LES and experimental investigation of flow field in the cyclone separator at different temperatures

Abstract

The present study is aimed to investigate the effect of temperature on the flow field. In this study, LES (large eddy simulation) and HWA (hot wire anemometry) are used to investigate the time-averaged and instantaneous flow field in the cyclone at different temperatures. The numerical results agree well with the experiment data. The results show that temperature has an impact on both the time-averaged flow field and the fluctuations of the flow field. To investigate the effect of temperature on flow field fluctuations, we first reveal the mechanism of flow field fluctuations. The effect of temperature on vortex motion and tangential velocity fluctuation is analyzed, and a mathematical model for predicting the freqeuncy of vortex core precession at different temperatures is proposed, fT/f0=k(T0/T)0.125(1+m). The Q criterion is used to identify the vortex in the cyclone. When the temperature is high, the vortex core undergoes a typical vortex breakdown phenomenon at the lower part of the cyclone separator: the vortex core breaks up into a double helix shape. This is the reason for the disappearance of the negative pressure region, the decrease in tangential velocity and the weak fluctuation of tangential velocity in the dipleg at high temperature.