Uniflow cyclones have gas and particles passing through them in only one direction and are preferably used for applications with space limitations. Recently comprehensive information has been gained on the design criteria of uniflow cyclones by systematic experiments.
Analysis on experimental studies of uniflow cyclones with an inner diameter of 100 mm showed main influences to the separation performance of this separator type.
The expected influence of the vortex finder diameter is the result of two main effects. The behavior of the radial velocity component at the inlet zone of the vortex finder is reciprocal. An increased vortex finder diameter results in a lower radial velocity. This velocity component could prevent particles to be separated into the particle outlet, see Figure 1 (left). The second effect is a result of a secondary flow witch is winding around the outer vortex finder tube in reverse direction of the main flow through the separator. At smaller vortex finder diameters this component increases and may transport already separated particles out of the particle outlet chamber into the vortex finder tube, see Figure 1 (right).
Figure 1: Influences of the vortex finder tube to the separation performance of uniflow cyclones
Current studies on uniflow cyclones are carried out in order to identify a critical particle zone of radial particle movement in downstream direction in the separation chamber, see Figure 2. Due to non-invasive measurement methods including laser illuminated particles the flow pattern through the separator is unaffected. The evaluation is realized with optical methods identifying partial particle accumulation due to obscuration effects.
Figure 2: Particle sedimentation zone
 Kraxner M. “Empirische Ermittlung von Auslegungskriterien für Gleichstromzyklone in Multizyklonblöcken” PhD-thesis (2013)