A centrifugal atomizer was designed and built for this study.
A schematic of the experimental apparatus is shown in Fig. 2. A
Thermocraft electric furnace was used to melt the aluminum.
The aluminum was held in a carbon-bonded silicon carbide
crucible. To develop a steady flow a 1-mm hole was drilled into
the bottom of the crucible. Initial experiments showed that if
this hole was not plugged, it would leak before all the aluminum
was melted. Pressurizing the crucible with 20 psi of argon
developed a steady flow.
Argon was supplied to the crucible through a pipe that also
contained a plain carbon steel rod that plugged the hole in the
bottom of the crucible during melting to prevent leakage. It was
found that plain carbon steel was more corrosion resistant against
the molten aluminum than the stainless steel used during early
experiments. The steel rod and pipe extended outside of the
furnace. A seal was formed around the steel rod with an O-ring.
The O-ring was kept cool with a coil of copper tubing with water
flowing through it. Fig. 3 shows drawings of the crucible
pressurization system. A Cambell Hausheld pneumatic diegrinder,
model number TL1020, was chosen as a motor for the
rotating disk. Calibration of the motor was performed using a
high-speed video camera. Because the crucible could not always
be positioned in the exact same position, a holder for the pneumatic
motor was designed to move horizontally to align the
aluminum stream with the disk. This was accomplished by using
an x–y-positioning table. Rods with universal joints attached to
them were connected to the table. Dials for operators to rotate and
adjust the disk were located outside the atomization chamber.
Plain carbon steel rotating disks 3 inch in diameter and
0.1 inch thick were used. The disks had a quarter of inch spindle