Abstract: The effects of the addition of ethylhexyl nitrate (EHN) and polyoxyethylene dimethyl ether (DMMn) on the performance of a single cylinder diesel engine were investigated by adjusting the intake pressure to simulate the plateau environment at different altitude. The effects of altitude, EHN, DMMN and their combination on engine output power, fuel economy and combustion characteristics were compared and analyzed. The results showed that with the increase of altitude, the excess air coefficient decreased, which led to the increase of exhaust temperature, the decrease of maximum output power and the deterioration of fuel economy due to the decrease of combustion pressure in the cylinder. The addition of DMMn could effectively increase the excess air coefficient, thereby reducing the exhaust temperature, reducing the heat load of the engine, and also improving the thermal efficiency and fuel energy utilization. The combination of EHN and DMMn could further reduce the exhaust temperature and improve the thermal efficiency. Through fuel quantity compensation, the output power of the engine could be effectively recovered at the same exhaust temperature, which was about 1.45% higher than the reference fuel at different altitudes.

Key words: diesel engine, plateau, oxygenated component, additive