Meaning
First stage of liquid stream disintegration during atomization where a continuous flow of liquid metal is disrupted into large ligaments, droplets, or sheets. The primary breakup regime is characterized by the growth of surface instabilities driven by aerodynamic and inertial forces. This initial breakdown occurs close to the exit of the liquid delivery tube before further fragmentation takes place.
Disintegration Stage
High-speed gas forces act on the liquid metal stream to initiate wave propagation across the liquid surface. These waves grow in amplitude until the liquid sheet or column stretches into unstable filaments. Capillary forces then cause these filaments to break apart into distinct droplets.
This primary phase determines the spatial distribution of the spray plume and the initial droplet size.
Fluid Interaction
Density and velocity ratios between the gas and liquid phases dictate the onset of this initial disruption. When the gas velocity is high relative to the liquid stream, the aerodynamic drag overcomes the surface tension of the metal. This interaction is characterized by different modes, such as bag breakup or shear-stripping, depending on the fluid properties.
High viscosity in the liquid metal suppresses wave growth, which requires more energy to initiate the breakup.
Control Parameter
Gas-to-melt mass flow ratios and nozzle exit pressures are adjusted to control this initial fragmentation step. Operating with a higher gas-to-melt ratio results in a more rapid transition to the primary breakup, which ensures smaller initial fragments. This behavior is analyzed using high-speed imaging to verify spray stability and optimize nozzle operation.
