Tribological matching between the chemical engine cylinder liner and piston rings is a core element in ensuring the efficient and reliable operation of an engine. Its design requires comprehensive consideration of multiple dimensions, including material selection, surface treatment, lubrication conditions, thermal load management, morphological matching, and dynamic clearance control.
Material selection is fundamental to tribological matching. The chemical engine cylinder liner and piston rings must possess complementary mechanical properties. For example, when the chemical engine cylinder liner uses high-silicon aluminum alloy or alloy cast iron, the piston rings are often made of chromium- or molybdenum-containing alloy cast iron or steel. This combination achieves uniform wear distribution through hardness gradient differences, avoiding premature failure caused by excessive wear of a single material. Material surface properties are equally crucial. For instance, the bonding between the chromium plating layer and the cast iron substrate must prevent material transfer caused by atomic interface affinity, while the pairing of ceramic-coated piston rings with boron alloy chemical engine cylinder liners reduces the risk of adhesive wear through a low coefficient of friction.
Surface treatment technology directly affects the wear resistance and anti-galling ability of the friction pair. Laser hardening, porous chrome plating, or nitriding are commonly used treatments for chemical engine cylinder liners to create a high-hardness surface layer, enhancing resistance to abrasive wear. Piston rings, on the other hand, benefit from chrome plating, molybdenum spraying, or physical vapor deposition (PVD) coatings (such as CrN and DLC) to improve surface hardness and heat resistance. For example, molybdenum spraying, due to its high melting point and low coefficient of friction, effectively prevents cylinder scoring, while DLC coatings maintain a low-friction state even at high temperatures, significantly extending the life of the mating components. Surface texture design is also crucial; laser etching of micropits or grooves can create an oil film retention zone on the cylinder liner surface, reducing dry friction.
Lubrication condition management is a core challenge in tribological matching. During engine operation, the lubrication state of the chemical engine cylinder liner and piston rings dynamically changes with speed, load, and temperature, encompassing fluid lubrication, boundary lubrication, and mixed lubrication. At the midpoint of the stroke, high speeds facilitate the formation of a hydrodynamic oil film, achieving fluid lubrication; however, near top dead center, low speeds and high temperatures cause a sharp reduction in oil film thickness, making boundary lubrication dominant. At this point, extreme pressure additives (such as ZDDP) in the lubricating oil form a protective film through chemical reaction, preventing direct metal-to-metal contact. However, the interaction between chrome-plated cylinder liners and extreme pressure additives is weak, requiring a physical adsorption film to maintain lubrication, while alloy cast iron cylinder liners can form a chemical adsorption film with the additives, enhancing anti-wear performance.
Thermal load management is crucial for tribological matching. High combustion chamber temperatures cause differences in thermal expansion between the piston rings and cylinder liners. Improper clearance design can lead to cylinder seizure or scoring accidents. For example, insufficient piston ring gap can cause breakage due to hindered thermal expansion, while localized overheating of the cylinder liner can trigger material phase transformation, reducing surface hardness. Therefore, clearance design needs to be optimized using a thermo-mechanical coupling model to ensure a stable oil film is maintained at high temperatures. Furthermore, cooling water temperature control also affects the wear rate; appropriately increasing the outlet temperature can keep the cylinder liner surface temperature above the dew point, reducing sulfuric acid corrosion and thus reducing corrosive wear.
Topology matching and dynamic clearance control are key details in tribological optimization. The cylindricity and roundness errors of the inner wall of the chemical engine cylinder liner must be strictly controlled to avoid uneven wear during piston ring movement. The piston ring's barrel surface design or waveform closed-loop structure can adapt to cylinder liner deformation, achieving uniform contact and reducing localized stress concentration. Dynamic clearance control relies on the intelligent adjustment of the lubrication system. For example, a closed-loop lubrication system uses pressure array technology to monitor 192 lubrication points in real time, dynamically adjusting the injection quantity to automatically optimize the oil film thickness according to load changes, reducing friction loss.
Wear mechanisms and material failure analysis provide theoretical support for tribological matching. Wear forms in chemical engine cylinder liners include abrasive wear, adhesive wear, and corrosive wear. Their location and severity are closely related to piston ring type, lubrication conditions, and fuel quality. For example, the first compression ring, being close to the combustion chamber, is susceptible to high-temperature combustion gas erosion and carbon deposits, leading to accelerated end-face wear; while the oil ring, due to its oil-scraping function, needs to withstand higher mechanical loads, and its failure is often due to hard particles scratching the cylinder liner surface. Through bench tests and simulation analysis, the wear patterns of different mating pairs can be revealed, providing data support for material selection and surface treatment.
