A model was developed to assess the absorption and desorption of fuel in oil film and in the binary diffusion of oil and fuel films. This was investigated with a parametric study according to engine speed, load and oil film temperature. The results show that Henry's constant, which is related to solubility, is the most dominant parameter in the absorption/desorption mechanism of fuel into the oil film. Under warm-up conditions, engine speed had little influence on the amount of fuel absorbed/desorbed, but when the oil film temperature was low, the quantity of fuel absorbed/desorbed decreased with increasing engine speed. Liquid fuel on the oil film and piston head caused higher hydrocarbon (HC) emissions, and under base conditions (a simulated cold engine), the amount of fuel vaporized from fuel film and desorbed from wetted oil film was 24.5 per cent of the stoichiometric fuel mass. The effect of oil film with liquid fuel was 5.3 times larger than that of oil film without liquid fuel. The amount of fuel that escaped from the piston crevice was 1.3 times larger than that of fuel in the oil film. However, the fuel trapped in the oil film desorbed into the combustion chamber more slowly than the fuel that escaped from the piston crevices under cold engine conditions.
