Euro 7 Light Duty SCR System Solution with Software-Extraction of the Ammonia-Signal from NO_x-Sensors

Two-stage SCR systems with double dosing are now state of the art for passenger cars and light commercial vehicles and thus the starting point for meeting future Euro7 requirements. Even lower emission limits, the regulation of further exhaust gas components such as NH₃ and N₂O, the extension of the RDE boundary conditions and On Board Monitoring will be core requirements for the SCR system. Therefore, hardware and software of the SCR system will have to be further developed or newly developed accordingly. For the AdBlue dosing system, this results in new requirements for monitoring capability, dosing quantity accuracy and fast system readiness, which have been implemented with the new Denox5.3 generation. The central Euro 7 requirements for the NO_x sensor are a fast signal readiness from engine start as well as an even further increased accuracy, which have been incorporated into the development of the new sensor generation EGS-NX3. In order to achieve robustly high efficiencies, closed-loop control is required that takes into account the system architecture of the two-stage SCR system. For this purpose, it is important to know the NH₃ levels in both catalysts as precisely as possible. However, the NO_x sensor at the position between the catalysts can only measure the sum of NO_x and NH₃. With sophisticated software procedures, it is nevertheless possible to infer the respective NO_x or NH₃ signal components and thus increase system performance without additional sensor costs.