异辛烷HCCI燃烧下多环芳烃形成的多维数值研究

Multidimensional CFD Research on Polycyclic Aromatic Hydrocarbons in Iso-Octane HCCI Combustion

将发动机多维CFD程序KIVA-3V与化学动力学程序CHEMKIN III相耦合,对异辛烷HCCI燃烧下芳香烃(苯)与多环芳烃(萘、菲及芘)的生成及演变规律进行了详细分析。发动机以异辛烷为燃料,其化学反应采用了异辛烷的燃烧与分解、多环芳烃生成的详细反应机理。结果表明,此计算模型所得到的缸内压力及放热率的变化趋势与实验基本吻合;缸内混合气着火前,A1(苯)、A2(萘)、A3(菲)与A4(芘)的质量浓度场非常不均匀,在缸中心区域A1-A4质量浓度较高,而在边界层及缝隙区则相对较低;缸内混合气着火后,在缸中心区域及缝隙区A1-A4质量浓度较低,而在边界层则相对较高;当排气门开启时,仅仅缝隙区中A1-A4质量浓度较高,而在缸中心区及边界层区则相对较低,同时在这4种芳香烃与多环芳烃中,苯的质量浓度最高,萘其次,而芘则极低。

By coupling the KIVA--3V engine CFD package with the CHEMKIN III chemical kinetics package, the formation and evolvement mechanisms of the aromatic （benzene） arid polycyclic aromatic hydrocarbons （include naphthalene, phenanthrene and pyrene） in iso-- octane HCCI combustion were simulated. Iso-- octane was used as fuel and the detailed reaction mechanisms of combustion of iso-octane and formation of the polycyclic aromatic hydrocarbons were adopted. The results show that the numerical simulations of the pressure and heat release through this computational model are the same as the experimental results. Before ignition, the mass fraction fields of A1 （benzene）, A2 （naphthalene）, A3 （phenanthrene） and A4 （pyrene） are very inhomogeneous. Comparing with the boundary zone and the crevice zone, the mass fractions of A1 --A4 in the core zone are higher. After ignition, comparing with the core zone and the crevice zone, the mass fractions of A1 --A4 in the boundary zone are higher. At the time as the vent opening, comparing with the core zone and the boundary zone, the mass fractions of A1- A4 in the crevice zone are higher. At the same time, among these four aromatic and polycyclic aromatic hydrocarbons, the mass fraction of A1 is the highest, A2 is following, and A4 is almost zero.