9 Impact Comminution in Jet Mills
315
Fig. 4 Low-pressure particle impact device
the finite element calculations. Therefore, aluminium spheres with an initial diameter of 6 mm (Umarex, Germany) were accelerated towards a rectangular steel plate
(150 mm × 150 mm × 20 mm, length × width × height) using pressurized air. Before
impact, the velocity of the particles was measured by two light barriers installed in
close distance to the impact plate. The size of the formed spherical contact area
(minimum Feret diameter) on the surface of the particles was related to the particle
size ratio x c /x. By using a scale paper placed in the plain of the contact, the minimum Feret diameter of the contact area was determined from photographic images.
Therefore, the waist diameter equals the initial particle diameter. No changes in the
waist diameter were detected within the evaluated impact velocity range.
315
Fig. 4 Low-pressure particle impact device
the finite element calculations. Therefore, aluminium spheres with an initial diameter of 6 mm (Umarex, Germany) were accelerated towards a rectangular steel plate
(150 mm × 150 mm × 20 mm, length × width × height) using pressurized air. Before
impact, the velocity of the particles was measured by two light barriers installed in
close distance to the impact plate. The size of the formed spherical contact area
(minimum Feret diameter) on the surface of the particles was related to the particle
size ratio x c /x. By using a scale paper placed in the plain of the contact, the minimum Feret diameter of the contact area was determined from photographic images.
Therefore, the waist diameter equals the initial particle diameter. No changes in the
waist diameter were detected within the evaluated impact velocity range.