The fight against pollution relies heavily on Selective Catalyst Reduction (SCR) systems, the gold standard for removing harmful NOx vehicle exhaust. SCRs work by injecting a Urea–Water Solution (UWS) into the exhaust stream, converting NOx into harmless nitrogen.
Why injector performance matters
The effectiveness of an SCR system is extremely sensitive to how the UWS is injected. This process is a complex multi-phase flow where liquid spray meets hot gas. Poor injection leads to problems like wall film formation and urea crystallization, hurting efficiency and system life.
Finding the sweet spot
A study titled “Multiphase injector modelling for automotive SCR systems…” used numerical analysis (CFD) to pinpoint the perfect injection settings. The research systematically tested the impact of three crucial parameters:
- Injection velocity
- Spray angle
- Droplet size
The simulation, using AVL Fire 2014 v, successfully modeled the turbulent flow and droplet interaction using an Euler/Lagrange approach.
The key takeaway
The analysis confirmed that these injection parameters significantly influence the Ammonia Uniformity Index (NHUI) and the amount of wall film formation. By modeling and predicting these results, the study created response surfaces—powerful tools that allow engineers to optimize SCR systems for better efficiency and cleaner air, even outside of tested settings.
This article was written based on the research articles presented by active and former Katcon Global members.
Azael Capetillo, Fernando Ibarra, Multiphase injector modelling for automotive SCR systems: A full factorial design of experiment and optimization, Computers & Mathematics with Applications, Volume 74, Issue 1, 2017, Pages 188-200, ISSN 0898-1221, https://doi.org/10.1016/j.camwa.2017.01.025