Cylinder body structure of wellhead natural gas compressor, compressor and working method of compressor

Abstract

The invention discloses a wellhead natural gas compressor cylinder body structure, a compressor and a working method of the compressor, and relates to the technical field of compressors, the cylinder body structure comprises a cylinder barrel, the cylinder barrel comprises an outer cylinder barrel and an inner cylinder barrel, the inner cylinder barrel is embedded in a center hole of the outer cylinder barrel, and a piston cavity of the cylinder barrel is formed by a center hole of the inner cylinder barrel; the inner wall of the outer cylinder barrel and the outer wall of the inner cylinder barrel are each provided with a spiral groove with a semi-annular cross section, the spiral grooves of the outer cylinder barrel and the outer wall of the inner cylinder barrel define a spiral flow channel which extends in the axis direction of the cylinder barrel, the cross section of the spiral flow channel is annular, and the spiral flow channel is provided with a medium leading-in hole and a medium leading-out hole which are located in the surface of the outer cylinder barrel. The compressor comprises the cylinder body structure, and the working method is the working method of the compressor. According to the scheme, the temperature difference of different positions of the inner wall of the cylinder can be effectively reduced, the purposes of reducing air leakage of a piston ring and optimizing the volume of the compressor are achieved, and the purposes of reducing deformation of different positions of the inner wall of the cylinder and optimizing vibration in the working process of the compressor are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of compressors, and particularly to a cylinder block structure of a wellhead natural gas compressor, a compressor and a working method thereof. Background Art

[0002] The role of a wellhead natural gas compressor in natural gas extraction is to pressurize the natural gas from the wellhead and transport the pressurized natural gas to the exhaust pipeline. In the prior art, most compressors for this purpose adopt positive displacement compressors, such as piston compressors, and are assembled in a skid-mounted manner with separators, buffers, coolers, etc. to form a skid-mounted compressor unit and installed near the wellhead. The basic configuration of the commonly used compressor is generally the solution provided by the patent document with the publication (announcement) number CN202811255U. The specific application can be: driving the crankshaft to rotate through a variable frequency motor, connecting multiple crossheads in a circumferential staggered manner on the crankshaft, each crosshead is connected with a piston ring through a piston rod, and each piston ring is arranged in a cylinder block structure. In this way, when the crankshaft rotates, multiple compression components work simultaneously, which can not only balance the impact on the crankshaft, but also meet the need for large flow rate treatment of wellhead gas.

[0003] Different from traditional compressors, in order to adapt to the gas outlet characteristics of wellhead gas, compressors for this purpose usually need to have the ability of wide throughput adjustment, the ability to adapt to the pressure fluctuation of wellhead gas, and explosion-proof ability. At the same time, due to the characteristics of continuous high-load operation of compressors for this purpose, and there is a higher probability of entraining liquids, fine particles or even corrosive liquids in the medium flow. To solve the problems of difficult use and maintenance and high safety hazards in remote areas and ensure the continuous production of wellhead gas, for the design of the compressor unit, there are high requirements for the reliability and service life of filters and separators. For the design of the compressor, there are high requirements for vibration control, fault monitoring and prediction.

[0004] In the prior art, among the means that can be adopted for the above-mentioned vibration control, cylinder temperature control is included, and commonly, external cooling is used to strengthen the heat dissipation of the cylinder. This solution has the effect of reducing the temperature difference in different regions of the cylinder to a certain extent. In order to optimize the performance and service life of the imported natural gas compressor, it is necessary to further optimize the structure of the compressor. Summary of the Invention

[0005] Aiming at the above-mentioned problem of optimizing the compressor structure, the present invention provides a cylinder block structure of a wellhead natural gas compressor, a compressor and a working method thereof. This solution can effectively reduce the temperature difference at different positions on the inner wall of the cylinder, achieve the purpose of reducing piston ring leakage and optimizing the volume of the compressor, and achieve the purpose of reducing the deformation at different positions on the inner wall of the cylinder and optimizing the vibration during the operation of the compressor.

[0006] In view of the above problems, the cylinder block structure of the wellhead natural gas compressor, the compressor and its working method provided by the present invention solve the problems through the following technical key points: The cylinder block structure of the wellhead natural gas compressor includes a cylinder barrel, and the cylinder barrel includes an outer cylinder barrel and an inner cylinder barrel. The inner cylinder barrel is embedded in the central hole of the outer cylinder barrel, and the central hole of the inner cylinder barrel forms the piston cavity of the cylinder barrel; Semicircular spiral grooves are provided on both the inner wall of the outer cylinder barrel and the outer wall of the inner cylinder barrel. The spiral grooves of the two enclose a spiral flow passage that extends along the axis of the cylinder barrel and has a circular cross-section. The spiral flow passage is provided with a medium inlet hole and a medium outlet hole on the surface of the outer cylinder barrel. The medium inlet hole is used to introduce fluid into the spiral flow passage, and the medium outlet hole is used to discharge the medium in the spiral flow passage.

[0007] In the prior art, piston compressors are widely used in wellhead natural gas compression. This type of compressor is particularly suitable for high-pressure (greater than 15 MPa) and occasions with large fluctuations in wellhead gas pressure (such as shale gas wells). For the cylinder block cooling of piston compressors, external cooling methods are usually used to cool the cylinder, such as setting heat dissipation fins on the outer wall of the cylinder barrel, configuring air-cooling mechanisms and liquid-cooling mechanisms for the cylinder barrel, etc. This solution has a certain effect of reducing the temperature difference in different regions of the cylinder. However, due to the large processing flow rate of natural gas compressors and the obvious difference between the inlet temperature and the outlet temperature, for the inlet region and the outlet region of the cylinder block, because the heat conduction at these positions is asymmetric, such a heat dissipation method has little effect on the temperature at different positions of the inner wall of the cylinder, resulting in uneven deformation of the cylinder barrel and thus causing compressor vibration. Specifically: Regarding the vibration during the operation of a piston-type wellhead natural gas compressor, one of the inducing factors is the uneven local temperature distribution on the cylinder: intake ports and exhaust ports are respectively arranged at both ends of the cylinder. When the piston moves, the space at one end of the piston ring sucks in gas, and the space at the other end compresses it to improve the working efficiency and natural gas processing capacity. At the same time, for convenient piping layout, the intake ports are arranged in a straight line, and the exhaust ports are arranged in a straight line (the intake ports and exhaust ports can be arranged in a single row respectively, such as one intake port and one exhaust port are arranged at each end of the cylinder, or they can be arranged in two rows, such as two intake ports and two exhaust ports are arranged at each end of the cylinder, with different intake ports located at different circumferential positions of the cylinder, and different exhaust ports also located at different circumferential positions of the cylinder). The straight line where the above intake ports are located and the straight line where the exhaust ports are located are in different orientations on the cylinder. When the compressor is working, since the intake temperature is lower than the exhaust temperature (considering the compression efficiency and the dew point temperature under different pressures, in each stage of compression, an intake temperature of 30 - 50 °C can be adopted, and depending on the compression ratio, the exhaust temperature can reach 150 °C or even higher), because the above intake ports and exhaust ports are located at different positions on the cylinder block, thus, under the action of asymmetric heat conduction in different directions and large flow rates, this causes the temperature in the circumferential direction of the cylinder to be uneven, with local hot zones and local cold zones appearing at different orientations on the cylinder. Under the temperature difference between the cold and hot zones, the cylinder barrel deforms unevenly (from circular to elliptical). According to measurements, in a specific application, for a cast iron cylinder with a cylinder diameter of 400 mm, the deformation difference between the cold and hot zones reaches 0.6 mm, and the area with the most obvious elliptical deformation is located at the junction of the cold and hot zones, thus causing vibration of the cylinder during the working process. This not only accelerates the wear of the corresponding structure, but also, under the stress cycle, it is easy to cause the formation of expandable cracks on the inner wall of the cylinder. At the same time, this may also cause air leakage of the piston ring, seriously affecting the failure rate and volumetric efficiency of the compressor.

[0008] To address the problem that the elliptical deformation of the cylinder barrel caused by the temperature difference in different orientations of the cylinder barrel results in vibration and a decrease in volumetric efficiency during the operation of the compressor, the above solution is provided. This solution can effectively reduce the temperature difference at different positions on the inner wall of the cylinder, achieving the purpose of reducing air leakage of the piston ring and optimizing the volume of the compressor, and achieving the purpose of reducing the deformation at different positions on the inner wall of the cylinder and optimizing the vibration during the working process of the compressor.

[0009] Specifically, the outer cylinder is the outer layer of the cylinder, and the inner cylinder is the inner layer of the cylinder. The outer cylinder and the inner cylinder are both independent parts. After the spiral grooves are machined on each of them, the inner cylinder is nested inside the outer cylinder to assemble into a double-layer cylinder structure. In this way, the spiral flow channel is formed by the spiral grooves on the cylinder. When the cylinder is applied to the natural gas compression process, a heat-carrying fluid medium, such as heat-carrying oil, is introduced into the spiral flow channel. Since the spiral flow channel extends along the axis direction of the cylinder, the outer cylinder can not only provide support for the inner cylinder to ensure the effective wall thickness of the cylinder, but also, the heat-carrying effect of the medium in the spiral flow channel is used to form an isothermal wall on the outer wall of the inner cylinder, making the temperatures at each position on the outer wall of the inner cylinder closer. In this way, since the heat source on the inner cylinder is the natural gas compressed in the piston cavity, for each position on the side of the inner cylinder, the above-mentioned isothermal wall can effectively reduce the difference in the temperature difference between the inner and outer sides at each position of the inner cylinder. From the perspective of thermal deformation, this solution can effectively reduce the temperature difference at different positions on the inner wall of the cylinder, achieving the purpose of reducing piston ring air leakage and optimizing the compressor volume, and achieving the purpose of reducing the deformation at different positions on the inner wall of the cylinder and optimizing the vibration during the operation of the compressor.

[0010] At the same time, different natural gas wellheads have different wellhead pressures. The initial wellhead pressures of low-pressure gas fields and shale gas fields are relatively small, and the wellhead gas pressure will continuously decrease as the exploitation progresses. In this case, it is usually necessary to boost the pressure to 7 to 15 MPa (in some cases with small flow rates, the piston compressor is used to boost the pressure to more than 15 MPa) before transporting it to the transmission pipeline. Therefore, for the cylinder design of the wellhead natural gas compressor, although the additive manufacturing method can be used to machine a complex cylinder structure, the cylinder machined by this method has the problem of poor interlayer bonding strength. Therefore, in order to make the cylinder have sufficient compressive capacity under the condition of meeting the processing flow rate, in the production of this type of piston compressor, the cylinder is usually machined from castings and forgings. The existing integral cylinder can obtain a cooling flow channel on the cylinder through subsequent reprocessing, but it is difficult to machine an annular flow channel and a spiral flow channel on the cylinder. In response to the requirement for the cylinder's pressure-bearing capacity, this solution provides a technical solution in which the cylinder is designed to include an outer cylinder and an inner cylinder, and spiral grooves are respectively arranged on the inner wall of the outer cylinder and the outer wall of the inner cylinder. The spiral flow channel is formed by the spiral grooves. Such a technical solution can not only utilize traditional casting and forging to machine high-quality outer cylinders and inner cylinders, but also, the spiral grooves are surface structures on the inner wall of the outer cylinder and the outer wall of the inner cylinder, and can be integrally formed on the outer cylinder and the inner cylinder by methods such as casting, or after the tubular basic structures of the outer cylinder and the inner cylinder are formed, on the basis of this basic structure, the spiral groove machining can be completed by further machining. Therefore, this solution also has the characteristics of effectively ensuring the cylinder performance and convenient machining.

[0011] It is easy to understand that the medium inlet hole and the medium outlet hole respectively serve as the channels for introducing the medium into the spiral flow channel and for discharging the medium from the spiral flow channel. As those skilled in the art, the connection positions of the medium inlet hole and the medium outlet hole on the spiral flow channel should be located at different positions of the spiral flow channel, so that the medium can cover different circumferential positions and axial positions of the inner cylinder by flowing spirally along the spiral flow channel, and form the isothermal wall on the outer wall of the inner cylinder. At the same time, as those skilled in the art, when the medium flows along the spiral flow channel, if the temperature of the medium when it enters the cylinder is lower than the exhaust temperature of the cylinder and higher than the intake temperature of the cylinder, due to the gases entering and leaving the cylinder body, different heat dissipation conditions and temperatures will exist at different positions of the cylinder body. This makes the medium absorb and release heat to different degrees at different positions during the flowing process, that is, there is a certain temperature difference in the medium at different positions of the spiral flow channel. Therefore, the understanding of the isothermal wall should be that the medium in the spiral flow channel has the function of balancing the temperature differences at different axial positions and circumferential positions on the outer wall of the inner cylinder, but it cannot be understood that the temperatures at different positions on the outer wall of the inner cylinder can be made exactly the same.

[0012] In a specific embodiment, the spiral groove on the inner wall of the outer cylinder starts from the inner wall at one end and spirally runs along the center line of the axis of the outer cylinder on this inner wall, and ends at the inner wall at the other end of the outer cylinder. The spiral groove on the outer wall of the inner cylinder starts from the outer wall at one end and spirally runs along the center line of the axis of the inner cylinder on this outer wall, and ends at the outer wall at the other end. The spiral flow channel extends from the end of the cylinder where the piston rod hole is provided to the end of the cylinder where the end plate is provided. In the axial direction of the cylinder axis, the piston cavity is located between the two ends of the spiral flow channel, so that the spiral flow channel can fully cover the lateral heat dissipation surface of the piston cavity, and the spiral flow channel can provide comprehensive uniform temperature protection against uneven deformation for the inner cylinder outside the piston cavity.

[0013] A further technical solution of the cylinder body structure is as follows: The inner cylinder is a cylindrical structure with a piston rod hole communicated with the piston cavity at one end and an outer shape of a stepped shaft. The central hole of the outer cylinder is a stepped hole with a stepped surface; One end of the inner cylinder provided with the piston rod hole is supported on the stepped surface, and the other end of the inner cylinder is embedded in the outer cylinder; It further includes an end plate bolted to the outer cylinder. The end plate is connected to the end of the outer cylinder far from the piston rod hole. A boss inserted into the inner cylinder is provided at the inner end of the end plate, and the inner end surface of the end plate supports the other end of the inner cylinder through a disc spring assembly.

[0014] The above provides a specific cylinder assembly solution. The piston chamber is the working chamber of the piston ring in the compressor. The piston rod on the piston ring is matched with the piston rod hole. In this solution, the constraint of the inner wall of the outer cylinder on the outer wall of the inner cylinder is used to realize the position constraint of the outer cylinder and the inner cylinder in the radial direction of the cylinder. One end of the inner cylinder provided with the piston rod hole is supported on the step surface of the outer cylinder through the shoulder structure at this end, and the other end of the inner cylinder is supported on the end plate through the disc spring assembly, so as to realize the position constraint of the outer cylinder and the inner cylinder in the axial direction of the cylinder.

[0015] At the same time, as the cylinder head on the cylinder, after the end plate is fixed to the outer cylinder, it can not only support the inner cylinder through the disc spring assembly to prevent the inner cylinder from moving in the central hole of the outer cylinder. At the same time, the boss inserted into the inner cylinder on it is used to control the clearance size of the piston chamber.

[0016] The above solution realizes the position constraint of the inner cylinder in the central hole of the outer cylinder by using a simple structure. At the same time, for the axial deformation generated during the working process of the inner and outer cylinders, not only can the thrust of the disc spring assembly on the inner cylinder be used to keep the inner cylinder having a stable axial position relative to the outer cylinder, but also, through the compression deformation generated on the disc spring assembly, the thermal deformation of the cylinder can be adapted and the thermal stress can be released, so that the cylinder block structure of the present invention is not only simple in structure, but also has reliable structural stability and the generated thermal stress can be reliably released.

[0017] An air inlet hole and an exhaust hole are provided on the cylinder, and each end of the cylinder has an air inlet hole and an exhaust hole; The air inlet hole and the exhaust hole are both: there is an outer side hole section on the outer cylinder, and there is an inner side hole section on the inner cylinder, and the outer side hole section is docked with the inner side hole section; A sealing assembly is configured for each air inlet hole and exhaust hole. The sealing assemblies for the air inlet hole and the exhaust hole are both: the sealing assembly is located at the position where the outer side hole section and the inner side hole section are docked with each other. The sealing assembly has a sealing ring extending along the circumferential direction of the docking position and located outside the docking position. The sealing ring is used as a sealing isolation structure for the gap between each of them and the cylinder. The gap is the gap between the outer cylinder and the inner cylinder.

[0018] The above provides a technical solution with specific intake and exhaust. Specifically, in the existing cylinder intake and exhaust solutions, the intake hole and the exhaust hole are generally set as stepped holes. The inner diameter of the stepped hole is reduced and communicated with the piston cavity, and intake and exhaust valves are installed on the outer side of the stepped hole. The inner hole section at the above docking position is directly communicated with the piston cavity. Therefore, when the cylinder is set as a double-layer structure including an outer cylinder and an inner cylinder, the intake hole and the exhaust hole on the cylinder are formed by docking the outer hole section located on the outer cylinder and the inner hole section located on the inner cylinder. For the gap on the mating surface between the inner and outer cylinders, even if the inner cylinder is expanded and joined to the outer cylinder by strength (the outer diameter of the inner cylinder is larger than the inner diameter of the central hole of the outer cylinder at room temperature), but under the influence of machining errors, inevitable vibrations and thermal deformations during the operation of the compressor, although the intake and exhaust pressures of the wellhead natural gas compressor have the effect of preventing the medium in the spiral flow channel from entering the piston cavity through the gap and the inner hole section, when intake holes and exhaust holes are provided on both sides of the piston ring (the piston cavities on both sides of the piston ring are used as compression working cavities, and in any moving direction of the piston ring, one side of the piston cavity intakes air and the other side compresses), there is an obvious pressure difference on both sides of the piston ring. In this way, the possible phenomena include that the piston cavity on the compression side of the piston ring pressurizes the gap through the inner hole section. When this pressure exceeds the sealing ability of the mating surface between the outer and inner cylinders, the medium in the spiral flow channel enters the piston cavity on the intake side of the piston ring through the inner hole section, ultimately causing the occurrence of the liquid hammer phenomenon of the compressor. At the same time, the gas in the piston cavity entering the mating surface and flowing into the spiral flow channel will also lead to a reduction in the efficiency of the compressor. Based on the above, the technical solution of the sealing component is provided.

[0019] Specifically, the sealing component is used to provide a sealing ring for the docking position. Specifically: an annular sealing surface is formed on the outer periphery of the outer orifice of the inner hole section to prevent the compressed gas in the piston cavity from entering the gap on the mating surface, resulting in an increase in the internal pressure of the gap, ultimately causing the medium located between the outer cylinder and the inner cylinder to enter the intake side of the piston cavity and causing the occurrence of the liquid hammer phenomenon during the compression stage on the intake side, and at the same time avoiding the reduction of the working efficiency of the compressor caused by fluid flow or leakage of compressed gas on the compression side.

[0020] In a specific implementation, since the inner cylinder needs to be embedded in the outer cylinder and the outer cylinder serves as a supporting layer for the inner cylinder, it is preferred that the outer wall of the inner cylinder is a cylindrical surface. In this way, the mating surfaces of the outer cylinder and the inner cylinder at the position where the side hole section and the inner hole section are butted against each other are also cylindrical surfaces that fit each other. Therefore, unlike the shape of the traditional flat-plate sealing ring, the sealing plate in this scheme needs to fit the outer surface of the inner cylinder and extend in the circumferential direction of the outer hole opening of the inner hole section. The sealing plate is an arc-shaped plate structure that fits the cylindrical surface of the outer cylinder. Since the compressor processes corrosive media, the sealing ring must be selected from a material that is resistant to acid corrosion, such as a rubber sealing structure with a skeleton inside.

[0021] The sealing assembly also includes a compression ring and a plurality of compression bolts; Each sealing assembly is provided with an annular groove on the outer cylinder, the annular groove is located at the outer periphery of the outer hole section and intersects with the outer hole section to form a stepped hole, and the pressure ring and the sealing ring are both installed in the annular groove; The compression ring is stacked on the outside of the sealing ring, the inside of the sealing ring is attached to the outer wall of the inner cylinder, the side of the sealing ring is attached to the groove wall of the ring groove, the clamping bolts are arranged at intervals along the circumferential direction of the compression ring, each clamping bolt is threadedly connected to the outer cylinder, and the inner end of each clamping bolt acts on the outer surface of the compression ring and provides the compression ring with an extrusion force toward the sealing ring; The outer end of the sealing ring is provided with an annular groove, and the inner end of the pressure ring is provided with a tapered section whose outer shape is adapted to the shape of the groove, and the tapered section is embedded in the groove.

[0022] The above provides a specific sealing assembly structure, which provides thrust toward the sealing ring for the pressure ring by tightening the clamping bolts connected to the outer cylinder, so that the sealing ring obtains the extrusion force. Before the center hole of the outer cylinder is embedded in the inner cylinder, the pressure ring and the sealing ring can be connected by bonding to form an integral structure, and then the integral structure is pasted on the outer end surface of the ring groove. When the inner cylinder is embedded in the outer cylinder in place, the clamping bolts are tightened by the air inlet and the exhaust hole to push the integral structure toward the inner cylinder and make the sealing ring fit the outer wall of the inner cylinder. In the present solution, it is further configured that the outer end of the sealing ring has a groove, and the inner end of the pressure ring has a conical section adapted to the groove. In this way, in the process of the pressure ring moving toward the sealing ring, the pressure ring can not only provide the sealing ring with an extrusion force in the radial direction of the cylinder, but also provide the outer edge of the sealing ring with an extrusion force in the axial direction of the cylinder. In this way, the inner end face of the sealing ring forms a sealing surface with the outer wall of the inner cylinder, and the side face of the sealing ring forms a sealing surface with the side face of the ring groove, thereby achieving reliable sealing of the docking position.

[0023] In a specific implementation, the pressure ring is also an arc-shaped plate structure adapted to the curvature of the outer surface of the inner cylinder barrel. In such an application, since the outer hole section is preferably arranged as a flat-bottom hole convenient for installing the intake and exhaust valves, for the clamping bolts in different orientations of the pressure ring, at the same time, to avoid the exposure of the clamping bolts affecting the installation of the intake and exhaust valves, a preferred solution is to install the clamping bolts with the outer ends sunken relative to the bottom of the flat-bottom hole. In such an application, clamping bolts with multiple length parameters should be used.

[0024] The inner cylinder barrel is a cast iron barrel, and the outer cylinder barrel is an aluminum alloy barrel. The inner cylinder barrel is expanded and connected in the outer cylinder barrel.

[0025] The above solution provides a form of the inner cylinder barrel, a form of the outer cylinder barrel, and an assembly method of the cylinder barrels. Specifically, the inner cylinder barrel is made of cast iron with a small coefficient of thermal expansion and wear resistance, such as ductile iron, to ensure its sealing ability with the piston ring at high temperatures. The outer layer is made of aluminum alloy with high thermal conductivity and less heat capacity per unit volume. By reducing the heat absorption of the outer cylinder barrel and strengthening heat transfer, the maximum temperature of the outer cylinder barrel and the temperature difference at different positions are reduced, so that each position on the side of the cylinder has relatively balanced heat dissipation conditions, achieving the purpose of reducing uneven thermal deformation occurring on the outer cylinder barrel. The inner cylinder barrel being expanded and connected in the outer cylinder barrel is a pre-stress installation method for the cylinder barrels to cope with the characteristic that the coefficient of thermal expansion of aluminum alloy is significantly greater than that of cast iron, strengthening the tightness of the cooperation between the outer cylinder barrel and the inner cylinder barrel during the operation of the compressor and avoiding the generation of gaps between the inner and outer cylinder barrels to ensure the supporting ability of the outer cylinder barrel for the inner cylinder barrel.

[0026] The number of the spiral flow channels is 1. In the axial direction of the cylinder barrel, both the intake position and the exhaust position of the piston chamber are within the coverage area of the spiral flow channel. The coverage area is the area between the two ends of the spiral flow channel on the cylinder barrel. The number of the medium introduction holes is 1. The conduction position of the medium introduction hole and the spiral flow channel is in the middle of the axial direction of the spiral flow channel. The number of the medium outlet holes is 2. Each end of the spiral flow channel is provided with a medium outlet hole.

[0027] The above provides a specific form of spiral flow channel. The setting of the end positions of the spiral flow channel and the air inlet and outlet positions of the piston chamber in the axial direction of the cylinder barrel aims to utilize the isothermal wall effect exerted by the spiral flow channel to evenly distribute the heat dissipation conditions at the air inlet and outlet positions of the piston chamber, so as to achieve the purpose of controlling the uneven deformation amount of the inner cylinder barrel under the hot state. The air inlet and outlet positions are the connection positions of the above-mentioned air inlet holes and exhaust holes on the piston chamber respectively. The setting methods of the medium inlet hole and the medium outlet hole are designed to achieve the following: for this spiral flow channel, the fluid in the middle of the spiral flow channel is introduced, and the introduced fluid can flow to both sides of the spiral flow channel and flow out from the medium outlet holes at both ends of the spiral flow channel respectively. In the spiral flow channel, for the fluid flowing to each side, the flow path of the fluid from introduction to extraction is short, and the two-way flow is symmetric with respect to the middle in the length direction of the cylinder barrel. Therefore, this solution can not only reduce the temperature difference of the fluid at different positions in the spiral flow channel and reduce the uneven deformation occurring on the inner cylinder barrel, but also the required circulating pipeline structure is simple. As those skilled in the art know, the spiral flow channel is a spiral-shaped flow channel, and the axis of the central hole of the spiral flow channel is the axis of the spiral flow channel. In specific applications, it is set that the axis of the spiral flow channel is collinear with the axis of the inner cylinder barrel.

[0028] The number of the spiral flow channels is greater than 1, and the spiral flow channels are arranged in sequence along the axial direction of the cylinder barrel. In the axial direction of the cylinder barrel, both the air inlet position and the air outlet position of the piston chamber are within the coverage area of the spiral flow channels. The coverage area is the distribution area of the spiral flow channels on the cylinder barrel on the axis of the cylinder barrel, and the spiral flow channels are independent of each other; Each spiral flow channel is configured with a medium inlet hole at one end and a medium outlet hole at the other end.

[0029] The above provides a specific form of spiral flow channel, which is an equivalent solution for the case where the number of the above spiral flow channels is 1. Specifically, different spiral flow channels are located at different axial positions of the cylinder barrel. For the heat dissipation conditions of these different axial positions (for example, the air inlet hole position has good heat dissipation conditions because the inlet air temperature is low and the flow rate is large, and the cylinder barrel in this area is the cold area on the cylinder barrel; the exhaust hole position has poor heat dissipation conditions because the exhaust air temperature is high and the flow rate is large, and the cylinder barrel in this area is the hot area on the cylinder barrel), by introducing fluids with different temperatures or different flow rates into these spiral flow channels, the purpose of adjusting to reduce the temperature difference of the fluid at different positions in the spiral flow channel and reducing the uneven deformation occurring on the inner cylinder barrel can be achieved.

[0030] It further includes a circulation system connected to the spiral flow channel through a circulation pipeline. The circulation system, the circulation pipeline, and the spiral flow channel form an annular medium circulation loop. The spiral flow channels are connected in series in the medium circulation loop, and the circulation pipeline is connected to the spiral flow channel through the medium inlet hole and the medium outlet hole; The described circulation system includes a pump and a cooler connected in series in the medium circulation loop. The pump serves as the power device for the medium to circulate in the medium circulation loop, and the cooler is used to cool down the medium in the medium circulation loop.

[0031] As described above, a technical solution is provided for using a circulation system to supply circulating fluid to the spiral flow channel of the cylinder barrel. In specific implementation, considering heat dissipation of the cylinder barrel and optimizing the non-uniform deformation of the inner cylinder barrel by reducing the temperature difference between the inlet and outlet fluids of the spiral flow channel, a preferred application is that the initial temperature of the fluid injected into the spiral flow channel is the intermediate value of the compressor inlet and outlet gas temperatures. By setting to adopt the described circulation system, not only can this fluid be reused repeatedly, but also the temperatures of the fluid introduced into and led out of the spiral flow channel can be adjusted through the cooler cooling capacity adjustment and pump flow rate adjustment.

[0032] In a specific implementation manner, since there is a possibility that the gas in the piston cavity enters the spiral flow channel through the mating surface, if this part of the gas does not enter the low-pressure side of the piston ring in the piston cavity, it will not cause a substantial impact on the safe operation of the compressor, but this will increase the possibility of liquid hammer and lead to a decrease in the operating efficiency of the compressor. Based on this, a microbubble sensor for detecting whether there are bubbles in the liquid phase is provided in the circulation pipeline connected to the medium outlet hole, so as to monitor the operating conditions of the compressor through the detection results of the microbubble sensor and avoid serious operating failures of the compressor.

[0033] This solution also relates to a wellhead natural gas compressor, including a cylinder for realizing natural gas compression. The cylinder includes a cylinder body structure and a piston assembly installed in the cylinder body structure. The cylinder body structure is the cylinder body structure provided in any one of the above. The compression working chamber of the piston cavity has an air outlet position located at the bottom side of the piston cavity.

[0034] The compressor is a piston compressor including the cylinder body structure, which is a specific application of the cylinder body structure. As described above, if both piston cavities on both sides of the piston ring have air inlet holes and air outlet holes, it should be considered that both piston cavities on both sides of the piston ring are the compression working chambers. The above solution that the compression working chamber has an air outlet position located at the bottom side of the piston cavity aims to achieve: when there is liquid in the compression working chamber, it can be discharged in time through this outlet position along with the exhaust gas, avoiding serious liquid hammer failures of the compressor.

[0035] This solution also relates to a working method of a wellhead natural gas compressor. The compressor is the compressor described above, and this working method is as follows: During the process of the compressor compressing wellhead natural gas, heat-carrying medium is introduced into the spiral flow channel and flows along the spiral flow channel to balance the temperatures at various positions on the outer periphery of the inner cylinder barrel.

[0036] The working method described above is the compressor operation method based on the compressor structure. As described above, this solution aims to utilize the fluid in the spiral flow channel to form an isothermal wall on the outer circumference of the inner cylinder. By equalizing the heat dissipation conditions and temperatures at various positions of the inner cylinder, this isothermal wall reduces the non-uniform deformation that occurs on the inner cylinder during the operation of the compressor, thereby achieving the purpose of reducing piston ring air leakage and optimizing the compressor volume, and achieving the purpose of reducing the deformation at different positions on the inner wall of the cylinder and optimizing the vibration during the operation of the compressor.

[0037] The present invention has the following beneficial effects: This solution equalizes the heat dissipation conditions and temperatures at various positions of the inner cylinder, reducing the non-uniform deformation that occurs on the inner cylinder during the operation of the compressor, thereby achieving the purpose of reducing piston ring air leakage and optimizing the compressor volume, and achieving the purpose of reducing the deformation at different positions on the inner wall of the cylinder and optimizing the vibration during the operation of the compressor, so that the wellhead compressor can better adapt to long-term high-load operation and reduce the failure rate during operation.

[0038] At the same time, this solution also has the characteristics of effectively ensuring the performance of the cylinder block and being convenient for processing. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 is a cross-sectional view of a specific embodiment of the cylinder block structure of the wellhead natural gas compressor described in this solution; Figure 2 is Figure 1 a partial enlarged view of part A in ; Figure 3 is Figure 1 a partial enlarged view of part B in ; Figure 4 is a cross-sectional view of the laminated structure formed by the pressure ring and the sealing ring in a specific embodiment of the cylinder block structure of the wellhead natural gas compressor described in this solution; Figure 5 is a side view of the laminated structure formed by the pressure ring and the sealing ring in a specific embodiment of the cylinder block structure of the wellhead natural gas compressor described in this solution; Figure 6 is Figure 4 a cross-sectional view of the provided laminated structure; Figure 7 is a front view of a specific embodiment of the cylinder block structure of the wellhead natural gas compressor described in this solution; Figure 8 is a side view of a specific embodiment of the cylinder block structure of the wellhead natural gas compressor described in this solution. The state shown in this side view is the installation state of the cylinder block structure on the compressor, so that the compression working chamber has an air outlet position located at the bottom side of the piston chamber.

[0040] The reference numerals in the drawings are respectively: 1. outer cylinder, 2. spiral flow channel, 3. end plate, 4. inner cylinder, 5. exhaust hole, 6. intake hole, 7. piston chamber, 8. sealing assembly, 9. step surface, 10. piston rod hole, 11. disc spring assembly, 12. circulation pipeline, 13. compression bolt, 14. pressing ring, 15. sealing ring, 16. conical section, 17. annular groove. Detailed implementation mode

[0041] The present invention will be further described in detail below in conjunction with embodiments, but the present invention is not limited to the following embodiments: Embodiment 1: As Figures 1 to 8 shown, the cylinder block structure of the wellhead natural gas compressor includes a cylinder barrel, the cylinder barrel includes an outer cylinder 1 and an inner cylinder 4, the inner cylinder 4 is embedded in the central hole of the outer cylinder 1, and the central hole of the inner cylinder 4 forms the piston chamber 7 of the cylinder barrel; Semicircular spiral grooves are provided on both the inner wall of the outer cylinder 1 and the outer wall of the inner cylinder 4, and the spiral grooves of the two enclose a spiral flow channel 2 that extends along the axis of the cylinder barrel and has a circular cross-section. The spiral flow channel 2 is provided with a medium inlet hole and a medium outlet hole on the surface of the outer cylinder 1. The medium inlet hole is used to introduce fluid into the spiral flow channel 2, and the medium outlet hole is used to discharge the medium in the spiral flow channel 2.

[0042] In this embodiment, the outer cylinder 1 is the outer layer of the cylinder barrel, and the inner cylinder 4 is the inner layer of the cylinder barrel. The outer cylinder 1 and the inner cylinder are both independent parts. After the spiral grooves on each are processed, the inner cylinder 4 is nested inside the outer cylinder 1 to assemble into a double-layer cylinder barrel structure. In this way, the spiral flow channel 2 is formed by the spiral grooves on the cylinder barrel. During the application of the cylinder block in the natural gas compression process, a heat-carrying fluid medium, such as heat-carrying oil, is introduced into the spiral flow channel 2. Since the spiral flow channel 2 extends along the axis of the cylinder barrel, the outer cylinder 1 can not only provide support for the inner cylinder 4 to ensure the effective wall thickness of the cylinder barrel, but also, the heat-carrying effect of the medium in the spiral flow channel 2 is used to form an isothermal wall on the outer wall of the inner cylinder 4, making the temperatures at each position on the outer wall of the inner cylinder 4 closer. In this way, since the heat source on the inner cylinder 4 is the compressed natural gas in the piston chamber 7, for each position on the side of the inner cylinder 4, the above-mentioned isothermal wall can effectively reduce the difference in the temperature difference between the inner and outer sides at each position of the inner cylinder 4. From the perspective of thermal deformation, this solution can effectively reduce the temperature difference at different positions on the inner wall of the cylinder, achieve the purpose of reducing piston ring air leakage and optimizing the compressor volume, and achieve the purpose of reducing the deformation at different positions on the inner wall of the cylinder and optimizing the vibration during the operation of the compressor.

[0043] Meanwhile, regarding the pressure-bearing capacity of the cylinder block, this solution provides a technical solution in which the cylinder barrel is designed to include an outer cylinder barrel 1 and an inner cylinder barrel 4, and spiral grooves are respectively provided on the inner wall of the outer cylinder barrel 1 and the outer wall of the inner cylinder barrel 4. The spiral flow channel 2 is formed by the spiral grooves. Such a technical solution can not only utilize traditional casting and forging to process the outer cylinder barrel 1 and the inner cylinder barrel 4 with excellent quality. At the same time, the spiral grooves are surface structures on the inner wall of the outer cylinder barrel 1 and the outer wall of the inner cylinder barrel 4, and can be integrally formed on the outer cylinder barrel 1 and the inner cylinder barrel 4 by methods such as casting, or after the cylindrical basic structures of the outer cylinder barrel 1 and the inner cylinder barrel 4 are formed, the spiral groove processing can be completed by further machining on the basis of this basic structure. Therefore, this solution also has the characteristics of effectively guaranteeing the performance of the cylinder block and facilitating processing.

[0044] It is easy to understand that the medium inlet hole and the medium outlet hole are respectively used as the channels for introducing the medium into the spiral flow channel 2 and the channels for discharging the medium in the spiral flow channel 2. As those skilled in the art, the connection positions of the medium inlet hole and the medium outlet hole on the spiral flow channel 2 should be located at different positions of the spiral flow channel 2, so that the medium can flow along the spiral flow channel 2 in a spiral shape to cover different circumferential positions and axial positions of the inner cylinder barrel 4, and form the isothermal wall on the outer wall of the inner cylinder barrel 4. At the same time, as those skilled in the art, when the medium flows along the spiral flow channel 2, if the temperature of the medium when it enters the cylinder barrel is lower than the exhaust temperature of the cylinder barrel and higher than the intake temperature of the cylinder barrel, since the gases entering and leaving the cylinder block will cause different heat dissipation conditions and temperatures at different positions of the cylinder block, this will cause the medium to absorb and release heat to different degrees at different positions during the flow process, that is, the medium at different positions of the spiral flow channel 2 has a certain temperature difference. Therefore, the understanding of the isothermal wall should be that the medium in the spiral flow channel 2 has the function of balancing the temperature differences at different axial positions and circumferential positions on the outer wall of the inner cylinder barrel 4, which is beneficial to isothermal from the perspective of heat dissipation conditions, but it cannot be understood that the temperatures at different positions on the outer wall of the inner cylinder barrel 4 can be completely the same.

[0045] In a specific embodiment, the spiral groove on the inner wall of the outer cylinder barrel 1 starts from the inner wall at one end and spirally runs on this inner wall with the axis of the outer cylinder barrel 1 as the center line, and ends at the inner wall at the other end of the outer cylinder barrel 1. The spiral groove on the outer wall of the inner cylinder barrel 4 starts from the outer wall at one end and spirally runs on this outer wall with the axis of the inner cylinder barrel 4 as the center line, and ends at the outer wall at the other end. The spiral flow channel 2 extends from the end of the cylinder barrel where the piston rod hole 10 is provided to the end of the cylinder barrel where the end plate 3 is provided. In the axial direction of the cylinder barrel axis, the piston cavity 7 is located between the two ends of the spiral flow channel 2, so that the spiral flow channel 2 can fully cover the lateral heat dissipation surface of the piston cavity 7 and enable the spiral flow channel 2 to provide comprehensive uniform temperature protection against uneven deformation for the inner cylinder barrel 4 outside the piston cavity 7.

[0046] Embodiment 2: This embodiment is further refined on the basis of Embodiment 1: The inner cylinder 4 is a cylindrical structure with a piston rod hole 10 communicating with the piston cavity 7 at one end and a stepped shaft shape, and the central hole of the outer cylinder 1 is a stepped hole with a stepped surface 9; One end of the inner cylinder 4 provided with the piston rod hole 10 is supported on the stepped surface 9, and the other end of the inner cylinder 4 is embedded in the outer cylinder 1; It further includes an end plate 3 bolted to the outer cylinder 1. The end plate 3 is connected to the end of the outer cylinder 1 away from the piston rod hole 10. A boss inserted into the inner cylinder 4 is provided at the inner end of the end plate 3, and the inner end surface of the end plate 3 supports the other end of the inner cylinder 4 through a disc spring assembly 11.

[0047] The above provides a specific cylinder assembly scheme. The piston cavity 7 is the working cavity of the piston ring in the compressor, and the piston rod on the piston ring cooperates with the piston rod hole 10. In this scheme, the constraint of the inner wall of the outer cylinder 1 on the outer wall of the inner cylinder 4 is used to realize the position constraint between the outer cylinder 1 and the inner cylinder 4 in the radial direction of the cylinder. One end of the inner cylinder 4 provided with the piston rod hole 10 is supported on the stepped surface 9 of the outer cylinder 1 through the shoulder structure at this end, and the other end of the inner cylinder 4 is supported on the end plate 3 through the disc spring assembly 11, so as to realize the position constraint between the outer cylinder 1 and the inner cylinder 4 in the axial direction of the cylinder.

[0048] At the same time, the end plate 3, as the cylinder head on the cylinder, after being fixed to the outer cylinder 1, can not only support the inner cylinder 4 through the disc spring assembly 11 to prevent the inner cylinder 4 from moving around in the central hole of the outer cylinder 1, but also, the boss inserted into the inner cylinder 4 on it is used to control the clearance size of the piston cavity 7.

[0049] The above scheme realizes the position constraint of the inner cylinder 4 in the central hole of the outer cylinder 1 with a simple structure. At the same time, for the axial deformation generated by the inner and outer cylinders 1 during the working process, not only can the thrust of the disc spring assembly 11 on the inner cylinder 4 be used to keep the inner cylinder 4 having a stable axial position relative to the outer cylinder 1, but also, through the compression deformation generated on the disc spring assembly 11, the thermal deformation of the cylinder can be adapted and the thermal stress can be released, so that the cylinder block structure of the present invention is not only simple in structure, but also has reliable structural stability and the generated thermal stress can be reliably released.

[0050] Embodiment 3: This embodiment is further refined on the basis of Embodiment 1: An air inlet hole 6 and an exhaust hole 5 are provided on the cylinder, and each end of the cylinder has an air inlet hole 6 and an exhaust hole 5; The intake hole 6 and the exhaust hole 5 are both configured such that the outer cylinder 1 has an outer hole section, and the inner cylinder 4 has an inner hole section, and the outer hole section and the inner hole section are docked with each other; Each intake hole 6 and exhaust hole 5 is provided with a sealing assembly 8. The sealing assemblies 8 for the intake hole 6 and the exhaust hole 5 respectively are configured such that the sealing assembly 8 is located at the position where the outer hole section and the inner hole section are docked with each other. The sealing assembly 8 has a sealing ring 15 that extends in the circumferential direction of the docking position and is located on the outer periphery of the docking position. The sealing ring 15 serves as a sealing isolation structure for the gap between itself and the cylinder, and the gap is the gap between the outer cylinder 1 and the inner cylinder 4.

[0051] The above provides a technical solution with specific intake and exhaust. Specifically, the inner hole section at the above docking position is directly communicated with the piston chamber 7. When the cylinder is set as a double-layer structure including the outer cylinder 1 and the inner cylinder 4, the intake hole 6 and the exhaust hole 5 on the cylinder are both formed by the docking of the outer hole section on the outer cylinder 1 and the inner hole section on the inner cylinder 4. For the gap on the mating surface between the inner and outer cylinders 1, even if the inner cylinder 4 is expanded and joined to the outer cylinder 1 with strength (the outer diameter of the inner cylinder 4 is larger than the inner diameter of the central hole of the outer cylinder 1 at room temperature), under the influence of processing errors, inevitable vibrations during the operation of the compressor, and thermal deformation, although the intake and exhaust pressures of the wellhead natural gas compressor have the effect of preventing the medium in the spiral flow channel 2 from entering the piston chamber 7 through the gap and the inner hole section, when intake holes 6 and exhaust holes 5 are provided on both sides of the piston ring (both piston chambers 7 on both sides of the piston ring serve as compression working chambers, and for any movement direction of the piston ring, one side of the piston chamber 7 intakes air and the other side of the piston chamber 7 compresses), there is a significant pressure difference on both sides of the piston ring. In this way, possible phenomena include that the piston chamber 7 on the compression side of the piston ring pressurizes the gap through the inner hole section. When this pressure exceeds the sealing ability of the mating surface between the inner and outer cylinders 1, the medium in the spiral flow channel 2 enters the piston chamber 7 on the intake side of the piston ring through the inner hole section, ultimately causing the occurrence of a liquid hammer phenomenon in the compressor. At the same time, the gas in the piston chamber 7 entering the mating surface and flowing into the spiral flow channel 2 will also lead to a reduction in the efficiency of the compressor. Based on the above, the technical solution of the sealing assembly 8 is provided.

[0052] Specifically, the sealing assembly 8 is used to provide the sealing ring 15 for the docking position, specifically: forming an annular sealing surface on the outer periphery of the outer orifice of the inner hole section to prevent the compressed gas in the piston chamber 7 from entering the gap on the mating surface, causing an increase in the internal pressure of the gap, ultimately resulting in the medium between the outer cylinder 1 and the inner cylinder 4 entering the intake side of the piston chamber 7 and causing the occurrence of a liquid hammer phenomenon during the compression stage on the intake side, and at the same time avoiding the reduction of the working efficiency of the compressor caused by fluid flow or leakage of compressed gas on the compression side.

[0053] In a specific implementation, since the inner cylinder 4 needs to be embedded in the outer cylinder 1 and the outer cylinder 1 serves as a supporting layer for the inner cylinder 4, the outer wall of the inner cylinder 4 is preferably a cylindrical surface. In this way, the mating surfaces of the outer cylinder 1 and the inner cylinder 4 at the position where the side hole section and the inner hole section are butted against each other are also cylindrical surfaces that fit each other. Therefore, unlike the shape of the traditional flat-plate sealing ring 15, the sealing plate in this scheme needs to fit the outer surface of the inner cylinder 4 and extend in the circumferential direction of the outer hole opening of the inner hole section. The sealing plate is an arc-shaped plate structure that fits the cylindrical surface of the outer cylinder 1. Since the compressor processes corrosive media, the sealing ring 15 must be selected as a material resistant to acid corrosion, such as a rubber sealing structure with a skeleton inside.

[0054] Embodiment 4: This embodiment is further refined on the basis of Embodiment 3: The sealing assembly 8 also includes a compression ring 14 and a plurality of compression bolts 13; Each sealing assembly 8 is provided with an annular groove 17 on the outer cylinder 1. The annular groove 17 is located at the outer periphery of the outer hole section and intersects with the outer hole section to form a stepped hole. The pressure ring 14 and the sealing ring 15 are both installed in the annular groove 17. The compression ring 14 is stacked on the outside of the sealing ring 15, the inside of the sealing ring 15 is attached to the outer wall of the inner cylinder 4, the side of the sealing ring 15 is attached to the groove wall of the ring groove 17, the clamping bolts 13 are arranged at intervals along the circumferential direction of the compression ring 14, and each clamping bolt 13 is threadedly connected to the outer cylinder 1, and the inner end of each clamping bolt 13 acts on the outer surface of the compression ring 14 and provides the compression ring 14 with an extrusion force toward the sealing ring 15; The outer end of the sealing ring 15 has an annular groove, and the inner end of the pressure ring 14 has a conical section 16 whose outer shape matches the shape of the groove, and the conical section 16 is embedded in the groove.

[0055] The above provides a specific structure of the sealing component 8. The pressing bolts 13 fastened to the outer cylinder 1 provide a thrust force towards the sealing ring 15 for the pressing ring 14, so that the sealing ring 15 obtains the extrusion force. Before the inner cylinder 4 is inserted into the central hole of the outer cylinder 1, the pressing ring 14 and the sealing ring 15 can be integrally formed by adhesive connection, and then the integral structure is pasted on the outer end face of the annular groove 17. After the inner cylinder 4 is inserted into the outer cylinder 1 in place, the pressing bolts 13 are tightened through the air inlet hole 6 and the exhaust hole 5, and the integral structure is pushed towards the inner cylinder 4 so that the sealing ring 15 fits against the outer wall of the inner cylinder 4. In this solution, it is further set that the outer end of the sealing ring 15 has a groove, and the inner end of the pressing ring 14 has a tapered section 16 adapted to the groove. In this way, during the movement of the pressing ring 14 towards the sealing ring 15, the pressing ring 14 can not only provide an extrusion force in the radial direction of the cylinder for the sealing ring 15, but also provide an extrusion force in the axial direction of the cylinder for the outer edge of the sealing ring 15. In this way, a sealing surface is formed between the inner end face of the sealing ring 15 and the outer wall of the inner cylinder 4, and a sealing surface is formed between the side surface of the sealing ring 15 and the side surface of the annular groove 17, realizing reliable sealing of the butt joint position.

[0056] In a specific implementation manner, the pressing ring 14 is also an arc-shaped plate structure adapted to the curvature of the outer surface of the inner cylinder 4. In such an application, since the outer hole section is preferably set as a flat-bottom hole convenient for installing the intake and exhaust valves, for the pressing bolts 13 at different positions of the pressing ring 14, at the same time, to avoid the exposure of the pressing bolts 13 affecting the installation of the intake and exhaust valves, a preferred solution is to install the pressing bolts 13 so that the outer ends are sunken relative to the bottom of the flat-bottom hole. In such an application, pressing bolts 13 with multiple length parameters should be used.

[0057] Example 5: This embodiment is further refined on the basis of Embodiment 1: The inner cylinder 4 is a cast iron cylinder, the outer cylinder 1 is an aluminum alloy cylinder, and the inner cylinder 4 is expanded and connected in the outer cylinder 1.

[0058] The above solution provides a form of the inner cylinder 4, a form of the outer cylinder 1, and an assembly method of the cylinders. Specifically, the inner cylinder 4 is made of cast iron with a small coefficient of thermal expansion and good wear resistance, such as ductile iron, to ensure its sealing ability with the piston ring at high temperatures. The outer layer is made of aluminum alloy with high thermal conductivity and low heat capacity per unit volume. By reducing the heat capacity of the outer cylinder 1 and strengthening heat transfer, the maximum temperature of the outer cylinder 1 and the temperature difference at different positions are reduced, so that each position on the side of the cylinder has relatively balanced heat dissipation conditions, achieving the purpose of reducing the non-uniform thermal deformation occurring on the outer cylinder 1. The inner cylinder 4 is expanded and connected to the outer cylinder 1, which is a form of pre-stressed installation of the cylinders, to cope with the characteristic that the coefficient of thermal expansion of aluminum alloy is significantly greater than that of cast iron, strengthening the tightness of the cooperation between the outer cylinder 1 and the inner cylinder 4 during the operation of the compressor, and avoiding the generation of gaps between the inner and outer cylinders 1 to ensure the supporting ability of the outer cylinder 1 for the inner cylinder 4.

[0059] Embodiment 6: This embodiment is further refined on the basis of Embodiment 1: The number of the spiral flow channels 2 is 1. In the axial direction of the cylinder, both the air inlet position and the air outlet position of the piston chamber 7 are within the coverage area of the spiral flow channel 2, and the coverage area is the area between the two ends of the spiral flow channel 2 on the cylinder. The number of the medium introduction holes is 1, and the conduction position of the medium introduction hole and the spiral flow channel 2 is in the middle of the axial direction of the spiral flow channel 2. The number of the medium outlet holes is 2, and each end of the spiral flow channel 2 is provided with a medium outlet hole.

[0060] The above provides a specific form of setting the spiral flow channel 2. The setting of the end positions of the spiral flow channel 2 and the air inlet and outlet positions of the piston chamber 7 in the axial direction of the cylinder aims to utilize the isothermal wall effect exerted by the spiral flow channel 2 to evenly distribute the heat dissipation conditions at the air inlet and outlet positions of the piston chamber 7, achieving the purpose of controlling the non-uniform deformation amount of the inner cylinder 4 in the hot state. The air inlet and outlet positions are the connection positions of the above-mentioned air inlet hole 6 and exhaust hole 5 on the piston chamber 7 respectively. The setting method of the medium introduction hole and the medium outlet hole aims to achieve: for this spiral flow channel 2, the fluid introduced from the middle of the spiral flow channel 2 can flow to both sides of the spiral flow channel 2 and flow out from the medium outlet holes at both ends of the spiral flow channel 2 respectively. In the spiral flow channel 2, for the fluid flowing to each side, the flow path of the fluid from introduction to outlet is short, and the two-way flow is symmetric with respect to the middle of the cylinder length direction. Therefore, this solution can not only reduce the temperature difference of the fluid at different positions in the spiral flow channel 2 and reduce the non-uniform deformation occurring on the inner cylinder 4, but also the structure of the required circulation pipeline 12 is simple.

[0061] Such as Figure 7As shown, the arrows in the attached drawing are used to indicate the fluid inlet position and outlet position on the cylinder barrel. In this attached drawing, the arrow in the center of the lower cylinder block indicates the fluid inlet position where the fluid is introduced into the spiral flow channel 2, and the arrows at both ends of the upper cylinder block indicate the fluid outlet positions where the fluid is led out from the spiral flow channel 2.

[0062] Embodiment 7: This embodiment is further refined on the basis of Embodiment 1: The number of the spiral flow channels 2 is greater than 1, and the spiral flow channels 2 are arranged in sequence along the axial direction of the cylinder barrel. In the axial direction of the cylinder barrel, both the air inlet position and the air outlet position of the piston chamber 7 are within the coverage area of the spiral flow channels 2. The coverage area is the distribution area of the spiral flow channels 2 on the cylinder barrel axis, and the spiral flow channels 2 are independent of each other; Each spiral flow channel 2 is configured with a medium inlet hole at one end and a medium outlet hole at the other end.

[0063] The above provides a specific setting form of the spiral flow channel 2, which is an equivalent solution to the case where the number of spiral flow channels 2 in Embodiment 6 is 1. Specifically, different spiral flow channels 2 are located at different axial positions of the cylinder barrel. For the heat dissipation conditions of these different axial positions (for example, the air inlet hole 6 has good heat dissipation conditions because the inlet air temperature is low and the flow rate is large, and this area of the cylinder barrel is the cold area on the cylinder barrel; the exhaust hole 5 has poor heat dissipation conditions because the exhaust temperature is high and the flow rate is large, and this area of the cylinder barrel is the hot area on the cylinder barrel), by introducing fluids with different temperatures or different flow rates into these spiral flow channels 2, the purpose of adjusting to reduce the temperature difference of the fluids at different positions in the spiral flow channels 2 and reducing the non-uniform deformation occurring on the inner cylinder barrel 4 can be achieved; on the other hand, using two or more spiral flow channels 2 to cover the coverage area of the spiral flow channels 2 on the cylinder barrel, compared with the technical solution adopted in Embodiment 6, the flow path of the fluid in a single spiral flow channel 2 is shortened. In this way, the temperature difference between the medium inlet hole position and the medium outlet hole position of the spiral flow channel 2 can be reduced. Compared with a single spiral flow channel 2, such a configuration has a better temperature equalizing effect on the inner cylinder barrel 4.

[0064] Embodiment 8: This embodiment is further refined on the basis of Embodiment 1: It further includes a circulation system connected to the spiral flow channel 2 through a circulation pipeline 12. The circulation system, the circulation pipeline 12, and the spiral flow channel 2 form an annular medium circulation loop. The spiral flow channel 2 is connected in series in the medium circulation loop, and the circulation pipeline 12 is connected to the spiral flow channel 2 through the medium inlet hole and the medium outlet hole; The circulation system includes a pump and a cooler connected in series in the medium circulation loop. The pump serves as the power equipment for the medium to circulate in the medium circulation loop, and the cooler is used to cool the medium in the medium circulation loop.

[0065] As described above, a technical solution is provided for supplying circulating fluid to the spiral flow channel 2 of the cylinder barrel by using a circulating system. In specific implementation, considering heat dissipation of the cylinder barrel and optimizing non-uniform deformation of the inner cylinder barrel 4 by reducing the temperature difference between the inlet and outlet fluids of the spiral flow channel 2, a preferable application is that the initial temperature of the fluid injected into the spiral flow channel 2 is the intermediate value of the inlet and outlet gas temperatures of the compressor. By adopting the said circulating system, not only can the fluid be reused repeatedly, but also the temperatures of the fluid introduced into and drawn out from the spiral flow channel 2 can be adjusted through regulating the cooling capacity of the cooler and the pump flow rate.

[0066] In a specific implementation manner, since it is possible for the gas in the piston chamber 7 to enter the spiral flow channel 2 through the mating surface, if this part of the gas does not enter the low-pressure side of the piston ring in the piston chamber 7, it will not have a substantial impact on the safe operation of the compressor, but this will increase the possibility of liquid hammer and lead to a decrease in the operating efficiency of the compressor. Based on this, a microbubble sensor for detecting whether there are bubbles in the liquid phase is arranged in the circulating pipeline 12 connected to the medium outlet hole, so as to monitor the operating conditions of the compressor according to the detection result of the microbubble sensor and avoid serious operating failures of the compressor.

[0067] Example 9: On the basis of Example 1, this embodiment provides a wellhead natural gas compressor, including a cylinder for realizing natural gas compression, and the cylinder includes a cylinder block structure and a piston assembly installed in the cylinder block structure, and the cylinder block structure is the cylinder block structure described in Example 1; The compression working chamber of the piston chamber 7 has an air outlet position at the bottom side of the piston chamber 7.

[0068] The compressor is a piston compressor including the cylinder block structure, which is a specific application of the cylinder block structure. As described above, if both piston chambers 7 on both sides of the piston ring have air inlet holes 6 and air outlet holes, it should be considered that both piston chambers 7 on both sides of the piston ring are the compression working chambers. The above solution that the compression working chamber has an air outlet position at the bottom side of the piston chamber 7 aims to achieve: when there is liquid in the compression working chamber, it can be discharged in time through this outlet position along with the exhaust gas to avoid serious liquid hammer failures of the compressor.

[0069] Example 10: On the basis of Example 9, this embodiment provides a working method for a wellhead natural gas compressor, and the compressor is the compressor described in Example 9, and the working method is as follows: During the process of the compressor compressing the wellhead natural gas, a heat-carrying medium is introduced into the spiral flow channel 2 and the heat-carrying medium flows along the spiral flow channel 2 to balance the temperatures at various positions on the outer periphery of the inner cylinder barrel 4.

[0070] The working method described above is the compressor operation method based on the compressor structure. As described above, this solution aims to utilize the fluid in the spiral flow channel 2 to form an isothermal wall on the outer periphery of the inner cylinder 4. This isothermal wall reduces the non-uniform deformation occurring on the inner cylinder 4 during the operation of the compressor by equalizing the heat dissipation conditions and temperatures at various positions of the inner cylinder 4, thereby achieving the purpose of reducing piston ring air leakage and optimizing the compressor volume, and achieving the purpose of reducing the deformation at different positions on the inner wall of the cylinder and optimizing the vibration during the operation of the compressor.

[0071] The above content is a further detailed description of the present invention in combination with specific preferred embodiments. It cannot be determined that the specific embodiments of the present invention are only limited to these descriptions. For those of ordinary skill in the technical field to which the present invention pertains, other embodiments obtained without departing from the technical solution of the present invention should all be included within the protection scope of the present invention.

Claims

1. The cylinder block structure of the wellhead natural gas compressor, including a cylinder barrel, is characterized in that The cylinder comprises an outer cylinder (1) and an inner cylinder (4), wherein the inner cylinder (4) is embedded in the center hole of the outer cylinder (1), and the center hole of the inner cylinder (4) forms a piston chamber (7) of the cylinder; The inner wall of the outer cylinder (1) and the outer wall of the inner cylinder (4) are both provided with a spiral groove with a semi-circular cross section, and the spiral grooves of the two surround a spiral flow channel (2) extending along the axis of the cylinder and having a circular cross section. The spiral flow channel (2) is provided with a medium introduction hole and a medium outlet hole located on the surface of the outer cylinder (1), the medium introduction hole is used to introduce fluid into the spiral flow channel (2), and the medium outlet hole is used to outlet the medium in the spiral flow channel (2).

2. The cylinder block structure of the wellhead natural gas compressor according to claim 1, wherein The inner cylinder (4) is a cylindrical structure with a piston rod hole (10) at one end communicating with the piston chamber (7) and a stepped shaft shape, and the center hole of the outer cylinder (1) is a stepped hole with a stepped surface (9); One end of the inner cylinder (4) provided with a piston rod hole (10) is supported on the step surface (9), and the other end of the inner cylinder (4) is embedded in the outer cylinder (1); It also includes an end plate (3) bolted to the outer cylinder (1), the end plate (3) being connected to one end of the outer cylinder (1) away from the piston rod hole (10), the inner end of the end plate (3) being provided with a boss inserted into the inner cylinder (4), and the inner end surface of the end plate (3) supporting the other end of the inner cylinder (4) via a disc spring assembly (11).

3. The cylinder block structure of the wellhead natural gas compressor according to claim 1, characterized in that, The cylinder is provided with an air inlet hole (6) and an air outlet hole (5), and each end of the cylinder has an air inlet hole (6) and an air outlet hole (5); The air inlet (6) and the air outlet (5) are each provided with an outer hole section on the outer cylinder (1) and an inner hole section on the inner cylinder (4), and the outer hole section and the inner hole section are butted against each other; Each air inlet hole (6) and air outlet hole (5) is provided with a sealing assembly (8), and each of the air inlet hole (6) and the air outlet hole (5) has the following characteristics: the sealing assembly (8) is located at a position where the outer hole section and the inner hole section are butted against each other, the sealing assembly (8) has a sealing ring (15) extending in a circumferential direction of the butting position and located at the outer periphery of the butting position, and the sealing ring (15) serves as a sealing isolation structure for each of the gaps with the cylinder barrel, and the gap is the gap between the outer cylinder barrel (1) and the inner cylinder barrel (4).

4. The cylinder block structure of the wellhead natural gas compressor according to claim 3, characterized in that, The sealing assembly (8) further comprises a pressure ring (14) and a plurality of clamping bolts (13); Each sealing assembly (8) is provided with an annular groove (17) located on the outer cylinder (1), the annular groove (17) being located on the outer periphery of the outer hole section and intersecting with the outer hole section to form a stepped hole, and the pressure ring (14) and the sealing ring (15) are both installed in the annular groove (17); The pressing ring (14) is stacked outside the sealing ring (15). The inner side of the sealing ring (15) is attached to the outer wall of the inner cylinder barrel (4). The side surface of the sealing ring (15) is in contact with the groove wall of the annular groove (17). The pressing bolts (13) are arranged at intervals along the circumferential direction of the pressing ring (14). Each pressing bolt (13) is threadedly connected to the outer cylinder barrel (1). The inner end of each pressing bolt (13) acts on the outer surface of the pressing ring (14) and provides a pressing force for the pressing ring (14) towards the sealing ring (15). The outer end of the sealing ring (15) has an annular groove, and the inner end of the pressing ring (14) has a tapered section (16) whose outer shape is adapted to the shape of the groove, and the tapered section (16) is embedded in the groove.

5. The cylinder block structure of the wellhead natural gas compressor according to any one of claims 1 to 4, characterized in that, The inner cylinder barrel (4) is a cast iron barrel, and the outer cylinder barrel (1) is an aluminum alloy barrel. The inner cylinder barrel (4) is expansion-connected to the outer cylinder barrel (1).

6. The cylinder block structure of the wellhead natural gas compressor according to any one of claims 1 to 4, characterized in that, The number of the spiral flow channels (2) is 1. In the axial direction of the cylinder barrel, the air inlet position and the air outlet position of the piston chamber (7) are both within the coverage area of the spiral flow channel (2), and the coverage area is the area between the two ends of the spiral flow channel (2) on the cylinder barrel. The number of the medium introduction holes is 1, and the conduction position of the medium introduction hole and the spiral flow channel (2) is in the middle of the axial direction of the spiral flow channel (2). The number of the medium outlet holes is 2, and each end of the spiral flow channel (2) is provided with a medium outlet hole.

7. The cylinder block structure of the wellhead natural gas compressor according to any one of claims 1 to 4, characterized in that, The number of the spiral flow channels (2) is greater than 1. The spiral flow channels (2) are arranged in sequence along the axial direction of the cylinder barrel. In the axial direction of the cylinder barrel, the air inlet position and the air outlet position of the piston chamber (7) are both within the coverage area of the spiral flow channels (2), and the coverage area is the distribution area of the spiral flow channels (2) on the axis of the cylinder barrel. The spiral flow channels (2) are independent of each other. Each spiral flow channel (2) is configured with a medium introduction hole at one end and a medium outlet hole at the other end.

8. The cylinder block structure of the wellhead natural gas compressor according to any one of claims 1 to 4, characterized in that, It further includes a circulation system connected to the spiral flow channel (2) through a circulation pipeline (12). The circulation system, the circulation pipeline (12) and the spiral flow channel (2) form an annular medium circulation loop. The spiral flow channel (2) is connected in series in the medium circulation loop. The circulation pipeline (12) is connected to the spiral flow channel (2) through the medium introduction hole and the medium outlet hole. The circulation system includes a pump and a cooler connected in series in the medium circulation loop. The pump serves as the power equipment for the medium to circulate in the medium circulation loop, and the cooler is used to cool down the medium in the medium circulation loop.

9. Wellhead natural gas compressor, including a cylinder for realizing natural gas compression, the cylinder including a cylinder block structure and a piston assembly installed in the cylinder block structure, characterized in that, The cylinder block structure is the cylinder block structure provided in any one of claims 1 to 8. The compression working chamber of the piston chamber (7) has an air outlet position located at the bottom side of the piston chamber (7).

10. The working method of a wellhead natural gas compressor, characterized in that, The compressor is the compressor described in claim 9, and the working method is as follows: During the process of the compressor compressing the wellhead natural gas, a heat-carrying medium is introduced into the spiral flow channel (2), and the heat-carrying medium flows along the spiral flow channel (2) to balance the temperatures at various positions on the outer periphery of the inner cylinder barrel (4).

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