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 NOx 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, NOx 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.