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 : υ_c・Q_c・dξ_α=dU_α+dL_α+dQ_<ωα>, [1] where υ_c is the fuel cyclic dose, Q_c is the fuel heating value, ξ_α=υ_<cα>/υ_c, υ_<cα> is the quantity of burned fuel up to the moment α, U_α is the internal energy of the working fluid, Q_<wα> is the heat exchanged through the cylinder walls and L_α is the mechanical work. The heat release law was assumed to be a Vibe type one : ξ_α=R_c・[1-exp(-6.9・A^<m_p+1>_P)]+(1-R_c)・[1-exp(-6.9・A^<m_d+1>)], [2] where : ・A_P=(α-α_d)/(α_P-α_d) and A=(α-α_d)/(α_F-α_d); ・α_d-start of combustion angle; ・α_f-end of combustion angle; ・α_P-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.