Investigation of the Gas‐Jet Wiping Process − Two‐Phase Large Eddy Simulations Elucidate Impingement Dynamics and Wave Formation on Zinc Coatings. Issue 9 (24th May 2017)

• Record Type: Journal Article
• Authors: Pfeiler, Claudia; Eßl, Werner; Reiss, Georg; Riener, Christian K.; Angeli, Gerhard; Kharicha, Abdellah
• Is Part Of: Steel research international. Volume 88:Issue 9(2017)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2017-05-24
• Subjects: air knifes -- continuous hot‐dip galvanizing -- corrosion -- flat nozzles -- steel sheets; Steel -- Periodicals; Steel -- Metallurgy -- Periodicals; 669.142
• DOI: 10.1002/srin.201600507
• Languages: English
• ISSNs: 1611-3683

Abstract

Abstract : In addition to corrosion resistance and processing properties, high coating uniformity is a key quality criterion for galvanized steel sheets. Hydrodynamic gas jet wiping has proved to be an efficient method to control the coating thickness. However, the occurrence of non‐uniformities is attributed to the unsteadiness of the impinging jet. For the first time, vertical surface non‐uniformities resulting from the interaction of the impinging jet with the liquid coating are numerically predicted under industrial boundary conditions using the ANSYS Fluent ® . The turbulent flow field of the compressible wiping gas is accomplished by the LES (Large‐Eddy‐Simulation) turbulence model, whereas the interphase between the wiping gas and the liquid coating is modeled by the VOF (Volume‐of‐Fluid) method. It is found that the liquid coating reacts relatively slowly to the high frequent flapping gas jet. Only, when the jet is deflected for a comparatively long period, significant waves are able to develop. The waviness predicted by the simulation model is in good agreement with experimental results. Thus, the model enables a careful study of process settings on the vertical coating uniformity characteristics. For the studied case, an increase of nozzle inclination is found to enhance the performance in terms of coating uniformity significantly. Abstract : Turbulent gaseous jet induces waves on the liquid zinc coating of galvanized steel sheets – smooth coatings are a key quality criterion. The numerical results give insight to the jet‐coating interaction and the coating waviness. The results are compared to measurements at voestalpine galvanizing line. The model allows for the careful adjustment of nozzle‐parameters, as well as nozzle‐design improvements.