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The purpose of this study was to gain a better understanding of the effects of port fuel injection strategies and thermal stratification on the HCCI combustion processes. Experiments were conducted in a single-cylinder HCCI engine modified with windows in the combustion chamber for optical access. Two-dimensional images of the chemiluminescence were captured using an intensified CCD camera in order to understand the spatial distribution of the combustion. N-heptane was used as the test fuel. The experimental data consisting of the in-cylinder pressure, heat release rate, chemiluminescence images all indicate that the different port fuel injection strategies result in different charge distributions in the combustion chamber, and thus affect the auto-ignition timing, chemiluminescence intensity, and combustion processes. Under higher intake temperature conditions, the injection strategies have less effect on the combustion processes due to improved mixing.

The influence of different combustion chamber configuration, intake temperature, and coolant temperature on HCCI combustion processes were investigated in a single-cylinder optical engine. Two-dimensional images of the chemiluminescence were captured using an intensified CCD camera in order to understand the spatial distribution of the combustion. N-heptane was used as the test fuel. Three combustion chamber geometries with different squish lip, salient, orthogonal, reentrant shape, referred as V-type, H-type, and A-type respectively, were used in this study. Intake temperature was set to 65°C and 95°C, while coolant temperature was set to 85°C. The experimental data consisting of the in-cylinder pressure, heat release rate, chemiluminescence images all indicated that the different combustion chamber geometries result in different turbulence intensity in the combustion chamber, and thus affect the auto-ignition timing, chemiluminescence intensity, and combustion processes.