sleeve 105 can be made of wear-resistant materials such as ductile iron to improve the wear resistance of the inner surface of the cylinder and improve the operating reliability of the compressor.

[0031] In this embodiment, a flange portion is provided on the outer peripheral side of the upper end of the cylinder sleeve 24, and an annular mounting groove matching with the flange portion is provided on the upper peripheral side of the compression chamber, and the flange portion is connected to the annular mounting groove by screws.

[0032] In this embodiment, the main shaft of the drive motor 20 is coaxially connected to the crankshaft 101 through a coupling 21; a connecting rod assembly 102 is provided under the piston 110, and the connecting rod assembly 102 includes a connecting rod body 124 whose small head end 125 is hinged to the main piston 111 of the piston 110 through a piston pin 103, and a seat sleeve 123 fixedly connected to the large head end 126 of the connecting rod body 124, and a bearing 127 that rotatably cooperates with the connecting rod journal on the crankshaft 101 is nested in the seat sleeve 123.

[0033] In this embodiment, the axial width of the seat sleeve 123 is consistent with the axial width W of the bearing bush, the axial width W of the bearing bush 127 is 2 to 8 times the thickness of the connecting rod body 124, and the axial width W of the bearing bush 127 is greater than the diameter D of the bearing bush. The connecting rod assembly adopts a wide bearing bush structure. The larger bearing bush width increases the contact area between the connecting rod and the crankshaft, reduces the contact pressure between the connecting rod and the crankshaft, and can not only stably transmit a larger piston force, but also reduce the wear of the connection pair, thereby increasing the life of the bearing bush. In addition, the wider bearing bush improves the ability of the connecting rod to resist the tipping torque caused by the unbalanced force of the piston, making the crank-connecting rod-piston mechanism run more smoothly, reducing the tipping piston vibration caused by the uneven piston force, thereby reducing the vibration of the compressor operation and improving the dynamic performance of the compressor.

[0034] In this embodiment, the cylinder head 106 is provided with an air inlet located at the top of the compression chamber, and an air inlet valve 109 is provided at the air inlet. An air inlet pipe 107 connected to the air inlet and an exhaust pipe 108 connected to the exhaust cavity are provided above the cylinder, and an exhaust valve 120 is provided at the upper opening of the exhaust cavity.

[0035] The cylinder block, cylinder liner, main piston and cylinder head together form a cylinder. Driven by the connecting rod, the main piston reciprocates on the straight line between the top dead center and the bottom dead center, continuously completing the intake-compression-exhaust process to compress the working gas. When the main piston is at the top dead center, the compression chamber volume is the smallest, and when the main piston is at the bottom dead center, the compression chamber volume is the largest.

[0036] like Figure 1 As shown, the exhaust cavity is located on the cylinder head. In the traditional compressor, since the attached piston is a plane, the volume of the exhaust cavity does not change during compression and exhaust, which reduces the compression ratio of the cylinder to a certain extent. For high-pressure and heavy-load compressors, the compression ratio loss caused by the exhaust cavity will significantly affect the performance of the compressor. Therefore, it is necessary to change the volume of the exhaust cavity during the compression process. The conventional method for changing the volume of the exhaust cavity is to set a protrusion with a flat top surface on the attached piston, and the protrusion enters the exhaust cavity during the compression process, thereby reducing the influence of the exhaust cavity on the compression ratio. However, the geometric discontinuity area of ​​the traditional planar protrusion is prone to cause airflow accumulation, and there are problems such as large resistance, temperature concentration, and stress concentration. These problems will greatly affect the efficiency and life of the compressor when high-temperature and high-pressure gas is compressed. Therefore, the present invention changes the attached piston 112 into a continuous curved surface structure, and the attached piston 112 is extended into the exhaust cavity through the curved surface formed by the top surface necking section 15 set by the attached piston 112. At the same time, the top cross-sectional area of ​​the windward section 14 of the top surface is a minimum value close to zero, thereby preventing the accumulation of high-pressure and high-temperature airflow above the windward section 14 of the top surface during the high-speed upward movement of the main piston 111, thereby reducing the resistance to piston movement, reducing stress and temperature concentration, and thus improving the efficiency and life of the compressor. In addition, by optimizing the curved surface design, the aerodynamic force generated by the auxiliary piston 112 when the main piston 111 moves can be used to stabilize the movement of the main piston 111, thereby reducing the vibration during the operation of the compressor.

[0037] A working method for a high-pressure, heavy-duty piston compressor for supercritical carbon dioxide as described above, wherein when the main piston is at the top dead center position, the exhaust valve is closed and the intake valve is opened, and then during the main piston running from the top dead center to the bottom dead center, the volume of the compression chamber gradually increases, and carbon dioxide gas enters the compression chamber from the air inlet, and when the main piston runs to the bottom dead center position, the intake valve is closed, completing the intake process; the main piston moves from the bottom dead center to the top dead center, the volume of the compression chamber decreases, completing the compression process, and the carbon dioxide gas is compressed in the compression chamber, and after reaching a certain pressure, the exhaust valve is opened, and the compressed carbon dioxide gas is discharged from the compression chamber into the exhaust pipe, and then the exhaust valve is closed, completing the exhaust process.

[0038] Unless otherwise stated, any technical solution disclosed in the present invention disclosed above, if it discloses a numerical range, then the disclosed numerical range is a preferred numerical range, and any technician in the field should understand that the preferred numerical range is only a numerical value with a more obvious technical effect or representative value among many implementable numerical values. Since there are too many numerical values ​​to be exhaustive, the present invention discloses only some numerical values ​​to illustrate the technical solution of the present invention, and the numerical values ​​listed above should not constitute a limitation on the scope of protection of the present invention.

[0039] If the present invention discloses or involves components or structures that are fixedly connected to each other, then, unless otherwise stated, the fixed connection can be understood as: a detachable fixed connection (for example, connection using bolts or screws), and can also be understood as: a non-detachable fixed connection (for example, riveting, welding). Of course, the mutual fixed connection can also be replaced by an integrated structure (for example, manufactured by integrated molding using a casting process) (except when it is obviously impossible to use an integrated molding process).

[0040] In addition, unless otherwise stated, the terms used to indicate positional relationships or shapes in any of the technical solutions disclosed in the present invention include states or shapes that are approximate, similar, or close to them.

[0041] Any component provided by the present invention may be assembled from a plurality of separate components, or may be a separate component manufactured by an integral forming process.

[0042] The above is only a preferred embodiment of the present invention, and does not limit the present invention in other forms. Any technician familiar with the profession may use the above disclosed technical content to change or modify it into an equivalent embodiment with equivalent changes. However, any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention without departing from the technical solution of the present invention still belongs to the protection scope of the technical solution of the present invention.

Claims

1. A high-pressure, heavy-duty piston compressor for supercritical carbon dioxide, characterized in that: It includes a compressor body, a drive motor and a compressor shell; the compressor body includes a plurality of cylinders, the cylinders include a cylinder body and a cylinder head arranged in sequence from bottom to top, a compression chamber is provided in the cylinder body, a piston is provided in the compression chamber, an exhaust cavity located at the top of the compression chamber is provided on the cylinder head, the piston includes a main piston working with the compression chamber, an auxiliary piston is provided on the upper end of the main piston which protrudes upward and can extend into the exhaust cavity when the piston runs to the top dead center, and the auxiliary piston is a smooth curved surface structure.

2. The high-pressure, heavy-duty piston compressor for supercritical carbon dioxide according to claim 1, characterized in that: The upper end of the auxiliary piston is provided with a curved top which bulges upwards, and the peripheral side of the lower part of the auxiliary piston is provided with a neck portion, and the curved top and the neck portion are transitionally connected by an arc-shaped drum portion.

3. The high-pressure, heavy-duty piston compressor for supercritical carbon dioxide according to claim 1 or 2, characterized in that: The vertical cross-sectional contour line of the attached piston is a curve, including a top windward section, side necking sections and side transition sections on both sides, and the top windward section, side necking section and side transition section are connected in sequence from top to bottom.

4. The high-pressure, heavy-duty piston compressor for supercritical carbon dioxide according to claim 3, characterized in that: The upper end of the vertical section contour line of the main piston has a top surface flat section located on both sides of the vertical section contour line of the auxiliary piston, the inner end point of the top surface flat section is connected to the lower end point of the side transition section, and the outer end point of the top surface flat section is connected to the upper edge line of the side of the main piston.

5. The high-pressure heavy-duty piston compressor for supercritical carbon dioxide according to claim 1, characterized in that: The compression chamber is detachably sleeved with a cylinder sleeve, the main piston of the piston is slidably matched with the cylinder sleeve, an annular groove is arranged around the main piston, and a sealing ring is arranged in the annular groove.

6. The high-pressure, heavy-duty piston compressor for supercritical carbon dioxide according to claim 5, characterized in that: A flange portion is provided on the outer peripheral side of the upper end of the cylinder sleeve, and an annular mounting groove matching with the flange portion is provided on the peripheral side of the upper end of the compression chamber.

7. The high-pressure, heavy-duty piston compressor for supercritical carbon dioxide according to claim 1, characterized in that: The main shaft of the driving motor is coaxially connected to the crankshaft through a coupling; a connecting rod assembly is provided under the piston, and the connecting rod assembly includes a connecting rod body whose small end is hinged to the main piston of the piston through a piston pin, and a seat sleeve fixedly connected to the large end of the connecting rod body, and a bearing bushing that rotatably cooperates with the connecting rod journal on the crankshaft is embedded in the seat sleeve.

8. The high-pressure, heavy-duty piston compressor for supercritical carbon dioxide according to claim 7, characterized in that: The axial width of the seat sleeve is consistent with the axial width of the bearing shell, the axial width of the bearing shell is 2 to 8 times the thickness of the connecting rod body, and the axial width of the bearing shell is greater than the diameter of the bearing shell.

9. The high-pressure, heavy-duty piston compressor for supercritical carbon dioxide according to claim 1, characterized in that: The cylinder head is provided with an air inlet located at the top of the compression chamber, an air inlet valve is provided at the air inlet, an air inlet pipe connected with the air inlet and an exhaust pipe connected with the exhaust cavity are provided above the cylinder, and an exhaust valve is provided at the upper opening of the exhaust cavity.

10. A method for operating a high-pressure, heavy-duty piston compressor for supercritical carbon dioxide as claimed in claim 9, characterized in that: When the main piston is at the top dead center, the intake valve opens after the exhaust valve is closed. Subsequently, as the main piston moves from the top dead center to the bottom dead center, the volume of the compression chamber gradually increases, and carbon dioxide gas enters the compression chamber from the intake port. When the main piston moves to the bottom dead center, the intake valve closes, completing the intake process; the main piston moves from the bottom dead center to the top dead center, the volume of the compression chamber decreases, completing the compression process, and the carbon dioxide gas is compressed in the compression chamber. After reaching a certain pressure, the exhaust valve opens, and the compressed carbon dioxide gas is discharged from the compression chamber into the exhaust pipe. Subsequently, the exhaust valve closes, completing the exhaust process.

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