关键词: 预喷正时；柴油发动机；燃烧特性；排放特性

Abstract: In this paper, the influence of the pre-injection timing on the combustion and emission characteristics of diesel engines is studied, and the relevant bench tests are carried out by adjusting the pre-injection timing of a high-pressure common rail in-line four-cylinder diesel engine. The influence of the pre-injection time on the combustion characteristics such as the pressure rise rate, the instantaneous heat release rate, the effective pressure cycle variation coefficient, the cylinder temperature, etc., as well as the emission characteristics such as the specific emission of the number of ultrafine particles and large particles, and the specific emission of NOx. The test results show that as the main pre-injection interval increases, the peak pressure rise rate decreases, the instantaneous heat release rate peaks earlier, the ultrafine particle concentration decreases, the brake specific particle number and the brake specific nitrogen oxides continues to decrease. Therefore, the combustion performance of the engine can be improved and the emission of pollutants can be reduced by adjusting the pre-injection time without changing the overall structure of the diesel engine.

Key words: Pre-injection timing; Diesel engines; Combustion characteristics; Emissions characteristics