Romagnuolo, Luca (2021) Evaporative Emissions from a Gasoline Fueled Vehicle: Predictive Models of Fuel Evaporation from Tank and Canister Dynamics. [Tesi di dottorato]

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Fuel evaporative emissions from a vehicle fuel tank have long been known to be an important source of pollution, and international regulations on automotive Volatile Organic Compounds (VOCs) are becoming increasingly stringent every year, because of their effects on human health and environment. The most cost-effective and widely adopted solution for limiting the release of VOCs to the environment is the use of an EVAP system, which commonly consists of a canister filter filled with activated carbons that stores fuel vapors, by means of adsorption, to make them available for the combustion in the engine cylinders. However, as the automotive world is moving towards hybrid electric solutions, the role of the EVAP system is becoming even more important, because of limited possibilities of canister filter purging. In the present study, the problem of VOCs formation from gasoline vehicle and the EVAP system functioning have been analyzed, under three different aspects. Gasoline evaporation inside the vehicle fuel tank has been experimentally tested by using a VT Mini-SHED, under different environmental temperature conditions, in order to study the fuel vapor formation and leakage from the tank due to diurnal temperature variations (DBLs), when the vehicle is in parking conditions. A 0D semi-empirical model has been developed in MATLAB(R) environment, that is able to predict the amount of fuel vapors that escapes the tank under different environmental temperature conditions, fuel tank dimensions, filling level and gasoline vapor pressure (RVP). Fuel vapors adsorption and desorption phenomena have been analyzed by means of an experimental activity performed on a European-type canister filter, by measuring its mass variation and internal temperatures changes due to the phenomena themselves. A 1D model has been developed in MATLAB(R) environment, to simulate the adsorption phenomenon by evaluating the adsorbed mass and temperature variations during time. Evaporative emissions due to the tank refueling process have also been studied and experimentally measured by using a VT Mini-SHED. A 3D CFD simulation of the refueling process has been carried out, by adding suitable equations to evaluate and predict the fuel vapor quantity that escapes the tank during refueling. The present work is the result of a collaboration among the Department of Industrial Engineering of the University of Naples Federico II (Naples, NA, IT), the R\&D division of Stellantis N.V. (Pomigliano d'Arco, NA, IT) and the Center for Automotive Research of the Ohio State University (Columbus, OH, USA).

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