Research on the lubrication failure mechanism of engine cylinder liner-piston ring resulting from biofuel blending under incomplete combustion conditions

Abstract

As the shipping industry pursues sustainable alternatives, biofuel has emerged as a promising fuel but introduces risks like fuel dilution into lubricating oil, particularly threatening cylinder liner-piston ring (CLPR). In this study, marine lubricating oil was mixed with B24 biofuel according to different mass fractions, and their physicochemical properties were analyzed. The results show that with the increase of the dilution concentration of biodiesel, the viscosity decreases significantly. When the dilution concentration is 20%, the viscosity of the lubricating oil decreases by 18.97% (40°C) and 16.63% (100°C) respectively, and the thermal stability and oxidation resistance of the lubricating oil also decline. Tribological tests show that both the friction coefficient and wear quality of CLPR have increased. Specifically, under high-speed and heavy-load working conditions, compared with pure lubricating oil, the average friction coefficient increases by up to 19.4%, the wear mass increases by up to 26%, and the vibration amplitude during the test process also increases significantly. This study provides valuable insights into the long-term operational challenges brought about by the use of marine biofuel and determines 10 wt% as the dilution threshold for B24 biofuel, offering a scientific basis for optimizing the lubrication strategy of marine engines.