The influence of pilot injection timing and quantity on soot, NOx, combustion noise and bsfc has been analyzed on a passenger car DI Diesel engine prototype equipped with a common rail fuel injection system.
The investigated engine operating points were 1500/5, 2000/2, 2500/8 rpm/bar, which are quite typical of EC driving cycles. For each of these operating conditions, the pilot injection quantity was varied by up to 15% of the total injected quantity and the pilot injection timing was varied between 32° and 1° crank angle degrees.
The principal combustion characteristics were determined on the basis of the heat release, and a thorough statistical analysis was performed to infer the correlation between the combustion parameters and soot and NOx emissions.
The obtained results allow an evaluation of the impact of different injection strategies on the combustion process taking into account not only the thermodynamic effects of the pilot injection, but also the effects of the hydraulic and mechanical behavior of the injection system.