Optimizing SCR System Design to Enhance NOx Reduction and Minimize Accretion through Swirl Mixing Integration

Introduction: This study presents an investigation into the optimization of a Selective Catalytic Reduction unit in an Aftertreatment system, focusing on minimizing the harmful gas, particularly oxides of nitrogen, in diesel engines. Methods: Two models were evaluated: a base model and a proposed model, both simulated using Computational Fluid Dynamics (CFD), where a swirl mixer was incorporated in the proposed model. Results: The base model experienced a pressure drop of 95.28 Pa, while the proposed model with the swirl mixer showed a slightly higher pressure drop of 123.67 Pa. The urea deposit thickness of the proposed SCR model was reduced to 5.1 × 10-4 microns. The base SCR model exhibited an Accretion Rate (AR) of 1.66×10-4 kg/m²s, which posed challenges such as catalyst blockages and reduced performance. In contrast, the proposed SCR model with no mixer achieved a significant reduction in AR to 8.5×10-5 kg/m²s, marking a 48.8% drop. Discussion: The proposed model demonstrated an efficient decreasing in accretion rate and better NOx reduction performance. To further enhance the proposed model, a swirl mixer was introduced, resulting in improved ammonia (NH3) distribution and increased NOx conversion efficiency. Conclusion: The swirl mixer significantly reduced Urea Deposition Thickness (UDT) 4.7×10-4 microns and Accretion Rate (AR) 8.2×10-5 kg/m²s, highlighting its efficient system for industrial applications by achieving a 94.87% reduction in accretion compared to the base model and an 84.2% reduction compared to the proposed model without the mixer at 41.9 mg/s. This study's findings can be deemed a patent for laying forth major implications for industrial SCR systems.