Modeling of the dynamic process of fuel absorption/desorption in the oil film in SI engines

A modeling for absorption/desorption of the fuel in the oil film has been developed. The effect of oil film on fuel absorption/desorption was investigated according to engine speed, load, and mean oil film temperature. Multi-component fuel was employed to quantify the oil film effect. The results showed that Henry's constant, which is related to solubility, is the most dominant parameter in absorption/desorption mechanism of the fuel into oil film. The oil segments close to the top of the cylinder liner have significant contribution to the fuel absorption and desorption process than other oil segments. At warm-up condition, engine speed has a little influence on the amount of fuel absorbed/desorbed. However, when the oil film temperature is low, the quantity of fuel absorbed/desorbed decreases with the increasing engine speed. The amount of fuel trapped in piston crevice is 2 to 2.3 times as large as that of fuel in the oil film. However, the fuel trapped in the oil film desorbs slower into the combustion chamber than that escaped from the piston crevices at the cold engine condition.