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This study experimentally investigated the ability of a novel multi-slot air-knife design to reduce high-intensity tonal noise and produce thinner coating weights in the continuous galvanizing gas jet wiping process. Coating weight measurements were carried out over a wide range of operating conditions to correlate the effect of the multi-slot jet operating parameters on the final coating thicknesses. These experiments showed that the resulting coating weight agreed with the predictions of the Elsaadawy et al. [1] analytical model and could produce thinner coatings versus the conventional single-slot geometry for the same main jet velocity with relatively low auxiliary jet velocities.
Further experiments showed that the novel multi-slot air-knife design reduced the tonal noise and jet oscillations of the aeroacoustics feedback mechanism exhibited by conventional single slot air-knifes, where the use of the auxiliary jets resulted in an average reduction in the acoustic tone intensity by 85%. Furthermore, the oscillation of the air-knife due to the large vortices of the aeroacoustics feedback mechanism was reduced by 45%, which resulted in a decrease in the fluctuating pressure at the substrate by 75%. The coating weight experiments also confirmed a correlation between suppressing the aeroacoustic feedback mechanism and lighter coating weights.
The findings of this work indicate that the multi-slot design can be a more effective wiping actuator in the continuous hot-dip galvanizing line, producing more consistent and lighter coating weights with less intense tonal noise when compared to the single jet design. This paper will discuss the results of these investigations in detail.