Efficient Modeling of SCR Urea Deposits Formation Using ANSYS Fluent

This paper presents recent developments of the Euler/Lagrange wall film model which allow the efficient simulation of complete Selective Catalytic Reduction (SCR) systems, used for exhaust gas aftertreatment in diesel and newly designed H₂ engines. Since release 2024R2, ANSYS Fluent is equipped with a chemistry model from recent literature to predict homogeneous chemical reactions in the film and heterogeneous reactions between gas and film occurring in SCR systems operating with aqueous urea solutions. The implementation of the chemistry model is first validated against results from Thermo–Gravimetric Analysis (TGA) measurements. The SCR–specific chemistry, combined with the Lagrangian Wall Film (LWF) model employing an improved wall–film convective heat transfer model, is then compared favorably with experimental SCR test rig measurements of urea deposits for fifty injection cycles, followed by a relaxation period. The full simulation completes significantly faster due to a new numerical algorithm for the LWF which reduces the number of wall film particles by consolidating groups of particles into a single particle that produces the same overall effect.