Study on the First-Firing-Cycle combustion characteristics of high-altitude and low-temperature environments during diesel engine cold start

Abstract

Cold-start performance is one of the main problems that affects the reliability of diesel engines in high-altitude and cold areas. The First-Firing-Cycle (FFC) is the most important cycle during the cold-start process, which apparently affects the cold-start performance. An environmental simulation storehouse and a 3D simulation model were used to study the spray and combustion of FFC in the start-up phase, which temperature varied from −20℃ to 10℃ and altitudes varied from 0 m to 4000 m. A skeleton mechanism using n-dodecane with 117 species and 649 reactions was proposed. Because of the cold temperature and low air density in the plateau area, the cold-start performance was worse and more difficult to reach idle conditions. Verified by experiments and simulations, the spray and combustion characteristics of FFC during the start-up phase were affected by the altitude and ambient temperature obviously. When the altitude increased or the ambient temperature decreased, the atomization and combustion were insufficient, which ultimately produced less power. The control parameters of the Electronic control unit (ECU) should consider the altitude to obtain better cold-start performance in the future.