Characterization of a New Air Knife Design for the McMaster University Galvanizing Simulator

In this study, a new air knife geometry has been designed and fabricated in order to improve the air flow field between the exit of the jet and the substrate with the overall objectives of enhancing the current coating control capabilities of the McMaster University Galvanizing Simulator (MGS). The pressure distributions were measured as a function of plate-to-nozzle ratio at different flow rates. The measured pressure profiles for all plate-to-nozzle ratios were compared with the current air knife pressure profiles at Q=12.4 m³/h. The results showed that the maximum pressure of the new air knifes is higher than the maximum pressure of the current air knives and that the velocity profile across the air knife gap was significantly more uniform versus the current air knives. It was also determined that the impingement plate is slightly outside of the potential core for z/d=6 for all flow rates, likely as a result of the turbulent boundary layer for the jet flow comprising a significant portion of the 0.5 mm jet gap employed. Overall, the revised design for the MGS wiping knives should significantly improve the coating weight control for this apparatus.