Effects of Diesel Exhaust Fluid (DEF) Injection Configurations on Deposit Formation in the SCR System of a Diesel Engine

摘要

In the Selective Catalytic Reduction (SCR) exhaust treatment system, the Diesel Exhaust Fluid (DEF) or urea water solution is injected in the form of spray into exhaust gas for mitigating the NOx emissions. One of the challenges adversely affecting its functionality is incomplete thermolysis of the injected urea upstream of catalyst. This leads to the formation of undesirable deposits, which blocks the exhaust system leading to back pressure rise, loss in NOx reduction efficiency and durability issues. The current study attempts to evaluate the influence of several DEF injection configurations on the deposit formation risk in an airless Urea-SCR exhaust system of Diesel engine used for commercial vehicle applications. Combination of experimental methods involving vehicular trials and detailed CFD simulation for modeling wall film were used. Further, the influence of the urea injection angle, injection cone geometry and mixing length on deposit formation risk was investigated. Finally, the deposit formation behavior of the optimized urea injection configuration under the vehicle durability was assessed.