Application of a Combustion Model to a Diesel Engine Fueled with Vegetable Oils

The paper presents the application of a three component model to the theoretical study of the combustion process of a Diesel engine fueled with sunflower oil and sunflower oil-Diesel fuel mixtures. The model assumes that the working fluid consists of three components: the fresh air, the flame and the burned gases. The combustion model uses the energy conservation equation: vc·Qc·dξα=dUα+dLα+dQwα, [1] where vc is the fuel cyclic dose, Qc is the fuel heating value, ξα=vcα/vc, vcα is the quantity of burned fuel up to the moment α, Uα is the internal energy of the working fluid, Qwα is the heat exchanged through the cylinder walls and Lα is the mechanical work. The heat release law was assumed to be a Vibe type one: ξα=Rc·[1−exp(−6.9·AmPp+1)]+(1−Rc)·[1−exp(−6.9·Amd+1)], [2] where: ·Ap=(α−αd)/(αP−αd) and A=(α−αd)/(αF−αd); ·αd-start of combustion angle; ·αf-end of combustion angle; ·αP-end of rapid combustion angle. Using Eqs. [1] and [2] we have obtained the cylinder pressure during combustion, for the vegetable fuels taken into account; the peak values were confirmed during the experiments.