Abstract:

The processing vortex core phenomenon (PVC) diminished the efficiency of a cyclone in capturing fine particles. In this paper, the numerical simulation method was used to study the motion frequency of vortex core and eccentricity degree from vortex core to geometrical center in a gas-flow field with a spiral inlet. Generally, the surface minimum pressure was regarded as the vortex core, and the PVC phenomenon was swung most heavily at the dust outlet section. Therefore, the variation of minimum pressure over time at dust outlet was analyzed by the fast Fourier transform (FFT), and the location of the vortex core was recorded. The results showed that the frequency and eccentricity degree at the dust outlet were gradually decreased with the increase of volute wrapping angle, and the PVC phenomenon was weakened. While the volute wrapping angle was more than 270°, the PVC phenomenon in the gas-flow field almost disappeared. The influence of the entrance cut-off on the movement characteristics of the vortex core at the dust outlet section would vary depending on the volute wrapping angle. Compared with the symmetry of the inlet structure, the eccentricity degree of vortex core was more strongly related to the energy loss of the down draft. When the energy loss of the downward airflow was greater, the energy getting from outer vortex to inner vortex zones was higher, and upward flow would suffer greater horizontal disturbances. When the energy of the incoming air flow exceeded a certain threshold value, the vortex core oscillation was induced. The vortex core rotation frequency was less affected by the energy loss of the downward airflow.

Key words: cyclone separator, processing vortex core, inlet structure, eccentricity degree, frequency

摘要：

旋进涡核（PVC）现象会削弱旋风分离器对细颗粒的捕集效率。利用数值模拟方法研究纯气相流场中涡核的运动频率和偏心程度。结果表明：随着蜗壳包角的增大，排尘口截面涡核的运动频率和偏心程度都逐渐减小，PVC现象被削弱，蜗壳包角大于270°以后，纯气相流场中的PVC现象基本消失。入口切进度对排尘口截面涡核运动特性的影响会因蜗壳包角而有所不同。相比于入口结构的对称性，涡核偏心程度与下行气流的能量损失相关性更强。下行气流的能量损失越多，下行期间汇入内旋流的气流能量越高，内旋上行气流受到的横向扰动越大，汇入气流的能量超过某一阈值后，引发涡核摆动。而涡核旋转频率受下行气流能量损失的影响则较小。

关键词: 旋风分离器, 旋进涡核, 入口结构, 偏心程度, 频率