Investigation of the Influence of Lubricating Oil Viscosity on the Wear-Reducing Characteristics of Cylinder Liner Surface Texture  
[PERSON]  
1 School of Energy and Power Engineering, Shandong University, Jinan 250100, China; [EMAIL_ADDRESS] (H.Z.). [EMAIL_ADDRESS] (Y.M.). [EMAIL_ADDRESS] (W.S.) Junzhen Gong  
2 State Key Laboratory of Engine and Powerfran  
various operating conditions [5; 6; 7; 8]. For conventional cylinder liners, high-viscosity lubricants provide better lubrication under high-load conditions, while low-viscosity lubricants perform better under low-load and high-speed conditions [9]. The lubrication performance of oils is influenced by various factors, including their chemical composition and operating temperature, both of which significantly impact the friction reduction effect of the tribological pair [10; 11]. Research by [PERSON] et al. [12] showed that by adjusting the type and concentration of additives in lubricating oil, the lubrication performance of the cylinder liner-piston ring pair could be further optimized. [PERSON] et al. [13] demonstrated that lubricants containing nanoparticles exhibited superior friction reduction in textured cylinder liner-piston ring pairs. [PERSON] et al. [14] found that using hybrid lubricants [15; 16; 17; 18] (hybrid lubricants are conventional lubricants to which nano additives have been added to improve tribological properties. Nano additives include metal nanoparticles such as silver, copper, nickel, molybdenum, and tungsten nanoparticles, metal oxides such as bimetallic oxides like CuO, ZnO, Fe\({}_{3}\)O\({}_{4}\), and TiO\({}_{2}\), carbon nanomaterials such as fullerenes, carbon nanotubes, graphene, etc., and other nanomaterials such as metal sulfides, rare-earth compounds) could significantly reduce the frictional losses of the tribological pair across a wide range of operating conditions. Building on the previous research on lubricants, [PERSON] et al. [15] introduced an intelligent lubrication system capable of adjusting lubricant flow and viscosity in real time to achieve optimal lubrication under various operating conditions. Additionally, [PERSON] et al. [16] utilized a new lubricant formulation and optimized surface texture design, significantly enhancing the performance of the cylinder liner-piston ring pair across diverse operating conditions. To reduce experimental costs, researchers have employed numerical simulation methods to analyze the impact of different surface texture parameters on the lubrication performance of the tribological pair, further revealing the coupling effect between surface texture and lubricant viscosity [17; 18; 19]. [PERSON] et al. [20] applied a Computational Fluid Dynamics (CFD) simulation method to more accurately predict the matching effect between lubricating oil and surface texture under various operating conditions. Subsequent scholars combined experimental and simulation methods to systematically study the effects of different surface textures and lubricating oil combinations on the cylinder liner-piston ring tribological pair [21; 22]. The results of several research studies indicate a strong correlation between texture parameters and lubricant viscosity on one side, and the frictional performance on the other side, thereby providing guidelines for the improvement of the flowability and lubrication performance of lubrication oils [23; 24]. In recent years, research on the lubrication of piston-cylinder liners has primarily focused on experimental studies. To better facilitate engineering applications, this paper combines the actual operating conditions of large-bore engines and conducts simulation calculations to analyze the effects of lubricant parameters on frictional losses of the cylinder liner-piston ring pair under different operating conditions. This analysis provides a basis for the optimal selection of lubricants.