Optimization of a Common Rail Diesel Engine Start-up Process

The high emission level during start-up process of common rail diesel engine is still a problem for ultra low emission control. For the map-based common rail system, engine start-up process goes through the initialization of injection and rail pressure build-up process, so the fuel injection status is not stable. Based on the analysis of the characteristics of rail pressure build-up, engine speed variety and exhausted smoke emission during engine start-up process, it is found that the injection parameters of the initial phase of engine start-up have large effects on the start-up time and smoke emission. To optimize the smoke emission, this paper makes a study on the methods of determining the injection parameters during start-up by means of well-phased investigation of engine speed and orthogonal bench test. The research is carried out on a 6-cylinder 7.8L turbocharged diesel engine equipped with a DENSO ECD-U2 common-rail system. The optimization result shows a one third decrease in engine smoke emission with about the same start-up time, and with little amount of bench tests.