Biodiesel Fuel from Chlorella vulgaris and Effects of Its Low-Level Blends on the Performance, Emissions, and Combustion Characteristics of a Nonroad Diesel Engine

Chlorella vulgaris is widely distributed in China and has the advantages of high oil content, short growth cycle, and wide growth space. Chlorella vulgaris biodiesel fuel (CVBF) made from Chlorella vulgaris has great development potential. In this study, the preparation, composition, and physicochemical properties of CVBF in China were analyzed, and the performance, emissions, and combustion characteristics of B0 and B5 (5% v/v CVBF and 95% diesel) in nonroad diesel engines were compared. The results show that CVBF has different physical and chemical properties than diesel fuel. The brake power and torque output of B5 is lower than B0, and the brake specific fuel consumption and brake specific energy consumption are higher. The maximum in-cylinder pressure and heat release rate of B5 is lower than B0, while the rate of cylinder pressure is higher, and the corresponding crankshaft angles are all advanced. The ignition delay and the premixed combustion duration of B5 are longer, while the diffusion combustion duration and the total combustion duration are slightly shorter. B5 has slightly higher NOX emissions, but less CO emissions. B5 can significantly reduce unburned hydrocarbon and smoke emissions, especially at high loads. Low-level CVBF blends can partially replace diesel fuel, with the advantages of improved combustion processes and effective emissions reduction.