Experiment and Chemical Kinetics Analysis of Active Atmosphere with Different Fuels in HCCI Combustion

摘要

The effect of gasoline, ethanol, and methanol fuels on the formation of active atmosphere for HCCI combustion control was investigated in a HCzCI engine with negative valve overlap (NVO). Gasoline, ethanol, and methanol were tested as preinjection fuel in the NVO period, respectively. A reduced RPF mechanism (47 species, 142 reactions), a detailed ethanol mechanism (32 species, 167 reactions), and a detailed methanol mechanism (57 species, 383 reactions) were embedded into a zero-dimensional engine simulation model to study the chemical kinetic process of the active atmosphere formation. The results show that the active atmosphere is formed through the pyrolysis, oxidization, and reforming reactions of the fuel preinjected into the high temperature residual gas during the NVO period. Both heat and intermediate reactants produced during this process provide an active atmosphere for the main combustion, which leads the advance of the combustion phase. But thermal atmosphere is much more effective in advancing the combustion phase than chemical atmosphere. The results also indicate that the specification of the active atmosphere is influenced by oxygen concentration and initial temperature during the NVO period. Methanol is the most effective fuel in forming a thermal atmosphere in all cases and is less sensitive to the oxygen concentration and initial temperature during the NVO period. The activity of forming an active atmosphere increases in the sequence: gasoline < ethanol < methanol.