Effects of Injection Strategy on the Nano-Particle Emission Characteristics of a Direct Injection Diesel Engine

摘要

In this study, the influence of variation of engine speed, injection mass, injection timing, and split injection strategy on the combustion, exhaust emissions and nanoparticle emission characteristics in a small direct injection (DI) diesel engine were experimentally investigated. The experimental results show that with the increase of engine speed, the peak combustion pressure and peak ROHR profile were increased and ignition delays were shortened. The NOx emission was considerably increased. The combustion characteristics of the three different injection mass cases indicated similar trends and patterns of combustion pressure and rate of heat release at a given test condition. As the injection fuel mass increased, the concentrations of soot emission generally showed increasing patterns with advanced injection timing. The strategy of a first injection mass of 7 mg and a second injection mass of 3 mg (7+3 mg) resulted in the maximum combustion pressure compared to the other cases. As the first injection mass was increased, the mode diameter of particles increased, and with the increase of the first injection mass, a significant shift to larger particle diameters was observed. However, with the reduced first injection mass, the number per volume of ultrafine particles ranges, was significantly increased.