Urea-SCR 분사시스템의 DeNOx 저감 성능 향상과 NH3슬립저감을 위한 모델 기반 제어알고리즘 개발 및 구현

Abstract

The selective catalytic reduction (SCR) system is a highly-effective aftertreatment device for NOx reduction of diesel engines. Generally, the ammonia (<TEX>$NH_3$</TEX>) was generated from reaction mechanism of SCR in the SCR system using the liquid urea as the reluctant. Therefore, the precise urea dosing control is a very important key for NOx and <TEX>$NH_3$</TEX> slip reduction in the SCR system. This paper investigated NOx and <TEX>$NH_3$</TEX> emission characteristics of urea-SCR dosing system based on model-based control algorithm in order to reduce NOx. In the map-based control algorithm, target amount of urea solution was determined by mass flow rate of exhaust gas obtained from engine rpm, torque and <TEX>$O_2$</TEX> for feed-back control NOx concentration should be measured by NOx sensor. Moreover, this algorithm can not estimate <TEX>$NH_3$</TEX> absorbed on the catalyst. Hence, the urea injection can be too rich or too lean. In this study, the model-based control algorithm was developed and evaluated on the numerical model describing physical and chemical phenomena in SCR system. One channel thermo-fluid model coupled with finely tuned chemical reaction model was applied to this control algorithm. The vehicle test was carried out by using map-based and model-based control algorithms in the NEDC mode in order to evaluate the performance of the model based control algorithm.