Effects of temperature inhomogeneities on the HCCI combustion in an optical engine

► Combustion chamber geometry affects HCCI heat release and pressure rise rate. ► Autoignition occurred at the center of the A-type combustion chamber. ► Autoignition was more dispersive and closer to the chamber wall for V-type. ► A-type combustion chamber induced higher turbulence intensity. ► A-type combustion chamber enhanced the temperature inhomogeneity.