Investigation of the combustion characteristics and the emissions characteristics with diesel low-temperature combustion

Abstract

Diesel low-temperature combustion is one of the new combustion technologies. Exhaust gas recirculation is an important measure required to realize low-temperature combustion. The paper mainly investigated the combustion characteristics and the emissions characteristics with diesel low-temperature combustion. Experiments were carried out on a modified single-cylinder heavy-duty diesel engine. The results showed that, with increasing exhaust gas recirculation rate, the peak pressure decreases while the combustion rate initially increases and then decreases. A high boost pressure will increase the mechanical load of the engine. With increasing exhaust gas recirculation rate, the nitric oxide proportion initially decreased and then increased. The nitrogen dioxide proportion had the opposite trend. The nitrous oxide proportion was very low at different boost pressures. Low-temperature combustion faces two new problems. One is that the proportion of small-molecule hydrocarbons increased, such as methane and formaldehyde. The other is that the small-diameter particulate matter concentration increased. Both small-molecule hydrocarbons and small-diameter particulate matter cause great harm to human health. At different exhaust gas recirculation rates, the mechanisms of reducing the soot emissions with a higher injection pressure were different.