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Biodiesel was prepared through transesterification of castor oil and ethanol. The optimization of parameters related to the yield of transesterification, such as oil to ethanol molar ratio, concentration of catalyst, reaction temperature and reaction time, was investigated. The results indicated that the optimum condition for castor oil ethyl ester (COEE) production was 1:12 oil to ethanol molar ratio, 1.5% catalyst concentration, 40 °C reaction temperature and 150 minutes reaction time. To avoid extremely high viscosity of castor oil which can affect the fuel injection system, COEE was blended with commercial diesel fuel at different concentrations ranged from 5%-15% volume and key properties of fuel blends, mainly focused on fuel lubricity and viscosity were evaluated.

SI-CAI hybrid combustion, also known as spark-assisted compression ignition (SACI), is a promising concept to extend the operating range of CAI (Controlled Auto-Ignition) and achieve the smooth transition between spark ignition (SI) and CAI in the gasoline engine. In order to investigate the effect of the thermal boundary condition on the hybrid combustion, the experiments with different coolant temperatures are performed to adjust the chamber wall temperature in a gasoline engine. The experimental results indicate that increasing wall temperature would advance the combustion phasing, enlarge the peak heat release rate and shorten the combustion duration. While the capacity of the wall temperature effect on the hybrid combustion characteristics are more notable in the auto-ignition dominated hybrid combustion.