In a selective catalytic reduction (SCR) system, urea atomization and mixing directly affect denitrification efficiency. Uniform NH 3 distribution improves NO x conversion, but excessive wall liquid film from spray impingement can lead to crystallization, endangering stable operation and potentially blocking the exhaust pipe. This study examines how injection parameters influence SCR atomization and mixing. A computational fluid dynamics (CFD) model of the aftertreatment system is built, with key injection parameters derived from spray experiments; the pressure drop validation error is within 5%. The effects of spray cone angle, nozzle installation angle, and spray inclination angle on NH 3 generation and liquid film accumulation are analyzed. Quantitative results show that a 40° spray angle yields a 1.21% higher average NH 3 mole fraction at the catalyst inlet and 2.51% more residual liquid film than a 50° angle, with similar NH 3 uniformity. Injection parameters change urea droplet distribution, altering gas–droplet contact area and residence time, thus affecting atomization, mixing, and urea decomposition. They also influence droplet impingement on mixer components, determining liquid film buildup. A combination of a 50° spray angle, a 24° nozzle installation angle, and a 4.53° spray inclination angle is recommended for optimal performance. These results offer engineering guidance for compact mixers to reduce crystallization risk while preserving NO x conversion efficiency.
Y et al. (2026) studied this question.