Impact of Post-Injection Parameters on Soot and Hydrocarbon Emissions in a Common-Rail Heavy-Duty Diesel Engine 2020-01-0374

In this paper, based on a direct injection (DI) diesel engine, soot and exhaust gaseous emissions were measured by a smoke meter and multi-component gas analyzer based on Fourier Transform Infrared (FTIR) spectroscopy under post-injection condition. The post-injection timing changed from 20 crank angle degree (CAD) after top dead center (ATDC) to 120 CAD ATDC, and the post-injection mass was set to either 5mg, 10mg or 15mg, to find a suitable post-injection strategy in a wide assessment range based on diesel oxidation catalyst (DOC) coupled diesel particle filter (DPF) after-treatment technology demands, considering emission reduction and after-treatment gas atmosphere investigation. The results showed that post-injection could achieve NO_x emission reduction, up to 14%. Besides, post-injection led to worsening soot emissions, and more hydrocarbon (HC) emissions were detected compared to the condition without the post-injection. With the post-injection, a higher concentration of unsaturated HC emissions (such as C₂H₂, C₂H₄, and C₃H₆), formaldehyde (HCHO), and acetaldehyde (CH₃CHO) appeared at late post-injection (after 70°CA). In the measured species, at 80°CA post-injection timing and with 10mg post-injection mass, species with low emissions (<30ppm), included CH₄, C₂H₂, C₃H₆, and CH₃CHO; species with medium emissions (>30ppm and <100ppm), included NO₂, HCHO, C₂H₄, and NC₈; species with large emissions (>100ppm), included NO, NO_x and non-methane hydrocarbon (NMHC). Furthermore, the peak position of NMHC was the same as C₃~C₈ HCs and different from C₂ HCs within the scope of the experiment, which indicated that, in terms of concentration, the proportion of C₂ HCs was not dominant in total NMHC emissions.