 |
Stringent emission regulations proposed for heavy duty diesel engines demands an efficient after-treatment system for internal combustion engines to control the NOx and soot emissions. Urea-based selective catalytic reduction (SCR) system is widely used to reduce NOx emission from diesel engines. The NOx conversion efficiency, as well as the adverse effects of wall-wetting is mainly influenced by the atomization characteristics of urea water solution (UWS). Under extreme winter conditions, the UWS can reach temperatures as close as its freezing temperatures. Under these adverse weather conditions the flow and spray characteristics of UWS are not well defined. In order to gain an understanding of these factors, an attempt has been made in this work to study the effect of varying the temperatures of UWS to evaluate the spray characteristics of UWS used in SCR systems. In this work, the temperature of UWS were varied from 20°C to -10°C to consider the variations in the ambient temperatures from normal up to freezing point of UWS. High-speed shadowgraph method was used to evaluate the spray characteristics, further analysis were performed to evaluate the spray drop-size distribution, global and near-nozzle spray structure. In addition to this, the impact of physical property variations of UWS under different temperatures as well as the pressure variations of the air-assisted SCR injection system on the spray characteristics will be presented in the full paper.
