12th International Conference on Zinc & Zinc Alloy Coated Steel Sheet - GALVATECH 2021

In the present study Computational Fluid Dynamics (CFD) were used to design a new air-knife for the hot-dip galvanizing simulator of Salzgitter Mannesmann Forschung in order to improve the flow field inside the knife and at the nozzle exit. The overall objectives were to improve the surface quality of coated samples and enhance coating control capabilities compared to the existing air-knife by optimising the gas flow inside the knifes. The existing configuration yields coating thicknesses from 7 µm on, although coating homogeneity could be optimised. The flow field inside the nozzle was modelled by transient RANS simulation. An ideal air-knife should create a uniform gas flow with low turbulence at the nozzle exit. However, this is difficult to achieve, being affected by various factors. It could be shown that the existing air-knife bears some significant fluidic disadvantages at the gas inlet and distribution inside the nozzle, causing an inhomogeneous, unsteady flow. A new air-knife design with optimised inlet and an innovative shape for rectified fluid deflection and distribution was designed. The additional application of a turbulence manipulator and an improved feeding geometry of the exit channel finally lead to a much more uniform gas flow. The turbulence of the flow is reduced significantly by the new design, compared to the existing nozzle.