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Numerical Analysis of the Flow Rig for UWS Spray Examination in Exhaust System-relevant Conditions

Numerical and experimental studies on urea-water solution (UWS) injections play a crucial role in the development process of exhaust aftertreatment systems based on urea-selective catalytic reduction (SCR) technology. A proper spray representation in the numerical model is one of the key factors determining the accuracy of the exhaust system’s simulations. On the other hand, spray measurements to provide input data for simulations are usually done in low-temperature quiescent conditions, while a strong crossflow of hot exhaust gases may greatly affect the process of spray formation. In the present study, a flow rig with optical access intended for spray investigations in exhaust system-relevant conditions was analysed in terms of flow and temperature in the spray area using numerical simulations. The operation of the rig was examined for a wide range of exhaust mass flow rates, temperatures and various forms of UWS spray plumes. The locations of the injector and thermocouple were verified. Both conventional and flash-boiling injections were considered to assess the effect of the interaction of sprays with a gas flow. The results showed highly uniform flow in the visualisation area, with only minor fluctuations near the walls. A similar observation was carried out for the temperature distribution. It was found that the extreme operating conditions caused substantial deformations of the spray plumes. However, the selected injector location allowed us to observe the spray formation properly regardless of the flow conditions. The study showed that the examined test rig enabled reliable spray investigations for a wide range of operating points.
Topic: Exhaust emissions and aftertreatment
Author: Krzysztof Górka
Co-authors: Bartosz Kaźmierski Łukasz Jan Kapusta