Fundamentals of Close Coupled Atomization for Battery Metal Powders
Close coupled atomization controls melt superheat, aspiration pressure, and supersonic gas shear to yield ultrafine spherical powders for battery manufacturing.
Shock Wave Mach Disk
Meaning
Supersonic flow structures in atomization jets contain high-pressure transitions that affect gas velocity. A critical feature of these structures is the shock wave mach disk, which is a flat normal shock that forms in the center of the jet. This disk acts as a barrier that slows the supersonic gas to subsonic speeds, causing a sudden loss of kinetic energy.
Metal droplets must interact with the gas before this barrier to undergo efficient breakup.
Jet Expansion
High-pressure gas exiting the nozzle expands rapidly into the lower-pressure atomization chamber. This expansion forms a pattern of diamond-shaped shock waves that reflect off the jet boundaries. If the nozzle operates far from its design pressure, the Mach disk grows larger, blocking more of the high-velocity gas.
Droplet Breakup
Efficient secondary fragmentation relies on the high velocity of the gas to shear the metal droplets. The subsonic region behind the disk reduces the drag forces acting on the liquid metal. This reduction results in a higher proportion of coarse, irregular particles in the final batch.
Operational Limits
Gas pressure must be carefully matched to the nozzle geometry to minimize the size of the Mach disk. Standard production runs use pressure regulators to keep the jet within its optimal operating window.