A study of urea injection timing to predict the NOx conversion in SCR systems

Abstract

The automotive industry has been restricted by several regulations to reduce pollutant from diesel engines. To fulfill the emission regulation, advanced engine technology purposes to control pollutant reduction and lowering the unburnt HC, CO2 and CO level. However, it is difficult to meet the NOx limits of the world standard like a European standard (EURO VI) and American standard (US TIER 2 BIN 5). Selective catalytic reduction (SCR) with ammonia (NH3) has been successfully to remove NOx from diesel engines. However, uniform ammonia distribution is usually difficult to achieve. Therefore, a study on the effects of urea injection timing to predict NOx reduction efficiency is needed. In this study, the simulations and experimental work to obtain constant and stable conditions in the SCR system were conducted. Because the constant condition can optimize the ammonia uniformity. The engine in experiment was compute from engine turned on to find the desired temperature and airflow, and the simulation was performed using a commercial code of STAR-CCM+. The numerical results were validated using experimental results of ammonia concentration distribution.