A Fundamental Investigation On Chemical Kinetic Models Of HCCI Combustion For Gasoline Surrogate Mixtures

Homogenous charge compression ignition (HCCI) combustion is being paid much attention and widely investigated due to their potential for high efficiencies and low emissions. The combustion in HCCI engine is controlled by the chemical kinetics of the fuels, which play a key role in combustion process and emission. Gasoline is one of the most important fuels in internal combustion engine. It is a complex mixture of hundreds of hydrocarbons, and is faced with the problem of many basic theories in numerical simulation. This thesis focuses on developing appropriate kinetic models of gasoline surrogate mixtures for HCCI combustion mode. The principal aim of this work is to understand gasoline HCCI combustion process and further development.Primary reference fuel (PRF) is applied widespread as gasoline surrogates. Based on the analysis of PRF detailed mechanism, chemical kinetic calculation was performed in HCCI engine. The computation results with four typical mechanisms including shock tube, rapid compression machine and HCCI engine indicate that these mechanisms are different in concrete experimental conditions. Therefore, a skeleton mechanism for HCCI engine including 42 species and 71 reactions was developed. It could predict CO and HC emissions, ignition point and burn rate of HCCI engine. The simulations show that this skeleton mechanism model generally agrees well with those of the detailed chemical kinetic model. Thus, the highly efficient HCCI engine simulations using chemistry with multi-dimensional CFD are attainable by using the present model.With regard to the influence of aromatic hydrocarbon, toluene reference fuel (TRF), a ternary mixture of iso-octane, n-heptane and toluene, is suitable as a gasoline surrogate fuel for HCCI combustion simulation. A review of currently TRF oxidation mechanisms was performed, and it indicates that most of those are detailed chemical kinetic model. A reduced kinetic model for TRF including 70 species and 196 reactions was constructed for HCCI combustion. Comparison of various experimental data, including shock tube tests and HCCI engine experiments, shows that the present TRF mechanism performs well. Response surface method (RSM) is applied for the octane number of any arbitrary tri-component gasoline surrogate consisting of toluene, i-octane and n-heptane. Given the octane number, the component proportion of TRF could be predicted.In HCCI combustion conditions, the research results of primary reference fuel, toluene reference fuel and gasoline fuel indicate that the predicted calculation of toluene reference fuel is satisfactory, and heat release rate of primary reference fuel is lower. Addition of toluene, Production benzyl is oxidated to OH with HO2, which consumes more fuel, improves reaction rate. In view of gasoline surrogate mixture is still need further improvement, Diisobutylene, as a important candidate, could be considered. It is an additional component that is important to include based upon present and continuing uses as gasoline surrogate. The HCCI combustion characteristics and chemical kinetic of diisobutylene were studied numerically.