Modeling and Simulation of Refueling Emissions from Plug-in Hybrid Electric Vehicles

Vehicular evaporative emissions are an important source of volatile organic compounds (VOCs). Moreover, the engines of plug-in hybrid electric vehicles (PHEVs) may not start for a long time, causing the activated carbon canister to not purge well in-use and to become saturated with fuel vapor. Therefore, the problems of evaporative emissions and refueling emissions of PHEVs are still severe. The objectives of this article are to model and simulate the refueling emissions from PHEVs to shorten the design and development cycle. To achieve the goals, the release of refueling emissions is divided into two stages: the depressurization stage and the refueling stage. The mathematical model has been established by means of the ideal gas law and the gas mass transfer and diffusion law. Then, the numerical model is built and the volume of fluid (VOF) model was applied in the simulation. Moreover, the numerical model was validated by experiment on internal pressure increase of the fuel tank. The baseline case is conducted under the condition that the fuel dispensing rate is 50 L/min. Finally, different fuel dispensing rates are set to simulate refueling emissions characteristics. The simulation results indicate that the pressure is negative at the outlet of the filler pipe connecting to the atmosphere, causing all the refueling vapors to flow to the activated carbon canister and potentially some vapor may be released to the atmosphere through the canister vent. Moreover, the mass of refueling emissions per liter of gasoline rises with the increasing fuel dispensing rate. The maximum mass of refueling emissions per liter of gasoline, under the condition of fuel dispensing rate of 50 L/min, is 0.01258 g/L, lower than the limit regulated in the new emission regulation (CHINA 6).