van Vuuren, N. and Qin, J., "High Speed Video Measurements with Water of a Planar Laser Illuminated Heated Tip Urea Injector Spray," SAE Technical Paper 2013-01-1073, 2013, doi:10.4271/2013-01-1073.
The recent implementation of new rounds of stringent nitrogen oxides (NOx) emissions reduction legislation in Europe and North America is driving the introduction of new exhaust aftertreatment systems, including those that treat NOx under the high-oxygen conditions typical of lean-burn engines.One increasingly common solution, referred to as Selective Catalytic Reduction (SCR), comprises a catalyst that facilitates the reactions of ammonia (NH₃) with the exhaust nitrogen oxides (NOx) to produce nitrogen (N₂) and water (H₂O). It is customary with these systems to use a liquid aqueous urea solution, typically at a 32% concentration of urea (CO(NH₂)₂). The solution is referred to as AUS-32, and is also known under its commercial name of AdBlue® in Europe, and DEF - Diesel Exhaust Fluid - in the USA. The urea solution is injected into the exhaust and transformed to NH₃ by various mechanisms for the SCR reactions.Current production AUS-32 injection systems typically rely on technologies previously developed for gasoline port fuel injection systems. Spray data (patternator data, particle size measurements, etc.) for these injectors are typically obtained under standard room temperature conditions.Recently, results were presented from high-speed video imaging of an AUS-32 injector spray simulating the hot conditions at the injector spray exit for an exhaust injection application. Those results showed substantial structural differences in the spray between room temperature conditions, and conditions where the fluid temperature approached and exceeded 100°C.The results presented in this paper follow up on the previous imaging work with an examination of the heated spray footprint and side view using planar laser illumination (the results presented here were measured using water as a substitute for AUS-32). The spray structure change observed in the previously published measurements is confirmed, and some preliminary quantification of the change in the spray footprint is shown. An initial approach at evaluating the sensitivity of spray-gas mixing models to the observed spray structure changes is also discussed.