Study of the influence of emission control strategies on the soot content and fuel dilution in engine oil

[EN] The engine oil contamination by both particulate matter (PM) and fuel is becoming an important problem since strategies to control pollutant emissions in internal combustion engines (ICE) significantly increase their presence in engine oil. As a consequence, the engine oil loses its tribological properties compromising engine lubrication and leading to potential problems in engine such as wear, corrosion, etc. For that reason, the study of the oil degradation and contamination due to these strategies have a special interest to the engine manufacturers and engine oil formulators. In this paper, the engine oil soot content and fuel dilution is analysed under real engine conditions. The study is addressed from two different but complementary points of views. First, on-line measurements at several engine operating conditions are performed in order to further understand how the soot generation correlates with the oil soot content and other derived problems on oil performance. Then, experimental data available after the experimental campaign is used to calibrate a numerical model, based on Computational Fluid Dynamics (CFD), that estimate the amount of soot particles settled in the engine oil. Results show that soot particles are more present in oil when operating high load-speed conditions and during the Diesel Particulate Filter (DPF) regeneration cycles. Regarding the fuel dilution, delayed post-injections are critical since they significantly increase the amount of fuel in the engine oil. Numerical results also show the relationships between the soot particles generated during combustion and the amount of soot in engine oil, giving an enhanced comprehension of soot-in-oil deposition mechanisms.