In Common-Rail DI Diesel Engines, multiple injection strategies are considered as one of the methodologies to achieve optimum performance and emission reduction. However, multiple injections open a whole new horizon of parameters which affect the combustion process. These parameters include the number of injection events, the duration between the starts of each injection event, the splitting of the total fuel mass on the different injection events, etc. In the present work, the influence of the number of injection events and the influence of the duration between the starts of each injection event on emission levels are investigated.
Combustion and pollutant formation were experimentally investigated in a Common-Rail DI Diesel engine. The engine was operated at conventional part-load conditions with 2000 rpm, no external EGR, and an injected fuel mass of 15 mg/cycle. The fuel mass was injected via one injection event (one main injection), two injection events (pilot and main injection) or three injection events (pilot, main, and post injection), respectively. For the single injection event, a variation of start of injection was carried out. For the two strategies with more than one injection event, a variation of start of injection in combination with a variation of the duration between the starts of the injection events was carried out. The influences of these variations on pollutant formation are discussed for the investigated engine.