Experimental study of the dynamic characteristics of a cyclone by hot wire/film anemometry: Effects of gas leakage

Abstract Experimental investigation on the dynamic characteristics of vortex flow in a cyclone was performed, particularly focused on the effects of the gas leakage from the dipleg. The instantaneous tangential velocities were measured by hot wire/film anemometry (HWFA) under the conditions of different gas leakage velocities, and then analyzed in the time and frequency-domains. The results showed that, on one hand, gas leakage reduced the time-averaged tangential velocity, on the other hand, gas leakage made the instantaneous tangential velocity fluctuate more intensely, particularly in the lower region of the cyclone, while both could deteriorate separation efficiency. In addition, when the gas leakage velocity exceeded a certain value, the vortex tail swung heavily and re-entrained separated particles to escape through the exit tube, which might have further deteriorated the separation efficiency. Frequency-domain analysis revealed that there were two dominant frequencies in the cylindrical space. The high frequency (∼131 Hz) was produced by the rotation of the quasi-forced vortex, while the low frequency (∼35 Hz) was related to the swing of the vortex core. The amplitudes of the two dominant frequencies were clearly attenuated along the radial direction. With gas leakage velocity increasing to higher values, high frequency amplitudes were weakened, while the low frequency amplitudes were enhanced. This study revealed some mechanisms of the effects of gas leakage on the time-averaged and dynamic flow field in the cyclone.