Numerical simulation of the performance of a diesel cycle operating with diesel-biodiesel mixtures

Abstract

This paper conducted a numerical simulation of the thermodynamic cycle of a diesel engine, which runs on diesel/biodiesel mixtures, and takes the processes of compression, combustion and expansion into account. The zero-dimensional mathematical model was adopted in order to build the numerical modeling based on the First Law of Thermodynamics and also of the state equation in order to obtain the pressure and temperature profiles of gases inside the cylinder which vary depending on the angle of the crankshaft. The mathematical modeling included taking account of the transfer of heat through the walls, the energy released during combustion considering the Wiebe function, the thermophysical properties of the reagents and the products and the geometric parameters of the engine. The largest relative error found was the 2% in the pressure which showed a good agreement between the simulated and experimental results from previous studies. A parametric analysis was performed considering the fraction of diesel and biodiesel in the mixture, the start angle of the combustion and the equivalence ratio with a view to assessing their effect on the performance of the engine. The results show that a reduction in temperature and in pressure values was achieved when the biodiesel share in the mixture is increased. This led to altering the values of the performance parameters values. In addition, the peaks of pressure and temperature were increased by raising the equivalence ratio which brings forward the point at which the fuel starts to burn due to the increases in the pressure and maximum temperature. It was verified that Wiebe function parameters have a direct influence not only on the pressure and temperature values but also on the performance data of the engine.