Numerical Simulation Of Hcci Combustion Process Based On Diesel Surrogate Fuel Design

HCCI combustion gives the internal combustion engine a new way to achieve high efficiency and low emissions. As HCCI combustion process is mainly controlled by the chemical kinetics, So the detailed chemical mechanisms of hydrocarbon fuel must be placed in the core of the study. Current surrogate fuel for diesel HCCI simulation is generally limited to one-and two-component, and multi-component surrogate model is usually formed by the simplified mechanism. In this paper, A new three-component diesel surrogate fuel model is formed by the detailed kinetic mechanism and the single-zone model and multi-zone model are used to study this new surrogate model on diesel HCCI combustion and emission performance.Based on the composition of the diesel fuel, several components are chosen from alkanes, aromatics and cycloalkanes; then according to the diesel surrogate fuel construction criterion, and compare the fundmental experiment data and detailed mechanism in the literature, N-heptane, toluene and cyclohexane are selected as ideal components for this new diesel surrogate fuel. All three detailed mechanism are chosen from the detailed mechaisms developed by the Lawrence Livermore National Laboratory in the United States, and Cross-reaction mechanism between heptane and toluene is added to the three-component detailed model.Firstly, by using the constant volume and single-zone model respectively, the best ratio of the heptane:toluene:cyclohexane of8:1:1is determined for the three-components diesel surrogate fuel. And then, by comparing with two-component and single component surrogate fuel model on apparent heat resealse and ignition delay, the new three components model predicts very good with the experimental data.Thirdly, the multi-zone model is used to study the emission performance of HCCI engine by this new three-components model. The results show that the wall boundary layer and the crevice region is the main source of of CO and UHC emissions. Therefore, to obtain low emissions and high efficiency, the crevice region should be minimized and the wall temperature should be appropriatly increased.