Numerical Simulation of Polycyclic Aromatic Hydrocarbon Formation in n-Heptane HCCI Combustion

By modifying the SENKIN code of CHEMKIN chemical kinetics package, the combustion processes and the characteristics of hydrocarbon (HC) and carbon monoxide(CO) emissions of a HCCI engine were simulated. Furthermore, the formation of benzene (A₁) and polycyclic aromatic hydrocarbons including naphthalene (A₂), phenanthrene (A₃), and pyrene (A₄) in n-heptane HCCI combustion were analyzed. A multi-zone computational model was built and a detailed chemical kinetics mechanism that consists of 107 species and 542 reactions was adopted. The results show that the multi-zone model and the reaction mechanism adopting in this paper are basically correct through the comparison of the cylinder pressure between experimental data from the literature and the results by this model. It is shown that the crevice zone is the main source of the HC emission, while the CO emission is mainly from the boundary layer. Among these four aromatic and polycyclic aromatic hydrocarbons, the emission of A₁ is the highest, A₂ is following, and the emission of A₄ is almost zero.