Wellhead natural gas compressor cylinder structure, compressor and working method thereof

Abstract

The present invention discloses a wellhead natural gas compressor cylinder structure, a compressor, and a working method thereof, relating to the technical field of compressors. The cylinder structure includes a cylinder barrel, which includes an outer cylinder barrel and an inner cylinder barrel. The inner cylinder barrel is embedded in the center hole of the outer cylinder barrel, and the center hole of the inner cylinder barrel forms the piston chamber of the cylinder barrel. The inner wall of the outer cylinder barrel and the outer wall of the inner cylinder barrel are both provided with spiral grooves with a semi-annular cross section. The spiral grooves of the two form a spiral flow channel extending along the axis of the cylinder barrel and having a circular cross section. The spiral flow channel is provided with a medium introduction hole and a medium outlet hole located on the surface of the outer cylinder barrel. The compressor includes the cylinder structure, and the working method is the working method of the compressor. This solution can effectively reduce the temperature difference at different positions of the inner wall of the cylinder, thereby achieving the purpose of reducing piston ring leakage and optimizing the volume of the compressor, and achieving the purpose of reducing deformation at different positions of the inner wall of the cylinder and optimizing the vibration during the operation of the compressor.

Description

Technical Field

[0001] The present invention relates to the technical field of compressors, and in particular to a wellhead natural gas compressor cylinder structure, 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 pipe. In the prior art, compressors for this purpose mostly use positive displacement compressors, such as piston compressors, and are assembled into a skid-mounted compressor unit with separators, buffers, coolers, etc. in a skid-mounted manner and installed near the wellhead. The basic configuration of the commonly used compressor is provided in the patent document with the publication (announcement) number CN202811255U. The specific application can be as follows: the crankshaft is driven to rotate by a variable frequency motor, and multiple crossheads are staggered in the circumference of the crankshaft. Each crosshead is connected to a piston ring through a piston rod, and each piston ring is arranged in a cylinder 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 needs of large-flow processing 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 wide processing capacity adjustment capabilities, the ability to adapt to wellhead gas pressure fluctuations, and explosion-proof capabilities. At the same time, since compressors for this purpose may have the characteristics of continuous high-load operation, and the medium flow has a higher probability of entraining liquids, fine particles and even corrosive liquids, in order to solve the problems of difficult maintenance and high safety hazards in remote areas and ensure continuous production of wellhead gas, the design of the compressor unit has high requirements for the reliability and life of the filter and separator. The design of the compressor has high requirements for vibration control, fault monitoring and prediction.

[0004] Existing techniques for vibration control include cylinder temperature control, most commonly using external cooling to enhance cylinder heat dissipation. This approach reduces temperature differences between different cylinder regions to a certain extent. To optimize the performance and service life of imported natural gas compressors, further optimization of the compressor structure is necessary. Summary of the Invention

[0005] In response to the aforementioned problem of optimizing the compressor structure, the present invention provides a wellhead natural gas compressor cylinder structure, a compressor, and an operating method thereof. This solution can effectively reduce temperature differences at different locations on the cylinder inner wall, thereby reducing piston ring leakage, optimizing compressor volume, and reducing deformation at different locations on the cylinder inner wall, thereby optimizing vibration during compressor operation.

[0006] In response to the above problems, the present invention provides a wellhead natural gas compressor cylinder structure, a compressor, and an operating method thereof to solve the problems through the following technical points: the wellhead natural gas compressor cylinder structure includes a cylinder barrel, the cylinder barrel includes an outer cylinder barrel and an inner cylinder barrel, the inner cylinder barrel is embedded in the center hole of the outer cylinder barrel, and the center hole of the inner cylinder barrel forms a piston cavity of the cylinder barrel;

[0007] Both the inner wall of the outer cylinder and the outer wall of the inner cylinder are provided with a spiral groove with a semi-annular cross section. The spiral grooves of the two form a spiral flow channel extending along the axis of the cylinder and having a circular cross section. The spiral flow channel is provided with a medium inlet hole and a medium outlet hole located on the surface of the outer cylinder. The medium inlet hole is used to introduce fluid into the spiral flow channel, and the medium outlet hole is used to outlet the medium from the spiral flow channel.

[0008] In the existing technology, piston compressors are widely used for wellhead natural gas compression. This type of compressor is particularly suitable for high pressure (greater than 15 MPa) and situations with large fluctuations in wellhead gas pressure (such as shale gas wells). For piston compressor cylinder cooling, external cooling is usually used to cool the cylinder, such as setting heat dissipation fins on the outer wall of the cylinder, configuring air cooling mechanisms or liquid cooling mechanisms for the cylinder, etc. This solution has the effect of reducing the temperature difference between different areas of the cylinder to a certain extent. However, since the natural gas compressor processes a large flow rate and there is a significant difference between the intake and outlet temperatures, for the intake and outlet areas of the cylinder, due to the asymmetric heat conduction at these locations, this heat dissipation method has little effect on the temperature at different locations on the inner wall of the cylinder, causing uneven deformation of the cylinder and thus causing compressor vibration. Specifically:

[0009] Regarding the vibration of the piston wellhead natural gas compressor during operation, one of the causes is the uneven local temperature distribution on the cylinder: an air inlet and an exhaust port are respectively provided at both ends of the cylinder, so that when the piston moves, the space at one end of the piston ring is inhaled and the space at the other end is compressed, so as to improve the working efficiency and natural gas processing capacity. At the same time, in order to facilitate the pipe layout, the air inlet is arranged in a straight line, and the air outlet is arranged in a straight line (the air inlet and the air outlet can be arranged in a single row respectively, such as an air inlet and an air outlet are provided at each end of the cylinder, and the air inlet and the air outlet can also be arranged in two rows, such as two air inlets and two air outlets are provided at each end of the cylinder, different air inlets are located at different circumferential positions of the cylinder, and different air outlets are also located at different circumferential positions of the cylinder). The above straight lines where the air inlet and the air outlet are located are located in different directions of the cylinder. When the compressor is working, since the air inlet temperature is lower than the air outlet temperature (taking into account the compression efficiency and the dew point temperature at different pressures), the air inlet temperature is lower than the air outlet temperature. (The following sentences appear unrelated and should be omitted:) In each stage of compression, an intake temperature of 30-50°C can be used. Depending on the compression ratio, the outlet temperature can reach 150°C or even higher.) Since the above-mentioned intake and outlet ports are located at different positions of the cylinder body, the asymmetric heat conduction in different directions and the large flow rate cause the temperature in the circumferential direction of the cylinder to be uneven, resulting in local hot zones and local cold zones in different directions on the cylinder. Under the temperature difference between the hot and cold zones, the cylinder barrel deforms unevenly (from round to elliptical). According to measurements, in a specific application, the deformation difference between the hot and cold zones of a cast iron cylinder with a cylinder diameter of 400mm reached 0.6mm. The area with the most obvious elliptical deformation is located at the junction of the hot and cold zones, which causes cylinder vibration during operation. This not only accelerates the wear of the corresponding structure, but also easily leads to the formation of expandable cracks on the inner wall of the cylinder under stress cycling. At the same time, this may also cause piston ring leakage, seriously affecting the failure rate and volumetric efficiency of the compressor.

[0010] In response to the problem that the temperature difference at different positions of the cylinder causes elliptical deformation of the cylinder, which causes vibration and decreased volumetric efficiency of the compressor during operation, the above solution is provided. This solution can effectively reduce the temperature difference at different positions of the cylinder inner wall, thereby reducing piston ring leakage and optimizing the compressor volume, reducing deformation at different positions of the cylinder inner wall, and optimizing the vibration of the compressor during operation.

[0011] 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 independent parts. After the spiral grooves are processed 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 grooves on the cylinder form a spiral flow channel. When the cylinder body is used in 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 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 located on the outer wall of the inner cylinder, so that the temperatures at various positions on the outer wall of the inner cylinder are closer. In this way, since the source of heat on the inner cylinder is the compressed natural gas in the piston chamber, the above isothermal wall can effectively reduce the difference in temperature between the inside and outside of the inner cylinder at various positions on the side 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, thereby achieving the purpose of reducing piston ring leakage, optimizing the volume of the compressor, reducing deformation at different positions on the inner wall of the cylinder, and optimizing the vibration during the operation of the compressor.

[0012] At the same time, different natural gas wellheads have different wellhead pressures. The initial wellhead pressure of low-pressure gas fields and shale gas fields is relatively low. As the exploitation progresses, the wellhead gas pressure will continue to decrease. In this case, it is usually necessary to increase the pressure to 7 to 15 MPa (a piston compressor is used to pressurize it to above 15 MPa under certain small flow rates) before it is transported to the transmission pipeline. Therefore, for the cylinder design of the wellhead natural gas compressor, although the additive manufacturing method can be used to process a complex cylinder structure, the cylinder processed by this method has the problem of poor interlayer bonding strength. Therefore, in order to make the cylinder have sufficient pressure resistance while meeting the processing flow rate, in the existing production of this type of piston compressor, castings and forgings are usually used to process the cylinder. The existing integral cylinder can be obtained with cooling channels on the cylinder through subsequent reprocessing methods. However, it is difficult to process annular flow channels and spiral flow channels on the cylinder. In response to the requirement for the pressure-bearing capacity of the cylinder body, this solution provides a technical solution in which the cylinder body is designed to include an outer cylinder and an inner cylinder, and spiral grooves are respectively provided on the inner wall of the outer cylinder and the outer wall of the inner cylinder, and the spiral flow channels are surrounded by the spiral grooves. Such a technical solution can not only use traditional casting and forging to process high-quality outer cylinders and inner cylinders, but also the spiral grooves are the surface structures of the inner wall of the outer cylinder and the outer wall of the inner cylinder, which can be integrally formed on the outer cylinder and the inner cylinder by methods such as casting, or after the cylindrical basic structures of the outer cylinder and the inner cylinder are formed, the spiral grooves can be processed by further machining on the basis of the basic structure. Therefore, this solution also has the characteristics of effectively ensuring the performance of the cylinder body and convenient processing.

[0013] It is easy to understand that the medium introduction hole and the medium outlet hole serve as a channel for introducing the medium into the spiral flow channel and a channel for withdrawing the medium from the spiral flow channel, respectively. As a person skilled in the art, the connection positions of the medium introduction hole and the medium outlet hole on the spiral flow channel should be located at different positions on the spiral flow channel, so that the medium can flow along the spiral flow channel to cover different circumferential positions and axial positions of the inner cylinder, forming the isothermal wall on the outer wall of the inner cylinder. At the same time, as a person skilled in the art, when the medium flows along the spiral flow channel, if the temperature of the medium when it is introduced into the cylinder is lower than the exhaust temperature of the cylinder and higher than the intake temperature of the cylinder, the gas entering and exiting the cylinder will cause different heat dissipation conditions and temperatures at different positions of the cylinder, which 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 has a certain temperature difference. Therefore, the isothermal wall should be understood as the medium in the spiral flow channel having the function of balancing the temperature differences at different axial and circumferential positions on the outer wall of the inner cylinder, but it should not be understood as making the temperature at different positions on the outer wall of the inner cylinder completely the same.

[0014] In a specific embodiment, the spiral groove on the inner wall of the outer cylinder starts from the inner wall at one end thereof, and spirals on the inner wall with the axis of the outer cylinder as the center line, and ends on 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 thereof, and spirals on the outer wall with the axis of the inner cylinder as the center line, and ends on the outer wall at the other end. The spiral flow channel extends from one end of the cylinder where the piston rod hole is set to one end of the cylinder where the end plate is set. In the axial direction of the cylinder, 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 temperature uniformity and anti-uneven deformation protection for the inner cylinder outside the piston cavity.

[0015] A further technical solution of the cylinder structure is:

[0016] The inner cylinder is a cylindrical structure with a piston rod hole communicating with the piston cavity at one end and a stepped shaft shape. The center hole of the outer cylinder is a stepped hole with a stepped surface.

[0017] One end of the inner cylinder having the piston rod hole is supported on the step surface, and the other end of the inner cylinder is embedded in the outer cylinder;

[0018] It also includes an end plate bolted to the outer cylinder, the end plate connected to one end of the outer cylinder away from the piston rod hole, the inner end of the end plate is provided with a boss inserted into the inner cylinder, and the inner end surface of the end plate supports the other end of the inner cylinder through a disc spring assembly.

[0019] The above provides a specific cylinder assembly scheme, in which the piston cavity 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. In this scheme, 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 is provided with the piston rod hole and is supported on the step surface of the outer cylinder through the shoulder structure of the end, and the other end of the inner cylinder is supported on the end plate through the disc spring assembly, thereby realizing the position constraint of the outer cylinder and the inner cylinder in the axial direction of the cylinder.

[0020] At the same time, the end plate serves as the cylinder head on the cylinder barrel. After being fixed to the outer cylinder barrel, it can not only support the inner cylinder barrel through the disc spring assembly to prevent the inner cylinder barrel from moving in the center hole of the outer cylinder barrel, but also the boss inserted into the inner cylinder barrel is used to control the clearance size of the piston chamber.

[0021] The above scheme adopts a simple structure to realize the position constraint of the inner cylinder in the center hole of the outer cylinder. At the same time, for the axial deformation of the inner and outer cylinders generated during operation, not only can the thrust of the disc spring assembly on the inner cylinder be used to maintain the inner cylinder in a stable axial position relative to the outer cylinder, but also, by generating compression deformation on the disc spring assembly, it can adapt to the thermal deformation of the cylinder and allow thermal stress to be released, so that the cylinder body structure is not only simple in structure, but also has reliable structural stability and the generated thermal stress can be reliably released.

[0022] The cylinder is provided with an air inlet and an air outlet, and each end of the cylinder has an air inlet and an air outlet;

[0023] The air inlet and the air exhaust holes are each provided with an outer hole section on the outer cylinder and an inner hole section on the inner cylinder, and the outer hole section and the inner hole section are butted against each other;

[0024] Each air inlet and exhaust hole is equipped with a sealing assembly, and the sealing assembly of each air inlet and exhaust hole is: the sealing assembly is located at the position where the outer hole section and the inner hole section are docked with each other, and the sealing assembly has a sealing ring extending along the circumferential direction of the docking position and located on the outer periphery of the docking position. The sealing ring 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 and the inner cylinder barrel.

[0025] The above provides a technical solution with specific intake and exhaust functions. Specifically, in the existing cylinder intake and exhaust solutions, it is generally configured that both the intake and exhaust holes are stepped holes. The inner side of the stepped hole is reduced in diameter and communicates with the piston cavity. Inlet and exhaust valves are installed on the outer side of the stepped hole. The inner hole section at the above docking position is directly connected to the piston cavity. Therefore, when the cylinder is configured as a double-layer structure including an outer cylinder and an inner cylinder, the intake and exhaust holes on the cylinder are formed by the outer hole section on the outer cylinder and the inner hole section on the inner cylinder docking with each other. As for the gap on the mating surface between the inner and outer cylinders, even if the inner cylinder is expanded into the outer cylinder with strength (the outer diameter of the inner cylinder is larger than the inner diameter of the center hole of the outer cylinder 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 from entering the piston cavity through the gap and the inner hole section, when the cylinder on both sides of the piston ring is provided with intake and exhaust holes, When the piston ring is in a state of high pressure, the piston chamber on both sides of the piston ring is used as a compression working chamber. In any direction of movement of the piston ring, the piston chamber on one side is intake and the piston chamber on the other side is compressed. There is an obvious pressure difference on both sides of the piston ring. In this way, the following phenomena may occur: the piston chamber on the compression side of the piston ring pressurizes the gap through the inner hole section. When the pressure exceeds the sealing capacity of the mating surfaces of the inner and outer cylinder barrels, the medium in the spiral flow channel enters the piston chamber on the intake side of the piston ring through the inner hole section, and finally causes the occurrence of liquid hammer in the compressor. At the same time, the gas in the piston chamber enters the mating surface and flows into the spiral flow channel, which also leads to a decrease in the efficiency of the compressor. Based on the above, a technical solution for the sealing assembly is provided.

[0026] Specifically, the sealing assembly 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, causing the internal pressure of the gap to increase, and eventually 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 compressor liquid hammer during the compression stage on the intake side, while avoiding fluid channeling or gas leakage on the compression side that leads to a reduction in the working efficiency of the compressor.

[0027] In a specific implementation, since the inner cylinder needs to be embedded in the outer cylinder and the outer cylinder serves as a support 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 docked with 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 solution needs to fit with 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 with the cylindrical surface of the outer cylinder. Since the medium processed by the compressor contains corrosive media, the sealing ring must be selected from a material resistant to acid corrosion, such as a rubber sealing structure with a skeleton inside.

[0028] The sealing assembly also includes a compression ring and a plurality of compression bolts;

[0029] Each sealing assembly is equipped with an annular groove on the outer cylinder, the annular groove is located on 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;

[0030] The compression ring is stacked on the outside of the sealing ring, the inner side of the sealing ring is in contact with the outer wall of the inner cylinder, the side surface of the sealing ring is in contact with the groove wall of the ring groove, and 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.

[0031] 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.

[0032] The above provides a specific sealing assembly structure, in which the compression ring is provided with a thrust toward the sealing ring by tightening the compression bolts connected to the outer cylinder, thereby enabling the sealing ring to obtain the extrusion force. Before the center hole of the outer cylinder is inserted into the inner cylinder, the compression ring and the sealing ring can be connected by bonding to form an integral structure, and then the integral structure is affixed to the outer end surface of the ring groove. When the inner cylinder is inserted into the outer cylinder, the compression bolts are tightened through the air inlet and exhaust holes to push the integral structure toward the inner cylinder and make the sealing ring fit the outer wall of the inner cylinder. In this 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 tapered 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.

[0033] In a specific implementation, the pressure ring is also an arc-shaped plate structure that adapts to the curvature of the outer surface of the inner cylinder. In such an application, since the outer hole section is preferably set as a flat-bottom hole that is convenient for installing the intake and exhaust valves, for the clamping bolts in different directions of the pressure ring, at the same time, in order to avoid the exposure of the clamping bolts affecting the installation of the intake and exhaust valves, the better solution is to install the clamping bolts with the outer end sunk relative to the bottom of the flat-bottom hole. In such an application, a clamping bolt with multiple length parameters should be used.

[0034] The inner cylinder is a cast iron cylinder, the outer cylinder is an aluminum alloy cylinder, and the inner cylinder is expanded and connected to the outer cylinder.

[0035] The above scheme provides a form of inner cylinder, outer cylinder and cylinder assembly method. Specifically, the inner cylinder is made of cast iron with a small thermal expansion coefficient and wear resistance, such as ductile iron, to ensure its sealing ability with the piston ring at high temperature. The outer layer is made of aluminum alloy with high thermal conductivity and low heat load per unit volume. By reducing the heat load of the outer cylinder and enhancing heat transfer, the maximum temperature of the outer cylinder 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, thereby achieving the purpose of reducing uneven thermal deformation on the outer cylinder. The inner cylinder is expanded and connected to the outer cylinder, which is a prestressed installation method of the cylinder to cope with the characteristic that the thermal expansion coefficient of aluminum alloy is significantly greater than that of cast iron. It strengthens the compactness of the fit between the outer cylinder and the inner cylinder during the operation of the compressor, avoids the formation of gaps between the inner and outer cylinders, and ensures the support capacity of the outer cylinder for the inner cylinder.

[0036] The number of the spiral flow channel is 1. In the axial direction of the cylinder, the air inlet and outlet positions of the piston chamber are both located 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.

[0037] The number of the medium introduction hole is 1, and the connection position between the medium introduction hole and the spiral flow channel is located in the middle of the spiral flow channel in the axial direction;

[0038] The number of the medium outlet holes is 2, and each end of the spiral flow channel is provided with a medium outlet hole.

[0039] The above provides a specific spiral flow channel setting form. The setting of the end position of the spiral flow channel and the inlet and outlet positions of the piston chamber in the direction of the cylinder axis is intended to utilize the isothermal wall effect of the spiral flow channel to evenly distribute the heat dissipation conditions of the inlet and outlet positions of the piston chamber, so as to achieve the purpose of controlling the uneven deformation of the inner cylinder under hot state. The inlet and outlet positions are the connection positions of the above-mentioned inlet hole and exhaust hole on the piston chamber respectively. The setting method of the medium introduction hole and the medium outlet hole is intended to achieve: for the spiral flow channel, the fluid introduced from the middle of the spiral flow channel can flow to both sides of the spiral flow channel and flow out from the medium outlet holes at each end of the spiral flow channel respectively. In the spiral flow channel, for the fluid flowing to each side, the flow path from introduction to outlet is short, and the two-way flow is symmetrical relative to the middle of the length direction of the cylinder. Therefore, this scheme 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, but also the required circulation pipeline structure is simple. As those skilled in the art know, a spiral flow channel is a spiral flow channel, and the axis of the center hole of the spiral flow channel is the axis of the spiral flow channel. In specific applications, the axis of the spiral flow channel is set to be collinear with the axis of the inner cylinder.

[0040] The number of the spiral flow channels is greater than one, and the spiral flow channels are arranged in sequence along the axial direction of the cylinder. In the axial direction of the cylinder, the air inlet position and the air outlet position of the piston chamber are both located within the coverage area of ​​the spiral flow channels. The coverage area is the distribution area of ​​the spiral flow channels on the cylinder axis. The spiral flow channels are independent of each other.

[0041] Each spiral flow channel is provided with a medium introduction hole at one end and a medium outlet hole at the other end.

[0042] The above provides a specific spiral flow channel setting form, which is an equivalent scheme in which the number of spiral flow channels is 1. Specifically, different spiral flow channels are located at different axial positions of the cylinder. For different heat dissipation conditions at these axial positions (for example, the heat dissipation condition at the air inlet position is good due to the low air intake temperature and large flow rate, and the cylinder in this area is a cold zone on the cylinder; the heat dissipation condition at the exhaust hole position is poor due to the high exhaust temperature and large flow rate, and the cylinder in this area is a hot zone on the cylinder), by introducing fluids with different temperatures or flows into these spiral flow channels, the purpose of adjusting to reduce the temperature difference of the fluids at different positions in the spiral flow channel and reducing the uneven deformation occurring on the inner cylinder can be achieved.

[0043] The invention also includes a circulation system connected to the spiral flow channel through a circulation pipeline, wherein the circulation system, the circulation pipeline and the spiral flow channel form an annular medium circulation loop, the spiral flow channel is connected in series in the medium circulation loop, and the circulation pipeline is connected to the spiral flow channel through the medium introduction hole and the medium outlet hole;

[0044] The circulation system includes a pump and a cooler connected in series in the medium circulation loop. The pump serves as a power device for the medium to circulate in the medium circulation loop, and the cooler is used to cool the medium in the medium circulation loop.

[0045] The above provides a technical solution for providing a circulating fluid to the spiral flow channel of the cylinder using a circulation system. In specific implementation, considering the heat dissipation of the cylinder and the optimization of the uneven deformation of the inner cylinder by reducing the temperature difference between the fluid inlet and outlet of the spiral flow channel, it is preferred to use the initial temperature of the fluid injected into the spiral flow channel to be the intermediate value of the compressor inlet and exhaust gas temperatures. By setting up and adopting the above circulation system, not only can the fluid be repeatedly reused, but the temperature of the fluid introduced into and out of the spiral flow channel can also be adjusted by adjusting the cooling capacity of the cooler and the flow rate of the pump.

[0046] In a specific implementation, since there is a possibility that the gas in the piston chamber 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 chamber, it will not have a substantial impact on the safe operation of the compressor. However, this will increase the possibility of liquid hammer and cause the operating efficiency of the compressor to decrease. 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 condition of the compressor through the detection results of the microbubble sensor to avoid serious operating failures of the compressor.

[0047] The present solution also relates to a wellhead natural gas compressor, comprising a cylinder for compressing natural gas, wherein the cylinder comprises a cylinder structure and a piston assembly installed in the cylinder structure, wherein the cylinder structure is the cylinder structure provided in any one of the above items;

[0048] The compression working chamber of the piston chamber has an air outlet position located at the bottom side of the piston chamber.

[0049] The compressor is a piston compressor including the cylinder structure, which is a specific application of the cylinder structure. As described above, if the piston cavities on both sides of the piston ring have air inlet holes and air outlet holes, then the piston cavities on both sides of the piston ring should be considered as the compression working chambers. The above scheme of the compression working chamber having an air outlet located at the bottom of the piston chamber is intended to achieve: when liquid is in the compression working chamber, it can be promptly discharged through this outlet with the exhaust gas, thereby avoiding serious liquid hammer failure in the compressor.

[0050] This solution also relates to a method for operating a wellhead natural gas compressor, wherein the compressor is the compressor described above, and the method is as follows:

[0051] During the process of the compressor compressing the wellhead natural gas, the temperature of each position on the outer periphery of the inner cylinder is balanced by introducing a heat carrier medium into the spiral flow channel and allowing the heat carrier medium to flow along the spiral flow channel.

[0052] The working method is a compressor operation method based on the compressor structure. As mentioned above, this scheme aims to use the fluid in the spiral flow channel to form an isothermal wall on the outer periphery of the inner cylinder. The isothermal wall reduces the uneven deformation of the inner cylinder during the operation of the compressor by uniformizing the heat dissipation conditions and temperature at various positions of the inner cylinder, thereby achieving the purpose of reducing piston ring leakage and optimizing the compressor volume, and achieving the purpose of reducing deformation of different positions of the inner wall of the cylinder and optimizing the vibration during the operation of the compressor.

[0053] The present invention has the following beneficial effects:

[0054] This solution reduces the uneven deformation of the inner cylinder during the operation of the compressor by uniformizing the heat dissipation conditions and temperature at various positions of the inner cylinder, thereby reducing piston ring leakage and optimizing the compressor volume. It also reduces the deformation of different positions of the cylinder inner wall and optimizes 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.

[0055] At the same time, this solution also has the characteristics of effectively ensuring the performance of the cylinder body and facilitating processing. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 This is a cross-sectional view of a specific embodiment of the wellhead natural gas compressor cylinder structure described in this solution;

[0057] Figure 2 for Figure 1 A partial enlarged view of part A;

[0058] Figure 3 for Figure 1 A partial enlarged view of part B;

[0059] Figure 4 This is a cross-sectional view of a laminated structure formed by a pressure ring and a sealing ring in a specific embodiment of the wellhead natural gas compressor cylinder structure described in this solution;

[0060] Figure 5 This is a side view of a stacked structure formed by a pressure ring and a sealing ring in a specific embodiment of the wellhead natural gas compressor cylinder structure described in this solution;

[0061] Figure 6 for Figure 4 a cross-sectional view of the provided stacked structure;

[0062] Figure 7This is a front view of a specific embodiment of the wellhead natural gas compressor cylinder structure described in this solution;

[0063] Figure 8 This is a side view of a specific embodiment of the wellhead natural gas compressor cylinder structure described in this solution. The state shown in this side view is the installation state of the cylinder structure on the compressor, so that the compression working chamber has an exhaust position located at the bottom side of the piston chamber.

[0064] The reference numerals in the accompanying drawings are: 1. outer cylinder, 2. spiral flow channel, 3. end plate, 4. inner cylinder, 5. exhaust hole, 6. air inlet hole, 7. piston chamber, 8. sealing assembly, 9. step surface, 10. piston rod hole, 11. disc spring assembly, 12. circulation pipeline, 13. tightening bolt, 14. pressure ring, 15. sealing ring, 16. tapered section, 17. ring groove. DETAILED DESCRIPTION

[0065] The present invention will be further described in detail below with reference to the embodiments, but the present invention is not limited to the following embodiments:

[0066] Example 1:

[0067] like Figures 1 to 8 As shown, the cylinder structure of the wellhead natural gas compressor includes a cylinder barrel, which includes an outer cylinder barrel 1 and an inner cylinder barrel 4. The inner cylinder barrel 4 is embedded in the center hole of the outer cylinder barrel 1, and the center hole of the inner cylinder barrel 4 forms a piston chamber 7 of the cylinder barrel;

[0068] Both the inner wall of the outer cylinder 1 and the outer wall of the inner cylinder 4 are provided with a spiral groove with a semi-annular cross-section. The spiral grooves of the two form a spiral flow channel 2 extending along the axis of the cylinder and with a circular cross-section. The spiral flow channel 2 is provided with a medium inlet hole and a medium outlet hole located 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 outlet the medium from the spiral flow channel 2.

[0069] In this embodiment, the outer cylinder 1 is the outer layer of the cylinder, and the inner cylinder 4 is the inner layer of the cylinder. The outer cylinder 1 and the inner cylinder are both independent parts. After the spiral grooves are processed on each of them, the inner cylinder 4 is nested inside the outer cylinder 1 to assemble a double-layer cylinder structure. In this way, the spiral grooves on the cylinder form a spiral flow channel 2. When the cylinder body is used 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, the outer cylinder 1 can not only provide support for the inner cylinder 4 to ensure the effective wall thickness of the cylinder, but also When the heat is applied to the inner wall of the inner cylinder 4, 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, so that the temperature of each position on the outer wall of the inner cylinder 4 is closer. In this way, since the source of heat 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 isothermal wall can effectively reduce the difference in temperature between the inside and outside of 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, thereby achieving the purpose of reducing piston ring leakage, optimizing the volume of the compressor, reducing deformation at different positions on the inner wall of the cylinder, and optimizing the vibration during the operation of the compressor.

[0070] At the same time, in terms of the pressure-bearing capacity of the cylinder body, this solution provides a technical solution in which the cylinder is designed to include an outer cylinder 1 and an inner cylinder 4, and spiral grooves are respectively provided on the inner wall of the outer cylinder 1 and the outer wall of the inner cylinder 4, and the spiral flow channel 2 is surrounded by the spiral grooves. Such a technical solution can not only use traditional casting and forging to produce high-quality outer cylinders 1 and inner cylinders 4, but also the spiral grooves are the surface structures of the inner walls of the outer cylinder 1 and the outer walls of the inner cylinder 4, which can be integrally formed on the outer cylinder 1 and the inner cylinder 4 by methods such as casting, or after the cylindrical basic structures of the outer cylinder 1 and the inner cylinder 4 are formed, the spiral grooves can be processed by further machining on the basis of the basic structure. Therefore, this solution also has the characteristics of effectively ensuring the performance of the cylinder body and convenient processing.

[0071] It is easy to understand that the medium introduction hole and the medium outlet hole serve as channels for introducing the medium into the spiral flow channel 2 and channels for withdrawing the medium from the spiral flow channel 2, respectively. As a person skilled in the art, the connection positions of the medium introduction 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 be used to flow spirally along the spiral flow channel 2 to cover different circumferential positions and axial positions of the inner cylinder 4, forming the isothermal wall on the outer wall of the inner cylinder 4. At the same time, as a person skilled in the art, when the medium flows along the spiral flow channel 2, if the temperature of the medium when it is introduced into the cylinder is lower than the exhaust temperature of the cylinder and higher than the intake temperature of the cylinder, the gas entering and exiting the cylinder will cause different positions of the cylinder to have different heat dissipation conditions and temperatures. This causes 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 and circumferential positions of the outer wall of the inner cylinder 4, which is beneficial to isothermal from the perspective of heat dissipation conditions, but it cannot be understood that the temperature at different positions of the outer wall of the inner cylinder 4 can be exactly the same.

[0072] In a specific embodiment, the spiral groove on the inner wall of the outer cylinder 1 starts from the inner wall at one end thereof, and spirals on the inner wall with the axis of the outer cylinder 1 as the center line, and ends on the inner wall of the other end of the outer cylinder 1. The spiral groove on the outer wall of the inner cylinder 4 starts from the outer wall at one end thereof, and spirals on the outer wall with the axis of the inner cylinder 4 as the center line, and ends on the outer wall of the other end. The spiral flow channel 2 extends from one end of the cylinder where the piston rod hole 10 is set to one end of the cylinder where the end plate 3 is set. In the axial direction of the cylinder, the piston chamber 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 chamber 7, and the spiral flow channel 2 can provide comprehensive temperature uniformity and anti-uneven deformation protection for the inner cylinder 4 outside the piston chamber 7.

[0073] Example 2:

[0074] This embodiment is further refined based on the embodiment 1:

[0075] The inner cylinder 4 is a cylindrical structure with a piston rod hole 10 at one end communicating with the piston cavity 7 and a stepped shaft shape. The center hole of the outer cylinder 1 is a stepped hole with a stepped surface 9.

[0076] One end of the inner cylinder 4 having the 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;

[0077] It also 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, the inner end of the end plate 3 is provided with a boss inserted into the inner cylinder 4, 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.

[0078] The above provides a specific cylinder assembly scheme, in which the piston chamber 7 is the working chamber 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 of the outer cylinder 1 and the inner cylinder 4 in the radial direction of the cylinder. One end of the inner cylinder 4 is provided with the piston rod hole 10 and is supported on the step surface 9 of the outer cylinder 1 through the shoulder structure of the end, and the other end of the inner cylinder 4 is supported on the end plate 3 through the disc spring assembly 11, thereby realizing the position constraint of the outer cylinder 1 and the inner cylinder 4 in the axial direction of the cylinder.

[0079] At the same time, the end plate 3 serves as the cylinder head on the cylinder barrel. After being fixed to the outer cylinder barrel 1, it can not only support the inner cylinder barrel 4 through the disc spring assembly 11 to prevent the inner cylinder barrel 4 from moving in the center hole of the outer cylinder barrel 1, but also the boss inserted into the inner cylinder barrel 4 is used to control the clearance size of the piston chamber 7.

[0080] The above scheme adopts a simple structure to realize the position constraint of the inner cylinder 4 in the center hole of the outer cylinder 1. At the same time, for the axial deformation of the inner and outer cylinders 1 generated during operation, not only can the thrust of the disc spring assembly 11 on the inner cylinder 4 be used to maintain the inner cylinder 4 in a stable axial position relative to the outer cylinder 1, but also, by generating compression deformation on the disc spring assembly 11, it can adapt to the thermal deformation of the cylinder and allow thermal stress to be released, so that the cylinder body structure is not only simple in structure, but also has reliable structural stability and the generated thermal stress can be reliably released.

[0081] Example 3:

[0082] This embodiment is further refined based on the embodiment 1:

[0083] The cylinder is provided with an air inlet 6 and an air outlet 5, and each end of the cylinder has an air inlet 6 and an air outlet 5;

[0084] The air inlet 6 and the air exhaust 5 are both: having 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 connected to each other;

[0085] Each air inlet 6 and exhaust hole 5 is equipped with a sealing assembly 8. The sealing assembly 8 of each of the air inlet hole 6 and the exhaust hole 5 is: the sealing assembly 8 is located at the position where the outer hole section and the inner hole section are docked with each other, and the sealing assembly 8 has a sealing ring 15 extending along the circumferential direction of the docking position and located on the outer periphery of the docking position. The sealing ring 15 serves as a sealing isolation structure for each of the gaps with the cylinder, and the gap is the gap between the outer cylinder 1 and the inner cylinder 4.

[0086] The above provides a technical solution with specific intake and exhaust functions. Specifically, the inner hole section at the above docking position is directly connected to the piston chamber 7. When the cylinder is set as a double-layer structure including an outer cylinder 1 and an inner cylinder 4, the intake hole 6 and the exhaust hole 5 on the cylinder are formed by the outer hole section located on the outer cylinder 1 and the inner hole section located on the inner cylinder 4 docking with each other. As for the gap on the mating surface between the inner and outer cylinders 1, even if the inner cylinder 4 is strongly expanded into the outer cylinder 1 (the outer diameter of the inner cylinder 4 is larger than the inner diameter of the center hole of the outer cylinder 1 at room temperature), under the influence of processing errors, inevitable vibrations and thermal deformation 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 2 from entering the piston chamber 7 through the gap and the inner hole section, However, when the cylinders on both sides of the piston ring are provided with air inlet holes 6 and air outlet holes 5 (the piston chambers 7 on both sides of the piston ring serve as compression working chambers. In any direction of movement of the piston ring, the piston chamber 7 on one side is inlet and the piston chamber 7 on the other side is compressed), there is a significant pressure difference on both sides of the piston ring. In this way, the following phenomena may occur: the piston chamber 7 on the compression side of the piston ring pressurizes the gap through the inner hole section. When the pressure exceeds the sealing capacity of the mating surfaces of the inner and outer cylinder barrels 1, the medium in the spiral flow channel 2 enters the piston chamber 7 on the inlet side of the piston ring through the inner hole section, eventually causing liquid hammer in the compressor. At the same time, the gas in the piston chamber 7 enters the mating surface and flows into the spiral flow channel 2, which also leads to a decrease in the efficiency of the compressor. Based on the above, a technical solution of the sealing assembly 8 is provided.

[0087] Specifically, the sealing assembly 8 is used to provide a sealing ring 15 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 chamber 7 from entering the gap on the mating surface, causing the internal pressure of the gap to increase, and eventually causing the medium located between the outer cylinder 1 and the inner cylinder 4 to enter the intake side of the piston chamber 7, and causing the occurrence of compressor liquid hammer during the compression stage on the intake side, while avoiding fluid channeling or gas leakage on the compression side that leads to a decrease in the working efficiency of the compressor.

[0088] 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 support layer for the inner cylinder 4, it is preferred that the outer wall of the inner cylinder 4 is 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 docked with 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 with 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 with the cylindrical surface of the outer cylinder 1. Since the medium processed by the compressor contains 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.

[0089] Example 4:

[0090] This embodiment is further refined based on embodiment 3:

[0091] The sealing assembly 8 further includes a pressure ring 14 and a plurality of compression bolts 13;

[0092] Each sealing assembly 8 is provided with an annular groove 17 on the outer cylinder 1. The annular groove 17 is located on 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.

[0093] The pressure ring 14 is stacked on the outside of the sealing ring 15, and the inner side of the sealing ring 15 is in contact with the outer wall of the inner cylinder 4. The side surface of the sealing ring 15 is in contact with the groove wall of the ring groove 17. The clamping bolts 13 are arranged at intervals along the circumferential direction of the pressure ring 14. Each clamping bolt 13 is threadedly connected to the outer cylinder 1. The inner end of each clamping bolt 13 acts on the outer surface of the pressure ring 14 and provides the pressure ring 14 with an extrusion force toward the sealing ring 15.

[0094] The outer end of the sealing ring 15 has an annular groove, and the inner end of the pressure ring 14 has a tapered section 16 whose outer shape matches the shape of the groove, and the tapered section 16 is embedded in the groove.

[0095] The above provides a specific structure of a sealing assembly 8. By tightening the clamping bolts 13 connected to the outer cylinder 1, the pressure ring 14 is provided with a thrust toward the sealing ring 15, so that the sealing ring 15 obtains the extrusion force. Before the center hole of the outer cylinder 1 is inserted into the inner cylinder 4, the pressure ring 14 and the sealing ring 15 can be connected by bonding to form an integral structure. The integral structure is then adhered to the outer end surface of the ring groove 17. When the inner cylinder 4 is inserted into the outer cylinder 1, the clamping bolts 13 are tightened through the air inlet 6 and the exhaust hole 5, pushing the integral structure toward the inner cylinder 4 and making the sealing ring 15 fit the outer wall of the inner cylinder 4. In this solution, it is further provided that the outer end of the sealing ring 15 has a groove, and the inner end of the pressure ring 14 has a tapered section 16 adapted to the groove. In this way, in the process of the pressure ring 14 moving toward the sealing ring 15, the pressure ring 14 can not only provide the sealing ring 15 with an extrusion force in the radial direction of the cylinder, but also provide the outer edge of the sealing ring 15 with an extrusion force in the axial direction of the cylinder. In this way, the inner end face of the sealing ring 15 forms a sealing surface with the outer wall of the inner cylinder 4, and the side face of the sealing ring 15 forms a sealing surface with the side face of the ring groove 17, thereby realizing reliable sealing of the docking position.

[0096] In a specific implementation, the pressure ring 14 is also an arc-shaped plate structure that adapts 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 for convenient installation of the intake and exhaust valves, for the clamping bolts 13 in different directions of the pressure ring 14, at the same time, in order to avoid the exposure of the clamping bolts 13 affecting the installation of the intake and exhaust valves, the better solution is to install the clamping bolts 13 with the outer end sunk relative to the bottom of the flat-bottom hole. In such an application, a clamping bolt 13 with multiple length parameters should be used.

[0097] Example 5:

[0098] This embodiment is further refined based on the embodiment 1:

[0099] The inner cylinder 4 is a cast iron cylinder, and the outer cylinder 1 is an aluminum alloy cylinder. The inner cylinder 4 is expanded and connected to the outer cylinder 1.

[0100] The above scheme provides a form of inner cylinder 4, outer cylinder 1 and cylinder assembly method. Specifically, inner cylinder 4 is made of cast iron with a small thermal expansion coefficient and wear resistance, such as ductile iron, to ensure its sealing ability with piston rings at high temperatures. The outer layer is made of aluminum alloy with high thermal conductivity and low heat load per unit volume. By reducing the heat load of outer cylinder 1 and strengthening heat transfer, the maximum temperature of outer cylinder 1 and the temperature difference at different positions are reduced, so that each position on the side of the cylinder has a relatively balanced heat dissipation condition, thereby achieving the purpose of reducing uneven thermal deformation on outer cylinder 1. The inner cylinder 4 is expanded and connected to the outer cylinder 1, which is a prestressed installation method of the cylinder to cope with the characteristic that the thermal expansion coefficient of aluminum alloy is significantly greater than that of cast iron. It strengthens the compactness of the fit between outer cylinder 1 and inner cylinder 4 during the operation of the compressor, avoids the generation of gaps between the inner and outer cylinders 1, and ensures the support capacity of outer cylinder 1 to inner cylinder 4.

[0101] Example 6:

[0102] This embodiment is further refined based on the embodiment 1:

[0103] The number of the spiral flow channel 2 is 1. In the axial direction of the cylinder, the air inlet and outlet positions of the piston chamber 7 are both located within the coverage area of ​​the spiral flow channel 2. The coverage area is the area between the two ends of the spiral flow channel 2 on the cylinder.

[0104] The number of the medium introduction hole is 1, and the connection position between the medium introduction hole and the spiral flow channel 2 is located in the middle of the spiral flow channel 2 in the axial direction;

[0105] 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.

[0106] The above provides a specific setting form of the spiral flow channel 2. The setting of the end position of the spiral flow channel 2 and the inlet and outlet positions of the piston chamber 7 in the direction of the cylinder axis is intended to utilize the isothermal wall effect of the spiral flow channel 2 to uniformly dissipate heat at the inlet and outlet positions of the piston chamber 7, so as to achieve the purpose of controlling the uneven deformation of the inner cylinder 4 in the hot state. The inlet and outlet positions are the connection positions of the above-mentioned inlet hole 6 and exhaust hole 5 on the piston chamber 7 respectively. The arrangement of the medium introduction hole and the medium outlet hole is intended to achieve: for the 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 each end of the spiral flow channel 2. In the spiral flow channel 2, for the fluid flowing to each side, the flow path from introduction to outlet is short, and the two-way flow is symmetrical relative to the middle of the length direction of the cylinder. Therefore, this scheme can not only reduce the temperature difference of the fluid at different positions in the spiral flow channel 2, and reduce the uneven deformation occurring on the inner cylinder 4, but also the circulation pipeline 12 required to be configured has a simple structure.

[0107] like Figure 7 As shown, the arrows in the figure are used to indicate the introduction position and the outlet position of the fluid on the cylinder. In the figure, the arrow in the center of the lower cylinder body indicates the introduction position of the fluid into the spiral flow channel 2, and the arrows at both ends of the upper cylinder body indicate the outlet position of the fluid from the spiral flow channel 2.

[0108] Example 7:

[0109] This embodiment is further refined based on the embodiment 1:

[0110] The number of the spiral flow channels 2 is greater than one, and the spiral flow channels 2 are arranged sequentially along the axial direction of the cylinder. In the axial direction of the cylinder, the air inlet position and the air outlet position of the piston chamber 7 are both located 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 axis. The spiral flow channels 2 are independent of each other.

[0111] Each spiral flow channel 2 is provided with a medium introduction hole at one end and a medium outlet hole at the other end.

[0112] The above provides a specific arrangement of the spiral flow channel 2, which is an equivalent solution to the above embodiment 6 in which the number of spiral flow channels 2 is 1. Specifically, different spiral flow channels 2 are located at different axial positions of the cylinder. For different heat dissipation conditions at these axial positions (for example, the heat dissipation conditions at the position of the air inlet 6 are good due to the low air intake temperature and large flow rate, and the cylinder in this area is a cold zone on the cylinder; the heat dissipation conditions at the position of the exhaust hole 5 are poor due to the high exhaust temperature and large flow rate, and the cylinder in this area is a hot zone on the cylinder), by introducing fluids with different temperatures or flow rates into these spiral flow channels 2, the temperature difference of the fluid at different positions in the spiral flow channel 2 can be adjusted to reduce the uneven deformation occurring on the inner cylinder 4. On the other hand, the spiral flow channel 2 covering the area of ​​the cylinder using two or more spiral flow channels 2 shortens the flow path of the fluid in a single spiral flow channel 2 relative to the technical solution adopted in embodiment 6. 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, this configuration has a better temperature uniformity effect on the inner cylinder 4.

[0113] Example 8:

[0114] This embodiment is further refined based on the embodiment 1:

[0115] The apparatus further includes a circulation system connected to the spiral flow channel 2 via a circulation pipe 12. The circulation system, the circulation pipe 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 pipe 12 is connected to the spiral flow channel 2 via the medium introduction hole and the medium outlet hole.

[0116] The circulation system includes a pump and a cooler connected in series in the medium circulation loop. The pump serves as a power device for the medium to circulate in the medium circulation loop, and the cooler is used to cool the medium in the medium circulation loop.

[0117] The above provides a technical solution for providing a circulating fluid to the spiral flow channel 2 of the cylinder using a circulation system. In specific implementation, considering the heat dissipation of the cylinder and the optimization of the uneven deformation of the inner cylinder 4 by reducing the temperature difference between the inlet and outlet fluids of the spiral flow channel 2, it is preferable to use the initial temperature of the fluid injected into the spiral flow channel 2 to be the intermediate value between the inlet and outlet temperatures of the compressor. By setting up and adopting the above circulation system, not only can the fluid be repeatedly reused, but the temperature of the fluid introduced into and out of the spiral flow channel 2 can also be adjusted by adjusting the cooling capacity of the cooler and the flow rate of the pump.

[0118] In a specific implementation, since there is a possibility that the gas in the piston chamber 7 enters 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. However, this will increase the possibility of liquid hammer and cause the operating efficiency of the compressor to decrease. Based on this, a microbubble sensor for detecting whether there are bubbles in the liquid phase is provided in the circulation pipeline 12 connected to the medium outlet hole, so as to monitor the operating condition of the compressor through the detection results of the microbubble sensor to avoid serious operating failures of the compressor.

[0119] Example 9:

[0120] This embodiment, based on the first embodiment, provides a wellhead natural gas compressor, comprising a cylinder for compressing natural gas, wherein the cylinder comprises a cylinder structure and a piston assembly installed in the cylinder structure, wherein the cylinder structure is the cylinder structure described in the first embodiment;

[0121] The compression working chamber of the piston chamber 7 has a gas outlet position located at the bottom side of the piston chamber 7 .

[0122] The compressor is a piston compressor including the cylinder structure, which is a specific application of the cylinder structure. As described above, if the piston cavities 7 on both sides of the piston ring have an air inlet 6 and an air outlet, then the piston cavities 7 on both sides of the piston ring should be considered as the compression working chambers. The above scheme of the compression working chamber having an air outlet located at the bottom side of the piston cavity 7 is intended to ensure that when liquid is present in the compression working chamber, it can be promptly discharged through this outlet with the exhaust gas, thereby avoiding serious liquid hammer failure in the compressor.

[0123] Example 10:

[0124] This embodiment provides a method for operating a wellhead natural gas compressor based on the embodiment 9. The compressor is the compressor described in the embodiment 9. The method is as follows:

[0125] During the process of the compressor compressing the wellhead natural gas, the temperature of each position on the outer periphery of the inner cylinder 4 is balanced by introducing the heat carrier medium into the spiral flow channel 2 and allowing the heat carrier medium to flow along the spiral flow channel 2 .

[0126] The working method is a compressor operation method based on the compressor structure. As mentioned above, this scheme aims to use the fluid in the spiral flow channel 2 to form an isothermal wall on the outer periphery of the inner cylinder 4. The isothermal wall reduces the uneven deformation of the inner cylinder 4 during the operation of the compressor by uniformly dissipating the heat dissipation conditions and temperature at various positions of the inner cylinder 4, thereby achieving the purpose of reducing piston ring leakage and optimizing the compressor volume, and achieving the purpose of reducing deformation of different positions of the inner wall of the cylinder and optimizing the vibration during the operation of the compressor.

[0127] The above content is a further detailed description of the present invention in conjunction with specific preferred embodiments, and the specific embodiments of the present invention cannot be considered to be limited to these descriptions. For those skilled in the art to which the present invention belongs, other embodiments derived without departing from the technical solution of the present invention should be included in the scope of protection of the present invention.

Claims

1. Wellhead natural gas compressor cylinder structure, including cylinder barrel, 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, and 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 lead the medium out of the spiral flow channel (2); The cylinder is provided with an air inlet (6) and an air outlet (5), and each end of the cylinder has an air inlet (6) and an air outlet (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 (6) and air outlet (5) is provided with a sealing assembly (8), and each of the air inlet (6) and air outlet (5) sealing assemblies (8) are: 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 along the circumferential direction of the butting position and located at the outer periphery of the butting position, the sealing ring (15) serving as a sealing isolation structure for each of the gaps between the outer cylinder (1) and the inner cylinder (4); 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. In the axial direction of the cylinder, the air inlet position and the air outlet position of the piston chamber (7) are both located 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 axis. The spiral flow channels (2) are independent of each other. Each spiral flow channel (2) is provided with a medium introduction hole at one end and a medium outlet hole at the other end; It also includes a circulation system connected to the spiral flow channel (2) through a circulation pipeline (12), and a microbubble sensor for detecting whether bubbles are contained in the liquid phase is provided in the circulation pipeline (12).

2. The wellhead natural gas compressor cylinder structure according to claim 1, characterized in that: The inner cylinder (4) is a cylindrical structure with a piston rod hole (10) at one end communicating with the piston cavity (7) and a stepped shaft shape. 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) through a disc spring assembly (11).

3. The wellhead natural gas compressor cylinder structure according to claim 1, characterized in that: The sealing assembly (8) further includes a pressure 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) 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 pressure 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 pressure 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 pressure ring (14) and provides the pressure 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 tapered section (16) whose outer shape matches the shape of the groove, and the tapered section (16) is embedded in the groove.

4. The wellhead natural gas compressor cylinder structure according to any one of claims 1 to 3, characterized in that: The inner cylinder (4) is a cast iron cylinder, the outer cylinder (1) is an aluminum alloy cylinder, and the inner cylinder (4) is expansion-connected to the outer cylinder (1).

5. The wellhead natural gas compressor cylinder structure according to any one of claims 1 to 3, characterized in that: 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 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 a power device for the medium to circulate in the medium circulation loop, and the cooler is used to cool the medium in the medium circulation loop.

6. A wellhead natural gas compressor comprising a cylinder for compressing natural gas, wherein the cylinder comprises a cylinder structure and a piston assembly mounted in the cylinder structure, wherein: The cylinder structure is the cylinder structure provided by any one of claims 1 to 5; The compression working chamber of the piston chamber (7) has an air outlet position located at the bottom side of the piston chamber (7).

7. A method for operating a wellhead natural gas compressor, characterized in that: The compressor is the compressor according to claim 6, and the working method is: During the process of the compressor compressing wellhead natural gas, the temperature of each position on the outer periphery of the inner cylinder (4) is balanced by introducing a heat carrier medium into the spiral flow channel (2) and allowing the heat carrier medium to flow along the spiral flow channel (2).

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