Optimization of selective catalytic reduction for nox emission control: an experimental and CFD analysis of mixer designs

This study focuses on optimizing the selective catalytic reduction (SCR) system to reduce urea deposits and enhance overall system performance. Both computational fluid dynamics (CFD) simulations and experimental analyses were conducted to evaluate an S-bend inlet SCR design and an improved configuration featuring multiple mixer setups. The enhanced design demonstrated superior performance, with the flap mixer reducing the accretion rate to 3.6 × 10⁻⁴ kg/m²s, representing a 60.9% reduction in urea deposition at an injection rate of 41.9 mg/s under acceleration conditions, compared to the no-mixer SCR setup. Furthermore, the thickness of the urea deposit was substantially reduced, with experimental measurements showing a decrease from 5.6 × 10⁻⁴ microns (no-mixer SCR setup) to 2.6 × 10⁻³ microns (flap mixer), marking a 53.6% reduction. The experimental and CFD results exhibited strong agreement, with deviations of 8% for the accretion rate and 7-9% for urea deposit thickness, reinforcing the reliability of the simulation model. The close alignment between experimental and numerical findings highlights the effectiveness of the optimized mixer in promoting uniform droplet breakup and reducing localized deposition. The implementation of optimized mixer geometries improved overall system performance, facilitated compliance with stringent emission regulations, and mitigated operational complexities related to urea accumulation. This study supports the ability of current SCR systems to meet future NOx emission limitations at reduced cost.