In the diesel engine industry, the growing trends are toward wider use of electronically controlled high pressure fuel injection equipment to provide better engine performance, while conforming to the stringent exhaust emission standards.
Although there have been some recent announcements of a diesel engine that applies an electronically controlled common rail type fuel injection system, there is little literature published about any attempt to reduce both exhaust emissions and noise and to improve engine performance by varying injection pressure and injection timing independently and introducing pilot injection in combination.
This paper describes the details of a study made on the parameters associated with injection timing, injection pressure and pilot injection and the procedures for their optimization, with an electronically controlled common rail type fuel injection system installed in an in-line 6-cylinder 6.9 liter turbocharged and intercooled DI diesel engine.
The study made it clear that not only high pressure injection, but also pilot injection are effective for the reduction of smoke at high load, particularly in low speed ranges. It also became clear that pilot injection was useful for reduction of NOx and HC at low load and also for reduction of noise in all engine operating ranges.
Based on the results of the study, the parameters of injection pressure, injection timing, pilot injection quantity and pilot injection timing were optimized in all engine operating ranges. Consequently, the torque at low speeds was increased and the particulate was cut by half in comparison with the conventional engine, while reducing smoke and noise, without increasing exhaust emissions. Moreover, pilot injection was found to be very effective for improvement of engine startability and reduction of white smoke at low temperatures.