While Iinoya et al. [4] found that it is possible to classify powders
even in the 0.4 μm size range using special cyclones, it is generally
difficult to change the cut size in a conventional cyclone separator. To
solve this problem, Yoshida et al. [1,5] found that it is possible to change
the cut size by the use of a moving circular guide plate at the cyclone
inlet or by the use of an additional secondary flow injection method in
the upper cylindrical part of the cyclone. By use of a special apex cone at
the inlet part of the dust box and by using the blow-up method, it is
reported that the cut size can be easily controlled from 1 μm to 40 μm
size range [6]. In order to increase particle separation performance of a
gas-cyclone, the effect of an apex cone used at the upper part of a dust
box was examined and it is confirmed that rotational and upward fluid
velocity components decreased with the apex cone set at the dust
box [7]. However, the optimum shape of the apex cone in the gascyclone
was not clear