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Ethanol is regarded as a potential alternative fuel for combustion engine as it provides lower exhaust emissions, higher efficiency and higher octane rating. However, the solubility of ethanol in oil can effect lubricant quality. The impact of ethanol-blend gasoline on lubricants is a matter of concern that must be addressed. With this in mind, the current study investigates the effect of blending ethanol with gasoline on the oil layer adsorption/desorption mechanism. The blends used for the study are E0, E5, E10, and E15. The study is carried out with the help of a mathematical model that predicts the fuel adsorbed/desorbed in the oil layer of an engine. The mathematical model predictions are compared to experimental results obtained on a single-cylinder gasoline engine. Fuel adsorbed in the oil layer ranges from 0.46% for E0 fuel to 0.35% for E15 fuel. Similarly, the desorbed fuel ranges from 0.45% to 0.29% as the ethanol fraction increases from 0% to 15%.

Unburned hydrocarbon (HC) emission results because part of the fuel inducted into the engine escapes combustion. HC emission is dependent on many mechanisms such as adsorption and desorption of fuel in oil layer, flame quenching, fuel escaping into crevices and accumulation of fuel in engine deposits, etc. Out of these, the oil layer adsorption/desorption mechanism contributes to about 25-30% of total engine-out HC emissions. In this work adsorption/desorption mechanism is studied considering the engine to be fueled with different fuels. The fuel adsorbed/desorbed in lubricating oil is modeled with a one-dimensional partial differential equation (PDE). One dimension PDE is chosen as the transverse flow across the oil film is considered to be negligible. The PDE is solved using finite difference explicit scheme in which the space derivatives and the time derivatives are approximated with a second order central difference method and forward Euler method, respectively.