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As a type of alternative fuel, biodiesel has advantages in reducing greenhouse gases and ensuring energy security. Compared with petroleum diesel, biodiesel has different lower calorific value, oxygen content and octane number that would raise problems when the unoptimized common rail diesel engine is fueled with biodiesel or its petroleum diesel blends. Among these problems, decreasing full load torque output and increasing NOx and BSFC are significantly important. Fuel injection parameter calibration and optimization experiments are carried out in an in-line 6-cylinder 8.82 liter turbocharged and intercooled common rail diesel, which is equipped with Denso ECD-U2 fuel injection system, SCR (Selective catalytic reduction) and DPF (diesel particulate filter). To avoid after-treatment apparatus' coupling influence and re-calibration, emission measure point is set in front of catalysts. The experiment adopts B20 biodiesel as test fuel.

Effects of biodiesel fuel on nucleation mode particles were studied on a direct injection, high pressure common-rail diesel engine for passenger cars. Particle number and size distribution of the diesel engine were obtained using an Engine Exhaust Particle Sizer (EEPS). The base petroleum diesel, three different blend ratios of petroleum diesel/biodiesel (10%, 20% and 50% v/v biodiesel blend ratios), and the pure biodiesel fuel (obtained and converted from Jatropha seed in China) (B0, B10, B20, B50 and B100 fuels) were tested without engine modification. Experiments were performed on a series of engine operating conditions. The particle number size distribution of the engine shows unimodal or bimodal log-normal distribution. With the biodiesel blend ratios increasing, the number of nucleation mode particles increases at all test engine operating conditions and accumulation mode particles decreases at most engine operating conditions.