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 d eveloped. The effect of oil film on fuel absorption/desorption was investig ated according to engine speed, load, and mean oil film temperature. Multi- component fuel was employed to quantify the oil film effect. The results sh owed that Henry's constant, which is related to solubility, is the most dom inant parameter in absorption/desorption mechanism of the fuel into oil fil m. 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 time s as large as that of fuel in the oil film. However, the fuel trapped in th e oil film desorbs slower into the combustion chamber than that escaped fro m the piston crevices at the cold engine condition.