A novel finding on tribological, emission, and vibration performances of diesel engines linking to graphene-attapulgite lubricants additives under hot engine tests

The cylinder liner-piston ring (CL-PR) that worked under harsh conditions is extremely susceptible to wear, and its friction loss is the primary source of mechanical loss of engines, affecting its equipment reliability and energy consumption. Recently, the use of low sulfur fuel oils (LSFO) aggravated the wear of the CL-PR, further increasing friction loss. Furthermore, the emissions of diesel engines also affect the environment and human health. In this study, the graphene-attapulgite (G-ATP) additive was prepared and applied to engines in response to these challenges. The prepared G-ATP additive was dispersed into 5040 lubricating oil with a 0.25 wt% concentration, then the effects of the additive on engines were investigated under hot test conditions with a speed of 1750 rpm. It was found that the G-ATP additive displayed excellent tribological properties, the wear mass loss of the piston ring was reduced by 64.5% with the addition of the G-ATP additive, and the wear of the cylinder liner was significantly reduced. Meanwhile, owing to the excellent tribological properties and thermal conductivity of the G-ATP additive, the HC and NOx emissions of the engine were reduced by 3.0% and 6.1%, respectively. Additionally, the vibration performances of the engine were improved by 42.1% in the final stage. These findings revealed the potential mechanism of the G-ATP additive for performance enhancements of diesel engines, as well as the relationships between the emission and vibration of engines and tribological properties of CL-PRs, which promote the energy saving and emission reduction of engines.