Development of a Compact Urea-SCR+CRT™ System for Heavy-Duty Diesel using a Design of Experiments Approach

Achieving optimal performance in a mobile SCR+CRT™ (Selective Catalytic Reduction + Continuously Regenerating Trap) system is a complex task relative to other passive emissions control systems, due to the operating constraints of urea-SCR technology, the size of the system components and the tight packaging envelope on the vehicle. These constraints have necessitated the design of highly efficient, compact reductant-exhaust gas mixing arrangements in order to achieve uniform reductant and velocity distributions at the entry to the SCR catalyst.

The paper describes a statistical Design of Experiments (DoE) approach to optimise the mixing arrangement for emissions and noise attenuation performance of an SCR+CRT™ system. The results from this approach show that the method is an effective tool for understanding complex systems and reducing development effort. The relative emissions performance of the system has been improved by between 2 and 26% across the operating temperature range, whilst achieving the target noise level.