Spray Characterization and CFD Simulation Workflow Analysis of Industrial Air-assist Nozzles in the Field of SCR Application

Controlling exhaust pollution by selective catalytic reduction (SCR) requires the precise and efficient injection of reductant, which highlights the crucial role played by nozzles. Their characteristics, such as droplet size distribution, penetration depths, and spray angle, significantly impact the overall functionality of this application. This work provides insights into an external atomizing air-assist nozzle, which is commonly utilized in SCR applications. A set of 10 nozzles of the same type were analyzed via shadowgraphy, structural image Velocimetry (SIV), and Phase-Doppler-Anemometry (PDA) methods to ascertain their spray characteristics and behavior. Based on the averaged experimental data, inlet boundary conditions for computational fluid dynamics (CFD) simulations are derived. The spray properties simulated following two different workflows, such as droplet size and droplet velocity distribution, are evaluated on two planes in the spray direction using experimental data. It is demonstrated that common spray models can achieve an acceptable degree of accuracy across a broad range of operation points. The limitations are identified and a sensitivity analysis on the workflow demonstrates the significant dependency on physical models as well as numerical settings.