关键词: cyclone separator;flow field;instantaneous velocity;precessing vortex core;particle image velocimetry

Abstract: The precessing vortex core (PVC) in a cyclone separator plays an important role in the
separation performance and in further understanding of the general law of periodic unsteady
flow therein. In this paper, theunsteady flow field is investigated with particle image
velocimetry (PIV), and the instantaneous velocity, vorticity,tangential velocity, and
radial velocity are acquired by analyzing the images of instantaneous flow. It is for the
first time reported that there is a centrifugal flow region close to the dust discharge
zone and its maximum value is higher than the mean radial velocity. This discovery is very
important for understanding the principle of separation of particles in the area of dust
discharge. Determination of the frequency and amplitude of PVC was conducted in the region
where the phenomenon of PVC is remarkable. Results agree well with those obtained by hot
wire anemometry. The observations of the center of vortex core and the bimodal distribution
of the amplitude of the PVC indicate the vortex core precesses around the geometric axis of
the cyclone in its own way.

Key words: cyclone separator, flow field, instantaneous velocity, precessing vortex core, particle image velocimetry