The cylinder liner and piston ring form the most crucial friction pair in the diesel engine, contributing 35–40% of its overall friction losses. Recent research indicates that transient heat transfer significantly affects piston ring lubrication. However, the impact of such a transfer on varying surface textures and lubrication traits remains unclear. This paper takes the piston ring–cylinder liner of a certain diesel engine as the research object, which is based on a two-dimensional averaged Reynolds function and Greenwood–Tripp micro convex body contact model; establishes a numerical calculation model of the transient heat fluid lubrication characteristics of a vertical piston ring–cylinder liner assembly by combining the oil film thickness equation, energy equation, lubricating oil viscosity–temperature, and viscosity pressure characteristics; avoids large errors associated with assuming different temperature values for lubricants; and also uses the cylinder liner surface texturing technique to examine the effects of surface texturing on lubrication properties in the presence of transient thermal fluids. The findings indicate that employing transient thermal fluid for determining the mean value of the oil film temperature in isothermal lubrication calculations yields comparable values for minimum oil film thickness and frictional power consumption, while the friction power consumption calculated by the transient thermal fluid is slightly lower. The depth of the recesses on the surface of the cylinder liner should be minimized, while the radius of the texture should be maximized, taking into consideration the current circumstances. Compared with a cylindrical texture, a spherical texture achieves lower friction with good lubrication indexes.

The arrangement of a pit-shaped surface texture on the surface of a cylinder liner significantly affects reductions in piston ring friction, and the influence of the structural parameters and spatial distribution on piston ring friction power consumption is unclear. In this paper, the diameter, depth, axial spacing distance, and radial spacing distance of the pits on the inner surface of a cylinder liner were used as variable parameters to process the surface textures of different schemes, and then a friction and wear test was carried out on UMT piston ring–cylinder liner specimens, several texture schemes with the best anti-friction effect were selected, an engine bench test was carried out by comparing these texture schemes with non-texture schemes, and the frictional torque and fuel consumption of the engine were studied at different oil temperatures. The results show that the depth of the pits in the surface texture of a cylinder liner has a greater influence on the friction reduction effect, followed by the radius. The higher the oil temperature in the engine bench test, the greater the impact of the surface texture. The reduction in fuel consumption was greater in the lower-speed region after structuring the textured cylinder liner compared to the non-textured cylinder liner. Specifically, the friction coefficient was mainly affected by the depth of the pits, and the depths of the pits in the texture schemes with good friction reduction effect were all 17–19 μm. The best friction reduction could be achieved when the pit radius is around 50 μm, with little difference in pit depth. When the oil temperature was 95 °C, the average drag torque reduction was about 1.69 Nm; when the oil temperature was 105 °C, the decrease was about 2.54 Nm; and when the oil temperature was 105 °C, the decrease was about 4.53 Nm. After adding the surface texture of the cylinder liner, the fuel consumption rate of the engine equipped with the structured cylinder liner was generally reduced compared with that of the original cylinder liner engine. Among them, the average and subsequent consumption rate of surface assembly scheme 11 decreased the most, with a value of 1.3 g/kwh.

Lubricating oil and cylinder liner surface textures can significantly reduce the friction coefficient between the piston ring and the cylinder liner, thereby improving engine performance. However, the friction-diminishing mechanisms between the lubricating oil and surface texture remain unclear. Properly combining lubricating oil and surface texture can achieve better friction reduction effects. This paper, based on a transient thermo-hydrodynamic model developed in MATLAB 2020a, conducted numerous simulation experiments to explore the matching characteristics of textured cylinder liners. The study provides theoretical support for the future selection of lubricating oils for textured cylinder liners. The results show that, within the range of the circular texture parameters used in this study, the texture radius is directly proportional to the reduction in friction mean effective pressure (FMEP), while the texture depth is inversely proportional to the FMEP reduction. At the same rotational speed, as the viscosity of the lubricating oil increases, the friction-reducing effect of the texture on the piston ring–cylinder liner pair decreases. When the texture depth is 2 μm, the engine speed is inversely proportional to the reduction in FMEP. As the texture depth increases from 2 μm to 6 μm, there is a significant change in the friction-reducing effect: for the 2 μm texture, the friction-reducing impact decreases with increasing lubricant viscosity, while for the 6 μm texture, the friction-reducing effect increases with increasing lubricant viscosity.