Research on the Influences of Addition of Biodiesel on the Equilibrium Concentrations and Thermodynamic Properties of Combustion Products for Conventional Diesel Fuel

Abstract

To deal with the increasingly stringent energy crisis and atmospheric pollution problems, biodiesel is regarded as one of the alternative biofuels with great potential for replacing the conventional diesel fuel, thus it is necessary to investigate the influences of addition of biodiesel to conventional diesel fuel on the combustion products. To this end, Jatropha biodiesel is taken as an example and under the assumption that all the combustion products are at chemical equilibrium, a system of nonlinear equations with the equilibrium concentrations of 10 combustion products as the unknown variables is constructed based on the equilibrium constant method and the numerical solutions are obtained by applying Newton-Raphson iterative method. On this basis the influences of biodiesel blending ratio on the equilibrium concentrations of the combustion products and the thermodynamic properties of burned gases mixture is investigated. The simulation results show that the addition of biodiesel does not cause significant influences on the equilibrium concentrations of combustion product, and as the three major greenhouse and poisonous gases, the relative changes of equilibrium concentration for CO2, NO and CO are less than 3.52% but with unclear trends and the influence is more significant at the “fuel rich” condition; on the other hand, the mass-based combustion products rates of CO2, NO and CO for a unity of blended fuel mass increases with blending ratio. For the thermodynamic properties of burned gases mixture, it is observed that both the constant-pressure and -volume specific heat increase slightly. The model presented here can be integrated into the engine dynamic simulation model conveniently, which lays the foundation for investigating the influence of addition of biodiesel on the engine power, economic and emission performance.