Improvement of the efficiency and emission characteristics for compression ignition engine operated in gasoline compression ignition mode fueled with gasoline-biodiesel blends

Abstract

Among the internal combustion engines, compression ignition (CI) engine shows the most efficient as fuel to energy conversion. The potential improvement in thermal efficiency and emission characteristics of CI engines fueled with gasoline-biodiesel blends running on GCI mode was investigated in an experimental series in this study. Fuels were injected directly into the cylinder by using common rail injection system. Commercial gasoline (GB00), diesel (D100), pure soyabean biodiesel (B100) and four gasoline-biodiesel blends (GB05, GB10, GB15, and GB20) were used in this study. The first step in conducting this research was the experimental works on an injection flow rate measurement of gasoline-biodiesel blend fuel to obtain its characteristics during injected in the cylinder. The second step was the experimental works for GCI engine testing fueled with gasoline-biodiesel blends with single injection strategy. The third step was experimental works on GCI engine fueled with gasoline biodiesel blends using main and pilot injection strategies. The last but not the least, fourth step was the experimental work on the effect of EGR and intake boosting on GCI engine combustion and emissions when fueled with gasoline-biodiesel blends. In single injection strategy, the results showed that the earlier the SOI of GB blends, the shorter the ignition delay compared to diesel fuel. Furthermore, the thermal efficiency for GB blends was found to be almost equivalent to diesel fuel for all conditions. In the case of emission, GB blends produce lower HC compared to diesel, as expected, because of their homogeneous mixing capabilities. However, a higher NOx emission from GB blends was observed, which might be a result of excess oxygen in the fuel. Using multiple injections and increasing the temperatures of the intake, oil, and engine coolant could result in improved combustion and engine efficiency. Multiple injections of GB05 showed decreased CO emissions, which could be due to the pilot injection of GB05. The biodiesel content and using gasoline as a highly volatile fuel in GB05 showed the significant effect of lowering total hydrocarbon and CO emissions. It is found that changes in EGR rate, intake boosting pressure, and injection strategies affect on ignition delay, maximum pressure rise rate and thermal efficiency, which is closely tied to HC, CO, NOx, and smoke emissions, respectively.