Date of Award
6-26-2026
Date Published
July 2026
Degree Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Mechanical and Aerospace Engineering
Advisor(s)
Benjamin Kumgeh
Subject Categories
Engineering | Mechanical Engineering
Abstract
This thesis investigates the impact of heated Diesel Exhaust Fluid (DEF) injection on spray character- istics for selective catalytic reduction (SCR) applications using both experimental and computational methods. This work aims to understand how DEF spray properties vary with injection temperature and how these variations influence atomization, mixing, evaporation, spray–wall interaction, and thermally driven decomposition processes relevant to diesel engine aftertreatment systems. Key areas of focus include spray penetration, spray angle, breakup behavior, evaporation characteristics, and deposit-related tendencies under heated injection conditions. This research is motivated by the need to improve the effectiveness of SCR systems, particularly during engine startup and low-temperature operation, where NOx reduction performance is typically diminished. By characterizing cold and heated DEF sprays using Schlieren imaging, this work interogates the relation between injection conditions and spray performance. In addition, comple- mentary evaporation studies using a heating plate and a metal cup are carried out to assess the role of temperature in DEF vaporization and droplet behavior, while CFD simulations are used to complement the experimental results and examine spray development, impingement behavior, and injection under exhaust crossflow conditions. The results show that when heated DEF remains in the liquid phase, its free-spray structure is generally similar to that of cold DEF, with comparable spray angle and penetration. However, when flash boiling occurs, the heated spray exhibits faster development and a wider cone angle. The CFD simulations reproduce the main experimental spray features and capture the measured spray tip penetration trends with good agreement. In spray impingement studies, heated DEF produces finer droplets, broader wall dispersion, and reduced rebound compared with cold DEF. Evaporation tests further show that the DEF evaporation rate increases with temperature, while single-droplet experiments indicate that higher surface temperatures promote breakup, faster removal of liquid material, and changes in residue persistence. Under a 200◦C exhaust crossflow condition, DEF preheating leads to only minor changes in droplet-size distribution and outlet NH3 distribution, with a slight increase in NH3 level in the heated case. The more rapid evaporation and decomposition of finer droplets highlighting the need for injection solutions that promote atomization such as higher pressure. Overall, the findings provide a more physically grounded understanding of heated DEF spray behavior and help identify the conditions under which preheating alters atomization, wall interaction, evaporation, and ammonia formation in SCR-relevant environments. It points to the potential positive impact of higher injection pressure that yields finer droplets that be easily vaporized and decomposed in exhaust crossflow. It also points to the potential benefit of incorporated heated surfaces in the aftertreatment system to promote decomposition of cold start up.
Access
Open Access
Recommended Citation
Liu, Zeyang, "Investigation of Reactive and Non-reactive Diesel Exhaust Fluid Spray Characteristics" (2026). Dissertations - ALL. 2332.
https://surface.syr.edu/etd/2332
