Compression-ignition of gdi sprays in a constant volume combustion chamber

Gasoline compression-ignition combustion has the potential to produce high thermal efficiency and low emissions. Different ambient temperature and oxygen levels can have great effects on the auto-ignition. In this study, experiments were carried out in a constant volume combustion chamber using a hollow-cone gasoline direct injection (GDI) injector, under a given ambient gas density condition. Different oxygen levels were used to simulate different exhaust gas recirculation (EGR) levels. The effect of ambient temperature and EGR levels on the combustion development were investigated and analyzed. The heat release rate and cumulative heat release rate under each condition are compared. High speed videos of the flame development are also recorded and studied. With the increase of ambient temperature, the cumulative heat release rate of gasoline compression ignition decreases, while the peak luminosity and average luminosity increase by a large scale. The auto-ignition delay also decreases with the increase of ambient temperature. It is noted that the peak heat release rate first increases then decreases with the increase of ambient temperature. On the other hand, higher EGR level leads to lower heat release rate, longer flame duration, much longer auto-ignition delay and lower flame luminosity. The results also suggest that a high ambient temperature can help reduce the case-To-case variation of combustion process.