A biogas compressor system and control method

Abstract

This invention discloses a biogas compressor system and control method, relating to the field of gas compressor technology. The control method is applied to the biogas compressor system, which includes a biogas compressor, a cylinder, and a piston assembly disposed within the cylinder. The cylinder assembly also includes a cylinder liner installed within the cylinder, the inner wall of which is coated with a ceramic coating. The piston assembly includes a piston base and piston rings fixed to the outer periphery of the piston base. The piston rings are made of a self-lubricating polymer material and slide in contact with the ceramic coating. The system also includes an annular groove on the outer circumferential surface of the piston rings, located at the end of the piston rings, serving as a accommodating groove for hard ceramic particles detached from the ceramic coating. This solution addresses the adaptability of the biogas compressor to process media while effectively reducing the compressor's failure rate and facilitating fault recovery.

Description

Technical Field

[0001] This invention relates to the field of gas compressor technology, and in particular to a biogas compressor system and control method. Background Technology

[0002] Biogas, as a renewable energy source, relies heavily on compression for purification, grid connection, vehicle fuel, and high-pressure storage. In biogas compression equipment selection, screw compressors dominate in low-to-medium pressure (≤2.5MPa), continuous operation, and scenarios with significant airflow fluctuations. However, in specific application scenarios, reciprocating compressors still possess irreplaceable technological advantages. High-pressure compression capacity: When biogas needs to be compressed to a pressure of 6.0 MPa or higher for use in CNG (compressed natural gas) refueling, high-pressure storage tanks, or long-distance pipeline transportation, screw compressors are difficult to meet the process requirements, while reciprocating compressors can better meet the process needs.

[0003] Investment threshold and adaptability: For small and medium-sized biogas projects, especially those with unstable gas volume, intermittent operation or limited investment budget, reciprocating compressors have advantages over screw compressors, such as lower initial purchase cost, stronger site adaptability and relatively less stringent requirements for front-end pretreatment.

[0004] In the field of biogas compression, reciprocating compressors complement screw compressors. However, in practical design, due to limitations imposed by the composition of biogas, the reliability of reciprocating compressors during biogas compression remains a key focus in this field. Specifically: Biogas is mainly composed of methane and carbon dioxide, and also contains trace amounts of hydrogen sulfide, water vapor, and solid impurities (such as fibers and sand). These components place stringent requirements on the structural design of reciprocating compressors. Corrosion protection: Hydrogen sulfide and carbon dioxide dissolve in condensate to form an acidic solution that severely corrodes common metal materials. Compared to traditional piston compressors, the cylinders, pistons, valves, and other key components of compressors used for biogas compression must be protected against corrosion.

[0005] Water pretreatment: To prevent liquid water from entering the compression chamber and causing liquid slugging, pretreatment equipment such as gas-liquid separators are usually installed at the front end of the compressor in engineering. However, even after pretreatment, biogas may still carry trace amounts of liquid water or high-humidity gas, posing a continuous challenge to the durability of the compressor's internal components.

[0006] Oil-free / low-oil lubrication requirements: When the acidic components in biogas mix with lubricating oil, it can easily lead to acidification, emulsification, and viscosity reduction of the lubricating oil, which will accelerate oil failure and increase maintenance costs. In reciprocating biogas compressors, oil-free lubrication is the mainstream application.

[0007] To address the corrosiveness of biogas and adapt to oil-free lubrication conditions, a possible solution is to apply a ceramic coating to the cylinder inner wall. Ceramic coatings offer wear resistance and excellent resistance to acid and alkali corrosion, effectively adapting to corrosive environments. However, the application of ceramic coatings to the compressor cylinder inner wall can lead to problems such as localized cracking and peeling. Specifically: The coefficient of thermal expansion of ceramic materials differs significantly from that of commonly used cylinder matrix materials (such as cast iron). During compressor start-up and shutdown, load changes, or temperature fluctuations caused by the cooling system, periodic thermal stress is generated at the interface between the ceramic material and the cylinder matrix material. When the thermal stress exceeds the bonding strength between the ceramic and the matrix, the coating will peel off at the interface or develop through cracks. Under oilless lubrication conditions, due to the limitations of the ceramic coating forming process, there may be micro-defects (pores, micro-cracks) in the ceramic coating. At the same time, the piston ring is in direct contact with the ceramic coating and rubs against it at high frequency. The cyclic contact force will induce the expansion of micro-defects inside the coating, eventually leading to local peeling of the coating. Trace solid particles (such as sand) carried in biogas or impurities that fall off from the pipeline enter the compression chamber with the airflow. During the high-speed movement of the piston, they cause local impact on the ceramic coating. Because the ceramic coating has poor toughness, it is prone to local brittle fracture under impact. When the ceramic coating peels off in some areas, exposing the cylinder substrate material, corrosive media penetrate along the interface, weakening the adhesion of the ceramic coating in other locations.

[0008] Hard ceramic particles formed by the cracking and detachment of the ceramic coating cause secondary damage to the compressor by rubbing between the piston rings and the cylinder and by impacting the ceramic coating under airflow pulsation.

[0009] In the prior art, such as the technical solution provided by patent application number CN202320359093.1, entitled "A Friction Pair for a Piston-Type Oil-Free Compressor", a technical solution is provided to obtain a ceramic layer by ceramicizing the inner wall of the cylinder and to obtain a polymer coating layer by polytetrafluoroethylene lamination on the outer surface of the piston. This solution is specifically used to solve problems such as the hardness and wear resistance of the inner wall of the cylinder.

[0010] Further optimization of biogas compression technology will undoubtedly have a positive impact on promoting the development of renewable energy. Summary of the Invention

[0011] To address the aforementioned issues regarding further optimization of biogas compression technology, this invention provides a biogas compressor system and control method. This solution not only addresses the adaptability of the biogas compressor to the process medium but also effectively reduces the compressor's failure rate and facilitates fault recovery.

[0012] To address the above problems, the present invention provides a biogas compressor system and control method that solves the problems through the following technical points: A biogas compressor system includes a biogas compressor, the biogas compressor includes a cylinder and a piston assembly disposed in the cylinder, and also includes a cylinder liner installed in the cylinder, the inner wall of the cylinder liner being provided with a ceramic coating; The piston assembly includes a piston base and a piston ring fixed to the outer periphery of the piston base. The piston ring is made of a polymer self-lubricating material and slides in contact with the ceramic coating. It also includes an annular groove disposed on the outer circumferential surface of the piston ring, the annular groove being located at the end of the piston ring, the annular groove serving as a receiving groove for accommodating hard ceramic particles that have detached from the ceramic coating.

[0013] This solution addresses the corrosive nature of the internal working environment of biogas compressors (due to the acidic components H2S and CO2 in biogas) and the requirement for oil-free lubrication (as the acidic components in biogas would cause lubricating oil to fail rapidly). It provides a specific structural design for a biogas compressor, specifically: The ceramic coating is used to mate with the piston rings, forming a mating pair during the operation of the compressor. The ceramic coating on the inner wall of the cylinder liner has high hardness, providing excellent wear resistance. At the same time, the ceramic coating has a low coefficient of friction and excellent resistance to acid and alkali corrosion, effectively resisting the chemical corrosion of acidic media in biogas. This allows it to withstand the high-frequency reciprocating friction of the piston rings, maintaining the geometric accuracy of the inner wall of the ceramic coating over a long period, and ensuring the volumetric efficiency of the biogas compressor.

[0014] By applying a ceramic coating to the cylinder liner, the ceramic coating provides corrosion protection for the cylinder liner. Furthermore, the ceramic coating and the metal substrate of the cylinder liner form a composite structure, utilizing the wear-resistant and corrosion-resistant properties of the ceramic coating while retaining the toughness of the cylinder liner. This avoids the risk of brittle fracture associated with integral ceramic structures for the cylinder liner. Moreover, due to the limited toughness of the ceramic coating, if it partially detaches due to long-term service or accidental stress, the cylinder liner, as an independent part, can be replaced with a cylinder liner with a intact ceramic coating as a spare part, thus restoring the performance of the biogas compressor. Compared to directly applying the ceramic coating to the cylinder barrel, this eliminates the need for complete disassembly of the biogas compressor and recoating, allowing for efficient on-site compressor maintenance.

[0015] By using piston rings made of polymer self-lubricating materials, such as polytetrafluoroethylene or polyetheretherketone, the piston rings achieve several advantages. First, they have a lower coefficient of friction, forming an ideal low-wear friction pair with the ceramic coating. Second, they achieve stable lubrication without external oil supply, fundamentally avoiding the problem of rapid lubrication failure caused by acidification and emulsification of the lubricating oil after mixing with acidic components in biogas. Third, compared to metal piston rings, polymer self-lubricating piston rings have better toughness, can adapt to minor deformations of the cylinder liner, and have a certain embedding ability for detached hard ceramic particles, reducing the scratch damage that ceramic particles may cause to the ceramic coating.

[0016] The ring grooves described above are designed to address the following: During long-term service, the ceramic coating may partially peel off under the influence of thermal stress, thermal fatigue, contact fatigue, or impact loads, forming hard ceramic particles (typically 10μm to 100μm in diameter) in the compression chamber. The fate of these particles in the compression chamber determines their impact on the compressor's lifespan. This solution uses the ring grooves to contain the hard ceramic particles, thus harmlessly isolating the particles that remain in the compression chamber and enter the friction pair between the ceramic coating and the piston rings.

[0017] Specifically, the destination includes: For ceramic particles of any size resulting from localized detachment of the ceramic coating, if they are carried out of the compression chamber by the airflow during the compressor's exhaust stroke, such ceramic particles do not pose a threat to the ceramic coating. For ceramic particles with larger diameters (particle size larger than the fit gap between the piston ring and the ceramic coating) resulting from localized detachment of the ceramic coating, they cannot enter the friction interface between the piston ring and the ceramic coating. They are either pushed to the end of the compression chamber by the piston assembly, or carried by the airflow and discharged from the compression chamber with the high-pressure gas during the exhaust stroke. Such ceramic particles generally do not pose a continuous threat to the ceramic coating. For ceramic particles with slightly smaller diameters resulting from localized detachment of the ceramic coating, these particles include those smaller than the clearance between the piston ring and the ceramic coating, and those larger than the clearance. Particles smaller than the clearance easily enter the friction interface between the piston ring and the ceramic coating from the piston ring end. Once inside the interface, these particles are subjected to the combined action of piston ring movement and ceramic coating friction, migrating towards the center of the piston ring and causing wear on the ceramic coating during piston ring movement (piston rings have a certain degree of radial movement). Particles larger than the clearance may also embed themselves at a specific angle into the gap between the piston ring and the ceramic coating. For example, when the tip of the particle faces the gap, it provides the conditions for embedding. Furthermore, because the piston ring is a soft material, subsequent ceramic particles, under the combined action of piston ring movement and ceramic coating friction, scratch the outer surface of the piston ring and migrate towards the center. These particles can cause more severe damage to the ceramic coating and piston ring.

[0018] This solution involves setting an annular groove at the end of the piston-type compressor. When ceramic particles migrate to the groove, they fall into it due to the loss of piston ring restraint (for example, in a compressor with a horizontal cylinder block arrangement, the ceramic particles subsequently settle to the bottom of the groove due to their own gravity). In this case, the ceramic particles lose the support from the piston rings, thus eliminating the conditions for scratching the ceramic coating. This achieves the purpose of harmlessly containing these ceramic particles using the annular groove and preventing them from damaging the ceramic coating and piston rings. At the same time, during the maintenance of the biogas compressor, cleaning the ceramic particles in the annular groove can restore or continuously maintain the annular groove's harmless containment capacity for ceramic particles.

[0019] In summary, the biogas compressor system provided by this solution, when applied to biogas compression, effectively ensures the corrosion resistance of the biogas compressor in the corrosive compression chamber working environment determined by the biogas medium, and under the condition of using oil-free lubrication in this environment. At the same time, the ring groove can effectively mitigate the impact of ceramic particles generated in the compression chamber on the ceramic coating and piston rings, thereby extending the effective life of the ceramic coating and piston rings and reducing the compressor failure rate. Furthermore, by placing the easily damaged ceramic coating on the cylinder liner, this solution allows for convenient fault recovery through cylinder liner replacement, effectively reducing the downtime and maintenance costs of the biogas compressor, thus ensuring the continuous operation of the biogas compressor and reducing operating costs.

[0020] In one specific implementation, the materials for other components of the biogas compressor that come into contact with biogas are selected as follows: In addition to the aforementioned friction pairs, the cylinder barrel, cylinder head, piston rod, etc., are components that come into contact with biogas but do not participate in sliding friction. These components can be made of corrosion-resistant metal materials (such as stainless steel 304 / 316L, high-nickel cast iron, etc., to control the overall manufacturing cost) to meet the corrosion resistance requirements under biogas medium.

[0021] In one specific implementation, the ceramic coating uses Al2O3-TiO2 composite ceramic, which has high bonding strength with the cylinder liner metal substrate, resistance to acidic media corrosion, and high wear resistance. The polytetrafluoroethylene (PTFE) filler is carbon fiber-filled PTFE, and the polyetheretherketone (PEEK) is carbon fiber-filled PEEK. This allows the piston ring to have self-lubricating, low-friction, and corrosion-resistant properties, while also possessing good toughness to reduce localized detachment under the scratching action of ceramic particles.

[0022] In one specific implementation, the cylinder liner material is high-nickel cast iron. This material selection not only gives the cylinder liner a certain degree of corrosion resistance, but more importantly, the coefficient of thermal expansion of the cylinder liner is close to that of the Al2O3-TiO2 composite ceramic coating (the TiO2 content needs to be reasonably selected to make the coefficient of thermal expansion of the ceramic coating close to that of high-nickel cast iron). This reduces the impact of thermal stress on the ceramic coating during biogas compressor operation due to temperature changes (such as compressor start-up and shutdown, load fluctuations, or lag in the temperature regulation of the cooling system for the cylinder). When the ceramic coating and the ceramic liner are heated and expand, if the difference in their coefficients of thermal expansion is too large, a large shear stress will be generated at the interface between them. After repeated temperature fluctuations, the ceramic coating is prone to peeling off at the interface or forming a through crack on the ceramic coating. When their coefficients of thermal expansion are close, they can deform together, reducing the impact of thermal stress at the interface on the bonding strength of the ceramic coating on the cylinder liner. This effectively suppresses the risk of early cracking or peeling of the ceramic coating due to thermal deformation, ensures the long-term integrity of the composite structure formed by the ceramic coating and the cylinder liner, reduces the failure rate of the biogas compressor, and lowers operating costs.

[0023] In one specific implementation, the annular groove is set on the outer circumferential surface of the piston ring, the center line of the annular groove is collinear with the axis of the piston ring, the axial distance between the annular groove and the end face of the piston ring is 2mm~5mm, the depth of the annular groove is 0.5mm~2.0mm, the width of the annular groove is 1.0mm~1.5mm, and the root of the annular groove adopts a rounded transition with a fillet radius of 0.5mm~1.0mm. The selection of the above parameters is based on the particle size distribution (10μm~100μm) and migration law of ceramic particles: after entering the interface between the ceramic coating and the piston ring, the ceramic particles can reach the ring groove position by migrating axially a few millimeters under the drive of friction, thereby reducing the damage to the ceramic coating during the migration of ceramic particles. Furthermore, this distance selection can effectively constrain the ceramic particles entering the ring groove within it. The piston ring material between the ring groove and the piston ring end acts as an escape-proof retainer for the ceramic particles in the ring groove. During the intake stroke of the piston ring, at the end of the piston ring near the intake side cavity, an escape-proof retainer of a certain thickness can effectively resist deformation, preventing ceramic particles from entering the friction interface from the ring groove. The selection of the above depth and width aims to balance the ceramic particle holding capacity of the ring groove and the influence of the ring groove on the piston ring's own performance. Wide and excessively deep ring grooves can also weaken the anti-escape ring's resistance to deformation. The use of a rounded transition aims to avoid stress concentration at the root of the ring groove, thus ensuring the piston ring's fatigue life. Each end of the piston ring has two ring grooves (2mm~5mm apart). The width and depth of the inner ring groove are smaller than the corresponding dimensions of the outer ring groove. This is to achieve the following: the size design reduces the impact of the ring grooves on piston ring performance; when the outer ring groove reaches its maximum ceramic particle capacity, the inner ring groove provides redundant protection against further migration of ceramic particles towards the center of the piston ring; when cleaning ceramic particles from the ring grooves, observe whether there are ceramic particles in the inner ring groove. If so, the time difference between maintenance should be shortened, or the ceramic coating on the in-service cylinder liner should be checked to ensure it meets the requirements for continued use.

[0024] A further technical solution for the biogas compressor system is as follows: The cylinder liner is constrained in the cylinder by a cylinder head bolted to the cylinder barrel. A spring assembly is provided between the inner end of the cylinder head and the outer end of the cylinder liner to provide axial support force for the cylinder liner. The cylinder head is provided with a boss that extends into the cylinder liner and provides radial constraint for the cylinder liner. The inner end of the cylinder liner is supported on the bottom of the cylinder liner bore. An axial sealing ring is provided between the boss and the cylinder liner to achieve axial sealing of the gap between the boss and the cylinder liner; A radial sealing ring is provided between the inner end of the cylinder liner and the bottom of the cylinder liner bore to achieve radial sealing of the gap between the inner end of the cylinder liner and the bottom of the cylinder liner bore. The cylinder liner bore serves as the mounting hole for mounting the cylinder liner on the cylinder barrel.

[0025] The above solution provides a specific method for installing a cylinder liner in a cylinder barrel. Specifically, the cylinder liner is inserted into the cylinder liner hole of the cylinder barrel from the end where the cylinder head is located. A radial sealing ring is clamped between the inner end of the cylinder liner and the bottom of the cylinder liner hole. The outer end of the cylinder liner is supported by the cylinder head, and a spring assembly is used as a support between the cylinder liner and the cylinder head. The spring assembly is used to provide elastic support for the outer end of the cylinder liner, aiming to adapt to the stress release and support requirements during the axial expansion and contraction of the cylinder liner through elastic deformation. The boss is used to provide radial support for the inner side of the cylinder liner and serves as the mounting base for the axial sealing ring. The structural design adopted in the above scheme aims to achieve the following: When the biogas compressor adopts a double-acting design (compression chambers are configured on both sides of the piston assembly), the radial sealing ring and axial sealing ring are used to block the channel connecting the compression chambers on both sides of the piston assembly through the gap between the cylinder liner and the boss, the gap between the outer end of the cylinder liner and the cylinder head, the gap between the outer side of the cylinder liner and the mounting hole, and the gap between the inner end of the cylinder liner and the bottom of the cylinder liner hole. This prevents leakage from the channel from affecting the efficiency of the biogas compressor. At the same time, the axial sealing ring and radial sealing ring are used to prevent the medium and particles in the corresponding compression chamber from entering the channel, preventing the formation of acidic droplets in the channel and mixing with the wear debris in the gap to form a viscous substance that affects the thermal expansion of the cylinder liner and axial micro-movement. This also prevents particulate impurities from intruding into the channel and depositing in the channel, affecting the normal function of the spring assembly.

[0026] The cylinder liners on both sides of the piston assembly are equipped with intake ports and exhaust ports. The intake ports are connected to the intake air passage on the cylinder, and the exhaust ports are connected to the exhaust air passage on the cylinder. When the cylinder liner's axis is in the horizontal direction, the exhaust port is located on the bottom side of the cylinder liner; Both ends of the piston ring are equipped with ring grooves.

[0027] The above describes a specific cylinder liner intake and exhaust configuration and piston ring arrangement for a double-acting compressor. Specifically, intake and exhaust ports are provided on both sides of the cylinder liner of the piston assembly, respectively connected to the intake and exhaust air passages on the cylinder barrel. This allows the compression chambers on both sides of the piston assembly to alternately complete the intake, compression, and exhaust processes during reciprocating motion, thereby improving the efficiency of the biogas compressor. When the cylinder liner axis is horizontally arranged, the exhaust port is located on the bottom side of the cylinder liner. Under gravity, detached ceramic particles or liquid precipitated in the compression chamber settle at the bottom of the compression chamber. The ceramic particles accumulate and are carried out by the high-pressure gas during the exhaust stroke, thereby reducing the residence time of ceramic particles in the compression chamber and lowering the probability of them entering the friction interface between the piston ring and the ceramic coating. At the same time, it provides anti-liquid hammer protection for the compression chamber. Both ends of the piston ring are equipped with ring grooves, which are designed to ensure that no matter whether the piston moves to the left or right, ceramic particles entering the friction interface in each compression chamber can be contained by the ring grooves at the corresponding ends of the piston rings. This allows the compression chambers on both sides to be protected against scratches by the ring grooves on the corresponding sides when the cylinder adopts a double-acting structure.

[0028] The bottom of the annular groove and the side of the annular groove are transitioned by a rounded chamfer. On the side of the annular groove near the end of the piston ring, the side of the annular groove transitions to the outer end face of the piston ring through a rounded chamfer. The piston ring end face and side face have a right angle.

[0029] The above provides a more specific implementation of the structure at the corresponding positions on the piston ring. Specifically: the bottom of the ring groove and the side of the ring groove are transitioned with a rounded chamfer. Simultaneously, on the side of the ring groove near the piston ring end, the side of the ring groove and the outer end face of the piston ring are also transitioned with a rounded chamfer. These two rounded chamfers are designed to eliminate stress concentration at the corners, preventing fatigue cracks from forming due to excessive local stress during the piston ring's reciprocating motion under stress changes and temperature fluctuations, thus optimizing piston ring life. The corners between the piston ring end face and the side are right angles, without any chamfers or fillets. The purpose of this structural feature is: if... A chamfer is created between the piston ring end face and the side face, forming an outward-opening bevel at the piston ring end. During piston ring movement, this bevel actively scoops / introduces large ceramic particles, which are originally located on the outer side of the end and have a particle size larger than the mating gap, into / into the mating interface. This increases the probability of ceramic particles entering the friction pair between the ceramic coating and the piston ring. On the other hand, the piston ring end face is made with a right angle, which reduces the amount of ceramic particles that can enter the friction pair and controls the particle size of the ceramic particles that can enter the friction pair by controlling the gap width between the piston ring end and the ceramic coating. This reduces secondary scratches on the ceramic coating caused by ceramic particles and reduces the risk of the ceramic coating being severely scratched by ceramic particles.

[0030] A water-cooling medium flow channel is formed between the cylinder barrel and the cylinder liner; The water-cooling medium flow channel is a spiral annular groove formed by the cylinder barrel and cylinder liner, and surrounding the cylinder liner; The wall thickness δ of the cylinder liner satisfies the following relationship: δ≥(0.04D+2)×(E0 / E), where D is the inner diameter of the cylinder liner, E is the elastic modulus of the material used for the cylinder liner, and E0 is the reference elastic modulus, with a value of 110 GPa.

[0031] The above provides a specific cylinder block cooling method and a wall thickness setting for the associated cylinder liner material, aiming to address the following issues: Since cylinder liners need to be replaced to restore the performance of their ceramic coating, the use of an interference fit between the cylinder liner and cylinder barrel, which has high heat transfer efficiency, presents difficulties in disassembling and assembling the cylinder liner. While a clearance fit facilitates disassembly and assembly, it significantly reduces the heat transfer efficiency of the mating surfaces between the cylinder barrel and cylinder liner outer walls. This is extremely detrimental to the ceramic coating's resistance to peeling, cracking, and detachment caused by thermal shock. In this solution, a water-cooling medium flow channel is formed between the cylinder barrel and cylinder liner, utilizing direct convective heat exchange between the cooling medium and the cylinder liner to achieve efficient cooling of the cylinder liner, thereby reducing the impact of thermal shock on the ceramic coating's detachment. Furthermore, the water-cooling medium flow channel adopts a spiral annular groove structure that surrounds the cylinder liner. This is a solution that can provide relatively uniform cooling capacity to all positions of the cylinder liner in both the axial and circumferential directions. In this solution, the presence of the spiral annular groove means that the cylinder barrel's support for the cylinder liner is no longer a complete cylindrical surface, but a discontinuous annular support surface (the spiral annular groove cannot provide support). As a result, under the action of gas pressure and thermal load, uneven radial deformation is likely to occur at various positions of the cylinder liner. Since the inner wall of the cylinder liner is coated with a ceramic coating, and the connection reliability between the ceramic coating and the cylinder liner metal substrate is extremely sensitive to the deformation of the metal substrate, excessive uneven deformation will directly lead to the peeling of the ceramic coating interface or the generation of through cracks. Against this backdrop, this scheme proposes a quantitative requirement for the cylinder liner wall thickness δ. The value of E0=110 GPa corresponds to the conventional elastic modulus of gray cast iron of 110 GPa. The above relationship reflects the coupling relationship between the cylinder liner wall thickness and the rigidity of the cylinder liner material: if the elastic modulus E of the cylinder liner is larger, the required wall thickness can be reduced accordingly, and vice versa. This ensures that the radial deformation of the inner wall of the cylinder liner is less than the ultimate strain of the ceramic coating under the maximum gas pressure and thermal load. That is, this scheme protects the ceramic coating on the cylinder liner by controlling the cylinder liner wall thickness. At the same time, it achieves the unity of interface heat transfer, cylinder liner maintainability and ceramic coating reliability.

[0032] It should be noted that the value of E0 is only used as a reference benchmark when implementing this solution. When those skilled in the art adjust the coefficients or benchmark values ​​in the formula according to the specific material properties, as long as their concept is the same as this solution (controlling cylinder liner deformation to protect the ceramic coating by limiting the relationship between cylinder liner wall thickness and elastic modulus), it should be considered as an equivalent technical solution of this solution.

[0033] The gap between the cylinder barrel and the cylinder liner is filled with a thermally conductive material, which is a thermally conductive gasket or a thermally conductive potting compound.

[0034] The above provides a technical solution parallel to setting a water-cooled medium flow channel. Specifically, for a double-acting biogas compressor, there is an alternating pressure difference between the compression chambers on both sides of the piston assembly. If the heat-conducting material is a paste-like thermal grease, due to the fluidity of the paste-like thermal grease, even if sealing rings are configured at both ends of the gap to achieve static sealing, when the static sealing rings age and fail, there is still a possibility that the heat-conducting material will be displaced by the airflow under the pressure difference between the two compression chambers and lost, ultimately leading to a sharp increase in the thermal resistance of the gap. At the same time, when the airflow comes into contact with the thermal grease, acidic components such as hydrogen sulfide in the biogas can easily cause the thermal grease to deteriorate, resulting in the loss of the thermal conductivity of the heat-conducting material. In this solution, neither the thermally conductive pad (solid flexible pad) nor the thermally conductive potting compound (which forms a solid elastomer after curing) has fluidity and will not be displaced by gas under pressure difference. Furthermore, the cured thermally conductive material has good corrosion resistance and can resist the erosion of acidic media in biogas. It can maintain a stable gap-filling state for a long time to ensure thermal conductivity. In summary, this solution solves the problem of heat conduction between the cylinder liner and the cylinder barrel, while also solving the problems of thermal medium displacement and chemical failure. It provides a reliable alternative for applications where water cooling structures are inconvenient or where cost is a concern (eliminating the need for a water cooling system).

[0035] It also includes a pretreatment system located upstream of the biogas compressor inlet, the pretreatment system comprising a first gas-water separator, a dry desulfurization tower, a refrigerated dryer, a second gas-water separator, a primary filter, and a secondary filter arranged sequentially along the biogas flow direction; The first gas-water separator is used to separate liquid water from the biogas stream; The dry desulfurization tower is filled with desulfurizing agent packing material and is used to remove hydrogen sulfide from biogas. The refrigerated dryer is used to reduce the temperature of the biogas flow, causing the water vapor in the biogas flow to condense and precipitate. The second gas-water separator is used to separate the liquid water condensed and precipitated in the biogas gas stream; The filtration accuracy of the primary filter is lower than that of the secondary filter. Both the primary and secondary filters are used to intercept solid particles in the airflow.

[0036] The above provides a biogas compressor system solution including a pretreatment system. In specific applications, the outlet of the secondary filter is connected to the inlet of the biogas compressor. In this solution, a first gas-water separator, a dry desulfurization tower, a refrigerated dryer, a second gas-water separator, a primary filter, and a secondary filter are sequentially arranged along the airflow direction. The first gas-water separator removes free liquid water from the biogas, preventing the desulfurizing agent in the dry desulfurization tower from becoming damp and ineffective. The dry desulfurization tower is filled with desulfurizing agent packing material (containing desulfurizing agent), and is located upstream of the refrigerated dryer. This allows for efficient removal of hydrogen sulfide from the biogas at room temperature, preventing the formation of acidic corrosive media in the subsequent condensate and purifying the product gas. The refrigerated dryer lowers the biogas temperature, such as reducing the biogas dew point temperature to below 4°C, allowing water vapor to condense and precipitate. The system features deep dehydration, and because the refrigerated dryer is positioned after the dry desulfurization tower, it avoids the generation of acidic condensate containing hydrogen sulfide during the refrigeration process. This also prevents the desulfurizing agent from reaching low temperatures due to airflow, which could ultimately affect the desulfurization effect. Furthermore, it provides corrosion protection for the refrigerated dryer and pipelines (since 100% desulfurization is impossible, corrosion protection design for pipelines is still necessary in practical applications). The second gas-water separator separates the liquid water precipitated after refrigeration, further reducing the water content of the biogas. The primary filter has a lower filtration precision than the secondary filter (i.e., the primary filter is coarse filtration, and the secondary filter is fine filtration). The primary filter intercepts desulfurizing agent powder and large particulate impurities that may fall off the desulfurization tower, while the secondary filter further intercepts small solid particles and aerosols that remain in the cold airflow. The above scheme adopts the following process sequence: first, remove free water; then, desulfurize; then, deeply dehydrate; and finally, perform staged filtration. In this sequence, the desulfurization process is placed before the cold drying process, which ensures the ambient temperature conditions required for efficient desulfurization reaction and avoids the generation of acidic condensate. The second gas-water separator is placed before the primary and secondary filters, so that water vapor is separated before reaching the primary and secondary filters, preventing liquid water from clogging or corroding the filter elements. The primary and secondary filters work together, with the primary filter bearing the main filtration load to extend the life of the secondary filter. The secondary filter is used to ensure the cleanliness of the gas entering the biogas compressor. The use of this pretreatment system can achieve efficient removal of water, hydrogen sulfide, particulate impurities, etc. in biogas before the biogas is compressed, thereby reducing the impact of media composition on the working stability of the biogas compressor and optimizing the quality of the product gas.

[0037] The number of dry desulfurization towers is greater than 1, and the dry desulfurization towers are connected in parallel. Each dry desulfurization tower can be independently connected in series in the gas path of the biogas flow. The second gas-water separator is a packing-type gas-water separator. The number of second gas-water separators is greater than 1. The second gas-water separators are connected in parallel with each other, and each second gas-water separator can be independently connected in series in the gas path of the biogas flow.

[0038] The above solution provides a further technical solution for the pretreatment system. Specifically, the number of dry desulfurization towers is greater than one and they are connected in parallel. Each dry desulfurization tower can be independently connected in series in the gas path. The purpose is to achieve the alternating use of the dry desulfurization towers: for example, when dry desulfurization tower A is performing desulfurization operations, dry desulfurization tower B can perform offline regeneration of the desulfurizing agent (such as air oxidation regeneration or other regeneration methods), thereby ensuring that after the desulfurizing agent is saturated, it can be switched to the standby dry desulfurization tower to continue operation without shutdown, avoiding interruption of biogas compression treatment due to desulfurizing agent regeneration; similarly, the second gas-water separator uses packing. The first gas-water separator (with a wire mesh demister and a water removal packing box arranged sequentially along the airflow direction) has the characteristic of high efficiency in capturing condensate mist formed by freeze drying. However, after long-term operation, it still has saturation, which leads to a decrease in water removal efficiency and may even cause liquid slugging during the operation of the biogas compressor. Therefore, this solution sets the number of second gas-water separators to be greater than 1, and the second gas-water separators are used alternately during use. For example, the second gas-water separator A and the second gas-water separator B are used alternately. When one is connected in series in the gas circuit, the other is disconnected from the gas circuit and regenerated.

[0039] This solution also relates to a biogas compressor control method, which is applied to the biogas compressor system described in any of the above embodiments, and the method specifically includes: During the operation of the biogas compressor, the operating status parameters of the biogas compressor are collected in real time. The operating status parameters include at least one of the following: cylinder vibration signal, biogas compressor exhaust temperature, biogas compressor biogas compression ratio, and motor current. The motor is a drive motor that drives the piston assembly to reciprocate. The collected operating status parameters are compared with a preset threshold, which is used to determine whether the ceramic coating has suffered damage of a preset severity. When the judgment result indicates that the ceramic coating has suffered damage of a preset severity, the biogas compressor is controlled to reduce power or shut down for protection.

[0040] The above provides a control method for real-time monitoring of biogas compressor status and operation control based on operating status parameters. It aims to promptly identify whether the ceramic coating has suffered damage of a preset severity and take protective measures. Specifically, during long-term service, the ceramic coating may peel off locally due to thermal fatigue, contact fatigue, etc. If the detached ceramic particles are not promptly contained by the ring groove and discharged from the compression chamber with the exhaust gas, they will cause further peeling through scratches, leading to accelerated failure of the ceramic coating, increased wear of the piston rings, and ultimately increased gas leakage and decreased compression efficiency during the biogas compression process. In severe cases, it may even cause sudden jamming or runaway exhaust temperature. In this method, indirect diagnosis of the coating condition is achieved by collecting at least one parameter among vibration signals, exhaust temperature, biogas compression ratio, and motor current. Vibration signals can directly detect the high-frequency impact characteristics generated by the reciprocating motion of particles in the friction interface; exhaust temperature can reflect abnormal temperature rise caused by increased friction or leakage; compression ratio (exhaust pressure / intake pressure) can quantify the efficiency decrease caused by increased clearance and axial leakage due to coating peeling; and motor current can capture load fluctuations caused by particle impact or uneven friction. By comparing the above parameters with preset thresholds, it can be determined whether the coating damage has reached a preset severity level. In the further control logic, once the severity level is determined, the compressor is immediately controlled to operate at reduced power or shut down for protection. It is easy to understand that operating at reduced power can slow down the rate of damage propagation while maintaining the continuity of biogas compression, giving operators time to arrange planned maintenance; direct shutdown is suitable for severe fault scenarios, avoiding irreversible damage to cylinder liners, piston rings, or even cylinder barrels due to continued operation, thereby reducing maintenance costs and preventing production safety accidents.

[0041] The design purpose of this control method complements the design purpose of the annular groove in this scheme, jointly protecting the biogas compressor with ceramic-coated cylinder structure from the problem of ceramic coating peeling during actual operation. This not only ensures the long-term reliability of the compressor but also guarantees its operational safety. In addition, this scheme can provide fault monitoring for the physical structure of the biogas compressor, realizing the upgrade from reactive maintenance to predictive maintenance. In specific applications, the collected operating status parameters are compared with preset thresholds through the compressor system's control module.

[0042] A further technical solution to the biogas compressor control method is as follows: The specific steps of comparing the collected operating status parameters with the preset threshold are as follows: When the operating status parameter is a vibration signal, the vibration signal is subjected to spectrum analysis. When an abnormal vibration component with an amplitude exceeding a preset threshold appears in the characteristic frequency band, it is determined that the damage to the ceramic coating has reached a preset severity level. The characteristic frequency band corresponds to the impact characteristic frequency generated by the reciprocating motion of the detached ceramic particles between the piston ring and the cylinder liner. When the operating status parameter is exhaust temperature, the rate of increase of exhaust temperature per unit time is calculated. When the calculated rate of increase exceeds the first preset threshold, the exhaust temperature exceeds the second preset threshold, or the deviation between the theoretical exhaust temperature under the current operating condition of the compressor and the collected exhaust temperature exceeds the third preset threshold, it is determined that the ceramic coating has been damaged to a preset severity. When the operating status parameter is biogas compression ratio, the intake pressure and exhaust pressure are monitored in real time, and the actual compression ratio is calculated based on the monitoring results. At the same time, the theoretical compression ratio under the current operating conditions is calculated based on the biogas compressor operating frequency, intake temperature and gas adiabatic index. When the deviation between the actual compression ratio and the theoretical compression ratio exceeds the first preset threshold, and the rate of decrease of the actual compression ratio per unit time exceeds the second preset threshold, it is determined that the ceramic coating has been damaged to a preset severity level. When the operating status parameter is motor current, the motor current signal is collected, and the motor current signal is subjected to envelope demodulation processing to obtain the envelope spectrum. When a feature component with the same frequency as the reciprocating motion frequency of the piston assembly appears in the envelope spectrum, and the amplitude of the feature component exceeds a preset threshold, it is determined that the ceramic coating has been damaged to a preset severity. When the operating status parameters include at least two of the following parameters: vibration signal, exhaust temperature, biogas compression ratio, and motor current, a multi-parameter collaborative judgment method is adopted, specifically as follows: Preliminary judgment results on whether the ceramic coating has suffered damage of a preset severity level are obtained according to the judgment methods corresponding to each operating status parameter. When the preliminary judgment results of at least two operating status parameters simultaneously indicate that the ceramic coating has suffered damage of a preset severity level, it is finally determined that the damage level of the ceramic coating has reached the preset severity level.

[0043] The above solutions provide differentiated judgment strategies for different types of operating state parameters and introduce a multi-parameter collaborative mechanism to improve the accuracy and robustness of ceramic coating damage judgment. Specifically, for vibration signals, spectral analysis is used to lock the characteristic frequency band generated by the reciprocating motion of detached ceramic particles in the friction interface. The appearance of abnormal components in this frequency band directly indicates the existence of ceramic particle impact, which has the advantages of fast response and clear physical meaning. For exhaust temperature, a method is used to judge by simultaneously monitoring the heating rate, exhaust temperature exceeding the limit, and the deviation between the exhaust temperature and the theoretical temperature. The method uses a triple threshold of heating rate, actual exhaust temperature, and deviation between actual exhaust temperature and theoretical exhaust temperature to eliminate false alarms caused by using a single temperature threshold under interference such as intake temperature fluctuations and load changes. For biogas compression ratio, the deviation between the actual compression ratio and the theoretical compression ratio is calculated and combined with... The compression ratio decrease rate can effectively distinguish between efficiency loss caused by ceramic coating leakage and proportional changes in exhaust pressure caused by intake pressure fluctuations. The decrease rate threshold is used to exclude the long-term effects of normal progressive wear of piston rings. For motor current, envelope demodulation processing is used to extract the characteristic component with the same reciprocating frequency as the piston, separating the weak impact modulation signal from the strong power frequency background, and realizing non-invasive detection of ceramic particle impact. When multiple parameters are collected simultaneously, this method adopts multi-parameter collaborative judgment: each operating state parameter independently obtains a preliminary judgment result, and only when at least two operating state parameters simultaneously indicate that the ceramic coating has reached a preset severe damage level is the ceramic coating fault finally confirmed. Multi-parameter collaborative judgment is used to form redundant verification, which greatly reduces the false alarm rate and false alarm rate caused by external interference or weak signals of a single sensor, and provides sensitive and reliable intelligent protection measures for the compressor.

[0044] The present invention has the following beneficial effects: This solution effectively ensures the corrosion resistance of the biogas compressor. At the same time, the ring groove can effectively mitigate the impact of ceramic particles generated in the compression chamber on the ceramic coating and piston rings, thereby extending the effective life of the ceramic coating and piston rings and reducing the compressor failure rate. Furthermore, this solution allows for convenient restoration of the ceramic coating by replacing the cylinder liner, which can effectively reduce the downtime and maintenance costs of the biogas compressor, thus ensuring the continuity of operation of the biogas compressor and reducing operating costs. Attached Figure Description

[0045] Figure 1 This is a cross-sectional view of the cylinder portion in a specific embodiment of the biogas compressor system described in this solution; Figure 2 for Figure 1 A magnified view of part A shown; Figure 3 A side view of the cylinder liner in a specific embodiment of the biogas compressor system described in this solution; Figure 4 A cross-sectional view of the cylinder portion in a specific embodiment of the biogas compressor system provided in Example 5; Figure 5 This is an equipment layout diagram of a specific embodiment of the biogas compressor system described in this solution.

[0046] The reference numerals in the attached figures are as follows: 1. Cylinder barrel; 2. Cylinder liner; 21. Ceramic coating; 22. Shear key; 23. Puller bolt hole; 24. Intake port; 25. Exhaust port; 3. Spring assembly; 4. Cylinder head; 41. Boss; 5. Packing seal assembly; 6. Piston assembly; 61. Piston ring; 62. Piston body; 63. Ring groove; 7. Water cooling medium flow channel. Detailed Implementation

[0047] 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: Example 1:

[0048] like Figures 1 to 5 As shown, it includes a biogas compressor, which includes a cylinder 1 and a piston assembly 6 disposed in the cylinder 1, and also includes a cylinder liner 2 installed in the cylinder 1, the inner wall of which is provided with a ceramic coating 21; The piston assembly 6 includes a piston base 62 and a piston ring 61 fixed on the outer periphery of the piston base 62. The piston ring 61 is a polymer self-lubricating material and the piston ring 61 is in sliding contact with the ceramic coating 21. It also includes an annular groove 63 disposed on the outer circumferential surface of the piston ring 61, the annular groove 63 being located at the end of the piston ring 61, the annular groove 63 serving as a receiving groove for accommodating hard ceramic particles that have detached from the ceramic coating 21.

[0049] This solution addresses the corrosive nature of the internal working environment of biogas compressors (due to the acidic components H2S and CO2 in biogas) and the requirement for oil-free lubrication (as the acidic components in biogas would cause lubricating oil to fail rapidly). It provides a specific structural design for a biogas compressor, specifically: The ceramic coating 21 is used to cooperate with the piston ring 61, forming a mating pair during the operation of the compressor. The ceramic coating 21 on the inner wall of the cylinder liner 2 has high hardness, which provides excellent wear resistance. At the same time, the ceramic coating 21 has a low coefficient of friction and excellent resistance to acid and alkali corrosion, which can effectively resist the chemical corrosion of acidic media in biogas, enabling it to withstand the high-frequency reciprocating friction of the piston ring 61, maintain the geometric accuracy of the inner wall of the ceramic coating 21 for a long time, and ensure the volumetric efficiency of the biogas compressor.

[0050] By setting the ceramic coating 21 on the cylinder liner 2, on the one hand, the ceramic coating 21 provides corrosion protection for the cylinder liner 2; on the other hand, the ceramic coating 21 and the metal substrate of the cylinder liner 2 form a composite structure, which utilizes the wear-resistant and corrosion-resistant properties of the ceramic coating 21 while retaining the toughness of the cylinder liner 2, avoiding the risk of brittle fracture that exists with an integral ceramic structure for the cylinder liner 2. Furthermore, due to the limited toughness of the ceramic coating 21, when the ceramic coating 21 partially falls off due to long-term service or accidental stress, the cylinder liner 2, as an independent part, only needs to be replaced with a cylinder liner 2 with the ceramic coating 21 as a spare part, and the performance of the biogas compressor can be restored. Compared with setting the ceramic coating 21 directly on the cylinder barrel 1, there is no need to disassemble the entire biogas compressor or recoat the coating, and the compressor maintenance work can be completed efficiently on-site.

[0051] By setting the piston ring 61 to a high-molecular self-lubricating material, specifically using polytetrafluoroethylene or polyetheretherketone (PEEK) as fillers, the piston ring 61 achieves several advantages. First, it has a low coefficient of friction, forming an ideal low-wear friction pair with the ceramic coating 21. Second, the piston ring 61 can achieve stable lubrication without external oil supply, fundamentally avoiding the problem of rapid lubrication failure caused by acidification and emulsification of the lubricating oil after mixing with acidic components in biogas. Third, compared to a metal piston ring 61, the high-molecular self-lubricating material piston ring 61 has better toughness, can adapt to minor deformations of the cylinder liner 2, and has a certain embedding ability for detached hard ceramic particles, reducing the degree of scratch damage that ceramic particles may cause to the ceramic coating 21.

[0052] The ring groove 63 described above is designed to address the following: During long-term service, the ceramic coating 21 may partially peel off under the influence of thermal stress, thermal fatigue, contact fatigue, or impact loads, forming hard ceramic particles (typically 10μm to 100μm in diameter) in the compression chamber. The fate of these particles in the compression chamber determines their impact on the compressor's lifespan. This solution uses the ring groove 63 to contain the hard ceramic particles, thereby harmlessly isolating the particles that remain in the compression chamber and enter the friction pair between the ceramic coating 21 and the piston ring 61.

[0053] Specifically, the destination includes: For ceramic particles of any size resulting from the partial detachment of ceramic coating 21, if they are carried by airflow and discharged from the compression chamber with the airflow during the compressor's exhaust stroke, such ceramic particles do not pose a threat to ceramic coating 21. For ceramic particles with larger diameters (larger than the fit gap between piston ring 61 and ceramic coating 21) that are produced by localized detachment of ceramic coating 21, they cannot enter the friction interface between piston ring 61 and ceramic coating 21. They are either pushed to the end of the compression chamber by piston assembly 6, or carried by airflow and discharged from the compression chamber with high-pressure gas during the exhaust stroke. Such ceramic particles generally do not pose a continuous threat to ceramic coating 21. For the ceramic particles with slightly smaller diameters resulting from the localized detachment of the ceramic coating 21, these particles include those smaller than the clearance between the piston ring 61 and the ceramic coating 21, and those larger than the clearance. Particles smaller than the clearance easily enter the friction interface between the piston ring 61 and the ceramic coating 21 from the end of the piston ring 61. Once these particles enter the friction interface, they are subjected to the combined action of the piston ring 61's movement and the frictional force of the ceramic coating 21, and migrate towards the center of the piston ring 61 under this combined action. During the movement of the piston ring 61, these particles cause the ceramic coating to... Wear of layer 21 (piston ring 61 has a certain degree of radial movement), and ceramic particles with a particle size larger than the fit gap between piston ring 61 and ceramic coating 21 may also be embedded in the gap between piston ring 61 and ceramic coating 21 at a specific angle. For example, when the tip of the ceramic particle faces the gap, it provides conditions for the ceramic particle to embed in the gap. At the same time, because piston ring 61 is a soft material, subsequent ceramic particles, under the combined action of piston ring 61 movement and ceramic coating 21 friction, scratch the outer surface of piston ring 61 and migrate to the center of piston ring 61. Such ceramic particles can cause more serious damage to ceramic coating 21 and piston ring 61.

[0054] This solution uses an annular groove 63 at the end of the piston-type compressor. When ceramic particles migrate to the position of the annular groove 63, they fall into the annular groove 63 due to the loss of constraint from the piston ring 61 (for example, in the case of a horizontal cylinder block arrangement of the compressor, the ceramic particles subsequently settle to the bottom of the annular groove 63 by their own gravity). In this case, since the ceramic particles lose the support from the piston ring 61, the conditions for scratching the ceramic coating 21 are eliminated. This achieves the purpose of harmlessly containing these ceramic particles using the annular groove 63 and preventing them from damaging the ceramic coating 21 and the piston ring 61. At the same time, during the maintenance of the biogas compressor, the ceramic particles in the annular groove 63 can be cleaned to restore or maintain the harmless containment capacity of the annular groove 63 for ceramic particles.

[0055] In summary, the biogas compressor system provided by this solution, when applied to biogas compression, effectively ensures the corrosion resistance of the biogas compressor in the corrosive working environment of the compression chamber determined by the biogas medium, and under the condition of using oil-free lubrication in this environment. At the same time, the ring groove 63 can effectively alleviate the impact of ceramic particles generated in the compression chamber on the ceramic coating 21 and piston ring 61, thereby extending the effective life of the ceramic coating 21 and piston ring 61 and reducing the compressor failure rate. In addition, by placing the easily damaged ceramic coating 21 on the cylinder liner 2, this solution allows for convenient fault recovery by replacing the cylinder liner 2, which can effectively reduce the downtime and maintenance cost of the biogas compressor, thereby ensuring the continuous operation of the biogas compressor and reducing operating costs.

[0056] In one specific implementation, the materials for other components of the biogas compressor that come into contact with biogas are selected as follows: In addition to the aforementioned friction pairs, the cylinder 1, cylinder head 4, piston rod, etc., are components that come into contact with biogas but do not participate in sliding friction. They can be made of corrosion-resistant metal materials (such as stainless steel 304 / 316L, high-nickel cast iron, etc., to control the overall manufacturing cost) to meet the corrosion resistance requirements under biogas medium.

[0057] In one specific implementation, the ceramic coating 21 adopts an Al2O3-TiO2 composite ceramic with high bonding strength with the metal substrate of the cylinder liner 2, resistance to acidic media corrosion, and high wear resistance. The polytetrafluoroethylene filling adopts carbon fiber-filled polytetrafluoroethylene, and the polyetheretherketone adopts carbon fiber-filled polyetheretherketone, so that the piston ring 61 has self-lubricating, low friction, and corrosion resistance, while also having good toughness to reduce local detachment under the scratching action of ceramic particles.

[0058] In one specific implementation, the cylinder liner 2 is made of high-nickel cast iron. This material selection not only gives the cylinder liner 2 a certain degree of corrosion resistance, but more importantly, the thermal expansion coefficient of the cylinder liner 2 is close to that of the Al2O3-TiO2 composite ceramic coating 21. This reduces the impact of thermal stress on the ceramic coating 21 during biogas compressor operation due to temperature changes (such as compressor start-up and shutdown, load fluctuations, or lag in the temperature regulation of the cooling system configured for cylinder 1). When both the cylinder liner 2 and the ceramic coating 21 expand due to heat, if the difference in their expansion coefficients is too large... The large shear stress at the interface between the two components can easily lead to the peeling of the ceramic coating 21 at the interface or the formation of through cracks on the ceramic coating 21 after repeated temperature fluctuations. When the thermal expansion coefficients of the two components are close, they can deform together, reducing the influence of thermal stress at the interface on the bonding strength of the ceramic coating 21 on the cylinder liner 2. This effectively suppresses the risk of early cracking or peeling of the ceramic coating 21 due to thermal deformation, ensures the long-term integrity of the composite structure formed by the ceramic coating 21 and the cylinder liner 2, reduces the failure rate of the biogas compressor, and lowers operating costs.

[0059] In one specific implementation, the annular groove 63 is disposed on the outer circumferential surface of the piston ring 61. The center line of the annular groove 63 is collinear with the axis of the piston ring 61. The axial distance between the annular groove 63 and the end face of the piston ring 61 is 2mm~5mm. The depth of the annular groove 63 is 0.5mm~2.0mm. The width of the annular groove 63 is 1.0mm~1.5mm. The root of the annular groove 63 adopts a rounded transition with a fillet radius of 0.5mm~1.0mm. The selection of the above parameters is based on the particle size distribution (10μm~100μm) and migration law of ceramic particles: after entering the mating interface between the ceramic coating 21 and the piston ring 61, the ceramic particles can reach the ring groove 63 position by migrating axially a few millimeters under the drive of friction, thereby reducing the damage to the ceramic coating 21 caused by the migration of ceramic particles. Furthermore, this distance selection can effectively and reliably constrain the ceramic particles entering the ring groove 63 within it. The selection of the depth and width aims to balance the ceramic particle holding capacity of the ring groove 63 and the influence of the ring groove 63 on the performance of the piston ring 61 itself. The use of a rounded transition aims to avoid stress concentration at the root of the ring groove 63, thus ensuring the fatigue life of the piston ring 61. Two annular grooves 63 are provided at each end (the distance between the two annular grooves 63 is 2mm~5mm). The width and depth of the inner annular groove 63 are smaller than the corresponding dimensions of the outer annular groove 63. This is to achieve the following: the size design is used to reduce the impact of the annular grooves 63 on the performance of the piston ring 61; when the outer annular groove 63 reaches the maximum ceramic particle holding capacity, the inner annular groove 63 is used to provide redundant protection against further migration of ceramic particles to the center of the piston ring 61; when cleaning the ceramic particles in the annular grooves 63, observe whether there are ceramic particles in the inner annular groove 63. If there are, the time difference between the two maintenance should be shortened, or the ceramic coating 21 on the in-service cylinder liner 2 should be observed to meet the requirements for continued use.

[0060] Example 2:

[0061] This embodiment is a further refinement of embodiment 1: The cylinder liner 2 is constrained in the cylinder 1 by the cylinder cover 4 bolted to the cylinder barrel 1. A spring assembly 3 is provided between the inner end of the cylinder cover 4 and the outer end of the cylinder liner 2 to provide axial support force for the cylinder liner 2. A boss 41 is provided on the cylinder cover 4 that extends into the cylinder liner 2 and provides radial constraint for the cylinder liner 2. The inner end of the cylinder liner 2 is supported on the bottom of the cylinder liner hole. An axial sealing ring is provided between the boss 41 and the cylinder liner 2 to achieve axial sealing of the gap between the boss 41 and the cylinder liner 2. A radial sealing ring is provided between the inner end of the cylinder liner 2 and the bottom of the cylinder liner hole to achieve radial sealing of the gap between the inner end of the cylinder liner 2 and the bottom of the cylinder liner hole. The cylinder liner hole serves as the mounting hole for mounting the cylinder liner 2 on the cylinder barrel 1.

[0062] The above scheme provides a specific method for installing the cylinder liner 2 in the cylinder barrel 1. Specifically, the cylinder liner 2 is inserted into the cylinder liner hole of the cylinder barrel 1 from the end where the cylinder head 4 is located. A radial sealing ring is clamped between the inner end of the cylinder liner 2 and the bottom of the cylinder liner hole. The outer end of the cylinder liner 2 is supported by the cylinder head 4, and a spring assembly 3 is used as a support between the cylinder liner 2 and the cylinder head 4. The spring assembly 3 is used to provide elastic support for the outer end of the cylinder liner 2, which is designed to adapt to the stress release and support requirements when the cylinder liner 2 is axially extended and retracted through elastic deformation. The boss 41 is used to provide radial support for the inner side of the cylinder liner 2 and serves as the mounting base for the axial sealing ring. The structural design adopted in the above scheme aims to achieve the following: When the biogas compressor adopts a double-acting design (compression chambers are configured on both sides of the piston assembly 6), the radial sealing ring and axial sealing ring are used to block the channel connecting the compression chambers on both sides of the piston assembly 6 through the gap between the cylinder liner 2 and the boss 41, the gap between the outer end of the cylinder liner 2 and the cylinder head 4, the gap between the outer side of the cylinder liner 2 and the mounting hole, and the gap between the inner end of the cylinder liner 2 and the bottom of the cylinder liner hole, so as to avoid leakage from the channel affecting the efficiency of the biogas compressor; at the same time, the axial sealing ring and radial sealing ring are used to prevent the medium and particles in the corresponding compression chamber from entering the channel, so as to prevent the formation of acidic droplets in the channel and the mixing with the wear debris in the gap to form a viscous substance that affects the thermal expansion and axial micro-movement of the cylinder liner 2, and to prevent particulate impurities from entering the channel and depositing in the channel, affecting the normal function of the spring assembly 3.

[0063] Example 3:

[0064] This embodiment is a further refinement of embodiment 1: The piston assembly 6 has an intake port 24 and an exhaust port 25 on both sides of the cylinder liner 2. The intake port 24 is connected to the intake air passage on the cylinder 1, and the exhaust port 25 is connected to the exhaust air passage on the cylinder 1. When the axis of cylinder liner 2 is in the horizontal direction, the exhaust port 25 is located on the bottom side of cylinder liner 2; Both ends of the piston ring 61 are provided with ring grooves 63.

[0065] The above provides a specific configuration of the cylinder liner 2 intake and exhaust form and piston ring 61 arrangement for a double-acting compressor. Specifically, intake holes 24 and exhaust holes 25 are provided on both sides of the cylinder liner 2 of the piston assembly 6, respectively connected to the intake and exhaust air passages on the cylinder barrel 1. This allows the compression chambers on both sides of the piston assembly 6 to alternately complete the intake, compression, and exhaust processes during reciprocating motion, thereby improving the efficiency of the biogas compressor. When the cylinder liner 2 is horizontally arranged, the exhaust hole 25 is located on the bottom side of the cylinder liner 2. Under gravity, detached ceramic particles or liquid precipitated in the compression chamber settle at the bottom of the compression chamber. The ceramic particles accumulate and are carried out by the high-pressure gas during the exhaust stroke, thereby reducing the residence time of ceramic particles in the compression chamber and lowering the probability of them entering the friction interface between the piston ring 61 and the ceramic coating 21. At the same time, it provides anti-liquid hammer protection for the compression chamber. Both ends of the piston ring 61 are equipped with ring grooves 63, which are designed to ensure that no matter whether the piston moves to the left or the right, the ceramic particles entering the friction interface in each compression chamber can be contained by the ring grooves 63 at the corresponding ends of the piston ring 61. This allows the compression chambers on both sides to be protected against scratches by the ring grooves 63 on the corresponding sides when the cylinder adopts a double-acting structure.

[0066] Example 4:

[0067] This embodiment is a further refinement of embodiment 1: The bottom of the annular groove 63 and the side of the annular groove 63 are transitioned by a rounded chamfer. On the side of the annular groove 63 near the end of the piston ring 61, the side of the annular groove 63 transitions to the outer end face of the piston ring 61 through a rounded chamfer. The angle between the end face and the side face of the piston ring 61 is a right angle.

[0068] The above provides a more specific implementation of the structure at the corresponding position on the piston ring 61. Specifically: the bottom of the ring groove 63 and the side of the ring groove 63 are transitioned by a rounded chamfer. Simultaneously, on the side of the ring groove 63 near the end of the piston ring 61, the side of the ring groove 63 and the outer end face of the piston ring 61 are also transitioned by a rounded chamfer. The design of these two rounded chamfers aims to eliminate stress concentration at the corners, preventing fatigue cracks from forming due to excessive local stress during the reciprocating motion of the piston ring 61 under stress changes and temperature fluctuations, and thus optimizing the lifespan of the piston ring 61. Furthermore, the corners between the end face and the side of the piston ring 61 are right angles, without any chamfers or rounded corners. The purpose of this structural feature is to: [The text abruptly ends here, likely due to an incomplete sentence or missing information.] A chamfer is provided between the end face and the side face of the piston ring 61, which forms an outwardly opening at the end of the piston ring 61. During the movement of the piston ring 61, this opening will actively scrape / introduce large ceramic particles with a particle size larger than the mating gap into the mating interface, which were originally located on the outer side of the piston ring 61 end. This increases the probability of ceramic particles entering the friction pair between the ceramic coating 21 and the piston ring 61. The outer side of the piston ring 61 end is made of a right-angle end face, which reduces the amount of ceramic particles that can enter the friction pair and controls the particle size of the ceramic particles that can enter the friction pair by controlling the gap width between the piston ring 61 end and the ceramic coating 21. This reduces secondary scratches on the ceramic coating 21 by ceramic particles and reduces the risk of the ceramic coating 21 being severely scratched by ceramic particles.

[0069] Example 5:

[0070] This embodiment is a further refinement of embodiment 1: A water-cooled medium flow channel 7 is formed between the cylinder barrel 1 and the cylinder liner 2; The water-cooling medium flow channel 7 is a spiral annular groove 63 formed by the cylinder barrel 1 and the cylinder liner 2 and surrounding the cylinder liner 2; The wall thickness δ of cylinder liner 2 satisfies the following relationship: δ≥(0.04D+2)×(E0 / E), where D is the inner diameter of cylinder liner 2, E is the elastic modulus of the material used in cylinder liner 2, and E0 is the reference elastic modulus, with a value of 110 GPa.

[0071] The above provides a specific cylinder block cooling method and a wall thickness setting for the associated cylinder liner 2 material, aiming to address the following problem: Since the cylinder liner 2 needs to be replaced to restore the performance of its ceramic coating 21, the use of an interference fit between the cylinder liner 2 and the cylinder barrel 1, which has high heat transfer efficiency, presents difficulties in disassembling and assembling the cylinder liner 2. While a clearance fit facilitates disassembly and assembly, it significantly reduces the heat transfer efficiency of the mating surfaces between the cylinder barrel 1 and the outer wall of the cylinder liner 2. This is extremely detrimental to the ceramic coating 21's resistance to peeling, cracking, and detachment caused by thermal shock. In this solution, a water-cooling medium flow channel 7 is formed between the cylinder barrel 1 and the cylinder liner 2. The direct convective heat exchange between the cooling medium and the cylinder liner 2 achieves efficient cooling of the cylinder liner 2, thereby reducing the impact of thermal shock on the detachment of the ceramic coating 21. Furthermore, the water-cooling medium flow channel adopts a spiral annular groove 63 structure that surrounds the cylinder liner 2. This is a solution that can provide relatively uniform cooling capacity to various positions of the cylinder liner 2 in both the axial and circumferential directions. In this solution, the presence of the spiral annular groove 63 makes the support of the cylinder liner 2 by the cylinder barrel 1 no longer a complete cylindrical surface, but a discontinuous annular support surface (the spiral annular groove 63 cannot provide support). Thus, under the action of gas pressure and thermal load, uneven radial deformation is prone to occur at various positions of the cylinder liner 2. Since the inner wall of the cylinder liner 2 is provided with a ceramic coating 21, and the reliability of the connection between the ceramic coating 21 and the metal substrate of the cylinder liner 2 is extremely sensitive to the deformation of the metal substrate, excessive uneven deformation will directly lead to the peeling of the ceramic coating 21 interface or the generation of through cracks. Against this backdrop, this scheme proposes a quantitative requirement for the wall thickness δ of cylinder liner 2. The value of E0=110 GPa corresponds to the conventional elastic modulus of gray cast iron of 110 GPa. The above relationship reflects the coupling relationship between the cylinder liner wall thickness and the rigidity of the cylinder liner material: if the elastic modulus E of cylinder liner 2 is larger, the required wall thickness can be reduced accordingly, and vice versa, the wall thickness needs to be increased to ensure that the radial deformation of the inner wall of cylinder liner 2 is less than the ultimate strain of ceramic coating 21 under maximum gas pressure and thermal load. That is, this scheme protects the ceramic coating 21 on it by controlling the wall thickness of cylinder liner 2. At the same time, it achieves the unity of interface heat transfer, cylinder liner 2 maintainability and ceramic coating 21 reliability.

[0072] It should be noted that the value of E0 is only used as a reference benchmark when implementing this solution. When those skilled in the art adjust the coefficients or benchmark values ​​in the formula according to the specific material properties, as long as their concept is the same as this solution (controlling the deformation of cylinder liner 2 by limiting the relationship between cylinder liner wall thickness and elastic modulus to protect ceramic coating 21), they should be considered as equivalent technical solutions to this solution.

[0073] Example 6:

[0074] This embodiment is a further refinement of embodiment 1: The gap between the cylinder barrel 1 and the cylinder liner 2 is filled with a thermally conductive material, which is a thermally conductive gasket or a thermally conductive potting compound.

[0075] The above provides a technical solution parallel to the setting of water-cooled medium flow channel 7. Specifically, for a dual-acting biogas compressor, there is an alternating pressure difference between the compression chambers on both sides of the piston assembly 6. If the heat-conducting material is a paste-like thermal grease, due to the fluidity of the paste-like thermal grease, even if sealing rings are configured at both ends of the gap to achieve static sealing, when the static sealing rings age and fail, there is still a possibility that the heat-conducting material will be displaced by the airflow under the pressure difference between the two compression chambers and lost, ultimately leading to a sharp increase in the thermal resistance of the gap. At the same time, when the airflow comes into contact with the thermal grease, acidic components such as hydrogen sulfide in the biogas can easily cause the thermal grease to deteriorate, resulting in the loss of the thermal conductivity of the heat-conducting material. In this solution, neither the thermally conductive pad (solid flexible pad) nor the thermally conductive potting compound (which forms a solid elastomer after curing) has fluidity and will not be displaced by gas under pressure difference. Furthermore, the cured thermally conductive material has good corrosion resistance and can resist the erosion of acidic media in biogas. It can maintain a stable gap-filling state for a long time to ensure thermal conductivity. In summary, this solution solves the problem of heat conduction between cylinder liner 2 and cylinder barrel 1, while also solving the problems of thermally conductive medium displacement and chemical failure. It provides a reliable alternative for applications where water cooling structures are inconvenient or cost-sensitive (eliminating the need for a water cooling system).

[0076] In one specific implementation, a puller bolt hole 23 is provided on the outer end of the cylinder liner 2 to provide a bolt for connecting the cylinder liner 2 through the puller bolt hole 23. This bolt is used to connect with a hydraulic puller, screw puller, or other puller, so that the cylinder liner 2 to be replaced can be pulled out of the cylinder barrel 1 through the puller tool, facilitating the maintenance of the cylinder liner 2. Furthermore, a shear key 22 extending along the axis of the cylinder liner 2 is provided on the outer side of the cylinder liner 2. The shear key 22 is a strip-shaped ridge on the outer side of the cylinder liner 2, which is used to cooperate with the strip-shaped groove on the wall of the cylinder liner hole. The cylinder liner 2 and the cylinder barrel 1 are connected by a key, thereby achieving anti-rotation constraint of the cylinder liner 2 in the cylinder liner hole.

[0077] Example 7:

[0078] This embodiment is a further refinement of embodiment 1: It also includes a pretreatment system located upstream of the biogas compressor inlet, the pretreatment system comprising a first gas-water separator, a dry desulfurization tower, a refrigerated dryer, a second gas-water separator, a primary filter, and a secondary filter arranged sequentially along the biogas flow direction; The first gas-water separator is used to separate liquid water from the biogas stream; The dry desulfurization tower is filled with desulfurizing agent packing material and is used to remove hydrogen sulfide from biogas. The refrigerated dryer is used to reduce the temperature of the biogas flow, causing the water vapor in the biogas flow to condense and precipitate. The second gas-water separator is used to separate the liquid water condensed and precipitated in the biogas gas stream; The filtration accuracy of the primary filter is lower than that of the secondary filter. Both the primary and secondary filters are used to intercept solid particles in the airflow.

[0079] The above provides a biogas compressor system solution including a pretreatment system. In specific applications, the outlet of the secondary filter is connected to the inlet of the biogas compressor. In this solution, a first gas-water separator, a dry desulfurization tower, a refrigerated dryer, a second gas-water separator, a primary filter, and a secondary filter are sequentially arranged along the airflow direction. The first gas-water separator removes free liquid water from the biogas, preventing the desulfurizing agent in the dry desulfurization tower from becoming damp and ineffective. The dry desulfurization tower is filled with desulfurizing agent packing material (containing desulfurizing agent), and is located upstream of the refrigerated dryer. This allows for efficient removal of hydrogen sulfide from the biogas at room temperature, preventing the formation of acidic corrosive media in the subsequent condensate and purifying the product gas. The refrigerated dryer lowers the biogas temperature, such as reducing the biogas dew point temperature to below 4°C, allowing water vapor to condense and precipitate. The system features deep dehydration, and because the refrigerated dryer is positioned after the dry desulfurization tower, it avoids the generation of acidic condensate containing hydrogen sulfide during the refrigeration process. This also prevents the desulfurizing agent from reaching low temperatures due to airflow, which could ultimately affect the desulfurization effect. Furthermore, it provides corrosion protection for the refrigerated dryer and pipelines (since 100% desulfurization is impossible, corrosion protection design for pipelines is still necessary in practical applications). The second gas-water separator separates the liquid water precipitated after refrigeration, further reducing the water content of the biogas. The primary filter has a lower filtration precision than the secondary filter (i.e., the primary filter is coarse filtration, and the secondary filter is fine filtration). The primary filter intercepts desulfurizing agent powder and large particulate impurities that may fall off the desulfurization tower, while the secondary filter further intercepts small solid particles and aerosols that remain in the cold airflow. The above scheme adopts the following process sequence: first, remove free water; then, desulfurize; then, deeply dehydrate; and finally, perform staged filtration. In this sequence, the desulfurization process is placed before the cold drying process, which ensures the ambient temperature conditions required for efficient desulfurization reaction and avoids the generation of acidic condensate. The second gas-water separator is placed before the primary and secondary filters, so that water vapor is separated before reaching the primary and secondary filters, preventing liquid water from clogging or corroding the filter elements. The primary and secondary filters work together, with the primary filter bearing the main filtration load to extend the life of the secondary filter. The secondary filter is used to ensure the cleanliness of the gas entering the biogas compressor. The use of this pretreatment system can achieve efficient removal of water, hydrogen sulfide, particulate impurities, etc. in biogas before the biogas is compressed, thereby reducing the impact of media composition on the working stability of the biogas compressor and optimizing the quality of the product gas.

[0080] Example 8:

[0081] This embodiment is a further refinement of embodiment 7: The number of dry desulfurization towers is greater than 1, and the dry desulfurization towers are connected in parallel. Each dry desulfurization tower can be independently connected in series in the gas path of the biogas flow. The second gas-water separator is a packing-type gas-water separator. The number of second gas-water separators is greater than 1. The second gas-water separators are connected in parallel with each other, and each second gas-water separator can be independently connected in series in the gas path of the biogas flow.

[0082] The above solution provides a further technical solution for the pretreatment system. Specifically, the number of dry desulfurization towers is greater than one and they are connected in parallel. Each dry desulfurization tower can be independently connected in series in the gas path. The purpose is to achieve the alternating use of the dry desulfurization towers: for example, when dry desulfurization tower A is performing desulfurization operations, dry desulfurization tower B can perform offline regeneration of the desulfurizing agent (such as air oxidation regeneration or other regeneration methods), thereby ensuring that after the desulfurizing agent is saturated, it can be switched to the standby dry desulfurization tower to continue operation without shutdown, avoiding interruption of biogas compression treatment due to desulfurizing agent regeneration; similarly, the second gas-water separator uses packing. The first gas-water separator (with a wire mesh demister and a water removal packing box arranged sequentially along the airflow direction) has the characteristic of high efficiency in capturing condensate mist formed by freeze drying. However, after long-term operation, it still has saturation, which leads to a decrease in water removal efficiency and may even cause liquid slugging during the operation of the biogas compressor. Therefore, this solution sets the number of second gas-water separators to be greater than 1, and the second gas-water separators are used alternately during use. For example, the second gas-water separator A and the second gas-water separator B are used alternately. When one is connected in series in the gas circuit, the other is disconnected from the gas circuit and regenerated.

[0083] Example 9:

[0084] This embodiment, based on Embodiment 1, provides a biogas compressor control method. This method is applied to the biogas compressor system described in Embodiment 1, and the method specifically includes: During the operation of the biogas compressor, the operating status parameters of the biogas compressor are collected in real time. The operating status parameters include at least one of the following: vibration signal of cylinder 1, exhaust temperature of biogas compressor, biogas compression ratio of biogas compressor, and motor current. The motor is a drive motor that drives the reciprocating motion of piston assembly 6. The collected operating status parameters are compared with a preset threshold, which is used to determine whether the ceramic coating 21 has been damaged to a preset degree. When the judgment result indicates that the ceramic coating 21 has suffered damage of a preset severity, the biogas compressor is controlled to reduce power or shut down for protection.

[0085] The above provides a control method for real-time monitoring of the biogas compressor status and operation control based on operating status parameters. The aim is to promptly identify whether the ceramic coating 21 has suffered damage of a preset severity and take protective measures. Specifically, during long-term service, the ceramic coating 21 may experience local peeling due to thermal fatigue, contact fatigue, etc. If the detached ceramic particles are not promptly contained by the ring groove 63 and discharged from the compression chamber with the exhaust gas, they will cause further peeling through scratches, leading to accelerated failure of the ceramic coating 21 and increased wear of the piston ring 61. Ultimately, this results in increased gas leakage and decreased compression efficiency during the biogas compression process, and in severe cases, even sudden jamming or runaway exhaust temperature. In this method, indirect diagnosis of the coating condition is achieved by collecting at least one parameter among vibration signals, exhaust temperature, biogas compression ratio, and motor current. Vibration signals can directly detect the high-frequency impact characteristics generated by the reciprocating motion of particles in the friction interface; exhaust temperature can reflect abnormal temperature rise caused by increased friction or leakage; compression ratio (exhaust pressure / intake pressure) can quantify the efficiency decrease caused by increased clearance and axial leakage due to coating peeling; motor current can capture load fluctuations caused by particle impact or uneven friction. By comparing the above parameters with preset thresholds, it can be determined whether the coating damage has reached a preset severity level. In the further control logic, once the severity level is determined, the compressor is immediately controlled to reduce power or shut down for protection. It is easy to understand that reducing power can slow down the damage propagation rate while maintaining the continuity of biogas compression, giving operators time to arrange planned maintenance; direct shutdown is suitable for severe fault scenarios, avoiding irreversible damage to cylinder liner 2, piston ring 61, or even cylinder barrel 1 due to continued operation, thereby reducing maintenance costs and preventing production safety accidents.

[0086] The design purpose of this control method complements that of the annular groove 63 in this scheme, jointly protecting the biogas compressor with a ceramic coating 21 cylinder structure from the problem of ceramic coating 21 peeling off during actual operation. This not only ensures the long-term reliability of the compressor but also its operational safety. In addition, this scheme can provide fault monitoring for the physical structure of the biogas compressor, realizing the upgrade from reactive maintenance to predictive maintenance. In specific applications, the collected operating status parameters are compared with preset thresholds through the compressor system's control module.

[0087] Example 10: This embodiment is a further refinement of embodiment 9: The specific steps of comparing the collected operating status parameters with the preset threshold are as follows: When the operating status parameter is a vibration signal, the vibration signal is subjected to spectrum analysis. When an abnormal vibration component with an amplitude exceeding a preset threshold appears in the characteristic frequency band, it is determined that the damage degree of the ceramic coating 21 has reached a preset severity level. The characteristic frequency band corresponds to the impact characteristic frequency generated by the reciprocating motion of the detached ceramic particles between the piston ring 61 and the cylinder liner 2. When the operating status parameter is exhaust temperature, the rate of increase of exhaust temperature per unit time is calculated. When the calculated rate of increase exceeds the first preset threshold, the exhaust temperature exceeds the second preset threshold, or the deviation between the theoretical exhaust temperature under the current operating condition of the compressor and the collected exhaust temperature exceeds the third preset threshold, it is determined that the ceramic coating 21 has been damaged to a preset severity. When the operating status parameter is biogas compression ratio, the intake pressure and exhaust pressure are monitored in real time, and the actual compression ratio is calculated based on the monitoring results. At the same time, the theoretical compression ratio under the current operating conditions is calculated based on the biogas compressor operating frequency, intake temperature and gas adiabatic index. When the deviation between the actual compression ratio and the theoretical compression ratio exceeds the first preset threshold, and the rate of decrease of the actual compression ratio per unit time exceeds the second preset threshold, it is determined that the ceramic coating 21 has suffered damage of a preset severity. When the operating status parameter is motor current, the motor current signal is collected, and the motor current signal is subjected to envelope demodulation processing to obtain the envelope spectrum. When a characteristic component with the same frequency as the reciprocating motion frequency of the piston assembly 6 appears in the envelope spectrum, and the amplitude of the characteristic component exceeds a preset threshold, it is determined that the ceramic coating 21 has been damaged to a preset severity. When the operating status parameters include at least two of the following parameters: vibration signal, exhaust temperature, biogas compression ratio, and motor current, a multi-parameter collaborative judgment method is adopted, specifically as follows: Preliminary judgment results on whether the ceramic coating 21 has suffered damage of a preset severity level are obtained according to the judgment methods corresponding to each operating state parameter. When the preliminary judgment results of at least two operating state parameters simultaneously indicate that the ceramic coating 21 has suffered damage of a preset severity level, it is finally determined that the damage level of the ceramic coating 21 has reached the preset severity level.

[0088] The above scheme provides differentiated judgment strategies for different types of operating state parameters and introduces a multi-parameter collaborative mechanism to improve the accuracy and robustness of ceramic coating 21 damage judgment. Specifically, for vibration signals, spectrum analysis is used to lock the characteristic frequency band generated by the reciprocating motion of detached ceramic particles in the friction interface. The appearance of abnormal components in this frequency band directly indicates the existence of ceramic particle impact, which has the advantages of fast response and clear physical meaning. For exhaust temperature, the method of judgment is based on the simultaneous monitoring of heating rate, exhaust temperature exceeding limit, and deviation between exhaust temperature and theoretical temperature. The method uses a triple threshold of heating rate, actual exhaust temperature, and deviation between actual exhaust temperature and theoretical exhaust temperature to eliminate false alarms caused by using a single temperature threshold under interference such as intake temperature fluctuations and load changes. For biogas compression ratio, the deviation between actual compression ratio and theoretical compression ratio is calculated and combined with the compression ratio. The rate of decline can effectively distinguish between the efficiency decrease caused by leakage of ceramic coating 21 and the proportional change in exhaust pressure caused by intake pressure fluctuation. The rate of decline threshold is used to exclude the long-term effects of normal progressive wear of piston ring 61. For motor current, envelope demodulation processing is used to extract the characteristic component with the same reciprocating frequency as the piston, separating the weak impact modulation signal from the strong power frequency background, and realizing non-invasive detection of ceramic particle impact. When multiple parameters are collected at the same time, this method adopts multi-parameter collaborative judgment: each operating state parameter independently obtains a preliminary judgment result. Only when at least two operating state parameters simultaneously indicate that the ceramic coating 21 has reached the preset severe damage is the ceramic coating 21 fault finally confirmed. Multi-parameter collaborative judgment is used to form redundant verification, which greatly reduces the false alarm rate and false alarm rate caused by external interference or weak signal of a single sensor, and provides sensitive and reliable intelligent protection measures for the compressor.

[0089] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific embodiments of the present invention are limited to these descriptions. For those skilled in the art, other embodiments derived without departing from the technical solution of the present invention should be included within the scope of protection of the present invention.

Claims

1. A biogas compressor control method, characterized in that, The method is applied to a biogas compressor system, which includes a biogas compressor, which includes a cylinder (1) and a piston assembly (6) disposed in the cylinder (1), and also includes a cylinder liner (2) installed in the cylinder (1), the inner wall of which is provided with a ceramic coating (21). The piston assembly (6) includes a piston base (62) and a piston ring (61) fixed on the outer periphery of the piston base (62). The piston ring (61) is made of a polymer self-lubricating material and slides in contact with the ceramic coating (21). It also includes an annular groove (63) disposed on the outer circumferential surface of the piston ring (61), the annular groove (63) being located at the end of the piston ring (61), the annular groove (63) serving as a receiving groove for accommodating hard ceramic particles that have detached from the ceramic coating (21); The method is specifically as follows: During the operation of the biogas compressor, the operating status parameters of the biogas compressor are collected in real time. The operating status parameters include at least one of the following: vibration signal of cylinder (1), exhaust temperature of biogas compressor, biogas compression ratio of biogas compressor, and motor current. The motor is a drive motor that drives the reciprocating motion of piston assembly (6). The collected operating status parameters are compared with a preset threshold, which is used to determine whether the ceramic coating (21) has been damaged to a preset degree. When the judgment result is that the ceramic coating (21) has been damaged to a preset severity level, the biogas compressor is controlled to reduce power or shut down for protection.

2. The biogas compressor control method according to claim 1, characterized in that, The cylinder liner (2) is constrained in the cylinder barrel (1) by the cylinder cover (4) bolted to the cylinder barrel (1). A spring assembly (3) is provided between the inner end of the cylinder cover (4) and the outer end of the cylinder liner (2) to provide axial support force for the cylinder liner (2). A boss (41) is provided on the cylinder cover (4) that extends into the cylinder liner (2) and provides radial constraint for the cylinder liner (2). The inner end of the cylinder liner (2) is supported on the bottom of the cylinder liner hole. An axial sealing ring is provided between the boss (41) and the cylinder liner (2) to achieve axial sealing of the gap between the boss (41) and the cylinder liner (2); A radial sealing ring is provided between the inner end of the cylinder liner (2) and the bottom of the cylinder liner hole to achieve radial sealing of the gap between the inner end of the cylinder liner (2) and the bottom of the cylinder liner hole. The cylinder liner hole serves as the mounting hole for mounting the cylinder liner (2) on the cylinder barrel (1).

3. The biogas compressor control method according to claim 1 or 2, characterized in that, The cylinder liners (2) on both sides of the piston assembly (6) are provided with an intake port (24) and an exhaust port (25). The intake port (24) is connected to the intake air passage on the cylinder (1), and the exhaust port (25) is connected to the exhaust air passage on the cylinder (1). When the axis of the cylinder liner (2) is in the horizontal direction, the exhaust port (25) is located on the bottom side of the cylinder liner (2); Both ends of the piston ring (61) are provided with ring grooves (63).

4. The biogas compressor control method according to claim 1, characterized in that, The bottom of the annular groove (63) and the side of the annular groove (63) are transitioned by a rounded chamfer; On the side of the annular groove (63) near the end of the piston ring (61), the side of the annular groove (63) and the outer end face of the piston ring (61) are transitioned by a rounded chamfer. The piston ring (61) has a right angle between its end face and side face.

5. The biogas compressor control method according to claim 1, characterized in that, A water-cooled medium flow channel (7) is formed between the cylinder barrel (1) and the cylinder liner (2); The water-cooling medium flow channel (7) is a spiral annular groove formed by the cylinder barrel (1) and the cylinder liner (2) and surrounding the cylinder liner (2); The wall thickness δ of the cylinder liner (2) satisfies the following relationship: δ≥(0.04D+2)×(E0 / E), where D is the inner diameter of the cylinder liner (2), E is the elastic modulus of the material used in the cylinder liner (2), E0 is the reference elastic modulus, and the value of E0 is 110 GPa.

6. The biogas compressor control method according to claim 1, characterized in that, The gap between the cylinder barrel (1) and the cylinder liner (2) is filled with a thermally conductive material, which is a thermally conductive pad or a thermally conductive potting compound.

7. The biogas compressor control method according to claim 1, characterized in that, It also includes a pretreatment system located upstream of the biogas compressor inlet, the pretreatment system comprising a first gas-water separator, a dry desulfurization tower, a refrigerated dryer, a second gas-water separator, a primary filter, and a secondary filter arranged sequentially along the biogas flow direction; The first gas-water separator is used to separate liquid water from the biogas stream; The dry desulfurization tower is filled with desulfurizing agent packing material and is used to remove hydrogen sulfide from biogas. The refrigerated dryer is used to reduce the temperature of the biogas flow, causing the water vapor in the biogas flow to condense and precipitate. The second gas-water separator is used to separate the liquid water condensed and precipitated in the biogas gas stream; The filtration accuracy of the primary filter is lower than that of the secondary filter. Both the primary and secondary filters are used to intercept solid particles in the airflow.

8. The biogas compressor control method according to claim 7, characterized in that, The number of dry desulfurization towers is greater than 1, and the dry desulfurization towers are connected in parallel. Each dry desulfurization tower can be independently connected in series in the gas path of the biogas flow. The second gas-water separator is a packing-type gas-water separator. The number of second gas-water separators is greater than 1. The second gas-water separators are connected in parallel with each other, and each second gas-water separator can be independently connected in series in the gas path of the biogas flow.

9. The biogas compressor control method according to claim 1, characterized in that, The specific steps of comparing the collected operating status parameters with the preset threshold are as follows: When the operating status parameter is a vibration signal, the vibration signal is subjected to spectrum analysis. When an abnormal vibration component with an amplitude exceeding a preset threshold appears in the characteristic frequency band, it is determined that the damage degree of the ceramic coating (21) has reached a preset severity level. The characteristic frequency band corresponds to the impact characteristic frequency generated by the reciprocating motion of the detached ceramic particles between the piston ring (61) and the cylinder liner (2). When the operating status parameter is exhaust temperature, the rate of increase of exhaust temperature per unit time is calculated. When the calculated rate of increase exceeds the first preset threshold, the exhaust temperature exceeds the second preset threshold, or the deviation between the theoretical exhaust temperature under the current operating condition of the compressor and the collected exhaust temperature exceeds the third preset threshold, it is determined that the ceramic coating (21) has been damaged to a preset severity. When the operating status parameter is biogas compression ratio, the intake pressure and exhaust pressure are monitored in real time, and the actual compression ratio is calculated based on the monitoring results. At the same time, the theoretical compression ratio under the current working condition is calculated based on the biogas compressor operating frequency, intake temperature and gas adiabatic index. When the deviation between the actual compression ratio and the theoretical compression ratio exceeds the first preset threshold, and the rate of decrease of the actual compression ratio per unit time exceeds the second preset threshold, it is determined that the ceramic coating (21) has been damaged to a preset severity. When the operating status parameter is motor current, the motor current signal is collected, and the motor current signal is subjected to envelope demodulation processing to obtain the envelope spectrum. When a characteristic component with the same frequency as the reciprocating motion frequency of the piston assembly (6) appears in the envelope spectrum, and the amplitude of the characteristic component exceeds the preset threshold, it is determined that the ceramic coating (21) has been damaged to a preset severity. When the operating status parameters include at least two of the following parameters: vibration signal, exhaust temperature, biogas compression ratio, and motor current, a multi-parameter collaborative judgment method is adopted, specifically as follows: Preliminary judgment results on whether the ceramic coating (21) has suffered damage of a preset severity level are obtained according to the judgment methods corresponding to each operating state parameter. When the preliminary judgment results of at least two operating state parameters simultaneously indicate that the ceramic coating (21) has suffered damage of a preset severity level, it is finally determined that the damage level of the ceramic coating (21) has reached the preset severity level.

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